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   1133篇
  免费   34篇
  国内免费   2篇
  2024年   2篇
  2022年   6篇
  2021年   20篇
  2020年   8篇
  2019年   15篇
  2018年   10篇
  2017年   19篇
  2016年   21篇
  2015年   37篇
  2014年   41篇
  2013年   77篇
  2012年   69篇
  2011年   80篇
  2010年   43篇
  2009年   34篇
  2008年   72篇
  2007年   57篇
  2006年   77篇
  2005年   63篇
  2004年   76篇
  2003年   86篇
  2002年   76篇
  2001年   10篇
  2000年   7篇
  1999年   7篇
  1998年   18篇
  1997年   12篇
  1996年   16篇
  1995年   17篇
  1994年   9篇
  1993年   7篇
  1992年   8篇
  1991年   6篇
  1990年   4篇
  1989年   4篇
  1988年   9篇
  1987年   4篇
  1985年   2篇
  1984年   5篇
  1983年   6篇
  1982年   8篇
  1981年   4篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1974年   3篇
  1959年   1篇
排序方式: 共有1169条查询结果,搜索用时 62 毫秒
11.
We have cloned a new Dlx gene (Dlx7) from human and mouse that may represent the mammalian orthologue of the newt geneNvHBox-5.The homeodomains of these genes are highly similar to all other vertebrate Dlx genes, and regions of similarity also exist between mammalian Dlx7 and a subset of vertebrate Dlx genes downstream of the homeodomain. The sequence divergence between human and mouse Dlx7 in these regions is greater than that predicted from comparisons of other vertebrate Dlx genes, however, and there is little sequence similarity upstream of the homeodomain both between these two genes and with other Dlx genes. We present evidence for alternative splicing of mouseDlx7upstream of the homeodomain that may account for some of this divergence. We have mapped humanDLX7distal to the 5′ end of the HOXB cluster at an estimated distance of between 1 and 2 Mb by FISH. Both the human and the mouse Dlx7 are shown to be closely linked to Dlx3 in a convergently transcribed orientation. These mapping results support the possibility that vertebrate distal-less genes have been duplicated in concert with the Hox clusters.  相似文献   
12.
13.
14.
Abstract: Among various tissues of mouse, β1,4- N -acetylgalactosaminyltransferase (GM2/GD2 synthase) gene is expressed predominantly in the brain. Further analysis of the gene expression in the mouse CNS was performed by northern blotting and by enzyme assays using extracts from various parts of the CNS. In situ hybridization was also done to investigate the distribution of cells generating GM2/GD2 synthase. In northern blots, diverse levels of the gene expression were observed, depending on the regions examined. By in situ hybridization, pyramidal cells in the hippocampus, granular cells in dentate gyrus and cerebral cortex, Purkinje cells in cerebellum, and mitral cells in the olfactory bulb expressed high levels of the mRNA; these results corresponded to the results obtained by northern blot. Enzyme levels in these sites were accordingly high. However, enzyme levels in certain areas with low mRNA intensities, such as thalamus and pons medulla, were higher than expected from the results of northern blotting. The significance of the high gene expression in certain areas for brain function and the reason for the discrepancy between mRNA level and enzyme activity in some regions are discussed.  相似文献   
15.
16.
17.
18.
The regular surface layer of a strain of a Comamonas-like organism was examined by electron microscopy. The surface layer protein was easily extracted from the cell surface by a 2.5 M solution of lithium chloride. The protein subunit has a molecular size of 32,000 daltons, but usually forms a large aggregate of more than 1,200,000 daltons. In the extract it formed a regular array of p4 symmetry and was observed to be intimately associated with fragments of lipopolysaccharide. The size of a subunit determined by the negative staining method and the image processing method measured 5.2 × 6.4 nm (width and length), was arranged in a cobblestone-like pattern, and was located in a lattice space measuring 13.0 nm square.  相似文献   
19.
ADP-stimulated aggregation of bovine blood platelets was observed in media containing isotonic potassium salts of various monovalent anions. The aggregation depended on the anion in the medium, the order of aggregation being Cl?, Br?>I?>SCN?, ClO4?. After 30-min incubation, the extent of aggregation of platelets in Cl? or Br? medium was little changed, whereas, that in SCN? or ClO4? medium was remarkably decreased. This anion dependency of aggregation may be due to change in the membrane potential.  相似文献   
20.
Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion-exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross-reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemically visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M(r) of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M(r) of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50-kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor-stimulated astroblasts, but not neuronal cells.  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