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   1380篇
  免费   98篇
  1478篇
  2023年   7篇
  2022年   18篇
  2021年   43篇
  2020年   26篇
  2019年   39篇
  2018年   51篇
  2017年   31篇
  2016年   47篇
  2015年   58篇
  2014年   80篇
  2013年   80篇
  2012年   73篇
  2011年   79篇
  2010年   57篇
  2009年   46篇
  2008年   50篇
  2007年   72篇
  2006年   46篇
  2005年   53篇
  2004年   32篇
  2003年   34篇
  2002年   34篇
  2001年   20篇
  2000年   27篇
  1999年   16篇
  1998年   10篇
  1997年   7篇
  1995年   12篇
  1994年   11篇
  1992年   13篇
  1991年   25篇
  1990年   16篇
  1989年   27篇
  1988年   11篇
  1987年   9篇
  1986年   9篇
  1985年   16篇
  1984年   21篇
  1983年   10篇
  1982年   17篇
  1981年   10篇
  1980年   10篇
  1979年   22篇
  1978年   11篇
  1977年   15篇
  1975年   14篇
  1974年   6篇
  1973年   10篇
  1972年   9篇
  1971年   7篇
排序方式: 共有1478条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
A. C. Shukla 《Hydrobiologia》1967,30(2):221-224
Effect of presoaking seeds with different concentrations (0.5, 1 and 5%) of algal extracts on the development of stomata and epidermal cells in rice leaves has been investigated. One percent ether extract of Phormidium foveolarum (Mont.) Gomont suspended in water increases the number of stomata and also the total perimeter of stomatal pores, suggesting that the plants are better adopted for photosynthetic activity.  相似文献   
5.
6.
The role of phosphatidylinositol-specific phospholipase C (PIase C) in a) the enigmatic phosphatidylinositol (PI) turnover and b) in our understanding of membrane enzyme-PI interactions is the subject matter of this article. PIase C is present in both procaryotes and eukaryotes. This enzyme is considered to be involved in the cells PI breakdown which occurs in response to several external stimuli. Recent information on the physical properties, Ca2+ requirement, cellular localization and modulation of the activity of PIase C of mammalian systems can help to evaluate the PI turnover from a new angle. Existing evidence suggests that Ca2+-dependent PI breakdown is probably mediated through the cytosolic and particulate PIase C while a Ca2+ independent pathway is catalyzed by a lysosomal enzyme. Apparently PI turnover may be operating through more than one mechanism. The association of this phenomenon with a membrane receptor event linked with “Ca2+ gating” may have to be reconsidered. Modulation of the PIase C activity by unsaturated amphiphiles or the presence of this enzyme in different physico-chemical forms could be a potential regulatory feature.Hydrolysis of membrane PI of a number of cells and tissues by the bacterial PIase C has been shown to cause substantial release of acetylcholinesterase, alkaline phosphatase and 5′-nucleotidase in free, soluble form. Other membrane enzymes, e.g., alkaline phosphodiesterase I, L-leucyl-β naphtyl amidase and Ca2+ or Mg2+ ATPase are not affected. These results indicate a specific interaction between PI and certain enzymes in membranes. The chemical nature of this linkage, whether it is covalent or non-covalent, has also been explored and has provided intriguing insight into this phenomenon. New findings also indicate that hydrolysis of PI by PIase C also can cause modifications in membrane-enzyme activities, e.g., adenylate cyclase.  相似文献   
7.
Two new compounds G and H isolated from the roots of Costus speciosus have been characterized as 8-hydroxytriacontan-25-one and Me tritriacontanoat  相似文献   
8.
9.
Proteins and lipids in the haemolymph in both the sexes of the Danais chrysippus has been observed during the first gonotropic cycle. The concentration fluctuations in these haemolymph metabolites are correlated with the physiological state of the insect. The total protein and lipid concentration in the haemolymph of unmated females have been found to be low than the concentration found for the normal females although it followed the same type of oscillations in the concentration as have been observed for normal females.  相似文献   
10.
A simple agar diffusion method is developed where pure colony of Chlamydomonas sp. CRP7 was isolated from Chlorella sp. CB4 mixtures by passing through agar migration with a light exposure of 6,000 lux for 7 h. The main concept behind it is that Chlamydomonas has flagella and the rhodopsin pigment is attracted towards light. Thus the above two microalgae species can be separated from the mixtures as eye spot serves as a navigator and flagella serves as a propeller for Chlamydomonas spp. Further the genomic DNA was isolated and purified from the above mentioned two species after the separation from the mixtures. PCR amplification was carried out for ITS1, 5.8S and ITS2 regions. The amplified products were sequenced and the sequence analysis confirmed that they belong to Chlamydomonas sp. and Chlorella sp. This is an important augmentation for isolation and separation of microalgae.  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