全文获取类型
收费全文 | 348篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 54篇 |
现状及发展 | 78篇 |
研究方法 | 25篇 |
综合类 | 186篇 |
自然研究 | 6篇 |
出版年
2017年 | 3篇 |
2016年 | 3篇 |
2013年 | 3篇 |
2012年 | 17篇 |
2011年 | 24篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 9篇 |
1965年 | 3篇 |
1960年 | 1篇 |
1959年 | 16篇 |
1958年 | 30篇 |
1957年 | 22篇 |
1956年 | 10篇 |
1955年 | 15篇 |
1954年 | 23篇 |
1948年 | 7篇 |
1947年 | 3篇 |
排序方式: 共有350条查询结果,搜索用时 0 毫秒
251.
252.
Dragon F Gallagher JE Compagnone-Post PA Mitchell BM Porwancher KA Wehner KA Wormsley S Settlage RE Shabanowitz J Osheim Y Beyer AL Hunt DF Baserga SJ 《Nature》2002,417(6892):967-970
Although the U3 small nucleolar RNA (snoRNA), a member of the box C/D class of snoRNAs, was identified with the spliceosomal small nuclear RNAs (snRNAs) over 30 years ago, its function and its associated protein components have remained more elusive. The U3 snoRNA is ubiquitous in eukaryotes and is required for nucleolar processing of pre-18S ribosomal RNA in all organisms where it has been tested. Biochemical and genetic analyses suggest that U3 pre-rRNA base-pairing interactions mediate endonucleolytic pre-rRNA cleavages. Here we have purified a large ribonucleoprotein (RNP) complex from Saccharomyces cerevisiae that contains the U3 snoRNA and 28 proteins. Seventeen new proteins (Utp1 17) and Rrp5 were present, as were ten known components. The Utp proteins are nucleolar and specifically associated with the U3 snoRNA. Depletion of the Utp proteins impedes production of the 18S rRNA, indicating that they are part of the active pre-rRNA processing complex. On the basis of its large size (80S; calculated relative molecular mass of at least 2,200,000) and function, this complex may correspond to the terminal knobs present at the 5' ends of nascent pre-rRNAs. We have termed this large RNP the small subunit (SSU) processome. 相似文献
253.
Climate change: Regional warming and malaria resurgence 总被引:1,自引:0,他引:1
Patz JA Hulme M Rosenzweig C Mitchell TD Goldberg RA Githeko AK Lele S McMichael AJ Le Sueur D 《Nature》2002,420(6916):627-8; discussion 628
254.
Leighton PA Mitchell KJ Goodrich LV Lu X Pinson K Scherz P Skarnes WC Tessier-Lavigne M 《Nature》2001,410(6825):174-179
The search to understand the mechanisms regulating brain wiring has relied on biochemical purification approaches in vertebrates and genetic approaches in invertebrates to identify molecular cues and receptors for axon guidance. Here we describe a phenotype-based gene-trap screen in mice designed for the large-scale identification of genes controlling the formation of the trillions of connections in the mammalian brain. The method incorporates an axonal marker, which helps to identify cell-autonomous mechanisms in axon guidance, and has generated a resource of mouse lines with striking patterns of axonal labelling, which facilitates analysis of the normal wiring diagram of the brain. Studies of two of these mouse lines have identified an in vivo guidance function for a vertebrate transmembrane semaphorin, Sema6A, and have helped re-evaluate that of the Eph receptor EphA4. 相似文献
255.
256.
Mary R. Mitchell B. L. Ginsborg C. R. House 《Cellular and molecular life sciences : CMLS》1980,36(1):98-99
Summary After incubation in calcium-free solutions containing cobalt, the readmission of calcium caused prolonged but reversible hyperpolarization of acinar cells of cockroach salivary glands and prolonged fluid secretion. It is suggested that cobalt treatment increases the permeability of the acinar cell membrane to calcium.Acknowledgments. We are indebted to the Medical Research Council for support. 相似文献
257.
258.
259.
260.