全文获取类型
收费全文 | 298028篇 |
免费 | 1569篇 |
国内免费 | 326篇 |
专业分类
化学 | 136979篇 |
晶体学 | 4658篇 |
力学 | 16873篇 |
综合类 | 3篇 |
数学 | 42012篇 |
物理学 | 99398篇 |
出版年
2021年 | 3094篇 |
2020年 | 3415篇 |
2019年 | 4192篇 |
2018年 | 6229篇 |
2017年 | 6442篇 |
2016年 | 7942篇 |
2015年 | 3521篇 |
2014年 | 6879篇 |
2013年 | 12118篇 |
2012年 | 10141篇 |
2011年 | 11795篇 |
2010年 | 9984篇 |
2009年 | 10137篇 |
2008年 | 11409篇 |
2007年 | 11203篇 |
2006年 | 9963篇 |
2005年 | 8598篇 |
2004年 | 8353篇 |
2003年 | 7764篇 |
2002年 | 8049篇 |
2001年 | 7663篇 |
2000年 | 6057篇 |
1999年 | 4486篇 |
1998年 | 4262篇 |
1997年 | 4124篇 |
1996年 | 3734篇 |
1995年 | 3297篇 |
1994年 | 3360篇 |
1993年 | 3375篇 |
1992年 | 3380篇 |
1991年 | 3788篇 |
1990年 | 3788篇 |
1989年 | 3795篇 |
1988年 | 3547篇 |
1987年 | 3629篇 |
1986年 | 3320篇 |
1985年 | 3853篇 |
1984年 | 4087篇 |
1983年 | 3489篇 |
1982年 | 3688篇 |
1981年 | 3373篇 |
1980年 | 3132篇 |
1979年 | 3622篇 |
1978年 | 3691篇 |
1977年 | 3856篇 |
1976年 | 3929篇 |
1975年 | 3672篇 |
1974年 | 3527篇 |
1973年 | 3688篇 |
1972年 | 3177篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Lasing and discharge in mixtures of SF6 with hydrogen and hydrocarbons are investigated. If the chemical reaction is initiated by a self-sustained discharge (a generator
with both an inductive and capacitive energy storage can be used), the maximum lasing efficiency is attained at high values
of the ratio E/p (where E is the electric field intensity and p is the pressure in the mixture) if shaped electrodes and preionization of the discharge gap are employed. For the first time,
the lasing efficiency obtained in a nonchain HF laser is as high as 10% of the energy deposit and 4.5% of the stored energy
for a specific radiation energy of ≈140 J/(l atm). At high efficiencies, the emission spectrum of the nonchain HF laser significantly
broadens and cascade lasing at P(3-2) → P(2-1) → P(1-0) vibrational transitions for several rotational lines is realized. 相似文献
992.
R. M. Sardarly O. A. Samedov I. Sh. Sadykhov V. A. Aliev 《Physics of the Solid State》2003,45(6):1118-1121
The relaxor properties of Fe-doped TlInS2 crystals are investigated. It is shown that Fe-doped TlInS2 compounds exhibit all features inherent in relaxor ferroelectric materials. The temperature range of existence of the microdomain (relaxor) state and the temperature of the transition from this state to a macro-domain state are determined. 相似文献
993.
V. L. Tsymbalenko 《JETP Letters》2003,78(8):493-496
The kinetics of formation of an anomalous phase from a solution with a small 3He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ~30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface. 相似文献
994.
Baidyshev V. S. Udodov V. N. Popov A. A. Potekaev A. I. 《Russian Physics Journal》2003,46(12):1193-1198
The paper offers a method for calculating phase diagrams of polytype transformations in close-packed crystals based on the generalized axial Ising's model of finite dimensions at non-zero temperatures. Using the Metropolis algorithm, the behavior of systems with polytype transitions is studied under the conditions of changing external shear stress and temperature. The longest polytype period considered here is taken to be 30 close-packed planes. 相似文献
995.
996.
G. M. Maksimova A. L. Chuvilin E. M. Moroz V. A. Likholobov K. I. Matveev 《Kinetics and Catalysis》2004,45(6):870-878
Conditions for the preparation of stable aqueous monometallic and bimetallic colloidal solutions (sols) of noble metals (Ru, Rh, Pd, Pt, Ir, Ag, and Au) in the presence of polyoxometalates containing W, Mo, V, and Nb were found. The stability of sols against coagulation at room temperature was studied. The metal/C samples prepared by metal adsorption from sols were studied by powder X-ray diffraction analysis and transmission electron microscopy. The following factors of importance for the preparation of a stable sol are discussed: (1) the formation of a sol of a metal polyhydroxo complex stabilized by a polyoxometalate (preliminary stage) and (2) the formation of polyoxometalate-metal clusters in the course of reduction of polyhydroxo complexes.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 921–929.Original Russian Text Copyright © 2004 by Maksimova, Chuvilin, Moroz, Likholobov, Matveev. 相似文献
997.
998.
999.
E. A. Bogdanov A. A. Kudryavtsev L. D. Tsendin R. R. Arslanbekov V. I. Kolobov V. V. Kudryavtsev 《Technical Physics》2003,48(9):1151-1158
Comprehensive self-consistent simulations of the positive column plasma of a dc oxygen discharge are performed with the help
of commercial CFDRC software (), which enables one to carry out computations in an arbitrary 3D geometry using fluid equations for heavy components and
a kinetic equation for electrons. The main scaling laws for the spatial distributions of charged particles are determined.
These scaling laws are found to be quite different in the parameter ranges that are dominated by different physical processes.
At low pressures, both the electrons and negative ions in the inner discharge region obey a Boltzmann distribution; as a result,
a flat profile of the electron density and a parabolic profile of the ion density are established there. In the ion balance,
transport processes prevail, so that ion heating in an electric field dramatically affects the spatial distribution of the
charged particles. At elevated pressures, the volume processes prevail in the balance of negative ions and the profiles of
the charged particle densities in the inner region turn out to be similar to each other. 相似文献
1000.
The reasons for the existence of various scenarios for structural transformations in disordered condensed media, such as liquids and amorphous substances, where both smeared transformations and sharp first-order transitions may occur, were analyzed. The ratio between the spatial scale of structural correlations and the size of the smallest possible region occupied by a new phase in the matrix of initial modification is the key parameter determining the scenario for equilibrium phase transformations in liquids. In amorphous substances, the experimentally observed transformations occur far from equilibrium, and the possible size of the region occupied by the new phase corresponds to the minimal nucleus size. For some amorphous solids, quantitative analysis of the transformation width was carried out and the main classes of covalent substances, in which the smeared or sharp transitions occur, were revealed. Specific features of the interparticle interactions determining various transformation scenarios are discussed. 相似文献