全文获取类型
收费全文 | 3616篇 |
免费 | 536篇 |
国内免费 | 324篇 |
专业分类
化学 | 654篇 |
晶体学 | 45篇 |
力学 | 1653篇 |
综合类 | 71篇 |
数学 | 918篇 |
物理学 | 1135篇 |
出版年
2024年 | 13篇 |
2023年 | 32篇 |
2022年 | 74篇 |
2021年 | 84篇 |
2020年 | 123篇 |
2019年 | 107篇 |
2018年 | 92篇 |
2017年 | 143篇 |
2016年 | 161篇 |
2015年 | 131篇 |
2014年 | 156篇 |
2013年 | 294篇 |
2012年 | 174篇 |
2011年 | 210篇 |
2010年 | 157篇 |
2009年 | 193篇 |
2008年 | 226篇 |
2007年 | 216篇 |
2006年 | 192篇 |
2005年 | 196篇 |
2004年 | 174篇 |
2003年 | 175篇 |
2002年 | 135篇 |
2001年 | 138篇 |
2000年 | 132篇 |
1999年 | 129篇 |
1998年 | 84篇 |
1997年 | 78篇 |
1996年 | 87篇 |
1995年 | 50篇 |
1994年 | 57篇 |
1993年 | 48篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1972年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4476条查询结果,搜索用时 78 毫秒
21.
杨青 《高等学校计算数学学报(英文版)》2003,12(2)
The mathematical model of semiconductor devices is described by the initial boundary value problem of a system of three nonlinear partial differential equations. One equation in elliptic form is for the electrostatic potential; two equations of convection-dominated diffusion type are for the electron and hole concentrations. Finite volume element procedure are put forward for the electrostatic potential, while upwind 相似文献
22.
Direct Shooting Method for the Numerical Solution of Higher-Index DAE Optimal Control Problems 总被引:3,自引:0,他引:3
A method for the numerical solution of state-constrained optimal control problems subject to higher-index differential-algebraic equation (DAE) systems is introduced. For a broad and important class of DAE systems (semiexplicit systems with algebraic variables of different index), a direct multiple shooting method is developed. The multiple shooting method is based on the discretization of the optimal control problem and its transformation into a finite-dimensional nonlinear programming problem (NLP). Special attention is turned to the mandatory calculation of consistent initial values at the multiple shooting nodes within the iterative solution process of (NLP). Two different methods are proposed. The projection method guarantees consistency within each iteration, whereas the relaxation method achieves consistency only at an optimal solution. An illustrative example completes this article. 相似文献
23.
The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system. 相似文献
24.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.
25.
在应变速率为5.56×10-5s-1—5.56×10-3s-1的范围内,在不同温度下(从223K至773K),对3004铝合金进行系列拉伸试验,探索其锯齿屈服规律;通过激活能的计算、内耗研究、微观组织观察和能谱分析,探讨锯齿屈服的机理与物理本质.结果表明,3004铝合金在形变过程中会出现动态应变时效现象;发现了一种“反常”的锯齿屈服现象:在出现锯齿屈服的温区内,存在锯齿屈服临界应变量转变温度Tt,
关键词:
动态应变时效
锯齿屈服
铝合金
内耗 相似文献
26.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献
27.
由于混凝土材料理化特性的差异,高强混凝土的弯压极限应变明显地小于普通混凝土,依据试验结果分析了高强混凝土的弯压极限应变变化规律,并给出了它的计算公式. 相似文献
28.
We investigate linear parabolic systems with coupled nonsmooth capacities and mixed boundary conditions. We prove generalized resolvent estimates in W?1, p spaces. The method is an appropriate modification of a technique introduced by Agmon to obtain Lp estimates for resolvents of elliptic differential operators in the case of smooth boundary conditions. Moreover, we establish an existence and uniqueness result. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
29.
We use boundary value methods to compute consistent initial values for fully implicit nonlinear differential-algebraic equations.
The obtained algorithm uses variable order formulae and a deferred correction technique to evaluate the error. A rigorous
theory is stated for nonlinear index 1, 2 and 3 DAEs of Hessenberg form. Numerical tests on classical index 1, 2 and 3 DAE
problems are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
30.
This paper presents a generalized Adadorov theory for anisotropic thin—walled beams. The theory takes account of the shear strain of the middle surface, which exerts a significant influence on the anisotropic thin-walled beams. A new approach is established to solve the governing equations, which have the same form for both open and closed section beams. The numerical examples show that the effects of the shear strain cannot be neglected for this class of beams.This work was part of research project supported by the National Natural Science Foundation of China 相似文献