全文获取类型
收费全文 | 234733篇 |
免费 | 3601篇 |
国内免费 | 830篇 |
专业分类
化学 | 129409篇 |
晶体学 | 2805篇 |
力学 | 8989篇 |
综合类 | 17篇 |
数学 | 29577篇 |
物理学 | 68367篇 |
出版年
2022年 | 1443篇 |
2021年 | 1847篇 |
2020年 | 2077篇 |
2019年 | 1988篇 |
2018年 | 2373篇 |
2017年 | 2310篇 |
2016年 | 4412篇 |
2015年 | 3659篇 |
2014年 | 4259篇 |
2013年 | 11323篇 |
2012年 | 9905篇 |
2011年 | 11531篇 |
2010年 | 7201篇 |
2009年 | 7094篇 |
2008年 | 10399篇 |
2007年 | 10180篇 |
2006年 | 9656篇 |
2005年 | 9600篇 |
2004年 | 8686篇 |
2003年 | 7244篇 |
2002年 | 6660篇 |
2001年 | 7232篇 |
2000年 | 5804篇 |
1999年 | 4301篇 |
1998年 | 3295篇 |
1997年 | 3249篇 |
1996年 | 3401篇 |
1995年 | 2908篇 |
1994年 | 2886篇 |
1993年 | 2748篇 |
1992年 | 3073篇 |
1991年 | 2888篇 |
1990年 | 2595篇 |
1989年 | 2519篇 |
1988年 | 2514篇 |
1987年 | 2404篇 |
1986年 | 2304篇 |
1985年 | 3347篇 |
1984年 | 3301篇 |
1983年 | 2657篇 |
1982年 | 2856篇 |
1981年 | 2747篇 |
1980年 | 2635篇 |
1979年 | 2568篇 |
1978年 | 2646篇 |
1977年 | 2572篇 |
1976年 | 2506篇 |
1975年 | 2444篇 |
1974年 | 2392篇 |
1973年 | 2470篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
C. Kimberling 《Aequationes Mathematicae》2002,63(1-2):158-167
32.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
33.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
34.
In the following we find all of the three-dimensional flat spacetimes which are static and rotationally symmetric. 相似文献
35.
36.
A method using third order moments for estimating the regression coefficients as well as the latent state scores of the reduced-rank regression model when the latent variable(s) are non-normally distributed is presented in this paper. It is shown that the factor analysis type indeterminacy of the regression coefficient matrices is eliminated. A real life example of the proposed method is presented. Differences of this solution with the reduced-rank regression eigen solution are discussed. 相似文献
37.
38.
Using Wagner's polarization technique and EMF method the joinic and silver ionic transport number measurements of various
compositions of the mixed system CdI2-Ag2O-CrO3 have been made. The presence of AgI in these materials has been inferred from the typical β → α phase transition of AgI,
which is characterized by an endothermic peak at around 420 K in the DSC traces of these specimens. While the structural analysis
performed by means of powder X-ray diffraction has revealed the formation of ionic phases involving polycrystalline compounds,
the Fourier transform infrared (FTIR) spectroscopic results have indicated the presence of ionic species thus confirming the
ionic nature of the products. The complex impedance studies carried out in the frequency range 20 Hz - 1 MHz and over the
temperature range 294 – 442 K have revealed that the best conducting composition, namely 55%(CdI2) – 45%(Ag2O·CrO3), would exhibit a silver ionic conductivity of 1.3×10−5Scm−1 at 294 K. 相似文献
39.
de Souza P. A. Garg V. K. Klingelhöfer G. Gellert R. Gütlich P. 《Hyperfine Interactions》2002,139(1-4):705-714
A portable Mössbauer spectrometer, developed for extraterrestrial applications, opens up new industrial applications of MBS. But for industrial applications, an available tool for fast data analysis is also required, and it should be easy to handle. The analysis of Mössbauer spectra and their parameters is a barrier for the popularity of this wide-applicable spectroscopic technique in industry. Based on experience, the analysis of a Mössbauer spectrum is time-consuming and requires the dedication of a specialist. However, the analysis of Mössbauer spectra, from the fitting to the identification of the sample phases, can be faster using by genetic algorithms, fuzzy logic and artificial neural networks. Industrial applications are very specific ones and the data analysis can be performed using these algorithms. In combination with an automatic analysis, the Mössbauer spectrometer can be used as a probe instrument which covers the main industrial needs for an on-line monitoring of its products, processes and case studies. Some of these real industrial applications will be discussed. 相似文献
40.
A. I. Magunov A. Ya. Faenov I. Yu. Skobelev T. A. Pikuz E. Biémont P. Quinet F. Blasco C. Bonte F. Dorchies T. Caillaud F. Salin C. Stenz 《Journal of Experimental and Theoretical Physics》2002,95(6):998-1005
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. 相似文献