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   1342篇
  免费   113篇
  国内免费   100篇
化学   12篇
力学   167篇
综合类   30篇
数学   1132篇
物理学   214篇
  2024年   2篇
  2023年   13篇
  2022年   10篇
  2021年   14篇
  2020年   31篇
  2019年   28篇
  2018年   25篇
  2017年   46篇
  2016年   36篇
  2015年   29篇
  2014年   60篇
  2013年   84篇
  2012年   73篇
  2011年   74篇
  2010年   65篇
  2009年   83篇
  2008年   84篇
  2007年   102篇
  2006年   80篇
  2005年   84篇
  2004年   58篇
  2003年   56篇
  2002年   48篇
  2001年   44篇
  2000年   44篇
  1999年   35篇
  1998年   31篇
  1997年   29篇
  1996年   22篇
  1995年   16篇
  1994年   20篇
  1993年   14篇
  1992年   9篇
  1991年   13篇
  1990年   10篇
  1989年   3篇
  1988年   4篇
  1987年   8篇
  1985年   14篇
  1984年   2篇
  1983年   2篇
  1982年   5篇
  1981年   7篇
  1980年   6篇
  1979年   8篇
  1978年   9篇
  1977年   8篇
  1976年   3篇
  1971年   1篇
  1957年   1篇
排序方式: 共有1555条查询结果,搜索用时 31 毫秒
61.
The results of an investigation of the reflection spectrum of the human tympanic membrane in the visible and near IR ranges ( = 400–900 nm) are reported.  相似文献   
62.
Consider the stochastic partial differential equationdu (t,x) = (t)u (t, x)dt + dW Q(t,x), 0 t T where = 2/x 2, and is a class of positive valued functions. We obtain an estimator for the linear multiplier (t) and establish the consistency, rate of convergence and asymptotic normality of this estimator as 0.  相似文献   
63.
In radar, planar phased array antenna plays vital role in electronic scanning in the azimuth and elevation direction to the horizon. In most operations using planar phased array both the coordinates of azimuth and elevation, are steered electronically. In this paper a conceptual schematic of a phased array antenna with programmable time delay units has been presented. It is shown that by suitably exploiting the time delay matrix one can have electronic beam rotation around the target axis as required in conical scan. Thus both the elevation and azimuth motors in conical scan system are replaced by electronic scanning. Heuristically, we have selected eight consecutive points for beam rotation in a polygon shape and can also be extended almost circular shape by increasing number of array elements and phase shifter (delays) in the delay matrix. The array requires dual control of phase gradient and individual phase values. The whole array is controlled by micro-controller. This presents exciting possibilities in radar operation.  相似文献   
64.
《Optimization》2012,61(2):133-161
The aim of this article is to give a survey of some basic theory of semi-infinite programming. In particular, we discuss various approaches to derivations of duality, discretization, and first- and second-order optimality conditions. Some of the surveyed results are well known while others seem to be less noticed in that area of research.  相似文献   
65.
66.
In the present paper we answer two questions raised by Barbilian in 1960. First, we study how far can the hypothesis of Barbilian’s metrization procedure can be relaxed. Then, we prove that Barbilian’s metrization procedure in the plane generates either Riemannian metrics or Lagrance generalized metrics not reducible to Finslerian or Langrangian metrics.  相似文献   
67.
It is shown that the multiplier norm of a shifted Jacobi multiplier sequence can be estimated by the (same) multiplier norm of the original sequence uniformly with respect to the shift. Muckenhoupt’s transplantation theorem for Jacobi series is used essentially, for which also a functional analytic understanding is given in terms of the minimality of the Jacobi system in weighted L p -spaces.   相似文献   
68.
杨金龙  黄永畅 《中国物理 C》2008,32(10):788-792
We use the improved Faddeev-Jackiw quantization method to quantize the electromagnetic field and its Lagrange multiplier fields. The method's comparison with the usual Faddeev-Jackiw method and the Dirac method is given. We show that this method is equivalent to the Dirac method and also retains all the merits of the usual Faddeev-Jackiw method. Moreover, it is simpler than the usual one if one needs to obtain new secondary constraints. Therefore, the improved Faddeev-Jackiw method is essential. Meanwhile, we find the new meaning of the Lagrange multipliers and explain the Faddeev-Jackiw generalized brackets concerning the Lagrange multipliers.  相似文献   
69.
The aim of this paper is to point out some sufficient constraint qualification conditions ensuring the boundedness of a set of Lagrange multipliers for vectorial optimization problems in infinite dimension. In some (smooth) cases these conditions turn out to be necessary for the existence of multipliers as well.  相似文献   
70.
This article shows that finite-dimensional multiplier rules, which are based on the limiting subdifferential, can be proved by Ekeland's variational principle and some basic calculus tools of the generalized differentiation theory introduced by B. S. Mordukhovich. Consequences of a limiting constraint qualification, which yields the normal form of the multiplier rules, stability and calmness of optimization problems, are investigated in detail.  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