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   630篇
  免费   25篇
  国内免费   2篇
  2024年   2篇
  2023年   6篇
  2022年   25篇
  2021年   51篇
  2020年   31篇
  2019年   52篇
  2018年   29篇
  2017年   25篇
  2016年   30篇
  2015年   17篇
  2014年   47篇
  2013年   51篇
  2012年   46篇
  2011年   55篇
  2010年   32篇
  2009年   18篇
  2008年   23篇
  2007年   23篇
  2006年   22篇
  2005年   18篇
  2004年   10篇
  2003年   9篇
  2002年   11篇
  2001年   1篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1996年   4篇
  1994年   1篇
  1993年   2篇
  1988年   1篇
  1987年   2篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1976年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有657条查询结果,搜索用时 0 毫秒
1.
In this paper the synthetic methods of three covalently linked porphyrin-phthalocyanine heteropentamers, containing four units of porphyrin linked to a central phthalocyanine (Mpor-LPc; M = 2H, Fe, L = Zn, Fe), are described. The synthetic strategy is on the basis of nucleophilic substitution reactions between [1,8,15,22-tetra nitro phthalocyanines] and [5-(4-hydroxy phenyl)-10,15,20-triphenyl porphyrins] as the phenolic alcohols. Porphyrins are linked with oxygen as spacer through meso position of phenyl group to phthalocyanines. These macromolecules were characterized by 1H NMR, UV-Vis, IR, fluorescence and mass spectroscopy. The electronic absorption spectrums of the hetero-dyad systems changed significantly upon coupling and showed a great red shift in the phthalocyanine Q-bands. These changes confirm the electron-donating effects of the porphyrin units and the extension of conjugated п-systems. The emission spectra of the products supports intramolecular energy and charge transfer between the sub-units.  相似文献   
2.
The kinetics of lipid peroxide decomposition catalysed by microsomal enzymes and inhibited by SKF-525 A, hexobarbital, phenobarbital and aniline were investigated. The results indicate that the in vitro interaction of hexobarbital and SKF-525 A (type I binding compounds) with microsomal cytochrome p-450 inhibits the peroxidase activity while the in vitro interaction of aniline (type II binding compound) only slightly affect the peroxidase activity. It is suggested that LAHPO and type I binding compounds are competing for the hydrophobic binding site on cytochrome p-450, while type II binding compounds such as aniline negate electron transfer non-competitively by combining with the heme.  相似文献   
3.
Nabil  Samira  Cosson  Joël 《Hydrobiologia》1996,326(1):511-514
On Normandy coasts, the red alga Delesseria sanguinea perennates by its stipe; fronds grow in January and disappear in June. Seasonal variations in sterol composition in relation to the biology of D. sanguinea are reported. Sterols in cellular membranes are free or conjugated by esterification with fatty acids, heterosides or lipid complexes like phospholipids. Both kinds of sterols were analyzed by GC-MS. The major sterol (80%) found in fronds was cholesterol whereas in stipes, cholesterol was also the major sterol in spring, but in September, an important reduction in cholesterol yield was noted with proportional increase in sitosterol content. It appears that cholesterol is synthesized in fronds in spring, then transferred to the stipe, which loses an important amount of cholesterol with loss of the blades.  相似文献   
4.
We applied a modified immunofluorescence and immunoperoxidase method, utilizing labeled Blastomyces dermatitidis antigens, to look for specific antibody-bearing B/ plasma cells in the tissue infiltrates of blastomycosis lesions induced in hamsters. No specific anti-blastomyces antibodies were detectable by this method, although such antibodies were present in blood samples as demonstrated by routine immunodiffusion techniques. These studies suggest that humoral immune reactions do not play a major role in the pathogenesis of lesions of blastomycosis in hamsters.  相似文献   
5.
6.
7.
8.
Plant Cell, Tissue and Organ Culture (PCTOC) - In the present study, the integrative effects of two sets of stress tolerance-inducing and stress-inducing elicitors, including polyethylene...  相似文献   
9.
10.
Biochemical Genetics - Several studies have noted that vitamin D receptor (VDR) gene polymorphisms are involved in the susceptibility to Coronary artery disease (CAD). Nonetheless, the results have...  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