首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   521331篇
  免费   10471篇
  国内免费   12336篇
教育   344297篇
科学研究   79099篇
各国文化   1134篇
体育   48004篇
综合类   29161篇
文化理论   1780篇
信息传播   40663篇
  2023年   1682篇
  2022年   7441篇
  2021年   14551篇
  2020年   12443篇
  2019年   11300篇
  2018年   10520篇
  2017年   11859篇
  2016年   9589篇
  2015年   14615篇
  2014年   23349篇
  2013年   48653篇
  2012年   34747篇
  2011年   38324篇
  2010年   37808篇
  2009年   36119篇
  2008年   36696篇
  2007年   37132篇
  2006年   34111篇
  2005年   27507篇
  2004年   18616篇
  2003年   13214篇
  2002年   12162篇
  2001年   10003篇
  2000年   6763篇
  1999年   4084篇
  1998年   2360篇
  1997年   2118篇
  1996年   2033篇
  1995年   1744篇
  1994年   1562篇
  1993年   1339篇
  1992年   1450篇
  1991年   1351篇
  1990年   1251篇
  1989年   1220篇
  1988年   1069篇
  1987年   892篇
  1986年   951篇
  1985年   952篇
  1984年   829篇
  1983年   762篇
  1982年   659篇
  1981年   637篇
  1980年   574篇
  1979年   757篇
  1978年   624篇
  1977年   557篇
  1976年   468篇
  1975年   426篇
  1974年   429篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
101.
ABSTRACT

The preservation of artefacts in museum collections is profoundly affected by fluctuations in temperature and, especially, relative humidity (RH). Since the late nineteenth century, many studies have been carried out on the best way to control hygrothermal conditions. In old buildings located in maritime temperate climate zones (such as Portugal) with strong thermal inertia, and which have low ventilation rate (relative to the volume and number of visitors), daily and seasonal hygroscopic inertia may help to assure the maintenance of RH stabilization conditions. The use of expensive active systems may be minimized through the passive behaviour of internal finishing building materials. This work presents the results of an experimental laboratory study conducted in a flow chamber to demonstrate the enormous potential of hygroscopic materials in stabilizing interior relative humidity. Based in these results and in-situ monitoring in a museum housed in a building, located in Porto, with a typical construction of the 1950s (granite masonry and reinforced concrete slabs), a numerical analysis was done to quantify the influence of hygroscopic materials in stabilizing the interior relative humidity.  相似文献   
102.
Cultural Studies of Science Education - In this paper, I engage with arguments put forth by Anna Günther-Hanssen in her article “A swing and a child: How scientific phenomena can come to...  相似文献   
103.
Review helpfulness is attracting increasing attention of practitioners and academics. It helps in reducing risks and uncertainty faced by users in online shopping. This study examines uninvestigated variables by looking at not only the review characteristics but also important indicators of reviewers. Several significant review content and two reviewer variables are proposed and an effective review helpfulness prediction model is built using stochastic gradient boosting learning method. This study derived a mechanism to extract novel review content variables from review text. Six popular machine learning models and three real-life Amazon review data sets are used for analysis. Our results are robust to several product categories and along three Amazon review data sets. The results show that review content variables deliver the best performance as compared to the reviewer and state-of-the-art baseline as a standalone model. This study finds that reviewer helpfulness per day and syllables in review text strongly relates to review helpfulness. Moreover, the number of space, aux verb, drives words in review text and productivity score of a reviewer are also effective predictors of review helpfulness. The findings will help customers to write better reviews, help retailers to manage their websites intelligently and aid customers in their product purchasing decisions.  相似文献   
104.
[目的/意义]旨在分析协同搜索用户在信息搜索任务过程中的交流内容与模式,从而理解协同搜索用户的关注重点与搜索过程。[研究设计/方法]基于书籍交互检索平台(CLEF-Social Book Search)设计实验,共招募18名被试完成两种搜索任务,通过录音记录对话并对其进行编码和分析,总结交流内容特征和模式。结合任务类型、认知类型组合、服务器记录的搜索交互行为日志以及问卷收集的搜索体验进行了探索分析。[结论/发现]从交流内容上看,协同搜索用户主要理解与评判书目信息、商讨搜索任务计划;比起认知类型不同的用户,相同认知类型的用户在操作交互方面交流更多,在评判决策方面交流较少。交流模式依据讨论内容比重可分为理解评判型、评判主导型、均衡交流型三种,评判主导型用户的任务完成满意度最高。[创新/价值]协同搜索用户的交流反映出搜索过程中需要与同伴商讨协同的焦点,也是需要系统提供协助的重点,给协同搜索系统设计提供一定参考。本研究针对协同搜索的交流内容设计的编码系统对相关的协同交流研究也有借鉴意义。  相似文献   
105.
