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   316130篇
  免费   38138篇
  国内免费   202篇
  2016年   3315篇
  2015年   4752篇
  2014年   5497篇
  2013年   7892篇
  2012年   9460篇
  2011年   9456篇
  2010年   6309篇
  2009年   5713篇
  2008年   8553篇
  2007年   8772篇
  2006年   8313篇
  2005年   8211篇
  2004年   7906篇
  2003年   7966篇
  2002年   7602篇
  2001年   11830篇
  2000年   12025篇
  1999年   9650篇
  1998年   3851篇
  1997年   3955篇
  1996年   3980篇
  1995年   3709篇
  1994年   3666篇
  1993年   3671篇
  1992年   8389篇
  1991年   8191篇
  1990年   7980篇
  1989年   7900篇
  1988年   7461篇
  1987年   7390篇
  1986年   6858篇
  1985年   7015篇
  1984年   5914篇
  1983年   5318篇
  1982年   4318篇
  1981年   4181篇
  1980年   3755篇
  1979年   6135篇
  1978年   4818篇
  1977年   4603篇
  1976年   4388篇
  1975年   4723篇
  1974年   5200篇
  1973年   5092篇
  1972年   4703篇
  1971年   4255篇
  1970年   3767篇
  1969年   3787篇
  1968年   3369篇
  1967年   2916篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
151.
152.
153.
A synchronously pumped krypton ion dye laser fluorescence system is shown to provide tunable, polarized, subnanosecond pulses at high repetition rates, modest peak powers, and low energy. Such a source is uniquely suited to fluorescence investigations of biochemical mechanisms. Applications of this fluorescence excitation source to analysis, life-time determination, and depolarization effects are discussed.  相似文献   
154.
Study of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis.  相似文献   
155.
156.
A double antibody radioimmunoassay technique is described for the measurement of anti-zona antibodies in the peripheral plasma of marmosets actively immunized against intact cow zonae pellucidae. The method has been shown to be a reliable, repeatable indicator of antibody titer, enabling direct comparison of the response obtained between marmosets. This is the first report of a procedure describing the active immunization of a primate against zona antigens, and the first time a radioimmunoassay technique has been used to monitor profiles of anti-cow zona antibody production following active immunization. The method should prove to be a useful tool in the evaluation of zona antigens as agents for immunocontraception.  相似文献   
157.
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   
158.
159.
160.
C Schmelzer  M W Müller 《Cell》1987,51(5):753-762
Deletion or substitution of the branch A residue in group II intron bl1 significantly reduces splicing activity; yet, residual exon ligation is correct, and lariats have their branch points at the normal distance from the 3' end of the intron. Mutations in the sequence facing the branch point also allow residual lariat formation; however, free 3' exons are generated with false 5' termini, all of which are within a UCACA consensus sequence located upstream or downstream of the normal 3' splice site. These results indicate that both the conserved 3' splice site APy and the spatial arrangements in stem 6 are crucial for correct 3' splice site selection.  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