全文获取类型
收费全文 | 262篇 |
免费 | 23篇 |
国内免费 | 5篇 |
专业分类
化学 | 39篇 |
晶体学 | 13篇 |
力学 | 2篇 |
物理学 | 236篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 43篇 |
2008年 | 51篇 |
2007年 | 30篇 |
2006年 | 19篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有290条查询结果,搜索用时 15 毫秒
1.
Songqing Zhao Yuzi Liu Shufang Wang Zhen Liu Ze Zhang Huibin Lu Bolin Cheng 《Applied Surface Science》2006,253(2):726-729
B-doped ZnO thin films have been fabricated on fused quartz substrates using boron-ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32 ± 0.90 to 12.10 ± 1.00 GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380-780 nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2 × 1020 cm−3 and the resistivity lower than 3 × 10−3 Ω cm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films. 相似文献
2.
Polarization-resolved forward degenerate four-wave mixing (DFWM) in a nonresonant region revealed the effective third-order nonlinear susceptibility of colloidal CdTe nanocrystals (NCs) with the size near the Bohr radius and various concentrations. The second hyperpolarizabilities, and , of the CdTe NCs were ∼1.15 × 10−41 m5/V2 and ∼3.01 × 10−42 m5/V2 from the measurement of the concentration-dependent third-order nonlinear susceptibility of CdTe NCs, respectively. The ratio (/) of the hyperpolarizabilities was ∼0.26, which indicated a large contribution of an electronic polarization process to the third-order nonlinearity of CdTe NCs. 相似文献
3.
The Al-Cu-TM (TM = transition metal) alloy system has attracted great attention for both excellent glass-forming ability and its interesting physical properties. In this work, an investigation into the crystal, electrical and elastic properties of the AlCu2TM (TM = Ti, Zr, and Hf) compounds has been conducted by first-principles calculations based on density-functional theory. The fully relaxed structure parameters of the AlCu2TM compounds are in good agreement with previous experimental and other theoretical results. Besides, the cohesive energies of all the AlCu2TM compounds have been evaluated. The energy band and densities of state of these compounds are also obtained. According to the calculated single crystal elastic constants, all the compounds are mechanically stable. The polycrystalline bulk moduli, shear moduli, Young’s moduli and Poisson’s ratio have been deduced by using Voigt-Reuss-Hill (VRH) approximations. The calculated negative Cauchy pressure and ratio of bulk modulus to shear modulus indicated that the AlCu2TM compounds are ductile materials. The Debye temperatures of the AlCu2TM compounds decrease with increasing the TM (Ti, Zr, and Hf) atomic number. 相似文献
4.
A.F. Mesquita A.O. Porto G.M. de Lima J.M. Delgado F.S. Lameiras 《Solid State Communications》2005,136(3):133-137
Hexagonal and cubic cadmium selenide were prepared from a chemical route by using cadmium chloride and potassium selenium hydride obtained from reaction of selenium powder and potassium boron hydride. The product obtained was thermally treated under argon flux at 300, 500 and 600 °C for 2 h and characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The X-ray diffraction data were refined by Rietveld method and the structural parameters were determined for the phases of each annealed samples. At 300 °C five phases were identified: Cubic and hexagonal cadmium selenides and the contaminants: Potassium chloride, boron oxide and cadmium boron oxide. At 500 and 600 °C only the hexagonal cadmium selenide phase was identified besides the other above mentioned contaminant. 相似文献
5.
In dusty plasmas, overlapping Debye spheres around dust grains could produce an attractive force between them. Its effects on static structures of two-dimensional (2D) dusty plasmas are studied here by using molecular dynamics simulations. Results, in terms of the equilibrium radial distribution function, are compared with those deduced from purely repulsive Debye-Hückel or Yukawa potential for different Coulomb-coupling and screening parameters. The effect of the attractive force is found quite noticeable for usual experimental conditions, and becomes more pronounced for larger screening parameter κ. In particular, it is observed that for large κ the attractive force is dominant, and dust grains tend to aggregate and form patterns with scattering voids. 相似文献
6.
Transparent conducting zinc oxide thin films were prepared by spray pyrolytic decomposition of zinc acetate onto glass substrates with different thickness. The crystallographic structure of the films was studied by X-ray diffraction (XRD). XRD measurement showed that the films were crystallized in the wurtzite phase type. The grain size, lattice constants and strain in films were calculated. The grain size increases with thickness. The studies on the optical properties show that the direct band gap value increases from 3.15 to 3.24 eV when the thickness varies from 600 to 2350 nm. The temperature dependence of the electrical conductivity during the heat treatment was studied. It was observed that heat treatment improve the electrical conductivity of the ZnO thin films. The conductivity was found to increase with film thickness. 相似文献
7.
