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   6970篇
  免费   614篇
  国内免费   527篇
化学   235篇
晶体学   2篇
力学   1007篇
综合类   147篇
数学   5669篇
物理学   1051篇
  2024年   11篇
  2023年   65篇
  2022年   60篇
  2021年   77篇
  2020年   158篇
  2019年   141篇
  2018年   154篇
  2017年   201篇
  2016年   164篇
  2015年   144篇
  2014年   314篇
  2013年   569篇
  2012年   270篇
  2011年   481篇
  2010年   351篇
  2009年   421篇
  2008年   477篇
  2007年   429篇
  2006年   427篇
  2005年   371篇
  2004年   300篇
  2003年   331篇
  2002年   296篇
  2001年   225篇
  2000年   219篇
  1999年   222篇
  1998年   231篇
  1997年   186篇
  1996年   126篇
  1995年   105篇
  1994年   107篇
  1993年   69篇
  1992年   51篇
  1991年   36篇
  1990年   41篇
  1989年   22篇
  1988年   26篇
  1987年   25篇
  1986年   25篇
  1985年   18篇
  1984年   28篇
  1983年   12篇
  1982年   25篇
  1981年   22篇
  1980年   14篇
  1979年   9篇
  1978年   16篇
  1977年   8篇
  1976年   6篇
  1973年   6篇
排序方式: 共有8111条查询结果,搜索用时 203 毫秒
51.
Let μ+(t) and μ(t) be the locations of the maximum and minimum, respectively, of a standard Brownian motion in the interval [0,t]. We establish a joint integral test for the lower functions of μ+(t) and μ(t), in the sense of Paul Lévy. In particular, it yields the law of the iterated logarithm for max(μ+(t),μ(t)) as a straightforward consequence. Our result is in agreement with well-known theorems of Chung and Erdős [(1952) Trans. Amer. Math. Soc. 72, 179–186.], and Csáki, F?ldes and Révész [(1987) Prob. Theory Relat. Fields 76, 477–497].   相似文献   
52.
The application of multi-attribute utility theory based on the Choquet integral requires the prior identification of a capacity if the utility scale is unipolar, or of a bi-capacity if the utility scale is bipolar. In order to implement a minimum distance principle for capacity or bi-capacity approximation or identification, quadratic distances between capacities and bi-capacities are studied. The proposed approach, consisting in solving a strictly convex quadratic program, has been implemented within the GNU R kappalab package for capacity and nonadditive integral manipulation. Its application is illustrated on two examples.   相似文献   
53.
We review the Lorentz-covariant approach to loop quantum gravity. This approach solves the Immirzi parameter problem occurring in the standard loop approach based on the SU(2) gauge group. We show that there exists a unique loop quantization preserving all the classical symmetries at the quantum level and that the results obtained with it, such as the area operator spectrum, are independent of the Immirzi parameter. The standard SU(2) approach violates the diffeomorphism invariance and is therefore an incorrect quantization of gravity.  相似文献   
54.
We reformulate and prove the Hyers–Ulam–Rassias stability of Cauchy equation in the space of Schwartz tempered distributions and Fourier hyperfunctions.  相似文献   
55.
A class of Cauchy problems for interesting complicated periodic pseudodifferential equations is considered. By the Galerkin-wavelet method and with weak solutions one can find sufficient conditions to establish convergence estimates of weak Galerkin-wavelet solutions to a Cauchy problem for this class of equations.

  相似文献   

56.
正交变换在重积分中某些应用   总被引:2,自引:0,他引:2  
正交变换是代数学的基本内容 ,其用途十分广泛 .重积分的计算往往存在技术性的困难 ,若利用“正交变换”的有关理论去解决某些重积分的计算问题是颇有功效的 .本文将以“正交变换”为工具 ,简洁的处理重积分的某些问题  相似文献   
57.
Janssen  K. 《Potential Analysis》2003,19(3):289-299
We show that functions which are invariant for suitable product semigroups (one of which is a quasi-Poisson semigroup on a general state space) decompose into a singular eigen-function and a mixture of products of minimal eigen-functions.  相似文献   
58.
A linear operator in a separable Hilbert space is called a quasinormal one if it is a sum of a normal operator and a compact one. In the paper, bounds for the spectrum of quasinormal operators are established. In addition, the lower estimate for the spectral radius is derived. Under some restrictions, that estimate improves the well-known results. Applications to integral operators and matrices are discussed. Our results are new even in the finite-dimensional case.

  相似文献   

59.
Radkevich  E. V. 《Mathematical Notes》2003,73(3-4):551-561
In this paper, we study the linearization of the Cauchy problem and the mixed problem for the system of Grad--Hermite moments in nonequilibrium thermodynamics in the neighborhood of the equilibrium state. Stability conditions for solutions of the Cauchy problem are proved as a generalization of the classical Hermite--Biller theorem on stable polynomials. For the mixed problem, we prove an analog of the Vishik--Lyusternik theorem on small singular perturbations of general elliptic problems. The last observation allows us to introduce the Shapiro--Lopatinskii condition, which implies the well-posedness of the mixed problem.  相似文献   
60.
This paper considers the following Cauchy problem for semilinear wave equations in n spacedimensions□φ = F( φ),φ(0, x) = f(x), tφ(0, x) = g(x),The minimal value of s is determined such that the above Cauchy problem is locally well-posed in Hs. It turns out that for the general equation s must satisfyThis is due to Ponce and Sideris (when n = 3) and Tataru (when n ≥ 5). The purpose of thispaper is to supplement with a proof in the case n = 2, 4.  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