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211.
212.
Defect engineering for SiO2 precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (SIMOX). Cavities axe created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120 keV 8.0 ×1016 cm 2 0 ions. The Q ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectionM transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.  相似文献   
213.
T. Fu  Y.G. Shen  Z.F. Zhou 《Journal of Non》2008,354(27):3235-3240
Amorphous carbon nitride (CNx) films with silicon addition up to 16 at.% are sputter deposited on Si(1 0 0) substrate, and the surface morphology is studied with scaling method based on atomic force microscopy. The surface roughness σ, the roughness exponent α, and the lateral correlation length ξ decrease with silicon content of the films, reaching 0.33 nm, 0.80 and 50 nm, respectively, for the film with [Si] = 16 at.%. The addition of silicon in the films leads to additional Si-N, Si-C-N and CN bonds revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The films undergo a structural transition from columnar to smooth morphology in cross-section with silicon addition demonstrated by field emission scanning electron microscopy. Nano-sized clusters sparsely dispersed in amorphous matrix of the film with [Si] = 16 at.% are observed by high-resolution transmission microscopy. According to the surface growth mechanism in which surface diffusion and geometrical shadowing drive structural and morphological evolution of the sputter deposited films, surface smoothing of the amorphous CNx films by silicon addition is explained by the formation of Si-N and Si-C-N bonds that impede surface diffusion of the adsorbed species during film growth, which leads to the reduced size of the columnar structures.  相似文献   
214.
SiO2 samples were implanted with 45 keV Zn ions at doses ranging from 5×1015 to 1.0×1017 ions/cm2, and were then subjected to furnace annealing at different temperatures. Several techniques, such as ultra-violet–visible spectroscopy (UV–vis), grazing incidence X-ray diffraction spectroscopy (GXRD) and atomic force microscopy (AFM), have been used to investigate formation of nanoparticles and their thermal evolution. Our results clearly show that Zn nanoparticles could be effectively formed in SiO2 at doses higher than 5×1016 ions/cm2. The subsequent thermal annealing at oxygen ambient could induce the growth of Zn nanoparticles at intermediate annealing temperature range. While at temperature above 600 °C, Zn nanoparticles could be transformed into ZnO, or even Zn2SiO4 nanoparticles. The results have been tentatively discussed in combination with Zn diffusion and migration obtained by Rutherford backscattering spectroscopy (RBS) measurements.  相似文献   
215.
Recently, it has been observed that a liquid film spreading on a sample surface will significantly distort atomic force microscopy (AFM) measurements. In order to elaborate on the effect, we establish an equation governing the deformation of liquid film under its interaction with the AFM tip and substrate. A key issue is the critical liquid bump height yoc, at which the liquid film jumps to contact the AFM tip. It is found that there are three distinct regimes in the variation of yoc with film thickness H, depending on Hamaker constants of tip, sample and liquid. Noticeably, there is a characteristic thickness H^* physically defining what a thin film is; namely, once the film thickness H is the same order as H^*, the effect of film thickness should be taken into account. The value of H^* is dependent on Hamaker constants and liquid surface tension as well as tip radius.  相似文献   
216.
杜宇雷 《中国物理快报》2009,26(11):168-170
We perform a first-principles study on the electronic structure and elastic properties of TiaA1C with an antiperovskite structure. The absence of band gap at the Fermi level and the finite value of the density of states at the Fermi energy reveal the metallic behavior of this compound. The elastic constants of Ti3AlC are derived yielding c11 = 356 GPa, c12 = 55 GPa, c44 = 157 GPa. The bulk modulus B, shear modulus G and Young's modulus E are determined to be 156, 151 and 342 GPa, respectively. These properties are compared with those of Ti3AlC2 and Ti2AlC with a layered structure in the Ti-Al-C system and FeaAlC with the same antiperovskite structure.  相似文献   
217.
We report observation of fast and efficient VUV/UV luminescence from the mixed (Ba,La)F2:Er crystals. The broad bands, peaking at 162.5, 181.9, 194.2, 202.8, 216.1, 233.5 and 281.5 nm and decaying, at 10 and 293 K, with time constants of 46 and 35 ns respectively, are due to spin-allowed transitions from the low-spin (LS) state of the 4f105d configuration.We also observed a weak and slow broad band emission peaking at 170 nm due to the spin-forbidden transition from the high-spin (HS) state of the 4f105d configuration.While at room temperature the excitation into any of the three identified LS bands (J=8, 7 and 6) dominating the excitation spectrum yields fast VUV and UV emissions, at 10 K the excitation into higher lying J=7 and 6 bands generates slow and sharp line emissions. The positions of these lines fit energies of transitions originating from the 2G7/2 multiplet at 66140 cm−1. The emission from the 2G7/2 multiplet has been never, to the best of our knowledge, observed before.The efficient and fast VUV and UV emissions from the higher (LS, J=8) with almost no contribution from the lower (HS, J=8) level of the 4f105d configuration are possible because the modified crystal field in (Ba,La)F2 shifts the level of the (LS, J=8) state below the 2F5/2 multiplet which, therefore, does not contribute to nonradiative relaxation between the LS and HS levels.We conclude that the 2G7/2 and 2F5/2 levels have major impact on VUV and UV emissions from the Er3+ ion in (Ba,La)F2 contributing to complex emission pattern described in this report Their key role, elucidated by the VUV and UV luminescence spectroscopy, is consistent with predictions from a simple configuration coordinate model based on experimental results and calculations of the 4f11 energy levels.  相似文献   
218.
Nanosized barium aluminate materials was doped by divalent cations (Ca2+, Sr2+) and Eu2+ having nominal compositions Ba1−xMxAl12O19:Eu (M=Ca and Sr) (x=0.1-0.5), were synthesized by the combustion method. These phosphors were characterized by XRD, scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS) and photoluminescence measurement. The photoluminescence characterization showed the presence of Eu ion in divalent form which gave emission bands peaking at 444 nm for the 320 nm excitation (solid-state lighting excitation), while for 254 nm it gave the same emission wavelength of low intensity (1.5 times) compared to 320 nm excitation. It was also observed that alkaline earth metal (Ca2+ and Sr2+) dopants increase the intensity of Eu2+ ion in BaAl12O19 lattice, thus this phosphor may be useful for solid-state lighting.  相似文献   
219.
In this study different encapsulating agents have been used for chemical modification of fullerenes. Fullerenes have reacted with tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and ethylene vinyl acetate-ethylene vinyl versatate at room temperature under mechanical milling. The obtained powder has been dispersed in water by ultrasonication. The fullerene based colloids have been characterized by UV-vis, FTIR, Raman spectroscopy and atomic force microscopy. FTIR and Raman analysis have shown the presence of C60 after surface functionalization.  相似文献   
220.
The electro‐forming procedure was applied to NaNbO3:Mn and NaNbO3 insulator crystals. The electric current flow induced a transition to the metallic‐type temperature dependence of the resistance. The Mn dopant shortened the time needed for the transition. The LC‐AFM measurement showed a non‐homogeneous distribution in local resistance resulting from the electric field via the AFM tip. We ascribe this effect to percolation in the network of the highly conducting filaments, whose formation is facilitated by the Mn ions. We conclude that the insulator–metal transition is induced within a subsystem of extended defects already existing in the NaNbO3:Mn crystal lattice host. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
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