全文获取类型
收费全文 | 384740篇 |
免费 | 3092篇 |
国内免费 | 1168篇 |
专业分类
化学 | 202922篇 |
晶体学 | 6022篇 |
力学 | 16598篇 |
综合类 | 9篇 |
数学 | 43990篇 |
物理学 | 119459篇 |
出版年
2021年 | 3080篇 |
2020年 | 3402篇 |
2019年 | 3847篇 |
2018年 | 5272篇 |
2017年 | 5103篇 |
2016年 | 7219篇 |
2015年 | 4301篇 |
2014年 | 6800篇 |
2013年 | 16980篇 |
2012年 | 12852篇 |
2011年 | 15552篇 |
2010年 | 11040篇 |
2009年 | 10847篇 |
2008年 | 14619篇 |
2007年 | 14796篇 |
2006年 | 13990篇 |
2005年 | 12557篇 |
2004年 | 11437篇 |
2003年 | 10276篇 |
2002年 | 10045篇 |
2001年 | 11185篇 |
2000年 | 8708篇 |
1999年 | 6638篇 |
1998年 | 5565篇 |
1997年 | 5597篇 |
1996年 | 5151篇 |
1995年 | 4578篇 |
1994年 | 4510篇 |
1993年 | 4418篇 |
1992年 | 4839篇 |
1991年 | 4942篇 |
1990年 | 4751篇 |
1989年 | 4574篇 |
1988年 | 4543篇 |
1987年 | 4489篇 |
1986年 | 4245篇 |
1985年 | 5580篇 |
1984年 | 5944篇 |
1983年 | 4804篇 |
1982年 | 5183篇 |
1981年 | 5050篇 |
1980年 | 4782篇 |
1979年 | 5032篇 |
1978年 | 5266篇 |
1977年 | 5266篇 |
1976年 | 5283篇 |
1975年 | 4955篇 |
1974年 | 4929篇 |
1973年 | 5199篇 |
1972年 | 3383篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
E. Lodi Rizzini 《La Rivista del Nuovo Cimento (1969-1970)》1992,15(8):1-29
The nucleon-antinucleon (NN) annihilation process provides a fertile testing ground for microscopic hadron exchange and/or quark models. TheNN system offers a rich ensemble of annihilation channels, whose relative BRs provide strong constraints on dynamical models.
Recent experiments show that values of BRs display a significant dependence onL, S andI. These dynamical selection rules,i.e. the suppression of transitions alloweda priori by conservation of quantum numbers, provide key signatures of the annihilation mechanism, and suggest dynamical content beyond
simple statistical or flavour symmetry models. 相似文献
232.
E. G. Ryabova 《Computational Mathematics and Modeling》1992,3(1):30-35
Translated from Vychislitel'nye Kompleksy i Modelirovanie Slozhnykh Sistem, pp. 98–106, Moscow State University, 1989. 相似文献
233.
I.L. Lyubchanskii N.N. Dadoenkova M.I. Lyubchanskii E.A. Shapovalov A.E. Zabolotin K.Y. Guslienko T. Rasing 《Applied physics. B, Lasers and optics》2002,74(7-8):711-714
Nonlinear (at the second-harmonic frequency of the incident light) optical reflection by two-dimensional magnetic superstructures
is theoretically studied. A square lattice of magnetic dots and a hexagonal lattice of magnetic bubbles (cylindrical magnetic
domains) are considered. Because the periods of these structures are comparable with the wavelengths of the fundamental and
the second-harmonic radiation, it would be possible to observe diffraction at the second-harmonic frequency. A polarization
analysis of nonlinearly diffracted radiation is performed and the numbers of observable diffraction orders for the above structures
are estimated.
Received: 10 January 2002 / Published online: 11 June 2002 相似文献
234.
235.
We investigate some issues of minimax estimation of spectral intensity of acoustic sources in cases when the noise and the spectral amplitudes satisfy quadratic constraints. Recursive minimax filters are obtained.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 58, pp. 116–119, 1986. 相似文献
236.
237.
D. D. Bainov S. I. Kostadinov P. P. Zabreiko 《International Journal of Theoretical Physics》1992,31(8):1521-1526
Necessary and sufficient conditions for the existence of an exponential dichotomy of impulsive differential equations in a Hilbert space are found. 相似文献
238.
D. G. Sannikov 《Physics of the Solid State》1997,39(7):1139-1142
A theoretical temperature-electric field phase diagram is constructed for thiourea SC(ND2)2 using a phenomenological approach based on the representation of the thermodynamic potentials for all phases. The theoretical
diagram is compared with the experimental diagram.
Fiz. Tverd. Tela (St. Petersburg) 39, 1282–1286 (July 1997) 相似文献
239.
A simple and precise high performance liquid chromatographic method for the determination of mexiletine in human serum or plasma is described. Following addition of N-propionylprocainamide as internal standard the specimens are extracted, under basic conditions, into methylene chloride. After removal of the aqueous layer the drug is back-extracted into dilute acid, which is then injected directly for analysis. The extraction efficiency is 79% for both mexiletine and internal standard, and the assay is linear to 4 mg/L (twice upper therapeutic concentration). Inter-run coefficients of variation are 3.0% or less. The relative retention time of mexiletine to internal standard averages 1.3. An adaptation of this method is described for an alternate application to the analysis of tocainide, procainamide and N-acetylprocainamide. 相似文献
240.
A new metastable liquid-crystalline phase BPS was observed in pure chiral compounds. The BPS is transformed reversibly from the supercooled BPI and is thermodynamically stable with respect to the BPI and metastable to the cholesteric phase. Rhombic single crystals of the BPS probably indicate a cubic lattice structure as in other BPs, but the lattice constant exhibits an anomalous temperature dependence. 相似文献