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   479篇
  免费   13篇
化学   227篇
晶体学   9篇
力学   32篇
数学   45篇
物理学   179篇
  2022年   3篇
  2020年   6篇
  2019年   10篇
  2017年   16篇
  2016年   11篇
  2015年   4篇
  2014年   18篇
  2013年   48篇
  2012年   15篇
  2011年   17篇
  2010年   20篇
  2009年   16篇
  2008年   22篇
  2007年   18篇
  2006年   10篇
  2005年   17篇
  2004年   4篇
  2003年   12篇
  2002年   11篇
  2001年   5篇
  2000年   5篇
  1999年   7篇
  1997年   4篇
  1996年   9篇
  1995年   13篇
  1994年   6篇
  1993年   13篇
  1992年   7篇
  1991年   13篇
  1990年   6篇
  1989年   4篇
  1988年   10篇
  1986年   13篇
  1985年   7篇
  1983年   7篇
  1982年   5篇
  1981年   9篇
  1980年   6篇
  1979年   4篇
  1978年   5篇
  1977年   5篇
  1976年   4篇
  1975年   4篇
  1974年   6篇
  1973年   3篇
  1972年   3篇
  1971年   4篇
  1969年   4篇
  1967年   4篇
  1959年   2篇
排序方式: 共有492条查询结果,搜索用时 15 毫秒
61.
We present a grand unified model of the strong, electromagnetic and weak interactions based on a local SU(8)L×SU(8)R gauge theory which possesses a global U(8)L × U(8)R invariance. We break the symmetry down to the standard SU(3)C × SU(2)L × U(1) model, with the proton remaining stable and the left-handed neutrinos obliged to remain massless. A novel feature of our model is the simultaneous absence of both strong CP violations and of axions.  相似文献   
62.
V G Kher  V N Hete  D A Deshpande 《Pramana》1974,3(3):156-160
On application of dc electric fields to a sample of KNO2 (99.9% pure) fused between two heavily nickel plated copper plates the sample does not acquire the potential difference equal to the applied emf even though there is no external potential drop in the circuit. Also a very large capacitance of the order of 3000μF is obtained for this sample which is attributed to interfacial polarization effect. An equivalent circuit is given to explain the dc electrical behaviour of the sample. The idea of solid state battery does not seem to be applicable in the case of fused KNO2. The large value of the capacitance for dc fields in series with large voltage-dependent resistance is the cause of the slow discharge of the condenser.  相似文献   
63.
In the valence-quark c-decay scheme the decay D0K0π0 is expected to be strongly suppressed. We suggest that final state soft gluon exchange may account for the rather large branching ratio recently measured for this process, and study two-body decays of charmed mesons in our new scheme.  相似文献   
64.
We calculate the general transition qi → qj + γ for arbitrary quark flavors in a non-linear Rξ gauge. The reduced number of Feynman diagrams as well as simplified Ward identities greatly facilitates this calculation. A general result with intermediate quarks of arbitrary mass is presented and the special cases s → d + γ as well as s → d + gluon are discussed.  相似文献   
65.
66.
2-Acetyl-5,8-dimethoxy-3,4-dihydronaphthalene is synthesised easily·starting from 2-acetyl-5,8-dimethoxytetralone.  相似文献   
67.
To engineer lithium sulphate based material with high ionic conductivity at lowest possible temperature, the electrical conductivity of binary sulphates of Li2SO4 with Na2SO4, K2SO4, MgSO4, ZnSO4 and Ag2SO4 has been measured in the temperature range from 513 K to 773 K. The results are interpreted on the basis of different phases present therein. Li2SO4:Ag2SO4(40:60) mol % has high ionic conductivity = 2.17×10-3(ohm cm)-1 at 606 K which could be utilized in power sources.  相似文献   
68.
Structures, electronic and magnetic properties of Mn and Mn2 doped stoichiometric (GaO) n clusters with n = 1−7 are studied in the framework of density functional theory. Doping of a Mn atom is found to be energetically favorable in (GaO) n clusters and the equilibrium configurations are found to be determined by the metal–oxygen interactions. Mn prefers to maximize the number of Mn–O bonds by selecting a Ga site in the cluster which increases its coordination with oxygen. Addition of a Mn atom in Mn(GaO) n clusters results into the ground state to be either ferromagnetic or antiferromagnetic depending on the Mn coordination number and the Mn–Mn bond-length in the given Mn2(GaO) n cluster.  相似文献   
69.
We prove a common fixed point theorem for discontinuous,noncompatible mappings on noncomplete intuitionistic fuzzy metric spaces by using a new commutativity condition.We validate our main result by an example.  相似文献   
70.
In this note properties of two sequences generated by the recurrence relation G n+2 = 4G n+1 ? G n , are studied. It is shown that one of the sequences leads to a family of diophantine triplets. Some interesting properties of these sequences are also established.  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