全文获取类型
收费全文 | 485篇 |
免费 | 1篇 |
专业分类
化学 | 128篇 |
晶体学 | 5篇 |
力学 | 68篇 |
数学 | 46篇 |
物理学 | 239篇 |
出版年
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 3篇 |
2014年 | 23篇 |
2013年 | 21篇 |
2012年 | 20篇 |
2011年 | 17篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 23篇 |
2005年 | 21篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1966年 | 3篇 |
1917年 | 1篇 |
排序方式: 共有486条查询结果,搜索用时 390 毫秒
41.
I. A. Akimov V. F. Sapega D. N. Mirlin V. M. Ustinov 《Physica E: Low-dimensional Systems and Nanostructures》2001,10(4):129
We have studied the dependence of hot electron scattering rate on temperature in n-GaAs/AlAs types I and II multiple quantum wells. For a sample with well width 37 Å, which is on the borderline between types I and II band alignment, the increase of the temperature in the range 6–80 K leads to the strong decrease of the hot electron scattering rate. We explain this result by ionization of donors and transfer of cold electrons from the Γ-valley of GaAs to the X-valley of AlAs. 相似文献
42.
R. I. Zainullina N. G. Bebenin V. V. Mashkautsan A. M. Burkhanov Yu. P. Sukhorukov V. V. Ustinov V. G. Vasil’ev B. V. Slobodin 《Physics of the Solid State》2000,42(2):292-297
An experimental study is reported of the temperature dependences of the electrical resistivity and magnetoresistance, thermal and magnetothermal EMF, the Hall effect, optical reflectance, sound velocity, and internal friction of polycrystalline lanthanum manganite La0.60Eu0.07Sr0.33MnO3 carried out within the 77–430-K temperature range. Substitution of a small amount of europium for lanthanum has been found to result in a considerable decrease in the resistivity and a change in the behavior of its temperature dependence. Four characteristic temperatures at which special features are observed in the above properties have been identified. The discussion of the conduction mechanisms involved is based on the concept of mobility edge motion. 相似文献
43.
A. B. Drovosekov N. M. Kreines D. I. Kholin A. V. Korolev M. A. Milayev L. N. Romashev V. V. Ustinov 《JETP Letters》2008,88(2):118-122
The evolution of the magnetic properties of Fe/Cr superlattices with a decrease in the nominal thickness of the iron layers down to atomic dimensions at which these layers are not continuous has been analyzed. Investigations have been carried out with multilayer samples with Fe-layer thicknesses in a range of 2–6 Å and Cr-layer thicknesses of 10 and 20 Å. It has been found that the system with various Fe-layer thicknesses and at various temperatures exhibits various magnetic phases—superparamagnetic, magnetically ordered, and nonergodic—characterized by the dependence of the magnetization of the sample on its magnetic prehistory. It has been shown that the observed nonergodic phase has the properties of a spin glass. A qualitative phase diagram of the magnetic states of the system has been obtained. 相似文献
44.
M. D. Ustinov 《Fluid Dynamics》1966,1(3):44-48
The equations of one-dimensional and plane steady adiabatic motion of an ideal gas are transformed to a new form in which the role of the independent variables are played by the stream function and the function introduced by Martin [1, 2], It is shown that the function retains a constant value on a strong shock wave (and on a strong shock for plane flows). For one-dimensional isentropic motions the resulting transformation permits new exact solutions to be obtained from the exact solutions of the equations of motion. It is shown also that the one-dimensional motions of an ideal gas with the equation of state p=f(t) and the one-dimensional adiabatic motions of a gas for which p=f() are equivalent (t is time, is the stream function). It is shown that if k=s=–1, m and n are arbitrary (m+n0) and =1, the general solution of the system of equations which is fundamental in the theory of one-dimensional adiabatic self-similar motions [3] is found in parametric form with the aid of quadratures. Plane adiabatic motions of an ideal gas having the property that the pressure depends only on a single geometric coordinate are studied. 相似文献
45.
M. D. Ustinov 《Fluid Dynamics》1984,19(2):327-330
A study is made of the motion of a piston without initial velocity under the influence of gas pressure. Under the assumption that the temperature gradient is constant and fairly small, expressions are obtained for the distributions of the gas-dynamic parameters in the disturbed region between the piston and the leading edge of the sound wave propagating through the gas at rest.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 177–180, March–April, 1984. 相似文献
46.
