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In the course of a freeze-cleave study on intercellular junctions in the regenerating rat liver, we observed an unusual array of intramembranous particles located in regions of contact between endothelial cells lining the hepatic sinusoids. These arrays were characterized by an accumulation of particles which resembled a zonula occludens in their linear deployment but differed in that the contact regions were composed of individual particles which remained separated from each other by regular particle-free intervals. 相似文献
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A 145-base pair DNA sequence that positions itself precisely and asymmetrically on the nucleosome core. 总被引:16,自引:2,他引:14 下载免费PDF全文
A 145-bp DNA sequence, cloned from Escherichia coli, was reconstituted into nucleosome core particles by a number of methods. The behaviour of the resulting complex upon sucrose gradient sedimentation and nucleoprotein gel electrophoresis closely resembled that of control bulk nucleosome core particles. DNase I digestion of the 32P-end-labelled complex revealed the 10-bp periodicity of cleavages expected for DNA bound on a histone surface. The narrow cleavage sites observed (1 bp wide) imply that the sequence occupies a single preferred position on the nucleosome core, accurate to the level of single base pairs. By relating the digestion pattern observed to the pattern of site protection found for random sequence nucleosomes, the DNA position was found to be offset by 17 bp from that in the normal core particle. A number of experiments argue against the involvement of length or end effects and suggest that it is some feature of the DNA sequence itself that determines this precise positioning of DNA on the nucleosome. 相似文献
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W. Rushton Parker 《BMJ (Clinical research ed.)》1900,2(2072):754-755
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We test the hypothesis that polymorphisms of the brain regulator genes MCPH1 and ASPM contribute to variations in human brain size and its correlates. We measured general mental ability, head circumference and social intelligence in 644 Canadian adults (496 Caucasians, 36 Orientals, 84 Mixed Race/Other and 28 Blacks; 257 men and 387 women). The gene polymorphisms were assessed from buccal DNA; mental ability by Wonderlic Personnel Test and Multidimensional Aptitude Battery; head circumference by stretchless tape; and social intelligence by prosocial attitude questionnaires. Although all measures were construct valid and the allele frequencies showed expected population differences, no relationship was found between the genes and any of the criteria. Among Caucasian 18-25 year olds, for example, the two mental ability tests correlated with each other (r=0.78, N=476, p<0.001), with head circumference (r=0.17, N=182, p<0.05) and with prosocial attitudes (r=0.23, N=182, p<0.001). 相似文献
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Industrial Food Animal Production and Global Health Risks: Exploring the Ecosystems and Economics of Avian Influenza 总被引:2,自引:0,他引:2
Jessica H. Leibler Joachim Otte David Roland-Holst Dirk U. Pfeiffer Ricardo Soares Magalhaes Jonathan Rushton Jay P. Graham Ellen K. Silbergeld 《EcoHealth》2009,6(1):58-70
Many emerging infectious diseases in human populations are associated with zoonotic origins. Attention has often focused on
wild animal reservoirs, but most zoonotic pathogens of recent concern to human health either originate in, or are transferred
to, human populations from domesticated animals raised for human consumption. Thus, the ecological context of emerging infectious
disease comprises two overlapping ecosystems: the natural habitats and populations of wild animals, and the anthropogenically
controlled habitats and populations of domesticated species. Intensive food animal production systems and their associated
value chains dominate in developed countries and are increasingly important in developing countries. These systems are characterized
by large numbers of animals being raised in confinement with high throughput and rapid turnover. Although not typically recognized
as such, industrial food animal production generates unique ecosystems—environments that may facilitate the evolution of zoonotic
pathogens and their transmission to human populations. It is often assumed that confined food animal production reduces risks
of emerging zoonotic diseases. This article provides evidence suggesting that these industrial systems may increase animal
and public health risks unless there is recognition of the specific biosecurity and biocontainment challenges of the industrial
model. Moreover, the economic drivers and constraints faced by the industry and its participants must be fully understood
in order to inform preventative policy. In order to more effectively reduce zoonotic disease risk from industrial food animal
production, private incentives for the implementation of biosecurity must align with public health interests. 相似文献