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   10766篇
  免费   174篇
  国内免费   184篇
  11124篇
  2024年   19篇
  2023年   167篇
  2022年   176篇
  2021年   268篇
  2020年   336篇
  2019年   484篇
  2018年   466篇
  2017年   221篇
  2016年   243篇
  2015年   213篇
  2014年   864篇
  2013年   1272篇
  2012年   506篇
  2011年   789篇
  2010年   594篇
  2009年   525篇
  2008年   472篇
  2007年   527篇
  2006年   417篇
  2005年   365篇
  2004年   256篇
  2003年   197篇
  2002年   168篇
  2001年   36篇
  2000年   32篇
  1999年   22篇
  1998年   24篇
  1997年   16篇
  1996年   15篇
  1994年   16篇
  1993年   6篇
  1992年   7篇
  1991年   13篇
  1990年   12篇
  1989年   9篇
  1987年   9篇
  1985年   106篇
  1984年   178篇
  1983年   129篇
  1982年   132篇
  1981年   117篇
  1980年   116篇
  1979年   93篇
  1978年   75篇
  1977年   88篇
  1976年   88篇
  1975年   80篇
  1974年   58篇
  1973年   70篇
  1972年   19篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Effects of fasting on hepatic catecholamine receptors   总被引:1,自引:0,他引:1  
M F El-Refai  T M Chan 《FEBS letters》1982,146(2):397-402
  相似文献   
102.
103.
Core particle DNA unfolding and refolding are followed by stopped-flow circular dichroism technique. When core particles are dissociated in the stopped-flow cuvette, the high CD deviation corresponding to the dissociated state is reached in the first millisecond, which means that the dissociation process is completed within the dead time of the apparatus which is ~1 ms. The same conclusion can be drawn when core particles are reassociated, since the low CD value, typical of the associated state, is immediately reached. Similarly histone release from chromatin is a very fast process. We also include some points of discussion about core particle assembly process.  相似文献   
104.
J C Zolman 《FEBS letters》1982,143(1):26-28
Aspartate, glutamate, serine and glycine all permeate the inner membrane of mitochondria isolated from both etiolated and green plant tissues. No significant difference was found in the transport characteristics shown by mitochondria from either tissue. Influx of each amino acid appears diffusional because substrate saturation was not observed and there was no indication of specific inhibition or a requirement for a compensatory or counter ion for uptake. In contrast, uptake of the keto acid pyruvate did appear saturable. Inhibition by α-cyano-4-hydroxycinnamate, mersalyl and FCCP, but not valinomycin, suggests a carrier and a ΔpH mediate pyruvate transport into the matrix.  相似文献   
105.
External application of estradiol-17β increased shoot growth but decreased root growth of sunflower seedlings. It completely inhibited cotyledonary axillary bud development in decapitated plants at the concentration of 1 μg/plant. Concentrations lower than this promoted cotyledonary axillary bud formation. Testosterone on the other hand inhibited both shoot and root growth and promoted cotyledonary axillary bud formation at all the concentrations used. Progesterone at high (0.25,μg/plant) concentration promoted shoot growth but inhibited root growth. A low concentration (0.1 μg/plant) of progesterone produced the opposite effect.  相似文献   
106.
Twenty-seven mainly terpenoid constituents were identified in the essential oil of Mikania micrantha whole plant. Higher terpenoids present in the same plant included two kaurene derivatives and taraxasterol.  相似文献   
107.
Sterols were isolated from ten mushrooms, Hygrocybe punicea, Lampteromyces japonicus, Leucopaxillus giganteus, Lentinus edodes, Flammulina velutipes, Amanita caesarea, Coprinus atramentarius, Russula foetens, R. nigricans and R. senecis. The compositions of the sterol fractions were determined by GLC, combined GC/MS, and 1H NMR. Ergosterol was present in all the mushrooms. Other sterols found were 5α-cholest-7-en-3β-ol and ergosta-5,7-dien-3β-ol. Ergosta-5,8,22-trien-3β-ol was isolated from F. velutipes.  相似文献   
108.
The β-carbon of the acyl group of β-hydroxy-β-methylglutarylhydroxyabscisic acid was shown to possess R-configuration by HPLC analysis of the reduced product.  相似文献   
109.
The structures of two 4α-methylsterols is isolated from Cucumis sativus(Cucurbitaceae) seeds were determined based mainly on their 13CNMR spectra as 24β-ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)- dehydrolophenol, respectively, of which the former is a new sterol from natural sources. These two 4α-methylsterols were identified in the seeds of two other Cucurbitaceae species, Lagenaria leucantha var. Gourda and Citrullus battich. The probable biogenetic significance of the two 4α-methylsterols is discussed. Other 4α-methylsterols identified in the seeds of the three Cucurbitaceae species were obtusifoliol, cycloeucalenol and gramisterol.  相似文献   
110.
A new lichen depsidone was isolated, in the form of its triacetate derivative from the acetylated extracts of Nephroma antarcticum and has been demonstrated to be hypoconstictic acid-triacetate. Two related depsidones, hypostictic acid hyposalazinic acid, were isolated from N. australe.  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