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   295680篇
  免费   36421篇
  国内免费   194篇
  2016年   2925篇
  2015年   4365篇
  2014年   5076篇
  2013年   7170篇
  2012年   8137篇
  2011年   8051篇
  2010年   5507篇
  2009年   5170篇
  2008年   7293篇
  2007年   7501篇
  2006年   7131篇
  2005年   7037篇
  2004年   6888篇
  2003年   6970篇
  2002年   6639篇
  2001年   11191篇
  2000年   11304篇
  1999年   9302篇
  1998年   3630篇
  1997年   3792篇
  1996年   3790篇
  1995年   3510篇
  1994年   3514篇
  1993年   3482篇
  1992年   8244篇
  1991年   8042篇
  1990年   7834篇
  1989年   7741篇
  1988年   7319篇
  1987年   7273篇
  1986年   6732篇
  1985年   6881篇
  1984年   5759篇
  1983年   5170篇
  1982年   4141篇
  1981年   3987篇
  1980年   3612篇
  1979年   5966篇
  1978年   4689篇
  1977年   4474篇
  1976年   4266篇
  1975年   4610篇
  1974年   5063篇
  1973年   4974篇
  1972年   4614篇
  1971年   4163篇
  1970年   3665篇
  1969年   3697篇
  1968年   3298篇
  1967年   2850篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
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   
152.
153.
154.
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   
155.
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   
156.
157.
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   
158.
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   
159.
160.
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