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   12052篇
  免费   373篇
  国内免费   6篇
化学   6818篇
晶体学   225篇
力学   236篇
数学   2196篇
物理学   2956篇
  2022年   71篇
  2021年   132篇
  2020年   170篇
  2019年   212篇
  2018年   232篇
  2017年   275篇
  2016年   524篇
  2015年   403篇
  2014年   484篇
  2013年   927篇
  2012年   606篇
  2011年   692篇
  2010年   497篇
  2009年   425篇
  2008年   572篇
  2007年   515篇
  2006年   424篇
  2005年   357篇
  2004年   316篇
  2003年   258篇
  2002年   221篇
  2001年   169篇
  2000年   173篇
  1999年   136篇
  1998年   139篇
  1997年   109篇
  1996年   133篇
  1995年   116篇
  1994年   101篇
  1993年   95篇
  1992年   96篇
  1991年   115篇
  1990年   108篇
  1989年   111篇
  1988年   96篇
  1987年   116篇
  1986年   85篇
  1985年   156篇
  1984年   160篇
  1983年   125篇
  1982年   114篇
  1981年   120篇
  1980年   108篇
  1979年   107篇
  1978年   92篇
  1977年   72篇
  1976年   99篇
  1975年   91篇
  1974年   74篇
  1973年   70篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
91.
The kinetic equation of the classical homogeneous nucleation theory is rewritten in dimensionless form and it is shown that the numerical computation of the dimensionless kinetic equation is approximately 20 times faster in comparison with the original kinetic equation. The results are compared with known analytical results and with previous numerical results in the case of the constant and variable temperature for the model Li2O.2 SiO2 melt. It is shown, e.g., that under non-isothermal conditions the nucleation rate is greater than the quasistationary nucleation rate and the cluster distribution function is greater than the corresponding quasiequilibrium cluster distribution function.  相似文献   
92.
93.
We examine some properties of two types of inversions in the isotropical model of n-dimensional Laguerre space. Moreover we establish an isomorphism between the isotropical and the cylinder models of the n-dimensional Laguerre space. We prove also that every automorphism of the n-dimensional Laguerre space is a composition of a pseudodilatation and some involutive maps.  相似文献   
94.
Let (E, ¦·¦) be a uniformly convex Banach space with the modulus of uniform convexity of power type. Let be the convolution of the distribution of a random series inE with independent one-dimensional components and an arbitrary probability measure onE. Under some assumptions about the components and the smoothness of the norm we show that there exists a constant such that |{·<t}–{·+r<t}|r q , whereq depends on the properties of the norm. We specify it in the case ofL spaces, >1.  相似文献   
95.
The title compound (C14H8N2O7,M r =306.2) crystallizes in the orthorhombic space group Pbca witha=6.962(1).b=24.688(1), andc=15.890(1)Å,V=2731.0 Å3,D x =1.489 g·cm–3 forZ=8,=0.98 mm–1,F(000)=1296,T=293 K. FinalR=0.053 for 1873 observed reflections. The structure was solved by direct methods. Approximately planar molecules lie perpendicular to the [100] direction and show partial stacking. The structure is the first example of a symmetric anhydride which does not retain the symmetry in the crystal state. The two independent nitro groups twist out of the ring planes by 10.5 and 14.8°, respectively.  相似文献   
96.
97.
The crystal structure of 18-cyanoprogesterone was determined by X-ray diffraction methods:P212121 a=7.436(2),b=11.322(2),c=22.642(2) Å. The structure was solved usingShelx-86. Final conventionalR=0.054.R w =0.051 for 1841 reflections. TheA ring has an intermediate sofa-half-chair conformation with asymmetry parameters C s /1 =11.0, C 2 3,4 =14.9. The steroid skeleton exhibits a flattening of theA ring relative to the rest of the molecule. The progesterone side chain has a typical conformation, and the C16-C17-C20-O20 torsion angle is –19.0(6)°.  相似文献   
98.
A notion of anin-tree is introduced. It is then used to characterize and count plane embeddings of outerplanar graphs. In-trees have also been applied in the study of independent vertex covers of faces in outerplanar graphs.This research was partially supported by the grant RP.I.09, from the Institute of Informatics, University of Warsaw. Hospitality of the Institute of Datalogy, University of Copenhagen where this research has been completed is gratefully acknowledged.  相似文献   
99.
Summary In this paper we introduce some new classes of functions, among these a class of weak diffeomorphisms. In these classes we prove by direct methods the existence of minimizers for several kinds of variational integrals. In particular, we prove the existence of one-to-one orientation-preserving maps that minimize suitable energies associated with hyperelastic materials. The minimizers are also proved to satisfy equilibrium equations. Finally radial deformations are discussed in connection with cavitation.  相似文献   
100.
The dynamical system approach is applied to the study of dynamics of multidimensional cosmological models with topology FRW ×T D (D-dimensional torus) in the presence of high-temperature quantum effects. The stability methods developed in the paper of Szydowski (Gen. Rel. Grav.,20, 221, 1988) are used in the analysis of typical states of the metric in the neighborhood of singularities and for large time values. The problems of dynamical dimensional reduction, structure of singularities, isotropization, etc., are discussed in this context.  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