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   251281篇
  免费   23103篇
  国内免费   260篇
  274644篇
  2018年   2807篇
  2017年   2757篇
  2016年   3700篇
  2015年   4147篇
  2014年   5090篇
  2013年   7079篇
  2012年   7899篇
  2011年   8534篇
  2010年   5739篇
  2009年   5102篇
  2008年   7264篇
  2007年   7433篇
  2006年   7001篇
  2005年   6684篇
  2004年   6549篇
  2003年   6304篇
  2002年   6155篇
  2001年   12037篇
  2000年   11980篇
  1999年   9163篇
  1998年   2681篇
  1997年   2756篇
  1996年   2697篇
  1995年   2481篇
  1994年   2427篇
  1993年   2318篇
  1992年   7184篇
  1991年   6988篇
  1990年   7058篇
  1989年   6845篇
  1988年   6361篇
  1987年   6015篇
  1986年   5359篇
  1985年   5667篇
  1984年   4466篇
  1983年   3870篇
  1982年   2677篇
  1981年   2497篇
  1980年   2307篇
  1979年   4114篇
  1978年   3137篇
  1977年   2890篇
  1976年   2830篇
  1975年   3270篇
  1974年   3505篇
  1973年   3528篇
  1972年   3059篇
  1971年   2845篇
  1970年   2534篇
  1969年   2301篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The results of complementation analysis of nitrosoguanidine-induced mutants of F-like drd-plasmid pAP18-1 (Tc, ColV) testified to the existence of at least 3 tra regions (tra1, tra2, tra3) and regulating locus fin V in the genome of this plasmid. By means of molecular cloning of tra2 region and locus fin V of plasmid pAP18-1drd were located in Sall-fragment f5 (3.9 MD).  相似文献   
942.
Ombuin (7,4′-dimethyl quercetin) (10 μg ml-1, for 12 wk), glycyrrhizin/quercetin (80 μg ml-1and 10 μg ml-1respectively, for 18 wk), ribavirin (10 μg ml-1, for 12 wk) and quercetin/ribavirin (10 μg ml-1each, for 9–12 wk) reduced the titre of apple stem grooving virus (ASGV) when applied in vitro to infected tissue cultures of Nicotiana occidentalis obliqua Wheeler, and/or Malus domestica. ASGV was not detectable in both plant species after the quercitin/ribavirin treatment when tested by ISEM, herbaceous host indexing, RT-PCR, and immunocapture RT-PCR. A sensitive immunocapture RT-PCR procedure for the detection of ASGV was developed for the screening of treated samples to assess antiviral activity.  相似文献   
943.
944.
The phytocenotic diversity of the Altai steppe piedmont is described. Plant communities were ordinated along the moisture gradient. The results were used to analyze the structure of vegetation of steppe hill massifs. Distribution of steppe vegetation over an ideal hill was simulated, and the main patterns of distribution were typified.  相似文献   
945.
Lipid synthesis in permeabilized cultured rat hepatocytes   总被引:1,自引:0,他引:1  
Hepatic lipid synthesis was verified and studied in lysolecithin-permeabilized cultured rat hepatocytes and compared to that of intact liver cells. Triacylglycerol synthesis in permeabilized cells incubated in the presence of glycerol 3-phosphate and long chain fatty acids approached that of intact hepatocytes. Similarly, phosphatidylcholine synthesis in permeable cells incubated in the presence of exogenous CDP-choline was similar to that of intact hepatocytes and at the expense of microsomal neutral lipid synthesis. Phosphatidic acid accumulation in lysolecithin-permeabilized liver cells was remarkably increased as compared to that of intact cells, and its synthesis was mostly accounted for by the activity of mitochondrial glycerol-3-phosphate acyltransferase. Mitochondrial-generated phosphatidate was found to migrate to the endoplasmic reticulum, thus establishing a novel lipid esterification pathway which begins in mitochondrial glycerol 3-phosphate acylation and results in microsomal triacylglycerol and phospholipid synthesis. The free access of permeabilized liver cells to substrates and modulators of lipid synthesis, while maintaining an overall synthetic pattern similar to that of intact hepatocytes, makes them a system of choice for studying hepatic lipid synthesis in general and the microsomal/mitochondrial distribution of fluxes in particular.  相似文献   
946.
N.C. Lee 《CMAJ》1990,142(11):1176-1177
  相似文献   
947.
Yellow lupine seeds were found to contain two proteins and a low molecular weight fraction possessing the ability to bind Mo, W and radionuclides from the Chernobyl nuclear power in vivo and the 185W isotope in vitro. These proteins differ in their electrophoretic mobility. The electrophoretically less mobile protein undergoes proteolytic degradation; the proteolytic product retains the ability to accumulate microelements.  相似文献   
948.
949.
950.
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