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61.
Eric N. Landis Svetlana Vasic William G. Davids Perrine Parrod 《Experimental Mechanics》2002,42(4):389-394
In this paper, we explore ways to couple experimental measurements with the numerical simulations of the mechanical properties
of wood. For our numerical simulations, we have adopted a lattice approach, where wood fibers or bundles of wood fibers are
modeled as discrete structural elements connected by a lattice of spring elements. Element strength and stiffness properties
are determined from bulk material properties. Damage is represented by broken lattice elements, which cause both stiffness
and strength degradation. The modeling approach was applied to small specimens of spruce subjected to transverse uniaxial
tension, and mode I transverse splitting. The model was found to be good at predicting the load-deformation response of both
notched and unnotched specimens, including the post-peak softening response. In addition, the damage patterns predicted by
the model are consistent with those observed in the experiments. 相似文献
62.
Sami Abou Rich Perrine Leroy Thierry Dufour Nimer Wehbe Laurent Houssiau François Reniers 《Surface and interface analysis : SIA》2014,46(3):164-174
The in‐depth oxygen diffusion into a low density polyethylene film is performed in the post‐discharge of an atmospheric plasma torch, supplied in argon as carrier gas and with or without oxygen as reactive gas. The chemical and structural properties of the polymer surface and bulk are studied in terms of plasma parameters (treatment time, power, and reactive gas flow rate). A good correlation between XPS and Fourier transform infrared spectroscopy analyses is demonstrated. The penetration depth of oxygen into the bulk of the polymer is investigated by angle resolved‐XPS and time‐of‐flight SIMS. It is shown that, depending on the plasma conditions, oxygen could penetrate up to 20–40 nm into the low density polyethylene during the atmospheric plasma treatment. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
63.
64.
Thill A Maillet P Guiose B Spalla O Belloni L Chaurand P Auffan M Olivi L Rose J 《Journal of the American Chemical Society》2012,134(8):3780-3786
It is known that silicon can be successfully replaced by germanium atoms in the synthesis of imogolite nanotubes, leading to shorter and larger AlGe nanotubes. Beside the change in morphology, two characteristics of the AlGe nanotube synthesis were recently discovered. AlGe imogolite nanotubes can be synthesized at much higher concentrations than AlSi imogolite. AlGe imogolite exists in the form of both single-walled (SW) and double-walled (DW) nanotubes, whereas DW AlSi imogolites have never been observed. In this article, we give details on the physicochemical control over the SW or DW AlGe imogolite structure. For some conditions, an almost 100% yield of SW or DW nanotubes is demonstrated. We propose a model for the formation of SW or DW AlGe imogolite, which also explains why DW AlSi imogolites or higher wall numbers for AlGe imogolite are not likely to be formed. 相似文献
65.
Chabert Jérôme Echterhoff Siegfried Nest Ryszard 《Publications Mathématiques de L'IHéS》2003,97(1):239-278
Let G be a locally compact group with cocompact connected component. We prove that the assembly map from the topological K-theory of G to the K-theory of the reduced C*-algebra of G is an isomorphism. The same is shown for the groups of k-rational points of any linear algebraic group over a local field k of characteristic zero. Dedicated to the memory of Peter Slodowy 相似文献
66.
Jean-Luc Chabert Scott T. Chapman William W. Smith 《Proceedings of the American Mathematical Society》1998,126(11):3151-3159
Let be an integral domain with quotient field and . We investigate the relationship between the Skolem and completely integrally closed properties in the ring of integer-valued polynomials
Among other things, we show for the case and that the following are equivalent: (1) is strongly Skolem, (2) is completely integrally closed, and (3) for every .
67.
68.
Auffan M Rose J Proux O Borschneck D Masion A Chaurand P Hazemann JL Chaneac C Jolivet JP Wiesner MR Geen AV Bottero JY 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3215-3222
When normalized per unit of surface area, the quantity of arsenic adsorbed at the maghemite surface remains constant for particles between 300 and 20 nm. However, nanoparticles smaller than 20 nm exhibit enhanced adsorption capacity. The origin of this observed size-dependence for adsorption or "nano effect" is unclear. Arsenic was chosen as a probe of the surface structure to explore adsorption mechanisms occurring at the surface of maghemite nanoparticles (6 nm). Two factors contributing to the enhanced reactivity of nanoscale maghemites were determined. The first is related to a size-dependent structural modification of the surface of particles and the decrease of the occupancy of the tetrahedral site that leaves vacant, highly reactive adsorption sites. In particular, there is a site localized in a six-membered iron octahedral ring. This site is the only one for which an oxidation of As(III) occurs. The second factor relates to the thermodynamics of a decrease of the surface free energy. The high density of As adsorbed at the saturation of the surface can be related to crystal growth. 相似文献
69.
Previously we have demonstrated that several structural features are crucial for the functionality of molecular field-effect transistors. The effect of additional structural aspects of molecular wires is explored. These include the type of, the thiol binding location on, and the chemical substitutions of a conjugated system. Pentacene, porphyrin, and the Tour-Reed devices are utilized as model systems. The thiol binding location is shown to have a varied effect on the transmission of a system depending on the molecular orbitals involved. Substitution by electron withdrawing and donating groups is illustrated to have a substantial effect on the transmission of single molecule devices. The substitution effect is either a simple energy shifting effect or a more complicated resonance effect, and can be used to effectively tune the electronic behavior of a single molecule field effect transistor. 相似文献
70.
Properties of interface in unidirectional composite materials can be studied “in situ” by dynamic mechanical measurements: analysis of relaxations and appearance of damage in shearing. This methodology is applied on composite materials based on an epoxy matrix and carbon fibers with different surface treatments (untreated, oxidized and sized). Mechanical spectroscopy displays modifications of epoxy network with the fiber treatment and evidence for an interphase in the case of sized fibers. Dynamic shearing test clearly shows large differences of behavior with the surface treatments. 相似文献