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We have used phosphorescence from erythrosin B (tetraiodofluorescein) dispersed in amorphous thin films of maltose and maltitol at mole ratios of 0.8:10(4) dye:sugar to monitor the molecular mobility of these matrixes over the temperature range from -25 to over 110 degrees C. Analysis of the emission peak frequency and bandwidth (full width at half-maximum) and time-resolved intensity decay parameters provided information about thermally activated modes of matrix mobility that enhanced the rate of dipolar relaxation around the triplet state and the rate of intersystem crossing to the ground state (k(TS0)). Detectable dipolar relaxation began in the glassy state about 50 degrees C below T(g) in both maltose and maltitol; the relaxation rate, however, while 3-4 orders of magnitude slower than literature values for the beta relaxation determined from dielectric relaxation, had an activation energy only 2-fold smaller. Dipolar relaxation was further enhanced in the melt above T(g); the dipolar relaxation rates in the melt scaled nearly exactly with rates for the alpha relaxation determined from dielectric relaxation. Intensity decays were well fit using a stretched exponential decay function in which the lifetime (tau) and the stretching exponent (beta) were the physically significant parameters. In maltose, the magnitude of k(TS0) was essentially constant in the glass and increased dramatically at the T(g); in maltitol k(TS0) increased moderately at T(g) = -50 degrees C and more dramatically in the melt at T(g) = +20 degrees C. The value of k(TS0) in maltose:maltitol mixtures was significantly smaller than that seen in pure maltose and maltitol, suggesting that specific interactions decreased the mobility of the mixed sugar matrix; this phenomenon was comparable to the antiplasticization seen in mixtures of small molecule plasticizers with synthetic polymers and starch. The extent of inhomogeneous broadening and dynamic heterogeneity were essentially constant in the glass and increased dramatically in maltose and more gradually in maltitol at the glass transition. 相似文献
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Irina O. Zhuravel' Sergiy M. Kovalenko Alexandre V. Ivachtchenko Valentin P. Chernykh Pavlo E. Shinkarenko 《Journal of heterocyclic chemistry》2004,41(4):517-524
An efficient two‐step synthesis of novel 3‐(5‐amino‐[1,3,4]thiadiazol‐2‐yl)‐2H‐pyrano[2,3‐c]pyridine‐2‐ones was developed. In the first step, a new 2H‐pyrano[2,3‐c]pyridine‐3‐carboxamide 5 was prepared by Knoevenagel condensation of pyridoxal hydrochloride with cyanoacetamide. In the second step, the reaction of carboxamide 5 with a series of N4‐substituted thiosemicarbazides yielded a library of 35 dis crete compounds 8 {1–35} in high yields. The intermolecular recyclization mechanism leading to these products is discussed. 相似文献
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Some preliminary results of the influence of the cyclotron harmonic damping of lower hybrid waves by thermonuclearly produced alpha-particles are presented. Recently, the usefulness of the lower hybrid current drive (LHCD) in reactor regime was doubted in connection with this effect. The quasilinear change of the slope of the alpha-particle distribution function is taken into account. Analytical estimates are obtained showing that at a sufficiently high wave energy density the power absorped by alpha-particles saturates (in the approximation used). For the parameters of a hybrid reactor, the saturated power was found much lower than that computed from the linear theory. It seems, therefore, that, at least for hybrid reactor conditions, the alphaparticles need not represent a serious obstacle to LHCD. Some further aspects of this effect are discussed.The authors are grateful to Drs. R. Klima, V. A. Petrílka and J. Preinhealter for valuable discussions. 相似文献
