期刊文献+
共找到1,138篇文章
< 1 2 57 >
每页显示 20 50 100
Time trends in myopia and high myopia prevalence in young university adults in China 被引量:5
1
作者 Hong-Mei Zhang Bing-Qin Li +2 位作者 Yun Zhu Sheng-Xin Liu Rui-Hua Wei 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2023年第10期1676-1681,共6页
AIM:To investigate time trends in myopia and high myopia prevalence over 6y among young university adults in China.METHODS:This is a 6-year series cross-sectional study from 2016 to 2021.Totally 4910 freshmen were enr... AIM:To investigate time trends in myopia and high myopia prevalence over 6y among young university adults in China.METHODS:This is a 6-year series cross-sectional study from 2016 to 2021.Totally 4910 freshmen were enrolled and completed a questionnaire concerning age,gender,and disease history.Students with eye diseases were excluded after a detailed eye examination.The refractive status was measured by non-cycloplegic objective refraction and ocular parameters were measured by Lenstar 900.The examination followed the same protocol each year.Trends over time in myopia and high myopia prevalence,as well as ocular biometry parameters,were analyzed.RESULTS:From 2016 to 2021,the axial length(AL)and corneal radius(CR)increased significantly(P=0.002 for AL;P=0.04 for CR).However,the spherical equivalent(SE)and the ratio of axial length to the corneal radius(AL/CR)did not change significantly(P=0.59 for SE;P=0.24 for AL/CR).The frequency of AL≥26.0 mm increased from 26.6%in 2016 to 29.3%in 2021(P=0.05 for trend).The prevalence of myopia and high myopia did not change significantly in our study(P≥0.18).Compared to a similar cross-sectional study conducted 10 years ago,the prevalence of myopia decreased significantly(94.9%vs 91.8%,P<0.001).Whereas the prevalence of high myopia increased largely(18.12%vs 27.6%,P<0.001).CONCLUSION:The prevalence of high myopia increases in young university adults during 10y period.Myopia control should begin earlier in childhood.However,these interventions are still needed for high myopia even in young adulthood. 展开更多
关键词 MYOPIA high myopia PREVALENCE axial length time trend
原文传递
Increasing pancreatic cancer is not paralleled by pancreaticoduodenectomy volumes in Brazil:A time trend analysis
2
作者 Lucila M Perrotta de Souza Jessica PL Moreira +3 位作者 Homero S Fogaca José Marcus Raso Eulálio Ronir R Luiz Heitor SP de Souza 《Hepatobiliary & Pancreatic Diseases International》 SCIE CAS CSCD 2019年第1期79-86,共8页
Background: Currently, surgical resection represents the only curative treatment for pancreatic cancer(PC), however, the majority of tumors are no longer resectable by the time of diagnosis. The aim of this study was ... Background: Currently, surgical resection represents the only curative treatment for pancreatic cancer(PC), however, the majority of tumors are no longer resectable by the time of diagnosis. The aim of this study was to describe time trends and distribution of pancreaticoduodenectomies(PDs) performed for treating PC in Brazil in recent years. Methods: Data were retrospectively obtained from Brazilian Health Public System(namely DATASUS) regarding hospitalizations for PC and PD in Brazil from January 2008 to December 2015. PC and PD rates and their mortalities were estimated from DATASUS hospitalizations and analyzed for age, gender and demographic characteristics. Results: A total of 2364 PDs were retrieved. Albeit PC incidence more than doubled, the number of PDs increased only 37%. Most PDs were performed in men(52.2%) and patients between 50 and 69 years old(59.5%). Patients not surgically treated and those 70 years or older had the highest in-hospital mortality rates. The most developed regions(Southeast and South) as well as large metropolitan integrated municipalities registered 76.2% and 54.8% of the procedures, respectively. LMIM PD mortality fluctuated, ranging from 13.6% in 2008 to 11.8% in 2015. Conclusions: This study suggests a trend towards regionalization and volume-outcome relationships for PD due to PC, as large metropolitan integrated municipalities registered most of the PDs and more stable mortality rates. The substantial differences between PD and PC increasing rates reveals a limiting step on the health system resoluteness. Reduction in the number of hospital beds and late access to hospitalization, despite improvement in diagnostic methods, could at least in part explain these findings. 展开更多
