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   505篇
  免费   35篇
  2021年   5篇
  2020年   1篇
  2019年   2篇
  2018年   8篇
  2017年   4篇
  2016年   12篇
  2015年   22篇
  2014年   23篇
  2013年   33篇
  2012年   28篇
  2011年   22篇
  2010年   35篇
  2009年   32篇
  2008年   18篇
  2007年   23篇
  2006年   19篇
  2005年   20篇
  2004年   18篇
  2003年   7篇
  2002年   12篇
  2001年   11篇
  2000年   9篇
  1999年   12篇
  1998年   12篇
  1997年   12篇
  1996年   4篇
  1995年   6篇
  1994年   5篇
  1993年   7篇
  1992年   4篇
  1991年   9篇
  1989年   4篇
  1988年   9篇
  1987年   4篇
  1986年   1篇
  1985年   8篇
  1984年   8篇
  1983年   6篇
  1982年   18篇
  1981年   7篇
  1980年   1篇
  1979年   5篇
  1978年   5篇
  1977年   11篇
  1976年   5篇
  1975年   6篇
  1974年   2篇
  1972年   1篇
  1971年   1篇
  1877年   1篇
排序方式: 共有540条查询结果,搜索用时 406 毫秒
1.
CFC syndrome: a syndrome distinct from Noonan syndrome   总被引:2,自引:0,他引:2  
We report two children with a common pattern of birth defects. Both have very sparse, curly hair, nystagmus and mental retardation. The first one has Noonan syndrome habitus associated with keratosis plantaris and nystagmus; the second one has a slightly Noonan-like face, macrocephaly, keratosis pilaris, and hypertrophic cardiomyopathy. They represent the extreme of a spectrum of congenital defects recently reported independently as CFC syndrome by Reynolds and as "Noonan-like short stature syndrome with sparse hair" by Baraitser and Patton. The clinical features are reviewed and the autonomy of the syndrome with regards to Noonan syndrome, is disputed, since every sign seems to occur independently in Noonan syndrome. The father of the second case probably has a minor syndrome expression, pointing to probable autosomal dominant inheritance.  相似文献   
2.
The rate of generation of superoxide ion, the concentration of Cu, Zn superoxide dismutase and the hematological parameters were measured in red blood cells obtained from Fanconi anemia patients and from healthy individuals. No significative difference in the superoxide dismutase concentration was found, while the rate of generation of the superoxide ion doubled in Fanconi anemia patients. The steady-state concentration of the superoxide ion was calculated from these data and was found to be 2.3 times higher in Fanconi anemia erythrocytes than in controls. The possible consequences with respect to the alterations in FA are discussed.  相似文献   
3.
4.
5.
6.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.   相似文献   
7.
8.
Two glnB-like genes have been isolated from Herbaspirillum seropedicae by complementation of the Klebsiella pneumoniae glnB502 mutant for growth on nitrate. One of these glnB-like genes has been sequenced and shows strong identity with GlnB proteins derived from other organisms. A Tn5-20 mutation of this glnB was Nif negative.  相似文献   
9.
10.
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