期刊文献+
共找到736,598篇文章
< 1 2 250 >
每页显示 20 50 100
Guiding the younger generation to explore new scenarios for participating in standards development and application
1
作者 Li Zhiping 《China Standardization》 2026年第1期43-44,共2页
Standards are the common language that consolidates global consensus and builds the most solid foundation for international partnerships.They are the cornerstone for global sustainable and high-quality development.You... Standards are the common language that consolidates global consensus and builds the most solid foundation for international partnerships.They are the cornerstone for global sustainable and high-quality development.Young students,with their active and vibrant minds,represent the future and hope of standardization. 展开更多
关键词 standards development sustainable development application standards international partnerships high quality development consolidates global consensus younger generation common language
原文传递
China’s Urban-Rural Integration:A Global Perspective on Sustainable Development
2
作者 XIA YUANYUAN 《China Today》 2026年第1期36-38,共3页
China is carving out a distinctive development path which features urban-rural integration.This approach has not only yielded tangible results domestically but also drawn the attention of other countries.
关键词 sustainable development urban rural integration China development path
在线阅读 下载PDF
Standards lead the high-quality development of intelligent construction in China
3
作者 Cheng Zhijun 《China Standardization》 2026年第1期49-49,共1页
To advance intelligent construction,standards must come first.The Ministry of Housing and Urban-Rural Development has issued the List for Replicable Experience and Practices for Developing Intelligent Construction fou... To advance intelligent construction,standards must come first.The Ministry of Housing and Urban-Rural Development has issued the List for Replicable Experience and Practices for Developing Intelligent Construction four times successively and the Technical Guidelines for Intelligent Construction(Trial). 展开更多
关键词 sTANDARDs technical guidelines high quality development Ministry Housing Urban Rural development intelligent constructionstandards replicable experience intelligent construction
原文传递
Intersection of mitochondrial dysfunction and myelination:An overlooked aspect in neurodevelopmental disorders
4
作者 Ariel Nir Sade Gal Wiener Boaz Barak 《Neural Regeneration Research》 2026年第2期659-660,共2页
Neurodevelopmental processes represent a finely tuned interplay between genetic and environmental factors,shaping the dynamic landscape of the developing brain.A major component of the developing brain that enables th... Neurodevelopmental processes represent a finely tuned interplay between genetic and environmental factors,shaping the dynamic landscape of the developing brain.A major component of the developing brain that enables this dynamic is the white matter(WM),known to be affected in neurodevelopmental disorders(NDDs)(Rokach et al.,2024).WM formation is mediated by myelination,a multifactorial process driven by neuro-glia interactions dependent on proper neuronal functionality(Simons and Trajkovic,2006).Another key aspect of neurodevelopmental abnormalities involves neuronal dynamics and function,with recent advances significantly enhancing our understanding of both neuronal and glial mitochondrial function(Devine and Kittler,2018;Rojas-Charry et al.,2021).Energy homeostasis in neurons,attributed largely to mitochondrial function,is critical for proper functionality and interactions with oligodendrocytes(OLs),the cells forming myelin in the brain’s WM.We herein discuss the interplay between these processes and speculate on potential dysfunction in NDDs. 展开更多
关键词 neurodevelopmental disorders ndds rokach white matter developing brain MYELINATION neurodevelopmental processes mitochondrial dysfunction white matter wm known developing braina
暂未订购
Study on the development,applications,and standardization status of environmental DNA(eDNA)technology in China
5
作者 Li Xiawei Duan Bin +3 位作者 Lu Jing Li Xueling Wang Min Yang Yongqi 《China Standardization》 2026年第1期54-59,共6页
Environmental DNA(eDNA)technology has revolutionized biodiversity monitoring with its non-invasive,sensitive,and cost-efficient approach.This paper systematically reviews eDNA advancements,examining its applications i... Environmental DNA(eDNA)technology has revolutionized biodiversity monitoring with its non-invasive,sensitive,and cost-efficient approach.This paper systematically reviews eDNA advancements,examining its applications in aquatic and terrestrial ecosystems and assessing China’s standardization progress.It delineates four developmental phases from single-species detection to high-throughput sequencing,and highlights China’s contribution to the development of technical standards.While significant progress has been made,challenges persist in quantitative accuracy,methodological consistency,and large-scale implementation.Future efforts should prioritize enhanced standardization,improved quantification techniques,broader applications,and international collaboration to drive innovation in eDNA technology. 展开更多
关键词 environmental DNA development application standardization status
原文传递
National development requires the younger generation to cultivate the standardization consciousness and mindset
6
作者 Zhang Xiaogang 《China Standardization》 2026年第1期42-42,共1页
The International Standardization Youth Star Competition is held for three consecutive years.We have witnessed continuous improvement in the competition each year,which is a result of our collective efforts.
