全文获取类型
收费全文 | 207篇 |
免费 | 26篇 |
专业分类
233篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 34篇 |
2012年 | 6篇 |
2011年 | 14篇 |
2010年 | 3篇 |
2009年 | 13篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 15篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1981年 | 2篇 |
1975年 | 2篇 |
1924年 | 1篇 |
1921年 | 1篇 |
1920年 | 1篇 |
1915年 | 2篇 |
1914年 | 1篇 |
1909年 | 1篇 |
1902年 | 1篇 |
1901年 | 1篇 |
1897年 | 2篇 |
1892年 | 1篇 |
1891年 | 1篇 |
1889年 | 1篇 |
1888年 | 1篇 |
1887年 | 1篇 |
1883年 | 3篇 |
1882年 | 5篇 |
1881年 | 2篇 |
1880年 | 1篇 |
1879年 | 6篇 |
1878年 | 2篇 |
1877年 | 2篇 |
1876年 | 1篇 |
排序方式: 共有233条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
26.
27.
28.
29.
Abrahamsen H Baillie G Ngai J Vang T Nika K Ruppelt A Mustelin T Zaccolo M Houslay M Taskén K 《Journal of immunology (Baltimore, Md. : 1950)》2004,173(8):4847-4858
Ligation of the TCR along with the coreceptor CD28 is necessary to elicit T cell activation in vivo, whereas TCR triggering alone does not allow a full T cell response. Upon T cell activation of human peripheral blood T cells, we found that the majority of cAMP was generated in T cell lipid rafts followed by activation of protein kinase A. However, upon TCR and CD28 coligation, beta-arrestin in complex with cAMP-specific phosphodiesterase 4 (PDE4) was recruited to lipid rafts which down-regulated cAMP levels. Whereas inhibition of protein kinase A increased TCR-induced immune responses, inhibition of PDE4 blunted T cell cytokine production. Conversely, overexpression of either PDE4 or beta-arrestin augmented TCR/CD28-stimulated cytokine production. We show here for the first time that the T cell immune response is potentiated by TCR/CD28-mediated recruitment of PDE4 to lipid rafts, which counteracts the local, TCR-induced production of cAMP. The specific recruitment of PDE4 thus serves to abrogate the negative feedback by cAMP which is elicited in the absence of a coreceptor stimulus. 相似文献
30.
KARIN NORÉN ERS ANGERBJÖRN PÁLL HERSTEINSSON 《Biological journal of the Linnean Society. Linnean Society of London》2009,97(1):18-26
The genetic composition of a population reflects several aspects of the organism and its environment. The Icelandic Arctic fox population exceeds 8000 individuals and is comprised of both coastal and inland foxes. Several factors may affect within-population movement and subsequent genetic population structure. A narrow isthmus and sheep-proof fences may prevent movement between the north-western and central part and glacial rivers may reduce movement between the eastern and central part of Iceland. Moreover, population density and habitat characteristics can influence movement behaviour further. Here, we investigate the genetic structure in the Icelandic Arctic fox population ( n = 108) using 10 microsatellite loci. Despite large glacial rivers, we found low divergence between the central and eastern part, suggesting extensive movement between these areas. However, both model- and frequency-based analyses suggest that the north-western part is genetically differentiated from the rest of Iceland (FST = 0.04, DS = 0.094), corresponding to 100–200 generations of complete isolation. This suggests that the fences cannot be the sole cause of divergence. Rather, the isthmus causes limited movement between the regions, implying that protection in the Hornstrandir Nature Reserve has a minimal impact on Arctic fox population size in the rest of Iceland. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 18–26. 相似文献