全文获取类型
收费全文 | 14793篇 |
免费 | 1467篇 |
国内免费 | 1495篇 |
专业分类
化学 | 2024篇 |
晶体学 | 26篇 |
力学 | 840篇 |
综合类 | 239篇 |
数学 | 11925篇 |
物理学 | 2701篇 |
出版年
2024年 | 39篇 |
2023年 | 184篇 |
2022年 | 177篇 |
2021年 | 276篇 |
2020年 | 321篇 |
2019年 | 381篇 |
2018年 | 380篇 |
2017年 | 438篇 |
2016年 | 504篇 |
2015年 | 360篇 |
2014年 | 631篇 |
2013年 | 1151篇 |
2012年 | 671篇 |
2011年 | 731篇 |
2010年 | 686篇 |
2009年 | 889篇 |
2008年 | 954篇 |
2007年 | 1018篇 |
2006年 | 903篇 |
2005年 | 843篇 |
2004年 | 705篇 |
2003年 | 628篇 |
2002年 | 652篇 |
2001年 | 566篇 |
2000年 | 514篇 |
1999年 | 526篇 |
1998年 | 416篇 |
1997年 | 380篇 |
1996年 | 300篇 |
1995年 | 215篇 |
1994年 | 183篇 |
1993年 | 136篇 |
1992年 | 130篇 |
1991年 | 107篇 |
1990年 | 80篇 |
1989年 | 64篇 |
1988年 | 59篇 |
1987年 | 55篇 |
1986年 | 52篇 |
1985年 | 79篇 |
1984年 | 71篇 |
1983年 | 27篇 |
1982年 | 54篇 |
1981年 | 30篇 |
1980年 | 43篇 |
1979年 | 37篇 |
1978年 | 26篇 |
1977年 | 25篇 |
1976年 | 17篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
P. G. Hjorth S. L. Kokkendorff S. Markvorsen 《Proceedings of the American Mathematical Society》2002,130(1):175-181
We study finite metric spaces with elements picked from, and distances consistent with, ambient Riemannian manifolds. The concepts of negative type and strictly negative type are reviewed, and the conjecture that hyperbolic spaces are of strictly negative type is settled, in the affirmative. The technique of the proof is subsequently applied to show that every compact manifold of negative type must have trivial fundamental group, and to obtain a necessary criterion for product manifolds to be of negative type.
192.
We consider the semilinear Cauchy problem for a class of pseudo-differential operators generating sub-Markovian semigroups.
Solutions of such problems with negative definite nonlinearity play an important role in constructing branching measure-valued
processes. We establish local existence and uniqueness of solutions in the context of the Dirichlet space associated to the
problem. Comparison and global properties of solutions are also studied.
Accepted 29 August 2001. Online publication 17 December 2001. 相似文献
193.
Numerical methods for the efficient integration of both stiff and nonstiff equations of motion of multibody systems having
the form of differential-algebraic equations (DAE) of index 3 are discussed. Linear multi-step ABM and BDF methods are considered
for the non-iterational integration of nonstiff DAE. The Park method is proposed for integration of stiff equations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
194.
Comparison of Two Reformulation-Linearization Technique Based Linear Programming Relaxations for Polynomial Programming Problems 总被引:3,自引:0,他引:3
In this paper, we compare two strategies for constructing linear programmingrelaxations for polynomial programming problems using aReformulation-Linearization Technique (RLT). RLT involves an automaticreformulation of the problem via the addition of certain nonlinear impliedconstraints that are generated by using the products of the simple boundingrestrictions (among other products), and a subsequent linearization based onvariable redefinitions. We prove that applying RLT directly to the originalpolynomial program produces a bound that dominates in the sense of being atleast as tight as the value obtained when RLT is applied to the jointcollection of all equivalent quadratic problems that could be constructed byrecursively defining additional variables as suggested by Shor. 相似文献
195.
带有弹性碰撞的离散的凝结方程 总被引:1,自引:0,他引:1
带有弹性碰撞的离散的凝结方程是反映粒子增长动力学的数学模型,它刻划了这样一种粒子反应系统;系统中任意两个粒子碰撞后一定的概率或者凝结成为更大的粒子,或者发生弹性碰撞.本文研究了这一系统发生冻肢的可能性,并给出了一个充分条件. 相似文献
196.
有序分组资料的线性趋势检验主要用于检验几个二项总体反应率的线性趋势;在医学与生物学中最典型的用途是研究剂量和反应的关系. 如果用Z检验来代替通常在本检验中所用的卡方检验,就可容易地导出本检验的确切概率计算方法,和其他2×C有序列联表有着相同的形式.本文给出了该检验的确切概率计算方法. 相似文献
197.
198.
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
199.
This paper proposes a fully three‐dimensional non‐linear Euler methodology for solving aerodynamic and acoustic problems in the presence of strong shocks and rarefactions. It uses a discontinuous Galerkin method (DGM) within the element, and a Riemann solver (HLLC) at the boundaries to propagate rarefactions while preserving the entropy condition and capturing shocks with no spurious oscillations. This approach is thought to marry the best aspects of finite element and finite volume methods, achieving conservation while not requiring the solution of a large matrix. Examples in which shock and rarefaction waves are well captured are presented and the propagation of acoustic pulses is well demonstrated. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
200.
In this paper we develop a numerical method for computing higher order local approximations of center manifolds near steady states in Hamiltonian systems. The underlying system is assumed to be large in the sense that a large sparse Jacobian at the equilibrium occurs, for which only a linear solver and a low-dimensional invariant subspace is available. Our method combines this restriction from linear algebra with the requirement that the center manifold is parametrized by a symplectic mapping and that the reduced equation preserves the Hamiltonian form. Our approach can be considered as a special adaptation of a general method from Numer. Math. 80 (1998) 1-38 to the Hamiltonian case such that approximations of the reduced Hamiltonian are obtained simultaneously. As an application we treat a finite difference system for an elliptic problem on an infinite strip. 相似文献