关键词 Pancreatic cancer PANCREATICODUODENECTOMY time trend analysis Ecological study Hospitalization rates Mortality rates
暂未订购
Time trends in dietary Zn intake and occurrence of dietary Zn inadequacy among Chinese adults:data from the China Health and Nutrition Surveys between 2004 and 2011
3
作者 Lu LIU Alida MELSE-BOONSTRA +4 位作者 Wen-Feng CONG Mo LI Fusuo ZHANG Wopke VAN DER WERF Tjeerd JAN STOMPH 《Frontiers of Agricultural Science and Engineering》 2025年第3期559-570,共12页
Adequate dietary zinc intake remains a public health challenge in China.Also,there is a lack of information on the relationship between Zn intake and food consumption patterns across provinces and over time.In this st... Adequate dietary zinc intake remains a public health challenge in China.Also,there is a lack of information on the relationship between Zn intake and food consumption patterns across provinces and over time.In this study,data from the China Health and Nutrition Survey 2004-2011(21,266 individuals)was used to explore associations between dietary Zn intake and sociodemographic factors.Zn intake per person declined from 11.1 mg·d^(-1)in 2004 to 9.89 mg·d^(-1)in 2011,with reduction in cereal consumption the greatest contributor to this.However,the reduction resulting from the lower cereal consumption was only partly compensated by an increase in consumption of Zn-rich foods.The percentage of the study population with inadequate Zn intake increased from 23% in 2004 to 37% in 2011.While Zn intake was positively associated with income levels in each survey year,the time trend for all income levels was a gradually reducing Zn intake.In all years,males had an average higher dietary Zn intake,whereas no significant difference was found between living areas.In conclusion,this study shows that dietary Zn inadequacy was high and has increased over the studied period.Remediation could be sought by shifting dietary patterns toward more Zn-dense food or by enhancing Zn concentration through biofortification. 展开更多
关键词 CEREALS food consumption pattern sociodemographic characteristics time trend zinc intake inadequacy
原文传递
Changing trends in upper gastrointestinal endoscopic findings in Ethiopia:A comparison of eighteen thousand exams across two periods
4
作者 Guda M Roro Rodas T Annose Odd H Gilja 《World Journal of Gastrointestinal Endoscopy》 2025年第5期41-50,共10页
BACKGROUND Relative changes in the prevalence of gastrointestinal(GI)diseases have been reported worldwide over the past decades.However,data on changing trends of upper GI diseases remain scarce in sub-Saharan Africa... BACKGROUND Relative changes in the prevalence of gastrointestinal(GI)diseases have been reported worldwide over the past decades.However,data on changing trends of upper GI diseases remain scarce in sub-Saharan Africa.This study examines the shifting patterns of upper GI endoscopic findings over 35 years in Ethiopia.AIM To analyze trends in upper GI endoscopic findings over two distinct time periods,35 years apart,in Ethiopia.METHODS We extracted findings from 8412 upper GI endoscopies performed between 2016 and 2024 at a tertiary referral center in Addis Ababa,Ethiopia.Patient characteristics,indications,and endoscopic findings were analyzed using descriptive statistics and presented in tables,map and graphs.These findings were compared to 10000 procedures conducted between 1979 and 1994.Key endoscopic findings were identified,and percentage changes in disease prevalence were calculated.RESULTS Between the two study periods,the male-to-female ratio of patients