全文获取类型
收费全文 | 1491880篇 |
免费 | 26033篇 |
国内免费 | 7938篇 |
专业分类
化学 | 763259篇 |
晶体学 | 21165篇 |
力学 | 78076篇 |
综合类 | 117篇 |
数学 | 253689篇 |
物理学 | 409545篇 |
出版年
2021年 | 13698篇 |
2020年 | 16059篇 |
2019年 | 16203篇 |
2018年 | 17535篇 |
2017年 | 16218篇 |
2016年 | 30281篇 |
2015年 | 21397篇 |
2014年 | 30749篇 |
2013年 | 74830篇 |
2012年 | 46292篇 |
2011年 | 50087篇 |
2010年 | 42507篇 |
2009年 | 43605篇 |
2008年 | 47007篇 |
2007年 | 44681篇 |
2006年 | 44835篇 |
2005年 | 40468篇 |
2004年 | 38862篇 |
2003年 | 34962篇 |
2002年 | 34613篇 |
2001年 | 35135篇 |
2000年 | 28897篇 |
1999年 | 24492篇 |
1998年 | 21824篇 |
1997年 | 21609篇 |
1996年 | 21502篇 |
1995年 | 19442篇 |
1994年 | 18947篇 |
1993年 | 18534篇 |
1992年 | 19280篇 |
1991年 | 19399篇 |
1990年 | 18617篇 |
1989年 | 18600篇 |
1988年 | 18229篇 |
1987年 | 18090篇 |
1986年 | 17046篇 |
1985年 | 23360篇 |
1984年 | 24358篇 |
1983年 | 20406篇 |
1982年 | 21910篇 |
1981年 | 21138篇 |
1980年 | 20453篇 |
1979年 | 20994篇 |
1978年 | 22081篇 |
1977年 | 21765篇 |
1976年 | 21534篇 |
1975年 | 20287篇 |
1974年 | 19978篇 |
1973年 | 20410篇 |
1972年 | 14859篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
In terms of two-dimensional dislocation-disclination dynamics, a theoretical model is developed to describe the decay of a low-angle tilt boundary in a deformed nanocrystalline material under the action of an externally applied elastic stress and of the elastic field of a neighboring decayed boundary. The critical external stresses are calculated at which the boundary decays and the dislocations making up this boundary either are trapped by the boundary that decayed earlier or break away from both boundaries. The decay of a low-angle tilt boundary is shown to result in a substantial decrease in the critical decay stresses for the neighboring boundaries, which can cause an avalanche-like chain decay of low-angle boundaries yielding high-density ensembles of mobile dislocations capable of carrying substantial plastic deformations and of forming shear bands in deformed nanocrystalline materials. 相似文献
972.
The exact solution of the problem of ion transport current in an electrolyte in the presence of a conjugate flow of solvent
is obtained in the framework of the one-dimensional Gurevich-Kharkats diffusion-migration model; the conditions for the existence
of the solution are analyzed. 相似文献
973.
Spatial parameters of the X-ray radiation produced by a high-voltage nanosecond discharge evolving in air under atmospheric
pressure in the rod (cathode)-plane electrode system with a 10-cm electrode spacing are studied experimentally. A ∼170-ns
voltage pulse with an amplitude of ∼200 kV and 10-ns rise time is applied to the cathode. The photoelectronic method is used
to study, under the same conditions, the integrated (over the gap) characteristics of the radiation, in particular, the duration
of its generation. It is found that, when the size of the X-ray source is not smaller than that of the discharge region of
diffusive luminescence, radiation from the cathode region of the gap is primarily observed (i.e., from the region where the
electric field distribution is sharply inhomogeneous). The X-ray generation is usually observed after the bridging of the
discharge gap, the X-ray pulse having a rise time of ∼3 ns, a duration of ∼10 ns, and an effective radiation energy of ∼6
keV. 相似文献
974.
V. L. Bychkov L. P. Grachev I. I. Esakov A. A. Ravaev K. V. Khodataev 《Technical Physics》2004,49(7):833-838
A longitudinal dc electric discharge in a submerged high-pressure supersonic air jet is described. Photographs of the discharge
are provided. The experimental voltage across the discharge gap and the discharge current are given for two resistances of
the resistor that limits the discharge current over a certain range of the discharge channel length along the air flow. The
current-voltage discharge characteristic is provided at a constant discharge length. The main discharge characteristics are
obtained from a comparison of the experimental and theoretical results calculated on the basis of the simplest model. 相似文献
975.
The translational nonequilibrium zone in a shock wave is considered for a gas consisting of light particles and a small addition
of heavy particles. The gas is taken to be two-dimensional, and long-range forces are assumed to be absent. In the framework
of this approximation, a program for molecular dynamics simulation of the gas is developed. It is applied to calculate a particle
distribution function in the shock wave, to analyze the time evolution of the distribution function, and to study its dependence
on the gas composition. 相似文献
976.
Stimulated Raman scattering (SRS) in a long-distance fiber-optic communication line with wavelength-division multiplexing (WDM) is studied theoretically at a high power of the signal transmitted. A new criterion for determining the SRS threshold is used to calculate the critical input power versus the number of optical channels and frequency separation between them. The theoretical model is verified experimentally. SRS interaction between two channels in a communication line with an SRS amplifier for which the optical waveguide of the line serves as a nonlinear medium is measured. 相似文献
977.
Russian Physics Journal - 相似文献
978.
Russian Physics Journal - 相似文献
979.
The problem of dimensionality of time is considered. The space-time curvature is shown to result not only from the presence of the gravitational field but also from a certain other field whose potential is a positive value. 相似文献
980.
Gavrilyuk A. A. Semenov A. L. Gavrilyuk A. V. Mokhovikov A. Yu. Zubritsky S. M. Petrov A. L. 《Russian Physics Journal》2004,47(7):750-755
It has been studied how the conditions of machining and the elastic tensile stresses affect the magnetic properties of amorphous metal wires of composition Fe75Si10B15 produced by drawing from a melt. The magnetic characteristics of wires subjected to both thermal treatment and treatment with a continuous electric current of different magnitude have been investigated. The residual induction of wires is their magnetic parameter most sensitive to the conditions of treatment. The dependences of the residual induction on temperature and on the magnitude of the treating electric current are qualitatively similar. The greatest changes in residual induction are observed in the range of treating electric currents from 0.5 to 0.8 A, which can be associated with the processes of structural relaxation and crystallization occurring in the wires. The run of the dependence of the residual induction on the magnitude of tensile stresses is nonmonotonic in character and is determined by the level of internal hardening stresses of the test wires. 相似文献