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   182篇
  免费   27篇
  2021年   3篇
  2020年   3篇
  2019年   2篇
  2017年   5篇
  2016年   7篇
  2015年   9篇
  2014年   9篇
  2013年   6篇
  2012年   6篇
  2011年   10篇
  2010年   6篇
  2009年   13篇
  2008年   7篇
  2007年   7篇
  2006年   18篇
  2005年   5篇
  2004年   6篇
  2003年   4篇
  2002年   3篇
  2001年   7篇
  2000年   6篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   5篇
  1992年   10篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1988年   2篇
  1987年   3篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1978年   3篇
  1977年   2篇
  1975年   1篇
  1974年   2篇
  1969年   2篇
  1933年   1篇
排序方式: 共有209条查询结果,搜索用时 328 毫秒
11.
We have shown previously that human sperm bind and enter leukocytes expressing surface HLA class II molecules. In the present study, mutant B lymphoblastoid cells and HLA-DR-transfected murine 3T3 fibroblasts are used to confirm that HLA class II molecules are somatic cell receptors for sperm. Further, for isolated HLA-DR expressed on murine cells, we show that sperm receptor activity requires the presence of sulfated carbohydrates. As carriers of multiple HLA-DR binding ligands, sperm may 1) mimic the target cell-activating effects of anti-DR antibody and 2) bind HIV through CD4-like or alternate receptors. By these or other mechanisms, sperm/somatic cell interactions in the female reproductive tract may affect fertility and potentiate the sexual transmission of AIDS.  相似文献   
12.
13.
Herons (Aves: Ardeidae) are rare in the fossil record globally. Fossil taxa referred to Ardeinae and Nycticoracini are known from as early as the early Oligocene and ardeids undetermined to subfamily include some as old as the early Eocene. In Australasia, the pre-Pliocene record is restricted to one species from the early Miocene of New Zealand. On the basis of a tarsometatarsus and a coracoid we describe a new species of bittern (Ardeidae: Botaurinae) from the St Bathans Fauna, of early Miocene age, from Otago, New Zealand. This is only the third and the oldest pre-Quaternary record for Botaurinae globally.  相似文献   
14.
15.

Background  

The timing of the origin of introns is of crucial importance for an understanding of early genome architecture. The Exon theory of genes proposed a role for introns in the formation of multi-exon proteins by exon shuffling and predicts the presence of conserved splice sites in ancient genes. In this study, large-scale analysis of potential conserved splice sites was performed using an intron-exon database (ExInt) derived from GenBank.  相似文献   
16.
Both systemic lupus erythematosus (SLE) and vitiligo are autoimmune disorders that have strong evidence of complex genetic contributions to their etiology, but, to date, efforts using genetic linkage to find the susceptibility genes for either phenotype have met with limited success. Since autoimmune diseases are thought to share at least some of their genetic origins, and since only a small minority (16 of 92) of the European-American pedigrees multiplex for SLE in our collection have one or more affected members with vitiligo, we hypothesized that these pedigrees might be more genetically homogeneous at loci important to both SLE and vitiligo and, hence, have increased power for detection of linkage. We therefore evaluated genomewide microsatellite-marker-scan data for markers at an average marker density of approximately 11 cM in these 16 European-American pedigrees and identified a significant linkage at 17p13, where the maximum multipoint parametric LOD score was 3.64 (P<4.3x10(-5)) and the nonparametric linkage score was 4.02 (P<2.8x10(-5)), respectively. The segregation behavior of this linkage suggests a recessive mode of inheritance with a virtually homogeneous genetic effect in these 16 pedigrees. These results support the hypotheses that SLE and vitiligo may share important genetic effects and that sampling on the basis of clinical covariates dramatically improves power to identify genetic effects.  相似文献   
17.
Qualitative urinalysis using Multistix reagent strips for the detection of urinary pH, protein, glucose, bilirubin, blood, ketone, urobilinogen and creatinine can be carried out with a few drops of mouse urine. The use of metabolic cages is not practical for such qualitative studies particularly when several animals are involved. Here we describe two different methods for collecting pure mouse urine. The single animal method (SAM) involves allowing a single mouse to urinate on Glad cling wrap outside of the animal cage. The multiple animal method (MAM) involves partitioning seven mice into seven different make-shift compartments laid out on top of the cling wrap and allowing them to urinate. The voided urine, in each case, is then aspirated into micro-centrifuge tubes using a Pipetman. Without coercion pure urine was obtained as early as 12 s. Volumes in the range of 10-250 microl were obtained. Modifications of the SAM could prove useful for rat or mouse urine collection under conditions of microgravity.  相似文献   
18.
19.
20.
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