全文获取类型
收费全文 | 467750篇 |
免费 | 5044篇 |
国内免费 | 1581篇 |
专业分类
化学 | 248258篇 |
晶体学 | 7042篇 |
力学 | 20420篇 |
综合类 | 11篇 |
数学 | 55568篇 |
物理学 | 143076篇 |
出版年
2021年 | 3150篇 |
2020年 | 3554篇 |
2019年 | 3751篇 |
2018年 | 4384篇 |
2017年 | 4205篇 |
2016年 | 7095篇 |
2015年 | 5095篇 |
2014年 | 7420篇 |
2013年 | 21101篇 |
2012年 | 16195篇 |
2011年 | 19954篇 |
2010年 | 12967篇 |
2009年 | 12901篇 |
2008年 | 18153篇 |
2007年 | 18525篇 |
2006年 | 17848篇 |
2005年 | 16065篇 |
2004年 | 14681篇 |
2003年 | 12986篇 |
2002年 | 12704篇 |
2001年 | 14353篇 |
2000年 | 11069篇 |
1999年 | 8757篇 |
1998年 | 7048篇 |
1997年 | 6955篇 |
1996年 | 6784篇 |
1995年 | 6215篇 |
1994年 | 5882篇 |
1993年 | 5673篇 |
1992年 | 6353篇 |
1991年 | 6211篇 |
1990年 | 5937篇 |
1989年 | 5613篇 |
1988年 | 5887篇 |
1987年 | 5637篇 |
1986年 | 5328篇 |
1985年 | 7511篇 |
1984年 | 7737篇 |
1983年 | 6294篇 |
1982年 | 6801篇 |
1981年 | 6778篇 |
1980年 | 6464篇 |
1979年 | 6596篇 |
1978年 | 6767篇 |
1977年 | 6758篇 |
1976年 | 6752篇 |
1975年 | 6477篇 |
1974年 | 6348篇 |
1973年 | 6562篇 |
1972年 | 3987篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
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
43.
44.
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
45.
46.
J. P. Levine 《Inventiones Mathematicae》1989,96(3):571-592
47.
J. H. Eberly 《Laser Physics》2006,16(6):921-926
We examine the application of Schmidt mode analysis to pure-state entanglement. Several examples permitting exact analytic calculation of Schmidt eigenvalues and eigenfunctions are included, as well as evaluation of the associated degree of entanglement. 相似文献
48.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
49.
The tape stripping technique is an experimental method frequently used for reconstruction of the in-depth distribution of various topically administered substances within the horny layer of human skin, e.g., compounds contained in sunscreens. Titanium dioxide (TiO2) nanoparticles (25–200 nm in diameter) are one such compound. Optical techniques which apply blue light are found to be suitable for reconstruction. However, the presence of particles affects the light propagation within the skin and therefore causes incorrect determination of strip thickness, leading to an improper reconstructed distribution of nanoparticle concentration revealed from the experimental data. This study evaluates the errors emerging from the use of blue (400 nm) and NIR (800 nm) radiation and finds the use of longer wavelength light more advantageous. Particles of different diameters are considered, and it is revealed that the application of small particles (25–60 nm) results in the lowest rate of error. 相似文献
50.
An algorithm is proposed which allows one to construct higher symmetries of arbitrary order for some special classes of hyperbolic
systems possessing integrals. The Pohlmeyer-Lund-Regge system and the open two-dimensional Toda lattices are shown to belong
to the class of systems where our algorithm is applicable.
__________
Translated from Fundamental’naya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 10, No. 1, Geometry
of Integrable Models, 2004. 相似文献