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141.
L. Palacio P. Prádanos A. Hernández M.J. Ariza J. Benavente M. Nyström 《Applied Physics A: Materials Science & Processing》2001,73(5):555-560
The surfaces of three commercial urea formaldehyde polysulfone membranes from Dow DenmarkTM (GR51, GR61 and GR81) are characterised both topographically and chemically. Their topography is studied by scanning force
microscopy to obtain the corresponding pore-size distributions, which are in fair agreement with nominal molecular weight
cut-offs.
The composition of the surfaces of the membranes is analysed by X-ray photoelectron spectroscopy. The resulting percentage
content of nitrogen, which could be attributed probably to an additive used in the manufacturing process, is shown to correlate
with the portion of the total surface with different viscoelastic properties as investigated by using phase-contrast scanning
force microscopy. Both parameters are increasing for membranes with decreasing molecular weight cut-off. Also, the additive
seems to be more sparsely distributed for the membranes with bigger pores, according to fractal analysis. Finally, all the
membranes are very similarly wettable.
Received: 22 May 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001 相似文献
142.
Zh. M. Wang Yu. I. Mazur K. A. Sablon T. D. Mishima M. B. Johnson G. J. Salamo 《固体物理学:研究快报》2008,2(6):281-283
The structural complexity of GaAs quantum‐dot pairs has been revealed by cross‐sectional transmission electron microscopy. As a result of high‐temperature droplet epitaxy, the AlGaAs substrate beneath the quantum‐dot pairs is no longer immobile and its reconstruction is observed to define the crystallization of gallium droplets under an arsenic flux. The GaAs quantum‐dot pairs are immersed into the substrate and further confined by the re‐distributed AlGaAs materials above the substrate plane. There are two underlying mechanisms responsible for the final nanostructure configuration, melt‐back etching by the gallium droplets and preferential crystallization of gallium around reconstructed sidewalls. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
143.
S. Deachapunya P. J. Fagan A. G. Major E. Reiger H. Ritsch A. Stefanov H. Ulbricht M. Arndt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):307-313
Slow beams of neutral molecules are of great interest for
a wide range of applications, from cold chemistry through precision
measurements to tests of the foundations of quantum mechanics. We
report on the quantitative observation of thermal beams of
perfluorinated macromolecules with masses up to 6000 amu, reaching
velocities down to 11 m/s. Such slow, heavy and neutral molecular
beams are of importance for a new class of experiments in
matter-wave interferometry and we also discuss the requirements for
further manipulation and cooling schemes with molecules in this
unprecedented mass range. 相似文献
144.
In this work, ZnO thin films were prepared by sol-gel method and the effect of aging time of ZnO sol on the structural and optical properties of the films was studied. The structural characteristics of the samples were analyzed by an atomic force microscope and an X-ray diffractometer. The optical properties were studied by a UV-vis spectrophotometer and a fluorophotometer. The results show that the ZnO thin film prepared by the as-synthesized ZnO sol had relatively poor crystalline quality, low optical transmittance in the visible range and relatively weak ultraviolet emission performance. After the as-synthesized ZnO sol was aged for 24 h, the degree of the preferred crystal orientation along the c-axis of the ZnO thin film prepared by this aged sol was improved. At the same time, this film had a very smooth surface with uniform grains and both its visible range transmittance and ultraviolet emission intensity were obviously increased. These results suggest that appropriate aging of ZnO sol is very important for the improvement of structural and optical quality of ZnO thin films derived from sol-gel method. 相似文献
145.
The surface modification of titanium thin foil/sheet samples (0.5 mm) implanted by nitrogen ions of 30 keV energy and a fluence of 1 × 1018 N+ cm−2 at different temperatures is studied using XRD, AFM, SEM, and SIMS. XRD patterns showed the development of titanium nitride with different compositions in the implanted samples, while the presence of different titanium compositions such as titanium oxides was also observed. AFM images at 654 K showed the formation of grains, that after initial sputtering of the grain boundary at 728 K temperature, the morphology of the surface changed from small grains to a bimodal distribution of grains at 793 K which consisted of larger grains with bright hillocks within them. This was considered to be due to phase transformation/compositional changes, explained by correlating XRD and SIMS results. The SIMS results showed a maximum at about 730 K and a minimum at about 790 K for both N+ density and depth of N+ penetration in the Ti sample. The variation of these results with temperature was explained on the basis of the residual gas, substrate temperature, dissociation of water in the chamber and the gettering property of titanium. 相似文献
146.
