全文获取类型
收费全文 | 318292篇 |
免费 | 3911篇 |
国内免费 | 1116篇 |
专业分类
化学 | 173564篇 |
晶体学 | 4475篇 |
力学 | 13121篇 |
综合类 | 7篇 |
数学 | 36762篇 |
物理学 | 95390篇 |
出版年
2020年 | 2061篇 |
2019年 | 2057篇 |
2018年 | 2053篇 |
2017年 | 1954篇 |
2016年 | 4028篇 |
2015年 | 3356篇 |
2014年 | 4544篇 |
2013年 | 14190篇 |
2012年 | 11070篇 |
2011年 | 13747篇 |
2010年 | 8456篇 |
2009年 | 8394篇 |
2008年 | 12617篇 |
2007年 | 12864篇 |
2006年 | 12505篇 |
2005年 | 11410篇 |
2004年 | 10236篇 |
2003年 | 9005篇 |
2002年 | 8835篇 |
2001年 | 10144篇 |
2000年 | 7732篇 |
1999年 | 6133篇 |
1998年 | 4908篇 |
1997年 | 4754篇 |
1996年 | 4792篇 |
1995年 | 4381篇 |
1994年 | 4128篇 |
1993年 | 3954篇 |
1992年 | 4443篇 |
1991年 | 4302篇 |
1990年 | 4020篇 |
1989年 | 3839篇 |
1988年 | 4130篇 |
1987年 | 3793篇 |
1986年 | 3685篇 |
1985年 | 5329篇 |
1984年 | 5404篇 |
1983年 | 4384篇 |
1982年 | 4760篇 |
1981年 | 4799篇 |
1980年 | 4549篇 |
1979年 | 4668篇 |
1978年 | 4668篇 |
1977年 | 4653篇 |
1976年 | 4601篇 |
1975年 | 4511篇 |
1974年 | 4357篇 |
1973年 | 4528篇 |
1972年 | 2572篇 |
1971年 | 1885篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献
12.
The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques. 相似文献
13.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
14.
The Wheeler–DeWitt equation of arbitrary Hartle–Hawking factor ordering for several minisuperspace universe models, such as the pure gravity Friedmann–Robertson–Walker and Taub ones, is mapped onto the dynamics of corresponding classical oscillators. The latter ones are studied by the classical Ermakov invariant method, which is a natural approach in this context. For the more realistic case of a minimally coupled massive scalar field, one can study, within the same type of approach, the corresponding squeezing features as a possible means of describing cosmological evolution. Finally, we comment on the analogy with the accelerator physics. 相似文献
15.
R. J. Hinde 《Few-Body Systems》2006,38(2-4):187-191
We compute the vibrational coupling between two H2 molecules from ab initio quantum chemical calculations of the H2-H2 potential carried out at the full configuration interaction level of theory using the atom-centered aug-cc-pVTZ basis set
for hydrogen. We compare the full configuration interaction results with those obtained using two variants of coupled cluster
theory and find that a fully iterative treatment of connected triples may be required to estimate the H2-H2 vibrational coupling accurately using coupled cluster theory. 相似文献
16.
J. M. Rubi 《Journal of statistical physics》2006,123(2):497-498
17.
In this paper we study root system generalizations of the quantum Bose-gas on the circle with pair-wise delta-function interactions.
The underlying symmetry structures are shown to be governed by the associated graded algebra of Cherednik's (suitably filtered)
degenerate double affine Hecke algebra, acting by Dunkl-type differential-reflection operators. We use Gutkin's generalization
of the equivalence between the impenetrable Bose-gas and the free Fermi-gas to derive the Bethe ansatz equations and the Bethe
ansatz eigenfunctions. 相似文献
18.
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
19.
20.
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