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31.
[reaction: see text] New methods for the palladium-catalyzed cyanation of aryl and heteroaryl chlorides have been developed, featuring sterically demanding, electron-rich phosphines. Highly challenging electron-rich aryl chlorides, in addition to electron-neutral and electron-deficient substrates, as well as nitrogen- and sulfur-containing heteroaryl chlorides can all undergo efficient cyanation under relatively mild conditions using readily available materials. In terms of substrate scope and temperature, these methods compare very favorably with the state-of-the-art cyanations of aryl chlorides.  相似文献   
32.
We report transverse momentum (p(T)≤15 GeV/c) spectra of π(±), K(±), p, p[over ˉ], K(S)(0), and ρ(0) at midrapidity in p+p and Au+Au collisions at √S(NN)=200 GeV. Perturbative QCD calculations are consistent with π(±) spectra in p+p collisions but do not reproduce K and p(p[over ˉ]) spectra. The observed decreasing antiparticle-to-particle ratios with increasing p(T) provide experimental evidence for varying quark and gluon jet contributions to high-p(T) hadron yields. The relative hadron abundances in Au+Au at p(T)?8 GeV/c are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.  相似文献   
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34.
We study a class of supersymmetric spinning particle models derived from the radial quantization of stationary, spherically symmetric black holes of four dimensional \({{\mathcal N} = 2}\) supergravities. By virtue of the c-map, these spinning particles move in quaternionic Kähler manifolds. Their spinning degrees of freedom describe mini-superspace-reduced supergravity fermions. We quantize these models using BRST detour complex technology. The construction of a nilpotent BRST charge is achieved by using local (worldline) supersymmetry ghosts to generate special holonomy transformations. (An interesting byproduct of the construction is a novel Dirac operator on the superghost extended Hilbert space.) The resulting quantized models are gauge invariant field theories with fields equaling sections of special quaternionic vector bundles. They underly and generalize the quaternionic version of Dolbeault cohomology discovered by Baston. In fact, Baston’s complex is related to the BPS sector of the models we write down. Our results rely on a calculus of operators on quaternionic Kähler manifolds that follows from BRST machinery, and although directly motivated by black hole physics, can be broadly applied to any model relying on quaternionic geometry.  相似文献   
35.
Inhibition of tumor necrosis factor-alpha converting enzyme (TACE) is a widespread objective in the search for disease modifying agents to combat rheumatoid arthritis and other autoimmune diseases. Until recently, most of the inhibitors in the literature have shown concomitant activity against the related matrix metalloproteinases (MMPs), producing undesired side effects. Here we describe the successful search for a TACE selectivity mechanism. We built a homology model based on the crystal structure of the related snake venom protein atrolysin. Comparison of the model with crystal structures of MMPs suggested a uniquely shaped S1' pocket that might be exploited for selectivity. A novel gamma-lactam scaffold was used to explore the activity profile of P1' sidechains, resulting in highly selective compounds consistent with this hypothesis. Transferability of the hypothesis was then demonstrated with five other distinct scaffolds.  相似文献   
36.
Dispersion media formed by anisotropically polarizable particles suspended in nonconducting viscous fluid are considered. The particle anisotropy is set by a freezing-in unit vector; the particle shape is assumed to be close to spherical. A complete hydrodynamic model of such a medium is constructed. The expression for the free energy of a system is derived, and the laws governing the polarization of a dispersion medium and the relaxation of its anisotropy are revealed. The dependence of the effective viscosity of dispersion medium on the strength of an electric field during the flow in plane capillaries is determined.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 293–298.Original Russian Text Copyright © 2005 by Vasil’eva, Cherney.  相似文献   
37.
We report the first observations of the first harmonic (directed flow, v(1)) and the fourth harmonic (v(4)), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v(2)) generated at RHIC. From the correlation of v(2) with v(1) it is determined that v(2) is positive, or in-plane. The integrated v(4) is about a factor of 10 smaller than v(2). For the sixth (v(6)) and eighth (v(8)) harmonics upper limits on the magnitudes are reported.  相似文献   
38.
The paper presents two different methods to calculate the current density along silicone rubber (SiR) insulator surface under salt-fog testing conditions. The first method which is based on field theory approach uses the commercial software COMSOL® to compute the current density. The conductivity of the contamination layer used in the calculations was extracted from the measured equivalent salt deposit density (ESDD) separately for different regions of the insulator surfaces. The second method is based on circuit theory approach. The insulator surface was divided into different sections for resistance calculations to account for different contamination levels. Rankings based on the calculated current densities based on segmentation of the insulator surface for ESDD measurements match with those extracted from measured leakage currents.  相似文献   
39.
The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at √s=200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of pT≥5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high pT.  相似文献   
40.
This paper reports on measurements of thermally stimulated depolarization current (TSDC) that is applied to characterize changes in the large motors and generators enamelled wires that have been exposed to aging under steep-front pulse voltage waveforms. The thermoelectrets are prepared at various polarizing fields, EP, and measurements of TSDC are carried out both as a function of time and temperature over the range of 23–200 °C. In addition, various TSDC parameters such as activation energy, ?a, characteristic relaxation time, τ and the released charge, Q during the relaxation process have been determined by applying initial rise method. The experimental results for TSDC spectra of wire specimens have shown that the total stored charge in the insulation bulk increases significantly, as the number of insulation layers increases on the wire. The reason for such a higher concentration of trapped charges is more likely due to the presence of a broad distribution of the traps, which are occupied by the injected charges.  相似文献   
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