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   1338198篇
  免费   145430篇
  国内免费   637篇
  1484265篇
  2018年   11896篇
  2016年   16415篇
  2015年   22393篇
  2014年   26349篇
  2013年   37683篇
  2012年   42311篇
  2011年   43037篇
  2010年   29568篇
  2009年   27544篇
  2008年   39068篇
  2007年   40405篇
  2006年   37739篇
  2005年   36395篇
  2004年   36081篇
  2003年   34726篇
  2002年   33869篇
  2001年   55217篇
  2000年   54908篇
  1999年   44425篇
  1998年   17347篇
  1997年   17751篇
  1996年   16831篇
  1995年   15799篇
  1994年   15458篇
  1993年   15435篇
  1992年   37293篇
  1991年   36607篇
  1990年   35851篇
  1989年   35011篇
  1988年   32396篇
  1987年   31407篇
  1986年   29140篇
  1985年   29272篇
  1984年   24392篇
  1983年   21398篇
  1982年   16650篇
  1981年   15031篇
  1980年   14165篇
  1979年   23324篇
  1978年   18676篇
  1977年   16937篇
  1976年   16087篇
  1975年   17837篇
  1974年   19238篇
  1973年   18953篇
  1972年   17179篇
  1971年   15687篇
  1970年   13573篇
  1969年   13174篇
  1968年   11672篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Intraperitoneal administration of marinobufagenin resulted in a reliable and dose-dependent suppression of ethanol self-administration in drug- and experimentally naive DBA/2 mice. The findings suggest that Na/K-ATPase contributes to both mediation of the ethanol reinforcing properties and the mood regulation.  相似文献   
52.
Methods of synthesis of coproporphyrin and uroporphyrin by using bacteria of the genus Arthrobacter are proposed. Metal complexes of coproporphyrin and uroporphyrin with Pt, Pd, and Zn were synthesized. Their structures were identified by spectrophotometry, IR spectrometry, 1H-NMR, mass spectrometry, and HPLC. Data showing the possibility to use coproporphyrin III-metal complexes as luminophores for fluorescence detection of tumors. The current and prospective uses of metal complexes of water-soluble natural porphyrins in advanced immunofluorescence assays are discussed.  相似文献   
53.
54.
Meiosis is the process by which diploid germ cells divide to produce haploid gametes for sexual reproduction. The process is highly conserved in eukaryotes, however the recent availability of mouse models for meiotic recombination has revealed surprising regulatory differences between simple unicellular organisms and those with increasingly complex genomes. Moreover, in these higher eukaryotes, the intervention of physiological and sex-specific factors may also influence how meiotic recombination and progression are monitored and regulated. This review will focus on the recent studies involving mouse mutants for meiosis, and will highlight important differences between traditional model systems for meiosis (such as yeast) and those involving more complex cellular, physiological and genetic criteria.  相似文献   
55.
56.
The proteolytic activity of the leaf extracellular space of wheat cultivars Pigüé and Isla Verde was estimated after inoculation of either detached leaves or plants with the fungus Septoria tritici. Pigüé is resistant, whereas Isla Verde is susceptible to the disease caused by S. tritici. Viable conidiospores of the fungus caused similar increases in both hydrogen peroxide production and chitinase activity of the cultivars studied. In contrast, they caused a decrease in the extracellular serine proteinase activity of Isla Verde and a significant increase in that of Pigüé. Independently of the cultivar from which it was extracted, the extracellular serine proteinase inhibited the germination of Septoria tritici conidiospores. These results suggest that the proteolytic activity of the leaf extracellular space can participate in the defence of wheat plants against Septoria tritici. Its regulation may be controlled by specific defence components of each cultivar.  相似文献   
57.
58.
G A Klevazel' 《Ontogenez》2001,32(6):477-480
Analysis of the recording structures in mammals, such as dentine, cementum, or bone tissue, makes it possible to estimate the parameters of individual history of life: age at the moment of death, seasons of death and birth, growth rate, age of sexual maturation, etc. Using the reindeer (Rangifer tarandus) as an example, it has been shown what specific life features essential for population studies may be estimated when only mandibles with teeth are available.  相似文献   
59.
60.
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