关键词 collective efforts youth competition national development improvement standardization consciousness
原文传递
The role of m^(6)A in plant development,stress response,and agricultural practices
7
作者 Jin Qi Shaoxia Li +3 位作者 Jun Su Yushi Lu Wenjin Yu Changxia Li 《Horticultural Plant Journal》 2026年第1期19-35,共17页
N6-methyladenosine(m^(6)A)modification,the most abundant internal modification in messenger RNA(mRNA)and long non-coding RNA(lncRNA),has emerged as a critical epitranscriptomic regulatory mechanism in eukaryotes.While... N6-methyladenosine(m^(6)A)modification,the most abundant internal modification in messenger RNA(mRNA)and long non-coding RNA(lncRNA),has emerged as a critical epitranscriptomic regulatory mechanism in eukaryotes.While the importance of m^(6)A modification in various biological processes has been recognized,a comprehensive understanding of its diverse roles in plant biology and agricultural applications remains fragmented.This review analyzes recent advances inm^(6)A modification's biological functions in plants.m^(6)A modification plays crucial roles in multiple aspects of plant life,including seed germination,organ development,and reproductive structure formation.Furthermore,m^(6)A has been found to significantly influence plant responses to environmental stresses,including salt,drought,temperature,and heavy metal exposure.We also uncover m^(6)A involvement in important agricultural traits.This review provides insights into the mechanistic understanding of m^(6)A modification in plants and highlights its applications in agricultural improvement,offering a foundation for future research in crop enhancement and stress resistance. 展开更多
关键词 N6-methyladenosine Epitranscriptomics Plant development sTREss Agricultural production
在线阅读 下载PDF
Ideas in Motion--Xi Jinping:The Governance of China sparks fresh reflections on Africa’s development pathways
8
《ChinAfrica》 2026年第1期14-19,共6页
Governance debates gained strong momentum in Africa in early December 2025 as the China-Kenya Readers Forum on Xi Jinping:The Governance of China convened in Nairobi on 1 December 2025,followed by a promotional event ... Governance debates gained strong momentum in Africa in early December 2025 as the China-Kenya Readers Forum on Xi Jinping:The Governance of China convened in Nairobi on 1 December 2025,followed by a promotional event for the English edition of the book’s fifth volume on 3 December 2025 in Johannesburg,South Africa. 展开更多
关键词 NAIROBI JOHANNEsBURG south Africa China Kenya Xi Jinping development pathways GOVERNANCE
原文传递
Progress in Offshore Oilfield Development Planning
9
作者 L.M.R.Silva C.Guedes Soares 《哈尔滨工程大学学报(英文版)》 2026年第1期136-161,共26页
This study examines the methods to plan the development of offshore oilfields over the years,which are used to support the decision-making on the development of offshore oilfields.About 100 papers are analysed and cat... This study examines the methods to plan the development of offshore oilfields over the years,which are used to support the decision-making on the development of offshore oilfields.About 100 papers are analysed and categorised into different groups of main early-stage decisions.The present study stands in contrast to the contributions of the operations research and system engineering review articles,on the one hand,and the petroleum engineering review articles,on the other.This is because it does not focus on one methodological approach,nor does it limit the literature analysis by offshore oilfield characteristics.Consequently,the present analysis may offer valuable insights,for instance,by identifying environmental planning decisions as a recent yet highly significant concern that is currently being imposed on decision-making process.Thus,it is evident that the incorporation of safety criteria within the technical-economic decision-making process for the design of production systems would be a crucial requirement at development phase. 展开更多
关键词 Offshore oilfield development Oilfield planning decisions Production system design Decision-making process
在线阅读 下载PDF
Measuring hydrological alterations and landscape patterns for sustainable development through ecosystem connectivity in Hastinapur Wildlife Sanctuary,India
10
作者 Sonali Kundu Narendra Kumar Rana Barnali Kundu 《Journal of Environmental Sciences》 2026年第1期322-338,共17页
