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   44626篇
  免费   3839篇
  国内免费   4477篇
  2024年   34篇
  2023年   606篇
  2022年   812篇
  2021年   2400篇
  2020年   1711篇
  2019年   2241篇
  2018年   2024篇
  2017年   1470篇
  2016年   2027篇
  2015年   2976篇
  2014年   3510篇
  2013年   3737篇
  2012年   4270篇
  2011年   3833篇
  2010年   2421篇
  2009年   2238篇
  2008年   2569篇
  2007年   2263篇
  2006年   1915篇
  2005年   1527篇
  2004年   1288篇
  2003年   1228篇
  2002年   957篇
  2001年   686篇
  2000年   643篇
  1999年   591篇
  1998年   403篇
  1997年   334篇
  1996年   320篇
  1995年   283篇
  1994年   291篇
  1993年   187篇
  1992年   239篇
  1991年   204篇
  1990年   145篇
  1989年   114篇
  1988年   89篇
  1987年   92篇
  1986年   49篇
  1985年   55篇
  1984年   32篇
  1983年   39篇
  1982年   22篇
  1981年   25篇
  1980年   8篇
  1979年   10篇
  1976年   3篇
  1973年   3篇
  1972年   4篇
  1965年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Plant somatic cells have the capability to switch their cell fates from differentiated to undifferentiated status under proper culture conditions, which is designated as totipotency. As a result, plant cells can easily regenerate new tissues or organs from a wide variety of explants. However, the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown. In this study, we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro. Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.  相似文献   
2.
3.
It has been demonstrated that caleosin alone is sufficient to stabilize artificial oil bodies. A series of recombinant caleosins, mutated with 3, 5, 8, 11, 13, 15, and 17 extra Lys residues and over‐expressed in Escherichia coli, were used as carrier proteins to render biotin as a hapten on the surface of artificial oil bodies for antibody production. Biotinylation levels of the recombinant caleosins were step‐wisely elevated as the number of extra Lys residues increased, and the biotinylated Lys residues were identified by mass spectrometric analysis. Polyclonal antibodies against biotin were successfully generated in rats injected with artificial oil bodies constituted with each of the biotinylated caleosins. Moreover, those generated via the biotinylated caleosins with eight or more extra Lys residues no longer recognized caleosin. It appears that engineered Lys‐rich caleosins are suitable carrier proteins for the production of antibodies against small molecules. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011  相似文献   
4.
The functioning of the vertebrate eye depends on its absolute size, which is presumably adapted to specific needs. Eye size variation in lidless and spectacled colubrid snakes was investigated, including 839 specimens belonging to 49 genera, 66 species and subspecies. Variations of adult eye diameters (EDs) in both absolute and relative terms between species were correlated with parameters reflecting behavioral ecology. In absolute terms, eye of arboreal species was larger than in terrestrial and semiaquatic species. For diurnal species, EDs of terrestrial species do not differ from semiaquatic species; for nocturnal species the ED of terrestrial species is larger than fossorial species but not different from semiaquatic species. In relative terms, ED did not differ significantly by habitat for diurnal species. Although the ED of terrestrial species is larger than fossorial species there were no differences for nocturnal species between semiaquatic and fossorial snakes. In contrast to other vertebrates studied to date, colubrid EDs in absolute and relative terms are larger in diurnal than in nocturnal species. These observations suggest that among colubrid snakes, eye size variation reflects adaptation to specific habitats, foraging strategies and daily activities, independently of phylogeny. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
5.
6.
7.
8.
  相似文献   
9.
10.
Liu  Rui-zhu  Li  Tao  Zhao  Guo-qing 《Neurochemical research》2019,44(5):1090-1100
Neurochemical Research - Inhalation anesthetic isoflurane may cause an increased risk of cognitive impairment. Previous studies have indicated that this cognitive decline is associated with...  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