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   85篇
  免费   1篇
教育与普及   2篇
现状及发展   18篇
研究方法   3篇
综合类   59篇
自然研究   4篇
  2016年   2篇
  2013年   1篇
  2012年   1篇
  2011年   8篇
  2010年   1篇
  2009年   1篇
  2008年   3篇
  2007年   3篇
  2006年   5篇
  2005年   2篇
  2004年   5篇
  2003年   4篇
  2002年   2篇
  2001年   5篇
  2000年   1篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1980年   3篇
  1979年   3篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1975年   2篇
  1973年   2篇
  1972年   2篇
  1971年   1篇
  1970年   6篇
  1969年   2篇
  1968年   2篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
排序方式: 共有86条查询结果,搜索用时 265 毫秒
71.
Zusammenfassung Nach experimentellerTrichophytonmentagrophytes-Infektion wurden in den Stratum-Corneum-Zellen des Meerschweinchens intrasquamale Pilshyphen identifiziert. Dies erlaubt ein detailliertes Verständnis der Pathogenese einer.Dermatophyteninfektion.  相似文献   
72.
L Rohrer  M Freeman  T Kodama  M Penman  M Krieger 《Nature》1990,343(6258):570-572
The macrophage scavenger receptor, which has been implicated in the pathogenesis of atherosclerosis, has an unusually broad binding specificity. Ligands include modified low-density lipoprotein and some polyanions (for example, poly(I) but not poly(C]. The scavenger receptor type I (ref. 3) has three principal extracellular domains that could participate in ligand binding: two fibrous coiled-coil domains (alpha-helical coiled-coil domain IV and collagen-like domain V), and the 110-amino-acid cysteine-rich C-terminal domain VI. We have cloned complementary DNAs encoding a second scavenger receptor which we have termed type II. This receptor is identical to the type I receptor, except that the cysteine-rich domain is replaced by a six-residue C terminus. Despite this truncation, the type II receptor mediates endocytosis of chemically modified low-density lipoprotein with high affinity and specificity, similar to that of the type I receptor. Therefore one or both of the extracellular fibrous domains are responsible for the unusual ligand-binding specificity of the receptor.  相似文献   
73.
74.
75.
76.
Dyson F 《Nature》2004,427(6972):297
  相似文献   
77.
ICOS is critical for CD40-mediated antibody class switching   总被引:58,自引:0,他引:58  
The inducible co-stimulatory molecule (ICOS) is a CD28 homologue implicated in regulating T-cell differentiation. Because co-stimulatory signals are critical for regulating T-cell activation, an understanding of co-stimulatory signals may enable the design of rational therapies for immune-mediated diseases. According to the two-signal model for T-cell activation, T cells require an antigen-specific signal and a second, co-stimulatory, signal for optimal T-cell activation. The co-stimulatory signal promotes T-cell proliferation, lymphokine secretion and effector function. The B7-CD28 pathway provides essential signals for T-cell activation, but does not account for all co-stimulation. We have generated mice lacking ICOS (ICOS-/- ) to determine the essential functions of ICOS. Here we report that ICOS-/- mice exhibit profound deficits in immunoglobulin isotype class switching, accompanied by impaired germinal centre formation. Class switching was restored in ICOS-/- mice by CD40 stimulation, showing that ICOS promotes T-cell/B-cell collaboration through the CD40/CD40L pathway.  相似文献   
78.
E Zouros  K R Freeman  A O Ball  G H Pogson 《Nature》1992,359(6394):412-414
Inheritance of mitochondrial DNA in animals was thought to be strictly maternal. Recently, evidence for incidental paternal mtDNA leakage was obtained in hybrid crosses of Drosophila and mice. In mice, the frequency of paternal mtDNA contributions was estimated at 10(-4), compared with maternal contributions. The common occurrence in the marine mussel Mytilus of heteroplasmic individuals with two or more types of highly diverged mtDNA molecules was interpreted as strong evidence for biparental mtDNA inheritance by some, but not by others. We report here results from pair-matings involving two species of mussels, Mytilus edulis and Mytilus trossulus. Extensive contribution of paternal mtDNA, amounting to several orders of magnitude higher than that inferred for Drosophila or mice, was observed in both intra- and interspecific crosses.  相似文献   
79.
80.
Class II major histocompatibility complex (MHC) molecules function as antigen-presenting elements as well as signal transducers on B lymphocytes. We previously reported that a B lymphoma cell transfectant, 5C2, expressing genetically engineered I-Ak molecules with truncated cytoplasmic domains was severely impaired in both antigen presentation and in anti-Ia-induced intracytoplasmic signalling. These two functions could be restored by preculturing 5C2 cells with cyclic AMP analogues. Here we demonstrate that impaired signal transduction by truncated class II molecules results in a deficiency in induction of the newly defined B-cell accessory molecule B7 (ref. 8), which can be reversed by restoration of B7 expression. These data imply that contact of the T-cell antigen receptor with MHC/antigen ligand results in signal transmission through the class II cytoplasmic domain. This signal, which can be mimicked by dibutyryl cAMP, induces expression of B7, resulting in effective antigen presentation. The fact that crosslinking of surface class II MHC also induces B7 expression on normal resting human B cells supports this contention.  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