Floodplain wetlands are invaluable ecosystems providing numerous ecological benefits,yet they face a global crisis necessitating sustainable preservation efforts.This study examines the depletion of floodplain wetland... Floodplain wetlands are invaluable ecosystems providing numerous ecological benefits,yet they face a global crisis necessitating sustainable preservation efforts.This study examines the depletion of floodplain wetlands within the Hastinapur Wildlife Sanctuary(HWLS)in Uttar Pradesh.Encroachment activities such as grazing,agriculture,and human settlements have fragmented and degraded critical wetland ecosystems.Additionally,irrigation projects,dam construction,and water diversion have disrupted natural water flow and availability.To assess wetland inundation in 2023,five classification techniques were employed:Random Forest(RF),Support Vector Machine(SVM),artificial neural network(ANN),Spectral Information Divergence(SID),and Maximum Likelihood Classifier(MLC).SVM emerged as the most precise method,as determined by kappa coefficient and index-based validation.Consequently,the SVM classifier was used to model wetland inundation areas from 1983 to 2023 and analyze spatiotemporal changes and fragmentation patterns.The findings revealed that the SVM clas-sifier accurately mapped 2023 wetland areas.The modeled time-series data demonstrated a 62.55%and 38.12%reduction in inundated wetland areas over the past 40 years in the pre-and post-monsoon periods,respectively.Fragmentation analysis indicated an 86.27%decrease in large core wetland areas in the pre-monsoon period,signifying severe habitat degradation.This rapid decline in wetlands within protected areas raises concerns about their ecological impacts.By linking wetland loss to global sustainability objectives,this study underscores the global urgency for strengthened wetland protection measures and highlights the need for integrating wetland conservation into broader sustainable development goals.Effective policies and adaptive management strategies are crucial for preserving these ecosystems and their vital services,which are essential for biodiversity,climate regulation,and human well-being. 展开更多
关键词 Wetland monitoring Hastinapur wildlife sanctuary Landscape fragmentation sustainable development goals Ecosystem connectivity
原文传递
mTORC1 and mTORC2 synergy in human neural development, disease, and regeneration
11
作者 Navroop K.Dhaliwal Julien Muffat Yun Li 《Neural Regeneration Research》 2026年第4期1552-1553,共2页
The mechanistic target of rapamycin(m TOR) is a serine/threonine kinase that plays a pivotal role in cellular growth, proliferation, survival, and metabolism. In the central nervous system(CNS), the mTOR pathway regul... The mechanistic target of rapamycin(m TOR) is a serine/threonine kinase that plays a pivotal role in cellular growth, proliferation, survival, and metabolism. In the central nervous system(CNS), the mTOR pathway regulates diverse aspects of neural development and function. Genetic mutations within the m TOR pathway lead to severe neurodevelopmental disorders, collectively known as “mTORopathies”(Crino, 2020). Dysfunctions of m TOR, including both its hyperactivation and hypoactivation, have also been implicated in a wide spectrum of other neurodevelopmental and neurodegenerative conditions, highlighting its importance in CNS health. 展开更多
关键词 m tor neural development mtorc central nervous system cns mtor neurodevelopmental disorders neurodegenerative conditions
暂未订购
Inter-Regional Tech Complementarity:A Mechanism for Balanced Development and GVC Upgrading
12
作者 Zheng Jianghuai Jin Shengnan 《China Economist》 2026年第1期2-32,共31页