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Dr. Stephan K. Pedersen Viktor B. R. Pedersen Dr. Fadhil S. Kamounah Line M. Broløs Dr. Glib V. Baryshnikov Dr. Rashid R. Valiev Dr. Khrystyna Ivaniuk Prof. Pavlo Stakhira Prof. Boris Minaev Dr. Nataliya Karaush-Karmazin Prof. Hans Ågren Prof. Michael Pittelkow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11609-11617
A soluble, green-blue fluorescent, π-extended azatrioxa[8]circulene was synthesized by oxidative condensation of a 3,6-dihydroxycarbazole and 1,4-anthraquinone by using benzofuran scaffolding. This is the first circulene to incorporate anthracene within its carbon framework. Solvent-dependent fluorescence and bright green electroluminescence accompanied by excimer emission are the key optical properties of this material. The presence of sliding π-stacked columns in the single crystal of dianthracenylazatrioxa[8]circulene is found to cause a very high electron-hopping rate, thus making this material a promising n-type organic semiconductor with an electron mobility predicted to be around 2.26 cm2 V−1 s−1. The best organic light-emitting diode (OLED) device based on the dianthracenylazatrioxa[8]circulene fluorescent emitter has a brightness of around 16 000 Cd m−2 and an external quantum efficiency of 3.3 %. Quantum dot-based OLEDs were fabricated by using dianthracenylazatrioxa[8]circulene as a host matrix material. 相似文献
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Computational Management Science - Lift-and-project (L &P) cuts are well-known general 0–1 programming cuts which are typically deployed in branch-and-cut methods to solve MILP... 相似文献
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Pavlo?I.?Stakhira Georgij?L.?Pakhomov Vlad?V.?Cherpak Dmitro?Volynyuk Grzegorz?Luka Marek?Godlewski El?bieta?Guziewicz Zenon?Yu.?Hotra 《Central European Journal of Physics》2010,8(5):798-803
The introduction of an ultrathin zinc oxide (ZnO) layer formed by the atomic layer deposition (ALD) technique was found to
improve the operation parameters of nickel phthalocyanine (NiPc) based photovoltaic cells with a transparent bottom electrode,
indium tin oxide (ITO). This improvement is attributed to several reasons, such as I) increase of photovoltaic yield in ITO/p-NiPc/n-ZnO/Al cells incorporating a hybrid heterojunction as compared to single-layer ITO/NiPc/Al cells, II) enhancement of the
overall spectral response in the double-layer cells and III) extension of long-term operational stability. 相似文献
59.
Pavlo Solokha Serena De Negri Volodymyr Pavlyuk Adriana Saccone 《Solid State Sciences》2009,11(4):801-811
Single crystals of the Y5Cu5Mg8, Y5Cu5Mg13, Y5Cu5Mg16 and YCuMg4 compounds were synthesized by heating in a resistance furnace evacuated quartz vials containing Ta-crucibles with element pieces. SEM-EDXS analyses were performed to check phases composition. The structures were refined from X-ray single crystal diffraction data. Y5Cu5Mg8, Y5Cu5Mg13 and Y5Cu5Mg16 represent new structure types: Y5Cu5Mg8 – orthorhombic, Pmma, oP36, a = 2.63723(15), b = 0.40066(2), c = 0.74115(6) nm, Z = 2, wR2 = 0.0597, 939 F2 values, 60 variables; Y5Cu5Mg13 – orthorhombic, Cmcm, oS92, a = 0.40973(2), b = 1.92794(8), c = 2.57907(11) nm, Z = 4, wR2 = 0.1134, 1208 F2 values, 75 variables; Y5Cu5Mg16 – orthorhombic, Cmcm, oS104, a = 0.41360(8), b = 1.9239(4), c = 2.9086(6) nm, Z = 4, wR2 = 0.0760, 1383 F2 values, 84 variables. YCuMg4 crystallizes in the TbCuMg4 structure type (Cmmm, oS48, a = 1.35754(4), b = 2.03153(6), c = 0.39060(1) nm, Z = 8, wR2 = 0.0401, 661 F2 values, 45 variables). The crystal chemistry of these two-layer structures is comparatively discussed. Majority of novel compounds were characterized as members of inhomogeneous 2D intergrowth structure series of R5M5X5, X4 (Mg4) and empty Mg octahedra building blocks of general formula R5kM5kX5k + 4l + m. The common pentagonal prism derivative structural fragments around the most electropositive yttrium atoms were outlined in all these intermetallics. 相似文献
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