全文获取类型
收费全文 | 13921篇 |
免费 | 1393篇 |
国内免费 | 17篇 |
出版年
2022年 | 84篇 |
2021年 | 138篇 |
2020年 | 89篇 |
2019年 | 146篇 |
2018年 | 167篇 |
2017年 | 179篇 |
2016年 | 297篇 |
2015年 | 460篇 |
2014年 | 543篇 |
2013年 | 664篇 |
2012年 | 900篇 |
2011年 | 902篇 |
2010年 | 630篇 |
2009年 | 557篇 |
2008年 | 799篇 |
2007年 | 831篇 |
2006年 | 766篇 |
2005年 | 794篇 |
2004年 | 771篇 |
2003年 | 784篇 |
2002年 | 788篇 |
2001年 | 221篇 |
2000年 | 190篇 |
1999年 | 200篇 |
1998年 | 231篇 |
1997年 | 164篇 |
1996年 | 154篇 |
1995年 | 154篇 |
1994年 | 153篇 |
1993年 | 145篇 |
1992年 | 164篇 |
1991年 | 135篇 |
1990年 | 114篇 |
1989年 | 139篇 |
1988年 | 110篇 |
1987年 | 113篇 |
1986年 | 127篇 |
1985年 | 110篇 |
1984年 | 125篇 |
1983年 | 123篇 |
1982年 | 127篇 |
1981年 | 146篇 |
1980年 | 123篇 |
1979年 | 86篇 |
1978年 | 87篇 |
1977年 | 67篇 |
1976年 | 67篇 |
1974年 | 69篇 |
1973年 | 63篇 |
1972年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
L B Andersen P Henckel B Saltin 《European journal of applied physiology and occupational physiology》1987,56(1):74-82
A random sample of schoolchildren, 119 boys and 153 girls, was tested in the fall of 1983. The data presented here are anthropometric data (height, weight, fat % and vital capacity) and oxygen uptake directly measured on a bicycle ergometer. The mean height and weight for boys were 179.1 cm and 67.7 kg, and those for girls were 168.0 cm and 59.6 kg. The mean fat content was 9.1% for boys and 19.1% for girls, and their mean vital capacities were 4.91 and 3.61 respectively. The boys had a high maximal oxygen uptake (51.7 ml X kg-1 X min-1) showing no reduction over the age span studied. The girls' maximal oxygen uptake was lower (overall mean 40.0 ml X kg-1 X min-1) with a small reduction from 16 to 19 years of age. When comparing maximal oxygen uptake per kg lean body mass in the two sexes, the boys had 18.4% higher values than the girls, indicating that girls of this age have the lower fitness level. The results of maximal aerobic power measurement in the boys compare well with findings from other investigations using direct measurements, indicating that the fitness of teenage boys is kept at a high level. Comparable data from various countries for girls show different pictures, but it appears that in general they have a low fitness level. 相似文献
2.
3.
4.
Eugénie Bassères Giuseppe Coppotelli Thorsten Pfirrmann Jens B. Andersen Maria Masucci Teresa Frisan 《Cellular microbiology》2010,12(11):1622-1633
Invasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C‐terminal hydrolase UCH‐L1 that promotes the invasion of epithelial cells by Listeria monocytogenes and Salmonella enterica. Knockdown of UCH‐L1 reduced the uptake of both bacteria, while expression of the catalytically active enzyme promoted efficient internalization in the UCH‐L1‐negative HeLa cell line. The entry of L. monocytogenes involves binding to the receptor tyrosine kinase Met, which leads to receptor phosphorylation and ubiquitination. UCH‐L1 controls the early membrane‐associated events of this triggering cascade since knockdown was associated with altered phosphorylation of the c‐cbl docking site on Tyr1003, reduced ubiquitination of the receptor and altered activation of downstream ERK1/2‐ and AKT‐dependent signalling in response to the natural ligand Hepatocyte Growth Factor (HGF). The regulation of cytoskeleton dynamics was further confirmed by the induction of actin stress fibres in HeLa expressing the active enzyme but not the catalytic mutant UCH‐L1C90S. These findings highlight a previously unrecognized involvement of the ubiquitin cycle in bacterial entry. UCH‐L1 is highly expressed in malignant cells that may therefore be particularly susceptible to invasion by bacteria‐based drug delivery systems. 相似文献
5.
The gorgoniid Eugorgia is exclusively an eastern Pacific genus. It has a wide geographic and bathymetric range of distribution, found from California to Perú and extends down to 65 m deep. Two new species are herein described. The morphological characters were analyzed and illustrated by light and scanning electron microscopy. Eugorgia beebei
sp. n. can be distinguished by its white, ascending, sparse colony growth. Eugorgia mutabilis
sp. n. can be distinguished by its white colony that changes color after collection, and the conspicuous sharp-crested disc sclerites. From a morphological point of view the new species are related to the daniana-group, the rubens-group and the siedenburgae-group of Eugorgia; their affiliations, and the proposal of a new group are discussed. These new species increases the number of species in the genus to 15, and contribute to the knowledge of the eastern Pacific octocoral biodiversity. 相似文献
6.
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
7.
8.
Nimra Khan Dylan Pelletier Thomas S. McAlear Nathalie Croteau Simon Veyron Andrew N. Bayne Corbin Black Muneyoshi Ichikawa Ahmad Abdelzaher Zaki Khalifa Sami Chaaban Igor Kurinov Gary Brouhard Susanne Bechstedt Khanh Huy Bui Jean-François Trempe 《Structure (London, England : 1993)》2021,29(6):572-586.e6
- Download : Download high-res image (220KB)
- Download : Download full-size image
9.
We present a fast, reliable and inexpensive restriction-free cloning method for seamless DNA insertion into any plasmid without sequence limitation. Exponential megapriming PCR (EMP) cloning requires two consecutive PCR steps and can be carried out in one day. We show that EMP cloning has a higher efficiency than restriction-free (RF) cloning, especially for long inserts above 2.5 kb. EMP further enables simultaneous cloning of multiple inserts. 相似文献
10.