undergoing upper GI endoscopy shifted from 2:1 to 1.4:1,while the median patient age increased from 36 to 40 years.The proportion of patients older than 50 years doubled(14.6%to 30.2%),and referrals from outside Addis Ababa increased from 33%to 57%.The prevalence of peptic ulcer disease and its complications decreased from 46.2%to 9.5%.Conversely,gastroesophageal varices increased from 9.5%to 21.8%,and upper GI malignancies rose from 3.6%to 18.8%.CONCLUSION This study sheds light on critical epidemiological shifts in upper GI diseases in Ethiopia,with a decline in peptic ulcer disease and a rise in portal hypertensive lesions and malignancies which have important public health implications.These findings underscore the need for increased awareness,improved clinical practices,enhanced resource allocation,and expanded access to early diagnosis and treatment of prevailing conditions.Preventive strategies targeting immunization and treatment of viral hepatitis,schistosomiasis,and Helicobacter pylori infection are urgently needed. 展开更多
关键词 time trend ENDOSCOPY VARICES Esophageal cancer Gastric cancer STRICTURE
暂未订购
Trend and Periodicity of Temperature Time Series in Ontario 被引量:1
5
作者 Syed Imran Ahmed Ramesh Rudra +1 位作者 Trevor Dickinson Motahir Ahmed 《American Journal of Climate Change》 2014年第3期272-288,共17页
The trends and periodicities in the annual and seasonal temperature time series at fifteen weather stations within Ontario Great Lakes Basins have been analyzed, for the period 1941-2005, using the statistical analyse... The trends and periodicities in the annual and seasonal temperature time series at fifteen weather stations within Ontario Great Lakes Basins have been analyzed, for the period 1941-2005, using the statistical analyses (Fourier series analysis, t-test, and Mann-Kendall test). The stations were spatially divided into three regions: northwest (NW), southwest (SW), and southeast (SE) to evaluate spatial variability in temperature. The results of the study reveal that the annual maximum mean temperature showed increasing trend for NW, and mixed trends for SW and SE regions. The variability was found to be more for northern stations as compared to southern stations for annual extreme minimum temperature. In addition, the trend slope per 100 years for the average annual extreme minimum temperature increased within the range of -0.8°C (Stratford) to 15°C (Porcupine). The seasonal analysis demonstrated that extreme maximum temperature has an increasing trend and maximum mean temperature has a decreasing trend during summer and winter. The extreme minimum temperature for winter illustrated an increasing trend (90%) with 22% statistically significant for NW region. For the SW region, the trend is also increasing (80%) for most of the temperature variables and 25% of temperature data were significantly increased in the SW region. The SE region stations showed overall very clear increasing trends (95%) for all the temperature variables. The data also showed that 47% of data were statistically significant in the SE region. The analysis of variance accounted for by trend, significant periodicities, and random component show that the pattern is similar for the percent of variance accounted for periodicities, and random component contribute dominantly for the four temperature variables and frost free days (FFD) for all three regions. Overall, the study reveals that the extreme minimum temperature is increasing annually and seasonally, with statistically significant at many stations. 展开更多
关键词 time Series trend PERIODICITY MANN-KENDALL Test T-TEST FROST Free Days
在线阅读 下载PDF
Conforming to the Trend at An Appropriate Time——My Thoughts on the Building of the Silk Road Economic Belt 被引量:2
6
作者 Zhang Zhiming Pu Zhuangyi 《International Understanding》 2013年第4期6-8,共3页
