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M. A. Ivanov V. Ya. Mitrofanov A. Ya. Fishman 《Journal of Experimental and Theoretical Physics》1997,84(3):531-539
We study the energy spectrum and some properties of various quadrupole centers (magnetic impurities or magnetic impurity complexes
that are symmetric with respect to the magnetic sublattices of the antiferromagnet). We allow for the effect of spin-phonon
coupling on the quadrupole splitting parameter and show that such coupling can lead to a considerable decrease in the value
of this parameter and even change its sign. We investigate the behavior of quadrupole centers with an orbitally degenerate
ground state and of quadrupole impurity complexes formed by mixed-valence ions. We demonstrate that such centers may greatly
affect the resonant, magnetic, and thermodynamic properties of antiferromagnets. Finally, we analyze the existing experimental
data and show that several new effects can be observed in systems with such centers (in particular, a magnetic analog of the
Jahn-Teller effect and a strong magnetoelectric effect).
Zh. éksp. Teor. Fiz. 111, 964–978 (March 1997) 相似文献
55.
Wieslaw Wiczk Peggy S. Eis Mayer N. Fishman Michael L. Johnson Joseph R. Lakowicz 《Journal of fluorescence》1991,1(4):273-286
The end-to-end distance distribution of a flexible molecule was recovered from steady-state fluorescence energy transfer measurements using the method suggested by Cantor and Pechukas (Proc. Natl. Acad. Sci. USA
68, 2099–2101, 1971). In this method, the Förster distance (R
0) is varied by attaching different donor-acceptor (D-A) pairs to the flexible linker of interest. Distance distributions are then recovered from energy transfer efficiency measurements on the set of D-A pairs with differentR
0 values. Thirteen D-A pair compounds were synthesized withR
0 values ranging from 6 to 32 Å. Each compound contained a tryptamine donor linked by an alkyl chain (10 carbons) to 1 of 13 acceptors. Using these compounds, we have experimentally confirmed the Cantor and Pechukas method for recovering distance distributions. The measured transfer efficiencies, as a function ofR
0, were fit to the transfer efficiencies predicted for both Gaussian and skewed Gaussian distance distributions. The data support the existence of a skewed Gaussian distribution, and we believe that this is the first experimental observation of an asymmetric distribution for a flexible molecule using fluorescence resonance energy transfer measurements. Finally, the experimentally recovered distance distribution was found to be in good agreement with the distribution predicted from the rotational isomeric state model of Flory (Statistical Mechanics of Chain Molecules, John Wiley & Sons, New York, 1969, Chaps. 1, 3, and 5) but not with the predicted distribution for a freely rotating or freely jointed chain. 相似文献
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Nonlinear dynamics of a Heisenberg ferromagnet 总被引:1,自引:0,他引:1
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Herrebout WA Gatin A Everaert GP Fishman AI van der Veken BJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(7):1431-1444
The formation of weak molecular complexes of cyclopentene with HCl and BF3, dissolved in liquid argon is investigated using infrared spectroscopy. Evidence is found for the formation of 1:1 complexes in which the Lewis acid under study binds to the CC double bond. At higher concentrations of HCl, weak absorption bands due to 1:2 species are also observed. From spectra recorded at different temperatures between 92 and 127 K, the complexation enthalpies for CP.HCl and CP.BF3 are determined to be -9.5(3) and -16.1(9) kJ mol-1, while for CP.(HCl)2 a value of -17.0(6) kJ mol-1 is obtained. For the 1:1 and 1:2 complexes, structural and spectral information is obtained from ab initio calculations at the MP2/6-31+G(d) level. Using free energy perturbation Monte Carlo simulations to calculate the solvation enthalpies and statistical thermodynamics to account for zero-point vibrational and thermal contributions, the complexation energies for CP.HCl and CP.(HCl)2 are estimated from the experimental complexation enthalpies to be -17.4(14) and -34.0(20) kJ mol-1, while the value for CP.BF3 was derived to be -23.4(22) kJ mol-1. The experimental complexation energies are compared with the theoretical values derived from the MP2/6-31+G(d) potential energy surfaces and with single point energies calculated at the MP2/6-311++G(3df,2pd) level. 相似文献
60.
Tyugaev M. D. Kharitonov A. V. Gazizov A. R. Fishman A. I. Salakhov M. Kh. Dedkova A. A. Alekseev A. M. Shelaev A. V. Kharintsev S. S. 《JETP Letters》2019,110(12):766-770
JETP Letters - The effects of enhancement of stimulated Raman scattering in titanium oxynitride (TiON) nanofilms are considered. The mechanism of giant amplification of a Stokes wave is based on,... 相似文献