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   11021篇
  免费   1338篇
  国内免费   1275篇
化学   2977篇
晶体学   21篇
力学   321篇
综合类   206篇
数学   8635篇
物理学   1474篇
  2024年   13篇
  2023年   111篇
  2022年   107篇
  2021年   174篇
  2020年   306篇
  2019年   323篇
  2018年   308篇
  2017年   295篇
  2016年   453篇
  2015年   366篇
  2014年   573篇
  2013年   888篇
  2012年   566篇
  2011年   727篇
  2010年   659篇
  2009年   876篇
  2008年   829篇
  2007年   810篇
  2006年   716篇
  2005年   637篇
  2004年   553篇
  2003年   580篇
  2002年   487篇
  2001年   304篇
  2000年   343篇
  1999年   325篇
  1998年   272篇
  1997年   289篇
  1996年   161篇
  1995年   88篇
  1994年   83篇
  1993年   54篇
  1992年   50篇
  1991年   32篇
  1990年   26篇
  1989年   23篇
  1988年   21篇
  1987年   13篇
  1986年   10篇
  1985年   19篇
  1984年   32篇
  1983年   16篇
  1982年   26篇
  1981年   16篇
  1980年   28篇
  1979年   13篇
  1978年   8篇
  1977年   9篇
  1976年   3篇
  1936年   4篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
81.
We describe the relationship between the fuzzy sets and the algebraic hyperstructures. In fact, this paper is a continuation of the ideas presented by Davvaz in (Fuzzy Sets Syst., 117: 477- 484, 2001) and Bhakat and Das in (Fuzzy Sets Syst., 80: 359-368, 1996). The concept of the quasicoincidence of a fuzzy interval value with an interval-valued fuzzy set is introduced and this is a natural generalization of the quasi-coincidence of a fuzzy point in fuzzy sets. By using this new idea, the concept of interval-valued (α,β)-fuzzy sub-hypermodules of a hypermodule is defined. This newly defined interval-valued (α,β)-fuzzy sub-hypermodule is a We shall study such fuzzy sub-hypermodules and sub-hypermodules of a hypermodule. generalization of the usual fuzzy sub-hypermodule. consider the implication-based interval-valued fuzzy  相似文献   
82.
83.
We study the existence and the continuity properties of the boundary values on the real axis of the resolvent of a self-adjoint operator H in the framework of the conjugate operator method initiated by Mourre. We allow the conjugate operator A to be the generator of a C0-semigroup (finer estimates require A to be maximal symmetric) and we consider situations where the first commutator [H,iA] is not comparable to H. The applications include the spectral theory of zero mass quantum field models.  相似文献   
84.
Let SB(X,Y) be the set of the bounded sublinear operators from a Banach space X into a Banach lattice Y. Consider π2(X,Y) the set of 2-summing sublinear operators. We study in this paper a variation of Grothendieck's theorem in the sublinear operators case. We prove under some conditions that every operator in SB(C(K),H) is in π2(C(K),H) for any compact K and any Hilbert H. In the noncommutative case the problem is still open.  相似文献   
85.
本文证明了可分无穷维 Hilbert空间上每个有界线性算子均可写成两个强不可约算子之和 .这回答了文献 [9]中提出一个公开问题  相似文献   
86.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically.  相似文献   
87.
88.
89.
Quantum Hamiltonian systems corresponding to classical systems related by a general canonical transformation are considered. The differential equation to find the unitary operator, which corresponds to the canonical transformation and connects quantum states of the original and transformed systems, is obtained. The propagator associated with their wave functions is found by the unitary operator. Quantum systems related by a linear canonical point transformation are analyzed. The results are tested by finding the wave functions of the under-, critical-, and over-damped harmonic oscillator from the wave functions of the harmonic oscillator, free-particle system, and negative harmonic potential system, using the unitary operator to connect them, respectively.  相似文献   
90.
This is the first part of a work on second order nonlinear, nonmonotone evolution inclusions defined in the framework of an evolution triple of spaces and with a multivalued nonlinearity depending on both x(t) and x(t). In this first part we prove existence and relaxation theorems. We consider the case of an usc, convex valued nonlinearity and we show that for this problem the solution set is nonempty and compact in C^1 (T, H). Also we examine the Isc, nonconvex case and again we prove the existence of solutions. In addition we establish the existence of extremal solutions and by strengthening our hypotheses, we show that the extremal solutions are dense in C^1 (T, H) to the solutions of the original convex problem (strong relaxation). An example of a nonlinear hyperbolic optimal control problem is also discussed.  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