全文获取类型
收费全文 | 2375篇 |
免费 | 211篇 |
国内免费 | 6篇 |
专业分类
2592篇 |
出版年
2022年 | 19篇 |
2021年 | 37篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 38篇 |
2017年 | 25篇 |
2016年 | 57篇 |
2015年 | 115篇 |
2014年 | 122篇 |
2013年 | 139篇 |
2012年 | 210篇 |
2011年 | 155篇 |
2010年 | 96篇 |
2009年 | 80篇 |
2008年 | 116篇 |
2007年 | 116篇 |
2006年 | 127篇 |
2005年 | 93篇 |
2004年 | 97篇 |
2003年 | 87篇 |
2002年 | 66篇 |
2001年 | 73篇 |
2000年 | 59篇 |
1999年 | 73篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 34篇 |
1991年 | 38篇 |
1990年 | 31篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 13篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1974年 | 11篇 |
1973年 | 15篇 |
1972年 | 13篇 |
排序方式: 共有2592条查询结果,搜索用时 0 毫秒
981.
982.
Vimentin is one of the intermediate filaments that functions in structural support, signal transduction and organelle positioning of a cell. In the present study, we report the contribution of vimentin in mitochondrial morphology and organization. Using subcellular fractionation, immunoprecipitation and fluorescence microscopy analyses, we found that vimentin was associated with mitochondria. Knockdown of vimentin resulted in mitochondrial fragmentation, swelling and disorganization. We further demonstrated that the vimentin cytoskeleton co-localized and interacted with mitochondria to a greater extent than other cytoskeletal components known to support mitochondria. Our results also suggest that vimentin could participate in the mitochondrial association of microtubules. As mitochondrial morphologies determine mitochondrial function, our findings revealed a potentially important relationship between the vimentin-based intermediate filaments and the regulation of mitochondria. 相似文献
983.
Synergism of biochemical and mechanical stimuli in the differentiation of human placenta-derived multipotent cells into endothelial cells 总被引:2,自引:0,他引:2
Wu CC Chao YC Chen CN Chien S Chen YC Chien CC Chiu JJ Linju Yen B 《Journal of biomechanics》2008,41(4):813-821
There have been intensive studies on the differentiation of endothelial progenitor cells (EPCs) into endothelial cells. We investigated the endothelial differentiation of placenta-derived multipotent cells (PDMCs), a population of CD34(-)/CD133(-)/Flk-1(-) cells. PDMCs were cultured in basal media or media containing endothelial growth factors (EGM), including vascular endothelial growth factor (VEGF), for 3 days and then subjected to shear stress of 6 or 12dyn/cm(2) for 24h. Culture of PDMCs in EGM under static conditions resulted in significant increases in VEGF receptor-1 (Flt-1) and receptor-2 (Flk-1) expression. Application of shear stress at 12dyn/cm(2) to these cells led to significant increases in their expression of von Willebrand Factor and platelet-endothelial cell adhesion molecule-1 at both the gene and protein levels. Shear stress at 6dyn/cm(2) had lesser effects. Uptakes of acetylated low-density lipoproteins as well as formation of tube-like structures on Matrigel were significantly increased after subjecting to shear stress of 12dyn/cm(2) for 24h. Our findings suggest that the combined use of endothelial growth factors and high shear stress is synergistic for the endothelial differentiation of PDMCs. 相似文献
984.
985.
Background
Contamination of endoscopy equipment by Helicobacter pylori (H. pylori) frequently occurs after endoscopic examination of H. pylori-infected patients. In the hospital, manual pre-cleaning and soaking in glutaraldehyde is an important process to disinfect endoscopes. However, this might not be sufficient to remove H. pylori completely, and some glutaraldehyde-resistant bacteria might survive and be passed to the next patient undergoing endoscopic examination through unidentified mechanisms. We identified an Imp/OstA protein associated with glutaraldehyde resistance in a clinical strain, NTUH-C1, from our previous study. To better understand and manage the problem of glutaraldehyde resistance, we further investigated its mechanism. 相似文献986.
Introduction
We have previously observed that Brown Norway (BN) rats display a relative resistance to experimental Chlamydia-induced arthritis. In the present study, we examine an environmental toxin, mercuric chloride (HgCl2), as a modulator of this innate resistance to arthritis. 相似文献987.
Ascherman JA Chiu DT 《Plastic and reconstructive surgery》2006,118(2):577; author reply 577-577; author reply 579
988.
989.
Genetically engineered pacemaking in ventricular cells has been achieved by down-regulation of the time independent inward rectifying current (I
K1), or insertion of the hyperpolarisation-activated funny current (I
f). We analyse the membrane system (i.e. ionic concentrations clamped) of an epicardial Luo-Rudy dynamic cell model using continuation algorithms with the maximum conductance () of I
K1 and I
f as bifurcation parameters. Pacemaker activity can be induced either via Hopf or homoclinic bifurcations. As
K1 is decreased by ≈74%, autorhythmicity emerged via a homoclinic bifurcation, i.e., the periodicity first appear with infinitely large periods. In contrast, the insertion of
f induced periodicity via a subcritical Hopf bifurcation at
f≈ 0.25 mSμF−1. Stable autorhythmic action potentials occurred at
f > 0.329 mSμF−1. 相似文献
990.
Mei Zhang Peter C.-K. Cheung Lawrence C.-M. Chiu Elaine Y.-L. Wong Vincent E.-C. Ooi 《Carbohydrate polymers》2006,66(4):455-462
The mechanism for the anti-tumor activity of a water-soluble carboxymethylated β-glucan (CMPTR), partially synthesized from an insoluble native glucan isolated from the sclerotia of Pleurotus tuber-regium, was studied using human breast carcinoma MCF-7 breast cancer cells in vitro. CMPTR-induced anti-proliferative activity dose-dependently, with an IC50 of 204 μg/ml. CMPTR inhibited the cell proliferation of MCF-7 by arresting the G1 phase of its cell cycle after 48 h of incubation as shown by flow cytometry. Such G1 phase arrest was associated with the down-regulation of cyclin D1 and cyclin E expressions in the breast cancer cells. In addition, the CMPTR-treated MCF-7 cancer cells were associated with decreased expression of anti-apoptotic Bcl-2 protein and increased expression of Bax/Bcl-2 ratio. This study shows that CMPTR can inhibit the proliferation of MCF-7 by cell-cycle arrest and apoptosis induction. The potential development of this mushroom polysaccharide as a water-soluble anti-tumor agent requires further investigation. 相似文献