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   536篇
  免费   10篇
  国内免费   1篇
化学   372篇
晶体学   13篇
力学   7篇
数学   13篇
物理学   142篇
  2021年   4篇
  2019年   7篇
  2018年   3篇
  2016年   6篇
  2015年   9篇
  2014年   11篇
  2013年   38篇
  2012年   15篇
  2011年   24篇
  2010年   14篇
  2009年   13篇
  2008年   28篇
  2007年   13篇
  2006年   24篇
  2005年   25篇
  2004年   15篇
  2003年   16篇
  2002年   29篇
  2001年   11篇
  2000年   5篇
  1999年   3篇
  1998年   4篇
  1997年   8篇
  1996年   3篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1992年   6篇
  1991年   6篇
  1990年   5篇
  1989年   6篇
  1988年   9篇
  1987年   4篇
  1986年   7篇
  1985年   14篇
  1984年   16篇
  1983年   6篇
  1982年   14篇
  1981年   21篇
  1980年   23篇
  1979年   14篇
  1978年   12篇
  1977年   7篇
  1976年   7篇
  1975年   5篇
  1974年   8篇
  1973年   4篇
  1972年   2篇
  1968年   3篇
  1942年   2篇
排序方式: 共有547条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Infrared and Raman spectra of 1,2-dibromoethane CH2BrCH2Br and CD2BrCD2Br were observed in the liquid state, and the fundamental frequencies were determined by comparison with those of related molecules. Infrared absorption intensities of fundament bands were measured in the liquid state, and the intensity data were interpreted on the basis of the valence-optical theory. From the converged value of a population ratio, the energy difference between the trans and gauche isomers was determined, which was in good agreement with the value obtained from the temperature effect of the IR spectrum.  相似文献   
5.
Isotropie Raman spectra of the symmetric C—H stretching bands of several organic molecules are measured in the neat liquid and in solvents including water. The linewidths are interpreted on the basis of the vibrational dephasing model, and intermolecular interactions between the solutes and solvents are discussed.  相似文献   
6.
Allylation of carbonucleophiles with allylic carbamates under neutral conditions has been studied. The C-allylation of carbonucleophile is competitive with the N-allylation of amines, and the structure of amines is crucial for the selectivity. Bulky secondary amines gave the best results. Also a new method of protection-deprotection of amines as carbamates has been developed. Smooth deprotection is possible by the palladium-catalyzed reaction of allyl carbamates with formic acid. This method is particulary useful for primary amines, including optically active amino acids.  相似文献   
7.
Dehydrroxy-trans-resorcylide (15) was synthesized by efficient intramolecular alkylation of the protected cyanohydrin. The butadiene telomer obtained by the palladium catalyzed reaction of butadiene with acetic acid was used as a suitable block of the carbocycle.  相似文献   
8.
The photoionization of 8-anilino-1-naphthalenesulfonate in polar solvents occurs through a biphotonic process, as proved by nanosecond flash photolysis. A transient absorption of a charge transfer to solvent (CTTS) state is found with ≈10 ns life-time. The state is shown to be an intermediate of the photoionization process.  相似文献   
9.
Phenotyping of erythrocyte acid phosphatase (EAP) and esterase D (ESD) by cellulose acetate membrane isoelectric focusing (CAM-IEF) under a nonequilibrium condition is described. In an attempt to improve the method of CAM-IEF, we shortened the electrode distance to provide a higher field strength at a given (low) voltage. Various carrier ampholytes for EAP typing and various chemical separators for ESD typing were also tested. Good separations were obtained after 30 min IEF for EAP typing and 25 min for ESD typing. When applied to blood stains and stored for various periods at room temperature, the stains up to 8 months old could still be phenotyped for EAP and those up to 4 weeks old for ESD. CAM-IEF is suitable for routine forensic work of EAP and ESD phenotyping.  相似文献   
10.
Oxidative cleavage reactions of catechol with CuCI to give monoester of cis,cis-muconic acid in pyridine containing alcohol was investigated under various conditions. The same oxidation was carried out also with the systems of KO2/CuCl2 and KOH/CuCl2 in pyridine containing alcohol in the absence of oxygen. Phenol was oxidized with the same oxidizing systems to give the same monoester of muconic acid.  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