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排序方式: 共有80条查询结果,搜索用时 31 毫秒
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.
Bharathi Avula Babu L. Tekwani Narayan D. Chaurasiya NP Dhammika Nanayakkara Yan‐Hong Wang Shabana I. Khan Vijender R. Adelli Rajnish Sahu Mahmoud A. Elsohly James D. McChesney Ikhlas A. Khan Larry A. Walker 《Journal of mass spectrometry : JMS》2013,48(2):276-285
Therapeutic efficiency and hemolytic toxicity of primaquine (PQ), the only drug available for radical cure of relapsing vivax malaria are believed to be mediated by its metabolites. However, identification of these metabolites has remained a major challenge apparently due to low quantities and their reactive nature. Drug candidates labeled with stable isotopes afford convenient tools for tracking drug‐derived metabolites in complex matrices by liquid chromatography‐tandem mass spectrometry (LC‐MS‐MS) and filtering for masses with twin peaks attributable to the label. This study was undertaken to identify metabolites of PQ from an in vitro incubation of a 1:1 w/w mixture of 13C6‐PQ/PQ with primary human hepatocytes. Acquity ultra‐performance LC (UHPLC) was integrated with QTOF‐MS to combine the efficiency of separation with high sensitivity, selectivity of detection and accurate mass determination. UHPLC retention time, twin mass peaks with difference of 6 (originating from 13C6‐PQ/PQ), and MS‐MS fragmentation pattern were used for phenotyping. Besides carboxy‐PQ (cPQ), formed by oxidative deamination of PQ to an aldehyde and subsequent oxidation, several other metabolites were identified: including PQ alcohol, predictably generated by oxidative deamination of PQ to an aldehyde and subsequent reduction, its acetate and the alcohol's glucuronide conjugate. Trace amounts of quinone‐imine metabolites of PQ and cPQ were also detected which may be generated by hydroxylation of the PQ/cPQ quinoline ring at the 5‐position and subsequent oxidation. These findings shed additional light on the human hepatic metabolism of PQ, and the method can be applied for identification of reactive PQ metabolites generated in vivo in preclinical and clinical studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
Ioan Paraschiv Alistair Tomkinson Marcel Giesbers Ernst J. R. Sudh?lter Han Zuilhof Antonius T. M. Marcelis 《Liquid crystals》2013,40(9):1029-1038
The synthesis and thermotropic properties are reported for a series of hexaalkoxytriphenylenes that contain an amide, urea or thiourea group in one of their alkoxy tails. The intermolecular hydrogen bonding abilities of these molecules have a disturbing influence on the formation and stability of the columnar liquid crystalline phases. The stronger the hydrogen bonding the more the liquid crystallinity is suppressed, probably due to disturbance of the π–π stacking of the triphenylene discs. As a direct result, urea‐ and amide‐containing triphenylene derivatives are not liquid crystalline, but several thiourea derivatives show hexagonal columnar mesophases. 相似文献
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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