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   128858篇
  免费   1890篇
  国内免费   235篇
教育   89368篇
科学研究   13838篇
各国文化   2000篇
体育   10226篇
综合类   173篇
文化理论   1088篇
信息传播   14290篇
  2021年   987篇
  2020年   1701篇
  2019年   2628篇
  2018年   3283篇
  2017年   3518篇
  2016年   3521篇
  2015年   2345篇
  2014年   3196篇
  2013年   27384篇
  2012年   2559篇
  2011年   3009篇
  2010年   2466篇
  2009年   2659篇
  2008年   2544篇
  2007年   2316篇
  2006年   2480篇
  2005年   2491篇
  2004年   3177篇
  2003年   2467篇
  2002年   2266篇
  2001年   2250篇
  2000年   1930篇
  1999年   1756篇
  1998年   1480篇
  1997年   1554篇
  1996年   1715篇
  1995年   1472篇
  1994年   1482篇
  1993年   1480篇
  1992年   1646篇
  1991年   1539篇
  1990年   1531篇
  1989年   1519篇
  1988年   1327篇
  1987年   1273篇
  1986年   1309篇
  1985年   1569篇
  1984年   1383篇
  1983年   1370篇
  1982年   1317篇
  1981年   1217篇
  1980年   1195篇
  1979年   1416篇
  1978年   1273篇
  1977年   1149篇
  1976年   1045篇
  1975年   858篇
  1974年   883篇
  1973年   839篇
  1971年   707篇
排序方式: 共有10000条查询结果,搜索用时 853 毫秒
991.
992.
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   
993.
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   
994.
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   
995.
996.
997.
998.
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   
999.
1000.
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   
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