全文获取类型
收费全文 | 28526篇 |
免费 | 2191篇 |
国内免费 | 9篇 |
学科分类
生物科学 | 30726篇 |
出版年
2022年 | 124篇 |
2021年 | 235篇 |
2020年 | 171篇 |
2019年 | 212篇 |
2018年 | 405篇 |
2017年 | 382篇 |
2016年 | 618篇 |
2015年 | 1064篇 |
2014年 | 1043篇 |
2013年 | 1509篇 |
2012年 | 1797篇 |
2011年 | 1815篇 |
2010年 | 1132篇 |
2009年 | 1000篇 |
2008年 | 1610篇 |
2007年 | 1681篇 |
2006年 | 1628篇 |
2005年 | 1560篇 |
2004年 | 1494篇 |
2003年 | 1414篇 |
2002年 | 1367篇 |
2001年 | 545篇 |
2000年 | 544篇 |
1999年 | 540篇 |
1998年 | 394篇 |
1997年 | 321篇 |
1996年 | 279篇 |
1995年 | 288篇 |
1994年 | 258篇 |
1993年 | 249篇 |
1992年 | 398篇 |
1991年 | 361篇 |
1990年 | 348篇 |
1989年 | 278篇 |
1988年 | 269篇 |
1987年 | 233篇 |
1986年 | 207篇 |
1985年 | 236篇 |
1984年 | 210篇 |
1983年 | 172篇 |
1982年 | 188篇 |
1981年 | 194篇 |
1980年 | 148篇 |
1979年 | 186篇 |
1978年 | 162篇 |
1977年 | 155篇 |
1976年 | 165篇 |
1975年 | 127篇 |
1974年 | 134篇 |
1973年 | 130篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
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
4.
A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing. 相似文献
5.
6.
The succinate dehydrogenase consists of only four subunits, all nuclearly encoded, and is part of both the respiratory chain and the Krebs cycle. Mutations in the four genes encoding the subunits of the mitochondrial respiratory chain succinate dehydrogenase have been recently reported in human and shown to be associated with a wide spectrum of clinical presentations. Although a comparatively rare deficiency in human, molecularly defined succinate dehydrogenase deficiency has already been found to cause encephalomyopathy in childhood, optic atrophy or tumor in adulthood. Because none of the typical housekeeping genes encoding this respiratory chain complex is known to present tissue-specific isoforms, the tissue-specific involvement represents a quite intriguing question, which is mostly addressed in this review. A differential impairment of electron flow through the respiratory chain, handling of oxygen, and/or metabolic blockade possibly associated with defects in the different subunits that can be advocated to account for tissue-specific involvement is discussed. 相似文献
7.
Calculation of effective diffusivities for biofilms and tissues. 总被引:2,自引:0,他引:2
In this study we describe a scheme for numerically calculating the effective diffusivity of cellular systems such as biofilms and tissues. This work extends previous studies in which we developed the macroscale representations of the transport equations for cellular systems based on the subcellular-scale transport and reaction processes. A finite-difference model is used to predict the effective diffusivity of a cellular system on the basis of the subcellular-scale geometry and transport parameters. The effective diffusivity is predicted for a complex three-dimensional structure that is based on laboratory observations of a biofilm, and these numerical predictions are compared with predictions from a simple analytical solution and with experimental data. Our results indicate that, under many practical circumstances, the simple analytical solution can be used to provide reasonable estimates of the effective diffusivity. 相似文献
8.
Olsvik Ørjan Myhre Stein Berdal Bjorn P. Fossum Kåre 《Acta veterinaria Scandinavica》1982,23(2):204-210
Enterotoxigenic reference strains of Staphylococcus aureus were cultivated in sterile whole and skim milk for 18 h at 37°G. Staphylococcal enterotoxin A, B, and C were detected directly in the milk by an enzyme linked immunosorbent assay (ELISA), sensitive down to 1 ng/ml. Enterotoxins in the range of 1 ng–20 µg/ml milk were detected without any concentration or extraction. Skim and whole milk were almost identical as medium for enterotoxin production. 相似文献
9.
Pierre Beuchet Laïla El kihel Michel Dherbomez Georges Charles Yves Letourneux 《Bioorganic & medicinal chemistry letters》1998,8(24):931
Δ7-5-Desaturase catalyses one of the last steps in ergosterol biosynthesis in fungi. Moreover Δ5-unsaturation is necessary for the sparking function. Synthesis of three pairs of C-6 epimeric cholestanol derivatives are described as potential growth inhibitors. Preliminary results suggest that 6β-aminocholestanol is a potent antifungal agent. 相似文献
10.
Corine Vialas Geneviève Pratviel Jean Bernadou Bernard Meunier 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):1061-1063
Abstract Mn TMPyP in the presence of sulfite/O2 catalyses the oxidation of dG into dIz as selectively but slower and less efficiently than in the presence of KHSO5. 相似文献