During his state visit to Kazakhstan this September,President Xi Jinping made a concrete proposal to build a Silk Road Economic Belt(SREB for short in the following paragraphs)from the aspects of policy communication,... During his state visit to Kazakhstan this September,President Xi Jinping made a concrete proposal to build a Silk Road Economic Belt(SREB for short in the following paragraphs)from the aspects of policy communication,road connectivity, 展开更多
关键词 My Thoughts on the Building of the Silk Road Economic Belt Conforming to the trend at An Appropriate time
在线阅读 下载PDF
Analysis of the Main Factors Influencing Food Production in China Based on Time Series Trend Chart
7
作者 Shuangjin WANG Jianying LI 《Asian Agricultural Research》 2014年第6期37-42,共6页
Based on the annual sample data on food production in China since the reform and opening up,we select 8 main factors influencing the total food production( growing area,application rate of chemical fertilizer,effectiv... Based on the annual sample data on food production in China since the reform and opening up,we select 8 main factors influencing the total food production( growing area,application rate of chemical fertilizer,effective irrigation area,the affected area,total machinery power,food production cost index,food production price index,financial funds for supporting agriculture,farmers and countryside),and put them into categories of material input,resources and environment,and policy factors. Using the factor analysis,we carry out the multi-angle analysis of these typical influencing factors one by one through the time series trend chart. It is found that application rate of chemical fertilizer,the growing area of food crops and drought-affected area become the key factors affecting food production. On this basis,we set forth the corresponding recommendations for improving the comprehensive food production capacity. 展开更多
关键词 FOOD PRODUCTION Influencing FACTORS time SERIES TR
在线阅读 下载PDF
Piecewise linear representation of time series based on mean trend in sliding window
8
作者 袁同雨 吴绍春 +3 位作者 张建 谷蓉蓉 陈高照 徐勇泉 《Journal of Shanghai University(English Edition)》 CAS 2011年第5期473-478,共6页
Seismic data show some important characteristics, such as big volume and strong timeliness. Specific to the time series data of earthquake precursory observations, a piecewise linear representation based on the slidin... Seismic data show some important characteristics, such as big volume and strong timeliness. Specific to the time series data of earthquake precursory observations, a piecewise linear representation based on the sliding window mean value (PLR_MTSW) algorithm is proposed. With this algorithm, the mutation points can be identified accurately according to the rate Of mean value change, while the main features of time series are maintained well. This algorithm can also smooth the noise and improve the compression accuracy with sliding window. Meanwhile the local extreme points can be identified effectively according to the change of mean value trend within window. 展开更多
关键词 earthquake precursor time series changing rate trend
在线阅读 下载PDF
Strengthening Exchanges and Cooperation in the Northeast Asia Region Follows the Trend of the Times——Sidelights of the 10^(th) Northeast Asia Youth Forum
9
作者 Wen Desheng Bai Ruijun 《International Understanding》 2013年第4期33-35,共3页
The 10thNortheast Asia Youth Forum,with the theme of China-ROK-Japan Youth Employment Guidance,sponsored by Moral Re-Armament/Initiatives of Change(MRA/IC)-Korea was held in Seoul and Cheonan from August 12 to 17.Seve... The 10thNortheast Asia Youth Forum,with the theme of China-ROK-Japan Youth Employment Guidance,sponsored by Moral Re-Armament/Initiatives of Change(MRA/IC)-Korea was held in Seoul and Cheonan from August 12 to 17.Seventy five college students from 37 universities sent by China International Youth Exchange Center,Moral Re-Armament/Initiatives of Change(MRA/IC)-Korea and Japan Society attended the Forum.Lee Boksil,Vice-Minister of Ministry of 展开更多
关键词 Re Sidelights of the 10 Strengthening Exchanges and Cooperation in the Northeast Asia Region Follows the trend of the times TH Northeast Asia Youth Forum Asia
