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   43309篇
  免费   3715篇
  国内免费   268篇
  47292篇
  2018年   525篇
  2017年   502篇
  2016年   649篇
  2015年   718篇
  2014年   925篇
  2013年   1148篇
  2012年   1250篇
  2011年   1313篇
  2010年   900篇
  2009年   892篇
  2008年   1219篇
  2007年   1195篇
  2006年   1205篇
  2005年   1035篇
  2004年   1001篇
  2003年   939篇
  2002年   924篇
  2001年   2797篇
  2000年   2492篇
  1999年   1813篇
  1998年   614篇
  1997年   531篇
  1996年   471篇
  1995年   405篇
  1994年   388篇
  1992年   1311篇
  1991年   1201篇
  1990年   1135篇
  1989年   1088篇
  1988年   978篇
  1987年   967篇
  1986年   837篇
  1985年   835篇
  1984年   599篇
  1983年   536篇
  1982年   382篇
  1979年   652篇
  1978年   473篇
  1977年   433篇
  1976年   390篇
  1975年   517篇
  1974年   603篇
  1973年   576篇
  1972年   600篇
  1971年   564篇
  1970年   537篇
  1969年   546篇
  1968年   444篇
  1967年   389篇
  1966年   433篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
81.
Efforts to develop molecular tools for genetic analysis and breeding of common bean in the tropics are still limited. The number of microsatellite markers available for the crop is small compared to other crops of similar social and economic importance. As part of a project to broaden the use of molecular tools in bean breeding, a genomic library enriched for AG/TC repeat sequences was constructed for Phaseolus vulgaris. Twenty microsatellite markers were initially developed and 10 were characterized using a panel of 85 representative accessions of the bean gene bank. The number of alleles per marker ranged from three to 10. The polymorphism information content (PIC) varied from 0.23 to 0.80. The results indicate that the new markers can be readily used in genetically analysis of common bean.  相似文献   
82.
It has been experimentally established that cultivation of yeast cells in depleted, dietary or normal nutrient aqueous solutions enriched with ortho-H2O spin isomers is accompanied by an increase in the amount of carbon dioxide produced by the cells and an increase in their biomass. It has been revealed that the rate of metabolic processes and biological activity depends on the quality of nutrition and enhances in time in both nutrient solutions. In contrast, the reproductive function and the rate of cell division are insusceptible to the components of nutrition, but intensified in a solution enriched with ortho-H2O similar to retardation of aging. The observed effects are discussed in assumption that an increase of a portion of ortho-H2O molecules occurs in the neighborhood of water channels in the cell membrane that let through only monomers of H2O and determine the rate vicinity of metabolic processes.  相似文献   
83.
84.
85.
The biodegradation of T-2 toxin was studied by strains of micromycetes which were isolated from the environment. The 26 tested strains were divided into three groups. Group contains strains which degraded T-2 toxin very fast. This toxin could not be chromatographically determined in the medium even after 48 hours of incubation and the antifungal activity of residua against Kluyveromyces fragilis CCY-51-1-2 was low or zero. There were strains of Alternaria sp., Ulocladium sp., Aspergillus candidus, Cladosporium cladosporioides, Rhodotorula sp., Aspergillus flavus and Cladosporium macrocarpum. Group II contains with a low activity and in group III the results were variable and non stable.  相似文献   
86.
Abstract cDNA-RNA liquid hybridization analysis was used to compare the RNA sequence homology between two members of the Nudaurelia β virus family, Trichoplusia ni virus ( T.ni V) and Dasychira pudibunda virus ( D.p V). Heterologous hybridization experiments demonstrated that these viruses shared little sequence homology. Using oligo(dT) chromatography and oligo(dT)12–18 as a primer for cDNA synthesis it was shown that neither T.ni V nor D.p V RNA genomes possess a poly(A) tract at the 3' end.  相似文献   
87.
In these studies we describe the production of three mAb raised to an idiotype on an IgG anticasein antibody isolated from the serum of one IgA-deficient blood donor. These are IgM kappa and block the binding of casein Ag to anticasein antibody. Sera of unrelated IgA-deficient donors were tested for the presence of the idiotype; 15 of 56 IgA-deficient sera (25%) contain the anticasein idiotype, whereas 1 of 45 normal sera was positive. Anticasein antibodies as a whole were predominantly of the IgG1 and IgG3 subclass; idiotype-positive anticaseins are predominantly of the IgG1 subclass. For IgA-deficient donors, the relative amount of idiotype-positive anticasein antibody was correlated with the level of anticasein present in the serum. Studies were done to investigate the potential inheritance of the idiotype in families; in three of four families the idiotype was inherited in an apparent autosomal dominant pattern. Our data show that a common cross-reactive idiotype can be detected in the sera of IgA-deficient individuals and their family members. This suggests that V region markers may be conserved in this humoral immunodeficiency disease.  相似文献   
88.
89.
90.
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