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   283篇
  免费   48篇
  2017年   2篇
  2016年   4篇
  2015年   10篇
  2014年   9篇
  2013年   14篇
  2012年   17篇
  2011年   14篇
  2010年   12篇
  2009年   8篇
  2008年   9篇
  2007年   6篇
  2006年   5篇
  2005年   7篇
  2004年   5篇
  2003年   6篇
  2001年   7篇
  2000年   6篇
  1999年   9篇
  1998年   15篇
  1997年   5篇
  1996年   6篇
  1995年   8篇
  1994年   4篇
  1993年   6篇
  1992年   6篇
  1991年   8篇
  1990年   8篇
  1989年   10篇
  1988年   6篇
  1987年   8篇
  1986年   4篇
  1985年   6篇
  1984年   6篇
  1983年   9篇
  1982年   3篇
  1981年   3篇
  1980年   2篇
  1979年   4篇
  1978年   5篇
  1977年   5篇
  1976年   3篇
  1975年   2篇
  1974年   3篇
  1973年   4篇
  1972年   2篇
  1971年   2篇
  1968年   4篇
  1967年   2篇
  1966年   4篇
  1965年   6篇
排序方式: 共有331条查询结果,搜索用时 15 毫秒
1.

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.  相似文献   
2.
A modified conductance medium for the detection of Salmonella spp   总被引:2,自引:0,他引:2  
Selenite-cystine/trimethylamine oxide/dulcitol medium has been used in conjunction with conductance instruments to detect the presence of Salmonella spp. in foods and faeces. However, a small but significant number of salmonella strains were missed by this method. The majority of these strains were detected when dulcitol was substituted by mannitol and tested on two separate Malthus conductance instruments. Some strains of Citrobacter freundii and Escherichia coli continued to give false positive results. Attempts are made to explain why the substitution of mannitol for dulcitol gives an improved medium.  相似文献   
3.
The oligodeoxynucleotide dACCGCGGCTGCT, complementary to Escherichia coli small ribosomal subunit RNA residues 520-531, has been used to probe subunit conformation and to localize the sequence in the subunit. Conditions for binding of the cDNA to 30S subunits were optimized and specificity of the interaction was demonstrated by RNase H cleavage. Three kinds of terminal modification of this cDNA were used to allow its localization by immune electron microscopy. A solid phase support with 5'-dimethoxytrity-N6-delta 2-isopentenyl-adenosine linked to controlled pore glass was synthesized, and used to prepare oligomer with an added 3'-terminal residue of isopentenyl adenosine. cDNA with a 5' primary amine substituent was modified with 1-fluoro-2,4-dinitrobenzene to prepare 5'-dinitrophenyl oligonucleotide, and both modifications together gave doubly-derivatized probes. Immune electron microscopy with antibodies to dinitrophenol, isopentenyl adenosine, or both, was used to place the cDNA on 30S subunits. In each case the probe was placed at a single site at the junction of the head and body of the subunit, near the decoding site and the area in which elongation factor Tu is bound. It is proposed that this segment of ribosomal RNA functions in mRNA binding and orientation.  相似文献   
4.
5.
Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17.  相似文献   
6.
7.
Overlapping cDNA clones representing the entire genome of poliovirus type 3 have been prepared in E. coli by two separate methods. Cloning of RNA . cDNA hybrids produced a more comprehensive set of clones with generally larger cDNA inserts than cloning of double - stranded cDNA. A restriction map of the entire genome and the nucleotide sequence of 2003 bases from the 3' terminus, comprising the region encoding the protease and polymerase proteins, are presented.  相似文献   
8.
Isolation of brain tubulin by affinity chromatography   总被引:2,自引:0,他引:2  
An affinity chromatographic procedure for the isolation of tubulin from brain is described. The yield is good and the method rapid and gentle. Criteria of purity are colchicine binding, SDS acrylamide gel electrophoresis, and velocity sedimentation.  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