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111.
We show that, when subjected to microwave fields, surfactant-stabilized single-walled carbon nanotubes (SWNTs) develop polarization potentials at their extremities that readily drive electrochemical reactions. In the presence of transition metal salts with high oxidation potential (e.g., FeCl3), SWNTs drive reductive condensation to metallic nanoparticles with essentially diffusion-limited kinetics in a laboratory microwave reactor. Using HAuCl4, metallic particles and sheaths deposit regioselectively at the SWNT tips, yielding novel SWNT-metal composite nanostructures. This process is shown to activate exclusively metallic SWNTs; a degree of diameter selectivity is observed using acceptors with different oxidation potentials. The reaction mechanism is shown to involve Fowler-Nordheim field emission in solution, where electric fields concentrate at the SWNT tips (attaining approximately 10(9) V/m) due to the SWNT high aspect ratio (approximately 1000) and gradient compression in the insulating surfactant monolayer. Nanotube antenna chemistry is remarkably simple and should be useful in SWNT separation and fractionation processes, while the unusual nanostructures produced could impact nanomedicine, energy harvesting, and synthetic applications. 相似文献
112.
F. Duque L.M. Molina M.J. López A. Ma nanes J.A. Alonso 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):285-288
The electronic and atomic structure of Al13H has been studied using Density Functional Theory. Al13H has closed electronic shells. This makes the cluster very stable and suggests that it could be a candidate to form cluster
assembled solids. The interaction between two Al13H clusters was analyzed and we found that the two units preserve their identities in the dimer. A cubic-like solid phase assembled
from Al13H units was then modeled. In that solid the clusters retain much of their identity. Molecular dynamics runs show that the
structure of the assembled solid is stable at least up to 150 K. A favorable relative orientation of the clusters with respect
to their neighbors is critical for the stability of that solid.
Received 21 November 2000 相似文献
113.
F. Ungan E. Kasapoglu C. A. Duque U. Yesilgul S. ?akiroglu I. S?kmen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):89-93
We have investigated the effects of the intense laser field and nitrogen
concentration on bound state energy levels in Ga
x
In1-
x
N
y
As1-
y
N/GaAs quantum well. The results show that both intense laser field
and N-incorporation into the GaInNAs have strong influences on carrier
localization. We hope that our results can stimulate further investigations
of the related physics, as well as device applications of group-III
nitrides. 相似文献
114.
The combined effects of electron-hole correlation, hydrostatic pressure, and temperature on the third harmonic generation
in disk-shaped parabolic GaAs quantum dots are studied under the density matrix formalism and the effective mass approximation.
Two well-defined regimes are discussed: (1) the strong-confinement regime, where the Coulomb interaction between the electron
and hole is neglected and (2) the weak-confinement regime where the parabolic confinement term is neglected and the system
reaches the limit of a hydrogenic problem. The results show that the third harmonic-generation coefficient is strongly dependent
on the localization of the electron-hole pair. Also, that by using external perturbations like hydrostatic pressure or by
considering the temperature effects it is possible to induce a blue-shift and/or red-shift on the resonant peaks of the third
harmonic generation coefficient. 相似文献
115.
116.
We provide sufficient conditions for the existence of solutions to a semilinear wave equation with non-monotone nonlinearity
involving a small parameter. Our results are based on the analysis of a an operator that characterizes the projection onto
the kernel of the wave operator subject to periodic-Dirichlet boundary conditions. Such a kernel is infinite dimensional which makes standard compactness arguments inapplicable. 相似文献
117.
Davide Viterbo Marco Milanesio Ramn Poms Hernndez Chryslaine Rodríguez Tanty Ivan Cols Gonzlez Marquiza Sabln Carrazana Julio Duque Rodríguez 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(5):580-581
The title compound, 1‐(2′,3′‐dideoxy‐β‐d ‐glycero‐pent‐2‐enofuranosyl)thymine 1‐methyl‐2‐pyrrolidone solvate, C10H12N2O4·C5H9NO, is an NMPO solvate of the anti‐AIDS agent D4T. In its crystal structure, both the pyrimidine and the furanose rings are planar and approximately perpendicular [82.1 (4)°]. The value of the torsion angle defining the orientation of the thymine with respect to the joined furane, χ = ?100.8 (4)°, and that of the torsion angle giving the orientation of the hydroxyl group linked to the furane ring, γ = 52.9 (5)°, show that the glycosylic link adopts the so‐called high‐anti conformation and the 5′‐hydroxyl group is in the +sc position. The NMPO solvate is linked to the nucleoside through a fairly strong hydrogen bond. 相似文献
118.
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