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1.
Multi-quantum well heterostructures (MQWHs) of the novel Ga(NAsP)/GaP material system have been grown, pseudomorphically strained to GaP-substrate. The crystalline perfection is verified by transmission electron microscopy (TEM). For As-concentrations in excess of about 70%, a direct band structure and adequate luminescence efficiency for laser device application is observed. Temperature-dependent photoluminescence (PL) investigations show the influence of carrier localisation and non-radiative recombination processes typical for dilute nitride materials. With rising N content in the active material, the emission wavelength shifts towards longer wavelength, leading to Ga(NAs)/GaP MQW structures with photon energies below the indirect band gap of silicon (Si). At the same time the luminescence intensity drops due to an increase in non-radiative carrier traps and/or structural degradation. 相似文献
2.
3.
Phenomena accompanying electrochemical doping of solid fullerene films with potassium were studied by sputter ion depth profiling
(XPS and SIMS). The potassium distribution was determined, and artifacts associated with possible damage of the layer composition
caused by ion impact were investigated and discussed. To compare the charge transfer while reductive doping is taking place
at fullerene/solution interface with doping from gas phase, model layers were prepared and doped by potassium under UHV conditions.
It was found that sputtering by Ar+ primary ions yields both accurate information on the alkaline metal distribution and on its concentration. Sputtering by
O+ ions led to an enrichment of potassium, apparently due to the reactivity of oxygen with the fullerene matrix. It is shown
that the reductive doping starts at the fullerene/solution interface. The concentration of potassium in the doped films was
found to be lower than expected from the charge transferred during the electrochemical reduction. Other phase transformations
such as hydrogenation are discussed.
Received March 4, 2002; accepted July 26, 2002 相似文献
4.
G. Stolz 《Mathematische Nachrichten》1997,183(1):275-294
This paper continues the investigation about the singularity theory in dual rich quasi–Banach spaces given in T. Runst [Ru 2]. The abstract results are applied to the study of the solution structure of semilinear elliptic boundary value problems in spaces of Besov – Triebel – Lizorkin type. 相似文献
5.
Eckhard Steffen 《Discrete Mathematics》2004,280(1-3):191-214
Cubic bridgeless graphs with chromatic index four are called uncolorable. We introduce parameters measuring the uncolorability of those graphs and relate them to each other. For k=2,3, let ck be the maximum size of a k-colorable subgraph of a cubic graph G=(V,E). We consider r3=|E|−c3 and
. We show that on one side r3 and r2 bound each other, but on the other side that the difference between them can be arbitrarily large. We also compare them to the oddness ω of G, the smallest possible number of odd circuits in a 2-factor of G. We construct cyclically 5-edge connected cubic graphs where r3 and ω are arbitrarily far apart, and show that for each 1c<2 there is a cubic graph such that ωcr3. For k=2,3, let ζk denote the largest fraction of edges that can be k-colored. We give best possible bounds for these parameters, and relate them to each other. 相似文献
6.
Michael Demuth Peter Stollmann Günter Stolz Jan van Casteren 《Integral Equations and Operator Theory》1995,23(2):145-153
We give trace norm estimates for products of integral operators and for diffusion semigroups. These are applied to differences of heat semigroups. A natural example of an integral operator with finite trace which is not trace class is given. 相似文献
7.
S.N. Vdovichev B.A. Gribkov S.A. Gusev E. Il’ichev Yu.N. Nozdrin G.L. Pakhomov A.V. Samokhvalov R. Stolz A.A. Fraerman 《Journal of magnetism and magnetic materials》2006
The effect of an array of ferromagnetic nanoparticles on the field-dependent critical current of the short overlap Josephson junction is experimentally studied. Large reversible variations of the maximum critical current are observed depending on the magnetic state of the particles. The pronounced commensurability effects are detected which are proved by the additional peaks of magnetic field induced diffraction pattern. 相似文献
8.
9.
We report on first experiments combining quasi-digital highly selective etching and atomic force microscopy (AFM) to examine the interior interfaces of semiconductor heterostructures. Lattice matched (GaIn)As/InP heterostructures grown by metalorganic vapour-phase epitaxy (MOVPE) are taken as a model system to check the capabilities of this new method. Standard selective etchants for different material systems have been optimized in selectivity and etch rate to achieve a quasi-digital etching behaviour. In this way, the real structure of interior interfaces can be determined by AFM. We find a significant difference between the surface of the heterostructure and the interior interfaces. 相似文献
10.