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   294394篇
  免费   36221篇
  国内免费   405篇
  331020篇
  2016年   2949篇
  2015年   4415篇
  2014年   5112篇
  2013年   7214篇
  2012年   8115篇
  2011年   8043篇
  2010年   5511篇
  2009年   5171篇
  2008年   7241篇
  2007年   7430篇
  2006年   7071篇
  2005年   6969篇
  2004年   6799篇
  2003年   6859篇
  2002年   6516篇
  2001年   11125篇
  2000年   11240篇
  1999年   9261篇
  1998年   3591篇
  1997年   3765篇
  1996年   3747篇
  1995年   3487篇
  1994年   3496篇
  1993年   3460篇
  1992年   8223篇
  1991年   8019篇
  1990年   7795篇
  1989年   7723篇
  1988年   7292篇
  1987年   7242篇
  1986年   6702篇
  1985年   6859篇
  1984年   5743篇
  1983年   5152篇
  1982年   4111篇
  1981年   3954篇
  1980年   3587篇
  1979年   5952篇
  1978年   4654篇
  1977年   4454篇
  1976年   4250篇
  1975年   4595篇
  1974年   5052篇
  1973年   4946篇
  1972年   4598篇
  1971年   4147篇
  1970年   3651篇
  1969年   3675篇
  1968年   3274篇
  1967年   2824篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
121.
122.
A 3-wk-old lamb died because of neurological disease. The predominant microscopic lesions were in the brain and spinal cord and consisted of nonsuppurative encephalomyelitis with severe gliosis throughout the gray and white matter. Immature and mature schizonts, 15.7 x 10.6 microns (8-30 x 6-18 microns), occurred in capillaries and were structurally similar to those of Sarcocystis tenella.  相似文献   
123.
124.
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   
125.
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   
126.
127.
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   
128.
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   
129.
130.
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