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991.
H. Angermann J. Rappich I. Sieber M. Schmidt J. Polte 《Applied Surface Science》2008,254(12):3615-3625
Special sequences of wet-chemical oxidation and etching steps were optimised with respect to the etching behaviour of differently oriented silicon to prepare very smooth silicon interfaces with excellent electronic properties on mono- and poly-crystalline substrates. Surface photovoltage (SPV) and photoluminescence (PL) measurements, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were utilised to develop wet-chemical smoothing procedures for atomically flat and structured surfaces, respectively. Hydrogen-termination as well as passivation by wet-chemical oxides were used to inhibit surface contamination and native oxidation during the technological processing. Compared to conventional pre-treatments, significantly lower micro-roughness and densities of surface states were achieved on mono-crystalline Si(100), on evenly distributed atomic steps, such as on vicinal Si(111), on silicon wafers with randomly distributed upside pyramids, and on poly-crystalline EFG (Edge-defined Film-fed-Growth) silicon substrates.The recombination loss at a-Si:H/c-Si interfaces prepared on c-Si substrates with randomly distributed upside pyramids was markedly reduced by an optimised wet-chemical smoothing procedure, as determined by PL measurements. For amorphous-crystalline hetero-junction solar cells (ZnO/a-Si:H(n)/c-Si(p)/Al) with textured c-Si substrates the smoothening procedure results in a significant increase of short circuit current Isc, fill factor and efficiency η. The scatter in the cell parameters for measurements on different cells is much narrower, as compared to conventional pre-treatments, indicating more well-defined and reproducible surface conditions prior to a-Si:H emitter deposition and/or a higher stability of the c-Si surface against variations in the a-Si:H deposition conditions. 相似文献
992.
D. Margarone L. Láska S. Gammino E. Krouský M. Pfeifer M. Rosiñski J. Skála A. Velyhan 《Applied Surface Science》2008,254(9):2797-2803
Long pulse laser shots of the PALS iodine laser in Prague have been used to obtain metal target ablation at various experimental conditions. Attention is paid mainly to the dependencies of the crater diameter on the position of minimum laser-focus spot with regard to the target surface, by using different laser wavelengths and laser energies. Not only a single one, but two minima, independently of the wavelength, of the target irradiation angle and of the target material, were recorded. Significant asymmetries, ascribed to the non-linear effects of intense laser beam with pre-formed plasma, were found, too. Estimations of ejected mass per laser pulse are reported and used to calculate the efficiency of laser-driven loading. Results on metal target ablation and crater formation at high intensities (from 2 × 1013 to 3 × 1016 W/cm2) are presented and compared. Crater depth, crater diameter and etching yield are reported versus the laser energy, in order to evaluate the ablation threshold fluence. 相似文献
993.
We have quantized a flat cosmological model in the context of the metric models, using the causal Bohmian quantum theory. The equations are solved and then we have obtained how the quantum corrections
influence the classical equations. 相似文献
994.
Giorgio Papini 《General Relativity and Gravitation》2008,40(6):1117-1144
External gravitational fields induce phase factors in the wave functions of particles. The phases are exact to first order
in the background gravitational field, are manifestly covariant and gauge invariant and provide a useful tool for the study
of spin–gravity coupling and of the optics of particles in gravitational or inertial fields. We discuss the role that spin–gravity
coupling plays in particular problems. 相似文献
995.
Jamie Vicary 《International Journal of Theoretical Physics》2008,47(12):3408-3447
This paper describes how the structure of the state space of the quantum harmonic oscillator can be described by an adjunction
of categories, that encodes the raising and lowering operators into a commutative comonoid. The formulation is an entirely
general one in which Hilbert spaces play no special role.
Generalised coherent states arise through the hom-set isomorphisms defining the adjunction, and we prove that they are eigenstates
of the lowering operators. Generalised exponentials also emerge naturally in this setting, and we demonstrate that coherent
states are produced by the exponential of a raising morphism acting on the zero-particle state. Finally, we examine all of
these constructions in a suitable category of Hilbert spaces, and find that they reproduce the conventional mathematical structures. 相似文献
996.
The Mechanism of Quantum Computation 总被引:1,自引:1,他引:0
Giuseppe Castagnoli 《International Journal of Theoretical Physics》2008,47(8):2181-2194
997.
Daniel Lehmann 《International Journal of Theoretical Physics》2008,47(5):1333-1353
The concept of a superposition is a revolutionary novelty introduced by Quantum Mechanics. If a system may be in any one of
two pure states x and y, we must consider that it may also be in any one of many superpositions of x and y. An in-depth analysis of superpositions is proposed, in which states are represented by one-dimensional subspaces, not by
unit vectors as in Dirac’s notation. Superpositions must be considered when one cannot distinguish between possible paths,
i.e., histories, leading to the current state of the system. In such a case the resulting state is some compound of the states
that result from each of the possible paths. States can be compounded, i.e., superposed in such a way only if they are not
orthogonal. Since different classical states are orthogonal, the claim implies no non-trivial superpositions can be observed
in classical systems. The parameter that defines such compounds is a proportion defining the mix of the different states entering
the compound. Two quantities, p and θ, both geometrical in nature, relate one-dimensional subspaces in complex Hilbert spaces: the first one is a measure of proximity
relating two rays, the second one is an angle relating three rays. The properties of superpositions with respect to those
two quantities are studied. The algebraic properties of the operation of superposition are very different from those that
govern linear combination of vectors.
This work was partially supported by the Jean and Helene Alfassa fund for research in Artificial Intelligence, by the Israel
Science Foundation grant 183/03 on “Quantum and other cumulative logics” and by EPSRC Visiting Fellowship GR/T 24562 on “Quantum
Logic”. 相似文献
998.
Wenbiao Liu 《International Journal of Theoretical Physics》2008,47(7):1979-1986
Hawking radiation can usefully be viewed as a semi-classical tunneling process that originates at the black hole horizon.
Massive radiation from a BTZ black hole is investigated. The conservation of energy implies the effect of self-gravitation.
Viewed as a tunneling process, the emission spectrum derivates from the pure thermal spectrum, but it is consistent with an
underlying unitary theory. The result is the same as that of massless particles. 相似文献
999.
We provide a method for constructing a set of four-photon states suitable for quantum communication applications. Among these
states is a set of concatenated quantum code states that span a decoherence-free subspace that is robust under collective-local
as well as global dephasing noise. This method requires only the use of spontaneous parametric down-conversion, quantum state
post-selection, and linear optics. In particular, we show how this method can be used to produce all sixteen elements of the
second-order Bell gem
, which includes these codes states and is an orthonormal basis for the Hilbert space of four qubits composed entirely of
states that are fully entangled under the four-tangle measure. 相似文献
1000.