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71.
Finite permutation groups of rank 3 such that both the subconstituents have rank 3 are classified. This is equivalent to classifying all finite undirected graphs with the following property: every isomorphism between subgraphs on at most three vertices is a restriction of an automorphism of the graph. 相似文献
72.
Boron is available in the form of metal borates, especially of sodium and calcium, in nature[1]. The production of boron compounds has substantially increased recently due to increasing uses of these compounds in nuclear technology, in rocket engines as f… 相似文献
73.
The classification of absorption bands in the acene series (, p, β-bands) was first based on the annellation effect and later on the polarization of the bands with regard to the molecular axes (Lb,La,Bb,Ba-bands). Both give the same result since annelation axes and molecular axes coincide. This is not so in the pyrene series. Annellation axes and molecular axes are different and it is shown that the classification of bands can be based only on the annellation effects. Moreover, the electronic asymmetry of the pyrene system is demonstrated by a striking asymmetric annellation effect. A number of higher annellated pyrenes have been synthesized:
1·-benzonaphtho-(2″·3″ :6·7)-pyrene, dinaphto-(2'·3 :1·2)-(2″·3″:6·7)-pyrene, 1·14,4·5-dibenzo-pentacene, 5·,15·16-dibenzohexacene, 6·7,16·17-dibenzoheptacene, 1·16,4·5-dibenzohexacene and 7·8,17·18-dibenzo-octacene. 相似文献
74.
Anthony P. O’Mullane Sara E. Dale Thomas M. Day Neil R. Wilson Julie V. Macpherson Patrick R. Unwin 《Journal of Solid State Electrochemistry》2006,10(10):792-807
Polyaniline (PANI) thin films modified with platinum nanoparticles have been prepared by several methods, characterised and assessed in terms of electrocatalytic properties. These composite materials have been prepared by the in situ reduction of a platinum salt (K2PtCl4) by PANI, in a variety of solvents, resulting in the formation of platinum nanoparticles and clusters of different sizes. The further deposition of platinum clusters at spin cast thin films of PANI/Pt composites from a neutral aqueous solution of K2PtCl4 has also been demonstrated. Thin-film electrodes prepared from these materials have been investigated for their electrocatalytic activity by studying hydrazine oxidation and dichromate reduction. The properties of the composite materials have been determined using UV–visible spectroscopy, atomic force microscopy and transmission electron microscopy. The nature of the material formed is strongly dependent on the solvent used to dissolve PANI, the method of preparation of the PANI/Pt solution and the composition of the spin cast thin film before subsequent deposition of platinum from the aqueous solution of K2PtCl4.Dedicated to Professor Dr. Alan Bond on the occasion of his 60th birthday. 相似文献
75.
Dobson PS Bindley LA Macpherson JV Unwin PR 《Langmuir : the ACS journal of surfaces and colloids》2005,21(4):1255-1260
A combined atomic force microscopy (AFM)-inverted optical microscopy technique has been used to image the surface of calcite single microcrystals, with dimensions of 10-20 microm, at high resolution. The microcrystals were grown on a glass substrate using the Kitano method, a process that involves the outgassing of carbon dioxide from a saturated solution of calcium carbonate. The resulting increase in the supersaturation of the solution, with respect to calcium carbonate, induces crystallization. It is demonstrated, for the first time, that calcite microcrystals formed in this way exhibit a single spiral growth hillock on the (104) surface, as evidenced by a spiral step pattern, indicating that growth occurs at steps arising from an individual screw dislocation. The subsequent reactivity of these crystals under Kitano conditions has been followed in situ using AFM imaging. 相似文献
76.
The lattice dynamics of InAs under variable hydrostatic pressures is investigated on the basis of an ‘11-parameter’ rigid-ion model (RIM). The calculated phonon dispersion curves are in satisfactory agreement with the neutron scattering data (available for the TA modes only) measured at room temperature and atmospheric pressure. The one- and two-phonon densities of states functions and mode Gruneisen parameters have been computed at two arbitrary hydrostatic pressures. The effect of high pressure on the phonon dispersion curves is shown to lead to a typical ‘softening’ in the transverse acoustic modes and eventually to a phase trnasformation of the compound. 相似文献
77.
