全文获取类型
收费全文 | 11387篇 |
免费 | 901篇 |
国内免费 | 8篇 |
专业分类
12296篇 |
出版年
2022年 | 62篇 |
2021年 | 106篇 |
2020年 | 56篇 |
2019年 | 92篇 |
2018年 | 132篇 |
2017年 | 151篇 |
2016年 | 203篇 |
2015年 | 356篇 |
2014年 | 392篇 |
2013年 | 526篇 |
2012年 | 637篇 |
2011年 | 671篇 |
2010年 | 451篇 |
2009年 | 455篇 |
2008年 | 600篇 |
2007年 | 690篇 |
2006年 | 641篇 |
2005年 | 640篇 |
2004年 | 623篇 |
2003年 | 626篇 |
2002年 | 641篇 |
2001年 | 155篇 |
2000年 | 142篇 |
1999年 | 183篇 |
1998年 | 224篇 |
1997年 | 167篇 |
1996年 | 146篇 |
1995年 | 151篇 |
1994年 | 134篇 |
1993年 | 158篇 |
1992年 | 185篇 |
1991年 | 141篇 |
1990年 | 153篇 |
1989年 | 118篇 |
1988年 | 99篇 |
1987年 | 99篇 |
1986年 | 75篇 |
1985年 | 119篇 |
1984年 | 106篇 |
1983年 | 82篇 |
1982年 | 99篇 |
1981年 | 85篇 |
1980年 | 80篇 |
1979年 | 78篇 |
1978年 | 62篇 |
1977年 | 76篇 |
1976年 | 69篇 |
1975年 | 48篇 |
1974年 | 49篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Véronique Lavoie Anne‐Elen Kernaleguen Guy Charron Nada Farhat Mariève Cossette Aida M. Mamarbachi Bruce G. Allen Eric Rhéaume Jean‐Claude Tardif 《Obesity (Silver Spring, Md.)》2011,19(4):722-728
Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen‐coated dishes. Three sub‐populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub‐populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub‐population. We also demonstrated that EPCs, particularly one sub‐population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub‐populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin. 相似文献
14.
We compared five different supports (Whatman paper filters Nos. 1, 5, and 40, nitrocellulose, and Nylon 66) for their suitability in the colony-immunoblot (CIB) technique. Results indicate that Whatman No. 5 filter paper recovered 94-98% of the bacterial colonies tested, were more resistant to tearing than the other Whatman papers tested, and showed reduced cross-reactions as compared with nitrocellulose membranes. Whatman No. 5 filters are 20 times less expensive than the nitrocellulose membranes usually used in the CIB technique. We thus adopted the former for our ecological studies of the murine oral cavity. 相似文献
15.
16.
Growth of the hopanoid-producing bacterium Zymomonas mobilis was inhibited at low concentrations of the cationic detergent octadecyltrimethylammoniumchloride (OTAC). A relationship between sensitivity of Zymomonas mobilis to OTAC, presence of hopanoids and ethanol tolerance was postulated. Mutants resistant to OTAC were isolated from strains ZM1 and ZM4. They did not present any alteration of the hopanoid content and their squalene cyclases showed the same sensitity to OTAC as the parent enzymes. Resistance to OTAC paralleled pleiotropic effects including, enhanced accessibility of the membrane-bound alkaline phosphatase, important release of proteins from cells by Tris/HCl treatment, increased resistance to antibiotics and increased sensitivity to ethanol. In addition, OTACR mutants were also characterized by the synthesis or the overproduction of an outer membrane protein (F53) not detected on 2D-PAGE maps of parent strains and by a normal heat shock response. The role of hopanoids, heat shock proteins, protein F53 and membrane organization in ethanol tolerance is discussed.Abbreviations OTAC
octadecyltrimethylammoniumchloride
- SLS
sodium lauryl sarcosinate 相似文献
17.
18.
Sylvie Cablé Michèle Kedinger Michel Dauça 《Differentiation; research in biological diversity》1993,54(2):99-108
Abstract. The development of peroxisomes and expression of their enzymes were investigated in differentiating intestinal epithelial cells during their migration along the crypt-villus axis. Sequential cell populations harvested by a low-temperature method were identified by microscopy, determination of alkaline phosphatase and sucrase activities and incorporation of [3 H]-thymidine into DNA. Ultrastructural cytochemistry after staining for catalase activity, revealed the presence of peroxisomes in undifferentiated stem cells located in the crypt region. Morphometry indicated that the number of these organelles increased as intestinal epithelial cells differentiate. Catalase activity was higher in the crypt cells than in the mature enterocytes harvested from villus tips. On the other hand, an increasing gradient of activity was observed from crypts to villus tips for peroxisomal oxidases, i.e. fatty acyl coA oxidase, D-amino acid oxidase and polyamine oxidase. These findings indicate that biogenesis of peroxisomes occurs during migration of intestinal epithelial cells along the crypt-villus axis and that peroxisomal oxidases contribute substantially to the biochemical maturation of enterocytes. 相似文献
19.
20.