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11.
K.V. Avramov 《Journal of sound and vibration》2009,322(3):476-489
An iterative loop combining nonlinear modes and the Rauscher method is suggested for analyzing finite degree-of-freedom nonlinear mechanical systems with parametric excitation. This method is applied to an analysis of the parametric vibration of beams. 相似文献
12.
Structure and electronic properties of hollow‐caged C60 fullerene‐derived (MN4)nC6(10 − n) (M = Zn,Mg, Fe,n = 1−6) complexes
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Vladimir A. Pomogaev Pavel V. Avramov Alex A. Kuzubov Victor Ya. Artyukhov 《International journal of quantum chemistry》2015,115(4):239-244
Unique hollow‐caged (MN4)nC6(10 ? n) (M = Zn, Mg, Fe, n = 1?6) complexes designed by introduction of n porphyrinoid fragments in C60 fullerene structure were proposed and the atomic and electronic structures were calculated using LC‐DFT MPWB95 and M06 potentials and 6‐311G(d)/6‐31G(d) basis sets. The complexes were optimized using various symmetric configurations from the highest Oh to the lowest C1 point groups in different spin states from S = 0 (singlet) to S = 7 (quindectet) for M = Fe to define energetically preferable atomic and electronic structures. Several metastable complexes were determined and the key role of the metal ions in stabilization of the atomic structure of the complexes was revealed. For Fe6N24C24, the minimum energy was reported for C2h, D2h, and D4h symmetry of pentet state S = 2, so the complex can be regarded as unique molecular magnet. It was found that the metal partial density of states determine the nature of HOMO and LUMO levels making the clusters promising catalysts. © 2014 Wiley Periodicals, Inc. 相似文献
13.
Nonlinear vibrations of cylindrical panels with complex base are analyzed. The Donnell-Mushtari-Vlasov equations with respect
to displacements are used to study vibrations of shallow shell with geometrical nonlinearity. R-function method is applied to satisfy the panel boundary conditions. The Rayleigh-Ritz method is used to obtain the linear
vibrations eigenmodes, which contain R-function. The nonlinear vibrations of panel are expanded by using these eigenmodes. The harmonic balance method and nonlinear
normal modes are used to study the free nonlinear vibrations. 相似文献
14.
The nonlinear parametric vibrations of cylindrical shell are described by the Donnell–Mushtari–Vlasov equations. The motions
are represented as a mode expansion. Discretization is performed using the Bubnov–Galerkin method. The describing-function
method is used to study traveling waves and nonlinear normal modes in systems with and without dissipation 相似文献
15.
M. L. Avramov Ivić S. D. Petrović F. Vonmoos D. Z. Mijin P. M. Zivković K. M. Drljević 《Russian Journal of Electrochemistry》2008,44(8):931-936
The aim of the present study was to examine the behavior of commercial clarithromycin, Clathrocyn®, comparing to the results previously obtained using pure clarithromycin under the same experimental conditions. The study was performed by cyclic linear sweep voltammetry and the bulk of electrolyte was analyzed by FTIR spectroscopy and HPLC. At gold electrode, in the range of ?1.2 V to 1.0 V vs. SCE in 0.05 M NaHCO3, the electrochemical determination of pure clarithromycin was previously defined by four anodic and one cathodic reproductive peaks, and commercial clarithromycin is defined by reproductive one anodic peak which appears from 0.60 to 0.80 V vs. SCE. Previously, FTIR analysis of the bulk electrolyte showed the apparent changes in pure clarithromycin molecule structure: in the ester bond of the lactone and in ethers and acetal bonds. FTIR analysis of the bulk electrolyte also showed changes in the molecule structure in commercial-tablets form of clarithromycin: indicating disappearance of lactone structure and changes of carbonyl group at position 9. 相似文献
16.
I. Avramov 《Journal of Non》2008,354(45-46):4959-4961
Crystallization in undercooled melts is accompanied by development of stress energy, due to the difference in volume of the new system as compared to the ambient phase. Therefore, the growth rate decreases with time. Here, the non-stationary differential equation is solved, accounting for the production of energy of stress deformation as well as for its reduction caused by relaxation. In this way the growth rate and the dependence of crystal size on time are obtained. The change of the growth rate is significant when new formed phase has composition different from the ambient phase, so that particles, creating the new phase can move much faster the main molecules of the matrix. A steady state is determined by the condition that the rate of stress energy production is equal the rate of stress energy consumption. The degree to which the stationary growth rate Ust is reduced as compared to the initial growth rate Umax is controlled mainly by the ratio of the self-diffusion coefficient of the building units to the diffusion coefficient of the building units creating the new phase. A clear break in the size versus time dependence of the growing crystal is seen. 相似文献
17.
