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11.
A V Gubskaya O A Boryak M V Kosevich V S Shelkovsky 《Rapid communications in mass spectrometry : RCM》1992,6(8):531-535
The present paper discusses non-traditional possibilities of the applications of mass spectrometry to the detection and study of differences in crystal polymorphic forms. The parameter of fast-atom bombardment which is sensitive to different polymorphs, namely the rate of the formation of cluster ions of an analyte with the glycerol matrix, was chosen for study. Using as an example the analysis of four different samples of cortisone acetate, varying in their polymorphic forms, treatment procedures, and dispersion of the crystalline powder, it is shown that the relative intensity of the cluster ion [MGH]+ (where M represents the analyte and G a molecule of glycerol) differs for two of the polymorphic forms and is the same for one of these forms, whether it is obtained by recrystallization from chloroform or by cryogrinding. Analysis of the time dependences of the [MGH]+ ion intensity allowed us to detect finer effects in the samples, associated with cryogrinding, namely differences in solubility and presumably, mechanoactivation. 相似文献
12.
V. S. Shelkovskii M. V. Kosevich V. V. Chagovets O. A. Boryak V. V. Orlov S. V. Snegir’ I. V. Shmigol’ V. A. Pokrovskii 《Journal of Analytical Chemistry》2010,65(13):1388-1396
An approach is proposed for the estimation of the contribution of field ionization (FI) to the mechanism of dye ion formation
under the conditions of laser desorption/ionization (LDI) from a nanostructurized graphite surface. As test systems, rough
graphite layers with dyes, e.g., imidazophenazine derivatives applied to them were chosen; these ensure FI in a strong electric
field. The dyes form three neutral precursors upon reduction and various types of ions in different ionization methods. It
was found that the mass distribution within the group of peaks formed by the initial dye molecule and the products of its
reduction in the positive ion mode upon LDI from a rough graphite surface is shifted to lower masses by one atomic mass unit
in comparison to the distribution recorded for LDI from a smooth metal support. The analysis of plausible pathways of ion
formation has shown that such a shift may be due to the superposition of ions formed by the FI mechanism on a graphite substrate
with a number of ions formed by protonation in LDI with no dependence on the support type. In the negative ion mode, the registration
of LDI dye spectra succeeded only if the graphite substrates used favored negative FI and electron emission enhanced by the
field. 相似文献
13.
14.
A. M. Kosevich 《Journal of Experimental and Theoretical Physics》1999,88(1):168-173
The shattering of a wave (quasiparticle) with a dispersion curve consisting of two quadratic branches by a planar defect is
discussed. The analog of such a process is the scattering of a similar wave (quasiparticle) in a one-dimensional system by
a point defect. It is shown that even when the defect is passive, i.e., has no internal degrees of freedom, scattering may
become resonant. The physical explanation of this effect is that a wave with a lower-lying spectrum scattered by the defect
is in resonance with a localized (bound) state emerging because of the interaction between the defect and a wave with a higher-lying
spectrum.
Zh. éksp. Teor. Fiz. 115, 306–317 (January 1999) 相似文献
15.
Magnetic solitons in a one-dimensional ferromagnet with easy-plane anisotropy are considered. Algebraic solitons are discussed and the conditions of existence of such solitons are investigated. 相似文献
16.
17.
The coherent Hall effect denotes the transient Hall response of impulsively excited coherent charge-carrier wave packets in a solid. We report the first experimental study of this phenomenon (i) using a semiconductor superlattice in crossed electric and magnetic fields as a model for three-dimensional materials and (ii) employing a contactless optoelectronic technique to probe the transient currents. Two field regimes with distinctly different oscillatory wave packet dynamics are found, separated from each other by a transition region where all oscillations are suppressed. 相似文献
18.
Kosevich MV Chagovets VV Shmigol IV Snegir SV Boryak OA Orlov VV Shelkovsky VS Pokrovskiy VA Gomory A 《Journal of mass spectrometry : JMS》2008,43(10):1402-1412
Redox behaviour of four imidazophenazine dye derivatives under mass spectrometric conditions of matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI) from metal and graphite surface, electrospray, low temperature secondary ion mass spectrometry (LT SIMS) and fast atom bombardment (FAB) was studied and distinctions in the reduction-dependent spectral patterns were analyzed from the point of view of different quantities of protons and electrons available for reduction in different techniques. The reduction products [M + 2H](+*), [M + 3H](+) and M(-*), [M + H](-) were observed in the positive and negative ion modes, respectively, which permitted to suggest independent occurrence of reduction and protonation/deprotonation processes. LDI from graphite substrate was the only technique that allowed us to obtain abundant negative ions of all dye derivatives. The yield of field ionization (FI) or field desorption (FD) mechanism to ion formation under LDI from rough graphite surface has been addressed. The sensitivity of reduction of the dyes to variation of reduction-initiating agents confirms high redox activity of the dyes essential for their functioning in natural and artificial systems. 相似文献
19.
20.
Fast growth of grains with homogeneous composition and 13 orientation was observed in Pd/Ag single-crystal thin films during annealing at 400°C. It was found that nucleuses of these orientation are contained in an initial structure. The grain growth obeys the mechanism of diffusion-induced grain boundary migration and the migration velocity was >-10-7 m/s. The assumption was made that an elementary act of fast grain boundary migration is a transition of an atomic group determined by a Coinsidence Site Lattice, and the reconstruction occurs as correlated displacements of n atoms resulting in the transition of m atoms from one grain to another. A free activation energy of such a process and velocity of the special grain boundary were estimated in the frames of the model. 相似文献