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921.
This paper is concerned with a heat diffusion problem in a half-space which is motivated by the detection of material defects
using thermal measurements. This problem is solved by inverting the Laplace transform with respect to time on a contour in
the complex plane using an exponentially convergent quadrature rule. This leads to a finite number of time-independent problems,
which can be solved in parallel using boundary integral equation methods. We provide a full numerical analysis of this scheme
on compact time intervals. Our results are formulated in a way that they can easily be used for other diffusion problems in
exterior or interior domains. 相似文献
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923.
Sophie E. Gledhill Anton Zykov Thorsten Rissom Raquel Caballero Christian A. Kaufmann Christian-Herbert Fischer Martha Lux-Steiner Varvara Efimova Volker Hoffmann Steffen Oswald 《Applied Physics A: Materials Science & Processing》2011,104(1):407-413
Thin film chalcopyrite solar cells grown on light-weight, flexible steel substrates are poised to enter the photovoltaic market.
To guarantee good solar cell performance, the diffusion of iron from the steel into the CIGSe absorber material must be hindered
during layer deposition. A barrier layer is thus required to isolate the solar module from the metal substrate, both electronically
and chemically. Ideally the barrier layer would be deposited by a cheap roll-to-roll process suitable to coat flexible steel
substrates. Aluminium oxide deposited by spray pyrolysis matches the criteria. The coating is homogeneous over rough substrates
allowing comparatively thin barrier layers to be utilized. In this article, solar cell results are presented contrasting the
device performance made with a barrier layer to that without a barrier layer. Secondary Ion Mass spectrometry (SIMS) measurements
show that the spray pyrolysed barrier layer diminishes iron diffusion to the chalcopyrite absorber layer. The role of sodium,
imperative for the growth of high efficiency chalcopyrite solar cells, and how it interacts with Al2O3 is discussed. 相似文献
924.
An unprecedented trinucleating ligand with a central 1,3,5-trimercaptobenzene unit and its trinuclear Cu(II)(3) complex are presented. The high covalency of the difficult-to-realize Cu(II)-SR bond provides an order of magnitude increase in the superexchange interaction in comparison to its oxygen analogue. 相似文献
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Nolan M Lykhach Y Tsud N Skála T Staudt T Prince KC Matolín V Libuda J 《Physical chemistry chemical physics : PCCP》2012,14(3):1293-1301
The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce(3+), while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce(3+) ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce(3+) ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts. 相似文献
930.
Five different para-substituted 3-phenylglycidates (3-phenyloxirane-2-carboxylates) were prepared and subjected to reactions with arenes and hetarenes under Lewis acid catalysis. Sc(OTf)(3) was found to effectively (5 mol%) promote a Friedel-Crafts reaction in nitromethane as the solvent. The reaction was shown to proceed stereoconvergently, which makes the intermediacy of a benzylic cation likely. The diastereoselectivities varied depending on the choice of the nucleophile and 3-arylglycidate. Best results were obtained with tert-butyl 3-anisylglycidate, which delivered the respective products with high syn-preference in diastereomeric ratios (d.r.) between 82 : 18 and >95 : 5. The observed selectivity can be explained by a model, according to which the intermediate benzylic cations adopt a preferred conformation, which allows for diastereoface-differentiation by the adjacent stereogenic center. 相似文献