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   56158篇
  免费   17478篇
  国内免费   81篇
化学   65255篇
晶体学   105篇
力学   2451篇
数学   3550篇
物理学   2356篇
  2024年   461篇
  2023年   4765篇
  2022年   1715篇
  2021年   2908篇
  2020年   5232篇
  2019年   2657篇
  2018年   2616篇
  2017年   727篇
  2016年   6248篇
  2015年   6219篇
  2014年   5672篇
  2013年   6021篇
  2012年   3912篇
  2011年   1650篇
  2010年   3995篇
  2009年   3922篇
  2008年   1524篇
  2007年   1164篇
  2006年   449篇
  2005年   397篇
  2004年   306篇
  2003年   274篇
  2002年   260篇
  2001年   161篇
  2000年   139篇
  1997年   137篇
  1996年   153篇
  1995年   232篇
  1994年   165篇
  1993年   301篇
  1992年   156篇
  1988年   144篇
  1987年   124篇
  1984年   124篇
  1983年   122篇
  1982年   148篇
  1981年   171篇
  1980年   211篇
  1979年   212篇
  1978年   222篇
  1977年   338篇
  1976年   399篇
  1975年   482篇
  1974年   508篇
  1973年   328篇
  1972年   456篇
  1971年   417篇
  1970年   626篇
  1969年   460篇
  1968年   504篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
Complexes of 2,6-dimethylpyridine 1-oxide with lanthanide iodides of the formulaeLn(2,6-LTNO)5I3 whereLn=La, Tb and Yb,Ln(2,6-LTNO)4I3 whereLn=Pr and Nd and Er(2,6-LTNO)4.5I3 have been prepared and characterised by chemical analysis, infrared and conductance studies. Infrared and conductance data have been interpreted in terms of dimeric (or polymeric) structures involving bridging amine oxide groups.

Mit 2 Abbildungen  相似文献   
162.
The synthesis of 5-(o-trifluoromethylphenyl)-1H-thieno-[3,4-e]1,4-diazepin-2(3H)-one (7) and its nitration and chlorination in pos. 8 are described.  相似文献   
163.
Mean amplitudes of vibration of a series of tetrahedralXY 4 molecules and ions (hydrides, halides, oxides and oxoanions) have been calculated using the “Method of the Characteristic Vibrations” ofA. Müller. The results indicate that this method leads to very good values for most of the investigated species, and especially in the cases of highM X/MY mass ratio.  相似文献   
164.
The reactions of Ge2(C6H5)6 with HCl and HBr lead in nearly quantitative yields to the 1,1,2,2-tetrahalo derivatives Cl2(C6H5)GeGe(C6H5)Cl2 (I) and Br2(C6H5)GeGe(C6H5)Br2 (II), resp. The Si?Ge bond of (C6H5)3SiGe(C6H5)3 is cleaved under the conditions of hydrohalogenation. The vibrational spectra of Ge2Br6, Ge2(C6H5)6, I, and II are reported. The influence of vibrational coupling on ν GeGe in these compounds is discussed in detail, including vibrational calculations.  相似文献   
165.
The hyperfine structure of the metastable atomic states (3d 74s)5 F 2,3,4,5 and (3d 7 4s)3 F 2,3,4 of57Fe has been measured using theABMR- LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). From these measurements the following hfs constantsA of the magnetic dipole interaction have been obtained (corrected for second order effects):A(5 F 2)=55.994(7) MHzA(5 F 3)=69.632(5) MHzA(5 F 4)=78.435(4) MHzA(5 F 5)=87.246(3) MHzA(3 F 2)=143.328(4) MHzA(3 F 3)=50.602(10) MHzA(3 F 4)=13.456(5) MHz  相似文献   
166.
A new proof of a theorem of W. Neiss is given that the rays of the Quadratwurzelschnecke are uniformly distributed mod 2 . The exact order of the discrepancy of the sequence is determined. Multidimensional generalizations of this sequence are also considered. It is shown that the Quadratwurzelschnecke is something like a roulette.

Mit 2 Abbildungen

Herrn Prof. R. M. Redheffer in Freundschaft zum 60. Geburtstag gewidmet  相似文献   
167.
Motivated by an investigation ofKuz'min [2], in this note we introduce a topology on the set of nonassociative algebras of a fixed dimensionr< over a local fieldF. We obtain a space, which is notT 1. If the trivial algebra is removed, the remaining subspace is quasicompact. The space is homeomoprhic to the group of square classes ofF *; forr3 the space is notT 1. The set of division algebras is open in.  相似文献   
168.
We continue our investigations started in a paper with the same title. The -length of a curve defined in this paper can be written as an integral along the curve. Furthermore, we determine necessary and sufficient conditions for the existence of a measure of orientated lines which generates a given non-symmetric pseudo-metric.

Herrn Prof. Dr. H.-J. Kanold zum 65. Geburtstag gewidmet  相似文献   
169.
Arithmetic formulae and an asymptotic expression for the order of magnitude of the arithmetic function ged (s, n) and of a generalisation of it are derived.  相似文献   
170.
This paper deals with the global classical solvability of the Cauchy problem for nonlinear wave equations of higher order of the following form where denotes the Laplacian, a real constant, m a positive integer, and f the nonlinearity. Using results of the first part [6] concerning estimations for the kernel of the associated integral equation a priori estimates for certain LP-norms of the local regular solution are established for higher space dimensions and for a class of nonlinearities satisfying certain growth and positivity conditions. This leads to completely regular solutions by means of the Sobolev embedding theorems.  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