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61.
Two Hexagonal Series of Lanthanoid(III) Oxide Fluoride Selenides: M6O2F8Se3 (M = La – Nd) and M2OF2Se (M = Nd,Sm, Gd – Ho)
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Dirk D. Zimmermann Hagen Grossholz Sarah Wolf Oliver Janka Alexander C. Müller Thomas Schleid 《无机化学与普通化学杂志》2015,641(11):1926-1933
Two hexagonal series of lanthanoid(III) oxide fluoride selenides with similar structure types can be obtained by the reaction of the components MF3, M2O3, M, and Se in sealed niobium tubes at 850 °C using CsI as fluxing agent. The compounds with the lighter and larger representatives (M = La – Nd) occur with the formula M6O2F8Se3, whereas with the heavier and smaller ones (M = Nd, Sm, Gd – Ho) their composition is M2OF2Se. For both systems single‐crystal determinations were used in all cases. The compounds crystallize in the hexagonal crystal system (space group: P63/m) with lattice parameters of a = 1394–1331 pm and c = 403–372 pm (Z = 2 for M6O2F8Se3 and Z = 6 for M2OF2Se). The (M1)3+ cations show different square antiprismatic coordination spheres with or without an extra capping fluoride anion. All (M2)3+ cations exhibit a ninefold coordination environment shaped as tricapped trigonal prism. In both structure types the Se2– anions are sixfold coordinated as trigonal prisms of M3+ cations, being first condensed by edges to generate trimeric units and then via faces to form strands running along [001]. The light anions reside either in threefold triangular or in fourfold tetrahedral cationic coordination. For charge compensation, both structures have to contain a certain amount of oxide besides fluoride anions. Since F– and O2– can not be distinguished by X‐ray diffraction, bond‐valence calculations were used to address the problem of their adjunction to the available crystallographic sites. 相似文献
62.
Recently, a density functional theory for hard particles with shape anisotropy was developed, the extended deconvolution fundamental measure theory (edFMT). We apply edFMT to hard dumbbells, arguably the simplest non-convex shape and readily available experimentally in the form of colloids. We obtain good agreement between edFMT and Monte Carlo simulations for fluids of dumbbells in a slit and for the same system under gravity. This indicates that edFMT can be successfully applied to nearly all colloidal shapes, not just for the convex shapes for which edFMT was originally derived. A theory, such as edFMT, that allows a fast and general way of mapping the phase behavior of anisotropic colloids, can act as a useful guide for the design of colloidal shapes for various applications. 相似文献
63.
A diiron(II) complex containing two μ-1,3-(κN:κO)-amidate linkages has been synthesized using the 2,2',2'-tris(isobutyrylamido)triphenylamine (H(3)L(iPr)) ligand. The resulting diiron complex, 1, reacts with dioxygen (or iodosylbenzene) to effect intramolecular C-H bond activation at the methine position of the ligand isopropyl group. The ligand-activated product, 2, has been isolated and characterized by a variety of methods including X-ray crystallography. Electrospray ionization mass spectroscopy of 2 prepared from(18)O(2) was used to confirm that the oxygen atom incorporated into the ligand framework is derived from molecular oxygen. 相似文献
64.
Jason P. Hagen 《光谱学快报》2013,46(1):58-61
Inductively coupled plasma–optical emission spectrometry was used to determine copper, iron, and zinc in both whole Crayfish and tail meat of crayfish from selected areas in southwestern Louisiana. Also included was a comparison between male and female crayfish. Results showed no significant difference between male and female crayfish and individuals from different sites. Iron was approximately four times greater in concentration for whole crayfish compared with tail meat. 相似文献
65.
A. Marshall B. Børresen G. Hagen S. Sunde M. Tsypkin R. Tunold 《Russian Journal of Electrochemistry》2006,42(10):1134-1140
Iridium-based oxides are highly active as oxygen evolving electrocatalysts in PEM water electrolyzers. In this work XRD reveals
that Ir-Sn oxides contain a single rutile phase with lattice parameters between those of pure IrO2 and SnO2. Addition of Ru leads to the synthesis of a core-shell type material due to the strong agglomeration of Ru colloids during
the preparation procedure. The shell of this material consists of an Ir-Sn-Ru oxide deficient in Ru relative to the bulk.
This leads to a decrease in the surface noble metal concentration (as found by XPS), which in turn results in a significant
reduction in electrochemically active surface area. Polarization analysis indicates that the addition of Ru can influence
the rate-determining step or mechanism by which oxygen is evolved. In a PEM water electrolysis cell, small additions of Sn
do not significantly reduce the operating performance, however larger additions cause a performance loss due to a reduction
in active surface area and increased ohmic resistance. When a pure IrO2 anode is used, a cell voltage is 1.61 V at 1 A cm−2 and 90°C.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1260–1267.
The text was submitted by the authors in English. 相似文献
66.
Absorption spectra from 4000 to 1200 cm?1 of amorphous solid water and polycrystalline ice Ic have been measured between 10 K and 140 K. Warm up and recooling of an H2O sample prepared at 10 K gives rise to both irreversible and reversible changes in the peak frequency, band width, and peak height as well as the integrated intensity of the OH stretching band. These spectral effects are related to structural differences. The structure of amorphous solid water also depends on deposition conditions. The optical constants of amorphous so water are determined at 10 K and 80 K from a Kramers-Kronig analysis of the transmission spectra taking into account reflection and interference losses. The astrophysical implication of the temperature dependence of peak frequency and band width of the 3250 cm?1 band in amorphous solid water is discussed briefly. 相似文献
67.
C. R. Hagen 《Communications in Mathematical Physics》1970,18(2):97-108
The equations of motion of a spin one particle as derived from Levy-Leblond's Galilean formulation of the Bargmann-Wigner equations are examined. Although such an approach is possible for the case of free particles, inconsistencies which closely parallel those encountered in the Bargmann-Wigner equations of special relaticity are shown to occur upon the introduction of minimal electromagnetic coupling. If, however, one considers the vector meson within the Lagrangian formalism of totally symmetric multispinors, it is found that the ten components which describe the vector meson in Minkowski space reduce to seven for the Galilean group and that in this formulation no difficulty occurs for minimal electromagnetic coupling.More generally it is demonstrated that one can replace Levy-Leblond's version of the Bargmann-Wigner equations by an alternative set which leads to the correct number of variables for the vector meson. A final extension consists in the proof that for all values of the spin the (Lagrangian) multispinor formalism implies the Bargmann-Wigner equations. Thus the problem of special relativity of seeking a Lagrangian formulation of the Bargmann-Wigner set is found to have only a somewhat trivial counterpart in the Galilean case.Research supported in part by the U.S. Atomic Energy Commission. 相似文献
68.
C.R Hagen 《Annals of Physics》1984,157(2):342-359
A gauge theory is formulated in two spatial dimensions different from all gauge theories previously known. Unlike quantum electrodynamics in such a space there does not exist an elementary photon in the model, even though a bound state having appropriate quantum numbers can be induced for weak coupling to a spinor field. Particularly noteworthy is the fact that despite the demonstrated covariance of the theory, there is an anomaly (i.e., noncanonical) term in the spatial transformation of the charge bearing field. 相似文献
69.
70.
P. Yodzis H. -J. Seifert H. Müller zum Hagen 《Communications in Mathematical Physics》1973,34(2):135-148
It is shown that spherically symmetric collapse can lead to singularities which arenot hidden within black holes.Work supported by the Deutsche Forschungsgemeinschaft. 相似文献