首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   656篇
  免费   68篇
  724篇
  2023年   8篇
  2022年   8篇
  2021年   24篇
  2020年   16篇
  2019年   15篇
  2018年   20篇
  2017年   20篇
  2016年   30篇
  2015年   36篇
  2014年   47篇
  2013年   44篇
  2012年   62篇
  2011年   51篇
  2010年   20篇
  2009年   24篇
  2008年   32篇
  2007年   43篇
  2006年   32篇
  2005年   22篇
  2004年   21篇
  2003年   27篇
  2002年   25篇
  2001年   6篇
  2000年   5篇
  1999年   6篇
  1998年   9篇
  1997年   4篇
  1996年   6篇
  1995年   5篇
  1994年   3篇
  1991年   4篇
  1987年   3篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1976年   2篇
  1975年   2篇
  1969年   4篇
  1968年   2篇
  1967年   2篇
  1966年   2篇
  1961年   1篇
  1960年   2篇
  1954年   1篇
  1952年   1篇
  1949年   1篇
  1942年   1篇
  1941年   1篇
排序方式: 共有724条查询结果,搜索用时 15 毫秒
11.
The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome.Four lines were deficient in total β-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical β-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease.The possible mechanisms explaining the high frequency of β-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.  相似文献   
12.
13.
In this study, we found that production of both reactive oxygen (ROS) and nitrogen (RNS) species is a very early event related to treatment with hyperosmotic concentration of sorbitol. The production of nitric oxide (NO) was paralleled by the increase of the mRNA and protein level of the inducible form of the nitric oxide synthase (iNOS). ROS and RNS enhancement, process concomitant to the failure of mitochondrial trans-membrane potential (ΔΨ), was necessary for the induction of apoptosis as demonstrated by the protection against sorbitol-mediated toxicity observed after treatment with ROS scavengers or NOS inhibitors. The synergistic action of ROS and RNS was finally demonstrated by pre-treatment with rosmarinic acid that, by powerfully buffering both these species, prevents impairment of ΔΨ and cell death. Overall results suggest that the occurrence of apoptosis upon sorbitol treatment is an event mediated by oxidative/nitrosative stress rather than a canonical hyperosmotic shock.  相似文献   
14.
We investigated the molecular relationships between lipid peroxidation and mitochondrial DNA (mtDNA) single strand breaks (ssb) in isolated rat hepatocytes and mitochondria exposed to tert-butylhydroperoxide (TBH). Our results show that mtDNA ssb induced by TBH are independent of lipid peroxidation and dependent on the presence of iron and of hydroxyl free radicals. These data contribute to the definition of the mechanisms whereby mtDNA ssb are induced and provide possible molecular targets for the prevention of this kind of damage in vivo.  相似文献   
15.
Because of its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum has a considerable potential in biomass hydrolysis applications. Trichoderma harzianum cellobiohydrolase I (ThCBHI), an exoglucanase, is an important enzyme in the process of cellulose degradation. Here, we report an easy single-step ion-exchange chromatographic method for purification of ThCBHI and its initial biophysical and biochemical characterization. The ThCBHI produced by induction with microcrystalline cellulose under submerged fermentation was purified on DEAE-Sephadex A-50 media and its identity was confirmed by mass spectrometry. The ThCBHI biochemical characterization showed that the protein has a molecular mass of 66 kDa and pI of 5.23. As confirmed by smallangle X-ray scattering (SAXS), both full-length ThCBHI and its catalytic core domain (CCD) obtained by digestion with papain are monomeric in solution. Secondary structure analysis of ThCBHI by circular dichroism revealed alpha- helices and beta-strands contents in the 28% and 38% range, respectively. The intrinsic fluorescence emission maximum of 337 nm was accounted for as different degrees of exposure of ThCBHI tryptophan residues to water. Moreover, ThCBHI displayed maximum activity at pH 5.0 and temperature of 50 degrees C with specific activities against Avicel and p-nitrophenyl-β-D-cellobioside of 1.25 U/mg and 1.53 U/mg, respectively.  相似文献   
16.
The tachogram shows that the flow of cough is neither continuous nor steady. Within a cough, 5 different phases can be differentiated: 1) acceleration, 2) initial fast decleration, 3) intermediary decleration, 4) terminal fast decleration, and 5) the flow-pause. Only in the course of phases 1) and 3) is the air flowing out from the lungs. In cough series the peak-flows of subsequent coughs are growing smaller and smaller. This decrease follows the form of an isosceles hyperbola. A cough can be short or elongated. From the flow-phases the 1-st, 2-nd and 4-th ones are of fairly stable duration. The wide deviation of the intermediary deceleration shows that this phase makes it possible to elongate voluntarily the cough.  相似文献   
17.
The human histamine H4 receptor (hH4R), a member of the G-protein coupled receptors (GPCR) family, is an increasingly attractive drug target. It plays a key role in many cell pathways and many hH4R ligands are studied for the treatment of several inflammatory, allergic and autoimmune disorders, as well as for analgesic activity. Due to the challenging difficulties in the experimental elucidation of hH4R structure, virtual screening campaigns are normally run on homology based models. However, a wealth of information about the chemical properties of GPCR ligands has also accumulated over the last few years and an appropriate combination of these ligand-based knowledge with structure-based molecular modeling studies emerges as a promising strategy for computer-assisted drug design. Here, two chemoinformatics techniques, the Intelligent Learning Engine (ILE) and Iterative Stochastic Elimination (ISE) approach, were used to index chemicals for their hH4R bioactivity. An application of the prediction model on external test set composed of more than 160 hH4R antagonists picked from the chEMBL database gave enrichment factor of 16.4. A virtual high throughput screening on ZINC database was carried out, picking ∼4000 chemicals highly indexed as H4R antagonists'' candidates. Next, a series of 3D models of hH4R were generated by molecular modeling and molecular dynamics simulations performed in fully atomistic lipid membranes. The efficacy of the hH4R 3D models in discrimination between actives and non-actives were checked and the 3D model with the best performance was chosen for further docking studies performed on the focused library. The output of these docking studies was a consensus library of 11 highly active scored drug candidates. Our findings suggest that a sequential combination of ligand-based chemoinformatics approaches with structure-based ones has the potential to improve the success rate in discovering new biologically active GPCR drugs and increase the enrichment factors in a synergistic manner.  相似文献   
18.
19.
Metabolomics - Food and dietary ingredients have significant effects on metabolism and health. To evaluate whether and how different diets affected the serum lipidomic profile of dogs. Sixteen...  相似文献   
20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号