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   85117篇
  免费   7304篇
  国内免费   5846篇
  2023年   875篇
  2022年   1006篇
  2021年   3754篇
  2020年   2568篇
  2019年   3122篇
  2018年   3121篇
  2017年   2245篇
  2016年   3141篇
  2015年   5019篇
  2014年   5807篇
  2013年   6499篇
  2012年   7630篇
  2011年   7045篇
  2010年   4273篇
  2009年   3824篇
  2008年   4616篇
  2007年   4102篇
  2006年   3545篇
  2005年   3058篇
  2004年   2570篇
  2003年   2243篇
  2002年   1999篇
  2001年   1714篇
  2000年   1722篇
  1999年   1559篇
  1998年   950篇
  1997年   859篇
  1996年   856篇
  1995年   808篇
  1994年   750篇
  1993年   577篇
  1992年   876篇
  1991年   703篇
  1990年   650篇
  1989年   571篇
  1988年   464篇
  1987年   395篇
  1986年   366篇
  1985年   331篇
  1984年   252篇
  1983年   221篇
  1982年   138篇
  1981年   136篇
  1980年   100篇
  1979年   165篇
  1978年   94篇
  1977年   111篇
  1976年   89篇
  1975年   119篇
  1974年   132篇
排序方式: 共有10000条查询结果,搜索用时 38 毫秒
11.
12.
13.
A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships.  相似文献   
14.
The genome of Mus domesticus has multiple genes of the alpha 1-acid glycoprotein (AGP). Two cDNA clones were identified corresponding to AGP-1 and AGP-2. Moreover, two alleles of AGP-1 exist in inbred mice. The genomic DNA of the AGP-2 gene has been cloned and studied. Here we report the genomic organization of three M. domesticus AGP genes, the sequence analysis of the AGP-3 genomic DNA, and the expression of the AGP-3 gene. The major structural differences between AGP-2 and AGP-3 genes are located in introns 1 and 5. The low level of AGP-3 mRNA can be detected by the polymerase chain reaction (PCR). The molecular basis of the low level expression of AGP-3 and the possible classification of AGP-3 as a pseudogene are discussed.  相似文献   
15.
Recent studies have revealed an unexpected synergism between two seemingly unrelated protein families: CCN matricellular proteins and the tumor necrosis factor (TNF) family of cytokines. CCN proteins are dynamically expressed at sites of injury repair and inflammation, where TNF cytokines are also expressed. Although TNFα is an apoptotic inducer in some cancer cells, it activates NFκB to promote survival and proliferation in normal cells, and its cytotoxicity requires inhibition of de novo protein synthesis or NFκB signaling. The presence of CCN1, CCN2, or CCN3 overrides this requirement and unmasks the apoptotic potential of TNFα, thus converting TNFα from a proliferation-promoting protein into an apoptotic inducer. These CCN proteins also enhance the cytotoxicity of other TNF cytokines, including LTα, FasL, and TRAIL. Mechanistically, CCNs function through integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4 to induce reactive oxygen species (ROS) accumulation, which is essential for apoptotic synergism. Mutant CCN1 proteins defective for binding α6β1-HSPGs are unable to induce ROS or apoptotic synergism with TNF cytokines. Further, knockin mice that express an α6β1-HSPG-binding defective CCN1 are blunted in TNFα- and Fas-mediated apoptosis, indicating that CCN1 is a physiologic regulator of these processes. These findings implicate CCN proteins as contextual regulators of the inflammatory response by dictating or enhancing the cytotoxicity of TNFα and related cytokines.  相似文献   
16.
17.
18.
19.
20.
  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