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21.
L. Jendrassik L. Dziobek M. Halász Margret B. Strauss W. E. Wilins H. D. Jones F. Breh O. H. Gaebler R. Truszkowski R. L. Zwemer F. Takács K. B. Thomson W. C. Lee O. S. Duffendack F. H. Wiley J. S. Owens C. Bomskov W. S. Hoffman G. Barkan Eva Berger Rudolf Schmid E. Starkenstein H. Weden W. Lintzel M. Sahyun R. F. Felkamp J. Dabrowski L. Marchlewski J. Peregud J. Kusmina Ph. Fischer H. Straller B. Behrens H. Taeger Frida Schmitt H. J. Morris H. O. Calvery K. Hinsberg M. Kiese G. Bertrand L. Silberstein H. de Waal 《Analytical and bioanalytical chemistry》1939,117(11-12):452-464
22.
Using temperature-variable scanning tunneling microscopy, we studied the coalescence of vacancy islands on Cu(0 0 1) in ultra-high vacuum. From the temperature dependence of the relaxation of merged vacancy islands to the equilibrium shape we obtain an activation energy of the island coalescence process of 0.76 eV. From that value we deduce an activation energy for the atomic hopping coefficient of EΓh=0.89 eV. Comparing our result with previous STM data on step fluctuations with dominant diffusion along straight step segments (EΓh=0.68 eV; [M. Giesen, S. Dieluweit, J. Mol. Catal. A: Chem. 216 (2004) 263]) and step fluctuations with kink crossing (EΓh=0.9 eV; [M. Giesen-Seibert, F. Schmitz, R. Jentjens, H. Ibach, Surf. Sci. 329 (1995) 47]), we conclude that there is a large extra barrier for diffusion of atoms across kinks on Cu(0 0 1) of the order of 0.23 eV. This is the first direct experimental evidence for the existence of a large kink Ehrlich-Schwoebel barrier on Cu(0 0 1). 相似文献
23.
Margret Höft 《Algebra Universalis》1987,24(3):283-288
The main result is a fixed point theorem for compositions of chain faithful multifunctions (Corollary 2.3). The theorem is then applied to get sufficient conditions for the fixed point property of the product of two partially ordered sets.Presented by R. P. Dilworth. 相似文献
24.
25.
By employing numerical solutions of the Poisson–Boltzmann equation we have studied the interface capacitance of flat electrodes with stripes of different potentials of zero charge ?pzc. The results depend on the ratio of the width of the stripes l to the dielectric screening length in the electrolyte, the Debye length dDebye, as well as on the difference Δ?pzc in relation kBT/e. As expected, the capacitance of a striped surface has its minimum at the mean potential of the surface if l/dDebye << 1 and displays two minima if l/dDebye >> 1. An unexpected result is that for Δ?pzc ? 0.2V, the transition between the two extreme cases does not occur when l ? dDebye, but rather when l > 10dDebye. As a consequence, a single minimum in the capacitance is observed for dilute electrolytes even for 100 nm wide stripes. The capacitance at the minimum is however higher than for homogeneous surfaces. Furthermore, the potential at the minimum deviates significantly from the potential of zero mean charge on the surface if l > 3dDebye and Δ?pzc is larger than about 4kBT/e. The capacitance of stepped, partially reconstructed Au(11n) surfaces is discussed as an example. Consequences for Parsons–Zobel-plots of the capacitances of inhomogeneous surfaces are likewise discussed. 相似文献
26.
Feilberg KL Gruber-Stadler M Johnson MS Mühlhäuser M Nielsen CJ 《The journal of physical chemistry. A》2008,112(44):11099-11114
A relative rate experiment is carried out for six isotopologues of methanol and their reactions with OH and Cl radicals. The reaction rates of CH2DOH, CHD2OH, CD3OH, (13)CH3OH, and CH3(18)OH with Cl and OH radicals are measured by long-path FTIR spectroscopy relative to CH3OH at 298 +/- 2 K and 1013 +/- 10 mbar. The OH source in the reaction chamber is photolysis of ozone to produce O((1)D) in the presence of a large excess of molecular hydrogen: O((1)D) + H2 --> OH + H. Cl is produced by the photolysis of Cl2. The FTIR spectra are fitted using a nonlinear least-squares spectral fitting method with measured high-resolution infrared spectra as references. The relative reaction rates defined as alpha = k(light)/k(heavy) are determined to be: k(OH + CH3OH)/k(OH + (13)CH3OH) = 1.031 +/- 0.020, k(OH + CH3OH)/k(OH + CH3(18)OH) = 1.017 +/- 0.012, k(OH + CH3OH)/k(OH + CH2DOH) = 1.119 +/- 0.045, k(OH + CH3OH)/k(OH + CHD2OH) = 1.326 +/- 0.021 and k(OH + CH3OH)/k(OH + CD3OH) = 2.566 +/- 0.042, k(Cl + CH3OH)/k(Cl + (13)CH3OH) = 1.055 +/- 0.016, k(Cl + CH3OH)/k(Cl + CH3(18)OH) = 1.025 +/- 0.022, k(Cl + CH3OH)/k(Cl + CH2DOH) = 1.162 +/- 0.022 and k(Cl + CH3OH)/k(Cl + CHD2OH) = 1.536 +/- 0.060, and k(Cl + CH3OH)/k(Cl + CD3OH) = 3.011 +/- 0.059. The errors represent 2sigma from the statistical analyses and do not include possible systematic errors. Ground-state potential energy hypersurfaces of the reactions were investigated in quantum chemistry calculations at the CCSD(T) level of theory with an extrapolated basis set. The (2)H, (13)C, and (18)O kinetic isotope effects of the OH and Cl reactions with CH3OH were further investigated using canonical variational transition state theory with small curvature tunneling and compared to experimental measurements as well as to those observed in CH4 and several other substituted methane species. 相似文献
27.
