全文获取类型
收费全文 | 4132篇 |
免费 | 280篇 |
国内免费 | 391篇 |
专业分类
化学 | 486篇 |
晶体学 | 8篇 |
力学 | 102篇 |
综合类 | 68篇 |
数学 | 3508篇 |
物理学 | 631篇 |
出版年
2024年 | 6篇 |
2023年 | 28篇 |
2022年 | 36篇 |
2021年 | 66篇 |
2020年 | 99篇 |
2019年 | 91篇 |
2018年 | 105篇 |
2017年 | 104篇 |
2016年 | 115篇 |
2015年 | 82篇 |
2014年 | 197篇 |
2013年 | 329篇 |
2012年 | 170篇 |
2011年 | 170篇 |
2010年 | 197篇 |
2009年 | 268篇 |
2008年 | 283篇 |
2007年 | 315篇 |
2006年 | 253篇 |
2005年 | 205篇 |
2004年 | 174篇 |
2003年 | 211篇 |
2002年 | 181篇 |
2001年 | 167篇 |
2000年 | 136篇 |
1999年 | 131篇 |
1998年 | 116篇 |
1997年 | 102篇 |
1996年 | 81篇 |
1995年 | 45篇 |
1994年 | 45篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 27篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有4803条查询结果,搜索用时 31 毫秒
11.
This paper deals with mathematical human resource planning; more specifically, it suggests a new model for a manpower‐planning system. In general, we study a k‐classed hierarchical system where the workforce demand at each time period is satisfied through internal mobility and recruitment. The motivation for this work is based on various European Union incentives, which promote regional or local government assistance programs that could be exploited by firms not only for hiring and training newcomers, but also to improve the skills and knowledge of their existing personnel. In this respect, in our augmented mobility model we establish a new ‘training/standby’ class, which serves as a manpower inventory position for potential recruits. This class, which may very well be internal or external to the system, is incorporated into the framework of a non‐homogeneous Markov chain model. Furthermore, cost objectives are employed using the goal‐programming approach, under different operating assumptions, in order to minimize the operational cost in the presence of system's constraints and regulations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
12.
The Boltzmann distribution used in the steady-state analysis of the simulated annealing algorithm gives rise to several scale invariant properties. Scale invariance is first presented in the context of parallel independent processors and then extended to an abstract form based on lumping states together to form new aggregate states. These lumped or aggregate states possess all of the mathematical characteristics, forms and relationships of states (solutions) in the original problem in both first and second moments. These scale invariance properties therefore permit new ways of relating objective function values, conditional expectation values, stationary probabilities, rates of change of stationary probabilities and conditional variances. Such properties therefore provide potential applications in analysis, statistical inference and optimization. Directions for future research that take advantage of scale invariance are also discussed. 相似文献
13.
The paper proposes a rational method to derive fairness measures for surfaces. It works in cases where isophotes, reflection lines, planar intersection curves, or other curves are used to judge the fairness of the surface. The surface fairness measure is derived by demanding that all the given curves should be fair with respect to an appropriate curve fairness measure. The method is applied to the field of ship hull design where the curves are plane intersections. The method is extended to the case where one considers, not the fairness of one curve, but the fairness of a one parameter family of curves. Six basic third order invariants by which the fairing measures can be expressed are defined. Furthermore, the geometry of a plane intersection curve is studied, and the variation of the total, the normal, and the geodesic curvature and the geodesic torsion is determined. 相似文献
14.
We study the induced measure obtained from a 1-step Markov measure, supported by a topological Markov chain, after the mapping of the original alphabet onto another one. We give sufficient conditions for the induced measure to be a Gibbs measure (in the sense of Bowen) when the factor system is again a topological Markov chain. This amounts to constructing, when it does exist, the induced potential and proving its Hölder continuity. This is achieved through a matrix method. We provide examples and counterexamples to illustrate our results. 相似文献
15.
16.
研究了Banach空间中非线性混合型微分-积分方程初值问题u′=f(t,u,Tu,Su),u(0)=x0的整体解,完全没有要求f的任何增性,利用Mnch不动点定理和比较结果得到了初值问题整体解的存在性和唯一解,并且给出了一致收敛于唯一解的迭代序列,改进推广和统一了已有的许多结果. 相似文献
17.
18.
Parabolic Capacity and Soft Measures for Nonlinear Equations 总被引:2,自引:0,他引:2
We first introduce, using a functional approach, the notion of capacity related to the parabolic p-Laplace operator. Then we prove a decomposition theorem for measures (in space and time) that do not charge the sets of null capacity. We apply this result to prove existence and uniqueness of renormalized solutions for nonlinear parabolic initial boundary-value problems with such measures as right-hand side. 相似文献
19.
晶体微观结构是晶体材料在特定物理条件下其多个能量极小平衔态在空间形成的某种微尺度的规则分布.几何非线性的连续介质力学理论可以用能量极小化原理来解释晶体微观结构的形成,并用Young测度来刻画平衡态各变体在空间的概率分布.定性的理解与定量地分析和计算晶体材料的微观结构对于发展和改进高级晶体功能材料,如形状记忆合金、铁电体、磁至伸缩材料等,有重要的意义.本文回顾了近年来晶体微观结构数值计算方面的最新进展.介绍了计算晶体微观结构的几种数值方法及有关的数值分析结果。 相似文献
20.
B. Amaziane M. Goncharenko L. Pankratov 《Mathematical Methods in the Applied Sciences》2005,28(15):1847-1865
We study the asymptotic behaviour of the solution of a stationary quasilinear elliptic problem posed in a domain Ω(ε) of asymptotically degenerating measure, i.e. meas Ω(ε) → 0 as ε → 0, where ε is the parameter that characterizes the scale of the microstructure. We obtain the convergence of the solution and the homogenized model of the problem is constructed using the notion of convergence in domains of degenerating measure. Proofs are given using the method of local characteristics of the medium Ω(ε) associated with our problem in a variational form. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献