全文获取类型
收费全文 | 316篇 |
免费 | 1篇 |
国内免费 | 5篇 |
专业分类
系统科学 | 4篇 |
教育与普及 | 4篇 |
理论与方法论 | 10篇 |
现状及发展 | 59篇 |
研究方法 | 41篇 |
综合类 | 179篇 |
自然研究 | 25篇 |
出版年
2020年 | 2篇 |
2017年 | 2篇 |
2013年 | 4篇 |
2012年 | 12篇 |
2011年 | 48篇 |
2010年 | 9篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1969年 | 8篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1965年 | 5篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有322条查询结果,搜索用时 15 毫秒
321.
Francis H Chapelle Kathleen O'Neill Paul M Bradley Barbara A Methé Stacy A Ciufo LeRoy L Knobel Derek R Lovley 《Nature》2002,415(6869):312-315
The search for extraterrestrial life may be facilitated if ecosystems can be found on Earth that exist under conditions analogous to those present on other planets or moons. It has been proposed, on the basis of geochemical and thermodynamic considerations, that geologically derived hydrogen might support subsurface microbial communities on Mars and Europa in which methanogens form the base of the ecosystem. Here we describe a unique subsurface microbial community in which hydrogen-consuming, methane-producing Archaea far outnumber the Bacteria. More than 90% of the 16S ribosomal DNA sequences recovered from hydrothermal waters circulating through deeply buried igneous rocks in Idaho are related to hydrogen-using methanogenic microorganisms. Geochemical characterization indicates that geothermal hydrogen, not organic carbon, is the primary energy source for this methanogen-dominated microbial community. These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets. 相似文献
322.
Molecular cloning and expression of the major protein kinase C substrate of platelets 总被引:23,自引:0,他引:23
M Tyers R A Rachubinski M I Stewart A M Varrichio R G Shorr R J Haslam C B Harley 《Nature》1988,333(6172):470-473
In platelets, agonists that stimulate phosphoinositide turnover cause the rapid phosphorylation of a protein of apparent relative molecular mass (Mr) 40-47,000, called P47, by protein kinase C (PKC). Diverse identities have been ascribed to P47 including lipocortin, inositol 1,4,5-trisphosphate 5-phosphomonoesterase, pyruvate dehydrogenase alpha subunit and an actin regulatory protein. We have isolated human P47 clones by immunological screening of a lambda gt11 complementary DNA library from HL-60 cells, a human promyelocytic leukaemia cell line. P47 recombinants thus identified hybridized to a 3.0 kilobase (kb) messenger RNA in mature white blood cell lines; the same mRNA was induced in HL-60 cells during differentiation. A 1,050 base pair (bp) open reading frame that could encode a protein of Mr40,087 was confirmed by comparison with peptide sequences from platelet P47, and by expression of the putative recombinant P47 in E. coli and in vitro. The P47 sequence appears to have been conserved throughout vertebrate evolution, and is not similar to any other known sequence including human lipocortin and the alpha subunit of pyruvate dehydrogenase. The P47 protein contains a potential Ca2+-binding 'EF-hand' structure and a region that strongly resembles known PKC phosphorylation sites. 相似文献