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   168篇
  免费   1篇
  国内免费   1篇
系统科学   17篇
教育与普及   15篇
理论与方法论   2篇
现状及发展   19篇
研究方法   11篇
综合类   96篇
自然研究   10篇
  2020年   1篇
  2019年   1篇
  2017年   5篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2012年   5篇
  2011年   13篇
  2010年   5篇
  2009年   13篇
  2008年   7篇
  2007年   7篇
  2006年   10篇
  2005年   4篇
  2004年   8篇
  2003年   6篇
  2002年   7篇
  2001年   7篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   6篇
  1987年   5篇
  1986年   4篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1980年   2篇
  1979年   3篇
  1978年   4篇
  1977年   1篇
  1975年   1篇
  1972年   2篇
  1971年   2篇
  1970年   4篇
  1968年   1篇
  1967年   3篇
  1966年   1篇
排序方式: 共有170条查询结果,搜索用时 31 毫秒
21.
R J Shaw  G M Walsh  O Cromwell  R Moqbel  C J Spry  A B Kay 《Nature》1985,316(6024):150-152
Eosinophils, a class of granular leukocytes, are prominent in many inflammatory processes, particularly in asthma, certain allergic diseases and during infections with helminthic parasites. Following incubation with the Ca ionophore A23187 (refs 1-4) (a non-physiological agent which circumvents membrane calcium-gating mechanisms), eosinophils generate large amounts of sulphidopeptide leukotrienes, potent inducers of smooth muscle constriction and mucus production. These are now known to represent the activity previously termed 'slow-reacting substance of anaphylaxis' (SRS-A) but attempts to identify a physiological stimulus for SRS-A production by eosinophils have so far been unsuccessful. The cells contain recognized receptors for IgG (Fc) and it is known that they adhere to, and can be activated by, contact with the surface of large organisms such as helminthic larvae. We show here that eosinophils, particularly when activated, produce sulphidopeptide leukotrienes after contact with large particles coated with IgG.  相似文献   
22.
Y Shimizu  G A Van Seventer  K J Horgan  S Shaw 《Nature》1990,345(6272):250-253
Regulated adhesion of T cells to extracellular matrix (ECM) proteins is likely to be essential in T cell migration. Constitutive binding of various other cell types to ECM components is mediated by members of the VLA (very late antigen) subfamily of integrins. We describe here the regulated binding of resting CD4+ human T cells to ECM through three VLA integrins: VLA-4 and VLA-5 binding to fibronectin (FN), and a novel pathway of VLA-6 binding to laminin (LN). Binding to ECM is regulated in two ways. First, unlike other VLA-mediated interactions, VLA binding activity of the T cells is rapidly and dramatically augmented with cell activation without change in level of expression of the VLA molecules. Second, binding is regulated with T-cell differentiation; memory T cells express three- to four-fold more VLA-4, VLA-5, and VLA-6 than do naive cells, and bind more efficiently through them to FN and LN.  相似文献   
23.
隔热涂层     
Stearns  CA 《世界科学》1989,11(2):37-38
  相似文献   
24.
Replication of EBV in epithelial cells during infectious mononucleosis.   总被引:2,自引:0,他引:2  
S M Lemon  L M Hutt  J E Shaw  J L Li  J S Pagano 《Nature》1977,268(5617):268-270
  相似文献   
25.
Mapping of mutation causing Friedreich's ataxia to human chromosome 9   总被引:29,自引:0,他引:29  
Friedreich's ataxia is an autosomal recessive disease with progressive degeneration of the central and peripheral nervous system. The biochemical abnormality underlying the disorder has not been identified. Prompted by the success in localizing the mutations causing Duchenne muscular dystrophy, Huntington's disease and cystic fibrosis, we have undertaken molecular genetic linkage studies to determine the chromosomal site of the Friedreich's ataxia mutation as an initial step towards the isolation and characterization of the defective gene. We report the assignment of the gene mutation for this disorder to chromosome 9p22-CEN by genetic linkage to an anonymous DNA marker MCT112 and the interferon-beta gene probe. In contrast to the clinical variation seen for the disorder, no evidence of genetic heterogeneity is observed.  相似文献   
26.
Summary Circulating immune complexes in the sera of patients with confirmed histological diagnosis of carcinoma of the prostate, were found to interfere in the sensitized leukocyte's in vitro reactivity to prostate cancer associated antigen as evaluated by tube leukocyte adherence inhibition assay, thereby suggesting an inhibitory role of such serum factors in host's anti tumor cell mediated immune responses.4 November 1986  相似文献   
27.
Summary Isolates ofTrichoderma spp. from pasture soils of Nova Scotia produce at least 7 toxic peptides, probably related to alamethicin, some of which inhibit the growth of cellulase producing rumen bacteria. One of the peptides has been obtained in crystalline form and crystal data on this material is reported.  相似文献   
28.
29.
30.
Shaw RJ  Cantley LC 《Nature》2006,441(7092):424-430
All eukaryotic cells coordinate cell growth with the availability of nutrients in their environment. The mTOR protein kinase has emerged as a critical growth-control node, receiving stimulatory signals from Ras and phosphatidylinositol-3-OH kinase (PI(3)K) downstream from growth factors, as well as nutrient inputs in the form of amino-acid, glucose and oxygen availability. Notably, components of the Ras and PI(3)K signalling pathways are mutated in most human cancers. The preponderance of mutations in these interconnected pathways suggests that the loss of growth-control checkpoints and promotion of cell survival in nutrient-limited conditions may be an obligate event in tumorigenesis.  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