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161.
Muresan AS Ostrovskii BI Sánchez-Ferrer A Finkelmann H de Jeu WH 《The European physical journal. E, Soft matter》2006,19(4):385-388
We report a high-resolution X-ray lineshape study of main-chain smectic polymers. The results indicate that the layer ordering
differs fundamentally from the algebraic decay typical for other smectic liquid-crystalline systems. The lineshapes are best
described by broad squared Lorentzians indicating some form of short-range correlations. However, several higher harmonics
are observed, which excludes simple liquid-like short-range order. This behaviour is tentatively attributed to a random field
of defects associated with entangled hairpins in the main-chain polymer structure. 相似文献
162.
The binding energy of an impurity located at the center of multilayered spherical quantum dot (MSQD) is reported as a function of the dot and barrier thickness for different alloy compositions under the influence of a magnetic field. Within the effective mass approximation, the binding energy has been calculated using the fourth order Runge-Kutta method without magnetic field. A variational approach has been employed if a magnetic field is present. The binding energy in MSQD with equal dot and barrier thickness is calculated. It is shown that the binding energy in MSQD differs from that of a single quantum dot. Also, the geometry is dominant on the binding energy for thin MSQDs, but the magnetic field becomes more effective for thick MSQDs. 相似文献
163.
B. A. van Hassel A. J. Burggraaf 《Applied Physics A: Materials Science & Processing》1991,52(6):410-417
The oxidation state of Fe and Ti ions implanted in yttria stabilized zirconia (YSZ) was studied by XPS (X-ray photoelectron spectroscopy) in combination with depth profiling using Ar+ sputtering. In the as-implanted state of the sample Fe was found to be present as Fe3+, Fe2+ and as metallic Fe0. This is in agreement with earlier conversion electron Mössbauer Spectroscopy measurements. For Ti-implanted YSZ in the as-implanted state the majority of the Ti is present as Ti4+, Ti3+, and Ti2+ ions, while a part of the Zr cations is present in the divalent oxidation state (Zr2+). After oxidation in air, the Fe and Ti ions are present only in the valence three and four oxidation states, respectively. 相似文献
164.
Beam shaping and homogenization techniques are essential to optimize a large number of laser-material processing applications and laser-material interaction studies. In this paper, we present an innovative approach for modeling laser beam homogenization by means of the integration method. The numerical results are compared with experimental data, and the influence of the measurement technique is discussed. The enhancement of the homogenization capability using an asymmetric divider is also presented and discussed. 相似文献
165.
N. Ikeda F. Nakamura Y. Inotani K. Koga M. Koga S. Koto T. Sugimitsu H. Fujita S. Morinobu 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):213-220
The 16O(11B,12C)15N reaction at 41.25 MeV has been investigated using the kinematical coincidence method. Polarization tensors t20 and t40 of 12C[2+
1] for the quantization axis taken along the direction of propagation have been measured at center-of-mass angles (Θc.m.) between 48° and 62° by analyzing the energy spectrum of 12C[2+
1] modulated by the effect of γ-ray emission. The cross-sections of the transfer reactions leading to the 12C[g.s.]+15N[g.s.], 12C[2+
1]+15N[g.s.] and 12C[g.s.]+15N[3/2-
1] final states have also been measured in the range 48°≤Θc.m.≤ 120°. The polarization tensor terms of 12C[2+
1] largely deviating from zero have been observed, contrary to the prediction by the distorted-wave Born approximation (DWBA).
The one-step DWBA calculation also fails in describing the transfer reaction cross-sections. It is shown that the coupled
channel model calculation including excitations and reorientations in 11B and 12C satisfactorily reproduces both the tensor terms and the cross-sections of the transfer reactions. The multi-step processes
passing through the excited states of 11B are found to significantly contribute to the reaction.
Received: 3 July 2000 / Accepted: 15 September 2000 相似文献
166.
In this work, a new way of achieving the recovery from the EL2 metastable state is reported and analyzed theoretically. Despite being an old problem, no definitive picture of the EL2 center has been established to date. For this reason, long past the days of effervescent research on the EL2, new models and investigations keep appearing in the literature as, for example, the recently proposed autocatalytic model to describe the inter-defect correlation during the thermal recovery process [A. Fukuyama, T. Ikari, Y. Akashi, M. Suemitsu, Phys. Rev. B 67 (2003) 113202]. In the course of a re-evaluation of the EL2 for nanosecond volume holographic storage, we found that a strong laser pulse is capable of destroying the metastable state and decided to investigate further this effect. The experiment reported here consists of monitoring the transmission of a λ = 1.05 μm continuous-wave (CW) laser, used to populate the metastable state, while subjecting the sample to the incidence of a strong λ = 1.06 μm laser pulse. A full simulation of the problem has been carried out and the results could be fit very well by assuming a recovery induced by electron-hole recombination and a nonlinear free-carrier production mechanism. It is perhaps worth noting that such a fast recovery induced by the nanosecond laser may prove to be an interesting tool to initiate a recovery process (even at low temperature) in a controlled way to check the predictions of the recently proposed autocatalytic recovery process. 相似文献
167.
Yunbo Li 《Optics Communications》2006,266(2):686-690
We numerically analyze the effects of radius and phase shift of phase objects on the diffraction image of the 4f coherent imaging system, a system used for measuring the third-order nonlinear refractive index. The selection of the aperture radius is discussed. We prove that when the phase object radius is 0.1 time of the aperture radius and the phase change of the phase object is 0.57π, one can get the highest sensitivity for nonlinear refraction measurement. 相似文献
168.
Arūnas Jagminas Marija Kurtinaitien? Gintaras Valin?ius 《Applied Surface Science》2006,252(6):2360-2367
A new simple method for modification of the porous alumina barrier-layer is described and characterized by the voltammetric, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) techniques. The method is based on re-anodization of porous alumina under galvanostatic conditions in the anodizing bath that, in addition to conventional anodization solution components, contains fluoride salts: (NH4)2SiF6 or NH4F. During first few minutes of alumina re-anodization, the sharp drop of anodizing voltage was observed, which is indicative of chemical/electrochemical transformations of the alumina barrier-layer. As a result, the scalloped structure of the barrier-layer changes drastically, becoming smooth and finely grained. Upon re-anodization, a significant loss of insulating ability of the barrier-layer and considerable increase in its capacitance were observed, while the variation of the constant phase element was found to be consistent with the oxide film morphology transformations observed by microscopy techniques. All these changes intensify with fluoride concentration increase. Curiously, (NH4)2SiF6 exhibited about three-fold stronger effect on the barrier-layer properties than NH4F, thus allowing us to hypothesize about possible chemical break up of SiF62− anion and the formation of the AlF3 phase inside the alumina pores. 相似文献
170.
The main conditions and parameters for obtaining surface relief total internal reflection diffraction gratings in conical mounting are presented. Calculated and experimental investigations reveal that there are ranges of grating periods, incidence angles, diffraction angles and gratings depths for which such gratings could be obtained, both for TE and TM polarizations. With optimized grating parameters the diffraction efficiency of the total internal reflection diffraction gratings can be greater than 90%. 相似文献