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21.
A simple method for patterning of thin (15–650 nm) aluminum films on glass substrates by direct, low-power, laser-thermal
oxidation in water under common laboratory conditions is demonstrated. Local heating of the metal film enhances the formation
of aluminum oxide (hydrargillite, Al2O3–3H2O) and provokes breakdown of the passivation layer followed by local corrosion at temperatures close to the boiling point
of water. Moving the focus of an Ar-ion laser (λ=488 nm) over the aluminum film with a speed of several μm/s yields grooves
flanked by hydrargillite. Upon through oxidation of the metal these structures act as electrically insulating domains. Depending
on the film thickness, the minimum width of the line structures measures between 266 nm and 600 nm. The required laser irradiation
power ranges from 1.7 mW to 30 mW. It is found that the photo-thermal oxidation process allows for writing of two-dimensional
electrode patterns.
Received: 16 July 2001 / Accepted: 23 July 2001 / Published online: 2 October 2001 相似文献
22.
23.
In this paper, the mathematical expressions and the particularities of the joint fractional Fourier transform correlator (JFRTC) are detailedly analyzed. In a JFRTC, the distance between the two fractional correlation peaks can be adjusted flexibly by shifting the fractional orders. However, the intensity of the fractional correlation peaks decreases rapidly as the first fractional order p1 drops. The former property is very useful in a practical recognition system, but the latter one seriously reduces the recognition sensitivity of a JFRTC. For this reason, phase masks should be added at the input plane of the JFRTC to enhance the intensities of the fractional correlation peaks and effectively overcome the default. Compared with the existing JFRTC with single phase modulation, a JFRTC with double phase modulation is suggested to more flexibly improve the performance of a JFRTC. 相似文献
24.
The design of an acousto-optic modulator using paratellurite requiring only low driving power is described. Because of the high figure of merit a high modulation index can be achieved. To avoid an intermediate transmission peak the modulator should not be operated in the Bragg-regime but rather in the transition regime. The time dependent transmission for this regime is calculated as a function of the material parameters. Experimentally, modulation indices up to 10 are obtained. Using such a TeO2 mode-locker a pulsed Nd:Cr:GSGG laser delivered pulses down to 70 ps. 相似文献
25.
J. M. Will W. Eisfeld K. F. Renk S. Haussühl 《Applied Physics A: Materials Science & Processing》1983,31(4):191-193
Tunable detection of high-frequency phonons in LaF3 is reported. Phonons generated by a heat-pulse technique are detected by phonon-induced fluorescence from magnetically split energy levels of Er3+ impurity ions. Evidence for a strongly frequency-dependent lifetime of acoustic phonons at frequencies above 600 GHz is found. The lifetime is attributed to spontaneous anharmonic phonon decay. 相似文献
26.
Yousuke Fukaya Takashi Yanase Yasushi Kubota Shigeki Imai Taketoshi Matsumoto Hikaru Kobayashi 《Applied Surface Science》2010,256(18):5610-5613
We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5-10 nm) SiO2/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 °C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO2 layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 × 1022 atoms/cm2, and it increases by POA at 400 °C in wet-oxygen (2.32 × 1022 atoms/cm2) or dry-oxygen (2.30 × 1022 atoms/cm2). The leakage current density is considerably low (e.g., 10−5 A/cm2 at 8 MV/cm) and it is greatly decreased (10−8 A/cm2 at 8 MV/cm) by POA at 400 °C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO2 layer, and decreases the density of oxide fixed positive charges. 相似文献
27.
