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   31704篇
  免费   46篇
  国内免费   71篇
系统科学   171篇
丛书文集   718篇
教育与普及   81篇
理论与方法论   202篇
现状及发展   13578篇
研究方法   1376篇
综合类   15309篇
自然研究   386篇
  2013年   179篇
  2012年   432篇
  2011年   873篇
  2010年   188篇
  2008年   578篇
  2007年   569篇
  2006年   623篇
  2005年   615篇
  2004年   543篇
  2003年   591篇
  2002年   577篇
  2001年   987篇
  2000年   906篇
  1999年   602篇
  1992年   578篇
  1991年   469篇
  1990年   490篇
  1989年   490篇
  1988年   491篇
  1987年   502篇
  1986年   497篇
  1985年   601篇
  1984年   496篇
  1983年   406篇
  1982年   350篇
  1981年   340篇
  1980年   450篇
  1979年   967篇
  1978年   859篇
  1977年   849篇
  1976年   580篇
  1975年   634篇
  1974年   935篇
  1973年   789篇
  1972年   804篇
  1971年   1022篇
  1970年   1348篇
  1969年   1005篇
  1968年   949篇
  1967年   994篇
  1966年   831篇
  1965年   611篇
  1964年   151篇
  1959年   360篇
  1958年   523篇
  1957年   443篇
  1956年   366篇
  1955年   316篇
  1954年   363篇
  1948年   193篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
p63 is a p53 homologue required for limb and epidermal morphogenesis   总被引:100,自引:0,他引:100  
Mills AA  Zheng B  Wang XJ  Vogel H  Roop DR  Bradley A 《Nature》1999,398(6729):708-713
  相似文献   
992.
993.
994.
995.
NF-AT activation requires suppression of Crm1-dependent export by calcineurin   总被引:19,自引:0,他引:19  
Zhu J  McKeon F 《Nature》1999,398(6724):256-260
  相似文献   
996.
This article describes the first results from the recent revision to The ONS classification of local and health authorities of Great Britain to allow for boundary changes. For each local and health authority of Great Britain as at April 1999 it presents 'most similar' authorities as measured by a selection of 37 socioeconomic and demographic variables from the 1991 Census. These results will assist local and health authorities in identifying other appropriate authorities for comparative studies. A second article, to be published in Population Trends 99, will present the results of the analysis to identify groups of authorities in a hierarchy of new Clusters, Groups and Families for the revised classification.  相似文献   
997.
998.
The hypothalamus regulates diverse physiological functions, including the control of energy metabolism, circadian rhythms, stress and anxiety, sexual and reproductive behaviors. An overview of the most prevalent hypothalamus-enriched mRNAs revealed that this area of the brain specializes in producing intercellular signaling molecules. Two new secreted peptides derived from a single neuropeptide precursor, named hypocretins and orexins by two different groups, are synthesized in a small set of neurons in the perifornical area of the hypothalamus. Intracerebroventricular injection of the hypocretins/orexins increases food consumption in rats. Here we review recent progress in identifying the role of the hypocretins/orexins in the control of energy balance and in other physiological systems.  相似文献   
999.
Integrin antagonists   总被引:4,自引:0,他引:4  
Integrins are a family of cell surface glycoproteins that mediate numerous cell-cell and cell-matrix interactions and are involved in biological processes such as tissue morphogenesis, leukocyte recirculation and migration, wound healing, blood clotting and immune response. Aberrant cell adhesion has been implicated in the pathogenesis of several diseases, including a number of inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease and asthma, as well as cancer and coronary heart disease. As such integrins are seen as excellent targets for the development of therapeutic agents. This report begins with an examination of the structure of integrin molecules and their ligands and then goes on to review the current state of development of antiintegrin antagonists. Received 13 April 1999; received after revision 28 May 1999; accepted 28 May 1999  相似文献   
1000.
Immune responses to DNA vaccines   总被引:16,自引:0,他引:16  
DNA vaccines, based on plasmid vectors expressing an antigen under the control of a strong promoter, have been shown to induce protective immune responses to a number of pathogens, including viruses, bacteria and parasites. They have also displayed efficacy in treatment or prevention of cancer, allergic diseases and autoimmunity. Immunologically, DNA vaccines induce a full spectrum of immune responses that include cytolytic T cells, T helper cells and antibodies. The immune response to DNA vaccines can be enhanced by genetic engineering of the antigen to facilitate its presentation to B and T cells. Furthermore, the immune response can be modulated by genetic adjuvants in the form of vectors expressing biologically active determinants or by more traditional adjuvants that facilitate uptake of DNA into cells. The ease of genetic manipulation of DNA vaccines invites their use not only as vaccines but also as research tools for immunologists and microbiologists. Received 26 October 1998; received after revision 3 December 1998; accepted 3 December 1998  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