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71.
Induced charge-density oscillations at noble metal surfaces caused by an external static impurity are studied within linear response theory. The calculation takes into account such properties of realistic surface electronic structure as an energy gap for three-dimensional (3D) bulk electrons and a s − pz surface state that forms two-dimensional (2D) electron system. It is demonstrated that the coexistence of these 2D and 3D electron systems has profound impact on the induced charge-density in the surface region. Thus, the oscillations with the 1/R2 decay as a function of lateral distance, R, are established in both electron systems with characteristic chess-board-like structure. Additionally, the charge-density penetrates into the solid at a finite angle with respect to the surface normal in contrast to that in jellium model. The origin of both these findings is investigated. 相似文献
72.
73.
The dependence of the quality of calculation of the geometric parameters and frequencies of normal vibrations on the choice of the theoretical method and the basis set of Gaussian functions has been investigated within the framework of four approximations (DFT/B3LYP, HF, MP2, MP3), using benzene and s-triazine molecules as an example. It has been shown that the molecular parameters calculated using the basis set without polarization functions within the framework of any of the above theoretical methods agree poorly with the experimental data. It has been concluded that the use of the basis set 6-31G(d) within the framework of these methods with allowance for the electron correlation for calculating the geometric parameters and frequencies of normal vibrations of polyatomic cyclic compounds is most optimum in terms of the relation between the expenditure of time and the quality of the calculation. The coefficients of linear scaling of frequencies have been obtained by the DFT/B3LYP method for 22 basis sets that were tested on porphin, pyrrole, indene, and pyridine molecules. Atypically large errors in determining the frequencies of some benzene and s-triazine vibrations have been obtained in a number of quantum-mechanical calculations with large basis sets. The changes in the force field for these cases have been investigated with the example of the benzene molecule. 相似文献
74.
I. A. Nechaev A. V. Dubovik V. I. Simakov V. S. Demidenko 《Physics of the Solid State》1997,39(5):716-717
Using a method based on incorporating statistics into the theory of multiple scattering via the distribution function of atoms
on lattices, the electronic structure of the intermetallic Co3Ti is calculated for both complete atomic order and complete disorder. An unusual feature of the electronic structure of this
intermetallic when it is disordered in the solid state is identified. Possible consequences of this behavior are analyzed.
Fiz. Tverd. Tela (St. Petersburg) 39, 809–810 (May 1996) 相似文献
75.
We investigate numerically and analytically the statistics of Markov chains on so-called braid (B
n
) and locally free (ℒℱ
n
) groups. Namely, we compute the mean length 〈μ〉 and the variance 〈μ2〉−〈μ〉2 of the shortest word which remains after applying of all group relations to the randomly generatedN-letter word (Markov chain). We express the conjecture (numerically justified) that the mean value 〈μ〉 for the random walk
on the groupB
n
(n≫1) coincides with high accuracy with the same value for the random walk on the “locally free group weth errors” if the number
of errors is of order of 20%. 相似文献
76.
V. N. Strel’nikov V. Yu. Senichev A. I. Slobodinyuk A. V. Savchuk E. R. Volkova M. A. Makarova A. I. Nechaev S. F. Krasnosel’skikh K. O. Ukhin 《Russian Journal of Applied Chemistry》2018,91(3):463-468
New polytetraurethane diepoxides were prepared from oligo(tetramethylene oxide)diols of various molecular masses, various diisocyanates, and glycidol. High-strength frost-resistant cold-curable elastic compounds were prepared on their basis. The use of aminoethylpiperazine as a curing agent allows the cured materials to be prepared in 24 h at room temperature. The elastomers based on isophorone diisocyanate exhibit higher mechanical and thermal characteristics than those based on 2,4-toluene diisocyanate, which is due to higher degree of microphase segregation of soft and hard blocks of elastomers based in isophorone diisocyanate. 相似文献
77.
G. N. Ten V. V. Nechaev V. I. Berezin V. I. Baranov 《Journal of Structural Chemistry》1997,38(2):268-276
The vibrational structure of the absorption spectra of the first two π-π* singlet transitions of adenine is calculated in
the Franck-Condon approximation including Herzberg-Teller interactions. The effect of excitation-induced changes in molecular
angles on the intensities of the vibrational components is estimated. Structural models of the adenine molecule in the excited
states are constructed. The theoretical and absorption spectra of the first π-π* transition are compared. The results of the
electronic structure calculations of adenine by different CNDO/S methods are discussed.
Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 2, pp. 334–344, March–April, 1997. 相似文献
78.
79.
Kristavchuk O. V. Sohatsky A. S. Kozlovskiy V. I. Skoi V. V. Kuklin A. I. Trofimov V. V. Sleptsov V. V. Nechaev A. N. Apel’ P. Yu. 《Colloid Journal》2021,83(4):448-460
Colloid Journal - This work is devoted to studying the structural and morphological properties of a silver colloidal solution obtained by the method of electrical-spark discharge in distilled... 相似文献
80.
A. V. Mikhalev A. A. Nechaev A. V. Prudnikov M. S. Staroverov A. S. Vydrin 《Journal of Mathematical Sciences》2008,149(2):1157-1169
The authors investigate semirings of cyclic types from the algebraic point of view. To simplify and facilitate the analysis,
the local Fourier transform of these semirings is introduced. The authors describe zero divisors, nilpotent elements, invertible
elements, idempotents, and the Jacobson radical.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 12, No. 2, pp. 175–192, 2006. 相似文献