全文获取类型
收费全文 | 3126篇 |
免费 | 419篇 |
国内免费 | 166篇 |
专业分类
化学 | 407篇 |
晶体学 | 18篇 |
力学 | 1452篇 |
综合类 | 31篇 |
数学 | 314篇 |
物理学 | 1489篇 |
出版年
2024年 | 13篇 |
2023年 | 22篇 |
2022年 | 65篇 |
2021年 | 57篇 |
2020年 | 109篇 |
2019年 | 78篇 |
2018年 | 85篇 |
2017年 | 100篇 |
2016年 | 111篇 |
2015年 | 117篇 |
2014年 | 145篇 |
2013年 | 245篇 |
2012年 | 147篇 |
2011年 | 172篇 |
2010年 | 128篇 |
2009年 | 169篇 |
2008年 | 159篇 |
2007年 | 174篇 |
2006年 | 169篇 |
2005年 | 136篇 |
2004年 | 143篇 |
2003年 | 139篇 |
2002年 | 103篇 |
2001年 | 93篇 |
2000年 | 98篇 |
1999年 | 72篇 |
1998年 | 85篇 |
1997年 | 77篇 |
1996年 | 67篇 |
1995年 | 52篇 |
1994年 | 41篇 |
1993年 | 65篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 38篇 |
1989年 | 32篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有3711条查询结果,搜索用时 15 毫秒
1.
In this work, a continuum model is presented for size and orientation dependent thermal buckling and post-buckling of anisotropic nanoplates considering surface and bulk residual stresses. The model with von-Karman nonlinear strains and material cubic anisotropy of single crystals contains two parameters that reflect the orientation effects. Using Ritz method, closed form solutions are given for buckling temperature and post-buckling deflections. Regarding self-instability states of nanoplates and their recovering at higher temperatures, an experiment is discussed based on low pressurized membranes to verify the predictions. For simply supported nanoplates, the size effects are lowest when they are aligned in [100] direction. When the edges get clamped, the orientation dependence is ignorable and the behavior becomes symmetric about [510] axis. The surface residual stress makes drastic increase in buckling temperature of thinner nanoplates for which a minimum thickness is pointed to stay far from material softening at higher temperatures. Deflection of [100]-oriented buckled nanoplates is higher than [110] ones but this reverses at higher temperatures. The results for long nanoplates show that the buckling mode numbers are changed by orientation which is verified by FEM. 相似文献
2.
采用DIS数字信息化系统,对不同浓度的蓝墨水溶液在激光光源照射下的透射平均照度及照度分布图像进行实验研究,得到了平均照度值随溶液浓度变化的规律。对不同颜色塑料膜片对白炽灯光源透过照度值及照度分布图像进行实验研究得到及其相关之规律。 相似文献
3.
Stress-Strain State in the Zone of Load Transfer in a Composite Specimen under Uniaxial Tension 总被引:2,自引:2,他引:0
Kulakov V. L. Tarnopol'skii Yu. M. Arnautov A. K. Rytter J. 《Mechanics of Composite Materials》2004,40(2):91-100
The stress-strain state in the zone of load transfer in a uniaxially stretched specimen made of a unidirectional epoxy carbon-fiber-reinforced plastic (CFRP) is investigated. A parametric analysis of the influence of geometric and mechanical characteristics of the specimen on its stress-strain state is performed by means of finite-element modeling. The parameters allowing us to significantly reduce the dangerous concentration of transverse and tangential stresses are revealed. The mechanical tensile characteristics of a high-strength pultruded unidirectional CFRP are determined experimentally, and the size effect of its strength is estimated. 相似文献
4.
A model is developed for the flow of a slightly compressible fluid through a saturated inelastic porous medium. The initial‐boundary‐value problem is a system that consists of the diffusion equation for the fluid coupled to the momentum equation for the porous solid together with a constitutive law which includes a possibly hysteretic relation of elasto‐visco‐plastic type. The variational form of this problem in Hilbert space is a non‐linear evolution equation for which the existence and uniqueness of a global strong solution is proved by means of monotonicity methods. Various degenerate situations are permitted, such as incompressible fluid, negligible porosity, or a quasi‐static momentum equation. The essential sufficient conditions for the well‐posedness of the system consist of an ellipticity condition on the term for diffusion of fluid and either a viscous or a hardening assumption in the constitutive relation for the porous solid. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
5.
Houman Borouchaki Abdelhakim Cherouat Patrick Laug Khemais Saanouni 《Comptes Rendus Mecanique》2002,330(10):709-716
The analysis of mechanical structures using the Finite Element Method in the framework of large elastoplastic strain, needs frequent remeshing of the deformed domain during computation. Indeed, the remeshing is due to the large geometrical distortion of finite elements and the adaptation to the physical behavior of the solution. This paper gives the necessary steps to remesh a mechanical structure during large elastoplastic deformations with damage. An important part of this process is constituted by geometrical and physical error estimates. The proposed method is integrated in a computational environment using the ABAQUS/Explicit solver and the BL2D-V2 adaptive mesher. To cite this article: H. Borouchaki et al., C. R. Mecanique 330 (2002) 709–716. 相似文献
6.
7.
8.
Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube. 相似文献
9.
10.
抽吸和压力梯度在层流边界层转捩过程中的作用 总被引:1,自引:0,他引:1
用空间模式的二次稳定性理论研究了抽吸和压力梯度对边界层三维亚谐扰动流动稳定性的影响.数值结果表明,固体边界上的抽吸有明显的层流控制作用,逆压梯度则有较强的不稳定作用. 相似文献