全文获取类型
收费全文 | 263960篇 |
免费 | 2805篇 |
国内免费 | 893篇 |
专业分类
化学 | 124114篇 |
晶体学 | 2971篇 |
力学 | 14202篇 |
综合类 | 12篇 |
数学 | 52739篇 |
物理学 | 73620篇 |
出版年
2020年 | 1601篇 |
2019年 | 1574篇 |
2018年 | 12072篇 |
2017年 | 11843篇 |
2016年 | 9334篇 |
2015年 | 3141篇 |
2014年 | 3610篇 |
2013年 | 8535篇 |
2012年 | 10198篇 |
2011年 | 18018篇 |
2010年 | 10881篇 |
2009年 | 11082篇 |
2008年 | 13613篇 |
2007年 | 15709篇 |
2006年 | 7090篇 |
2005年 | 7551篇 |
2004年 | 7036篇 |
2003年 | 6671篇 |
2002年 | 5649篇 |
2001年 | 5306篇 |
2000年 | 4208篇 |
1999年 | 3159篇 |
1998年 | 2808篇 |
1997年 | 2717篇 |
1996年 | 2643篇 |
1995年 | 2455篇 |
1994年 | 2436篇 |
1993年 | 2299篇 |
1992年 | 2572篇 |
1991年 | 2512篇 |
1990年 | 2323篇 |
1989年 | 2298篇 |
1988年 | 2219篇 |
1987年 | 2136篇 |
1986年 | 2036篇 |
1985年 | 2699篇 |
1984年 | 2789篇 |
1983年 | 2316篇 |
1982年 | 2497篇 |
1981年 | 2374篇 |
1980年 | 2329篇 |
1979年 | 2455篇 |
1978年 | 2589篇 |
1977年 | 2454篇 |
1976年 | 2451篇 |
1975年 | 2362篇 |
1974年 | 2398篇 |
1973年 | 2347篇 |
1972年 | 1517篇 |
1971年 | 1382篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
R. F. Bikbaev 《Theoretical and Mathematical Physics》1989,80(3):1004-1006
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989. 相似文献
12.
Transport as a consequence of state-dependent diffusion 总被引:1,自引:0,他引:1
M. Büttiker 《Zeitschrift für Physik B Condensed Matter》1987,68(2-3):161-167
Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
13.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed. 相似文献
14.
Data Envelopment Analysis (DEA) offers a piece-wise linear approximation of the production frontier. The approximation tends to be poor if the true frontier is not concave, eg in case of economies of scale or of specialisation. To improve the flexibility of the DEA frontier and to gain in empirical fit, we propose to extend DEA towards a more general piece-wise quadratic approximation, called Quadratic Data Envelopment Analysis (QDEA). We show that QDEA gives statistically consistent estimates for all production frontiers with bounded Hessian eigenvalues. Our Monte-Carlo simulations suggest that QDEA can substantially improve efficiency estimation in finite samples relative to standard DEA models. 相似文献
15.
A.-S. F. Obada M. Darwish H. H. Salah 《International Journal of Theoretical Physics》2002,41(9):1755-1768
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined. 相似文献
16.
17.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
18.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed. 相似文献
19.
The finite-size corrections, central chargesc, and scaling dimensionsx of tricritical hard squares and critical hard hexagons are calculated analytically. This is achieved by solving the special functional equation or inversion identity satisfied by the commuting row transfer matrices of these lattice models at criticality. The results are expressed in terms of Rogers dilogarithms. For tricritical hard squares we obtainc=7/10,x=3/40, 1/5, 7/8, 6/5 and for hard hexagons we obtainc=4/5,x=2/15, 4/5, 17/15, 4/3, 9/5, in accord with the predictions of conformal and modular invariance. 相似文献
20.