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   8193篇
  免费   556篇
  国内免费   738篇
化学   150篇
力学   349篇
综合类   113篇
数学   7645篇
物理学   878篇
无线电   352篇
  2024年   16篇
  2023年   98篇
  2022年   109篇
  2021年   109篇
  2020年   185篇
  2019年   198篇
  2018年   174篇
  2017年   221篇
  2016年   208篇
  2015年   189篇
  2014年   379篇
  2013年   632篇
  2012年   310篇
  2011年   431篇
  2010年   393篇
  2009年   486篇
  2008年   581篇
  2007年   589篇
  2006年   505篇
  2005年   499篇
  2004年   369篇
  2003年   387篇
  2002年   306篇
  2001年   275篇
  2000年   243篇
  1999年   242篇
  1998年   224篇
  1997年   213篇
  1996年   143篇
  1995年   92篇
  1994年   80篇
  1993年   63篇
  1992年   60篇
  1991年   61篇
  1990年   32篇
  1989年   32篇
  1988年   33篇
  1987年   19篇
  1986年   26篇
  1985年   44篇
  1984年   32篇
  1983年   20篇
  1982年   25篇
  1981年   31篇
  1980年   20篇
  1979年   26篇
  1978年   24篇
  1977年   17篇
  1976年   16篇
  1973年   6篇
排序方式: 共有9487条查询结果,搜索用时 0 毫秒
71.
In this paper, we first give an interesting operator identity. Furthermore, using the q-exponential operator technique to the multiple q-binomial theorem and q-Gauss summation theorem, we obtain some transformation formulae and summation theorems of multiple basic hypergeometric series.  相似文献   
72.
Let a(k,n) be the k-th coefficient of the n-th cyclotomic polynomials. In 1987, J. Suzuki proved that . In this paper, we improve this result and prove that for any prime p and any integer l≥1, we have
{a(k,pln)∣n,kN}=Z.  相似文献   
73.
Magnetic drug delivery has the potential to target therapy to specific regions in the body, improving efficacy and reducing side effects for treatment of cancer, stroke, infection, and other diseases. Using stationary external magnets, which attract the magnetic drug carriers, this treatment is limited to shallow targets (<5 cm below skin depth using the strongest possible, still safe, practical magnetic fields). We consider dynamic magnetic actuation and present initial results that show it is possible to vary magnets one against the other to focus carriers between them on average. The many remaining tasks for deep targeting in-vivo are then briefly noted.  相似文献   
74.
We study boundary value problems for fractional integro-differential equations involving Caputo derivative of order α ∈ (n-1,n) in Banach spaces. Existence and uniqueness results of solutions are established by virtue of the Holder's inequality, a suitable singular Gronwall's inequality and fixed point theorem via a priori estimate method. At last, examples are given to illustrate the results.  相似文献   
75.
This paper presents a theory of dynamics of closed relations on compact Hausdorff spaces. It contains an investigation of set valued maps and establishes generalizations for some topological aspects of dynamical systems theory, including recurrence, attractor–repeller structure and the Conley decomposition theorem.  相似文献   
76.
ABSTRACT

This paper introduces a class of backward stochastic differential equations (BSDEs), whose coefficients not only depend on the value of its solutions of the present but also the past and the future. For a sufficiently small time delay or a sufficiently small Lipschitz constant, the existence and uniqueness of such BSDEs is obtained. As an adjoint process, a class of stochastic differential equations (SDEs) is introduced, whose coefficients also depend on the present, the past and the future of its solutions. The existence and uniqueness of such SDEs is proved for a sufficiently small time advance or a sufficiently small Lipschitz constant. A duality between such BSDEs and SDEs is established.  相似文献   
77.
The purpose of this paper is to investigate the eight-dimensional non-associative unital division algebras {0}≠A over finite fields, admitting elementary abelian 2-group of automorphisms EAut(A), of order 8, using tools from algebraic geometry.  相似文献   
78.
We show that two simple semiclassical strategies, one based on the Wilson–Sommerfeld rule and the other on the uncertainty principle, yield the exact modified form of the virial theorem for confined systems. An alternative, easier quantum mechanical route to arrive at this result is also sketched. Pilot calculations on confined oscillators reveal decisive trends. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   
79.
The reaction force is a global property of a chemical reaction that arises when applying the Hellmann–Feynmann theorem to the potential energy surface that links reactants, products and transition states. In the present work, the reaction force is defined rigorously from the cartesian components coming out from all forces exerted over each atom of a molecular system during the chemical reaction; it is demonstrated that the reaction force is a scalar property. An erratum to this article can be found at  相似文献   
80.
Factorization theorem plays the central role at high energy colliders to study standard model and beyond standard model physics. The proof of factorization theorem is given by Collins, Soper and Sterman to all orders in perturbation theory by using diagrammatic approach. One might wonder if one can obtain the proof of factorization theorem through symmetry considerations at the lagrangian level. In this paper we provide such a proof.  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