全文获取类型
收费全文 | 2381篇 |
免费 | 366篇 |
国内免费 | 163篇 |
专业分类
化学 | 723篇 |
晶体学 | 31篇 |
力学 | 695篇 |
综合类 | 52篇 |
数学 | 382篇 |
物理学 | 1027篇 |
出版年
2024年 | 2篇 |
2023年 | 24篇 |
2022年 | 41篇 |
2021年 | 44篇 |
2020年 | 74篇 |
2019年 | 51篇 |
2018年 | 84篇 |
2017年 | 114篇 |
2016年 | 111篇 |
2015年 | 89篇 |
2014年 | 131篇 |
2013年 | 197篇 |
2012年 | 130篇 |
2011年 | 151篇 |
2010年 | 143篇 |
2009年 | 121篇 |
2008年 | 132篇 |
2007年 | 145篇 |
2006年 | 163篇 |
2005年 | 114篇 |
2004年 | 100篇 |
2003年 | 103篇 |
2002年 | 85篇 |
2001年 | 83篇 |
2000年 | 66篇 |
1999年 | 77篇 |
1998年 | 75篇 |
1997年 | 35篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 25篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 2篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2910条查询结果,搜索用时 15 毫秒
11.
12.
13.
LiuYuqi LiZhigang YahYakun 《Acta Mechanica Solida Sinica》2004,17(1):58-64
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM. 相似文献
14.
15.
带有给定凸切线多边形的保形五次样条逼近 总被引:3,自引:0,他引:3
本讨论带有给定切线多边形的保形逼近问题.给出了一条与给定切线多边形相切的保形五次参数祥条曲线。 相似文献
16.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献
17.
18.
Yu You George W. Kattawar Ping Yang Yong X. Hu Bryan A. Baum 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):470-482
Measurements from depolarized lidars provide a promising method to retrieve both cloud and aerosol properties and a versatile complement to passive satellite-based sensors. For lidar observations of clouds and aerosols, multiple scattering plays an important role in the scattering process. Monte Carlo simulations are carried out to investigate the sensitivity of lidar backscattering depolarization to cloud and aerosol properties. Lidar parameters are chosen to be similar to those of the upcoming space-based CALIPSO lidar. Cases are considered that consist of a single cloud or aerosol layer, as well as a case in which cirrus clouds overlay different types of aerosols. It is demonstrated that besides thermodynamic cloud phase, the depolarized lidar signal may provide additional information on ice or aerosol particle shapes. However, our results show little sensitivity to ice or aerosol particle sizes. Additionally, for the case of multiple but overlapping layers involving both clouds and aerosols, the depolarized lidar contains information that can help identify the particle properties of each layer. 相似文献
19.
Victor A. Kovtunenko 《Mathematical Methods in the Applied Sciences》2003,26(5):359-374
The 3D‐elasticity model of a solid with a plane crack under the stress‐free boundary conditions at the crack is considered. We investigate variations of a solution and of energy functionals with respect to perturbations of the crack front in the plane. The corresponding expansions at least up to the second‐order terms are obtained. The strong derivatives of the solution are constructed as an iterative solution of the same elasticity problem with specified right‐hand sides. Using the expansion of the potential and surface energy, we consider an approximate quadratic form for local shape optimization of the crack front defined by the Griffith criterion. To specify its properties, a procedure of discrete optimization is proposed, which reduces to a matrix variational inequality. At least for a small load we prove its solvability and find a quasi‐static model of the crack growth depending on the loading parameter. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
20.
J. T. Haslinger K. Kunisch G. Peichl 《Computational Optimization and Applications》2003,26(3):231-251
This contribution deals with an efficient method for the numerical realization of the exterior and interior Bernoulli free boundary problems. It is based on a shape optimization approach. The state problems are solved by a fictitious domain solver using boundary Lagrange multipliers. 相似文献