全文获取类型
收费全文 | 267篇 |
免费 | 0篇 |
专业分类
系统科学 | 1篇 |
理论与方法论 | 3篇 |
现状及发展 | 56篇 |
研究方法 | 24篇 |
综合类 | 172篇 |
自然研究 | 11篇 |
出版年
2017年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2012年 | 7篇 |
2011年 | 20篇 |
2010年 | 8篇 |
2009年 | 1篇 |
2008年 | 10篇 |
2007年 | 20篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1995年 | 2篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 1篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1970年 | 7篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1966年 | 6篇 |
1965年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 15 毫秒
261.
262.
263.
Replicating genotype-phenotype associations 总被引:1,自引:0,他引:1
NCI-NHGRI Working Group on Replication in Association Studies Chanock SJ Manolio T Boehnke M Boerwinkle E Hunter DJ Thomas G Hirschhorn JN Abecasis G Altshuler D Bailey-Wilson JE Brooks LD Cardon LR Daly M Donnelly P Fraumeni JF Freimer NB Gerhard DS Gunter C Guttmacher AE Guyer MS Harris EL Hoh J Hoover R Kong CA Merikangas KR Morton CC Palmer LJ Phimister EG Rice JP Roberts J Rotimi C Tucker MA Vogan KJ Wacholder S Wijsman EM Winn DM Collins FS 《Nature》2007,447(7145):655-660
264.
Peptide growth factors are multifunctional 总被引:64,自引:0,他引:64
The actions of many peptide growth factors include both stimulation and inhibition of cell proliferation, as well as effects unrelated to the control of cell growth. One peptide can have both stimulatory and inhibitory activity in a single cell, depending on the context of the other signal molecules present. 相似文献
265.
DNA coding for the opiate peptide beta-endorphin has been cloned into bacterial plasmids in such a way as to direct the synthesis of a hybrid beta-galactosidase/beta-endorphin protein. This hybrid protein can readily be cleaved in vitro to release biologically active beta-endorphin. 相似文献
266.
Prideaux GJ Long JA Ayliffe LK Hellstrom JC Pillans B Boles WE Hutchinson MN Roberts RG Cupper ML Arnold LJ Devine PD Warburton NM 《Nature》2007,445(7126):422-425
How well the ecology, zoogeography and evolution of modern biotas is understood depends substantially on knowledge of the Pleistocene. Australia has one of the most distinctive, but least understood, Pleistocene faunas. Records from the western half of the continent are especially rare. Here we report on a diverse and exceptionally well preserved middle Pleistocene vertebrate assemblage from caves beneath the arid, treeless Nullarbor plain of south-central Australia. Many taxa are represented by whole skeletons, which together serve as a template for identifying fragmentary, hitherto indeterminate, remains collected previously from Pleistocene sites across southern Australia. A remarkable eight of the 23 Nullarbor kangaroos are new, including two tree-kangaroos. The diverse herbivore assemblage implies substantially greater floristic diversity than that of the modern shrub steppe, but all other faunal and stable-isotope data indicate that the climate was very similar to today. Because the 21 Nullarbor species that did not survive the Pleistocene were well adapted to dry conditions, climate change (specifically, increased aridity) is unlikely to have been significant in their extinction. 相似文献
267.
A two-solar-mass neutron star measured using Shapiro delay 总被引:1,自引:0,他引:1
Neutron stars are composed of the densest form of matter known to exist in our Universe, the composition and properties of which are still theoretically uncertain. Measurements of the masses or radii of these objects can strongly constrain the neutron star matter equation of state and rule out theoretical models of their composition. The observed range of neutron star masses, however, has hitherto been too narrow to rule out many predictions of 'exotic' non-nucleonic components. The Shapiro delay is a general-relativistic increase in light travel time through the curved space-time near a massive body. For highly inclined (nearly edge-on) binary millisecond radio pulsar systems, this effect allows us to infer the masses of both the neutron star and its binary companion to high precision. Here we present radio timing observations of the binary millisecond pulsar J1614-2230 that show a strong Shapiro delay signature. We calculate the pulsar mass to be (1.97?±?0.04)M(⊙), which rules out almost all currently proposed hyperon or boson condensate equations of state (M(⊙), solar mass). Quark matter can support a star this massive only if the quarks are strongly interacting and are therefore not 'free' quarks. 相似文献