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31.
The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed. 相似文献
32.
In this paper, we construct spherically symmetric solutions of the equations of compressible flow, which are important in the theory of explosion waves in air, water, and other media. Following McVittie [ 1 ], we write a general solution form, in terms of velocity potential, as a product of a function of time and a function of a similarity variable. First, we find solutions to the equations of motion and continuity without reference to adiabatic or isentropic relation. These solutions are quite general and can be applied to nonadiabatic motions, such as the motions of interstellar gas clouds that lose energy by radiation. All the solutions found by McVittie [ 1 ] have linear velocity profile with respect to distance. We introduce a nonlinear form of the velocity function containing an arbitrary function of the similarity variable. Adiabatic conditions lead to a second-order ODE, which we discuss in some detail. We relate our work to the earlier investigations of Taylor [ 2 ], McVittie [ 1 ], and Keller [ 3 ]. 相似文献
33.
D. Bazzacco F. Brandolini K. Löwenich P. Pavan C. Rossi Alvarez M. De Poli A. M. I. Haque 《Hyperfine Interactions》1990,59(1-4):125-128
Relative g-factor of the first 2+ and 4+ states have been measured with the transient field technique in156Gd and158Gd. The precession of gamma rays depopulating the levels under study were observed, after passing through thin polarized gadolinium.
The observed values agree with the predictions of the rotational model, i.c. g(4+)= g(2+), while contrasting the hypothesis that in156Gd the g-factor of the 4+ is reduced with respect to the 2+, because of rotational alignment. 相似文献
34.
The effect of replacing the hydrogen atoms in thioformaldehyde by halogen atoms (F, Cl) on the ionisation potential of the
non-bonding electron is analysed by using the Hellman-Feynman theorem, regarding the nuclear charge of the substituent as
a parameter in the many-electron Hamiltonian. The trends predicted by our theory nicely agree with the relevant ionisation
potentials computed either by applying Koopmans’ theorem or by the ΔE
SCF method. For the carbonyls, avaible experimental data indicate the reliability of our prediction. 相似文献
35.
The total synthesis of cholecalciferol an intramolecular Diels-Alder approach is described. 相似文献
36.
Summary Extensive measurements of the coefficient of electroconvective heat transfer have been carried out in gases: air, Ar, N2, O2, freon-12 and freon-22, using a single platinum wire mounted along the axis of a copper cylinder. The diameter of the cylinder
was 53 mm, while that of the wire was 0.025 mm. Electroconvective heat transfer coefficients have been measured as a function
of electric field, pressure, orientation and frequency of the applied electric field in the earth's gravitational field. The
results reveal a complicated interaction between the electric-field gradient and thermal convection. The present work indicates
that the Senftleben mechanism alone cannot account for the observed phenomena. 相似文献
37.
A new simple, sensitive and selective test for the detection of microgram amounts of aliphatic amines with diphenylcarbazide-soaked Whatman No. 1 filter paper as the detection medium is described. A feature of the study is the observation that the reaction does not take place in solution in the absence of the filter paper. 相似文献
38.
The real-space densities of a polarized strongly interacting two-component Fermi gas of 6Li atoms reveal two low-temperature regimes, both with a fully paired core. At the lowest temperatures, the unpolarized core deforms with increasing polarization. Sharp boundaries between the core and the excess unpaired atoms are consistent with a phase separation driven by a first-order phase transition. In contrast, at higher temperatures the core does not deform but remains unpolarized up to a critical polarization. The boundaries are not sharp in this case, indicating a partially polarized shell between the core and the unpaired atoms. The temperature dependence is consistent with a tricritical point in the phase diagram. 相似文献
39.
Hirata N Kroeze JE Park T Jones D Haque SA Holmes AB Durrant JR 《Chemical communications (Cambridge, England)》2006,(5):535-537
We demonstrate the formation of a charge transfer cascade at a nanostructured TiO2/dye/polymer/molecular hole transport multilayer interface. Charge recombination dynamics at this interface are shown to be retarded when the ionisation potential of the polymer layer exceeds that of the molecular hole transport layer. 相似文献
40.
Photochemical approaches to solar energy conversion are currently making rapid progress, increasing not only academic but also commercial interest in molecular-based photovoltaic solar cells. This progress has been achieved not only by increased understanding of the physics and physical chemistry of device function but also through advances in chemical and materials synthesis and processing, which now allows the design and fabrication of increasingly sophisticated device structures organised on the nanometer length scale. In this feature article, we review some progress in this field, focusing in particular upon the electron-transfer dynamics which underlie the function of dye-sensitised, nanocrystalline solar cells. The article starts by building upon the parallels between the function of such devices and the function of simple donor/acceptor molecular systems in solution. We then go on to discuss the optimisation of device function, and in particular the use of self-assembly-based strategies to control interfacial electron-transfer kinetics. 相似文献