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   622篇
  免费   34篇
  2023年   4篇
  2022年   15篇
  2021年   17篇
  2020年   15篇
  2019年   20篇
  2018年   24篇
  2017年   15篇
  2016年   29篇
  2015年   36篇
  2014年   33篇
  2013年   28篇
  2012年   43篇
  2011年   41篇
  2010年   36篇
  2009年   21篇
  2008年   35篇
  2007年   32篇
  2006年   19篇
  2005年   18篇
  2004年   15篇
  2003年   18篇
  2002年   12篇
  2001年   9篇
  2000年   5篇
  1998年   3篇
  1997年   5篇
  1996年   3篇
  1995年   4篇
  1991年   4篇
  1990年   3篇
  1988年   3篇
  1986年   4篇
  1983年   5篇
  1981年   2篇
  1978年   3篇
  1977年   2篇
  1975年   2篇
  1973年   8篇
  1972年   5篇
  1971年   3篇
  1966年   2篇
  1959年   2篇
  1958年   2篇
  1957年   2篇
  1956年   3篇
  1954年   4篇
  1952年   2篇
  1951年   4篇
  1950年   6篇
  1949年   2篇
排序方式: 共有656条查询结果,搜索用时 15 毫秒
61.
Protein extraction is the most important step to reveal a proteome by Two-Dimensional Gel Electrophoresis. Usually, the urea/thiourea based standard protein extraction buffer (SB) is combined with detergents with the aim of achieving better resolution and solubilization of different classes of proteins. In order to produce better gels and achieve the greatest spot resolution of Human Brain Proteins, comparisons using 2-DE of extracted proteins from Human Brain Frontal Cortex with SB constituents (7M Urea, 2M Thiourea and 100mM DTT) were made, using different detergent compositions in the buffer. SB preparations in combination with CHAPS and ASB-14 as well as with ASB-16 (reported for the first time in 2-DE experiments) have been tested. Our results confirm that the most efficient solubilizing solution for 2-DE analysis of cytosolic and membrane Human Brain Proteins is SB combined with 4% CHAPS and 2% ASB-14.  相似文献   
62.
Euglossina bees form a group with about 200 species known, widespread in Neotropical Region. Males collect aromatic compounds on flowers and by using synthesized analogs it is possible to accomplish faunistic inventories and study several ecological aspects of these bees. In this work we studied the activity hours and the preference of aromatic compounds by Euglossina males in forest and dunes at Environmental Protection Area of the Mamanguape River Bar, Rio Tinto, Paraíba State, between August 2002 and July 2004. Six artificial compounds were used as attractive: benzyl acetate, ionone beta, skatole, eucalyptol, eugenol and vanillin. Nine species were sampled, being two of them exclusive of the forest. Euglossa cordata (L.) and Eulaema nigrita Lepeletier were the most abundant species as in the forest as on dunes. Males were more active between 8:00 a.m. and 10:00 a.m. in both areas, with no variation throughout the year. Eucalyptol and eugenol attracted most number of species. E. cordata demonstrated preference by ionone beta and eucalyptol and E. nigrita by skatole and eucalyptol.  相似文献   
63.
64.
Environmental Biology of Fishes - To clarify the reproductive activity of lane snapper, Lutjanus synagris, a total of 359 specimens of lane snapper were collected in partnership with an artisanal...  相似文献   
65.
66.
67.
68.
Four derivatives of an α,β-amyrin mixture were synthesized by acylation with appropriate anhydrides. The structures of the compounds were confirmed by means of IR and (1)H and (13)C NMR. The compounds were screened for cytotoxic activity using four human tumor cell lines (HL-60, MDAMB-435, SF-295 and HCT-8) and normal peripheral blood mononuclear cells (PBMC). 3-O-Carboxymaleinate of α,β-amyrin (3a/3b) were found to be the only active compounds of the series (high cytotoxicity), showing IC(50) values ranging from 1.8 to 3μM. In PBMC, 3a/3b were not toxic, suggesting selectivity for tumor cells. To better understand the mechanism of action involved in the cytotoxicity of 3a/3b, HL-60 cells treated with 3a/3b were examined for morphological changes, DNA fragmentation, cell cycle perturbation, externalization of phosphatidylserine and activation of caspases 3/7, with doxorubicin serving as the positive control. The results indicate that the cytotoxicity of 3a/3b involves the induction of cell death by apoptosis.  相似文献   
69.
70.
Plasmepsin (PM) II is one of four enzymes in the food vacuole of Plasmodium falciparum. It has become an attractive target for combating malaria through research regarding its importance in the P. falciparum metabolism and life cycle, making it the target of choice for structure-based drug design. This paper reports the results of hybrid quantum mechanics / molecular mechanics (QM/MM) molecular dynamics (MD) simulations employed to study the details of the interactions established between PM II and N-(3-{(2-benzo[1, 3]dioxol-5-yl-ethyl)[3-(1-methyl-3-oxo-1,3-dihydro-isoindol-2-yl) propionyl]-amino}-1-benzyl-2-(hydroxyl-propyl)-4-benzyloxy-3,5dimethoxy-benzamide (EH58), a well-known potent inhibitor for this enzyme. Electrostatic binding free energy and energy terms decomposition have been computed for PM II complexed with the EH58 inhibitor. The results reveal that there is a strong interaction between Asp34, Val78, Ser79, Tyr192 and Asp214 residues and the EH58 inhibitor. In addition, we have computed the potential of the mean force (PMF) profile in order to assign the protonation state of the two catalytic aspartates in PM II-EH58 complex. The results indicate that the protonation of Asp214 favors a stable active site structure, which is consistent with our electrostatic binding free energy calculation and with previous published works.  相似文献   
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