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31.
Abdullah?M?Asiri Harry?G?Heller David?S?Hughes Michael?B?HursthouseEmail author John?Kendrick Frank?JJ?Leusen Riccardo?Montis 《Chemistry Central journal》2014,8(1):70
Background
Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed “tribochromism”. We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies.Results
A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb – which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb.Conclusions
Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice.Graphical abstract Graphical representation of the structural and colour change in the tribochromic compound (III).
32.
利用螺旋波激发等离子体化学气相沉积(LPP-CVD)技术,以甲烷和氦气为反应气体产生等离子体.通过采集到甲烷的可见光到紫外发射光谱,对甲烷等离子体进行原位诊断,发现存在CH、Ha及Hβ等碎片粒子的光辐射,同时,分析了不同入射功率、气压下CH粒子以及Hβ、Hγ的相对强度变化情况.结果表明:CH粒子的相对强度随着射频功率是先增大而后减小,随工作气压的增大而逐渐减小;随气压及功率的增加,Hβ、Hγ相对强度变化的总体趋势都是先增加而后减小的. 相似文献
33.
Mahua Das R. Ranjith C. Bittencourt S. B. Krupanidhi J. J. Pireaux S. A. Shivashankar 《Applied Physics A: Materials Science & Processing》2009,95(2):523-536
We report the fabrication of assembled nanostructures from the pre-synthesized nanocrystals building blocks through optical
means of exciton formation and dissociation. We demonstrate that Li
x
CoO2 nanocrystals assemble to an acicular architecture, upon prolonged exposure to ultraviolet–visible radiation emitted from
a 125 W mercury vapor lamp, through intermediate excitation of excitons. The results obtained in the present study clearly
show how nanocrystals of various materials with band gaps appropriate for excitations of excitons at given optical wavelengths
can be assembled to unusual nanoarchitectures through illumination with incoherent light sources. The disappearance of exciton
bands due to Li
x
CoO2 phase in the optical spectrum of the irradiated film comprising acicular structure is consistent with the proposed mechanism
of exciton dissociation in the observed light-induced assembly process. The assembly process occurs through attractive Coulomb
interactions between charged dots created upon exciton dissociation. Our work presents a new type of nanocrystal assembly
process that is driven by light and exciton directed. 相似文献
34.
J.J. Pireaux M. Chtaïb J.P. Delrue P.A. Thiry M. Liehr R. Caudano 《Surface science》1984,141(1):211-220
Tentative adsorption on clean gold (110) and (111) crystals of molecular oxygen in the pressure range 10 ?10 to 10 ?5 Torr, at a temperature varying between 100 and 800 K is reported together with the subsequent characterization of the surfaces by High Resolution Electron Energy Loss, Auger and X-ray Photoelectron Spectroscopies. It is found that oxygen does not adsorb in these UHV conditions, except when a contaminant is present on the surface. Such an interaction with a low level silicon impurity is described. 相似文献
35.
Francílio de C. Oliveira José Schneider Abner Siervo Richard Landers Ana M. G. Plepis Jean-Jacques Pireaux Ubirajara Pereira Rodrigues-Filho 《Surface and interface analysis : SIA》2002,34(1):580-582
Composites of Keggin heteropolymetalates have been prepared and characterized by SEM, XPS, 31P-magic angle spinning/nuclear magnetic resonance and differential scanning calorimetry. The phosphotungstic acid and phosphomolybdic acid form nanocomposites where the oxocluster structure is preserved and is highly dispersed over the material, probably inserted between the polymeric chains. Phosphovanadotungstic clusters suffer partial decomposition during composite formation, resulting in a biphasic microcomposite. The decomposition product, phosphotungstic acid presents surface segregation as shown by comparison of XPS and nuclear magnetic resonance results. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
36.
37.
Bobeldijk I Bouwhuis M Ireland DG de Jager CW Jans E de Jonge N Kasdorp WJ Konijn J Lapikás L van Leeuwe JJ van der Meer RL Nooren GJ Passchier E Schroevers M van der Steenhoven G Steijger JJ Theunissen JA van Uden MA de Vries H de Vries R de Witt Huberts PK Blok HP van den Brink HB Dodge GE Harakeh MN Hesselink WH Kalantar-Nayestanaki N Pellegrino A Spaltro CM Templon JA Hicks RS Kelly JJ Marchand C 《Physical review letters》1994,73(20):2684-2687
38.
39.
40.
C. Girardeaux N. Zammatteo M. Art B. Gillon J. J. Pireaux R. Caudano 《Plasmas and Polymers》1996,1(4):327-346
Amine functionalization of Poly(ethylene-terephthalate) (PET) films for covalent binding of peptides is described. Ammonia
plasma treatments have been used to graft nitrogen-containing functional groups onto the PET surface. The samples were then
analyzed by X-ray photoelectron spectroscopy (XPS) and a parametric study was performed to define the best plasma grafting
conditions. For biological tests, samples were sterilized by steam autoclaving: this induces a four to fivefold loss of the
nitrogen functional groups on the polymer surface. XPS does not differentiate easily between the various nitrogen groups present
on the surface so it is difficult to estimate the amount of surface amine groups available for direct coupling of bioactive
molecules (proteins, peptides, nucleic acids, ...). To obtain a direct measurement of the amines present, we assayed for cysteine
fixation through its carboxylic group by detection of the thiolaminoacid by XPS. We obtained cysteine fixation, showing the
presence of grafted primary amine functions on PET surface after ammonia plasma treatment. Radiochemical assays were also
made to quantify the amount of amine groups on plasma treated PET. XPS, cysteine fixation and radiochemical assays all show
the presence of amine functions on ammonia plasma treated PET. 相似文献