全文获取类型
收费全文 | 856028篇 |
免费 | 100832篇 |
国内免费 | 336篇 |
专业分类
957196篇 |
出版年
2016年 | 9834篇 |
2015年 | 13330篇 |
2014年 | 15850篇 |
2013年 | 22313篇 |
2012年 | 24938篇 |
2011年 | 25528篇 |
2010年 | 17227篇 |
2009年 | 16084篇 |
2008年 | 23003篇 |
2007年 | 24176篇 |
2006年 | 22576篇 |
2005年 | 21747篇 |
2004年 | 21725篇 |
2003年 | 20721篇 |
2002年 | 20206篇 |
2001年 | 35118篇 |
2000年 | 35493篇 |
1999年 | 28524篇 |
1998年 | 10470篇 |
1997年 | 10962篇 |
1996年 | 10489篇 |
1995年 | 10033篇 |
1994年 | 9857篇 |
1993年 | 9810篇 |
1992年 | 24531篇 |
1991年 | 24371篇 |
1990年 | 23929篇 |
1989年 | 23250篇 |
1988年 | 21869篇 |
1987年 | 21065篇 |
1986年 | 19788篇 |
1985年 | 19792篇 |
1984年 | 16713篇 |
1983年 | 14660篇 |
1982年 | 11394篇 |
1981年 | 10442篇 |
1980年 | 9966篇 |
1979年 | 16387篇 |
1978年 | 12948篇 |
1977年 | 11935篇 |
1976年 | 11393篇 |
1975年 | 12468篇 |
1974年 | 13454篇 |
1973年 | 13186篇 |
1972年 | 12435篇 |
1971年 | 10981篇 |
1970年 | 9718篇 |
1969年 | 9323篇 |
1968年 | 8672篇 |
1967年 | 7511篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
201.
202.
203.
204.
ABSTRACT The phrase persistent vulnerability reflects the enduring relationship of the rural population in Ceará with a highly variable climate. Persistence underscores the historical and unyielding nature of this vulnerability. Yet contrary to once-catastrophic rates of mortality etched in a public consciousness, no one dies from severe droughts and few people flee them as in the past. Government relief and social transfers have become the institutionalized form of adaptation, giving way to the counterintuitive reality that drought stabilizes the food and income supply for poor people. We analyze how maladaptive risk reduction, which is embedded in clientilistic social relations, undermines resilience, and we examine pathways toward a more sustainable adaptive relationship. 相似文献
205.
Ffh is a component of a bacterial ribonucleoprotein complex homologous to the signal recognition particle (SRP) of eukaryotes. It comprises three domains that mediate both binding to the hydrophobic signal sequence of the nascent polypeptide and the GTP-dependent interaction of Ffh with a structurally homologous GTPase of the SRP receptor. The X-ray structures of the two-domain 'NG' GTPase of Ffh in complex with Mg2+GDP and GDP have been determined at 2.0 A resolution. The structures explain the low nucleotide affinity of Ffh and locate two regions of structural mobility at opposite sides of the nucleotide-binding site. One of these regions includes highly conserved sequence motifs that presumably contribute to the structural trigger signaling the GTP-bound state. The other includes the highly conserved interface between the N and G domains, and supports the hypothesis that the N domain regulates or signals the nucleotide occupancy of the G domain. 相似文献
206.
E Giannazzo F Licata G Li Volsi G Mio F Santangelo M Scivoli 《Bollettino della Società italiana di biologia sperimentale》1992,68(11):677-683
A computer-assisted analysis of the spatial distribution of neurons having homogeneous characteristics is described in this paper. The camera lucida drawings of sections of a brain nucleus and the points representing the neurons labeled on the basis of a specific behavior of discharge rates were digitized on a personal computer Amiga 2000 or IBM compatible. Our software provided: a) the computerized, stereotaxically oriented reconstruction of the stored sections and of the plotted neurons; b) the identification within each section of the mass center (MC) of the units sharing a given behavior and of the area where the density of such neurons was maximal (MDA). The routine was tested on the spatial distribution of neuronal responses to serotonin in the lateral vestibular nucleus. 相似文献
207.
208.
209.
1L-myo-Inositol-1-phosphatase, an enzyme purified from brain tissues, catalyzes the dephosphorylation of 1L-myo-inositol 1-phosphate. This enzyme has become the subject of intense research interest, since myo-inositol is needed for the resynthesis of phosphatidylinositol. We have developed a sensitive fluorometric assay for detecting the activity of 1L-myo-inositol-1-phosphatase. The assay is based on o-aminobenzoyl beta-glycerophosphate fluorescence, according to the following principles: (I) The fluorescence yield of o-aminobenzoyl beta-glycerophosphate is increased by 2.75-fold in the presence of saturating concentrations of bovine serum albumin. (II) o-Aminobenzoyl beta-glycerophosphate has the same fluorescence yield as o-aminobenzoyl glycerol, but the latter does not bind to bovine serum albumin. (III) Dephosphorylation of the substrate, catalyzed by the monophosphatase, makes less o-aminobenzoyl beta-glycerophosphate available for binding to bovine serum albumin, thereby producing a decrease in the fluorescence intensity. 相似文献
210.