Sofia Goia Matthew A. P. Turner Jack M. Woolley Michael D. Horbury Alexandra J. Borrill Joshua J. Tully Samuel J. Cobb Michael Staniforth Nicholas D. M. Hine Adam Burriss Julie V. Macpherson Ben R. Robinson Vasilios G. Stavros 《Chemical science》2022,13(2):486
Many photoactivated processes involve a change in oxidation state during the reaction pathway and formation of highly reactive photoactivated species. Isolating these reactive species and studying their early-stage femtosecond to nanosecond (fs–ns) photodynamics can be challenging. Here we introduce a combined ultrafast transient absorption-spectroelectrochemistry (TA-SEC) approach using freestanding boron doped diamond (BDD) mesh electrodes, which also extends the time domain of conventional spectrochemical measurements. The BDD electrodes offer a wide solvent window, low background currents, and a tuneable mesh size which minimises light scattering from the electrode itself. Importantly, reactive intermediates are generated electrochemically, via oxidation/reduction of the starting stable species, enabling their dynamic interrogation using ultrafast TA-SEC, through which the early stages of the photoinduced relaxation mechanisms are elucidated. As a model system, we investigate the ultrafast spectroscopy of both anthraquinone-2-sulfonate (AQS) and its less stable counterpart, anthrahydroquinone-2-sulfonate (AH2QS). This is achieved by generating AH2QS in situ from AQS via electrochemical means, whilst simultaneously probing the associated early-stage photoinduced dynamical processes. Using this approach we unravel the relaxation mechanisms occurring in the first 2.5 ns, following absorption of ultraviolet radiation; for AQS as an extension to previous studies, and for the first time for AH2QS. AQS relaxation occurs via formation of triplet states, with some of these states interacting with the buffered solution to form a transient species within approximately 600 ps. In contrast, all AH2QS undergoes excited-state single proton transfer with the buffered solution, resulting in formation of ground state AHQS− within approximately 150 ps.A spectroelectrochemical set-up using a boron doped diamond mesh electrode is presented; from ultrafast photodynamics to steady-state, the photochemistry and photophysics of redox active species and their reactive intermediates can be investigated. 相似文献
78.
Paul V. Bernhardt Brendan P. Macpherson 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):m533-m536
The crystal structures of a pair of closely related macrocyclic cyano‐ and hydroxopentaaminecobalt(III) complexes, as their perchlorate salts, are reported. Although the two complexes, [Co(CN)(C11H27N5)](ClO4)2·H2O and [Co(OH)(C11H27N5)](ClO4)2, exhibit similar conformations, significant differences in the Co—N bond lengths arise from the influence of the sixth ligand (cyano as opposed to hydroxo). The ensuing hydrogen‐bonding patterns are also distinctly different. Disorder in the perchlorate anions was clearly resolved and this was rationalized on the basis of distinct hydrogen‐bonding motifs involving the anion O atoms and the N—H and O—H donors. 相似文献
79.
Paul V. Bernhardt Brendan P. Macpherson 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(11):m467-m470
The crystal structures of a pair of cis and trans isomers of the macrocyclic chloropentaamine title complex, as their tetrachlorozincate(II) salts, [CoCl(C11H27N5)][ZnCl4], are reported. The two distinct isomeric forms lead to significant variations in the Co—N bond lengths and, furthermore, hydrogen bonding between the complex ions is influenced by the folded (cis) or planar (trans) conformations of the coordinated ligand. 相似文献
80.
Güell AG Ebejer N Snowden ME Macpherson JV Unwin PR 《Journal of the American Chemical Society》2012,134(17):7258-7261
As a new form of carbon, graphene is attracting intense interest as an electrode material with widespread applications. In the present study, the heterogeneous electron transfer (ET) activity of graphene is investigated using scanning electrochemical cell microscopy (SECCM), which allows electrochemical currents to be mapped at high spatial resolution across a surface for correlation with the corresponding structure and properties of the graphene surface. We establish that the rate of heterogeneous ET at graphene increases systematically with the number of graphene layers, and show that the stacking in multilayers also has a subtle influence on ET kinetics. 相似文献