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排序方式: 共有169条查询结果,搜索用时 15 毫秒
41.
The structural phase transformations of Cd chalcogenide compounds (CdS, CdSe, and CdTe) under high pressure are studied using
the local approximation to the density functional theory, and the one-electron equations are solved by means of the full potential
linear muffin-tin-orbital method. CdS, CdSe, and CdTe are found to have nearly similar behaviour of the structural properties
under high pressure. In the CdS compound, thePmmn phase is predicted to be thermodynamically stable after the rock-salt structure, and theCmcm structure is found to be thermodynamically stable before the rock-salt structure in both CdSe and CdTe. The resulting structural
properties of the zinc-blende, wurtzite, cinnabar, rock-salt,Pmmn, CsCl,Cmcm, and β-Sn phases for these considered compounds are found to be in agreement with the existing experimental data. 相似文献
42.
T. Palasyuk 《Solid State Communications》2007,141(6):354-358
Systematics of hcp-fcc phase transition observed in a series of lanthanide and yttrium trihydrides has been established. Based on the established systematics the prediction of the hcp-fcc transition pressure for the rest of the lanthanide trihydrides has been made. The role of H-H repulsive interaction as a probable transition promoter is discussed. 相似文献
43.
J. Badro J.P. Itié A. Polian 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):265-268
X-ray diffraction (XRD) experiments have been carried out on quartz-like GaPO4 at high pressure and room temperature. A transition to a high pressure disordered crystalline form occurs at 13.5 GPa. Slight
heating using a YAG infrared laser was applied at 17 GPa in order to crystallize the phase in its stability field. The structure
of this phase is orthorhombic with space group Cmcm. The cell parameters at the pressure of transition are a
=7.306?, b
=5.887? and c
=5.124?.
Received: 7 October 1997 / Received in final form: 17 November 1997 / Accepted: 18 November 1997 相似文献
44.
A. Elior B. D. Barmashenko E. Lebiush S. Rosenwaks 《Applied physics. B, Lasers and optics》1995,61(1):37-47
We report on detailed experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser. The laser has a 5 cm long active medium and utilizes a simple sparger-type O2(1
) chemical generator and a medium-size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 25 W of cw laser emission at 1.315 µm are obtained in the present experiments. The small size and the simple structure of the laser system and its stable operation for long times make it a convenient tool for studying parameters important for high-power supersonic iodine lasers and for comparison to model calculations. The lasing power is studied as a function of the molar flow rates of the various reagents, and conditions are found for optimal operation. Good agreement is found between the experimental results and calculations based on a simple one-dimensional semi-empirical model, previously developed in our laboratory and modified in the present work. The model is used to predict optimal values for parameters affecting the laser performance that are difficult to examine in the present experimental system. 相似文献
45.
L. Tsonev 《Applied physics. B, Lasers and optics》1984,34(2):93-96
A -type two-electrode system on a Ti diffused optical waveguide in LiNbO3 has been studied in symmetrical and in asymmetrical operation regimes. In the first case the device acts as a beam splitter or focuser, depending on the polarity of the applied voltage. In the second case the device acts as a scanner. The driving voltage is relatively low. Possible applications are optical communication systems and optical processing of information. 相似文献
46.
The density of states (DOS) of fcc and hcp structures of Al has been calculated for normal and high pressures. It has been found that the DOS of both structures, near the Fermi level, is similar over a range of compressed volumes close to the fcc-hcp transition volume (V/V0∼0.53). This similarity is the reason for the reported coexistence of fcc-hcp phases over a wide range of pressures near the fcc-hcp phase transition. All calculations have been performed using the FP-LAPW method with GGA. 相似文献
47.
Ge-doped Sb2Te3 films were prepared by magnetron sputtering of Ge and Sb2Te3 targets on SiO2/Si (1 0 0) substrates. The effect of Ge doping on the structure was studied in details by X-ray diffraction, differential scanning calorimetry, and X-ray photoelectron spectroscopy measurements. It is indicated that Ge atoms substitute for Sb/Te in lattice sites and form Ge-Te bonds, moreover, a metastable phase was observed in Ge-doped specimens. Both crystallization temperature and resistivity of amorphous Sb2Te3 increase after Ge doping, which are beneficial for improving room temperature stability of the amorphous state and reducing the SET current of chalcogenide random access memory. 相似文献
48.
Ti/Ge2Sb2Te5/Ti thin films deposited by a sputtering method on SiO2/Si substrates were annealed at 400 °C in N2 atmosphere and characterized by using transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) in order to investigate the inter-diffusion of the Ti/Ge2Sb2Te5/Ti system due to annealing. The TEM and AES results showed that the interface between the Ti and the Ge2Sb2Te5 layers was unstable and Ti atoms were incorporated into the Ge2Sb2Te5 thin film upon annealing. The Te and Sb atoms of the Ge2Sb2Te5 layer diffused into the Ti layer. The intermixing layers between the Ge2Sb2Te5 layer and two Ti layers were formed. These results indicate that the microstructural properties of the Ti/Ge2Sb2Te5/Ti systems can be degraded by the postgrowth thermal annealing. 相似文献
49.
X. Gu S. Zhu D. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):461-466
The steady state properties of a noise-driven bistable system are
investigated when there are two different kinds of time delays
existed in the deterministic and fluctuating forces respectively.
Using the approximation of the probability density approach, the
delayed Fokker-Planck equation is obtained. The stationary
probability distribution (SPD) and the variance of the system are
derived. It is found that the time delay τ in the deterministic
force can reduce the fluctuations while the time delay β in
the fluctuating force can enhance the fluctuations. Numerical
simulations are presented and are in good agreement with the
approximate theoretical results. 相似文献
50.
After classifying amorphous materials according to their topology, we review a recently proposed theory of pressure amorphization
(PA) that arises from some degree of displacive disorder while retaining a crystalline topology. That theory is based on the
notion that one or more branches of the phonon spectrum become soft and flat with increasing pressure and is illustrated by
a simple model that possesses the range of features displayed by many of the materials which undergo PA with displacive disorder.
We report the results of Langevin simulations of the simple model which show how the probability of amorphization increases
with the number of unit cells in the system and support our theory. We comment on how to generalize the model for the study
of real systems.
Received 29 march 2002 相似文献