全文获取类型
收费全文 | 87144篇 |
免费 | 2323篇 |
国内免费 | 51篇 |
出版年
2018年 | 916篇 |
2017年 | 1091篇 |
2016年 | 2845篇 |
2015年 | 6220篇 |
2014年 | 5814篇 |
2013年 | 5595篇 |
2012年 | 4816篇 |
2011年 | 2068篇 |
2010年 | 2120篇 |
2009年 | 2113篇 |
2008年 | 673篇 |
2007年 | 627篇 |
2006年 | 699篇 |
2005年 | 6757篇 |
2004年 | 5428篇 |
2003年 | 3680篇 |
2002年 | 1251篇 |
2001年 | 1132篇 |
2000年 | 375篇 |
1999年 | 1534篇 |
1998年 | 387篇 |
1997年 | 214篇 |
1992年 | 1961篇 |
1991年 | 2056篇 |
1990年 | 2127篇 |
1989年 | 2041篇 |
1988年 | 1980篇 |
1987年 | 1855篇 |
1986年 | 1659篇 |
1985年 | 1697篇 |
1984年 | 1156篇 |
1983年 | 895篇 |
1982年 | 513篇 |
1981年 | 483篇 |
1980年 | 422篇 |
1979年 | 1129篇 |
1978年 | 824篇 |
1977年 | 653篇 |
1976年 | 679篇 |
1975年 | 909篇 |
1974年 | 1031篇 |
1973年 | 1060篇 |
1972年 | 994篇 |
1971年 | 963篇 |
1970年 | 858篇 |
1969年 | 873篇 |
1968年 | 762篇 |
1967年 | 789篇 |
1966年 | 607篇 |
1965年 | 462篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The present study has shown that on the level of the parasitic system the epidemic process is a biological system, wherein the host population serves as the internal regulator, the mechanism of transmission serves as the external regulator and the parasite population, as the regulated object. The biological regulating mechanisms of the epidemic process have fundamental differences in the groups of infectious with various mechanisms of transmission, and the specific nature of the mechanism of transmission determines the peculiar features of the biological mechanism which governs the self-regulation of the epidemic process. In contrast, on a higher level of the organization of the epidemic process, i. e. on the level of the socio-ecological system, the epidemic process is a biosocial system, wherein the human society serves as the regulator, the parasitic system serves as the regulated object and the mechanism of transmission plays the role of the filter which determines the scope of social factors, most important in the regulation of the epidemic process in a given infection. The spontaneous regulation of the epidemic process is the freed forward channel from the regulator to the regulated object, and the controlled regulation is the feedback channel. 相似文献
82.
83.
Jens Blechert Eva Naumann Julian Schmitz Beate M. Herbert Brunna Tuschen-Caffier 《PloS one》2014,9(1)
Many individuals restrict their food intake to prevent weight gain. This restriction has both homeostatic and hedonic effects but their relative contribution is currently unclear. To isolate hedonic effects of food restriction, we exposed regular chocolate eaters to one week of chocolate deprivation but otherwise regular eating. Before and after this hedonic deprivation, participants viewed images of chocolate and images of high-calorie but non-chocolate containing foods, while experiential, behavioral and eyeblink startle responses were measured. Compared to satiety, hedonic deprivation triggered increased chocolate wanting, liking, and chocolate consumption but also feelings of frustration and startle potentiation during the intertrial intervals. Deprivation was further characterized by startle inhibition during both chocolate and food images relative to the intertrial intervals. Individuals who responded with frustration to the manipulation and those who scored high on a questionnaire of impulsivity showed more relative startle inhibition. The results reveal the profound effects of hedonic deprivation on experiential, behavioral and attentional/appetitive response systems and underscore the role of individual differences and state variables for startle modulation. Implications for dieting research and practice as well as for eating and weight disorders are discussed. 相似文献
84.
Protoplasts of Schizosaccharomyces pombe, grown on a rich nutrient medium, were treated with a peptide factor isolated from cultures of the protozoan Tetrahymena pyriformis. The peptide factor is known to inhibit RNA synthesis in Tetrahymena. It has now been shown that the peptide factor also inhibits RNA synthesis in yeast protoplasts without affecting protein synthesis. 相似文献
85.
86.
87.
88.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells. 相似文献
89.
H Zitzer H H H?nck D B?chner D Richter H J Kreienkamp 《The Journal of biological chemistry》1999,274(46):32997-33001
By using the yeast two-hybrid system we identified a novel protein from the human brain interacting with the C terminus of somatostatin receptor subtype 2. This protein termed somatostatin receptor interacting protein is characterized by a novel domain structure, consisting of six N-terminal ankyrin repeats followed by SH3 and PDZ domains, several proline-rich regions, and a C-terminal sterile alpha motif. It consists of 2185 amino acid residues encoded by a 9-kilobase pair mRNA; several splice variants have been detected in human and rat cDNA libraries. Sequence comparison suggests that the novel multidomain protein, together with cortactin-binding protein, forms a family of cytoskeletal anchoring proteins. Fractionation of rat brain membranes indicated that somatostatin receptor interacting protein is enriched in the postsynaptic density fraction. The interaction of somatostatin receptor subtype 2 with its interacting protein was verified by overlay assays and coimmunoprecipitation experiments from transfected human embryonic kidney cells. Somatostatin receptor subtype 2 and the interacting protein display a striking overlap of their expression patterns in the rat brain. Interestingly, in the hippocampus the mRNA for somatostatin receptor interacting protein was not confined to the cell bodies but was also observed in the molecular layer, suggesting a dendritic localization of this mRNA. 相似文献
90.