全文获取类型
收费全文 | 4290篇 |
免费 | 679篇 |
国内免费 | 525篇 |
专业分类
化学 | 2021篇 |
晶体学 | 65篇 |
力学 | 1621篇 |
综合类 | 30篇 |
数学 | 650篇 |
物理学 | 1107篇 |
出版年
2024年 | 8篇 |
2023年 | 63篇 |
2022年 | 100篇 |
2021年 | 135篇 |
2020年 | 223篇 |
2019年 | 157篇 |
2018年 | 176篇 |
2017年 | 142篇 |
2016年 | 212篇 |
2015年 | 182篇 |
2014年 | 215篇 |
2013年 | 322篇 |
2012年 | 245篇 |
2011年 | 243篇 |
2010年 | 203篇 |
2009年 | 209篇 |
2008年 | 232篇 |
2007年 | 234篇 |
2006年 | 272篇 |
2005年 | 228篇 |
2004年 | 208篇 |
2003年 | 216篇 |
2002年 | 164篇 |
2001年 | 113篇 |
2000年 | 127篇 |
1999年 | 106篇 |
1998年 | 85篇 |
1997年 | 99篇 |
1996年 | 81篇 |
1995年 | 78篇 |
1994年 | 63篇 |
1993年 | 54篇 |
1992年 | 47篇 |
1991年 | 48篇 |
1990年 | 40篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 20篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有5494条查询结果,搜索用时 15 毫秒
91.
92.
本文用样条边界元法分析轴对称圆形基础板的非线性非光滑接触。除事先给出外力与地基表面位移的对应关系外,地基的模型、板的厚薄(Reissner/Kirchhoff型)和外荷载沿径向的分布均可是任意的。文中将地基反力看作板的外载,对变量沿径向采用不等距祥条插值,并用无地基效应的板基本解。算例表明本文方法只要用少量自由度,便可得到令人满意的结果。 相似文献
93.
The flow of a second-grade fluid past a porous plate subject to either suction or blowing at the plate has been studied. A
modified model of second-grade fluid that has shear-dependent viscosity and can predict the normal stress difference is used.
The differential equations governing the flow are solved using homotopy analysis method (HAM). Expressions for the velocity
have been constructed and discussed with the help of graphs. Analysis of the obtained results showed that the flow is appreciably
influenced by the material and normal stress coefficient. Several results of interest are deduced as the particular cases
of the presented analysis. 相似文献
94.
A boundary layer analysis has been presented for the interaction of mixed convection with thermal radiation in laminar boundary flow from a vertical wedge in a porous medium saturated with a power-law type non-Newtonian incorporating the variation of permeability and thermal conductivity. The transformed conservation laws are solved numerically for the case of variable surface temperature conditions. The combined convection non-similar parameter we note that =0 and 1 correspond to pure free and forced convection cases. The Rosseland approximation is used to describe the radiative heat flux in energy equation. Velocity and temperature profiles as well as the local Nusselt number are presented. 相似文献
95.
A solute transport through a porous medium is examined provided that the fluid leaving the porous sample returns back in a continuous way. The porous medium is thus included into a closed hydrodynamic circuit. This cycling process is suggested as an experimental tool to determine porous medium parameters describing transport. In the present paper the mathematical theory of this method is developed. For the advective type of transport with solute retention and degradation in porous medium, the system of transport equations in a closed circuit is transformed to a delay differential equation. The exact analytical solution to this equation is obtained. The solute concentration manifests both the oscillatory and monotonous behaviors depending on system parameters. The number of oscillation splashes is shown to be always finite. The maximum/minimum points are determined as solutions of a polynomial equation whose degree depends on the unknown solution itself. The cyclic methods to determine porous medium parameters as porosity and retention rate are developed. 相似文献
96.
We use a mathematical technique, the self-similar functional renormalization, to construct formulas for the average conductivity
that apply for large heterogeneity, based on perturbative expansions in powers of a small parameter, usually the log-variance
of the local conductivity. Using perturbation expansions up to third order and fourth order in obtained from the moment equation approach, we construct the general functional dependence of the scalar hydraulic conductivity
in the regime where is of order 1 and larger than 1. Comparison with available numerical simulations show that the proposed method provides reasonable
improvements over available expansions. 相似文献
97.
98.
An approximate analytical solution is provided for one-dimensional, counter- current, spontaneous imbibition of a wetting
phase (water) into a semi-infinite porous medium. The solution is based on the assumption that a similarity solution exists
for the displacement process. This assumption, in turn, rests on the assumption that the set of relative permeability and
capillary pressures curves are unique functions of saturation and do not depend on the nature of the displacement. It further
rests on the assumption that the saturation at the imbibition face does not vary with time. It is demonstrated that the solution
is in agreement with results obtained from experiments and also numerical analyses of these experiments. The experiments utilize
cylindrical samples with the radial surface and one end-face sealed, and with counter-current imbibition occurring at the
open end-face. The stage of the experiment that is modeled by the present solution is the period before the imbibition front
contacts the sealed end-face. An important finding of the present analysis is that the pressure upstream of the advancing
invasion front is a constant. A second, improved solution is also presented; this solution is an iterative, series solution
of an integral-differential equation. It converges to a stable solution in very few terms. 相似文献
99.
Jodie N. Haigh Ya‐mi Chuang Brooke Farrugia Richard Hoogenboom Paul D. Dalton Tim R. Dargaville 《Macromolecular rapid communications》2016,37(1):93-99
A new method for fabricating hydrogels with intricate control over hierarchical 3D porosity using microfiber porogens is presented. Melt electrospinning writing of poly(ε‐caprolactone) is used to create the sacrificial template leading to hierarchical structuring consisting of pores inside the denser poly(2‐oxazoline) hydrogel mesh. This versatile approach provides new opportunities to create well‐defined multilevel control over interconnected pores with diameters in the lower micrometer range inside hydrogels with potential applications as cell scaffolds with tunable diffusion and transport of, e.g., nutrients, growth factors or therapeutics.
100.