在线阅读 下载PDF
Statistical Analysis for Assessing Randomness, Shift and Trend in Rainfall Time Series under Climate Variability and Change: Case of Senegal
10
作者 Didier Maria Ndione Soussou Sambou +4 位作者 Moussé Landing Sane Seydou Kane Issa Leye Seni Tamba Mouhamed Talla Cisse 《Journal of Geoscience and Environment Protection》 2017年第13期31-53,共23页
The main purpose of this study is to assess the climate variability and change through statistical processing tools that able to highlight annual and monthly rainfall behavior between 1970 and 2010 in six strategical ... The main purpose of this study is to assess the climate variability and change through statistical processing tools that able to highlight annual and monthly rainfall behavior between 1970 and 2010 in six strategical raingauges located in northern (Saint-Louis, Bakel), central (Dakar, Kaolack), and southern (Ziguinchor, Tambacounda) part of Senegal. Further, differences in sensitivity of statistical tests are also exhibited by applying several tests rather than a single one to check for one behavior. Dependency of results from statistical tests on studied sequence in time series is also shown comparing results of tests applied on two different periods (1970-2010 and 1960-2010). Therefore, between 1970 and 2010, exploratory data analysis is made to give in a visible manner a first idea on rainfall behavior. Then, Statistical characteristics such as the mean, variance, standard deviation, coefficient of variation, skewness and kurtosis are calculated. Subsequently, statistical tests are applied to all retained time series. Kendall and Spearman rank correlation tests allow verifying whether or not annual rainfall observations are independent. Hubert’s procedures of segmentation, Pettitt, Lee Heghinian and Buishand tests allow checking rainfall homogeneity. Trend is undertaken by first employing the annual and seasonal Mann-Kendall trend test, and in case of significance, magnitude of trend is calculated by Sen’s slope estimator tests. All statistical tests are applied in the period of 1960-2010. Explanatory analysis data indicates upwards trends for records in northern and central and trend free for southern records. Application of multiple tests shows that the Kendall and spearman ranks correlation tests lead to same conclusion. The difference in tests sensitivity was shown by outcomes of homogeneity tests giving different results either in dates of the shift occurrence or in the significance of an eventual shift. A synthesis analysis of results of tests was carried out to conclude about rainfall behaviors. Tests for homogeneity show that southern rainfall is homogeneous, while northern and central ones are not. According to trend test, upwards trends in Northern and central rainfall trend free in southern assumption in exploratory data analysis have been confirmed. The Sen’s slop estimator shows that all retained trend can be assumed to linear type. The same test over the period 1960-2010 shows independence of observations in all raingauges and exhibits neither trends nor breaks. This seems to show a return to a wet period. 展开更多
关键词 Senegal RAINFALL time Series Test INDEPENDENCE HOMOGENEITY SHIFT trend
暂未订购
Comparative Analysis of Climatic Change Trend and Change-Point Analysis for Long-Term Daily Rainfall Annual Maximum Time Series Data in Four Gauging Stations in Niger Delta
11
作者 Masi G. Sam Ify L. Nwaogazie +4 位作者 Chiedozie Ikebude Jonathan O. Irokwe Diaa W. El Hourani Ubong J. Inyang Bright Worlu 《Open Journal of Modern Hydrology》 2023年第4期229-245,共17页
