全文获取类型
收费全文 | 28420篇 |
免费 | 695篇 |
国内免费 | 230篇 |
专业分类
化学 | 19294篇 |
晶体学 | 128篇 |
力学 | 648篇 |
综合类 | 1篇 |
数学 | 5385篇 |
物理学 | 3889篇 |
出版年
2022年 | 183篇 |
2021年 | 276篇 |
2020年 | 347篇 |
2019年 | 314篇 |
2018年 | 276篇 |
2017年 | 292篇 |
2016年 | 600篇 |
2015年 | 626篇 |
2014年 | 659篇 |
2013年 | 1406篇 |
2012年 | 1407篇 |
2011年 | 1706篇 |
2010年 | 952篇 |
2009年 | 815篇 |
2008年 | 1465篇 |
2007年 | 1467篇 |
2006年 | 1553篇 |
2005年 | 1394篇 |
2004年 | 1327篇 |
2003年 | 1100篇 |
2002年 | 1046篇 |
2001年 | 453篇 |
2000年 | 407篇 |
1999年 | 395篇 |
1998年 | 385篇 |
1997年 | 432篇 |
1996年 | 398篇 |
1995年 | 360篇 |
1994年 | 391篇 |
1993年 | 344篇 |
1992年 | 320篇 |
1991年 | 320篇 |
1990年 | 278篇 |
1989年 | 280篇 |
1988年 | 260篇 |
1987年 | 218篇 |
1986年 | 245篇 |
1985年 | 361篇 |
1984年 | 370篇 |
1983年 | 315篇 |
1982年 | 348篇 |
1981年 | 316篇 |
1980年 | 338篇 |
1979年 | 270篇 |
1978年 | 300篇 |
1977年 | 280篇 |
1976年 | 223篇 |
1975年 | 190篇 |
1974年 | 195篇 |
1973年 | 165篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
A new parallel storm surge model, the Parallel Environmental Model (PEM), is developed and tested by comparisons with analytic solutions. The PEM is a 2‐D vertically averaged, wetting and drying numerical model and can be operated in explicit, semi‐implicit and fully implicit modes. In the implicit mode, the propagation, Coriolis and bottom friction terms can all be treated implicitly. The advection and diffusion terms are solved with a parallel Eulerian–Lagrangian scheme developed for this study. The model is developed specifically for use on parallel computer systems and will function accordingly in either explicit of implicit modes. Storm boundary conditions are based on a simple exponential decay of pressure from the centre of a storm. The simulated flooding caused by a major Category 5 hurricane making landfall in the Indian River Lagoon, Florida is then presented as an example application of the PEM. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
22.
Peter G. Casazza Gitta Kutyniok Mark C. Lammers 《Journal of Fourier Analysis and Applications》2004,10(4):383-408
Duality principles in Gabor theory such as the Ron–Shen duality principle and the
Wexler–Raz biorthogonality relations play a fundamental role for analyzing Gabor systems. In this
article we present a general approach to derive duality principles in abstract frame theory. For
each sequence in a separable Hilbert space we define a corresponding sequence dependent only
on two orthonormal bases. Then we characterize exactly properties of the first sequence in terms
of the associated one, which yields duality relations for the abstract frame setting. In the last part
we apply our results to Gabor systems. 相似文献
23.
Deformation quantization is a powerful tool for quantizing theories with bosonic and fermionic degrees of freedom. The star products involved generate the mathematical structures which have recently been used in attempts to analyze the algebraic properties of quantum field theory. In the context of quantum mechanics they provide a quantization procedure for systems with either bosonic or fermionic degrees of freedom. We illustrate this procedure for a number of physical examples, including bosonic, fermionic, and supersymmetric oscillators. We show how non-relativistic and relativistic particles with spin can be naturally described in this framework. 相似文献
24.
Andrzej Dabrowski Erich Robens Peter Klobes Klaus Meyer Przemyslaw Podkocielny 《Particle & Particle Systems Characterization》2003,20(5):311-322
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals. 相似文献
25.
26.
We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11] and considered also by Steadman [13], and show that coordinate time runs backward along a portion of these geodesics. 相似文献
27.
28.
Design theory crosses the boundary between mathematics and statistics, and includes a wide range of disparate types of design. In this paper we present a classification scheme which aims to include as many important types as possible, based on a balance among concept, representation and use. 相似文献
29.
Manfred Brun Peter Hubner Dieter Oelkrug 《Fresenius' Journal of Analytical Chemistry》1992,344(4-5):209-213
Summary A theoretical model is derived that describes the influence of lateral light diffusion in a scattering medium on the absorptivity of an absorber spot on top of the substrate. The model uses the lateral resolved reflectivity under point irradiation that has been analyzed experimentally with a scanning-micro-laser-reflectometer. The model allows quantification of the absorptivity by one single equation that contains only the mean radial diffusion length of light and the spot area. Experiment and theory are applied to typical substrates for thin layer chromatography (alumina, silica, cellulose). The diffusion lengths in these substrates are given and the absorptivities of the spots are calculated as a function of the spot area. 相似文献
30.