全文获取类型
收费全文 | 3064篇 |
免费 | 352篇 |
国内免费 | 191篇 |
专业分类
化学 | 696篇 |
晶体学 | 7篇 |
力学 | 543篇 |
综合类 | 42篇 |
数学 | 1111篇 |
物理学 | 1208篇 |
出版年
2024年 | 3篇 |
2023年 | 42篇 |
2022年 | 86篇 |
2021年 | 81篇 |
2020年 | 108篇 |
2019年 | 81篇 |
2018年 | 92篇 |
2017年 | 110篇 |
2016年 | 111篇 |
2015年 | 72篇 |
2014年 | 152篇 |
2013年 | 189篇 |
2012年 | 155篇 |
2011年 | 162篇 |
2010年 | 170篇 |
2009年 | 186篇 |
2008年 | 210篇 |
2007年 | 182篇 |
2006年 | 166篇 |
2005年 | 210篇 |
2004年 | 159篇 |
2003年 | 148篇 |
2002年 | 109篇 |
2001年 | 90篇 |
2000年 | 61篇 |
1999年 | 62篇 |
1998年 | 52篇 |
1997年 | 48篇 |
1996年 | 40篇 |
1995年 | 32篇 |
1994年 | 33篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有3607条查询结果,搜索用时 15 毫秒
1.
2.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
3.
Guy Bayada 《Journal of Mathematical Analysis and Applications》2003,282(1):212-231
The asymptotic behaviour of a Stokes flow with Tresca free boundary friction conditions when one dimension of the fluid domain tends to zero is studied. A specific Reynolds equation associated with variational inequalities is obtained and uniqueness is proved. 相似文献
4.
5.
A. A. Dokukin 《Computational Mathematics and Mathematical Physics》2006,46(5):914-918
To validate approximate optimization schemes for estimate calculation algorithms (ECAs), it is necessary to compute the optimal height, which cannot be done in a reasonable amount of time. A variety of samples are built for which the optimal height of the ECAs is known by construction. 相似文献
6.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献
7.
Thomas Wanner 《Transactions of the American Mathematical Society》2004,356(6):2251-2279
Many interesting and complicated patterns in the applied sciences are formed through transient pattern formation processes. In this paper we concentrate on the phenomenon of spinodal decomposition in metal alloys as described by the Cahn-Hilliard equation. This model depends on a small parameter, and one is generally interested in establishing sharp lower bounds on the amplitudes of the patterns as the parameter approaches zero. Recent results on spinodal decomposition have produced such lower bounds. Unfortunately, for higher-dimensional base domains these bounds are orders of magnitude smaller than what one would expect from simulations and experiments. The bounds exhibit a dependence on the dimension of the domain, which from a theoretical point of view seemed unavoidable, but which could not be observed in practice.
In this paper we resolve this apparent paradox. By employing probabilistic methods, we can improve the lower bounds for certain domains and remove the dimension dependence. We thereby obtain optimal results which close the gap between analytical methods and numerical observations, and provide more insight into the nature of the decomposition process. We also indicate how our results can be adapted to other situations.
8.
M.B. Xu 《Applied Acoustics》2003,64(7):731-752
The forced vibration of an infinite elastic circular cylindrical shell filled with fluid is studied. Three methods are employed to analyze the forced vibration problem of this shell-fluid coupled system, that is, wave propagation approach (wave mode superposition), theorem of residues and a numerical integral method. In order to explain these methods more explicitly, before being used to investigate the vibration of an infinite fluid-filled elastic circular cylindrical shell, all these three methods are employed firstly to analyze the forced vibration problem of an infinite beam and an infinite elastic circular cylindrical shell in vacuo. Advantage and disadvantage of these three methods are discussed and their interesting relationship is revealed. That is, to any circumferential wavenumber and frequency of the external force, there is an unchangeable relationship between the general coordinates of various waves in the wave propagation approach and the residuals in the theorem of residues. 相似文献
9.
10.
Two structure functions W1(x,Q2) and W2(x,Q2) are determined by using the cross sections measured in the deep inelastic electron-proton scattering experiments at Stanford Linac in the energy range of 5 to 20 GeV. In this paper an alternative mathematical approach have been used in such determination, resulting in a larger number of points in the graphs of the structure functions. 相似文献