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   119822篇
  免费   8256篇
  国内免费   214篇
  128292篇
  2021年   1259篇
  2020年   1122篇
  2019年   1088篇
  2018年   2661篇
  2017年   2381篇
  2016年   3195篇
  2015年   4110篇
  2014年   4389篇
  2013年   5675篇
  2012年   6608篇
  2011年   5968篇
  2010年   3934篇
  2009年   3131篇
  2008年   4930篇
  2007年   4693篇
  2006年   4671篇
  2005年   3919篇
  2004年   3887篇
  2003年   3513篇
  2002年   3284篇
  2001年   4656篇
  2000年   4238篇
  1999年   3166篇
  1998年   1199篇
  1997年   954篇
  1996年   960篇
  1995年   832篇
  1992年   2145篇
  1991年   1950篇
  1990年   1853篇
  1989年   1874篇
  1988年   1620篇
  1987年   1636篇
  1986年   1436篇
  1985年   1479篇
  1984年   1136篇
  1983年   1016篇
  1979年   1236篇
  1978年   889篇
  1977年   857篇
  1975年   1017篇
  1974年   1140篇
  1973年   1105篇
  1972年   1069篇
  1971年   998篇
  1970年   1018篇
  1969年   1081篇
  1968年   950篇
  1967年   811篇
  1966年   829篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The ability of the yeastCandida lipolytica 4-1 to oxidize and utilize various pure aliphatic hydrocarbons occurring in gas oil was studied. It was found that the given strain ofCandida lipolytica oxidized n-alkanes without adaptation, starting with heptane, and utilized them for growth, starting with nonane. Isoalkanes with a single methyl group in the side chain were also oxidized and utilized for growth, but less than the corresponding n-alkanes. The site of the methyl group in the isoalkane chain influences its conversion to biomass. Branched chains at both ends of the isoalkane molecule prevent its utilization for growth ofCandida lipolytica. 1-olefines are also oxidized and utilized for growth, though less than the corresponding n-paraffins. Alkylaromatic hydrocarbons are oxidized from amylbenzene up to decylbenzene, which is utilized only slightly for growth of the yeast.  相似文献   
992.
993.
994.
995.
996.
997.
998.
Summary Exponential phase cultures ofE. coli 15 T- cells growing on glucosemineral medium were supplemented with 2 mM l-cysteine-HCl. The optical density, acid soluble SH (AS-SH) as well as the DNA, RNA, and protein synthesis of the cultures were examined during this treatment and after return to normal growth conditions. Similarly, the survival of cells irradiated by a standard X-ray dose in cysteine-free buffer was measured.The development of radioresistance during the cysteine treatment as well as the loss of this acquired radioresistance after return to normal growth conditions could be divided into two phases: a) an instantaneous and b) a slow change of radioresistance. Phase a seems to be related to the changes occurring in the AS-SH content of the bacteria, while phase b is apparently dependent on the alterations in the synthesis of macromolecules.This work was partly presented at the 6th Annual Meeting of the European Society for Radiation Biology, Interlaken 1968.  相似文献   
999.
Summary The morphology of postnatal differentiation of the Golgi apparatus, the nucleus, the perikaryon, and the dendrites was studied in Purkinje cells of the rat cerebellum for 30 days after birth using histochemical, histological, and electron microscopic methods.The Golgi apparatus during differentiation undergoes morphological and positional changes. From the 1st to 7th postnatal day, the Golgi apparatus is found in a supranuclear position, and is connected with the axes of differentiating primary dendrites by beam-like processes. From days 8 to 11 this connection disappears, and most of the Golgi apparatus assumes a lateronuclear and infranuclear position. After the 11th or 12th day, the Golgi apparatus is found in perinuclear and peripheral cytoplasmic positions. The formation of granular endoplasmic reticulum occurs in the vicinity of the perinuclear Golgi apparatus. The differentiation of cell and nuclear forms requires approximately 20 days. The morphological changes of differentiation are discussed in relation to the participation of the Golgi apparatus in the differentiation of dendrites and in the formation of the granular endoplasmic reticulum.  相似文献   
1000.
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