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   17564篇
  免费   248篇
  国内免费   8篇
教育   12852篇
科学研究   1435篇
各国文化   126篇
体育   1567篇
综合类   9篇
文化理论   165篇
信息传播   1666篇
  2022年   114篇
  2021年   194篇
  2020年   308篇
  2019年   505篇
  2018年   646篇
  2017年   655篇
  2016年   568篇
  2015年   370篇
  2014年   450篇
  2013年   3379篇
  2012年   443篇
  2011年   457篇
  2010年   306篇
  2009年   284篇
  2008年   405篇
  2007年   301篇
  2006年   368篇
  2005年   250篇
  2004年   220篇
  2003年   214篇
  2002年   256篇
  2001年   346篇
  2000年   312篇
  1999年   277篇
  1998年   149篇
  1997年   171篇
  1996年   193篇
  1995年   197篇
  1994年   158篇
  1993年   177篇
  1992年   250篇
  1991年   225篇
  1990年   223篇
  1989年   254篇
  1988年   255篇
  1987年   212篇
  1986年   209篇
  1985年   222篇
  1984年   195篇
  1983年   234篇
  1982年   175篇
  1981年   165篇
  1980年   161篇
  1979年   236篇
  1978年   186篇
  1977年   172篇
  1976年   155篇
  1975年   127篇
  1974年   115篇
  1973年   124篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
This study examines how social comparison information provided by video game leaderboards may influence players’ retrospective judgments of autonomy, competence, and relatedness need fulfillment. Participants played a video game and were randomly assigned to receive no postgame feedback or were shown a leaderboard that placed them in the top or bottom quartile of players. Results indicate downward social comparisons increase enjoyment by increasing competence and relatedness perceptions. However, upward comparisons did not have an opposite effect, nor did either type of social comparison influence players’ autonomy perceptions. Implications for applying Self-Determination Theory to video game enjoyment in the context of social comparison feedback is discussed.  相似文献   
72.
This study extends instructional communication research on extra-class communication (ECC) by presenting an integrative analysis comparing the explanatory utility of student- and instructor-oriented reasons for student engagement in frequent ECC. Results from 495 college students suggested that student-oriented reasons, specifically the relational and functional student motives, were the only significant, positive predictors of students’ perceptions of frequent ECC engagement. Other student motives (excuse making, participation, sycophancy) and perceptions of instructor approachability did not significantly predict perceived frequency of ECC engagement.  相似文献   
73.
Automatic detection of source code plagiarism is an important research field for both the commercial software industry and within the research community. Existing methods of plagiarism detection primarily involve exhaustive pairwise document comparison, which does not scale well for large software collections. To achieve scalability, we approach the problem from an information retrieval (IR) perspective. We retrieve a ranked list of candidate documents in response to a pseudo-query representation constructed from each source code document in the collection. The challenge in source code document retrieval is that the standard bag-of-words (BoW) representation model for such documents is likely to result in many false positives being retrieved, because of the use of identical programming language specific constructs and keywords. To address this problem, we make use of an abstract syntax tree (AST) representation of the source code documents. While the IR approach is efficient, it is essentially unsupervised in nature. To further improve its effectiveness, we apply a supervised classifier (pre-trained with features extracted from sample plagiarized source code pairs) on the top ranked retrieved documents. We report experiments on the SOCO-2014 dataset comprising 12K Java source files with almost 1M lines of code. Our experiments confirm that the AST based approach produces significantly better retrieval effectiveness than a standard BoW representation, i.e., the AST based approach is able to identify a higher number of plagiarized source code documents at top ranks in response to a query source code document. The supervised classifier, trained on features extracted from sample plagiarized source code pairs, is shown to effectively filter and thus further improve the ranked list of retrieved candidate plagiarized documents.  相似文献   
74.
Libraries have been the key to preserving culture and historic legacy for centuries. One such treasure cataloged in The Pennsylvania State University (Penn State) Libraries is a collection of over 33,000 Sanborn? Fire Insurance Maps. Originally kept safe in metal drawers, the library has embarked on a journey to digitize this abundance of information, combine it with other media such as photographs, and make it accessible through a web interface. Inspired by these efforts, we accessed this information and took it to the next level. Using state of the art 3D modeling and immersive technologies, we created a historic 3D model and immersive experiences of Penn State, exemplarily for the 1922 campus. The resulting experiences can be accessed through the web but also through head mounted displays (HMDs) and mobile phones in combination with VR viewers such as the Google Cardboard. Additionally, they can be used anywhere in the world or on the campus itself as a way to enable remote and in situ experiences and learning. Immersive experiences let us connect to the past, the present and the future, and as such offer value to digital cultural heritage efforts.  相似文献   
75.