106.
Young children show social preferences for resource-rich individuals, although few studies have explored the causes underlying such preferences. We evaluate the viability of one candidate cause: Children believe that resource wealth relates to behavior, such that they expect the resource rich to be more likely to materially benefit others (including themselves) than the resource poor. In Studies 1 and 2 (ages 4–10), American children from predominantly middle-income families (= 94) and Indian children from lower income families (= 30) predicted that the resource rich would be likelier to share with others than the resource poor. In Study 3, American children (= 66) made similar predictions in an incentivized decision-making task. The possibility that children's expectations regarding giving contribute to prowealth preferences is discussed.  相似文献   
107.
Although there has been a great deal of research into Collaborative Information Retrieval (CIR) and Collaborative Information Seeking (CIS), the majority has assumed that team members have the same level of unrestricted access to underlying information. However, observations from different domains (e.g. healthcare, business, etc.) have suggested that collaboration sometimes involves people with differing levels of access to underlying information. This type of scenario has been referred to as Multi-Level Collaborative Information Retrieval (MLCIR). To the best of our knowledge, no studies have been conducted to investigate the effect of awareness, an existing CIR/CIS concept, on MLCIR. To address this gap in current knowledge, we conducted two separate user studies using a total of 5 different collaborative search interfaces and 3 information access scenarios. A number of Information Retrieval (IR), CIS and CIR evaluation metrics, as well as questionnaires were used to compare the interfaces. Design interviews were also conducted after evaluations to obtain qualitative feedback from participants. Results suggested that query properties such as time spent on query, query popularity and query effectiveness could allow users to obtain information about team's search performance and implicitly suggest better queries without disclosing sensitive data. Besides, having access to a history of intersecting viewed, relevant and bookmarked documents could provide similar positive effect as query properties. Also, it was found that being able to easily identify different team members and their actions is important for users in MLCIR. Based on our findings, we provide important design recommendations to help develop new CIR and MLCIR interfaces.  相似文献   
108.
[目的/意义] 提升公民健康水平是经济社会发展到一定程度后的必然要求,健康数据协同治理体系的构建有助于从信息科学角度达成这一要求,治理体系需要以国家战略为宏观指导,全方位服务于公民健康水平提升的总体目标。[方法/过程] 通过对《"健康中国2030"规划纲要》文本精神的领会,在分析了各治理主体对健康信息治理需求的基础上,提出一种面向"健康中国2030"战略的健康数据协同治理体系,并针对关键环节提出保障措施。[结果/结论] 协调各层级、各部门与各利益主体的健康数据治理体系构建与保障,有助于在推动国家健康战略目标的同时实现健康数据的社会价值,拓展健康信息学的研究范畴。  相似文献   
109.
目的:了解不同性别乒乓球运动员完成并步、跳步、跨步3种常用步法时膝关节的负荷特征,并探析乒乓球运动员膝关节的损伤机制。方法:对乒乓球男、女各10名运动员完成3种常用步法动作时的下肢运动学、动力学数据进行采集和处理,并运用方差分析法比较不同性别、不同技术之间的差异。结果:受试者在完成3种步法过程中,膝关节屈角大致范围在20°~60°。当地面反作用力最大时,女运动员比男运动员表现出更小的外展角(P<0.05),跳步比并步和跨步表现出更小的外展角(P<0.05);在三维受力方面,膝关节受到垂直方向上的力最大,水平向后和向左的力次之,未表现出显著的性别差异和技术差异;在三维力矩方面,膝关节受到的伸膝力矩较大,也未表现出显著的性别差异和技术差异。结论:膝关节屈曲状态下,较大的地面反作用力和膝关节外展角易导致乒乓球运动员前交叉韧带损伤,女运动员的损伤风险小于男运动员,跳步的损伤风险小于并步和跨步;水平向后和向左的力易造成乒乓球运动员软骨和半月板损伤;过大的伸膝力矩易导致乒乓球运动员髌腱末端病和髌骨软化。  相似文献   
110.
Abstract

This paper provides a methodology to study the characteristics of the research output from a university department. The faculty publications and their cited references over a 10-year period were used as the basis for this study to identify their publishing patterns and the types of material they are publishing; a core set of journals and other resources they are publishing in and citing over this period; the characteristics of the journals in which they publish and cite; the degree of openness of their publications and their citation advantage; and the age of resources that are referenced.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号