全文获取类型
收费全文 | 164526篇 |
免费 | 790篇 |
国内免费 | 323篇 |
专业分类
化学 | 63774篇 |
晶体学 | 2601篇 |
力学 | 10418篇 |
综合类 | 8篇 |
数学 | 29984篇 |
物理学 | 58854篇 |
出版年
2022年 | 535篇 |
2021年 | 478篇 |
2020年 | 447篇 |
2019年 | 427篇 |
2018年 | 10075篇 |
2017年 | 10954篇 |
2016年 | 5247篇 |
2015年 | 1582篇 |
2014年 | 1119篇 |
2013年 | 2626篇 |
2012年 | 6900篇 |
2011年 | 16274篇 |
2010年 | 9841篇 |
2009年 | 10004篇 |
2008年 | 14072篇 |
2007年 | 17742篇 |
2006年 | 2667篇 |
2005年 | 9636篇 |
2004年 | 5748篇 |
2003年 | 5413篇 |
2002年 | 3164篇 |
2001年 | 3182篇 |
2000年 | 2480篇 |
1999年 | 1600篇 |
1998年 | 1130篇 |
1997年 | 1078篇 |
1996年 | 1073篇 |
1995年 | 893篇 |
1994年 | 796篇 |
1993年 | 706篇 |
1992年 | 1024篇 |
1991年 | 1024篇 |
1990年 | 924篇 |
1989年 | 834篇 |
1988年 | 829篇 |
1987年 | 887篇 |
1986年 | 739篇 |
1985年 | 980篇 |
1984年 | 941篇 |
1983年 | 670篇 |
1982年 | 659篇 |
1981年 | 627篇 |
1980年 | 591篇 |
1979年 | 736篇 |
1978年 | 772篇 |
1977年 | 693篇 |
1976年 | 646篇 |
1975年 | 536篇 |
1974年 | 574篇 |
1973年 | 547篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
It is found that, when a bismuth crystal is subjected simultaneously to concentrated loading and a dc magnetic field, the magnetoplastic effect manifests itself as an abrupt decrease in the average length of wedge twins on the (111) cleavage plane (and, hence, as a decrease in the total twinned volume of the crystal) as a threshold value of the magnetic field is reached. However, the magnetic field stimulates glide deformation, which is indicated by an increase in the size of dislocation rosettes. The microhardness of a crystal varies smoothly and tends to increase with increasing magnetic field. The last phenomenon is accounted for by hardening of the crystal under the indenter in the presence of a magnetic field, because several slip systems become operative. 相似文献
122.
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
123.
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
124.
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
125.
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
126.
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
127.
O. Yu. Borkovskaya N. L. Dmitruk I. B. Ermolovich R. V. Konakova V. V. Milenin 《Technical Physics》2004,49(3):325-329
The properties of nonrectifying AuGe/GaAs (Al0.4Ga0.6As) contacts exposed to heat treatment, 60Co γ radiation, and γ radiation combined with the application of an electrical bias are studied. A correlation between the
type of interfacial interaction in the contacts and their resistance is found. Results obtained are explained in terms of
a diffusion model with a movable boundary of the metal layer. 相似文献
128.
The structure, composition, and mechanical properties of iron-alloyed TiC-TiNi composite materials are studied. When the titanium
carbide framework is sintered with iron and then impregnated with titanium nickelide, iron atoms are found to diffuse into
the matrix and form the B2 structure that is inhomogeneous (gradient) in chemical composition and properties and exhibits various temperatures of martensitic
transformation. The latter fact shows up in the broadening of the martensitic transformation hysteresis and its shift toward
low temperatures with increasing iron content. At room temperature, the strength properties of gradient-matrix TiC-TiNi composites
are shown to increase with iron concentration. 相似文献
129.
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
130.