Against the backdrop of Spain’s Transparency Act, this article discusses the presence or otherwise of a series of document types, proposed as management-related transparency indicators, on 61 (8 national and 53 provincial) historic archive websites. Although examples of good practice were identified, the information provided was found to be scant, in particular as regards lines of action, organisational objectives and yearly reports. The information most commonly provided on the websites included the collection classification chart, service use regulations and citizen charters. The inference drawn was that archives, so intently focused on their role in the application of the Act by the organisations they serve, neglect their own administrative obligations in respect of its provisions. The recommendation is that as government-funded and subsidised public service institutions, historic archives should exercise transparency by furnishing the information stipulated in the Act on their websites.  相似文献   
76.
This study investigates the convergence of two bibliometric approaches to the measurement of interdisciplinary research: one based on analyzing disciplinary diversity in the reference list of publications, the other based on the disciplinary diversity of authors of publications. In particular we measure the variety, balance, disparity and integrated diversity index of, respectively, single-author, multi-author single-field, and multi-author multi-field publications. We find that, in general, the diversity of the reference list grows with the number of fields reflected in a paper’s authors’ list and, to a lesser extent, with the number of authors being equal the number of fields. Further, we find that when fields belonging to different disciplines are reflected in the authors’ list, the disparity in the reference list is higher than in the case of fields belonging to the same discipline. However, this general tendency varies across disciplines, and noticeable exceptions are found at individual paper level.  相似文献   
77.
We have studied the efficiency of research in the EU by a percentile-based citation approach that analyzes the distribution of country papers among the world papers. Going up in the citation scale, the frequency of papers from efficient countries increases while the frequency from inefficient countries decreases. In the percentile-based approach, this trend, which is uniform at any citation level, is measured by the ep index that equals the Ptop 1%/Ptop 10% ratio. By using the ep index we demonstrate that EU research on fast-evolving technological topics is less efficient than the world average and that the EU is far from being able to compete with the most advanced countries. The ep index also shows that the USA is well ahead of the EU in both fast- and slow-evolving technologies, which suggests that the advantage of the USA over the EU in innovation is due to low research efficiency in the EU. In accord with some previous studies, our results show that the European Commission’s ongoing claims about the excellence of EU research are based on a wrong diagnosis. The EU must focus its research policy on the improvement of its inefficient research. Otherwise, the future of Europeans is at risk.  相似文献   
78.
Self‐efficacy is a universal construct, but few validated measures exist for researchers in developing countries to use in assessing youths’ perceptions of their ability to achieve academic success. This study examined the cross‐cultural suitability and psychometric properties of an academic self‐efficacy scale (ASES) adapted for the Ghanaian context. ASES construct validity was assessed with a sample of 4,289 Ghanaian junior high‐school students and exploratory and confirmatory factor analysis. Invariance testing assessed the scale's measurement equivalence by gender and temporal stability of gender equivalence. The ASES is a valid, reliable one‐dimensional scale for assessing young Ghanaians’ perceptions of their academic capabilities, and it works equally well across genders. As adapted, ASES is a valid scale with utility for researchers examining predictors and effects of academic self‐efficacy. The ASES has important implications for decisions regarding investment in programs aimed at improving academic self‐efficacy of youth, both in sub‐Saharan Africa and the increasingly diverse American public schools.  相似文献   
79.
ABSTRACT

Participation in youth sport is positively associated with physical fitness and performance. The purpose of the current study was to examine if physical fitness measures during childhood and early adolescence predicted high school sport participation. Participants included youth in the Michigan State University Motor Performance Study. Measures consisted of the endurance shuttle run, Wells sit-and-reach, jump and reach, standing long jump, agility shuttle run and 30-yard dash. Individual, generalized estimating equation models were used to estimate the association between each measure and the odds of participating in high school sport. For both sexes, the endurance shuttle run and agility shuttle run were related to sport participation. For boys only, the long jump and 30-yard dash were also associated with sport participation. Better physical fitness and performance across several dimensions in childhood, including those related to motor skills, enhanced the likelihood of sport participation in high school.  相似文献   
80.
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