全文获取类型
收费全文 | 41054篇 |
免费 | 5282篇 |
国内免费 | 4156篇 |
专业分类
化学 | 11019篇 |
晶体学 | 963篇 |
力学 | 9754篇 |
综合类 | 564篇 |
数学 | 14720篇 |
物理学 | 13472篇 |
出版年
2024年 | 102篇 |
2023年 | 465篇 |
2022年 | 831篇 |
2021年 | 944篇 |
2020年 | 1197篇 |
2019年 | 1033篇 |
2018年 | 1059篇 |
2017年 | 1472篇 |
2016年 | 1652篇 |
2015年 | 1305篇 |
2014年 | 2112篇 |
2013年 | 2942篇 |
2012年 | 2515篇 |
2011年 | 2887篇 |
2010年 | 2444篇 |
2009年 | 2700篇 |
2008年 | 2593篇 |
2007年 | 2588篇 |
2006年 | 2385篇 |
2005年 | 2215篇 |
2004年 | 1897篇 |
2003年 | 1705篇 |
2002年 | 1522篇 |
2001年 | 1277篇 |
2000年 | 1197篇 |
1999年 | 1082篇 |
1998年 | 999篇 |
1997年 | 846篇 |
1996年 | 697篇 |
1995年 | 589篇 |
1994年 | 544篇 |
1993年 | 439篇 |
1992年 | 450篇 |
1991年 | 345篇 |
1990年 | 273篇 |
1989年 | 211篇 |
1988年 | 176篇 |
1987年 | 127篇 |
1986年 | 86篇 |
1985年 | 114篇 |
1984年 | 107篇 |
1983年 | 53篇 |
1982年 | 70篇 |
1981年 | 50篇 |
1980年 | 26篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 37篇 |
1976年 | 13篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The system design must be started from the concept with low cost and high performance. In this point, the topological shape of the structure is very important in the view of the structural rigidities and light-weight design.In this paper, the optimization methodology is presented in the design stage of the large optical mirror. We obtain the optimal layout through the topology optimization and then design the details through the size or shape optimization for structural rigidity. 相似文献
92.
Alan L. Andrew 《BIT Numerical Mathematics》2003,43(3):485-503
The asymptotic correction technique of Paine, de Hoog and Anderssen can dramatically improve the accuracy of finite difference or finite element eigenvalues at negligible extra cost if closed form expressions are available for the errors in a simpler related problem. This paper gives closed form expressions for the errors in the eigenvalues of certain Sturm–Liouville problems obtained by various methods, thereby increasing the range of problems for which asymptotic correction can achieve maximum efficiency. It also investigates implementation of the method for more general problems. 相似文献
93.
This paper deals with a computational analysis of the influence of the pressing method and part geometry on the final density
distribution in the cold compaction process of ceramic alumina powders. The analysis is based on the explicit finite-element
model proposed and validated in a previous study. The mechanical behavior of the processing material is described using a
multisurface elastoplastic model, the modified Drucker-Prager/Cap model
Published in Prikladnaya Mekhanika, Vol. 43, No. 10, pp. 129–134, October 2007. 相似文献
94.
Mohamed El-Gebeily Donal O'Regan 《Journal of Mathematical Analysis and Applications》2007,334(1):140-156
Existence theory is developed for the equation ?(u)=F(u), where ? is a formally self-adjoint singular second-order differential expression and F is nonlinear. The problem is treated in a Hilbert space and we do not require the operators induced by ? to have completely continuous resolvents. Nonlinear boundary conditions are allowed. Also, F is assumed to be weakly continuous and monotone at one point. Boundary behavior of functions associated with the domains of definitions of the operators associated with ? in the singular case is investigated. A special class of self-adjoint operators associated with ? is obtained. 相似文献
95.
Lower-dimensional linear complementarity problem approaches to the solution of a bi-obstacle problem
A globally convergent Broyden-like method for solving a bi-obstacle problem is proposed based on its equivalent lower-dimensional linear complementarity problem. A suitable line search technique is introduced here. The global and superlinear convergence of the method is verified under appropriate assumptions. 相似文献
96.
Athanassios G. Bratsos 《Numerical Algorithms》2007,46(1):45-58
A predictor–corrector (P-C) scheme is applied successfully to a nonlinear method arising from the use of rational approximants
to the matrix-exponential term in a three-time level recurrence relation. The resulting nonlinear finite-difference scheme,
which is analyzed for local truncation error and stability, is solved using a P-C scheme, in which the predictor and the corrector
are explicit schemes of order 2. This scheme is accelerated by using a modification (MPC) in which the already evaluated values
are used for the corrector. The behaviour of the P-C/MPC schemes is tested numerically on the Boussinesq equation already
known from the bibliography free of boundary conditions. The numerical results are derived for both the bad and the good Boussinesq
equation and conclusions from the relevant known results are derived.
相似文献
97.
René Meziat Diego Patiño Pablo Pedregal 《Computational Optimization and Applications》2007,38(1):147-171
We propose an alternative method for computing effectively the solution of non-linear, fixed-terminal-time, optimal control
problems when they are given in Lagrange, Bolza or Mayer forms. This method works well when the nonlinearities in the control
variable can be expressed as polynomials. The essential of this proposal is the transformation of a non-linear, non-convex
optimal control problem into an equivalent optimal control problem with linear and convex structure. The method is based on
global optimization of polynomials by the method of moments. With this method we can determine either the existence or lacking
of minimizers. In addition, we can calculate generalized solutions when the original problem lacks of minimizers. We also
present the numerical schemes to solve several examples arising in science and technology. 相似文献
98.
Zhiyue Zhang Dingwen Deng 《Numerical Methods for Partial Differential Equations》2007,23(6):1530-1559
A modified backward difference time discretization is presented for Galerkin approximations for nonlinear hyperbolic equation in two space variables. This procedure uses a local approximation of the coefficients based on patches of finite elements with these procedures, a multidimensional problem can be solved as a series of one‐dimensional problems. Optimal order H01 and L2 error estimates are derived. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
99.
In this paper, we suggest and analyze a new two-step predictor–corrector type iterative method free from second derivatives for solving nonlinear equations of the type f(x)=0. This new method includes the two-step Newton method as a special case. We prove that the new iterative method is of fourth-order. Several examples are given to illustrate the efficiency of this new method and its comparison with other iterative methods. This method can be considered as a significant improvement of the Newton method and its variant forms. 相似文献
100.
A. Gorban' 《Mathematical and Computer Modelling》2002,35(13):1-1375
An explicitly solvable analog of the Kirchhoff flow for the case of a semipenetrable obstacle is considered. Its application to estimating the efficiency of free flow turbines is discussed. 相似文献