全文获取类型
收费全文 | 12167篇 |
免费 | 1656篇 |
国内免费 | 816篇 |
专业分类
化学 | 802篇 |
晶体学 | 58篇 |
力学 | 4314篇 |
综合类 | 168篇 |
数学 | 5869篇 |
物理学 | 3428篇 |
出版年
2024年 | 11篇 |
2023年 | 119篇 |
2022年 | 183篇 |
2021年 | 211篇 |
2020年 | 328篇 |
2019年 | 272篇 |
2018年 | 322篇 |
2017年 | 372篇 |
2016年 | 416篇 |
2015年 | 295篇 |
2014年 | 546篇 |
2013年 | 907篇 |
2012年 | 625篇 |
2011年 | 705篇 |
2010年 | 605篇 |
2009年 | 698篇 |
2008年 | 678篇 |
2007年 | 732篇 |
2006年 | 697篇 |
2005年 | 677篇 |
2004年 | 603篇 |
2003年 | 575篇 |
2002年 | 535篇 |
2001年 | 490篇 |
2000年 | 443篇 |
1999年 | 426篇 |
1998年 | 416篇 |
1997年 | 321篇 |
1996年 | 273篇 |
1995年 | 207篇 |
1994年 | 148篇 |
1993年 | 121篇 |
1992年 | 133篇 |
1991年 | 114篇 |
1990年 | 82篇 |
1989年 | 54篇 |
1988年 | 42篇 |
1987年 | 42篇 |
1986年 | 36篇 |
1985年 | 40篇 |
1984年 | 30篇 |
1983年 | 29篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1971年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In this paper, a unified approach for analysing finite dimensional approximations to a class of partial differential equations boundary value problems (second‐kind Fredholm differential equations) is introduced. The approach is shown to be general despite of its extremely simple form. In particular, it is expected to be useful in the convergence analysis of finite element methods for solving PDE problems. Three specific examples are presented to illustrate the broad applicability of the approach. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
52.
美式期权定价中非局部问题的有限元方法 总被引:2,自引:1,他引:1
在本文中 ,我们关心的是美式期权的有限元方法 .首先 ,根据 [4 ]我们对所讨论的问题引进一个新奇的实用的方法 ,它涉及到对原问题重新形成准确的数学公式 ,使得数值解的计算可以在非常小的区域上进行 ,从而该算法计算速度快精度高 .进而 ,我们利用超逼近分析技术得到了有限元解关于 L2 -模的最优估计 . 相似文献
53.
54.
A model of two interacting (chemically different) linear polymer chains is solved exactly using the real-space renormalization
group transformation on a family of Sierpinski gasket type fractals and on a truncated 4-simplex lattice. The members of the
family of the Sierpinski gasket-type fractals are characterized by an integer scale factorb which runs from 2 to ∞. The Hausdorff dimensiond
F of these fractals tends to 2 from below asb → ∞. We calculate the contact exponenty for the transition from the State of segregation to a State in which the two chains are entangled forb = 2-5. Using arguments based on the finite-size scaling theory, we show that forb→∞, y = 2 - v(b) d
F, wherev is the end-toend distance exponent of a chain. For a truncated 4-simplex lattice it is shown that the system of two chains
either remains in a State in which these chains are intermingled in such a way that they cannot be told apart, in the sense
that the chemical difference between the polymer chains completely drop out of the thermodynamics of the system, or in a State
in which they are either zipped or entangled. We show the region of existence of these different phases separated by tricritical
lines. The value of the contact exponenty is calculated at the tricritical points. 相似文献
55.
G.N. Gatica 《Applied Mathematics Letters》1997,10(6):29-35
We study the solvability and Galerkin approximation of an exterior hyperelastic interface problem arising in plane elasticity. The weak formulation is obtained from an appropriate combination of a mixed finite element approach with a Dirichlet-to-Neumann method. The derivation of our results is based on some tools from nonlinear functional analysis and the Babuska-Brezzi theory for variational problems with constraints. 相似文献
56.
Houman Borouchaki Abdelhakim Cherouat Patrick Laug Khemais Saanouni 《Comptes Rendus Mecanique》2002,330(10):709-716
The analysis of mechanical structures using the Finite Element Method in the framework of large elastoplastic strain, needs frequent remeshing of the deformed domain during computation. Indeed, the remeshing is due to the large geometrical distortion of finite elements and the adaptation to the physical behavior of the solution. This paper gives the necessary steps to remesh a mechanical structure during large elastoplastic deformations with damage. An important part of this process is constituted by geometrical and physical error estimates. The proposed method is integrated in a computational environment using the ABAQUS/Explicit solver and the BL2D-V2 adaptive mesher. To cite this article: H. Borouchaki et al., C. R. Mecanique 330 (2002) 709–716. 相似文献
57.
N. H. Al-Assady 《Journal of Optimization Theory and Applications》1997,94(3):747-755
We present a method which generates conjugate search directions and maintains the quadratic convergence property, when applied to a quadratic function, even when the line searches are not exact. The method is similar to that given by Dixon, but needs one less vector store. When the method is applied to a number of general functions of different dimensionality, results show the efficiency of the method. 相似文献
58.
Montgomery Multiplication in GF(2k) 总被引:8,自引:0,他引:8
We show that the multiplication operation c=a · b · r-1 in the field GF(2k can be implemented significantly faster in software than the standard multiplication, where r is a special fixed element of the field. This operation is the finite field analogue of the Montgomery multiplication for modular multiplication of integers. We give the bit-level and word-level algorithms for computing the product, perform a thorough performance analysis, and compare the algorithm to the standard multiplication algorithm in GF(2k. The Montgomery multiplication can be used to obtain fast software implementations of the discrete exponentiation operation, and is particularly suitable for cryptographic applications where k is large. 相似文献
59.
60.
In this paper, we provide numerical means to compute the quasi-stationary (QS) distributions inM/GI/1/K queues with state-dependent arrivals andGI/M/1/K queues with state-dependent services. These queues are described as finite quasi-birth-death processes by approximating the general distributions in terms of phase-type distributions. Then, we reduce the problem of obtaining the QS distribution to determining the Perron-Frobenius eigenvalue of some Hessenberg matrix. Based on these arguments, we develop a numerical algorithm to compute the QS distributions. The doubly-limiting conditional distribution is also obtained by following this approach. Since the results obtained are free of phase-type representations, they are applicable for general distributions. Finally, numerical examples are given to demonstrate the power of our method. 相似文献