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61.
Reduction of dislocation density and improvement of optical quality in ZnO layers by MgO-buffer annealing 总被引:1,自引:0,他引:1
Hiroki Goto Hisao Makino Agus Setiawan Takuma Suzuki Chihiro Harada Tsutomu Minegishi Meoung-Whan Cho Takafumi Yao 《Current Applied Physics》2004,4(6):637-639
Optical properties of ZnO thin films with/without MgO-buffer annealing were investigated by low and room temperature photoluminescence measurements. The ZnO films were grown on c-sapphire substrates by plasma-assisted molecular-beam epitaxy employing a thin MgO-buffer layer. Dislocation density of ZnO layer was reduced from 5.3 × 109 to 1.9 × 109 cm−2 by annealing MgO-buffer prior to the growth of ZnO. The intensity of free exciton emission from the sample with MgO-buffer annealing was almost twice of that from the sample without annealing, while the deep level emission from the sample with MgO-buffer annealing was about 1/3 of that without annealing. The MgO-buffer annealing improves optical quality of overgrown ZnO films. 相似文献
62.
The equations for a barotropic viscous gas in one space dimensiondν=(μ(?νε)ε?p ε)dt+dG,? t +?2νε=0,p=?γ with a perturbationdG are considered under the assumption thatG is only a function of bounded variation inL 2(Θ) orH 0 1 (Θ) (Θ=]0, α[) and the esistence and the uniqueness of the global solution in a class of solutions of «strong type» as well as in a class of solutions of «weak type» are proved. This result constitutes a generalization of the result of Kazhikhov [8] and that of Shelukhin [10] and contains preliminary considerations for the corrisponding stochastic equations. 相似文献
63.
Tsutomu Kagiya Shizuo Narisawa Taizo Ichida Kenichi Fukui Hisao Yokota Masatsune Kondo 《Journal of polymer science. Part A, Polymer chemistry》1966,4(2):293-299
The copolymerization of carbon monoxide and aziridines such as ethylenimine and propylenimine was carried out by γ-ray irradiation. Aziridines and carbon monoxide were allowed to copolymerize under γ-ray irradiation from a Co60 source and gave a crystalline solid copolymer. The yield of the copolymer increased with reaction temperature. The composition of copolymers obtained did not depend on the feed ratio of monomers and was found to be almost equimolar. The copolymer of ethylenimine and carbon monoxide melted at about 322–335°C. with decomposition and has an infrared spectrum identical with that of poly-β-alanine obtained by the hydrogen-migration polymerization of acrylamide. The hydrolyzed product of the ethylenimine–carbon monoxide copolymer was confirmed to be β-alanine by paper chromatography. These results lead to the conclusion that the copolymerization of aziridines and carbon monoxide took place alternatively by γ-ray irradiation, and produced crystalline poly-β-alanines. 相似文献
64.
Hisao Yamashige Shuji Matsuo Tsutomu Kurisaki Rupert C C Perera Hisanobu Wakita 《Analytical sciences》2005,21(3):309-314
X-ray absorption near edge structure (XANES) measurements at the C, N, and Fe K absorption edges were performed for iron(III)-tetraphenylporphyrin (FeTPP), iron(III)-tetrakis(p-carboxyphenyl)porphyrin (FeTCPP), and iron(III)-tetrakis(p-sulfonatophenyl)porphyrin (FeTSPP). The spectral shapes differ in the Fe K XANES, but not in C and N K XANES among FeTPP, FeTCPP, and FeTSPP. Crosschecks of XANES data for C, N, and Fe K absorption edges in combination with discrete variational (DV)-Xalpha molecular orbital (MO) calculations indicate that each p-electron-withdrawing group on four meso-phenyl substitutes in an Fe(III)-porphyrin complex brings about a unique electron state through the complex because of the electron-withdrawal strength, itself. Consequently, they affect the positive charge of the center Fe(III) ion. 相似文献
65.
