全文获取类型
收费全文 | 764545篇 |
免费 | 82088篇 |
国内免费 | 7655篇 |
出版年
2021年 | 10020篇 |
2019年 | 8203篇 |
2018年 | 9991篇 |
2017年 | 8686篇 |
2016年 | 12333篇 |
2015年 | 17813篇 |
2014年 | 20660篇 |
2013年 | 26518篇 |
2012年 | 30645篇 |
2011年 | 30175篇 |
2010年 | 19721篇 |
2009年 | 17766篇 |
2008年 | 24716篇 |
2007年 | 24590篇 |
2006年 | 22959篇 |
2005年 | 21241篇 |
2004年 | 20766篇 |
2003年 | 19518篇 |
2002年 | 18631篇 |
2001年 | 28952篇 |
2000年 | 28859篇 |
1999年 | 23421篇 |
1998年 | 9192篇 |
1997年 | 9501篇 |
1996年 | 9027篇 |
1995年 | 8465篇 |
1994年 | 8161篇 |
1993年 | 7937篇 |
1992年 | 19365篇 |
1991年 | 19160篇 |
1990年 | 18519篇 |
1989年 | 17904篇 |
1988年 | 16588篇 |
1987年 | 15693篇 |
1986年 | 14728篇 |
1985年 | 14795篇 |
1984年 | 12194篇 |
1983年 | 10452篇 |
1982年 | 8056篇 |
1981年 | 7324篇 |
1979年 | 11532篇 |
1978年 | 9144篇 |
1977年 | 8417篇 |
1976年 | 7862篇 |
1975年 | 8898篇 |
1974年 | 9800篇 |
1973年 | 9570篇 |
1972年 | 8566篇 |
1971年 | 7955篇 |
1970年 | 6876篇 |
排序方式: 共有10000条查询结果,搜索用时 388 毫秒
941.
942.
943.
944.
To clarify the mechanisms of Nosema ceranae parasitism, we deep-sequenced both honey bee host and parasite mRNAs throughout a complete 6-day infection cycle. By time-series analysis, 1122 parasite genes were significantly differently expressed during the reproduction cycle, clustering into 4 expression patterns. We found reactive mitochondrial oxygen species modulator 1 of the host to be significantly down regulated during the entire infection period. Our data support the hypothesis that apoptosis of honey bee cells was suppressed during infection. We further analyzed genome-wide genetic diversity of this parasite by comparing samples collected from the same site in 2007 and 2013. The number of SNP positions per gene and the proportion of non-synonymous substitutions per gene were significantly reduced over this time period, suggesting purifying selection on the parasite genome and supporting the hypothesis that a subset of N. ceranae strains might be dominating infection. 相似文献
945.
The structure of the tightly bound complex of the globular myosin head with F-actin is the key to understanding important details of the mechanism of how the actin-myosin motor functions. The current notion on this complex is based on the docking of known atomic structures of constituent proteins into low-resolution electron-density maps. The atomic structure of the complex was refined by the molecular mechanics method, which consists in minimizing the energy of molecular interaction and which makes it possible to optimize not only the relative position of protein backbones as rigid bodies, but also the position of side chains on the protein interface. The structure calculated using ICM-Pro software, on the one hand, is close to the model obtained using electron microscopy; on the other hand, it ensures the best calculated interaction energy and accounts for the results of mutagenesis experiments. On the basis of the structure obtained, we can suggest the molecular mechanisms underlying the actin-activated release of ATP hydrolysis products from myosin and the decrease in the affinity of myosin for actin upon binding of nucleotides. 相似文献
946.
947.
The morphology of dissociated single cerebellar Purkinje cells obtained from wild-type P1 CD1 mice was assessed in the absence
and in the presence of glia. A dedicated noninvasive technique based on optical microscopy was developed. Image processing
algorithms were implemented to extract metrical features characterizing cell structure and dendritic arborization. The morphological
features were analyzed in order to identify quantitative differences in Purkinje cell morphology due to interactions with
astrocytes. 相似文献
948.
D. Padilla F. Acosta J. A. García F. Real Jose R. Vivas 《Archives of microbiology》2009,191(3):191-198
Hafnia alvei, a Gram negative bacillus related to the Enterobacteriaceae family, is considered an opportunistic pathogen of several animal species and humans. In this communication, we describe
fimbrial-like structures from different strains of H. alvei that cannot be easily ascribed to any of the previously reported fimbrial types in this species (type I or type III). Polymerase
chain reaction (PCR) and immunofluorescence assays were carried out to study fimbriae and flagella in H. alvei strains isolated from different sources. No correlation between the results obtained by PCR and those obtained by phenotypic
methods were found, and the antibodies used gave cross or different recognition patterns of the surface structures present
in these strains. We report as well that strain and growth temperature influence fimbriation and expression of flagella in
human and animal isolates of H. alvei. This study also indicates that the absence of fimbriae have a significant positive influence on the initial adhesion of
H. alvei to human epithelial cells. 相似文献
949.
Ronald J. Roberts H. J. Ball A. L. S. Munro W. M. Shearer 《Journal of fish biology》1971,3(2):221-224
Fourteen fresh run salmon Satmo salar L. with early extant lesions of ulcerative dermal necrosis (UDN) were kept in separate tanks and treated with zinc free malachite green. Ten of the fish were held at 10° C and 4 at 2° C. The treatment precluded infection with Saprolegnia fungus and allowed natural resolution of the lesions. There was a marked difference in rate of healing between warm and cold water conditions.
Histological examination of healing lesions at different stages showed that there was a primary invasion of cuboidal epithelium over the collagen scar followed by a phase of disorganized proliferation which eventually organized itself into normal epithelium. Melanocytes were very obvious in the dermis of healing lesions. 相似文献
Histological examination of healing lesions at different stages showed that there was a primary invasion of cuboidal epithelium over the collagen scar followed by a phase of disorganized proliferation which eventually organized itself into normal epithelium. Melanocytes were very obvious in the dermis of healing lesions. 相似文献
950.