The aim of this study is to establish the prevailing conditions of changing climatic trends and change point dates in four selected meteorological stations of Uyo, Benin, Port Harcourt, and Warri in the Niger Delta re... The aim of this study is to establish the prevailing conditions of changing climatic trends and change point dates in four selected meteorological stations of Uyo, Benin, Port Harcourt, and Warri in the Niger Delta region of Nigeria. Using daily or 24-hourly annual maximum series (AMS) data with the Indian Meteorological Department (IMD) and the modified Chowdury Indian Meteorological Department (MCIMD) models were adopted to downscale the time series data. Mann-Kendall (MK) trend and Sen’s Slope Estimator (SSE) test showed a statistically significant trend for Uyo and Benin, while Port Harcourt and Warri showed mild trends. The Sen’s Slope magnitude and variation rate were 21.6, 10.8, 6.00 and 4.4 mm/decade, respectively. The trend change-point analysis showed the initial rainfall change-point dates as 2002, 2005, 1988, and 2000 for Uyo, Benin, Port Harcourt, and Warri, respectively. These prove positive changing climatic conditions for rainfall in the study area. Erosion and flood control facilities analysis and design in the Niger Delta will require the application of Non-stationary IDF modelling. 展开更多
关键词 Rainfall time Series Data Climate Change trend Analysis Variation Rate Change Point Dates Non-Parametric Statistical Test
在线阅读 下载PDF
Cancer burden in China:trends,risk factors and prevention 被引量:122
12
作者 Dianqin Sun He Li +4 位作者 Maomao Cao Siyi He Lin Lei Ji Peng Wanqing Chen 《Cancer Biology & Medicine》 SCIE CAS CSCD 2020年第4期879-895,共17页
As the most populous country in the world,China has made strides in health promotion in the past few decades.With the aging population,the burden of cancer in China continues to grow.Changes in risk factors for cancer... As the most populous country in the world,China has made strides in health promotion in the past few decades.With the aging population,the burden of cancer in China continues to grow.Changes in risk factors for cancer,especially diet,obesity,diabetes,and air pollution,continue to fuel the shift of cancer transition in China.The burden of upper gastrointestinal cancer in China is decreasing,but still heavy.The rising burden of colorectal,prostate,and breast cancers is also significant.Lung cancer became the top cause of cancer-related deaths,together with smoking as the most important contributor to cancer deaths.The Chinese government has taken several approaches to control cancer and cancer-related risk factors.Many achievements have been made,but some challenges remain.Health China 2030 is ambitious and depicts a bright vision of the future for cancer control in China.The decrease in the cancer burden in China will require cross-sector collaboration and coordinated efforts on primary and secondary preventions by governments,public health organizations,and individuals.In this review,we describe the trends of cancer burden and discuss cancer-related risk factors in China,identifying strategies to reduce the burden of cancer in China. 展开更多
关键词 Cancer burden time trends risk factor PREVENTION China
暂未订购
Changing trends of clinicopathologic features and survival duration after surgery for gastric cancer in Northeast China 被引量:2
13
作者 Zhao Zhai Zi-Yu Zhu +11 位作者 Xi-Liang Cong Bang-Ling Han Jia-Liang Gao Xin Yin Yu Zhang Sheng-Han Lou Tian-Yi Fang Yi-Min Wang Chun-Feng Li Xue-Feng Yu Yan Ma Ying-Wei Xue 《World Journal of Gastrointestinal Oncology》 SCIE CAS 2020年第10期1119-1132,共14页
BACKGROUND Through analyzing the data from a single institution in Northeast China,this study revealed the possible clinicopathologic characteristics that influence the prognosis of patients with gastric cancer(GC).AI... BACKGROUND Through analyzing the data from a single institution in Northeast China,this study revealed the possible clinicopathologic characteristics that influence the prognosis of patients with gastric cancer(GC).AIM To evaluate the changing trends of clinicopathologic features and survival duration after surgery in patients with GC in Northeast China,which is a highprevalence area of GC.METHODS The study analyzed the difference in clinicopathologic features and survival duration after surgery of 5887 patients who were histologically