全文获取类型
收费全文 | 2400篇 |
免费 | 258篇 |
国内免费 | 169篇 |
专业分类
化学 | 214篇 |
晶体学 | 7篇 |
力学 | 465篇 |
综合类 | 55篇 |
数学 | 1167篇 |
物理学 | 919篇 |
出版年
2023年 | 19篇 |
2022年 | 23篇 |
2021年 | 41篇 |
2020年 | 59篇 |
2019年 | 41篇 |
2018年 | 66篇 |
2017年 | 64篇 |
2016年 | 66篇 |
2015年 | 57篇 |
2014年 | 121篇 |
2013年 | 194篇 |
2012年 | 127篇 |
2011年 | 156篇 |
2010年 | 104篇 |
2009年 | 152篇 |
2008年 | 153篇 |
2007年 | 157篇 |
2006年 | 138篇 |
2005年 | 113篇 |
2004年 | 117篇 |
2003年 | 112篇 |
2002年 | 97篇 |
2001年 | 81篇 |
2000年 | 68篇 |
1999年 | 64篇 |
1998年 | 50篇 |
1997年 | 54篇 |
1996年 | 43篇 |
1995年 | 38篇 |
1994年 | 33篇 |
1993年 | 30篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 6篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有2827条查询结果,搜索用时 169 毫秒
1.
2.
3.
4.
This paper presents an enhanced version of the elasto-plastic model for partially saturated soil first proposed by Bolzon,
Schrefler and Zienkiewicz in 1996, “BSZ” model, which uses the effective stress tensor and suction as independent stress variables.
It is recalled that the effective stress tensor proposed by Lewis and Schrefler in 1982 is thermodynamically consistent and,
compared with other choices of stress tensors, results particularly suitable for partially saturated soil mechanics. A hydraulic
constitutive relationship and a hydraulic hysteresis are introduced in the model, to take into account the irreversible deformation
during cyclic drying and wetting until structural collapse. For this reason the plastic rate of strain is split into the sum
of two components: one depending on the effective stress tensor and the other one on suction. This is the new feature of the
BSZ model. This enhanced model is then cast into a thermodynamical framework at macroscopic level and it is shown that it
is possible to derive the constitutive law from the Helmholtz free energy and a dissipation function, both for associative
and non- associative plasticity. Finally the model predictions have been compared with experimental data for Sion slime, with
particular emphasis on the deviatoric part, and model predictions of hysteretic behaviour have been investigated in case of
a wetting and drying cycle on compacted betonite–kaolin. 相似文献
5.
V. I. Sakharov 《Fluid Dynamics》2007,42(6):1007-1016
The results of numerical simulation are presented for thermally and chemically nonequilibrium air plasma flows in a plasmatron discharge channel and underexpanded dissociated and partially ionized air jets flowing past a cylindrical model with a blunt leading edge and cooled copper surface under the experimental conditions realized in a VGU-4 100 kW induction plasmatron (Institute for Problems in Mechanics of the Russian Academy of Sciences) (see, for example, [1, 2]). The nonequilibrium excitation of the vibrational degrees of freedom of the molecules in the modal approximation and the difference between the electron and translational heavy-particle temperatures are taken into account in the calculations. The calculated data on the heat transfer and pressure at the stagnation point are compared with the results obtained within the framework of the thermally equilibrium model. Comparison with the experimental data obtained in the Institute for Problem in Mechanics of the Russian Academy of Sciences (Laboratory for interaction between plasma and radiation and materials) and kindly provided for comparison purposes gives satisfactory agreement. 相似文献
6.
We investigate the effects of adding uniformity requirements to concepts in computable structure theory such as computable categoricity (of a structure) and intrinsic computability (of a relation on a computable structure). We consider and compare two different notions of uniformity, previously studied by Kudinov and by Ventsov. We discuss some of their results and establish new ones, while also exploring the connections with the relative computable structure theory of Ash, Knight, Manasse, and Slaman and Chisholm and with previous work of Ash, Knight, and Slaman on uniformity in a general computable structure-theoretical setting. 相似文献
7.
8.
Tony Donnelly 《Applied Surface Science》2006,252(13):4445-4448
Ultra-thin (0.5-5 nm) films of Ag have been prepared by pulsed laser deposition in vacuum using a 26 ns KrF excimer laser at 1 J cm−2. The deposition was controlled using a Langmuir ion probe and a quartz crystal thickness monitor. Transmission electron microscopy showed that the films are not continuous, but are structured on nanometer size scales. Optical absorption spectra showed the expected surface plasmon resonance feature, which shifted to longer wavelength and increased in strength as the equivalent film thickness was increased. It is shown that Maxwell Garnett effective medium theory can be used to calculate the main features of optical absorption spectra. 相似文献
9.
用三个关系式与Mathematica软件求第二类自然数幂和公式 总被引:1,自引:1,他引:0
首先介绍三个第二类自然数幂和关系式并对其中的两式给出证明,接着利用这些关系式与数学软件M athem atica4.0,给出求解第二类自然数幂和公式的若干机械计算方法. 相似文献
10.
对覆盖广义Rough集中的隶属关系、隶属函数进行了定义,并利用隶属函数定义了集合的Rough包含与Rough相等,得到一些与Pawlak的Rough集不同的性质。 相似文献