全文获取类型
收费全文 | 1279篇 |
免费 | 44篇 |
国内免费 | 6篇 |
专业分类
化学 | 917篇 |
晶体学 | 5篇 |
力学 | 25篇 |
数学 | 202篇 |
物理学 | 180篇 |
出版年
2023年 | 9篇 |
2022年 | 27篇 |
2021年 | 34篇 |
2020年 | 29篇 |
2019年 | 22篇 |
2018年 | 32篇 |
2017年 | 20篇 |
2016年 | 48篇 |
2015年 | 28篇 |
2014年 | 40篇 |
2013年 | 71篇 |
2012年 | 57篇 |
2011年 | 67篇 |
2010年 | 43篇 |
2009年 | 37篇 |
2008年 | 64篇 |
2007年 | 48篇 |
2006年 | 42篇 |
2005年 | 41篇 |
2004年 | 35篇 |
2003年 | 42篇 |
2002年 | 34篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1987年 | 8篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1981年 | 11篇 |
1979年 | 8篇 |
1976年 | 7篇 |
1972年 | 6篇 |
1918年 | 8篇 |
1907年 | 6篇 |
1905年 | 6篇 |
1901年 | 11篇 |
1895年 | 6篇 |
1894年 | 6篇 |
1888年 | 6篇 |
1885年 | 9篇 |
排序方式: 共有1329条查询结果,搜索用时 15 毫秒
81.
In this paper we study the existence and the stability of bounded solutions of the following non-linear system of parabolic equations with homogeneous Dirichlet boundary conditions:
82.
Hugo A. Morales-Técotl Omar Pedraza Luis O. Pimentel 《General Relativity and Gravitation》2007,39(8):1185-1202
Testing extra dimensions at low-energies may lead to interesting effects. In this work a test point charge is taken to move
uniformly in the 3D subspace of a (3 + n)-brane embedded in a (3 + n + 1)-space with n compact and one warped infinite spatial extra dimensions. We found that the electromagnetic potentials of the point charge
match standard Liennard–Wiechert’s at large distances but differ from them close to it. These are finite at the position of
the charge and produce finite self-energies. We also studied a localized Hydrogen atom and take the deviation from the standard
Coulomb potential as a perturbation. This produces a Lamb shift that is compared with known experimental data to set bounds
for the parameter of the model. This work provides details and extends results reported in a previous Letter.
We are pleased to dedicate this work to Professor Octavio Obregón on occasion of his 60th birthday. H. A. Morales-Técotl is
an associate member of the Abdus Salam ICTP, Trieste Italy. 相似文献
83.
Considerable advances in automatic speech recognition have been made in the last decades, thanks specially to the use of hidden Markov models. In the field of speech signal analysis, different techniques have been developed. However, deterioration in the performance of the speech recognizers has been observed when they are trained with clean signal and tested with noisy signals. This is still an open problem in this field. Continuous multiresolution entropy has been shown to be robust to additive noise in applications to different physiological signals. In previous works we have included Shannon and Tsallis entropies, and their corresponding divergences, in different speech analysis and recognition systems. In this paper we present an extension of the continuous multiresolution entropy to different divergences and we propose them as new dimensions for the pre-processing stage of a speech recognition system. This approach takes into account information about changes in the dynamics of speech signal at different scales. The methods proposed here are tested with speech signals corrupted with babble and white noise. Their performance is compared with classical mel cepstral parametrization. The results suggest that these continuous multiresolution entropy related measures provide valuable information to the speech recognition system and that they could be considered to be included as an extra component in the pre-processing stage. 相似文献
84.
Ed. Hirschsohn M. Perrot P. W. Squire Bouchardat Tardy Schimmel & Co. Wallach Pond Helbing Passmore Kremers Schreiner und Hugo Andres 《Fresenius' Journal of Analytical Chemistry》1898,37(6):401-408
Ohne Zusammenfassung 相似文献
85.
86.
Ohne Zusammenfassung 相似文献
87.
Hugo Parlier 《Israel Journal of Mathematics》2008,166(1):297-311
In this paper, involutions without fixed points on hyperbolic closed Riemann surface are discussed. For an orientable surface
X of even genus with an arbitrary Riemannian metric d admitting an involution τ, it is known that min
p∈X
d(p, τ(p)) is bounded by a constant which depends on the area of X. The corresponding claim is proved to be false in odd genus, and the optimal constant for hyperbolic Riemann surfaces is
calculated in genus 2.
The author was supported in part by the Swiss National Science Foundation grants 20-68181.02 and PBEL2-106180. 相似文献
88.
Wilhelm Blödorn Robert Krismer Hugo M. Ortner Jens Stummeyer Peter Wilhartitz Gerold Wünsch 《Mikrochimica acta》1989,99(3-6):423-432
Trace metals (20 elements) in high-purity chromium, molybdenum and tungsten are collected and preconcentrated by precipitation and adsorption on cellulose collectors. The compound methods allow the application of AAS and ICP-AES as determination methods for the production control of highly pure refractory metals under routine conditions.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
89.
Hugo Ditz 《Fresenius' Journal of Analytical Chemistry》1905,44(10):642
Ohne Zusammenfassung 相似文献
90.
Hugo Schrötter 《Monatshefte für Chemie / Chemical Monthly》1896,17(1):199-205
Ohne Zusammenfassung 相似文献