In the complex architecture of global value-chain(GVC)trade,firms’technological content increasingly reflects external knowledge flows.This study examines how inter-regional technological complementarity shapes firms... In the complex architecture of global value-chain(GVC)trade,firms’technological content increasingly reflects external knowledge flows.This study examines how inter-regional technological complementarity shapes firms’GVC advancement,measured by the domestic value-added rate(DVAR)in exports.Using integrated Chinese microdata(2000-2014),we find this complementarity significantly boosts export DVAR,explaining about one-quarter of its observed growth.Two mechanisms drive this effect:increased use of domestic intermediates and gains in firm productivity.The benefits are especially large for firms with lower human capital and for those in accessible,innovation-peripheral regions,helping narrow productivity gaps across firms and space.Affected firms also exhibit broader export scopes,higher product quality,more diversified destinations,and greater markups-firm-level evidence of GVC upgrading.These findings highlight how external technological linkages drive upgrading and underscore the importance of fostering inter-regional synergies for balanced development. 展开更多
关键词 technological complementarity global value chains domestic value-added rate(DVAR) balanced regional development
在线阅读 下载PDF
Cardiac Organoids:Emerging Tools for Investigating Environmental Roles in Cardiomyopathy Pathogenesis and Therapeutic Development
13
作者 Yaoyao Xu Zhimin Wang 《Biomedical and Environmental Sciences》 2026年第1期82-104,共23页
Human cardiac organoids have revolutionized the study of cardiac development,disease modeling,drug discovery,and regenerative therapies.This review systematically discusses strategies and progress in the construction ... Human cardiac organoids have revolutionized the study of cardiac development,disease modeling,drug discovery,and regenerative therapies.This review systematically discusses strategies and progress in the construction of cardiac organoids,categorizing them into three main types:cardiac spheroids,self-organizing/assembloid organoids,and organoid-on-a-chip systems.This review uniquely integrates the advances in vascularization,organ-on-chip design,and environmental cardiotoxicity modeling within cardiac organoid platforms,offering a critical synthesis that is absent in the literature.In the context of escalating environmental threats to cardiovascular health,there is an urgent need for physiologically relevant models to accurately identify cardiac toxicants and elucidate their underlying mechanisms of action.This review highlights advances in cardiac organoid applications for disease modeling—including congenital heart defects and acquired cardiovascular diseases—drug development,toxicity screening,and the study of environmentally induced cardiovascular pathogenesis.In addition,it critically examines ongoing challenges and underscores opportunities brought by bioengineering approaches.Finally,we propose future directions for developing standardized cardiac organoid platforms with clinical predictability,aiming to expand the utility of this technology across broader research applications. 展开更多
关键词 regenerative therapiesthis therapeutic development environmental cardiotoxicity modeling cardiac organoids cardiomyopathy pathogenesis cardiac organoidscategorizing environmental roles
暂未订购
NVIDIA Jetson Orin Nano Super Developer Kit发布,推动AI边缘计算应用发展 被引量:1
14
《自动化博览》 2025年第2期8-8,共1页
NVIDIA Jetson作为先进的嵌入式系统,各行各业的开发人员可以使用它们来构建创新型AI产品。2024年12月,NVIDIA发布了Jetson系列新品—Jetson Orin Nano Super Developer Kit,做为Jetson Nano的升级款,模组售价仅仅249美元,NVIDIA以更加... NVIDIA Jetson作为先进的嵌入式系统,各行各业的开发人员可以使用它们来构建创新型AI产品。2024年12月,NVIDIA发布了Jetson系列新品—Jetson Orin Nano Super Developer Kit,做为Jetson Nano的升级款,模组售价仅仅249美元,NVIDIA以更加亲民的价格,赋予更多领域充足的算力支持。 展开更多
关键词 NVIDIA Jetson Orin Nano super developer Kit
在线阅读 下载PDF
Latest progress and challenges in drug development for degenerative motor neuron diseases
15
作者 Xiangjin Wen Tianxiang Lan +3 位作者 Weiming Su Bei Cao Yi Wang Yongping Chen 《Neural Regeneration Research》 2026年第5期1849-1863,共15页
Motor neuron diseases are sporadic or inherited fatal neurodegenerative conditions.They selectively affect the upper and/or lower motor neurons in the brain and spinal cord and feature a slow onset and a subacute cour... Motor neuron diseases are sporadic or inherited fatal neurodegenerative conditions.They selectively affect the upper and/or lower motor neurons in the brain and spinal cord and feature a slow onset and a subacute course contingent upon the site of damage.The main types include amyotrophic lateral sclerosis,progressive muscular atrophy,primary lateral sclerosis,and progressive bulbar palsy,the pathological processes of which are largely identical,with the main disparity lying in the location of the lesions.Amyotrophic lateral sclerosis is