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   124235篇
  免费   1864篇
  国内免费   236篇
教育   86234篇
科学研究   13494篇
各国文化   1979篇
体育   9588篇
综合类   174篇
文化理论   1060篇
信息传播   13806篇
  2021年   943篇
  2020年   1655篇
  2019年   2554篇
  2018年   3075篇
  2017年   3354篇
  2016年   3386篇
  2015年   2302篇
  2014年   3169篇
  2013年   27222篇
  2012年   2396篇
  2011年   2760篇
  2010年   2367篇
  2009年   2624篇
  2008年   2420篇
  2007年   2141篇
  2006年   2370篇
  2005年   2356篇
  2004年   3042篇
  2003年   2354篇
  2002年   2161篇
  2001年   2053篇
  2000年   1759篇
  1999年   1636篇
  1998年   1461篇
  1997年   1526篇
  1996年   1693篇
  1995年   1459篇
  1994年   1467篇
  1993年   1468篇
  1992年   1552篇
  1991年   1464篇
  1990年   1448篇
  1989年   1402篇
  1988年   1242篇
  1987年   1162篇
  1986年   1197篇
  1985年   1470篇
  1984年   1322篇
  1983年   1308篇
  1982年   1271篇
  1981年   1183篇
  1980年   1180篇
  1979年   1324篇
  1978年   1242篇
  1977年   1129篇
  1976年   1020篇
  1975年   829篇
  1974年   842篇
  1973年   809篇
  1971年   658篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
The author contemplates the fate of Russian science in the light of the reforms that are going on today, and the requirements of bringing it into conformity with this country’s traditions as well as with international practices.  相似文献   
952.
Soybean accounts for more than half of the global production of oilseed and more than a quarter of the protein used globally for human food and animal feed. Soybean domestication involved parallel increases in seed size and oil content, and a concomitant decrease in protein content. However, science has not yet discovered whether these effects were due to selective pressure on a single gene or multiple genes. Here, re-sequencing data from >800 genotypes revealed a strong selection during soybean domestication on GmSWEET10a. The selection of GmSWEET10a conferred simultaneous increases in soybean-seed size and oil content as well as a reduction in the protein content. The result was validated using both near-isogenic lines carrying substitution of haplotype chromosomal segments and transgenic soybeans. Moreover, GmSWEET10b was found to be functionally redundant with its homologue GmSWEET10a and to be undergoing selection in current breeding, leading the the elite allele GmSWEET10b, a potential target for present-day soybean breeding. Both GmSWEET10a and GmSWEET10b were shown to transport sucrose and hexose, contributing to sugar allocation from seed coat to embryo, which consequently determines oil and protein contents and seed size in soybean. We conclude that past selection of optimal GmSWEET10a alleles drove the initial domestication of multiple soybean-seed traits and that targeted selection of the elite allele GmSWEET10b may further improve the yield and seed quality of modern soybean cultivars.  相似文献   
953.
ABSTRACT

Press credentialing practices are a vital, yet understudied site of scholarly research on journalistic norms and practices. Press credentialing not only structures internal professional hierarchies, but they also signify the boundaries of the journalistic field itself. This paper explores the legal and theoretical implications of press credentialing to cover the United States Congress, drawing on the concepts of boundary work and journalistic authority to demonstrate the material impact of the space between fields on professional legitimation in journalism. Using WorldNetDaily (WND) as a case study, I argue that the Standing Committee of Correspondents (SCC) occupies a hybrid boundary zone between the journalistic and political fields, generating a unique tension in First Amendment jurisprudence that places journalists in a paradoxical role as both the professional embodiments of free speech and its constitutional steward. The resulting jurisdictional conflict between the SCC and WND extends the relational model of journalistic authority by articulating how journalist-state relations can fundamentally augment the process of legitimation at its fuzzy boundaries. The relevance and implications for press credentialing practices in the digital age are discussed.  相似文献   
954.
955.
956.
957.
Emerging fathers experience a variety of stressors, including identity and role transitions, changes in their relationships, and challenges in developing caregiving skills. Increasing expectations for father involvement in childcare are emphasizing the importance of the father role, but social supports for new fathers remain scarce. Nineteen expectant and new fathers participated in a pilot 5-week group intervention aimed at improving stress coping and involvement attitudes using a combination of mindfulness practices and skill-building for parenting and partner communication. We administered surveys pre- and postintervention to assess efficacy in the areas of stress, depressive symptoms, father involvement attitudes, and mindfulness. Within-participant differences were compared across participants as well as examining individual reliable change. Results indicated initial reductions in stress and depressive symptoms and increases in the mindfulness constructs of nonjudgment and nonreactivity. No significant changes were found in father involvement attitudes. Perinatal intervention specific to fathers holds promise as an underexplored avenue for supporting families across the transition to parenthood.  相似文献   
958.
959.
Abstract

This article discusses the use of R programing language for executing a sentiment analysis of tweets pertaining to library topics. This discussion is situated within the literature of marketing and management sciences, which is employing methods of machine learning and business intelligence to make informed decision-making, and library administration, which has expressed great interest in social media engagement within its literature but has yet to adopt these types of analysis. Presented in this article is a sample code with instructions on how users may execute it within R to retrieve and analyze tweets relevant to library services. Two examples created using the code (analysis of top librarians’ tweets and analysis of posts about major book publishers) are used to demonstrate the functionality of the code. The code presented in this article may be used by libraries to analyze tweets about their library and library-related topics, which, in turn, may inform management and marketing design.  相似文献   
960.
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