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   5245篇
  免费   574篇
  国内免费   499篇
化学   868篇
晶体学   6篇
力学   495篇
综合类   70篇
数学   3419篇
物理学   1460篇
  2024年   30篇
  2023年   72篇
  2022年   90篇
  2021年   123篇
  2020年   167篇
  2019年   159篇
  2018年   152篇
  2017年   147篇
  2016年   158篇
  2015年   140篇
  2014年   202篇
  2013年   390篇
  2012年   220篇
  2011年   246篇
  2010年   187篇
  2009年   275篇
  2008年   288篇
  2007年   332篇
  2006年   272篇
  2005年   293篇
  2004年   260篇
  2003年   254篇
  2002年   233篇
  2001年   173篇
  2000年   162篇
  1999年   181篇
  1998年   161篇
  1997年   128篇
  1996年   112篇
  1995年   75篇
  1994年   78篇
  1993年   63篇
  1992年   50篇
  1991年   48篇
  1990年   39篇
  1989年   39篇
  1988年   33篇
  1987年   18篇
  1986年   19篇
  1985年   38篇
  1984年   36篇
  1983年   22篇
  1982年   28篇
  1981年   19篇
  1980年   16篇
  1979年   28篇
  1978年   14篇
  1977年   15篇
  1976年   11篇
  1973年   6篇
排序方式: 共有6318条查询结果,搜索用时 989 毫秒
51.
Summary A method of joining two metal cylindrical shafts with adhesive coupling is proposed. Two cylindrical shafts with the same diameter are connected by bonding through a cylindrical coupling with epoxy resin. The strength of the shaft joint under tensile loading and torsional loading is investigated analytically and experimentally. The stress and strain distributions of the shaft joint is analyzed by the finite element method. The analyzed strain distributions in the joint are compared with experimental values. The joint strength is predicted by applying the strength laws of shafts, coupling, adhesive layer and adhesive interface between shaft and adhesive coupling. The effects of the coupling dimension on the joint strength are examined. It is shown that the adhesive shaft joint can transfer the load by which the cylindrical shafts are plastically deformed.This paper was refined by the author, K. Ikegami, during statying at Technische Universität München under the support of Deutscher Akademischer Austauschdients. The author is grateful to Professor Lippmann of Technische Universität München who is the host professor of the support.  相似文献   
52.
In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singular point quantities of a class of cubic polynomial systems, which is used to calculate the first seven singular point quantities. Further, we prove that such a cubic vector field can have maximal seven limit cycles in the neighborhood of infinity. We actually and construct a system that has seven limit cycles. The positions of these limit cycles can be given exactly without constructing the Poincare cycle fields. The technique employed in this work is essentially different from the previously widely used ones. Finally, the isochronous center conditions at infinity are given.  相似文献   
53.
A general relationship between the volume fraction and the specific interfacial area for averaged dispersed two-phase flows is proposed. This relationship, expressed as a basic set of two scalar evolution equations and two vectorial non-uniformity state equations, is an analytical result obtained by a systematic approach using the derivatives of some generalized functions and a local volume-averaging technique. The proposed set of equations was expressed for measurable macroscopic parameters of the system and has the same generality as the averaged transport equations of two-phase flows. By combination of the basic set of equations, called the averaged topological equations (ATEs), second-order ATEs for the volume fraction were found. The second-order ATEs were expressed both by a Lagrangian formulation and by a Eulerian formulation. The importance and physical meaning of the ATEs developed in this study were clarified within the framework of the theory of kinematic waves.  相似文献   
54.
55.
A classical Fermi accelerator model (FAM) is known to show chaotic behavior. The FAM is defined by a free particle bouncing elastically from two rigid walls, one fixed and the other oscillating periodically in time. The central aim of this paper is to connect the quantum and the classical solutions to the FAM in the semiclassical limit. This goal is accomplished using a finite inverted parametric oscillator (FIPO), confined to a box withfixed walls, as an alternative representation of the FAM. In the FIPO representation, an explicit correspondence between classical and quantum limits is accomplished using a Husimi representation of the quasienergy eigenfunctions.  相似文献   
56.
By continuing the probabilistic approach of Deaconu et al. (2001), we derive a stochastic particle approximation for the Smoluchowski coagulation equations. A convergence result for this model is obtained. Under quite stringent hypothesis we obtain a central limit theorem associated with our convergence. In spite of these restrictive technical assumptions, the rate of convergence result is interesting because it is the first obtained in this direction and seems to hold numerically under weaker hypothesis. This result answers a question closely connected to the Open Problem 16 formulated by Aldous (1999).  相似文献   
57.
In this paper we shall give a topological representation for Hilbert algebras that extend the topological representation given by A. Diego in [4]. For implicative semilattices this representation gives a full duality. We shall also consider the representation for Boolean ring.  相似文献   
58.
Portnov  G.  Cruz  I.  Fiffe  R. P.  Arias  F. 《Mechanics of Composite Materials》2004,40(1):37-44
A set of invariants describing the limit regimes of braking disk-type wound composite flywheels is suggested. The limit regime is determined by using a linear failure criterion. It is shown that, for generating short-time impulses of very high power, a set of small identical flywheels is more effective than one large flywheel with an equivalent mass. Particular examples illustrating the theory considered are discussed.  相似文献   
59.
引进集值映射的锥真拟凹概念,讨论一类具有集值映射的广义向量衡问题解的存在性与解集的凸性。  相似文献   
60.
We determine the limiting density of the zeroes of Heine–Stieltjes polynomials (or of any set of points satisfying the conclusion of Heine–Stieltjes Theorem) in the thermodynamic limit and use this to prove a strong law of large numbers for the zeroes.  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