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51.
Trevor J. Dines Louise D. MacGregor Colin H. Rochester 《Journal of Raman spectroscopy : JRS》2007,38(7):832-840
The protonation of Disperse Orange 25 (DO25) in aqueous solution, and upon adsorption on oxide surfaces, was studied by resonance Raman (RR) spectroscopy. The neutral and protonated forms of DO25 were modelled by DFT calculations of the isolated molecules in the gas phase at the B3‐LYP/DZ level, enabling calculation of the vibrational spectra of these species, together with vibrational assignments. RR spectra show that DO25 is physisorbed on the SiO2 surface, but its adsorption on SiO2 Al2O3 or H‐mordenite results in protonation. This observation indicates the presence of Brønsted acidic sites on these oxide surfaces with pKa values ⩽2.5. RR studies of the adsorption of DO25 can therefore provide useful information on the nature of surface acidity on oxides, which is complementary to that obtained from other probe molecules. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
52.
Andrew P. Mendham Rex A. Palmer Brian S. Potter Trevor J. Dines Martin J. Snowden Robert Withnall Babur Z. Chowdhry 《Journal of Raman spectroscopy : JRS》2010,41(3):288-302
Cyclo(L ‐Glu‐L ‐Glu) has been crystallised in two different polymorphic forms. Both polymorphs are monoclinic, but form 1 is in space group P21 and form 2 is in space group C2. Raman scattering and FT‐IR spectroscopic studies have been conducted for the N,O‐protonated and deuterated derivatives. Raman spectra of orientated single crystals, solid‐state and aqueous solution samples have also been recorded. The different hydrogen‐bonding patterns for the two polymorphs have the greatest effect on vibrational modes with N H and CO stretching character. DFT (B3‐LYP/cc‐pVDZ) calculations of the isolated cyclo(L ‐Glu‐L ‐Glu) molecule predict that the minimum energy structure, assuming C2 symmetry, has a boat conformation for the diketopiperazine ring with the two L ‐Glu side chains being folded above the ring. The calculated geometry is in good agreement with the X‐ray crystallographic structures for both polymorphs. Normal coordinate analysis has facilitated the band assignments for the experimental vibrational spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
53.
Mixed elliptic boundary value problems are characterised by conditions which have a jump along an interface of codimension 1 on the boundary. We study such problems in weighted edge spaces and show the Fredholm property and the existence of parametrices under additional conditions of trace and potential type on the interface. We develop a new method for computing the interface conditions in terms of the index of boundary value problems in weighted spaces on infinite cones, combined with structures from the calculus of boundary value problems on a manifold with edges. This will be illustrated by the Zaremba problem and other mixed problems for the Laplace operator. The approach itself is completely general. 相似文献
54.
A convenient route to 1,4-dithianes from ethane-1,2-disulfenyl chloride and acetylenes is presented. The reaction of this new sulfenyl halide with primary and secondary amines is also discussed. 相似文献
55.
56.
Martin B. Dines 《Journal of organometallic chemistry》1974,67(2):C55-C58
The silver salt of trifluoromethanesulfonic acid (silver(I) triflate) forms complexes with aromatics whose solid state stoichiometries involve two salt units per organic, as does the copper analog. Both show a similar preference for p-xylene among the eight carbon aromatic isomers, indicative of isomorphic structures. The two Ib systems are contrasted in their behavior as slurries with aromatics. 相似文献
57.
Klatte K Christen D Merke I Stahl W Oberhammer H 《The journal of physical chemistry. A》2005,109(37):8438-8442
CF3SiMe3 (Ruppert's reagent) has been investigated by gas phase electron diffraction, microwave spectroscopy and quantum chemical methods, deriving structural parameters and the barrier height for the methyl torsion. The bond length of the Si-CF3 bond, 1.941(3) A, is the longest Si-C bond observed so far in the gas phase. The V3 barrier for the methyl group torsion (V3= 5.71 kJ/mol) is only slightly lower than barriers determined for other trimethylsilane compounds. 相似文献
58.
59.
The resonance Raman spectra of [Et4N] [FeCl4] in nitromethane solution and of [Bu4N] [FeBr4] as a KBr disc at ≈ 80 K have been record 相似文献
60.
Andrew P. Mendham John Spencer Babur Z. Chowdhry Trevor J. Dines Muhammad Mujahid Rex A. Palmer Graham J. Tizzard Simon J. Coles 《Journal of chemical crystallography》2011,41(9):1328-1334