O. Bucicov M. Nowak S. Jung G. Meijer E. Tiemann C. Lisdat 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):463-469
We produce SO2 molecules with a centre of mass velocity near zero using a Stark decelerator. Since the initial kinetic energy of the supersonic
SO2 molecular beam is high, and the removed kinetic energy per stage is small, 326 deceleration stages are necessary to bring
SO2 to a complete standstill, significantly more than in other experiments. We show that in such a decelerator possible loss
due to coupling between the motional degrees of freedom must be considered. Experimental results are compared with 3D Monte-Carlo
simulations and the quantum state selectivity of the Stark decelerator is demonstrated. 相似文献
147.
Films of a binary polymer blends comprising polychloroprene (PCP) and piperylene-styrene copolymer (PSC) have been prepared by solution casting. The dependence of the surface morphology of the free blend films on PSC content was studied with both roughness and correlation analysis of lateral force microscopy (LFM) images. Significant changes in roughness and lateral parameter values of different blend film sides have been observed depending on the blend composition. It was shown that up to 15 wt.% PSC is distributed continuously in PCP bulk. The increase of roughness and lateral parameter values at the air/film surface shows the enrichment of PCP in the blends containing 25 wt.% or more PSC. The enrichment of PCP on the air/film surface favours the increase of PSC concentration at the backing/film surface. The films underside morphology becomes similar to that of PSC, when its content reaches 40 wt.%. 相似文献
148.
We report atomic scale flattening of surfaces of microstructures formed on Si wafers by furnace annealing. To avoid thermal deformation of the fabricated structures, advantage was taken of hydrogen annealing, which enables us to decrease the relaxation rate of Si surfaces due to surface hydrogenation. We examined cross-sectional shape and sidewall morphology of 3 μm deep trenches on Si(0 0 1) substrates after annealing at 1000 °C under various H2 pressures of 40-760 Torr. We successfully formed Si trenches with flat surfaces composed of terraces and steps while preserving the designed trench profile by increasing H2 pressure to 760 Torr. 相似文献
149.
The surface modifications of tungsten massive samples (0.5 mm foils) made by nitrogen ion implantation are studied by SEM, XRD, AFM, and SIMS. Nitrogen ions in the energy range of 16-30 keV with a fluence of 1 × 1018 N+ cm−2 were implanted in tungsten samples for 1600 s at different temperatures. XRD patterns clearly showed WN2 (0 1 8) (rhombohedral) very close to W (2 0 0) line. Crystallite sizes (coherently diffracting domains) obtained from WN2 (0 1 8) line, showed an increase with substrate temperature. AFM images showed the formation of grains on W samples, which grew in size with temperature. Similar morphological changes to that has been observed for thin films by increasing substrate temperature (i.e., structure zone model (SZM)), is obtained. The surface roughness variation with temperature generally showed a decrease with increasing temperature. The density of implanted nitrogen ions and the depth of nitrogen ion implantation in W studied by SIMS showed a minimum for N+ density as well as a minimum for penetration depth of N+ ions in W at certain temperatures, which are both consistent with XRD results (i.e., IW (2 0 0)/IW (2 1 1)) for W (bcc). Hence, showing a correlation between XRD and SIMS results. 相似文献
150.
Using a 100 MeV Au beam, the surface roughening kinetics of relaxed Si1−xGex alloy films for x=0.5 and 0.7 are studied by means of ex-situ atomic force microscopy (AFM). Swift heavy ion (SHI) irradiation induced surface roughening behavior is demonstrated using the trend in variation of β as a function of fluence when the data are analyzed in terms of the Edwards-Wilkinson (EW) model. By employing the EW model, the observed surface roughening is explained on the basis of the competition between SHI induced sputtering and smoothening through redeposition of the sputtered atoms. The composition dependent variation of surface morphology with increasing fluence is discussed in the light of the strain distribution along the sample surface. 相似文献