the representative condition in this group of diseases,while other types are its variants.Hence,this article mainly focuses on the advancements and challenges in drug research for amyotrophic lateral sclerosis but also briefly addresses several other important degenerative motor neuron diseases.Although the precise pathogenesis remains elusive,recent advancements have shed light on various theories,including gene mutation,excitatory amino acid toxicity,autoimmunology,and neurotrophic factors.The US Food and Drug Administration has approved four drugs for use in delaying the progression of amyotrophic lateral sclerosis:riluzole,edaravone,AMX0035,and tofersen,with the latter being the most recent to receive approval.However,following several phaseⅢtrials that failed to yield favorable outcomes,AMX0035 has been voluntarily withdrawn from both the US and Canadian markets.This article presents a comprehensive summary of drug trials primarily completed between January 1,2023,and June 30,2024,based on data sourced from clinicaltrials.gov.Among these trials,five are currently in phaseⅠ,seventeen are in phaseⅡ,and eleven are undergoing phaseⅢevaluation.Notably,24 clinical trials are now investigating potential disease-modifying therapy drugs,accounting for the majority of the drugs included in this review.Some promising drugs being investigated in preclinical studies,such as ATH-1105,are included in our analysis,and another review in frontiers in gene therapy and immunotherapy has demonstrated their therapeutic potential for motor neuron diseases.This article was written to be an overview of research trends and treatment prospects related to motor neuron disease drugs,with the aim of highlighting the latest potentialities for clinical therapy. 展开更多
关键词 amyotrophic lateral sclerosis clinical trial degenerative motor neuron diseases disease modifying therapy drug development motor neuron disease
暂未订购
SlSWEET5a and SlSWEET5b redundantly regulate early fruit development by mediating sugar transport in tomato
16
作者 Mengyao Liang Hairen Xu +4 位作者 Hexu Cai Haijing Wang Shuai Sun Xia Cui Ren Li 《Horticultural Plant Journal》 2026年第1期212-216,共5页
In tomato,early fruit development involves rapid cell division and expansion,which are highly dependent on sugar availability(Huang et al.,2025;Yuan et al.,2025).After fruit set,soluble sugars are loaded into pericarp... In tomato,early fruit development involves rapid cell division and expansion,which are highly dependent on sugar availability(Huang et al.,2025;Yuan et al.,2025).After fruit set,soluble sugars are loaded into pericarp cells through the symplasmic(cytosol)or apoplasmic pathway(cell wall and extracellular matrix)(Patrick and Offler,1996).Sucrose,as the major form of carbon translocated to tomato fruit,can be directly unloaded into fruit cells.However,some sucrose can be hydrolyzed by extracellular invertase,producing glucose and fructose for metabolism and biosynthesis in pericarp cells(Ruan,2014). 展开更多
关键词 fruit development sugar transport extracellular matrix patrick apoplasmic pathway cell wall slsweet pericarp cells slsweet b extracellular invertasepro
在线阅读 下载PDF
Critical Success Factors to Improve the Game Development Process from a Developer's Perspective
17
作者 Saiqa Aleem Luiz Fernando Capretz Faheem Ahmed 《Journal of Computer Science & Technology》 SCIE EI CSCD 2016年第5期925-950,共26页
The growth of the software game development industry is enormous and is gaining importance day by day. This growth imposes severe pressure and a number of issues and challenges on the game development community. Game ... The growth of the software game development industry is enormous and is gaining importance day by day. This growth imposes severe pressure and a number of issues and challenges on the game development community. Game development is a complex process, and one important game development choice is to consider the developer's perspective to produce good-quality software games by improving the game development process. The objective of this study is to provide a better understanding of the developer's dimension as a factor in software game success. It focuses mainly on an empirical investigation of the effect of key developer's factors on the software game development process and eventually on the quality of the resulting game. A quantitative survey was developed and conducted to identify key developer's factors for an enhanced game development process. For this study, the developed survey was used to test the research model and hypotheses. The results provide evidence that game development organizations must deal with multiple key factors to remain competitive and to handle high pressure in the software game industry. The main contribution of this paper is to investigate empirically the influence of key developer's factors on the game development process. 展开更多
