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   46245篇
  免费   15684篇
  国内免费   58篇
化学   55748篇
晶体学   61篇
力学   2047篇
数学   2742篇
物理学   1389篇
  2024年   372篇
  2023年   4086篇
  2022年   1443篇
  2021年   2481篇
  2020年   4626篇
  2019年   2317篇
  2018年   2286篇
  2017年   606篇
  2016年   5577篇
  2015年   5534篇
  2014年   4957篇
  2013年   5185篇
  2012年   3223篇
  2011年   1076篇
  2010年   3428篇
  2009年   3390篇
  2008年   1065篇
  2007年   789篇
  2006年   148篇
  2005年   116篇
  1997年   88篇
  1995年   152篇
  1994年   96篇
  1993年   219篇
  1992年   111篇
  1988年   123篇
  1987年   106篇
  1986年   85篇
  1985年   106篇
  1984年   116篇
  1983年   106篇
  1982年   140篇
  1981年   171篇
  1980年   202篇
  1979年   198篇
  1978年   197篇
  1977年   326篇
  1976年   367篇
  1975年   469篇
  1974年   475篇
  1973年   293篇
  1972年   374篇
  1971年   355篇
  1970年   543篇
  1969年   416篇
  1968年   458篇
  1967年   115篇
  1966年   92篇
  1965年   83篇
  1963年   113篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
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   
102.
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   
103.
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   
104.
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   
105.
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   
106.
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   
107.
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   
108.
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   
109.
It is shown by a simple induction that any square-free natural number is the square-free kernel of Euler's -function of infinitely many natural numbers. Furthermore every square-free natural number >1 is the square-free kernel of Euler's -function of infinitely many square-numbers.  相似文献   
110.
Let ={e(u)|uI} be a one-parameter family of straight lines forming a ruledC r-2-surface E n (n2,r1) without singular generatorse(u) (uI). As a synopsis, a generalization and an improvement of various results already known about the strictional properties of ruled surfaces E n (especially in the casen=3) the author demonstrates a uniform geometrical way of defining and uniquely obtaining thestriction point S(u) and theparameter of distribution d(u) of a generatore(u) under the minimal assumptions thate(u)E n (n2) be noncylindrical andr1. Other methods of obtainingS(u) andd(u) are discussed in comparison, and special strictional properties ofskew ruled surfaces E n are proved.

Herrn Prof. Dr. H. R. Müller zum 65. Geburtstag  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