全文获取类型
收费全文 | 4886篇 |
免费 | 543篇 |
国内免费 | 201篇 |
专业分类
化学 | 411篇 |
晶体学 | 11篇 |
力学 | 1023篇 |
综合类 | 30篇 |
数学 | 2200篇 |
物理学 | 1955篇 |
出版年
2024年 | 10篇 |
2023年 | 66篇 |
2022年 | 81篇 |
2021年 | 81篇 |
2020年 | 142篇 |
2019年 | 116篇 |
2018年 | 105篇 |
2017年 | 126篇 |
2016年 | 124篇 |
2015年 | 153篇 |
2014年 | 248篇 |
2013年 | 372篇 |
2012年 | 330篇 |
2011年 | 331篇 |
2010年 | 253篇 |
2009年 | 314篇 |
2008年 | 316篇 |
2007年 | 285篇 |
2006年 | 230篇 |
2005年 | 228篇 |
2004年 | 176篇 |
2003年 | 170篇 |
2002年 | 123篇 |
2001年 | 120篇 |
2000年 | 107篇 |
1999年 | 124篇 |
1998年 | 87篇 |
1997年 | 90篇 |
1996年 | 79篇 |
1995年 | 88篇 |
1994年 | 68篇 |
1993年 | 58篇 |
1992年 | 35篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 37篇 |
1988年 | 28篇 |
1987年 | 27篇 |
1986年 | 31篇 |
1985年 | 29篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1974年 | 3篇 |
排序方式: 共有5630条查询结果,搜索用时 15 毫秒
21.
Marco Dall'Aglio Theodore P. Hill 《Journal of Mathematical Analysis and Applications》2003,281(1):346-361
For fair-division or cake-cutting problems with value functions which are normalized positive measures (i.e., the values are probability measures) maximin-share and minimax-envy inequalities are derived for both continuous and discrete measures. The tools used include classical and recent basic convexity results, as well as ad hoc constructions. Examples are given to show that the envy-minimizing criterion is not Pareto optimal, even if the values are mutually absolutely continuous. In the discrete measure case, sufficient conditions are obtained to guarantee the existence of envy-free partitions. 相似文献
22.
This work is concerned with the maximum principle for optimal control problem governed by magnetohydrodynamic equations, which describe the motion of a viscous incompressible conducting fluid in a magnetic field and consist of a subtle coupling of the Navier-Stokes equation of viscous incompressible fluid flow and the Maxwell equation of electromagnetic field. An integral type state constraint is considered. 相似文献
23.
24.
Various problems associated with optimal path planning for mobile observers such as mobile robots equipped with cameras to obtain maximum visual coverage of a surface in the three-dimensional Euclidean space are considered. The existence of solutions to these problems is discussed first. Then, optimality conditions are derived by considering local path perturbations. Numerical algorithms for solving the corresponding approximate problems are proposed. Detailed solutions to the optimal path planning problems for a few examples are given. 相似文献
25.
本文实验发现具有较大密度和较高速度的93W钨合金长杆模拟弹的穿靶深度反而比密度较小,速度较低的90W钨合金长杆弹的穿靶深度小.针对这一现象,本文从两种材料在侵彻环境下的细观响应特性的差异上给出了有实验根据的合理分析,结论是90W在侵彻环境下较易于形成绝热剪切带,从而在弹头部发生“自锐化”效应所致. 相似文献
26.
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
27.
A review of the optimal stopping problem with more than a single decision maker (DM) is presented in this paper. We classify
the existing literature according to the arrival of the offers, the utility of the DMs, the length of the sequence of offers,
the nature of the game and the number of offers to be selected. We enumerate various definitions for this problem and describe
some dynamic approaches.
Fouad Ben Abdelaziz is on leave from the Institut Superieur de Gestion, University of Tunis, Tunisia e-mail: foued.benabdelaz@isg.run.tn. 相似文献
28.
29.
K. Holmåker 《Journal of Optimization Theory and Applications》1991,71(2):205-235
Some optimization problems concerning a substrate in a fluid are considered. The concentration of the substrate is affected by diffusion, convection, and elimination by enzymes, and the problem is to find the optimal distribution of enzymes. In this paper, the rate of elimination and the transmission coefficient are optimized. Mathematically, these problems are optimal control problems, and they are analyzed by means of Pontryagin's maximum principle. 相似文献
30.
1引言分离流动经常出现在许多实际流动中,对流体机械和飞行器产生重大影响。但由于这种流动具有方向性,变化快,给测量带来了困难。到目前为止,主要有以下三种测量方法:山激光多普勒测速治(*D川;(2)飞行热线(F坊In含*。卜w让e);O)脉冲热线技术(PulsedAVire。‘脉冲热线”比“激光多普勒测速仪”价格低一个数量级,操作简单,是一种比较理想的测量技术。其原理最初由Baner山提出,随后经过BradburyP],Eaton问,Castro*和Fernholz问等人不断发展与完善,目前国外正推广应用在分离流动的研究中。但在国内,尚不多见其… 相似文献