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   25481篇
  免费   235篇
  国内免费   19篇
教育   17448篇
科学研究   2728篇
各国文化   200篇
体育   2126篇
综合类   25篇
文化理论   252篇
信息传播   2956篇
  2021年   200篇
  2020年   331篇
  2019年   469篇
  2018年   1217篇
  2017年   1245篇
  2016年   1024篇
  2015年   429篇
  2014年   580篇
  2013年   3907篇
  2012年   530篇
  2011年   801篇
  2010年   676篇
  2009年   579篇
  2008年   643篇
  2007年   690篇
  2006年   395篇
  2005年   436篇
  2004年   747篇
  2003年   550篇
  2002年   529篇
  2001年   417篇
  2000年   438篇
  1999年   360篇
  1998年   189篇
  1997年   255篇
  1996年   251篇
  1995年   209篇
  1994年   221篇
  1993年   189篇
  1992年   330篇
  1991年   298篇
  1990年   269篇
  1989年   339篇
  1988年   293篇
  1987年   298篇
  1986年   277篇
  1985年   325篇
  1984年   263篇
  1983年   252篇
  1982年   209篇
  1981年   196篇
  1980年   168篇
  1979年   270篇
  1978年   200篇
  1977年   181篇
  1976年   191篇
  1975年   149篇
  1974年   175篇
  1973年   148篇
  1971年   142篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
Acquiring both published and unpublished documents produced in Africa is, generally, a difficult task due to the existing poor state of bibliographic control and the publishing industry. It is even more difficult to obtain unpublished documents in a specialized area of study such as demography--a diffuse area which cuts across several disciplines. This paper discusses the problems encountered on acquisition trips to some African countries to acquire unpublished population material. To help solve the problems, the Population Association of Africa must persuade its members to send copies of their publications to population libraries and documentation centers in their individual countries for dissemination to the other users in Africa. The various organizations and institutions in Africa engaged in the teaching and research of population studies should have an agreement to exchange copies of their theses. The Economic Commission for Africa (ECA) and the Organization of African Unity (OAU) should make representations to the various African member countries on the need to disseminate the results of vital censuses and surveys conducted. Finally, the Population Information Network for Africa (POPIN-AFRICA) with its coordinating unit at the population division of ECA should ensure that all the nodes of the network have the financial and other resources to be able to acquire the relevant documents needed for their operations.  相似文献   
54.
The National Library of Medicine has had an enormous impact on health information services all over the world. Although NLM is primarily a national institution, it has become an important international resource by responding to requests from the international community. NLM has been influential in three major ways. First, NLM has provided a model for other national and regional health information services. Second, it has been a catalyst, in that MEDLARS and other services it provides formed the nucleus of many regional networks. NLM helped such networks get started by giving advice on how to set up services and build collections and by "training the trainers" on the MEDLARS system. Third, NLM has supported national and regional operations by providing the additional training and materials needed for day-to-day service.  相似文献   
55.
56.
57.
58.
59.
60.
This study, an historical survey of medical journals in Louisiana before the outbreak of the Civil War in 1861, revealed that nine journals made an appearance during the period covered-all of them published in New Orleans. Of these, two were French language journals published by a French medical society. The others were all published by individuals rather than by professional societies. Medical practices, interests, and problems of the times were clearly reflected on the pages of the journals. It is evident that medical journalism reached a high plane in the era before the Civil War. Of the nine periodicals, only one emerged as a permanent publication after the War.  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