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11.
12.
D. L. Chizhov P. A. Slepukhin I. G. Ovchinnikova O. V. Fedorova G. L. Rusinov V. I. Filyakova V. N. Charushin 《Russian Chemical Bulletin》2010,59(11):2122-2125
O-Alkylation of 2-acetylphenols with α,ω-dichloro derivatives of oligoethylene glycols in the presence of KOH and Al2O3 in DMF gave the corresponding podands. Their condensation with ethyl trifluoroacetate afforded fluorine-containing bis(β-diketones)
with the aryl fragments linked by conformationally flexible polyether spacers. 相似文献
13.
E. Kh. Mukhamedzhanov M. V. Kovalchuk M. M. Borisov E. N. Ovchinnikova E. V. Troshkov V. E. Dmitrienko 《Crystallography Reports》2010,55(2):174-181
Purely resonant Bragg reflections 006, 5$
\bar 5
$
\bar 5
0, and 666 in a rubidium dihydrophosphate (RbH2PO4) crystal at the K edge of rubidium have been experimentally and theoretically investigated. These reflections remain forbidden when the resonant
dipole-dipole (E1E1) contribution to the resonant atomic factor is taken into account; they may be due to the dipole-quadrupole (E1E2) transitions as well as to the anisotropy atomic factor, which is caused by thermal atomic displacements (thermally induced
contribution) and/or local jumps of hydrogen atoms. A numerical simulation showed that, at room temperature (experimental
conditions), the thermally induced contribution to the “forbidden” reflections is dominant. 相似文献
14.
V. E. Dmitrienko E. N. Ovchinnikova 《Journal of Experimental and Theoretical Physics》2011,112(5):833-836
The X-ray resonant diffraction in a stishovite crystal near the K absorption edge of silicon (E
K
= 1839 eV) is studied theoretically. For such a long wavelength, the only possible Bragg reflection is the 100 reflection,
which is forbidden by the space group of the crystal. It can be excited solely due to anisotropy of the X-ray scattering amplitude.
The crystal symmetry is used to determine the polarization and azimuthal dependence of the reflection intensity. Since this
reflection is single, it can be detected upon diffraction from a powder, which substantially widens the possibilities of investigations.
The numerical calculations of the energy dependences of the forbidden reflection intensity and the absorption coefficient
demonstrate that the dipole-quadrupole, quadrupole-quadrupole, and dipole-octupole contributions to the resonant diffraction
and absorption are small and that the dipole-dipole contribution is the most important one. 相似文献
15.
M. Ya. Ovchinnikova 《Journal of Experimental and Theoretical Physics》2011,113(1):148-155
The possibility of interpreting the normal pseudogap state of cuprates as a result of the formation of spin and charge structures
is investigated for solutions of the Hubbard model of a finite 2D cluster based on the mean field method. The iterative self-consistency
procedure reduces the initial uncorrelated spin distributions to stable structures. The Fourier components of the charge and
spin distributions in such structures have peaks for characteristic incommensurate quasi-momenta depending on the doping.
It is shown that for any doping, the density of states of the system has a sharp minimum (pseudogap) at the Fermi level. This
emergence of the gap just at the Fermi level is a property typical of not only the superconducting state, but also the normal
state of spin glasses. The characteristics of the Fermi surface averaged over the implemented structures and the properties
of quasiparticles in the nodal and antinodal regions of the quasi-momentum are considered. 相似文献
16.
E. Kh. Mukhamedzhanov M. V. Kovalchuk M. M. Borisov E. N. Ovchinnikova A. P. Oreshko V. E. Dmitrienko 《Journal of Experimental and Theoretical Physics》2011,112(1):94-101
The purely resonant Bragg reflections (13, 13, 0) and (14, 0, 0) in yttrium aluminum garnet Y3Al5O12 at energies near the K absorption edge of yttrium have been studied experimentally and theoretically. The anisotropic tensor atomic factor of yttrium
corresponding to dipole-dipole resonance transitions depends on three independent parameters changing with energy. The intensities
of the reflections (14, 0, 0) and (13, 13, 0) are shown to depend on the parameter difference f
1(E) − f
2(E) and the parameter f
3(E), respectively, which are attributable to distortions of the wave functions of the excited atoms and change greatly with
photon energy E. Studying various reflections has allowed one to determine the various components of the tensor atomic factor and to compare
them with the results of numerical calculations. 相似文献
17.
18.
S. N. Ovchinnikova A. I. Maslii V. V. Boldyrev 《Russian Journal of Electrochemistry》2006,42(8):882-888
Methods of quartz microgravimetry (in solutions containing no copper ions) and stripping voltammetry (in copper-containing solutions) are used to study the process of anodic dissolution of thin deposits of pure Co and Ni and deposits of these metals with inclusion of copper in the potential region of copper deposition. It is shown that, under these conditions, Ni practically does not dissolve in either the sulfate or chloride-containing electrolytes, whereas Co dissolves in sulfate electrolytes at a rate that is dependent on the potential and increases with its shift into the positive region. Stability of ternary CoNiCu deposits is examined and it is demonstrated that additionally inserting Ni in the composition of a magnetic CoCu layer facilitates suppression of selective dissolution of Co. 相似文献
19.
The effect of a radial temperature gradient on stability of steady-state flow of a viscous liquid between two solid concentric cylinders both rotating in the same direction is considered. The linear stability problem is considered in the Boussinesq approximation. Sufficient stability and instability conditions for the flow relative to rotationally symmetric perturbation are obtained. Neutral curves are computed for a wide range of problem parameters. 相似文献
20.
O. V. Fedorova M. S. Valova Yu. A. Titova I. G. Ovchinnikova A. N. Grishakov M. A. Uimin A. A. Mysik A. E. Ermakov G. L. Rusinov V. N. Charushin 《Kinetics and Catalysis》2011,52(2):226-233
The effect of nanosized metal oxides on the regio- and stereoselectivity of the multicomponent Biginelli reaction and the
reaction mechanism under conditions of heterogeneous catalysis were studied. It was found that the considerable activation
of reagents occurred on the surface of metal nanooxides. The Biginelli reaction occurred by two mechanisms: a carbocationic
mechanism took place along with the generally accepted mechanism (through the N-acyliminium ion). Nanosized metal oxides in the presence of chiral inductors increased the regio- and stereoselectivity of
the Biginelli reaction. 相似文献