The influence of long-distance oxygen plasma sterilization on surface properties of substrate material, i.e., medical poly(tetrafluoroethylene) (PTFE), and aging effect of these sterilized PTFE film surfaces were investigated by contact angle measurement, mass loss determination, scanning electron microscopy (SEM) as well as bacterial adhesion and platelet adhesion measurements in vitro, respectively. The changes in chemical structure of sterilized PTFE film were followed using X-ray photoelectron spectroscopy (XPS). As a result of plasma sterilization oxygen-containing functional groups (such as CO and CO), especially the CO group are introduced into PTFE surfaces, and thus pronounced increases of surface free energy and surface wettability are presented when the sample positions are within 0-40 cm. The film surface wettability degrades little as the aging time continued as long as 190 days. At the same time, the minimal surface degradation and damage occur on the sterilized PTFE when the sample position is at 40 cm. Moreover, the antibacterial adhesion and blood compatibility of sterilized PTFE surface are enhanced and the optimal effects are also obtained at 40 cm. The essential reason may be due to the optimal equilibrium between surface wettability and surface damage, which is achieved at 40 cm. Overall, of the surface properties of long-distance oxygen plasma sterilized PTFE analyzed, the sterilization at 40 cm is optimal. 相似文献
8.
R. Hrach P. Barto? V. Hrachová 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):417-423
The influence of the unevenness of substrates immersed into plasma important for plasma-based treatment of materials were
studied by computer experiment. The role of both substrate properties and plasma parameters was investigated. For this analysis
the combination of multidimensional fluid modelling and particle simulation was used. The fluid part of our model consisted
of continuity equations for all charged species, energy balance equation for electrons and Poisson equation. The basic scattering
processes were also included. The particle simulation technique was used both for the calculation of electron energy distribution
function and for the derivation of quantities characterising plasma-surface interaction. This approach enabled us to study
in detail the structure of the sheath and presheath near metal substrates with realistic geometries and finite dimensions.
The main attention was devoted to the influence of substrate geometry in both macroscopic and microscopic spatial scales on
the local electric fields in plasma. 相似文献
9.
F. X. Bronold H. Deutsch H. Fehske 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):519-544
Plasma-boundaries floating in an ionized gas are usually negatively charged. They accumulate electrons more efficiently than
ions leading to the formation of a quasi-stationary electron film at the boundaries. We propose to interpret the build-up
of surface charges at inert plasma boundaries, where other surface modifications, for instance, implantation of particles
and reconstruction or destruction of the surface due to impact of high energy particles can be neglected, as a physisorption
process in front of the wall. The electron sticking coefficient se and the electron desorption time τe, which play an important role in determining the quasi-stationary surface charge, and about which little is empirically and
theoretically known, can then be calculated from microscopic models for the electron-wall interaction. Irrespective of the
sophistication of the models, the static part of the electron-wall interaction determines the binding energy of the electron,
whereas inelastic processes at the wall determine se and τe. As an illustration, we calculate se and τe for a metal, using the simplest model in which the static part of the electron-metal interaction is approximated by the classical
image potential. Assuming electrons from the plasma to loose (gain) energy at the surface by creating (annihilating) electron-hole
pairs in the metal, which is treated as a jellium half-space with an infinitely high workfunction, we obtain se≈10-4 and τe≈10-2 s. The product seτe≈10-6 s has the order of magnitude expected from our earlier results for the charge of dust particles in a plasma but individually se is unexpectedly small and τe is somewhat large. The former is a consequence of the small matrix elements occurring in the simple model while the latter
is due to the large binding energy of the electron. More sophisticated theoretical investigations, but also experimental support,
are clearly needed because if se is indeed as small as our exploratory calculation suggests, it would have severe consequences for the understanding of the
formation of surface charges at plasma boundaries. To identify what we believe are key issues of the electronic microphysics
at inert plasma boundaries and to inspire other groups to join us on our journey is the purpose of this colloquial presentation. 相似文献
10.
superconformal algebra is
algebra with two Virasoro operators. The Kac determinant is calculated and the complete list of unitary representations is determined. Two types of extensions of
algebra are discussed. A new approach to construction of
algebras from rational conformal field theories is proposed. 相似文献