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1.
New radiative transfer theory is developed for stochastically inhomogeneous scattering media. The three-dimensional shapes and large scale (compared to the mean free path) structures of the media are modeled by stochastic interfaces separating regions of different scattering properties. The small scale fluctuations are characterized by a pair-correlation function. The radiative transfer equation is extended to include individual scattering and propagation probabilities of a ray for each subregion as well as the probability for a ray to cross the interface between two subregions. The propagation probability is found to depend on the entire preceding path of the ray; the present formulation accounts for the two previous scatterings. A new adding/doubling algorithm is developed to solve this problem numerically. Transmission through a cloud layer and backward scattering seem to be particularly sensitive to inhomogeneities. 相似文献
2.
Jouni I. Peltoniemi 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,108(2):180-196
Light scattering from particulate medium is simulated using the Monte Carlo ray-tracing technique. The medium is modelled as a randomly packed medium of ellipsoidal grains with stochastically rough surfaces, with an optional thin coating. Optical properties are modelled using a wavelength-dependent complex refractive index and taking Fresnelian reflections and refractions from the interfaces. The size and shape of the grains are assumed to be large and smooth enough for geometric optics to apply reasonably well.The ray-tracing technique uses parallel, weighted rays for computing simultaneously over a wide wavelength spectrum and a small roughness range, and scaling to obtain a large range of sizes and absorbities simultaneously. Polarisation is fully accounted for. The multiobservation technique is effectively used at each scattering point. The scattering from thinner sample layers is also received as a subresult.Simulations are run for a set of model samples to study the effects and sensitivities regarding the values of certain parameters. It has been found that the size and composition of the grains affect the scattering in a unique and invertible way. The shape of the grain causes similar significant effects that must certainly be taken into account if any accuracy is required, although inverting for the shape is difficult without further constraints. The packing density has a small but observable effect. Polarisation can be used to study the composition of low-albedo objects. 相似文献
3.
Jouni PARKKONEN Vesa RUUSKA 《数学学报(英文版)》2007,23(1):89-94
A conjecture of Ehrenpreis states that any two compact Riemann surfaces of genus at least two have finite degree unbranched holomorphic covers that are arbitrarily close to each other in moduli space. Here we prove a weaker result where certain branched covers associated with arithmetic Riemann surfaces are allowed, and investigate the connection of our result with the original conjecture. 相似文献
4.
Sauli Vuoti Matti Haukka Jouni Pursiainen 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):m601-m603
The dichloromethane solvates of the isomers tetrakis(μ‐1,3‐benzothiazole‐2‐thiolato)‐κ4N:S;κ4S:N‐dipalladium(II)(Pd—Pd), (I), and tetrakis(μ‐1,3‐benzothiazole‐2‐thiolato)‐κ6N:S;κ2S:N‐dipalladium(II)(Pd—Pd), (II), both [Pd2(C7H4NS2)4]·CH2Cl2, have been synthesized in the presence of (o‐isopropylphenyl)diphenylphosphane and (o‐methylphenyl)diphenylphosphane. Both isomers form a lantern‐type structure, where isomer (I) displays a regular and symmetric coordination and isomer (II) an asymmetric and distorted structure. In (I), sitting on an centre of inversion, two 1,3‐benzothiazole‐2‐thiolate units are bonded by a Pd—N bond to one Pd atom and by a Pd—S bond to the other Pd atom, and the other two benzothiazolethiolate units are bonded to the same Pd atoms by, respectively, a Pd—S and a Pd—N bond. In (II), three benzothiazolethiolate units are bonded by a Pd—N bond to one Pd atom and by a Pd—S bond to the other Pd atom, and the fourth benzothiazolethiolate unit is bonded to the same Pd atoms by, respectively, a Pd—S bond and a Pd—N bond. 相似文献
5.
Tero Piippanen Jouko Jaatinen Jouni Tummavuori 《Analytical and bioanalytical chemistry》1997,357(4):405-410
Inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied as a rapid routine method for the analysis
of cemented tungsten carbides. Chromium, cobalt, iron, nickel, niobium, tantalum, titanium and zinc were selected as major,
minor and trace constituents in the material investigated. In the first step, the sample was treated with hydrochloric and
orthophosphoric acid. The second step consisted of the simultaneous addition of hydrofluoric and nitric acids. Cemented tungsten
carbides dissolved completely, leaving only minor quantities of carbon in the solution. Multiple linear regression proved
to be very effective in the search for interfering elements. Using simple acid based standards, all the elements investigated
could be determined individually from the complicated matrix using an appropriate method of calculation. The method described
was successfully applied to real type commercial samples. The advantages of the ICP-AES method in comparison with the XRF-method
are discussed.
Received: 15 February 1996/Revised: 22 April 1996/Accepted: 2 May 1996 相似文献
6.
The phonon properties and thermodynamics of four crystalline cellulose allomorphs, I, I, II, and III, have been investigated using dispersion-corrected density functional theory (DFT). In line with experimental findings, the free energy differences between the studied cellulose allomorphs are small, less than 1 kJ/mol per atom. The calculated specific heat at constant volume () has been compared with the available experimental data in the temperature range 10–300 K. Quasiharmonic approximation has been employed to study thermodynamics and specific heat at constant pressure (). For the studied temperature range of 10–400 K, the specific heat of all cellulose allomorphs shows very similar behavior. The calculated and experimental specific heat agree well at low temperatures below 100 K, but the deviation between theory and experiment increases with temperature. This may be due to increasing phonon anharmonicity as the temperature increases. 相似文献
7.
H. Penttilä D. Gorelov V. -V. Elomaa T. Eronen U. Hager J. Hakala A. Jokinen A. Kankainen P. Karvonen I. D. Moore J. Parkkonen K. Peräjärvi I. Pohjalainen S. Rahaman S. Rinta-Antila J. Rissanen V. A. Rubchenya A. Saastamoinen V. Simutkin T. Sonoda C. Weber A. Voss J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2016,52(4):104
8.
In a complete simply connected Riemannian manifold X of pinched negative curvature, we give a sharp criterion for a subset C to be the ??-neighbourhood of some convex subset of X, in terms of the extrinsic curvatures of the boundary of C. 相似文献
9.
10.