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1.
M. J. Tomkinson 《Ukrainian Mathematical Journal》1992,44(6):768-770
The major subgroups of a group G and their intersection (G) were introduced in [1] as a variation on maximal subgroups and the Frattini subgroup of G. In particular, we have proved in [1–4] a number of results of the form: if G/(G) has property X then G has property X. The property X may be that of being hypercentral or hypercyclic or of having some finiteness condition. These results, of course, require some restriction on the group G.Published in Ukrainskii Matematicheskii Zhurnal, Vol. 44, Mo. 6, pp. 853–856, June, 1992. 相似文献
2.
Keith P. Brierley Joseph Howard Clifford J. Ludman Keith Robson Thomas C. Waddington John Tomkinson 《Chemical physics letters》1978,59(3):467-471
Inelastic neutron scattering spectra of KHCO3 and CsH(NO3)2 have been obtained in the region 400 → 2400 and 400 → 2800 cm?1 respectively. The in- and out-of-phase bending vibrations of the hydrogen bonds have been observed and assigned. For CsH(NO3)2 the two bending modes are closer in frequency than in KHCO3 and they are not resolved from the antisymmetric stretch. 相似文献
3.
The crystal structures of potassium and cesium bistrifluoroacetates, KH(CF(3)COO)(2) and CsH(CF(3)COO)(2), respectively, were determined at room and cryogenic temperatures with the single crystal neutron diffraction technique. The crystals belong to the monoclinic space groups, I2a and A2a, respectively, and there is no evidence of any structural phase transition. In both crystals, trifluoroacetate entities in centrosymmetric dimers are linked by very short hydrogen bonds lying across a center of inversion. The thermal parameters provide no evidence of any double minimum potential for hydrogen bond protons. Single-minimum potentials were determined via best fitting to the inelastic neutron scattering spectral profiles of the stretching vibrations. They comprise a narrow well for the ground state and a very broad quasiharmonic well for excited states. The spread out of the wave functions of these states shows that protons are no longer confined between the oxygens. Presumably, they are attracted by the lone pairs of oxygen atoms. These potentials emphasize the covalent nature of the OO bond and the ionic character of the hydrogen bond proton. 相似文献
4.
A.B. Gardner S. Howard T.C. Waddington R.M. Richardson J. Tomkinson 《Chemical physics》1981,57(3):453-460
Incoherent quasi-elastic neutron scattering has been used to study the reorientational motions of the cyclopentadienyl rings in ferrocene, nickelocene and ruthenocene. The results for ferrocene show that the activation energy for ring rotation drops above the 164 K phase transition to 4.4 ± 0.5 kJ mol?1 (which is approximately half its low temperature value) but the rings still appear to jump between only five orientations on the observable time scale. At room temperature, the rings in nickelocene appear to behave the same as in ferrocene but in ruthenocene they reorientate much less frequently and resemble those in ferrocene below 164 K. 相似文献
5.
Jolin Tomkinson Ian J. Braid Joseph Howard Thomas C. Waddington 《Chemical physics》1982,64(1):151-157
Inelastic neutron scattering spectra (300–2500 cm?1) of KH(CHCO2)2, KD(CHCO2)2, KH(CDCO2)2 and KH(CHCO2 · CClCO2) have been obtained and the vibrations of the hydrogen bond, with the exception of ν2(OHO), assigned. This is the first assignment of these vibrations in a centrosymmetric intramolecularly hydrogen bonded complex. νas(OHO) was found to be heavily mixed and to give rise to a strong doublet in the INS spectra. 相似文献
6.
An aminocatalytic method for the formation of bisindolylalkanes is described; the reaction proceeds effectively at ambient temperature in the presence of moisture and air for both aldehyde and ketone substrates and has been applied to the one-step preparation of a series of naturally-occurring bis- and tris-indolylalkanes. 相似文献
7.
J. Tomkinson 《Pramana》2008,71(4):745-754
The role that model compounds can play in understanding the vibrational eigenvectors of molecules is discussed. Assigning
the spectra of model compounds is of particular importance and the individual-scaling approach, that has been used with isolated
molecule ab-initio calculations, is outlined. Special emphasis is given to recent work on assigning the spectra of three 5–6 heterobicyclic
systems; indole, benzimidazole and isatin.
相似文献
8.
We have used high resolution neutron vibrational spectroscopy to study the vibrations of the model compound for arene-to-metal bonding, benzene chromium tricarbonyl, and its mesityl analogue. It is shown that all previously published assignment schemes, based on optical spectroscopy alone, are wrong, and new assignments are given in agreement with ab initio calculations. 相似文献
9.
John Tomkinson 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(4):1377-1379
The title paper [1] reports ab initio calculations of the structure and molecular vibrations of 1,5-dinitronaphthalene. The calculations are unminimised, the molecular structure is wrong and the vibrational spectra are misinterpreted. These errors have been corrected and the vibrational spectra of 1,5-dinitronaphthalene have been reassigned in agreement with the optical and neutron spectroscopic data. 相似文献
10.
M. J. Tomkinson 《Ukrainian Mathematical Journal》1991,43(7-8):972-975
A splitting theorem for FC-hypercentral group G and zG-module of finite rank is obtained. According to this theorem, under certain conditions, every extension E of the zG-module A by the group G is split and all the complements to A in E are conjugate in E.Published in Ukraninskii Matematicheskii Zhurnal, Vol. 43, Nos. 7 and 8, pp. 1038–1042, July–August, 1991. 相似文献