全文获取类型
收费全文 | 4621篇 |
免费 | 485篇 |
出版年
2021年 | 78篇 |
2020年 | 50篇 |
2019年 | 67篇 |
2018年 | 74篇 |
2017年 | 69篇 |
2016年 | 123篇 |
2015年 | 188篇 |
2014年 | 204篇 |
2013年 | 246篇 |
2012年 | 330篇 |
2011年 | 331篇 |
2010年 | 184篇 |
2009年 | 171篇 |
2008年 | 250篇 |
2007年 | 251篇 |
2006年 | 243篇 |
2005年 | 209篇 |
2004年 | 215篇 |
2003年 | 203篇 |
2002年 | 191篇 |
2001年 | 76篇 |
2000年 | 73篇 |
1999年 | 65篇 |
1998年 | 84篇 |
1997年 | 37篇 |
1996年 | 43篇 |
1995年 | 40篇 |
1994年 | 41篇 |
1993年 | 40篇 |
1992年 | 58篇 |
1991年 | 68篇 |
1990年 | 43篇 |
1989年 | 53篇 |
1988年 | 46篇 |
1987年 | 41篇 |
1986年 | 46篇 |
1985年 | 37篇 |
1984年 | 45篇 |
1983年 | 30篇 |
1982年 | 44篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 25篇 |
1974年 | 33篇 |
1973年 | 21篇 |
1967年 | 18篇 |
1966年 | 21篇 |
排序方式: 共有5106条查询结果,搜索用时 31 毫秒
41.
Bradley Scott Perrin Jr. Toshiko Ichiye 《Journal of biological inorganic chemistry》2013,18(6):599-608
The reduction potential of an electron transfer protein is one of its most important functional characteristics. Although the type of redox site and the protein fold are the major determinants of the reduction potential of a redox-active protein, its amino acid sequence may tune the reduction potential as well. Thus, homologous proteins can often be divided into different classes, with each class characterized by a biological function and a reduction potential. Site-specific mutagenesis of the sequence determinants of the differences in the reduction potential between classes should change the reduction potential of a protein in one class to that of the other class. Here, a procedure is presented that combines energetic and bioinformatic analysis of homologous proteins to identify sequence determinants that are also good candidates for site-specific mutations, using the [4Fe–4S] ferredoxins and the [4Fe–4S] high-potential iron–sulfur proteins as examples. This procedure is designed to guide site-specific mutations or more computationally expensive studies, such as molecular dynamics simulations. To make the procedure more accessible to the general scientific community, it is being implemented into CHARMMing, a Web-based portal, with a library of density functional theory results for the redox site that are used in the setting up of Poisson–Boltzmann continuum electrostatics calculations for the protein energetics. 相似文献
42.
E. J. Bradley 《BMJ (Clinical research ed.)》1934,1(3825):752-754
43.
44.
The influence of secretions from von Ebner's lingual salivaryglands on gustatory function was studied in the rat. Neurophysiologicaltaste responses elicited by chemical stimulation of the circumvallatepapilla were recorded from the glossopharyngeal nerve whileinitiating salivary secretion in the same papilla. Salivarysecretion from von Ebner's glands significantly reduced tasteresponses to stimulation of the circumvallate papilla with variouschemicals. However, the magnitude of the reduction in responsediffered depending on the taste stimulus used. The reductionin response due to salivary secretion was blocked by prior administrationof the parasympathetic antagonist, atropine. These results demonstratea direct effect of salivary secretion on taste responses andillustrate the close relationship between taste function andthe secretion of von Ebner's glands. 相似文献
45.
It has long been debated whether the mind consists of specialized and independently evolving modules, or whether and to what extent a general factor accounts for the variance in performance across different cognitive domains. In this study, we used a hierarchical Bayesian model to re-analyse individual level data collected on seven primate species (chimpanzees, bonobos, orangutans, gorillas, spider monkeys, brown capuchin monkeys and long-tailed macaques) across 17 tasks within four domains (inhibition, memory, transposition and support). Our modelling approach evidenced the existence of both a domain-specific factor and a species factor, each accounting for the same amount (17%) of the observed variance. In contrast, inter-individual differences played a minimal role. These results support the hypothesis that the mind of primates is (at least partially) modular, with domain-specific cognitive skills undergoing different evolutionary pressures in different species in response to specific ecological and social demands. 相似文献
46.
W. H. Bradley 《American journal of botany》1970,57(7):782-785
Four new species of algae and two kinds of fossil plant hairs are described from a rich oil shale bed of the mid-Eocene Green River Formation of Wyoming. Two of the algae belong to the Cyanophyceae and two to the Chlorophyceae. On the basis of their morphology alone, they are assigned to four new species among four genera, as follows: Symploca hedraia, sp. n.; Stigonema anchistina, sp. n.; Schizochlamys haywellensis, sp. n.; and Spirogyra wyomingia, sp. n. One kind of fossil plant hair is similar to those observed in organic sediments of an existing lake and identified with trichomes on the under surface of live oak leaves (Quercus virginiana). Assignment of the fossil trichomes to a taxon is not warranted at present. 相似文献
47.
D. J. Bradley E. A. Wood A. P. Larkins G. Galfre G. W. Butcher N. J. Brewin 《Planta》1988,173(2):149-160
Plant and bacterial antigens contributing to nodule development and symbiosis in pea (Pisum sativum L.) roots were identified after isolation of a set of monoclonal antibody (McAb)-producing hybridoma lines. Rats were immunised with the peribacteriod material released by mild osmotic shock treatment from membrane-enclosed bacteroids of Rhizobium leguminosarum bv. viceae. In order to diversify the range of McAb specificities, this material was either used as immunogen directly (method 1), or after immunodepletion of a set of glycoprotein and lipopolysaccharide antigens (method 2), or after deglycosylation (method 3). After fusion and screening of cloned hybridoma lines, these three immunisation methods gave respectively 4, 2 and 1 classes of McAb with unique antigen specificities. Ultrastructural immunogold localisation studies showed four different antigens to be present on peribacteriod and plasma membranes (identified by MAC 64, 202, 206 or 209); in addition, a glycoprotein of plant origin but present in the infection-thread matrix was identified by MAC 204. Although none of the epitopes recognised by these McAb was nodule-specific, several were found to be more abundant in extracts of nodule tissue than in uninfected roots (MAC 64, 202, 204, 206). Two McAb reacted with new bacterial antigens: MAC 203 identified a bacterial antigen expressed upon infection but not in free-living cultures of Rhizobium, and MAC 115 identified a bacterial polypeptide (55 kdaltons) that was present in both free-living and bacteroid forms. There were also some McAb of broader specificity that react with antigens present in both plant and bacterial cytoplasms.Abbreviations ELISA
enzyme-linked immunosorbent assay
- Ig
inmunoglobulin
- kDa
kilodalton
- LPS
lipopolysaccharide
- McAb
monoclonal antibody
- PBM
peribacteroid membrane
- SDS-PAGE
sodium dodecyl sulfate-polyacryl-amide gel electrophoresis
- TFMS
trifluoromethane sulfonic acid 相似文献
48.
49.
50.
Measurement of cardiac output by thermal dilution in man 总被引:7,自引:0,他引:7