External electric field effect on electronic properties and charge transfer in CoI2/NiI2 spinterface
Iuliia Melchakova Evgenia A. Kovaleva Natalia S. Mikhaleva Felix N. Tomilin Sergey G. Ovchinnikov Alexander A. Kuzubov Paul Avramov 《International journal of quantum chemistry》2020,120(3):e26092
Electronic structure and spin-related properties of CoI2/NiI2 heterostructure were studied by means of density functional theory. It was shown that the electronic structure at the Fermi level can be characterized by a band gap. The effect of the external electric field on charge transfer and electronic properties of the CoI2/NiI2 interface was investigated, and it was found that band gap width depends on the strength of the applied electric field, switching its nature from semiconducting to a half-metallic one. An easy control of the electronic properties and promising spin-polarized nature of the CoI2/NiI2 spinterface allows the heterostructure to be used in spin-related applications. 相似文献
18.
The mechanism of interaction of low-energy atoms and ions of light elements (H, H+, He, Li, the kinetic energy of the particles 2-40 eV) with C6H6, C6F12, C60, and C60F48 molecules was studied by ab initio MD simulations and quantum-chemical calculations. It was shown that starting from 6 A from the carbon skeleton for the "C6H6 + proton" and "C60 + proton" systems, the electronic charge transfer from the aromatic molecule to H+ occurs with a probability close to 1. The process transforms the H+ to a hydrogen atom and the neutral C6H6 and C60 molecules to cation radicals. The mechanism of interaction of low-energy protons with C6F12 and C60F48 molecules has a substantially different character and can be considered qualitatively as the interaction between a neutral molecule and a point charge. The Coulomb perturbation of the system arising from the interaction of the uncompensated proton charge with the Mulliken charges of fluorine atoms results in an inversion of the energies of the electronic states localized on the proton and on the C6F12 and C60F48 molecules and makes the electronic charge transfer energetically unfavorable. On the different levels of theory, the barriers of the proton penetration for the C6F12 and C60F48 molecules are from two to four times lower than those for the corresponding parent systems (C6H6 and C60). The penetration barriers of the He atom and Li+ ion depend mainly on the effective radii of the bombarding particles. The theoretical penetration and escaped barriers for the "Li+ + C60" process qualitatively explain the experimental conditions of synthesis of the Li@C60 complex. 相似文献
19.
L. Popov G. Mihailova I. Hristova P. Dimitrova R. Tzibranski V. Avramov I. Naidenov B. Stoenelova 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):49-64
The method for the determination of 90Sr which employs sodium hydroxide for the separation of strontium from calcium was further improved introducing the use of
elevated temperatures. The results from 11-year study of background activity concentrations of 90Sr in different environmental objects in 100 km zone around Kozloduy Nuclear Power Plant (Bulgaria) are presented as an application
of the analytical method. The measured mean values are as follows: air precipitation − 0.0015±0.0009 Bq(m2.d), tap water − 0.0017±0.0012 Bq/L, soil − 1.90±1.26 Bq/kg, grass − 1.54±0.80 Bq/kg, milk − 0.023±0.012 Bq/L and for the Danube
river: water − 0.0046±0.0026 Bq/L, bottom sediments − 0.64±0.60 Bq/kg, algae − 1.99±1.56 Bq/kg. The calculated transfer coefficients
(soil-grass) are in the range of 0.33–0.84. Between 2 and 5 times reduction in actual background activities of 90Sr is observed compared to 1972–1974. 相似文献
20.
In a melt with the base mol% composition 25Na2O-15B2O3-60SiO2, doped with chromium and manganese, a redox reaction takes place during cooling the melt. This reaction was studied using high temperature UV-vis spectroscopy. Above 600 °C, the reaction is in equilibrium and shifted during cooling to the Cr3+ and Mn3+ species. At temperatures between 500 and 600 °C, the kinetics of the redox reaction is decisive and the cooling rate plays an important part. At temperatures < 500 °C, the reaction is frozen in. The smaller the cooling rate, the smaller is the Cr6+ concentration and the lower is the fictive redox temperature.The kinetics of the reaction was described by a differential equation assuming Arrhenian behaviour. The equation was numerically solved and fictive temperatures were calculated. These temperatures depended on cooling rate similar to Bartenev equation. Activation energies calculated hereof were around 38 kJ?mol−1 larger than those inserted into the kinetic equation. The experimentally determined activation energy is 565 kJ?mol−1, a value much larger than the activation energies of diffusion of the polyvalent elements. The rate determining step in the case of the Cr3+/Cr6+/Mn2+/Mn3+ system is the electron transfer reaction, because a notable structural rearrangement is necessary during the course of the electron transfer reaction (Cr3+ and Cr6+ occur in octahedral and tetrahedral coordination, respectively). The latter leads to a large inner reorganisation energy and to an activation energy similar to that of the viscous flow. In the case of the redox reaction between copper and arsenic, the activation energy is much smaller (210 kJ?mol−1), because here the coordination numbers do not change during the course of the redox reaction. 相似文献