diagnosed with GC at the Harbin Medical University Cancer Hospital.The study mainly analyzed the data in three periods,2000 to 2004(Phase 1),2005 to 2009(Phase 2),and 2010 to 2014(Phase 3).RESULTS Over time,the postoperative survival rate significantly increased from 2000 to 2014.In the past 15 years,compared with Phases 1 and 2,the tumor size was smaller in Phase 3(P<0.001),but the proportion of high-medium differentiated tumors increased(P<0.001).The proportion of early GC gradually increased from 3.9%to 14.4%(P<0.001).A surprising improvement was observed in the mean number of retrieved lymph nodes,ranging from 11.4 to 27.5(P<0.001).The overall 5-year survival rate increased from 24%in Phase 1 to 43.8%in Phase 3.Through multivariate analysis,it was found that age,tumor size,histologic type,tumor-node-metastasis stage,depth of invasion,lymph node metastasis,surgical approach,local infiltration,radical extent,number of retrieved lymph nodes,and age group were independent risk factors that influenced the prognosis of patients with GC.CONCLUSION The clinical features of GC in Northeast China changed during the observation period.The increasing detection of early GC and more standardized surgical treatment effectively prolonged lifetimes. 展开更多
关键词 Gastric cancer Clinicopathologic features SURVIVAL time trends EPIDEMIOLOGY GASTRECTOMY
暂未订购
基于多维度综合决策的猪肉价格时间序列预测模型
14
作者 李蓟涛 姚瑶 +2 位作者 李颖 陈晓 张国锋 《山东农业大学学报(自然科学版)》 北大核心 2026年第1期117-130,共14页
山东省是畜牧业大省,猪肉价格波动对居民生活质量有着重大影响,目前,关于山东省生猪价格波动的预测研究较少,且存在预测时间较短,时间窗口狭窄和预测结果不准确等问题。针对传统预测模型存在长时序预测准确率不足的问题,本文提出了一种... 山东省是畜牧业大省,猪肉价格波动对居民生活质量有着重大影响,目前,关于山东省生猪价格波动的预测研究较少,且存在预测时间较短,时间窗口狭窄和预测结果不准确等问题。针对传统预测模型存在长时序预测准确率不足的问题,本文提出了一种基于综合决策机制的时间序列预测模型。首先,将时间序列信息进行分解,通过可逆归一化将数据特征进行放大,以提取更多的价格波动信息;在信息分解的基础上,通过上采样扩充先验知识,并采用多维度综合决策的方式,增强多层感知机的数据特征挖掘能力和决策能力;最后,将先验知识与预测结果进行直接映射,解决了窗口狭窄和滑动窗口迭代预测导致的误差累积问题。试验结果表明,相较于ARIMA、Prophet-BP、GA-BP、VMD-LSTM和STL-Informer模型,本文算法在RMSE(Root mean square error)和MAE(Mean absolute error)指标上平均提升了50.2%和30.9%,在R^(2)(Coefficient of Determination)指标上的稳定性优于上述对比算法,平均提升了60.2%。本文所提出的算法对于山东省生猪市场的预测性能更优,有助于相关部门对生猪价格波动做出科学决策。 展开更多
关键词 猪肉价格 时间序列预测 趋势分解 上采样 多维度决策
在线阅读 下载PDF
公众知识产权信息服务需求变化与预测
15
作者 庄楠 杨行 《图书馆论坛》 北大核心 2026年第3期65-75,共11页
为探析公众知识产权信息服务需求的变化特征及趋势,文章以国家知识产权局网站咨询平台近十年的公众咨询内容为研究样本,采用扎根理论分析和时间序列分析开展混合研究。研究结果表明,公众知识产权信息服务需求理论模型包括知识产权创造... 为探析公众知识产权信息服务需求的变化特征及趋势,文章以国家知识产权局网站咨询平台近十年的公众咨询内容为研究样本,采用扎根理论分析和时间序列分析开展混合研究。研究结果表明,公众知识产权信息服务需求理论模型包括知识产权创造、运用、管理服务和保护四个核心范畴;近十年来公众知识产权创造相关的需求总体呈下降态势,而知识产权运用、管理服务、保护相关的需求比重呈上升趋势。文章提出我国知识产权信息服务工作提升路径:把握公众需求,拓展知识产权信息服务供给模式;优化服务内容,创新知识产权信息传播利用模式;提升服务效能,加强信息服务平台智能化建设。 展开更多
关键词 知识产权 信息服务 用户需求 时序模型 趋势预测
在线阅读 下载PDF
基于seasonal-trend-loess方法的符号化时间序列网络 被引量:3
16
作者 汪丽娜 成媛媛 臧臣瑞 《物理学报》 SCIE EI CAS CSCD 北大核心 2019年第23期314-322,共9页
为了有效控制海量数据时间序列网络的规模并使得网络更贴近实际,符号化时间序列网络成为研究热点.结合周期性时间序列的seasonal-trend-loess方法和符号化转化方法,本文提出一种新的符号化时间序列建网方法.该方法考虑了单个数据值的状... 为了有效控制海量数据时间序列网络的规模并使得网络更贴近实际,符号化时间序列网络成为研究热点.结合周期性时间序列的seasonal-trend-loess方法和符号化转化方法,本文提出一种新的符号化时间序列建网方法.该方法考虑了单个数据值的状态又结合了序列的长远变化趋势.以符号模式为节点;依时间顺序推移,以节点间的邻接转换关系定义连边;根据转换方向和转换频次确定连边的方向和权重,建立有向加权网络.分别以航空旅客吞吐量时间序列和因特网流量时间序列为实验数据构建的两个时间序列网络,有明显差异的拓扑特征;进一步对移动通信语音时间序列做了实证分析,挖掘时间序列数据的本质规律. 展开更多
关键词 周期时间序列 seasonal-trend-loess方法 复杂网络 拓扑特征
在线阅读 下载PDF
中国陆地生态系统动态生境指数格局及时空动态分析
17
作者 段昊玮 杨莹莹 +5 位作者 万华伟 王永财 张玉沙 卢龙辉 万凤鸣 代玉 《生态学报》 北大核心 2026年第2期691-704,共14页
生境是生态系统中维持生物多样性和生态过程的重要载体,植被生产力的状况和变化直接决定了生境的异质性。近年来,生态修复工程的实施推动了中国生境质量好转和生态系统结构变化,系统解析生境质量变化规律对提升我国生态系统服务功能和... 生境是生态系统中维持生物多样性和生态过程的重要载体,植被生产力的状况和变化直接决定了生境的异质性。近年来,生态修复工程的实施推动了中国生境质量好转和生态系统结构变化,系统解析生境质量变化规律对提升我国生态系统服务功能和保护生物多样性具有重要意义。基于卫星遥感大数据构建的动态生境指数(DHIs)从可用能量、环境稳定性、环境压力三方面有效评估生境生产力与生物多样性。为明确近十余年中国的生境生产力状况及动态变化特征,基于Google Earth Engine平台计算了中国累积DHI(DHI_(cum))、变异DHI(DHI_(var))与最小DHI(DHI_(min)),利用时间序列分析方法,对中国内地地区(不含港澳台)2010—2023年的DHIs变化进行了研究,揭示了我国不同生态系统、整体的DHIs格局及其DHIs的时空变化差异。综合来看,DHIs在生态环境质量监测、生物多样性管理与评估中具有不同的侧重和互补的重要意义。研究表明:(1)空间上,我国东南沿海向西北内陆地区累积生产力逐步递减、环境压力增加;东南沿海环境稳定性高于西北内陆。(2)14年来中国内地区域50%以上植被覆盖区总初级生产力改善,总体改善主要分布在大小兴安岭、四川盆地,云贵高原等区域,改善较为明显。(3)约三分之一区域受干旱气候与人类活动加剧的影响,生产力出现退化,以大兴安岭北部、青藏高原中部、洞庭湖流域等为主,其中洞庭湖流域等地区受土地利用类型转变影响较大。生境生产力变化与气候及生态保护工程等其他人类活动密切相关,植树造林、荒漠化治理等重大工程为提升生产力水平做出了重大贡献,而城镇扩张等城市化建设则限制了其地区的生产力水平。总体来看,各生态系统DHIs为可用能量、环境稳定性提高,环境压力降低为主的趋势,森林虽环境稳定性和压力改善明显,但累积生产力退化略高。多种生态系统DHIs变化趋势具有明显空间异质性。研究结果为中国生态保护和生物多样性监测评估提供了科学参考。 展开更多
