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   15136篇
  免费   28篇
  国内免费   47篇
系统科学   63篇
丛书文集   181篇
教育与普及   32篇
理论与方法论   73篇
现状及发展   6180篇
研究方法   786篇
综合类   7611篇
自然研究   285篇
  2013年   105篇
  2012年   264篇
  2011年   543篇
  2010年   105篇
  2008年   321篇
  2007年   304篇
  2006年   321篇
  2005年   329篇
  2004年   320篇
  2003年   280篇
  2002年   260篇
  2001年   458篇
  2000年   442篇
  1999年   310篇
  1992年   267篇
  1991年   197篇
  1990年   224篇
  1989年   219篇
  1988年   223篇
  1987年   218篇
  1986年   205篇
  1985年   293篇
  1984年   229篇
  1983年   158篇
  1982年   167篇
  1981年   152篇
  1980年   181篇
  1979年   418篇
  1978年   309篇
  1977年   307篇
  1976年   289篇
  1975年   323篇
  1974年   385篇
  1973年   363篇
  1972年   379篇
  1971年   434篇
  1970年   550篇
  1969年   462篇
  1968年   469篇
  1967年   431篇
  1966年   383篇
  1965年   285篇
  1964年   87篇
  1959年   169篇
  1958年   297篇
  1957年   199篇
  1956年   185篇
  1955年   150篇
  1954年   185篇
  1948年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
S M Juan  E L Segura  J J Cazzulo 《Experientia》1979,35(9):1139-1140
The purified NADP-linked glutamate dehydrogenase from Trypanosoma cruzi was strongly inhibited by silver nitrate. The inhibition was reversed by reduced glutathione, and was modified by the presence of the substrates during preincubation of the enzyme with the inhibitor.  相似文献   
892.
E Klinge  O Er?nk?  N O Sj?strand 《Experientia》1978,34(12):1624-1626
The penile artery of the bull contained significant amounts of acetylcholine, noradrenaline and dopamine, and its axon profiles contained either numerous small granular or agranular vesicles, as well as some large granular vesicles. In the dorsal metatarsal artery, only noradrenaline and dopamine were detectable, and the axon profiles observed contained numerous small granular vesicles. In the penile artery, the axons with small agranular vesicles, probably cholinergic axons, were in close contact with axons containing small granular vesicles. It is suggested that, in the penile artery of the bull, one of the functions of the cholinergic nerves is suppression of excitatory adrenergic neurotransmission.  相似文献   
893.
3 experimentally distinct transverse relaxation components of the water in frog sciatic nerve are obtained by Carr-Purcell-Meiboom-Gill technique. The relative weights of these components: approximately 29%; approximately 50%; approximately 21% fit well with water compartments in this tissue as revealed by previous methods.  相似文献   
894.
W Schmidt  E J?hnchen 《Experientia》1978,34(10):1323-1325
13 mammalian species are classified into 3 clearcut groups with respect to the stereospecific serum protein-binding of phenprocoumon: 2 groups showing opposed stereospecific binding characteristics and a 3rd group exhibiting no stereospecific binding. Structural differences in the albumin molecule account for these stereospecific differences in serum protein-binding.  相似文献   
895.
The presence of hydrocortisone in virus-infected cell cultures leads to enhancement of the syncytia forming ability of Newcastle disease virus and to production of vescicular stomatitis virus particles which loose their infectivity upon storage below 0 degrees C.  相似文献   
896.
Plasma membrane sheets prepared by zonal centrifugation of a premicrosomal pellet obtained from a rat liver homogenate are devoid of HCO-3-ATPase activity. Since the microsomal fraction is also lacking in this ATPase activity, it can be concluded that the HCO-3-ATPase is not involved in the secretion of HCO-3 into bile.  相似文献   
897.
Sterile cultures of Chlamydomonas reinhardi, WT+, were treated with Hg-203 at 25 degrees C to identify probably formed volatile mercury compounds. Experiments were performed with living and dead cells under aerobic or anaerobic conditions, respectively, and the mercury concentration was measured in the system algae/nutrient medium. We found a timerelated decrease of mercury concentration in the cell suspension and the cell-free nutrient medium due to a reduction of Hg++ to Hg0, probably caused by extracellular enzymes; monomethyl or dimethyl mercury could not be detected.  相似文献   
898.
Our results indicate that pig lymphocytes in culture complete their 1st division at 24 h. At 36 h there are 9% of cells in 2nd division. 3rd mitosis appears at 48 h; and at 72 h there are cells engaged in the 4th division.  相似文献   
899.
900.
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