全文获取类型
收费全文 | 267892篇 |
免费 | 2051篇 |
国内免费 | 623篇 |
专业分类
化学 | 142046篇 |
晶体学 | 4162篇 |
力学 | 11930篇 |
综合类 | 9篇 |
数学 | 29521篇 |
物理学 | 82898篇 |
出版年
2019年 | 2293篇 |
2018年 | 3117篇 |
2017年 | 3112篇 |
2016年 | 4486篇 |
2015年 | 2657篇 |
2014年 | 4280篇 |
2013年 | 10680篇 |
2012年 | 8072篇 |
2011年 | 9900篇 |
2010年 | 7085篇 |
2009年 | 6878篇 |
2008年 | 9315篇 |
2007年 | 9512篇 |
2006年 | 8882篇 |
2005年 | 8072篇 |
2004年 | 7422篇 |
2003年 | 6734篇 |
2002年 | 6660篇 |
2001年 | 7327篇 |
2000年 | 5661篇 |
1999年 | 4359篇 |
1998年 | 3859篇 |
1997年 | 3844篇 |
1996年 | 3586篇 |
1995年 | 3332篇 |
1994年 | 3492篇 |
1993年 | 3190篇 |
1992年 | 3663篇 |
1991年 | 3668篇 |
1990年 | 3599篇 |
1989年 | 3458篇 |
1988年 | 3568篇 |
1987年 | 3466篇 |
1986年 | 3287篇 |
1985年 | 4363篇 |
1984年 | 4632篇 |
1983年 | 3873篇 |
1982年 | 4010篇 |
1981年 | 3934篇 |
1980年 | 3910篇 |
1979年 | 3877篇 |
1978年 | 4191篇 |
1977年 | 4109篇 |
1976年 | 4173篇 |
1975年 | 3850篇 |
1974年 | 3897篇 |
1973年 | 4053篇 |
1972年 | 2852篇 |
1971年 | 2379篇 |
1970年 | 2177篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
G. P. Gurinovich 《Journal of Applied Spectroscopy》1991,54(3):243-249
152.
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
153.
154.
155.
A cluster mechanism is considered for the detachment of particles when the surface of a high-temperature superconducting target
absorbs laser pulses. By proposing a fractal nature for the surface, one can model it as an assembly of a large number of
nonlinear oscillators (clusters). Utilizing the method of sudden perturbations, a calculation was made of the probability
of dissociation of these oscillators, i.e., of the detachment of clusters from the surface. The calculated probability decreases
rapidly as the power density of the laser radiation is reduced to some limiting value. This is in agreement with experiments.
State Institute of Sensory Microelectronics. Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya
Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 73–77, June, 1997. 相似文献
156.
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
157.
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
158.
A. Jarid M. Aaid Y. Legoux J. Merini M. Loudet D. Gonbeau G. Pfister-Guillouzo 《Chemical physics》1991,150(3):353-360
The electronic and structural characteristics of CrF5, CrF4, RuF5 and RuF4 were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF5 in D3h, triplet for CrF4 in Td, quadruplet for RuF5 in C4v and quintuplet for RuF4 in D4h symmetry. 相似文献
159.
A two-dimensional self consistent model of the Beam-Plasma-Discharge (BPD) has been developed to calculate the discharge ignition of a bandlike electron beam in a discharge chamber. The discharge was considered in Argon with an initial concentration of 1014 cm?3. The model allows calculation of the time evolution of perpendicular profiles of electron density, temperature and the potential. 相似文献
160.
S. G. Charati A. Y. Houde S. S. Kulkarni M. G. Kulkarni 《Journal of Polymer Science.Polymer Physics》1991,29(8):921-931
Polymer packing density can be conveniently measured by either density-based measurements (direct or estimated free volume) or wide-angle X-ray diffraction (WAXD) spectra. Previously reported diffusivity and permeability values for various polyarylates and polyimides are examined on the basis of the packing density measured by these different techniques. It is shown that in these rigid glassy polymers, the mean intersegmental distance, the d-spacing, obtained from WAXD provides a better measure of the effect of polymer packing on diffusivity than either direct density measurements or estimated free volumes. It has been possible to correlate previously reported diffusivity and sorption data for various polyarylates and polycarbonate on the basis of the WAXD investigation, using the d-spacing and the amorphous peak width, respectively. The effect of polyarylate structure on d-spacing has been studied. A series of polyarylates have been synthesized with different substituents on the bridge carbon. In this series the d-spacing remains constant while the carbonyl group density and the glass transition temperatures are varied. However, small substituents on the aromatic ring cause significant changes in the d-spacing. These results can be used to tailor polyarylates with desired intersegmental distances and chain flexibility. 相似文献