We have developed low temperature formation methods of SiO2/Si and SiO2/SiC structures by use of nitric acid, i.e., nitric acid oxidation of Si (or SiC) (NAOS) methods. By use of the azeotropic NAOS method (i.e., immersion in 68 wt% HNO3 aqueous solutions at 120 °C), an ultrathin (i.e., 1.3-1.4 nm) SiO2 layer with a low leakage current density can be formed on Si. The leakage current density can be further decreased by post-metallization anneal (PMA) at 200 °C in hydrogen atmosphere, and consequently the leakage current density at the gate bias voltage of 1 V becomes 1/4-1/20 of that of an ultrathin (i.e., 1.5 nm) thermal oxide layer usually formed at temperatures between 800 and 900 °C. The low leakage current density is attributable to (i) low interface state density, (ii) low SiO2 gap-state density, and (iii) high band discontinuity energy at the SiO2/Si interface arising from the high atomic density of the NAOS SiO2 layer.For the formation of a relatively thick (i.e., ≥10 nm) SiO2 layer, we have developed the two-step NAOS method in which the initial and subsequent oxidation is performed by immersion in ∼40 wt% HNO3 and azeotropic HNO3 aqueous solutions, respectively. In this case, the SiO2 formation rate does not depend on the Si surface orientation. Using the two-step NAOS method, a uniform thickness SiO2 layer can be formed even on the rough surface of poly-crystalline Si thin films. The atomic density of the two-step NAOS SiO2 layer is slightly higher than that for thermal oxide. When PMA at 250 °C in hydrogen is performed on the two-step NAOS SiO2 layer, the current-voltage and capacitance-voltage characteristics become as good as those for thermal oxide formed at 900 °C.A relatively thick (i.e., ≥10 nm) SiO2 layer can also be formed on SiC at 120 °C by use of the two-step NAOS method. With no treatment before the NAOS method, the leakage current density is very high, but by heat treatment at 400 °C in pure hydrogen, the leakage current density is decreased by approximately seven orders of magnitude. The hydrogen treatment greatly smoothens the SiC surface, and the subsequent NAOS method results in the formation of an atomically smooth SiO2/SiC interface and a uniform thickness SiO2. 相似文献
28.
Vertically aligned monodomain nematic liquid-crystal elastomers contract when heated. If a temperature gradient is applied
across the width of such a cantilever, inhomogeneous strain distribution leads to bending motion. We modelled the kinetics
of thermally induced bending in the limit of a long thin strip and the predicted time variation of curvature agreed quantitatively
with experimental data from samples with a range of critical indices and nematic-isotropic transition temperatures. We also
deduced a value for the thermal diffusion coefficient of the elastomer. 相似文献
29.
J.L. Jiménez-Pérez A. Cruz-Orea J.F. Sanchez Ramirez E. Ramón-Gallegos 《Applied Surface Science》2008,255(3):643-645
In this work we have used the Photoacoustic Spectroscopy (PAS) to determine in vitro the non-radiative relaxation time (NRRT) of a protoporphyrin IX (PpIX) standard solution and samples of PpIX(1), PpIX(2) and PpIX(3) with Au nanoparticle concentrations of 0.001008, 0.00504 and 0.01008 mmol in 25 mL of water respectively. We have used PpIX disodium salt (DS) solution of 25% HCl. The results show that the NRRT average values, obtained for each one of the solution were: τ = 29 ± 0.001, 84 ± 0.001 and 62 ± 0.009 ms for PpIX(1), PpIX(2) and PpIX(3), respectively. These values were compared with some NRRT of triplet states reported in the literature for molecules with tetrapyrrolic structure, increasing the NRRT considerably. From each solution it was obtained its PAS signal phase as a function of the light modulation frequency from 17 to 80 Hz. UV-vis spectrophotometer, photoluminescence spectroscopy and Transmission Electron Microscopy (TEM) were used in order to obtain the optical absorption spectra, the photoluminescence intensities, and the gold nanoparticle sizes respectively. Our investigations are devoted to improve the thermal treatments of drugs the porphyrins as photosensitizers used in image photodynamic therapy. 相似文献
30.
Realization of MMI Power Splitter by UV-light Imprinting Technique Using Hybrid Sol-Gel SiO2 Materials
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An efficient fabrication scheme of buried ridge waveguide devices is demonstrated by UV-light imprinting technique using organic-inorganic hybrid sol-gel Zr-doped SiO2 materials. The refractive indices of a guiding layer and a cladding layer for the buried ridge waveguide structure are 1.537 and 1.492 measured at 1550nm, respectively. The tested results show more circular mode profiles due to existence of the cladding layer. A buried ridge single-mode waveguide operating at 1550 nm has a low propagation loss (0.088 dB/cm) and the 1× 2 MMI power splitter exhibits uniform outputs, with a very iow splitting loss of 0.029 dB at 1549nm. 相似文献