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   851004篇
  免费   91967篇
  国内免费   685篇
  2018年   8355篇
  2017年   7845篇
  2016年   11408篇
  2015年   15935篇
  2014年   18397篇
  2013年   25895篇
  2012年   29189篇
  2011年   29421篇
  2010年   19884篇
  2009年   17935篇
  2008年   25915篇
  2007年   26539篇
  2006年   25014篇
  2005年   24097篇
  2004年   23920篇
  2003年   22916篇
  2002年   22123篇
  2001年   39196篇
  2000年   39463篇
  1999年   31397篇
  1998年   11137篇
  1997年   11523篇
  1996年   10828篇
  1995年   10140篇
  1994年   9876篇
  1993年   9637篇
  1992年   25332篇
  1991年   24577篇
  1990年   23921篇
  1989年   23262篇
  1988年   21624篇
  1987年   20157篇
  1986年   18713篇
  1985年   18534篇
  1984年   15404篇
  1983年   12885篇
  1982年   9832篇
  1981年   8794篇
  1980年   8170篇
  1979年   13868篇
  1978年   10786篇
  1977年   9694篇
  1976年   8759篇
  1975年   9775篇
  1974年   10441篇
  1973年   10291篇
  1972年   9255篇
  1971年   8391篇
  1970年   7187篇
  1969年   6961篇
排序方式: 共有10000条查询结果,搜索用时 375 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