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   877449篇
  免费   93869篇
  国内免费   5227篇
  2021年   10160篇
  2019年   8190篇
  2018年   10694篇
  2017年   9343篇
  2016年   13472篇
  2015年   18842篇
  2014年   21932篇
  2013年   29316篇
  2012年   33029篇
  2011年   32601篇
  2010年   21699篇
  2009年   19730篇
  2008年   27169篇
  2007年   27382篇
  2006年   25559篇
  2005年   24244篇
  2004年   23760篇
  2003年   22585篇
  2002年   21593篇
  2001年   39179篇
  2000年   39386篇
  1999年   31477篇
  1998年   11290篇
  1997年   11796篇
  1996年   11118篇
  1995年   10386篇
  1994年   10055篇
  1993年   9672篇
  1992年   25218篇
  1991年   24388篇
  1990年   23759篇
  1989年   23030篇
  1988年   21349篇
  1987年   19951篇
  1986年   18445篇
  1985年   18292篇
  1984年   15136篇
  1983年   12651篇
  1982年   9576篇
  1981年   8535篇
  1980年   7976篇
  1979年   13529篇
  1978年   10515篇
  1977年   9452篇
  1976年   8560篇
  1975年   9514篇
  1974年   10157篇
  1973年   10054篇
  1972年   8972篇
  1971年   8185篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The effect of obesity on the connective tissue composition of skin was investigated in mice with goldthioglucose (GTG)-induced obesity. Four months after GTG treatment, the obese animals were sacrificed. Acid mucopolysaccharides, glycoproteins, collagen, and elastin were analyzed in the skin and compared to the controls. Total MPS in the skin from obese animals decreased, reflected mostly in hyaluronic acid. Chondroitin showed an increase over controls. The content of soluble glycoproteins varied; total carbohydrate and sialic acid of the glycoprotein tended to increase with obesity. Collagen and elastin both tended to decrease with obesity.  相似文献   
992.
993.
994.
995.
996.
997.
Power spectra and coherence function of EEG of various cortical areas of both hemispheres were analyzed in 9 patients with extremely protracted loss of consciousness. Five patients were in the state of posttraumatic apallic syndrome lasting for more than 4 years in one patient, and 4-9 months with successive lethal outcome in 4 patients. One patient for more than 2 years was in a state of areactivity to external signals. In 3 patients the process of recovery of consciousness and speech began in 1-2 months. At the apallic syndrome, only low-frequency EEG components were present in spectrograms, and the values of coherence function were sharply decreased. With recovering consciousness and speech, a gradual appearance of alpha-activity was observed as well as an increase of coherence values at the frequency of the alpha-rhythm. The recovery of intercentral EEG relations in the motor-verbal cortical area was shown to play a special role in further normalization of connections in the cerebral cortex.  相似文献   
998.
999.
1000.
Numerous clinical and epidemiological studies link enteroviruses such as the Coxsackie virus group with the autoimmune disease type 1 diabetes mellitus (DM). In addition, there are reports that patients with type 1 DM are characterized by skewing of TCR Vbeta chain selection among peripheral blood and intraislet T lymphocytes. To examine these issues, we analyzed TCR Vbeta chain-specific up-regulation of the early T cell activation marker, CD69, on CD4 T cells after incubation with Coxsackievirus B4 (CVB4) Ags. CD4 T cells bearing the Vbeta chains 2, 7, and 8 were the most frequently activated by CVB4. Up-regulation of CD69 by different TCR families was significantly more frequent in new onset type 1 DM patients (p = 0.04), 100% of whom (n = 8) showed activation of CD4 T cells bearing Vbeta8, compared with 50% of control subjects (n = 8; p = 0.04). T cell proliferation after incubation with CVB4 Ags required live, nonfixed APCs, suggesting that the selective expansion of CD4 T cells with particular Vbeta chains resulted from conventional antigen processing and presentation rather than superantigen activity. Heteroduplex analysis of TCR Vbeta chain usage after CVB4 stimulation indicated a relatively polyclonal, rather than oligo- or monoclonal response to viral Ags. These results provide evidence that new-onset patients with type 1 DM and healthy controls are primed against CVB4, and that CD4 T cell responses to the virus have a selective TCR Vbeta chain usage which is driven by viral Ags rather than a superantigen.  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