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31.
Ralf Hilger Hans-Peter Merckens Arne Lüchow Heinz Kleindienst 《International journal of quantum chemistry》1998,66(1):25-30
Extensive Hylleraas–CI calculations for the lowest Po states of 4He were performed. The dependence of the variational energy values Eκ on the mass parameter κ given by κ=m/m is discussed. Furthermore, lower bounds to Eκ were calculated using variance minimization. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 25–30, 1998 相似文献
32.
Viktor Bezugly Pawel Wielgus Miroslav Kohout Frank R. Wagner 《Journal of computational chemistry》2010,31(7):1504-1519
Electron localizability indicators based on the parallel‐spin electron pair density (ELI–D) and the antiparallel‐spin electron pair density (ELIA) are studied for the correlated ground‐state wavefunctions of Li2, Be2, B2, and C2 diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li2, B2, and C2 the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
33.
L. Künne 《International journal of quantum chemistry》1999,74(1):55-58
Relations between the two quantum chemical methods density functional theory (DFT) and configuration interaction (CI) are studied. As a result a new expression of the density functional based on CI approximation is presented. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 55–58, 1999 相似文献
34.
A cumulative selection procedure for choosing configuration functions for inclusion in CI calculations is described. The objective of the method is to obtain equal energy loss, relative to unselected calculations, for different states and different regions of the potential surface. Results obtained from calculations on the BH molecule indicate an overall advantage in comparison to the threshold selection procedure, particularly with regard to molecular geometry changes. 相似文献
35.
Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules
Neji Khelifi Riadh Dardouri Omar Marzook Al-Dossary Brahim Oujia 《Journal of Russian Laser Research》2009,30(2):172-186
Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states
of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in 1,3Σ, 1,3Π, and 1,3Δ symmetries are presented. Adiabatic results are also reported for 2Σ, 2Π, and 2Δ electronic states of the molecular ion LiNa+ dissociating into Li (2s, 2p, 3s, and 3p) + Na+ and Li+ + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and Na (1s22s22p6) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and
LiNa+ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between
electronic states of 2Σ and 2Π symmetries is related to the charge transfer process between the two ionic systems Li+Na and LiNa+. 相似文献
36.
A flexible correlation group table (CGT) method for the relativistic configuration interaction wavefunctions 总被引:1,自引:0,他引:1
Hang Tan Muzhen Liao Yan Wang Guoshi Wu K. Balasubramanian 《Journal of mathematical chemistry》2000,28(1-3):213-239
A generalized correlation group table (CGT) method is described for the relativistic configuration interaction (RCI) wavefunctions of molecules containing heavy atoms. In this method first four keywords are defined and two properties are discussed in terms of spectroscopic states and double group theory. These definitions and properties are then used to summarize six principles to stipulate the relationship among relativistic states, nonrelativistic states, as well as RCI configurations. The definitions, properties, and principles comprise the generalized CGT method, which facilitates the classification and assignment of the RCI wavefunctions, and thus, provide a general technique for complex systems containing several open shells. Finally, the techniques are exemplified with a few computational models. 相似文献
37.
We present in this paper a modification of the selection procedure, within the CIPSI algorithm, specifically intended for
the calculation of one-electron properties. In this new procedure the determinants are selected following their contribution
to a certain one-electron property. As test cases we report the calculation of the electric dipole of carbon monoxide and
of the hyperfine coupling constants of the CH3 radical.
Received: 20 August 2000 / Accepted: 2 October 2000 / Published online: 21 December 2000 相似文献
38.
UV photoelectron spectra of hypoxanthine, xanthine, and caffeine, up to 20 eV, were calculated and compared with the experimental spectra reported in literature. The calculations were performed using a novel version of the quantum mechanical symmetry-adapted cluster/configuration interaction (SAC-CI) method termed, direct SAC-CI. The Duning/Huzinaga valance double-zeta D95+(d,p) Gaussian basis set was also employed with this method. The ionization energies and intensities were calculated, and the corresponding spectral bands were assigned. Natural bonding orbital (NBO) calculations were employed for better spectral band assignment. The calculated ionization energies and intensities reasonably produced the experimental photoelectron spectra. 相似文献
39.
Barbituric acid (BA) is a very important kind of compound in biological chemistry and medicine. It can be applied in abirritative medicine and antioxidants.1 It is an important sort of raw material for organic synthe-sis.2 It predicts the important reactive mechanism for organic synthesis.3 Some investigations for NLO prop-erties of a series of BA derivatives have been reported by Feng and coworkers in the view of theory.4,5 The Schiff base has extensive application in the fields of organi… 相似文献
40.
Yoshihiro Osamura 《Theoretical chemistry accounts》1989,76(2):113-124
Summary A new analytic second derivative expression of the electronic energy is derived for full configuration interaction (CI) wave functions. This formula is shown to be free from the derivative terms of both CI and MO coefficients. The second-order relationships between CI and MO coefficients for full CI wave functions are also presented. 相似文献