全文获取类型
收费全文 | 37376篇 |
免费 | 5931篇 |
国内免费 | 3939篇 |
专业分类
化学 | 26186篇 |
晶体学 | 360篇 |
力学 | 2231篇 |
综合类 | 242篇 |
数学 | 4286篇 |
物理学 | 13941篇 |
出版年
2024年 | 112篇 |
2023年 | 763篇 |
2022年 | 1236篇 |
2021年 | 1369篇 |
2020年 | 1456篇 |
2019年 | 1341篇 |
2018年 | 1160篇 |
2017年 | 1078篇 |
2016年 | 1628篇 |
2015年 | 1655篇 |
2014年 | 2040篇 |
2013年 | 2619篇 |
2012年 | 3312篇 |
2011年 | 3272篇 |
2010年 | 2237篇 |
2009年 | 2126篇 |
2008年 | 2272篇 |
2007年 | 2045篇 |
2006年 | 1912篇 |
2005年 | 1594篇 |
2004年 | 1350篇 |
2003年 | 1012篇 |
2002年 | 913篇 |
2001年 | 750篇 |
2000年 | 703篇 |
1999年 | 840篇 |
1998年 | 696篇 |
1997年 | 638篇 |
1996年 | 706篇 |
1995年 | 603篇 |
1994年 | 553篇 |
1993年 | 471篇 |
1992年 | 450篇 |
1991年 | 366篇 |
1990年 | 324篇 |
1989年 | 236篇 |
1988年 | 216篇 |
1987年 | 198篇 |
1986年 | 141篇 |
1985年 | 156篇 |
1984年 | 135篇 |
1983年 | 116篇 |
1982年 | 80篇 |
1981年 | 59篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 26篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
We prove that every noetherian affine PI Hopf algebra has finite injective dimension, which answers a question of Brown (1998).
62.
Under the nonresonant case where the carrier frequency of a Gaussian beam deviates from the resonant frequency of a Fabry–Perot etalon, the transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon has been investigated. The results show that under the nonresonant case, variations of the peak intensity, the position of the peak intensity and the spot size of the transmitted beam with the input angle behave differently and even with a reversed tendency compared with those obtained under the resonant case. 相似文献
63.
64.
65.
66.
In this paper, based on the natural boundary reduction advanced by Feng and Yu, we couple the finite element approach with the natural boundary element method to study the weak solvability and Galerkin approximation of a class of nonlinear exterior boundary value problems. The analysis is mainly based on the variational formulation with constraints. We prove the error estimate of the finite element solution and obtain the asymptotic rate of convergence. Finally, we also give a numerical example.
相似文献67.
We study the stationary measure for the two-dimensional Boussinesq equation with random forcing. We prove the ergodicity for the two-dimensional stochastically forced Boussinesq equation. We also study the Galerkin truncations of the three-dimensional Boussinesq equations under degenerate stochastic forcing. We follow closely the previous results on the stochastically forced Navier–Stokes equations. 相似文献
68.
We characterize functions in Morrey space by p-Carleson measures. We then reveal a simple relation between Q space and Morrey space, that is Q space can be viewed as a fractional integration of the Morrey space. Therefore, many results for Morrey space can be translated onto Q space. For example, we show that Q space is a dual space by identifying its predual. 相似文献
69.
In this paper, we present some counterexamples which show that there is no theory on the spectrum of homogeneous compact operators which parallels the Riesz-Schauder theory on the spectrum of linear compact operators. These counterexamples also illustrate that it is impossible to study in a unified setting the Fucik spectrum of the Laplacian: -△w = au+ - bu- inΩand u = 0 on (?)Ω, as well as the spectrum of the p-Laplacian: -div(|(?)u| p-2(?)u) = λ|u|p-2u and u = 0 on (?)Ω. 相似文献
70.
Optical characterization of bromo-alkoxyl-substituted copper phthalocyanine derivative thin films 总被引:2,自引:0,他引:2
A series of thin films of copper phthalocyanine derivatives with bromine and alkoxyl substituents [CuPc(OC8H17)4Brm, m=0,1,2,4] were prepared on single-crystal silicon substrates by spin coating. The ellipsometric spectra of the films have been studied on a rotating analyzer–polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in 500–800 nm wavelength region were obtained. The results show that the complex refractive index, dielectric constants and absorption coefficient of these thin films are influenced regularly by bromine substituent on conjugated macrocycle. It was found that there are approximately linear relationships between the resonance absorption wavelengths of the films and the average number of bromine atoms substituted on the phthalocyanine ring. 相似文献