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   70600篇
  免费   5980篇
  国内免费   63篇
  2022年   646篇
  2021年   1202篇
  2020年   655篇
  2019年   882篇
  2018年   1323篇
  2017年   1024篇
  2016年   1851篇
  2015年   3043篇
  2014年   3404篇
  2013年   4069篇
  2012年   5255篇
  2011年   5074篇
  2010年   3240篇
  2009年   2920篇
  2008年   4133篇
  2007年   3909篇
  2006年   3626篇
  2005年   3357篇
  2004年   3334篇
  2003年   3069篇
  2002年   2767篇
  2001年   1829篇
  2000年   1643篇
  1999年   1378篇
  1998年   754篇
  1997年   638篇
  1996年   527篇
  1995年   517篇
  1994年   435篇
  1993年   457篇
  1992年   750篇
  1991年   632篇
  1990年   586篇
  1989年   564篇
  1988年   504篇
  1987年   490篇
  1986年   407篇
  1985年   456篇
  1984年   379篇
  1983年   336篇
  1982年   322篇
  1981年   303篇
  1980年   277篇
  1979年   295篇
  1978年   291篇
  1977年   268篇
  1976年   251篇
  1975年   206篇
  1974年   295篇
  1973年   232篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The reported selective serotonin Re-uptake Inhibitor Litoxetine was used as the starting point in the design of a range of potential SSRIs with high ease of synthetic accessibility. Preparation and subsequent optimization yielded a range of potent and highly selective SSRIs.  相似文献   
92.
Rapid and reproducible method is described here for the purification of the 43 kDa fimbrial protein from P. gingivalis by preferential fractionation in the presence of 1% SDS and 0.2M of a bivalent cation at pH 6.5. Homogeneity of the purified 43 kDa was confirmed by SDS-PAGE and Western blot analysis using monoclonal and polyclonal antibodies raised against this protein. Amino acid composition and the amino acid sequence of the first 30 amino acid residues of the purified fimbriae are consistent with the composition and sequence predicted from the cloned gene of the fimbrial subunit. Circular dichroism spectra shows high levels of beta-sheet structure. The purified 43 kDa polymer shows fimbriae-like morphology under the electron microscope. Ultrastructural localization of the 43 kDa protein by the immunogold technique revealed specific labeling of the fimbriae with a diameter of approximately 3.5 to 5.0 nm. Localization of this protein suggest that the 43 kDa component is a fimbrial subunit.  相似文献   
93.
Avian oviductal fluids contain phosphorylating-dephosphorylating enzymes that might function in sperm-oocyte interactions. Phosphorprotein phosphatase and protein kinase have been purified 20-fold and 40-fold, respectively. The latter easily aggregates and is highly labile. Other properties are comparable to those of holoenzymes.  相似文献   
94.
95.
96.
97.
One of the leading challenges for contemporary anthropology is to try to contribute to an understanding of the interaction between indigenous and exogenous socio‐cultural orders, especially at the frontiers of globalisation. Here I review three recent attempts to do so: (1) a model of structural transformation as developed by Marshall Sahlins; (2) a model of articulation as developed by James Clifford; (3) a model of ‘adoption’ proposed by Joel Robbins. As a test case for these models, I consider them in relation to some recent developments in local segmentary politics and verbal art in the Ku Waru region of Highland New Guinea. I show that all three models are in certain respects inadequate for understanding those developments, and offer some proposals as to what kinds of theory might be more adequate to the task.  相似文献   
98.
When expressed in Escherichia coli, a truncated form of phytochrome (oat PHYA AP3 residues 464-1129) self associates to form a series of products ranging in size from monomers to aggregates of greater than 20 subunits. When these same phytochrome sequences are coexpressed with the chaperonins GroEL and GroES, the truncated phytochrome migrates as a native-like dimer in size exclusion chromatography and no higher-order aggregates were detected. GroEL and GroES inhibition of phytochrome aggregation in E. coli presumably occurs via the suppression of folding pathways leading to incorrectly folded phytochrome.  相似文献   
99.
100.
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