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   128882篇
  免费   5227篇
  国内免费   65篇
  2021年   916篇
  2020年   613篇
  2019年   693篇
  2018年   1902篇
  2017年   1952篇
  2016年   4209篇
  2015年   8375篇
  2014年   8288篇
  2013年   8352篇
  2012年   8488篇
  2011年   5603篇
  2010年   4362篇
  2009年   4121篇
  2008年   3480篇
  2007年   3317篇
  2006年   2993篇
  2005年   8809篇
  2004年   7322篇
  2003年   5285篇
  2002年   2644篇
  2001年   2369篇
  2000年   1530篇
  1999年   2439篇
  1998年   709篇
  1997年   497篇
  1992年   2239篇
  1991年   2301篇
  1990年   2332篇
  1989年   2221篇
  1988年   2122篇
  1987年   1972篇
  1986年   1753篇
  1985年   1756篇
  1984年   1163篇
  1983年   915篇
  1982年   520篇
  1979年   1142篇
  1978年   810篇
  1977年   656篇
  1976年   672篇
  1975年   914篇
  1974年   1057篇
  1973年   1046篇
  1972年   984篇
  1971年   962篇
  1970年   845篇
  1969年   868篇
  1968年   757篇
  1967年   773篇
  1966年   602篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
The present study has shown that on the level of the parasitic system the epidemic process is a biological system, wherein the host population serves as the internal regulator, the mechanism of transmission serves as the external regulator and the parasite population, as the regulated object. The biological regulating mechanisms of the epidemic process have fundamental differences in the groups of infectious with various mechanisms of transmission, and the specific nature of the mechanism of transmission determines the peculiar features of the biological mechanism which governs the self-regulation of the epidemic process. In contrast, on a higher level of the organization of the epidemic process, i. e. on the level of the socio-ecological system, the epidemic process is a biosocial system, wherein the human society serves as the regulator, the parasitic system serves as the regulated object and the mechanism of transmission plays the role of the filter which determines the scope of social factors, most important in the regulation of the epidemic process in a given infection. The spontaneous regulation of the epidemic process is the freed forward channel from the regulator to the regulated object, and the controlled regulation is the feedback channel.  相似文献   
82.
Rabbit antiserum produced against rat liver cytochrome H-450 was specific for cytochrome H-450. The antiserum did not react with hemolysate, microsomal and mitochondrial fractions of liver, and tissue extracts from heart, lung skeletal muscle, and testis of rat. With the monospecific antiserum, a rocket immunoelectrophoretic assay method was developed for the quantitation of the antigen with a sensitivity of 25 ng. By using rocket immunoelectrophoresis, the total amounts of the antigen found in liver, kidney, and brain of 20 rats were 33.6, 3.6, and 1.3 mg, respectively. It appears that the antigens in liver, kidney, and brain are immunologically identical. From immunological studies with subcellular fractions of rat liver, the antigen was found only in the postmicrosomal fraction. This indicates that the antigen is not a precursor or a proteolytic product of known cytochromes in mitochondria or microsomes. Therefore, cytochrome H-450 is a unique cytosolic protein found in brain, kidney, and liver.  相似文献   
83.
84.
85.
Protoplasts of Schizosaccharomyces pombe, grown on a rich nutrient medium, were treated with a peptide factor isolated from cultures of the protozoan Tetrahymena pyriformis. The peptide factor is known to inhibit RNA synthesis in Tetrahymena. It has now been shown that the peptide factor also inhibits RNA synthesis in yeast protoplasts without affecting protein synthesis.  相似文献   
86.
87.
88.
89.
90.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells.  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