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The recently proposed scaling law relating the diffusion coefficient and the excess entropy of a liquid [M. Dzugutov, Nature (London) 381, 137 (1996)] is tested for several metals using molecular dynamics simulations. Interatomic potentials derived from the embedded atom method are used to study Ag, Au, Cu, Ni, Pd, Pt, Ni(3)Al, and AuPt and the angular dependent Stillinger-Weber form is used to investigate Si. 相似文献
3.
Nonequilibrium kinetic properties of alloy crystal-melt interfaces are calculated by molecular-dynamics simulations. The relationships between the interface velocity, thermodynamic driving force, and solute partition coefficient are computed and analyzed within the framework of kinetic theories accounting for solute trapping and solute drag. The results show a transition to complete solute trapping at high growth velocities, establish appreciable solute drag at low growth velocities, and provide insights into the nature of crystalline anisotropies and solute effects on interface mobilities. 相似文献
4.
The temperature profile around the moving solid–liquid interface during non-equilibrium molecular dynamics (MD) simulations of crystallization and melting is examined for HCP Mg and BCC Fe. An evident spike (valley) is found around the solid–liquid interface during solidification (melting). Considering the effect of a non-uniform temperature distribution, it is found that, if the actual interface temperature is adopted to compute the interface mobility, rather than the thermostat temperature (or the mean temperature of the whole system), the kinetic coefficient is approximately a factor of two larger than previous estimates. Although the magnitude of the kinetic coefficient is larger than the previous estimates, the crystalline anisotropies derived in the current work are consistent with earlier calculations. 相似文献
5.
J. W. Hoyt 《Experiments in fluids》1991,11(2-3):142-146
Based on an analogy to the Colebrook-White equation, a technique has been developed to allow polymer-solution extrapolation or “scaling” from one pipe size to another at constant values of ΔB. Each experimental data point can be transferred to a new pipe size by a simple, pocket-calculator method which preserves the experimental value of ΔB exactly. Thus scaling can be easily accomplished, without resorting to iteration or graphical techniques. The “negative-roughness” idea can also explain the loss of ΔB or drag reduction with increasing flow velocity. 相似文献
6.
In dendritic solidification, growth morphologies often display a pronounced sensitivity to small changes in composition. To gain insight into the origins of this phenomenon, we undertake an atomistic calculation of the magnitude and anisotropy of the crystal-melt interfacial free energy in a model alloy system featuring no atomic size mismatch and relatively ideal solution thermodynamics. By comparing the results of these calculations with predictions from recent phase-field calculations, we demonstrate that alloying gives rise to changes in free-energy anisotropies that are substantial on the scale required to induce changes in growth orientations. 相似文献
7.
Measurements of the electrical resistivity as a function of temperature from 250 to 270 K for Au and f.c.c. phase AuGa alloys are presented. The linear dependence of the resistivity with temperature and previous results of the superconducting transition temperature of the alloys are used to obtain a value for Tc of pure Au. From these results a new method is introduced to estimate the Coulomb pseudopotential μ1 for gold. 相似文献
8.
Cameras and lighting techniques which allow photographs to be taken of such water jet flow details as surface waves, transition, and spray eruption, as well as the various jet instability mechanisms, are described. While originally developed for very specialized cameras, many of the techniques can be adapted to conventional cameras. and other areas of research. 相似文献
9.
Hoyt JJ 《Physical review letters》2006,96(4):045702
A thermodynamic treatment of the freezing of fluids confined to nanosized closed pores is presented. The model includes the effects of pressure in the liquid, the volume change on solidification, and the strain energy in both the solidifying material and the wall material. When applied to the system of Pb droplets in Al, the model predicts an elevation of the melting point, in agreement with experiment. 相似文献
10.
Optical lattice induced light shifts in an yb atomic clock 总被引:1,自引:0,他引:1
Barber ZW Stalnaker JE Lemke ND Poli N Oates CW Fortier TM Diddams SA Hollberg L Hoyt CW Taichenachev AV Yudin VI 《Physical review letters》2008,100(10):103002
We present an experimental study of the lattice-induced light shifts on the (1)S(0) --> (3)P(0) optical clock transition (nu(clock) approximately 518 THz) in neutral ytterbium. The "magic" frequency nu(magic) for the 174Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p(3)P(0) --> 6s8p(3)P(0), 6s8p(3)P(2), and 6s5f(3)F(2) two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 microK deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10(-17). 相似文献