全文获取类型
收费全文 | 109660篇 |
免费 | 4104篇 |
国内免费 | 49篇 |
专业分类
113813篇 |
出版年
2021年 | 755篇 |
2020年 | 593篇 |
2019年 | 749篇 |
2018年 | 1781篇 |
2017年 | 1918篇 |
2016年 | 3847篇 |
2015年 | 7235篇 |
2014年 | 6984篇 |
2013年 | 7284篇 |
2012年 | 6768篇 |
2011年 | 4072篇 |
2010年 | 3402篇 |
2009年 | 3136篇 |
2008年 | 1998篇 |
2007年 | 1881篇 |
2006年 | 1881篇 |
2005年 | 7608篇 |
2004年 | 6361篇 |
2003年 | 4491篇 |
2002年 | 2005篇 |
2001年 | 1574篇 |
2000年 | 827篇 |
1999年 | 1847篇 |
1998年 | 618篇 |
1992年 | 2086篇 |
1991年 | 2140篇 |
1990年 | 2189篇 |
1989年 | 2088篇 |
1988年 | 2032篇 |
1987年 | 1895篇 |
1986年 | 1700篇 |
1985年 | 1716篇 |
1984年 | 1183篇 |
1983年 | 891篇 |
1982年 | 530篇 |
1981年 | 476篇 |
1979年 | 1109篇 |
1978年 | 800篇 |
1977年 | 643篇 |
1976年 | 652篇 |
1975年 | 908篇 |
1974年 | 1049篇 |
1973年 | 1038篇 |
1972年 | 972篇 |
1971年 | 952篇 |
1970年 | 840篇 |
1969年 | 858篇 |
1968年 | 754篇 |
1967年 | 768篇 |
1966年 | 595篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Simultaneous Display of Multiple Foreign Peptides in the FliD Capping and FliC Filament Proteins of the Escherichia coli Flagellum 下载免费PDF全文
Katariina Majander Timo K. Korhonen Benita Westerlund-Wikstr?m 《Applied microbiology》2005,71(8):4263-4268
The bacterial flagellum is composed of more than 20 different proteins. The filament, which constitutes the major extracellular part of the flagellum, is built up of approximately 20,000 FliC molecules that assemble at the growing distal end of the filament. A capping structure composed of five FliD molecules located at the tip of the filament promotes polymerization of FliC. Lack of FliD leads to release of the subunits into the growth medium. We show here that FliD can be successfully used in bacterial surface display. We tested various insertion sites in the capping protein, and the optimal region for display was at the variable region in FliD. Deletion and/or insertion at other sites resulted in decreased formation of flagella. We further developed the technique into a multihybrid display system in which three foreign peptides are simultaneously expressed within the same flagellum, i.e., D repeats of FnBPA from Staphylococcus aureus at the tip and fragments of YadA from Yersinia enterocolitica as well as SlpA from Lactobacillus crispatus along the filament. This technology can have biotechnological applications, e.g., in simultaneous delivery of several effector molecules. 相似文献
102.
L V Loskutova M A Gilinski? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1987,37(6):1070-1074
Character of conditioned reaction of passive avoidance was analyzed in Wistar line male rats after neurochemical destruction of terminal dopaminergic fields of the amygdalar complex. 6-hydroxydopamine was bilaterally administered to the central nucleus of the amygdalar complex after preliminary treating with desmethylimipramine for selective destruction of dopaminergic terminals. Lowering of dopamine level in the amygdalar complex led to a weakening of reproduction and to prolongation of spontaneous extinction of conditioned reaction. Features of conditioned reaction are highly similar to the effect of latent inhibition connected with attention deficit. It is suggested that activity of terminal fields of the amygdalar complex is one of the mechanisms providing for attention and intensifying selection of information in learning. 相似文献
103.
104.
105.
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
106.
E. Cortés A.A. Kirk J.A. Goolsby P.J. Moran A.E. Racelis M.A. Marcos-García 《Biocontrol Science and Technology》2011,21(11):1369-1373
Arundo donax L. (Poaceae) is native to Mediterranean Europe and invasive in the Rio Grande Basin of North America. Rhizomes from nine sites in France and Spain infested with a candidate control agent, the armoured scale Rhizaspidiotus donacis (Hemiptera: Diaspididae) weighed 50% less than those from nine sites without scale. 相似文献
107.
108.
Late Quaternary climate change,relict populations and present‐day refugia in the northern Atacama Desert: a case study from Quebrada La Higuera (18° S) 下载免费PDF全文
109.
110.
Nathalie Jeanray Rapha?l Marée Benoist Pruvot Olivier Stern Pierre Geurts Louis Wehenkel Marc Muller 《PloS one》2015,10(1)
Zebrafish is increasingly used to assess biological properties of chemical substances and thus is becoming a specific tool for toxicological and pharmacological studies. The effects of chemical substances on embryo survival and development are generally evaluated manually through microscopic observation by an expert and documented by several typical photographs. Here, we present a methodology to automatically classify brightfield images of wildtype zebrafish embryos according to their defects by using an image analysis approach based on supervised machine learning. We show that, compared to manual classification, automatic classification results in 90 to 100% agreement with consensus voting of biological experts in nine out of eleven considered defects in 3 days old zebrafish larvae. Automation of the analysis and classification of zebrafish embryo pictures reduces the workload and time required for the biological expert and increases the reproducibility and objectivity of this classification. 相似文献