关键词 developer's perspective software game empirical investigation good-quality game game development process game developer's factor
原文传递
Encouraging Thai Real Estate Developers Toward Net Zero:A Case Study on Factors Influencing Decision-Making in Net Zero Building Development
18
作者 Pornraht Pongprasert Satapat Kanchong 《Journal of Environmental & Earth Sciences》 2025年第8期22-35,共14页
The concept of Net Zero Carbon Buildings,which aims to reduce greenhouse gas emissions,is essential in addressing climate change.However,the development of such buildings in Thailand faces significant challenges,inclu... The concept of Net Zero Carbon Buildings,which aims to reduce greenhouse gas emissions,is essential in addressing climate change.However,the development of such buildings in Thailand faces significant challenges,including high construction costs,uncertain returns,and limited investment incentives.This study explores the factors influencing real estate developers’decisions to pursue Net Zero Carbon Buildings in Thailand,with a focus on physical,financial,and policy-related elements.Data collection was done with 388 respondents who are stakeholders,including developers,consultants,designers,and sustainability experts,through an online questionnaire,and analyzed using Multiple Regression Analysis.The independent variables in the analytical model consist of three groups of factors:physical buildings,climate finance,and climate policy.The results indicate that physical building factors,including building age,engineering systems,and design;climate finance factors,such as project cost increases,financial returns,and investment incentives;and climate policy factors,including government policies,international climate agreements,and carbon taxes,significantly influence development decisions.Government policies,building engineering systems,and financial incentives were identified as key positive drivers for investment,while carbon taxes and energy efficiency-focused designs were found to potentially discourage investment due to higher costs.The study concludes that substantial government support such as tax incentives,grants,and low-interest financing is critical to fostering investment in Net Zero Carbon Buildings.Additionally,raising awareness among developers and the private sector about the long-term benefits of these projects is essential to strengthening investment incentives. 展开更多
关键词 Zero Carbon Emission Net Zero Carbon Buildings Climate Finance Climate Policy Real Estate development Thailand
在线阅读 下载PDF
基于ST-Developer10几何信息提取方法的研究 被引量:5
19
作者 王军 刘哲 +1 位作者 孙军 聂新刚 《沈阳建筑大学学报(自然科学版)》 EI CAS 2006年第1期163-167,共5页
目的为以通用性标准提取三维模型的几何信息.以STEP AP 203数据模型为输入信息,研究三维模型几何信息的提取方法.方法在ST-Developer10的环境下,以VC++6.0为开发工具,使用ROSE库函数,将EXPRESS语言描述的AP 203文件信息转换为STEP设计... 目的为以通用性标准提取三维模型的几何信息.以STEP AP 203数据模型为输入信息,研究三维模型几何信息的提取方法.方法在ST-Developer10的环境下,以VC++6.0为开发工具,使用ROSE库函数,将EXPRESS语言描述的AP 203文件信息转换为STEP设计对象和C++类,按AP 203数据模型的几何信息属性的层次结构,逐次提取几何信息.结果使用ROSE C++类库提取AP 203文件头段信息.设计了数据段信息提取的流程,分为信息转换、几何信息提取和三维实体显示三部分,实现三维几何信息的提取,并显示出提取结果.结论以AP 203文件的几何模型信息为源信息,进行几何信息的提取,其提取结果也是基于STEP标准的,通用性好,可在不同的CAX系统之间传递与共享,可作为CAPP系统设计的直接输入信息,对实现CAD/CAPP集成提供了技术支持,是实现STEP-NC的基础. 展开更多
关键词 几何信息 sTEP标准 AP203 信息提取 sT—developer10
在线阅读 下载PDF
Developer Express.Net控件中内嵌的Ajax技术研究 被引量:2
20
作者 魏志明 李家 吕天阳 《绿色科技》 2016年第20期154-156,159,共4页
指出了Developer Express.Net是一款功能齐全、界面美观的.NET基础控件库,为.NET框架进行充分优化,可以最大限度地提高用户的开发效率。Ajax是Web 2.0的核心技术之一,它利用客户端的JavaScript和服务器端代码进行异步通信来实现页面局... 指出了Developer Express.Net是一款功能齐全、界面美观的.NET基础控件库,为.NET框架进行充分优化,可以最大限度地提高用户的开发效率。Ajax是Web 2.0的核心技术之一,它利用客户端的JavaScript和服务器端代码进行异步通信来实现页面局部更新,可为用户提供了更好的操作体验。以ASPxGridView、ASPxCallback、控件为例研究了其中的Ajax技术。 展开更多
关键词 AJAX developer Express.NET AsPx控件
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部