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   1733篇
  免费   106篇
  国内免费   52篇
化学   356篇
晶体学   7篇
力学   80篇
综合类   54篇
数学   869篇
物理学   525篇
  2024年   7篇
  2023年   14篇
  2022年   96篇
  2021年   113篇
  2020年   62篇
  2019年   48篇
  2018年   48篇
  2017年   41篇
  2016年   70篇
  2015年   50篇
  2014年   67篇
  2013年   106篇
  2012年   50篇
  2011年   83篇
  2010年   66篇
  2009年   98篇
  2008年   80篇
  2007年   72篇
  2006年   55篇
  2005年   58篇
  2004年   51篇
  2003年   59篇
  2002年   56篇
  2001年   42篇
  2000年   41篇
  1999年   52篇
  1998年   31篇
  1997年   32篇
  1996年   23篇
  1995年   35篇
  1994年   23篇
  1993年   11篇
  1992年   28篇
  1991年   43篇
  1990年   12篇
  1989年   25篇
  1988年   18篇
  1987年   2篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
  1979年   3篇
  1978年   4篇
  1977年   1篇
  1975年   1篇
  1973年   4篇
排序方式: 共有1891条查询结果,搜索用时 0 毫秒
11.
The nature of hydrologic parameters in reservoir management models is uncertain. In mathematical programming models the uncertainties are dealt with either indirectly (sensitivity analysis of a deterministic model) or directly by applying a chance-constrained type of formulation or some of the stochastic programming techniques (LP and DP based models). Various approaches are reviewed in the paper. Moran's theory of storage is an alternative stochastic modelling approach to mathematical programming techniques. The basis of the approach and its application is presented. Reliability programming is a stochastic technique based on the chance-constrained approach, where the reliabilities of the chance constraints are considered as extra decision variables in the model. The problem of random event treatment in the reservoir management model formulation using reliability programming is addressed in this paper.  相似文献   
12.
13.
This paper presents some results of the relation between wavelet transform and fractal transform. The wavelet transform of the attractor of fractal transform posseses translational and scale invariance. So we speed the fractal image encoding by testing the invariance of the wavelet transform appropriate for image encoding. The classfication scheme of range blocks by wavelet transform is given in this paper.  相似文献   
14.
In this paper, assuming a certain set-theoretic hypothesis, a positive answer is given to a question of H. Kraljevi, namely it is shown that there exists a Lebesgue measurable subsetA of the real line such that the set {c R: A + cA contains an interval} is nonmeasurable. Here the setA + cA = {a + ca: a, a A}. Two other results about sets of the formA + cA are presented.  相似文献   
15.
IfK is a field of characteristic 0 then the following is shown. Iff, g, h: M n (K) K are non-constant solutions of the Binet—Pexider functional equation
  相似文献   
16.
The purpose of this paper is to solve the following Pythagorean functional equation:(e p(x,y) ) 2 ) = q(x,y) 2 + r(x, y) 2, where each ofp(x,y), q(x, y) andr(x, y) is a real-valued unknown harmonic function of the real variablesx, y on the wholexy-planeR 2.The result is as follows.  相似文献   
17.
We solve the functional equation
  相似文献   
18.
LetC m be a compound quadrature formula, i.e.C m is obtained by dividing the interval of integration [a, b] intom subintervals of equal length, and applying the same quadrature formulaQ n to every subinterval. LetR m be the corresponding error functional. Iff (r) > 0 impliesR m [f] > 0 (orR m [f] < 0),=" then=" we=" say=">C m is positive definite (or negative definite, respectively) of orderr. This is the case for most of the well-known quadrature formulas. The assumption thatf (r) > 0 may be weakened to the requirement that all divided differences of orderr off are non-negative. Thenf is calledr-convex. Now letC m be positive definite or negative definite of orderr, and letf be continuous andr-convex. We prove the following direct and inverse theorems for the errorR m [f], where , denotes the modulus of continuity of orderr:
  相似文献   
19.
Applying Bittner's operational calculus we present a method to give approximate solutions of linear partial differential equations of first order
  相似文献   
20.
An exact formula for the various measure dimensions of attractors associated with contracting similitudes is given. An example is constructed showing that for more general affine maps the various measure dimensions are not always equal.Communicated by Michael F. Barnsley.  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