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71.
Wagdi G. Habashi Julien Dompierre Yves Bourgault Djaffar Ait‐Ali‐Yahia Michel Fortin Marie‐Gabrielle Vallet 《国际流体数值方法杂志》2000,32(6):725-744
The present paper is the lead article in a three‐part series on anisotropic mesh adaptation and its applications to structured and unstructured meshes. A flexible approach is proposed and tested on two‐dimensional, inviscid and viscous, finite volume and finite element flow solvers, over a wide range of speeds. The directional properties of an interpolation‐based error estimate, extracted from the Hessian of the solution, are used to control the size and orientation of mesh edges. The approach is encapsulated into an edge‐based anisotropic mesh optimization methodology (MOM), which uses a judicious sequence of four local operations: refinement, coarsening, edge swapping and point movement, to equi‐distribute the error estimate along all edges, without any recourse to remeshing. The mesh adaptation convergence of the MOM loop is carefully studied for a wide variety of test cases. The mesh optimization generic coupling of MOM with finite volume and finite element flow solvers is shown to yield the same final mesh no matter what the starting point is. It is also shown that on such optimized meshes, the need for computational fluid dynamics (CFD) stabilization artifices, such as upwinding or artificial viscosity, are drastically reduced, if not altogether eliminated, in most well‐posed formulations. These two conclusions can be considered significant steps towards mesh‐independent and solver‐independent CFD. The structure of the three‐part series is thus, 1, general principles; 2, methodology and applications to structured and unstructured grids; 3, applications to three‐dimensional flows. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
72.
73.
Hossni Ziyat My Youssef Ait Itto Mustapha Ait Ali Abdellah Karim Abdelkhalek Riahi Jean‐Claude Daran 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o90-o93
The two new gem‐dihalogenocyclopropanes (1′S,3R)‐3‐(2′,2′‐dichloro‐1′‐methylcyclopropyl)‐6‐oxoheptanoic acid, C11H16Cl2O3, (2), and (1′S,3R)‐3‐(2′,2′‐dibromo‐1′‐methylcyclopropyl)‐6‐oxoheptanoic acid, C11H16Br2O3, (3), are isostructural. Both present two stereogenic centers at C1′ and C3. The absolute configuration was determined by X‐ray methods. The cyclopropyl rings are unsymmetrical, the shortest bond being distal with respect to the alkyl‐substituted C atom. 相似文献
74.
75.
Badia Ait Allal Larbi El Firdoussi Smail Allaoud Abdallah Karim Yves Castanet Andr Mortreux 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):177-184
The allylic oxidation of α-pinene 1 was investigated using various catalytic systems. By a proper choice of the latter, the reaction can be directed toward the selective synthesis of verbenol 2 or verbenone 3. High yield into verbenone was achieved under mild conditions with copper salts as catalysts and t-butyl hydroperoxide (TBHP) as oxidant. On the other hand, when Pd(acac)2 was used with hydrogen peroxide, verbenol was obtained as the main product. 相似文献
76.
Microtubule‐Binding R3 Fragment from Tau Self‐Assembles into Giant Multistranded Amyloid Ribbons
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Dr. Jozef Adamcik Dr. Antoni Sánchez‐Ferrer Nadine Ait‐Bouziad Dr. Nicholas P. Reynolds Prof. Dr. Hilal A. Lashuel Prof. Dr. Raffaele Mezzenga 《Angewandte Chemie (International ed. in English)》2016,55(2):618-622
Tau protein and its fragments self‐assemble into amyloid fibrils in the presence of polyanions, such as heparin. By combining microscopy, scattering, and spectroscopy techniques, we studied the aggregation of the 26‐mer Tau‐derived peptide alone, Tau306–327, the third repeat fragment (R3) of the microtubule‐binding domain. We show that: i) the sole Tau306–327 can self‐assemble into amyloid fibrils without the need of aggregation‐promoting polyanions; ii) the resulting structures consist of surprisingly large, well‐ordered 2D laminated flat ribbons, with a log‐normal distribution of the lateral width, reaching the unprecedented lateral size of 350 nm and/or 45 individual protofilaments, that is, the largest amyloid laminated structures ever observed for Tau or any other amyloidogenic sequence. Our results provide insight into the molecular determinants of Tau aggregation and open new perspectives in the understanding of the assembly of amyloid fibrils and β‐sheet‐based biomaterials. 相似文献
77.
In this short paper, in order to price occupation-time options, such as (double-barrier) step options and quantile options, we derive various joint distributions of a mixed-exponential jump-diffusion process and its occupation times of intervals. 相似文献
78.
Mohamed Ait Ouahra 《Comptes Rendus Mathematique》2005,340(7):519-524
We give some limit theorems of certain additive functionals for symmetric stable process of index in anisotropic Besov space. These results generalize those obtained by Eisenbaum (1997) and by Csaki et al. (2002). To cite this article: M. Ait Ouahra, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
79.
Lomello-Tafin M Chaou AA Morfin F Caps V Rousset JL 《Chemical communications (Cambridge, England)》2005,(3):388-390
The intimate mixture of a skeletal gold structure with ZrO2 nanoparticles obtained simply by oxidation of Au(0.5)Zr(0.5) alloy at room temperature turns out to be an efficient catalyst for the selective oxidation of CO in the presence of hydrogen. 相似文献
80.
H. Ait Ahsaine M. Zbair Z. Anfar Y. Naciri R. El haouti N. El Alem M. Ezahri 《Materials Today Chemistry》2018
Almond shell agricultural biomass was used to prepare high surface area activated carbon using potassium hydroxide as activating agent. The activated carbon (AC) was characterized using X-Ray photoelectron spectroscopy, X-Ray diffraction, Thermogravimetric and differential thermal analyses, Scanning electron microscopy, Fourier transform infrared, Brunauer–Emmett–Teller surface area and Raman spectroscopy. The AC was found to have a high surface area of 2054 m2 g?1. The influence of various key parameters was evaluated on the adsorption process including contact time, adsorbent dose and solution pH. Isotherm data were modeled using Langmuir and Freundlich models. Langmuir isotherm model presented the best fit to experimental data suggesting homogeneous distribution of adsorption sites. The adsorbent demonstrated high monolayer adsorption capacity of 833.33 and 625.0 mg/g for Methylene Blue and Crystal Violet, respectively. The efficiency of the adsorption process was linked to the micro-mesoporous structure and to the availability of the surface adsorption sites. Response surface methodology was used to optimize the removal efficiency from aqueous solution. 相似文献