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61.
The interactions of selected zirconium alloys used as special construction materials (Zr-pure, Zry-2, E-110) with the molten system of (LiF—NaF—KF)(eut.) with additions of K2ZrF6 or Na7Zr6F31 were studied. Corrosion losses of pure zirconium decrease sharply with 5 mole% addition of K2ZrF6 to (LiF—NaF—KF)(eut.). The presence of alloying additives (Sn, Nb) has a positive influence on corrosion resistance in the eutectic mixture — up to 60% increase in corrosion resistance in comparison with pure zirconium. The mass losses of pure zirconium indicate an increasing corrosion attack with increasing Na7Zr6F31 content in (LiF—NaF—KF)(eut.) mixtures. 相似文献
62.
Spin densities have been calculated by the Roothaan INDO CI method in the parametrization of Pople and Kaufman. The dependence of the spin densities on both the type and the number of configurations in CI has been followed. Results have been compared with the UHF and spin-projected UHF methods. 相似文献
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Vladim?r?Luke? Martina?Bittererová Stanislav?Biskupi? Viliam?LaurincEmail author 《Theoretical chemistry accounts》2003,109(6):316-325
The potential-energy surface for the Li(2S)–HF (? X1Σ+ interaction, where HF is kept rigid, is calculated using the supermolecular unrestricted fourth-order Møller–Plesset perturbation theory. The basis set superposition error corrected potential indicates two minima. The global minimum occurs for the bent Li...FH structure at R=1.95 Å and θ=70° with a relatively deep well of De=1,706 cm?1 and the secondary minimum is found for the linear Li...HF configuration at R=4.11 Å with a well depth ofDe=288 cm?1. A barrier of 177 cm?1 (with respect to the secondary linear minimum) separates these two minima. In this study 27 bound states of the bent Li...FH minimum and eight bound states of the linear Li...HF minimum up to the Li+HF dissociation threshold are calculated. The energy partitioning using the intermolecular perturbation theory scheme shows that the origins of the stability of the structures studied are entirely different. The global minimum is stabilised using the attractive Coulombic interaction and unrestricted Hartree–Fock deformation energy. The latter term originates from the mutual electric polarisation effects. The secondary linear minimum is mostly determined by the anisotropy of the repulsive Heitler–London exchange-penetration and attractive dispersion energies. 相似文献
65.
Viliam Krivan Karl-Heinz Theimer 《Spectrochimica Acta Part B: Atomic Spectroscopy》1997,52(14):2061-2076
A technique for the separation of 42 trace elements from up to 5 g of molybdenum and tungsten matrices was developed by means of the radiotracer technique. It is based on adsorption of the analyses on the cation exchanger Dowex 50 W x 9 from a 4% H2O2/0.01 mol 1−1 HNO3 solution followed by their elution with 15 ml of 4 mol I−1 HNO3 in the opposite flow direction. Both matrices were removed with a separation factor > 104. The separation technique was applied to the analysis of these materials by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spetrometry. For all the determination methods used, the limits of detection are given and compared with those of other methods. With inductively coupled plasma mass spectrometry, for 22 of the 30 assayed elements, limits of detection at the sub-ng g−1 level were achieved. The results are compared with those obtained by radiochemical neutron activation analysis in this work and by glow discharge mass spectrometry, secondary ion mass spectrometry, isotope dilution mass spectrometry and by solution spectrometric methods in other laboratories. 相似文献
66.
The ab initio three-dimensional potential energy surface (PES) for the weak interaction of hydrogen molecule with bromine anion is presented. The surface was obtained by the supermolecular method at the coupled cluster with single and double excitations and noniterative correction to triple excitations (CCSD(T)) level of theory. Our calculations indicate the van der Waals (vdW) system for the linear orientation at R=3.37 A with a well depth of D(e)=660.1 cm(-1). The presented PES reveals also transition state for the perpendicular orientation at R=4.22 A with a barrier of 607.1 cm(-1). The physical origin of the stability of vdW H(2) ... Br(-) structure with respect to the H(2) ... Cl(-) one was analyzed by the symmetry adapted perturbation theory based on the single determinant Hartree-Fock (HF) wave function. The separation of the interaction energy shows that the dispersion forces play slightly more important role in the stabilization of the vdW system with Br(-) than with Cl(-). 相似文献
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69.
In this paper, we present a parameter estimation procedure for a condition‐based maintenance model under partial observations. Systems can be in a healthy or unhealthy operational state, or in a failure state. System deterioration is driven by a continuous time homogeneous Markov chain and the system state is unobservable, except the failure state. Vector information that is stochastically related to the system state is obtained through condition monitoring at equidistant sampling times. Two types of data histories are available — data histories that end with observable failure, and censored data histories that end when the system has been suspended from operation but has not failed. The state and observation processes are modeled in the hidden Markov framework and the model parameters are estimated using the expectation–maximization algorithm. We show that both the pseudolikelihood function and the parameter updates in each iteration of the expectation–maximization algorithm have explicit formulas. A numerical example is developed using real multivariate spectrometric oil data coming from the failing transmission units of 240‐ton heavy hauler trucks used in the Athabasca oil sands of Alberta, Canada. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
70.
Kolivoška V Gál M Pospíšil L Valášek M Hromadová M 《Physical chemistry chemical physics : PCCP》2011,13(23):11422-11429
Facile electron transfer in molecules with one dimension greatly exceeding the other two is essential in the development of new molecular electronic devices as these molecules can serve as so-called molecular wires. In this communication the electrochemical behavior of a series of molecules with multiple extended viologen moieties has been studied. We show that the electron transfer in the shortest wire is due to reduction of two identical communicating pyridinium moieties leading to a full charge delocalization, whereas the electron transfer in molecules with n≥ 2 is due to reduction of initially non-communicating centers. This was confirmed by digital simulation of cyclic voltammograms. All studied molecules accept reversibly at least four and up to ten electrons without any long-term chemical changes, which is a prerequisite for their future application. Chemical stability of these molecules after multiple electron transfer was confirmed by in situ UV-Vis spectroelectrochemical detection. 相似文献