Inorganic chemistry and IONiC: an online community bringing cutting-edge research into the classroom
Jamieson ER Eppley HJ Geselbracht MJ Johnson AR Reisner BA Smith SR Stewart JL Watson LA Williams BS 《Inorganic chemistry》2011,50(13):5849-5854
This Viewpoint highlights creative ways that members of the Interactive Online Network of Inorganic Chemists (IONiC) are using journal articles from Inorganic Chemistry to engage undergraduate students in the classroom. We provide information about specific educational materials and networking features available free of charge to the inorganic community on IONiC's web home, the Virtual Inorganic Pedagogical Electronic Resource (VIPEr, www.ionicviper.org ) and describe the benefits of joining this community. 相似文献
28.
Manuel Pfanzelt Pierre Kubiak Ute H?rmann Ute Kaiser Margret Wohlfahrt-Mehrens 《Ionics》2009,15(6):657-663
Several carbon-coated anatase TiO2 samples have been prepared by impregnation with lactose as carbon precursor and annealed at different temperatures (650 and
700 °C). X-ray diffraction was carried out to study the anatase to rutile phase transition and to evaluate the crystallite
size. Scanning electron microscopy was utilized to evaluate the morphology, and transmission electron microscopy was used
to show the distribution and nature of the carbon coating. The galvanostatic measurements and cyclic voltammetry revealed
better kinetics, cycling stability, and high rate capacity for the carbon-coated materials when compared with the noncoated
ones. 相似文献
29.
Periodic convective instability has been observed in a biphasic system during the complexation reaction of alkali picrate and dicyclohexano-18-crown-6 which undergoes mass transfer from the hexane phase into the aqueous phase. The convection was visualized by means of precipitated crystals that are formed in both phases by the complexation reaction. The fluid motion was observed with an optical microscope and further analyzed with the particle image velocimetry (PIV) technique. The partition at the extraction of cesium into the organic phase was followed by means of the radioactive isotope (137)Cs. The type of the hydrodynamic instability is governed by the alkali metal expressed via its stability constants for the complex formed. More stable complexes trigger a higher precipitation, thereby favoring a Raleigh-Taylor instability. Complexes with a lower stability constant induce Marangoni cells which show a pulsating character in a cubic container. Depending on the confinement of the experiment cell the fluid motion can also follow a back-and-forth movement. Possible mechanisms for the occurring oscillations are discussed. 相似文献
30.
Marinkovic M Gruber-Stadler M Nicovich JM Soller R Mülhäuser M Wine PH Bache-Andreassen L Nielsen CJ 《The journal of physical chemistry. A》2008,112(48):12416-12429
A laser flash photolysis-resonance fluorescence technique has been employed to determine absolute rate coefficients for the CH3F + Cl reaction in N2 bath gas in the temperature range of 200-700 K and pressure range of 33-133 hPa. The data were fitted to a modified Arrhenius expression k(T) = 1.14 x 10(-12) x (T/298)2.26 exp{-313/T}. The OH and Cl reaction rates of (13)CH3F and CD3F have been measured by long-path FTIR spectroscopy relative to CH3F at 298 +/- 2 K and 1013 +/- 10 hPa in purified air. The FTIR spectra were fitted using a nonlinear least-squares spectral fitting method including line data from the HITRAN database and measured infrared spectra as references. The relative reaction rates defined by alpha = k(light)/k(heavy) were determined to be k(OH+CH3F)/k(OH+CD3F) = 4.067 +/- 0.018, k(OH+CH3F)/k(OH+(13)CH3F) = 1.067 +/- 0.006, k(Cl+CH3F)/k(Cl+CD3F) = 5.11 +/- 0.07, and k(Cl+CH3F)/k(Cl+(13)CH3F) = 1.016 +/- 0.006. The carbon-13 and deuterium kinetic isotope effects in the OH and Cl reactions of CH3F have been further investigated by quantum chemistry methods and variational transition state theory. 相似文献