关键词 动态生境指数 遥感时间序列 植被生产力 趋势分析
在线阅读 下载PDF
基于改进RSEI的巴彦淖尔市生态环境质量分析
18
作者 马斌畅 于新海 白珍 《现代信息科技》 2026年第2期161-165,共5页
基于2000—2023年Landsat遥感影像,文章构建改进遥感生态指数(RSEI),将原有干度指标NDBSI替换为地表裸土指数(SI),以系统评估巴彦淖尔市生态环境质量。通过主成分分析、相关性检验及时序趋势分析,揭示区域生态质量的时空演变特征及驱动... 基于2000—2023年Landsat遥感影像,文章构建改进遥感生态指数(RSEI),将原有干度指标NDBSI替换为地表裸土指数(SI),以系统评估巴彦淖尔市生态环境质量。通过主成分分析、相关性检验及时序趋势分析,揭示区域生态质量的时空演变特征及驱动机制。结果显示:改进RSEI均值呈波动上升趋势,年均复合增长率为0.286%;空间分布呈“南优北劣”特征,河套平原生态质量较高,北部及西部荒漠化区域仍处于低值水平;NDVI与WET对生态改善具有显著正向作用,其中NDVI贡献逐年增强,为核心驱动因子;SI与LST对改进RSEI影响显著为负,裸土暴露与干旱问题制约生态提升。研究表明,三北防护林工程及退耕还林还草等生态治理措施显著改善了区域生态环境,但水资源不足与土地荒漠化仍是当前面临的持续挑战。 展开更多
关键词 RSEI 生态环境 巴彦淖尔市 生态质量 主成分分析 相关性检验 时序趋势分析
在线阅读 下载PDF
基于多维知识元的科学—技术关联主题识别及发展态势测度研究——以人工智能领域为例
19
作者 张鹤翔 孙震 唐苗 《现代情报》 北大核心 2026年第2期61-76,共16页
[目的/意义]将科学与技术的知识要素置于统一分析框架下进行系统整合与动态测度,对把握创新发展态势、优化资源配置及提升国家创新体系效能具有重要价值。[方法/过程]本文立足科技协同创新整体视角,以论文与专利作为科学与技术知识要素... [目的/意义]将科学与技术的知识要素置于统一分析框架下进行系统整合与动态测度,对把握创新发展态势、优化资源配置及提升国家创新体系效能具有重要价值。[方法/过程]本文立足科技协同创新整体视角,以论文与专利作为科学与技术知识要素的载体,将科学—技术关联主题作为科学与技术知识要素重构和融合的分析单元。首先运用主题挖掘方法识别科学、技术主题,并引入知识元理论对主题内部的知识要素进行抽取与语义—结构—时序三维表征;随后基于知识元的语义关联与网络结构特征识别科学—技术关联主题,结合其生命周期演化特征,从创新活跃度、创新成熟度、创新衰弱度3个维度构建指标体系,借助战略定位坐标图对关联主题的发展态势进行测度与分类。[结果/结论]通过对人工智能领域的实证研究,识别出206对科学—技术关联主题并将其划分为前沿创新型、新兴潜力型等8种类型。实证结果表明,本文构建的基于多维知识元的科学—技术关联主题识别及发展态势测度方法具有较强的实用性与领域拓展性,可为学术界与产业界在前沿布局规划、创新资源配置等方面提供系统化的情报支撑。 展开更多
关键词 科学—技术关联 知识元 多维表征 时间序列演化 态势测度 主题识别 人工智能
在线阅读 下载PDF
Trends in the survival of patients with nasopharyngeal carcinoma between 1976 and 2005 in Sihui, China: a population-based study 被引量:12
20
作者 Qing Liu Jin-Ou Chen +1 位作者 Qi-Hong Huang Yan-Hua Li 《Chinese Journal of Cancer》 SCIE CAS CSCD 2013年第6期325-333,共9页
Both the incidence a nd mortality of nasopharyngeal carcinoma(NPC) have decreased in Hong Kong and Taiwan but not in China's Mainland. The goal of this study was to analyze trends in NPC patient survival between 1... Both the incidence a nd mortality of nasopharyngeal carcinoma(NPC) have decreased in Hong Kong and Taiwan but not in China's Mainland. The goal of this study was to analyze trends in NPC patient survival between 1976 and 2005 in Sihui, an area of China's Mainland with a population at high risk for NPC. A total of 1,761 patients diagnosed with NPC between 1976 and 2005 according to the records of Sihui Cancer Registry were followed to the end of 2006. We determined their observed and relative survival rates and used Cox proportional hazards regression analysis to predict prognosis. Our results showed that the 5-year and 10-year observed survival rates of NPC patients in Sihui were 50.5% and 36.9% , respectively, and the median survival time was 5.1 years. The 5-year observed survival rate of NPC patients diagnosed after 2000 was 69.8%, significantly higher than that of patients diagnosed between 1976 and 1985 (42.5% ; P<0.001, relative risk=0.28). Similarly, the 5-year relative survival rate was 84.8% between 2000 and 2005 but 51.8% between 1976 and 1985. Besides date of diagnosis, other prognostic factors included patient sex and age and NPC clinical stage and histologic type. The relative risks of death from NPC were 0.76 [95% confidence interval (CI): 0.65-0.90] for female comparing to male and 1.28 (95% CI: 1.00-1.64) for WHO type I comparing to WHO types II and III. For the eldest age group and the latest clinical stage group, the relative risks were 2.22 (95% CI: 1.73-2.84) and 3.41 (95% CI: 2.34-4.49), respectively. Our results indicate that the survival of NPC patients in Sihui has significantly increased in recent years and this increase is not influenced by patient's sex, age, histologic type, and clinical stage. A reduction in mortality rate is expected in coming years. 展开更多
关键词 中国大陆地区 鼻咽癌 四会市 患者 人口 基础 世界卫生组织 NPC
暂未订购
上一页 1 2 57 下一页 到第
使用帮助 返回顶部