Hisao Yamashige Shuji Matsuo Tsutomu Kurisaki Rupert C C Perera Hisanobu Wakita 《Analytical sciences》2005,21(6):635-639
This study investigated the protonation of nitrogen atoms in porphyrins with meso-phenyl p-substituted by an electron-withdrawing group using N 1s X-ray photoelectron spectroscopy (XPS), the N K X-ray absorption near-edge structure (XANES), and the discrete variational (DV)-Xalpha molecular orbital (MO) method. Both tetraphenylporphyrin (TPP) and tetrakis(p-sulfonatophenyl)porphyrin (TSPP) have a single structure: the former has two protonated and two non-protonated N atoms in the porphine ring; the latter has four protonated N atoms in the porphine ring. In contrast, a combination of XPS, XANES, and DV-Xalpha MO calculations shows that tetrakis(p-carboxyphenyl)porphyrin (TCPP) has a dual structure: one structure has two protonated and two non-protonated N atoms; the other has four protonated N atoms. Furthermore, this result was also considered based on the protonation constants of N atoms in the porphyrins. The correlation between the strength of electron-withdrawing groups and protonation to N atoms in porphyrins can be described using the spectral patterns of the N 1s XPS and N K XANES spectra. 相似文献
66.
Photoluminescence characteristics of nitrogen atomic-layer-doped GaAs grown by MOVPE 总被引:1,自引:0,他引:1
Nitrogen atomic-layer-doped and uniformly doped GaAs were grown by MOVPE using dimethylhydrazine on a (001) plane. They showed several sharp photoluminescence lines with a full width at half maximum less than 1 meV at 8 K. Compared with uniformly doped GaAs, the photoluminescence intensity of the nitrogen-related line at the longest wavelength is enhanced in nitrogen atomic-layer-doped GaAs, suggesting that it is easier to form nitrogen pairs during atomic layer doping. To investigate the sharp nitrogen-related lines, we also grew GaAs with double atomic-layer-doped planes and varied the distance between the two planes. When the two planes are brought close to 1 nm, two new lines, NNC and NND, appear between the two nitrogen-related lines, NNA and NNB, observed in a single nitrogen atomic-layer-doped GaAs. The NNC and NND lines are also observed in uniformly doped GaAs. Therefore, NNA and NNB originate from excitons bound to pairs of nitrogen atoms, both of which are in the (001) plane, while NNC and NND originate from those bound to pairs of nitrogen atoms, of which pairing directions are not included in the (001) plane. From the photoluminescence characteristics, distances between nitrogen atoms of a pair are estimated for each line. 相似文献
67.
Perfluorocarboxylic acids and their anions (PFCAs), such as perfluorooctanate (C7F15C(O)O?), have been generally recognized to be global pollutants and are believed to persist in the environment. Kinetic data for reactions of sulfate anion radicals (SO4?) with PFCAs are needed to evaluate the residence times of PFCAs in the environment, but no kinetic data have been reported, except for the rate constant for the reaction of SO4? with trifluoroacetate (CF3C(O)O?) (k1). In this study, using the fact that PFCAs react with SO4? to form shorter chain PFCAs, we determined rates relative to k1 of the reactions of photolytically generated SO4? with two short‐chain PFCAs, pentafluoropropionate (C2F5C(O)O?; k2) and heptafluorobutyrate (C3F7C(O)O?; k3), along with conversion ratios for conversion of C2F5C(O)O? into CF3C(O)O? (α) and conversion of C3F7C(O)O? into C2F5C(O)O? (β) and CF3C(O)O? (γ) at 298 K. Values of k1, k2, or k3 might change over the course of reaction with increasing ionic strength. Nevertheless, if the values of k1/k2, k2/k3, α, β, and γ remain almost constant during the reaction, a simple equation involving relative rates, such as k1/k2, can be used to relate the concentrations of C3F7C(O)O?, C2F5C(O)O?, and CF3C(O)O?. We compared the relative rates, such as k1/k2, and the conversion ratios determined from various experimental runs with different initial conditions to check whether relative rates and conversion ratios remained almost constant during each experimental run. The values of k1/k2, k2/k3, α, β, and γ seemed to remain almost constant, which facilitated determination of k2/k1 = 0.89 ± 0.07, k3/k1 = 0.84 ± 0.08, α = 0.88 ± 0.05, β = 0.75 ± 0.05, and γ = 0.17 ± 0.02. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 276–288, 2007 相似文献
68.
Sound attenuattion constants are calculated for the one-dimensional ferro- and antiferromagnetic systems at finite temperatures. Their frequency dependences, in both cases, turn out to be , where ωc is a “cut-off” frequency related to the three-dimensional anisotropic interactions. 相似文献
69.
70.
Hisao Watanabe 《Letters in Mathematical Physics》1991,23(1):1-9
In this Letter, we show that the local time of self-intersections ofd-dimensional Brownian motions is a generalized Brownian functional in the sense of Hida. 相似文献