全文获取类型
收费全文 | 2996篇 |
免费 | 523篇 |
国内免费 | 498篇 |
专业分类
化学 | 1927篇 |
晶体学 | 62篇 |
力学 | 936篇 |
综合类 | 21篇 |
数学 | 313篇 |
物理学 | 758篇 |
出版年
2024年 | 8篇 |
2023年 | 48篇 |
2022年 | 80篇 |
2021年 | 127篇 |
2020年 | 192篇 |
2019年 | 142篇 |
2018年 | 150篇 |
2017年 | 117篇 |
2016年 | 182篇 |
2015年 | 148篇 |
2014年 | 161篇 |
2013年 | 233篇 |
2012年 | 170篇 |
2011年 | 160篇 |
2010年 | 151篇 |
2009年 | 151篇 |
2008年 | 148篇 |
2007年 | 164篇 |
2006年 | 186篇 |
2005年 | 166篇 |
2004年 | 147篇 |
2003年 | 168篇 |
2002年 | 116篇 |
2001年 | 77篇 |
2000年 | 88篇 |
1999年 | 74篇 |
1998年 | 58篇 |
1997年 | 68篇 |
1996年 | 51篇 |
1995年 | 41篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 20篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 3篇 |
排序方式: 共有4017条查询结果,搜索用时 15 毫秒
11.
A. Bourgeat O. Gipouloux E. Marui‐Paloka 《Mathematical Methods in the Applied Sciences》2004,27(4):381-403
In this paper, we study the global behaviour of an underground waste disposal in order to have an accurate upscaled model suitable for the computations involved in safety assessment processes. We start from a detailed model describing the transport of pollutant leaking from a high number of units. Using the method of homogenization, going to the limit, we obtain first a macroscopic model where the sources are now appearing globally. Then we compute a first‐order matched asymptotic expansion and we give the error estimates for this approximation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
M. A. Efendiev J. Fuhrmann S. V. Zelik 《Mathematical Methods in the Applied Sciences》2004,27(8):907-930
For the Boussinesq approximation of the equations of coupled heat and fluid flow in a porous medium we show that the corresponding system of partial differential equations possesses a global attractor. We give lower and upper bounds of the Hausdorff dimension of the attractor depending on a physical parameter of the system, namely the Rayleigh number of the flow. Numerical experiments confirm the theoretical findings and raise new questions on the structure of the solutions of the system. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
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
14.
Luminescence properties of anodic aluminum oxide films with organic luminophores embedded into pores
V. V. Gruzinskii A. V. Kukhto A. M. Mozalev V. F. Surganov 《Journal of Applied Spectroscopy》1997,64(4):497-502
Luminescence properties of porous anodic aluminum oxide films formed in a 0.6 M solution of citric acid and luminescence of
paraterphenyl, perylene, coumarin 7, and rhodamine 6G dyes adsorbed by the films are investigated. The nature of emitting
centers in anodic aluminum oxide is revealed. Intense photoluminescence of all tested dyes embedded into pores of anodic aluminum
oxide has been found. A redshift of fluorescence spectra of dyes adsorbed by the matrix and emergence of an additional longwave
band have been detected. Data obtained can be used in developing new thin-film luminescent coatings for future applications
in optoelectronics and molecular electronics.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No 4, pp. 483–488, July–August, 1997. 相似文献
15.
对经过阴极还原处理后的多孔硅样片进行了光致发光测试和稳定性测试.实验结果表明这种处理能明显改善多孔硅的发光稳定性,使其表面结构更加稳定.利用原子力显微镜对不同还原时间的多孔硅微结构及形貌进行了比较,在一定范围内随着还原时间的增长多孔硅表面粗糙度增大,PL谱增强. 相似文献
16.
The aim of this paper is to introduce a new functional in thestudy of swelling porous elastic soils saturated by a fluid.This new functional is a useful tool; it allows us to provethe existence of solutions in the case of a compressible fluid.We also prove the stability of solutions and the exponentialdecay in the case of an incompressible fluid. We study as wellthe continuous dependence with respect to the initial time. 相似文献
17.
A. V. Pastukhov V. A. Davankov E. V. Sidorova E. I. Shkol’nikov V. V. Volkov 《Russian Chemical Bulletin》2007,56(3):484-493
An automated procedure was developed for monitoring fast changes in the size of spherical samples of polymers during their
contact with a solvent or drying. The kinetics of bulk deformation in these processes was studied for a series of cross-linked
polymers, viz., gel-type and porous styrene—divinylbenzene copolymers and poly(divinylbenzenes), and hypercrosslinked polystyrenes. Gel,
macroporous, and hypercrosslinked polystyrenes are substantially different in the rate, mechanism, and degree of swelling,
which is associated with the principal differences in their physical structures. An unusual effect of a sharp decrease followed
by a temporary increase in the volume of porous polystyrene and poly(divinylbenzene) materials were observed during desorption
(evaporation) of organic solvents. Water desorption is accompanied by an excessive bulk compression of porous granules giving
rise to negative deformations, which gradually relax to the state equilibrium for the dry polymer. The results of dynamic
desorption porometry (for water desorption) are indicative of a bimodal size distribution of micropores in hypercrosslinked
polystyrene.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 467–476, March, 2007. 相似文献
18.
19.
20.