E. V. Cherdantseva D. V. Starichenko P. A. Slepukhin R. I. Ishmetova Yu. N. Shvachko A. V. Korolev G. L. Rusinov V. V. Ustinov A. I. Matern V. N. Charushin 《Russian Chemical Bulletin》2010,59(4):717-723
Dinuclear complexes of CuII with 3-(3,5-dimethylpyrazol-1-yl)-6-(2-hydroxyethylami-no)-1,2,4,5-tetrazine (1) and CoII with 3-(3,5-dimethylpyrazol-1-yl)-6-(piperidin-1-yl)-1,2,4,5- tetrazine (2) were synthesized and structurally characterized, and the magnetic (SQUID) and resonance (EPR) properties of van der Waals crystals based on these complexes were studied. Unusual behavior of the effective magnetic moment μeff(T) is observed at T < 60 K. A nonmonotonic increase in μeff(?) for 1 (s~6 %) and a 20% reduction of μeff(?) for 2 have a common origin and are due to the influence of spin-orbital coupling on the character of the splitting between the t2g and eg levels of the central ion. Distortions of the coordination site “switch on” a positive (1) or negative (2) contribution of the orbital magnetic moment near 6 K. Irreversible temperature behavior of μeff(T) in the heating and cooling regimes in the vicinity of 60 K suggests that the character of structural distortions and the magnetic properties are related to ligand geometry. This factor plays a significant role in crystal engineering of magnetoactive structures with polynitrogen ligands. 相似文献
47.
Ustinov AB Demidov VE Kondrashov AV Kalinikos BA Demokritov SO 《Physical review letters》2011,106(1):017201
The transition from stationary to chaotic spin-wave soliton trains has been observed. The experiment utilized cw excitation of envelope solitons through self-modulation instability of spin waves. By increasing the spin-wave power, the secondary self-modulation instability succeeded the primary modulation instability, resulting in after-modulation of the soliton train amplitude. Further increase of the spin-wave power led to development of the higher-order instabilities, resulting in formation of the chaotic soliton train. 相似文献
48.
A. B. Ustinov P. I. Kolkov A. A. Nikitin B. A. Kalinikos Y. K. Fetisov G. Srinivasan 《Technical Physics》2011,56(6):821-825
Planar phase shifters fabricated based on ferrite-ferroelectric layered structures are studied experimentally. The structures
served as waveguides for spin-electromagnetic waves, whose phase shift was controlled by both electric and magnetic fields.
The measurements were performed in the magnetic field range from 900 to 2100 Oe, which corresponds to operating frequencies
from 4.0 to 8.5 GHz, with 5- to 20-μm-thick yttrium-iron garnet ferrite films and 200- to 500-μm-thick barium-strontium titanate
ferroelectric plates. It is shown that the phase shift may exceed 180° and is a function of the magnetic and electric fields
and also of the thickness of the ferrite and ferroelectric layers. 相似文献
49.
We investigate the propagation of a longitudinal-transverse elastic pulse in a statically deformed crystal containing paramagnetic impurities and placed in an external magnetic field. We derive a system of three nonlinear wave equations describing the interaction of the pulse with the paramagnetic impurities in the quasiresonance approximation in the Faraday geometry. We assume that the transverse components of the pulse, which cause quantum transitions, have carrier frequencies and are short-wave (acoustic), while the longitudinal component has no carrier frequency and is long-wave. We show that in the case of an equilibrium initial distribution of populations of quantum levels of paramagnetic impurities, the coupling between the longitudinal and transverse components is weak, the pulse is therefore strictly transverse, and its dynamics are described by the Manakov system. With a nonequilibrium initial distribution of populations, conditions of effective interaction between all components of the elastic pulse can be reached, and their nonlinear dynamics are described by a vector generalization of the Zakharov equations. In the case of a unidirectional propagation of the pulse, these equations reduce to the Yajima-Oikawa vector system. We show that the obtained system of equations and its version with an arbitrary number of short-wave components can be integrated using the inverse scattering transform. We construct infinite hierarchies of solutions of the Yajima-Oikawa vector system (including a solution on a nontrivial background). We consider stationary (complex-valued Garnier system) and self-similar reductions of that system, also admitting a representation in the form of compatibility conditions. 相似文献
50.
V. M. Buznik L. N. Ignat’eva V. G. Kuryavyi E. B. Merkulov N. N. Savchenko A. Yu. Ustinov A. B. Slobodyuk L. N. Nikitin 《Polymer Science Series A》2010,52(12):1334-1343
Microsized spherical core-shell particles consisting of hydrocarbon cores encapsulated into fluoropolymer shells are obtained
in supercritical carbon dioxide. Paraffins serve as a core material, while the polymer shell is formed from ultradispersed
polytetrafluoroethylene. The morphology and molecular structure in the bulk and on the surface of the particles and the influence
of conditions of particle formation on the shell thickness and the thermal properties of the materials are studied. The materials
are composites comprised of paraffin cores coated with shells of loosened globular fluoropolymer particles with sizes of 0.2–1.7
μm. The shells is built of low- and high-molecular-mass fractions consisting of CF3(CF2)nCF3 molecular chains with different lengths. The shell thickness is governed by preparation conditions, exposure time, and the
percentage of the polymer in the initial dispersion. 相似文献