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   198篇
  免费   30篇
  国内免费   42篇
化学   98篇
晶体学   5篇
力学   9篇
综合类   2篇
数学   32篇
物理学   124篇
  2023年   2篇
  2022年   3篇
  2021年   6篇
  2020年   3篇
  2019年   8篇
  2018年   4篇
  2017年   8篇
  2016年   4篇
  2015年   6篇
  2014年   13篇
  2013年   9篇
  2012年   15篇
  2011年   14篇
  2010年   11篇
  2009年   12篇
  2008年   16篇
  2007年   14篇
  2006年   10篇
  2005年   7篇
  2004年   5篇
  2002年   2篇
  2001年   9篇
  2000年   2篇
  1999年   4篇
  1998年   2篇
  1995年   3篇
  1994年   4篇
  1993年   3篇
  1992年   5篇
  1990年   6篇
  1988年   6篇
  1987年   3篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1983年   7篇
  1982年   3篇
  1981年   2篇
  1979年   3篇
  1978年   2篇
  1977年   4篇
  1976年   3篇
  1975年   1篇
  1974年   1篇
  1973年   3篇
  1972年   3篇
  1971年   1篇
  1968年   1篇
  1965年   2篇
  1961年   1篇
排序方式: 共有270条查询结果,搜索用时 15 毫秒
151.
A simple model of a classical break-up process is given in which the correlation E(a,b) of the components A and B of the spins of the two subsystems along directions a and b gives precisely the quantum mechanical result ?cos(a·b). The model is “local”, but the normalization procedure of correlation functions in terms of “hidden variables” is different from that used in deriving Bell's inequalities. A discretization procedure of the classical spins is then given which reproduces fully the dichotomous quantum mechanical results both for probabilities and for correlation functions. This procedure illustrates particularly clearly the difference between quantum and classical spins and provides a possible intuitive picture for the notion of the “reduction of the wave function”.  相似文献   
152.
Bäcklund transformations for several nonlinear field equations in four-dimensional space-time relating two solutions of the same equation (symmetry), or two different equations (dynamical), are given. These transformations can be used to generate new families of solutions and infinitely many conservation laws for nonlinear equations.Bäcklund transformations and solutions of nonlinear equations have been studied extensively in one-space and one-time dimension. We give here a fairly general method for a class of equations in four-dimensional space-time which paves the way for many further generalizations.Supported in part by the U.S. National Academy of Sciences Foundation Grant No. INT 73-20002 A01 (formerly GF-41958).  相似文献   
153.
We present, in various limits, analytical expressions for the center-of-mass wave function of a spin-1/2 atom as it is deflected by a Stern-Gerlach apparatus.Work Supported by the Office of Naval Research.  相似文献   
154.
The relations betweeb a field FμνM satisfying the usual Maxwell equations and a field FμνD satisfying the symmetric Maxwell-Dirac equations, and the singular potential solving both of these is given. The action principle is formulated in both forms and the reality of the string is shown. A string with spin is constructed by placing electric charges at its end-points. The motion and interactions of the string, the relation between flux and angular momentum quantization and the passage to two-body Hamiltonians are examined.  相似文献   
155.
The internal motion of the electron (i.e. Zitterbewegung) takes place in a hyperplane in the Minkowski space orthogonal to the four-vector p u. For a four-component massless Dirac neutrino it takes place on a two-dimensional plane perpendicular to the three-momentum p, and for a two-component Weyl neutrino it takes place along a straight line perpendicular to p. The kinematical algebras of the compact internal quantum systems are so(5), so(4), and so(2), respectively.On leave from Department of Mathematics, University of Queensland, Australia  相似文献   
156.
α-芳基取代二甲氧基苯丙烯酸;Pekin反应;抗炎作用  相似文献   
157.
Optically pure l,1'-binaphthalene-2,2'-diols are very useful compounds for various application[1] such as catalyst ligands for asymmetric synthesis, the starting materials for other chiral binaphthyl catalysts and resolving agents for racemic compounds. Consequently, the preparation of optically pure l,l'-binaphthalene-2,2'-diols are of current interest Recently, new methods of resolution of racemic l,1'-binaphthalene-2,2'-diols utilizing (-)-(lR)-menthyl chloroformate as the derivatization agent have been developed[2,3]. To determine the optical purity of these 1,1'-binaphthalenes, it is necessary to develop a convenient and reliable method for the detection of each stereoisomers.  相似文献   
158.
气相色谱-质谱法测定艾叶挥发油中化学成分   总被引:1,自引:0,他引:1  
采用水蒸气蒸馏法提取艾叶的挥发油,用气相色谱-质谱法分离和鉴定挥发油成分,并用归一化法测定其相对含量。共分离出76个组分,鉴定出59种化合物。其含量占总挥发油组分峰面积的94.3%。贵州遵义产艾叶主要挥发油成分及其含量为1,8-桉叶油素(22.19%)、樟脑(10.39%)、绿花白千层醇(6.57%)、蒿醇(4.95%)、L-龙脑(4.88%)、α-松油烯(3.98%)、蒿酮(3.44%)、顺式桧烯水合物(3.36%)、4-松油醇(2.68%)、菊油环酮(2.51%)、β-崖柏酮(2.41%)、1-松油醇(2.32%)和丁香酚(2.26%)等。  相似文献   
159.
As a highly selective and potent acetylcholinesterase(AChE)inhibitor,territrem B wasisolated by Ling et al.from a strain of Aspergillus terreus in19791,2.Zhao et alreported mimic preparation of territrem B analogues from triterpenoids and found thatthe enone moiety and aromatic ring played important roles in their syntheticcompounds3,4.To further detect essential pharmacophors for AChE inhibitors,wesimplified the A/B ring system of territrem B and synthesized a number of pyranonepharmacop…  相似文献   
160.
Monoliths are chromatographic stationary phases, which were specially designed for efficient purification of large biomolecules, like proteins, viruses and DNA. In this work, the small scale monolithic butyl (C4) and styrene-divinyl benzene (SDVB) columns were applied for reversed phase analyses of various degraded influenza viruses. The binding of the HA1 subunit of haemagglutinin to the monolithic columns was confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and the Western blot. The working linear range was determined as 1.60 × 1010 viral particles/mL to at least 1.64 × 1011 viral particles/mL, the limit of detection was found to be 2.56 × 109 virus particles/mL and the limit of quantification was 5.12 × 109 virus particles/mL. The analytical HPLC method developed with the H1N1 virus was also applicable for the analytics of the HA1 subunit of H3N2 influenza virus and the influenza B virus.  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