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   184006篇
  免费   14581篇
  国内免费   50篇
  2018年   1858篇
  2017年   1798篇
  2016年   2319篇
  2015年   2249篇
  2014年   3049篇
  2013年   4325篇
  2012年   4986篇
  2011年   5486篇
  2010年   3820篇
  2009年   3469篇
  2008年   4992篇
  2007年   5267篇
  2006年   4927篇
  2005年   4666篇
  2004年   4820篇
  2003年   4709篇
  2002年   4708篇
  2001年   8433篇
  2000年   8613篇
  1999年   6349篇
  1998年   2022篇
  1997年   2055篇
  1996年   1829篇
  1995年   1701篇
  1992年   5213篇
  1991年   5386篇
  1990年   5157篇
  1989年   5138篇
  1988年   4756篇
  1987年   4512篇
  1986年   4096篇
  1985年   4262篇
  1984年   3443篇
  1983年   2929篇
  1982年   1949篇
  1981年   1750篇
  1980年   1733篇
  1979年   3223篇
  1978年   2568篇
  1977年   2296篇
  1976年   2100篇
  1975年   2569篇
  1974年   2896篇
  1973年   2830篇
  1972年   2667篇
  1971年   2427篇
  1970年   2123篇
  1969年   2032篇
  1968年   1912篇
  1967年   1746篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
901.
902.
The role of leucine-47 in determining the structure and activity of human epidermal growth factor was examined using site-directed mutagenesis. Wild type protein and four variants in which Leu47 was replaced by valine, glutamate, aspartate and alanine were produced from yeast. 1H NMR experiments demonstrated that substitution of Leu47 had little effect on the protein structure. The observed reduction in receptor binding affinity caused by the substitutions could thus be attributed to perturbation of a residue directly involved in receptor interactions.  相似文献   
903.
904.
Regional association analysis is one of the most powerful tools for gene mapping because instead analysis of individual variants it simultaneously considers all variants in the region. Recent development of the models for regional association analysis involves functional data analysis approach. In the framework of this approach, genotypes of variants within region as well as their effects are described by continuous functions. Such approach allows us to use information about both linkage and linkage disequilibrium and reduce the influence of noise and/or observation errors. Here we define a functional linear mixed model to test association on independent and structured samples. We demonstrate how to test fixed and random effects of a set of genetic variants in the region on quantitative trait. Estimation of statistical properties of new methods shows that type I errors are in accordance with declared values and power is high especially for models with fixed effects of genotypes. We suppose that new functional regression linear models facilitate identification of rare genetic variants controlling complex human and animal traits. New methods are implemented in computer software FREGAT which is available for free download at http://mga.bionet.nsc.ru/soft/FREGAT/.  相似文献   
905.
A novel algorithm for multiple alignment of biological sequences is suggested. At the first step the DotHelix procedure is employed for construction of motifs, i.e. continuous fragments of local similarity of various “thickness” and strength, and then these motifs are concatenated into chains consistent with the order of letters in the sequences. The algorithm is implemented in the MA-Tools program of the GeneBee package. An example illustrating the effectivity of the algorithm is presented.  相似文献   
906.
907.
908.
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   
909.
There are data suggesting that HMG1 protein may be involved in DNA replication. Recently we have found that only the acetylated form of the protein generates tetramers, stimulates the activity of DNA polymerase alpha (EC 2.7.7.7) (with activated DNA as a template) and forms a specific complex with it. This paper compares some properties of the acetylated and nonacetylated forms of HMG1 protein and shows that it is only the acetylated form which serves as a histone assembly factor, increases the melting temperature of poly d[(A-T)] and stimulates the activity of DNA polymerase alpha when histone H1-depleted chromatin is used as a template.  相似文献   
910.
For 35 of 50 patients with rheumatoid arthritis traditional drug therapy was a minor success for a long time. Without any modifications of the drug therapy every patient went through a course of hyperbaric oxygenation (HBO): 21 sessions under 1.7 ata for 40 min. Good clinical results both immediate and remote have been obtained. The effect of HBO on the immune system of the patients has intensified the suppressive function of T-lymphocytes (especially with systemic symptoms of the disease), normalized cell-bound immunity and decreased the serum concentration in immune complexes.  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