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V. Železny D. B. Tanner K. Kamarás L. P. Kozeeva A. A. Pavlyuk 《Zeitschrift für Physik B Condensed Matter》1995,96(3):313-318
The optical spectrum of reduced-T
c GdBa2Cu3O7– has been measured for polarizations parallel and perpendicular to theab plane. The sample was an oxygen-deficient single crystal with a large face containing thec axis. The polarized reflectance from this face was measured from 20–300 K in the spectral region from 30–3000 cm–1, with 300 K data to 30000 cm–1. Kramers-Kronig analysis was used to determine the spectral dependence of theab and thec components of the dielectric tensor. The optical properties are strongly anisotropic. Theab-plane response resembles that of other reduced-T
c materials whereas thec axis, in contrast, shows only the presence of several phonons. There is a complete absence of charge carrier response alongc aboveand belowT
c. This observation allows us to set an upper limit to the free-carrier spectral weight for transport perpendicular to the CuO2 planes.Permanent address: Institute of Physics, CSAV, Prague, Czechoslovakia 相似文献
55.
Pavlyuk A. V. Davydov V. N. Mys'kiv M. G. 《Russian Journal of Coordination Chemistry》2003,29(3):199-202
Crystals of [97N(35)]uBr2 (IV) and [97N(35)][u2Br3] (V) were prepared by ac electrochemical synthesis from uBr2, N-allylquinolinium bromide, on copper electrodes in the ethanol–benzene medium. X-ray diffraction study has shown that crystals IV and V are monoclinic: space group A21/a, a = 13.776(3) Å, b = 14.304(3) Å, c = 13.147(2) Å, = 107.90(1) Å, V = 2465(2) Å3, Z = 8 for IV and space group P21/n, a = 13.881(2) Å, b = 15.446(2) Å, c = 7.111(1) Å, = 104.64(1)°, V = 1475.0(8) Å3, Z = 4 for V. Structures IV and V are built of the N-allylquinolinium cations and different anions i.e., (CuBr2)
n-
n forming infinite chains in IV and peculiar {[CuI
4Br6]2–}
n
arranged in polymeric chains in V. In the latter case, two independent metal atoms have trigonal–pyramidal and trigonal–planar environments. In the structures of both compounds, the C=C bond of the allyl group is not involved in coordination with the Cu(I) atom. 相似文献
56.
The newly established intermetallic compound LiAg2In crystallizes in the MnCu2Al-type structure (Fm-3m, Heusler phase) with . The homogeneity range of this phase in the ternary Li-Ag-In phase diagram along the adjacent quasibinary cut Li0.25(Ag1−xInx)0.75 was determined by X-ray powder diffraction and extends from x∼0.33, Li0.25Ag0.50In0.25, up to x∼0.44, Li0.25Ag0.42In0.33. The homogeneity ranges of Heusler- and Zintl-type phases in the Li-Ag-In system are separated from each other by a broad heterogeneous region. 相似文献
57.
Volodymyr Pavlyuk Wojciech Ciesielski Beata Rozdzynska-Kielbik Grygoriy Dmytriv Helmut Ehrenberg 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):561-565
Binary and multicomponent intermetallic compounds based on lithium and p‐elements of Groups III–V of the Periodic Table are useful as modern electrode materials in lithium‐ion batteries. However, the interactions between the components in the Li–Ge–B ternary system have not been reported. The structure of tetralithium digermanium boride, Li4Ge2B, exhibits a new structure type, in the noncentrosymmetric space group R3m, in which all the Li, Ge and B atoms occupy sites with 3m symmetry. The title structure is closely related to the Mo2B5 and Li5Sn2 structure types, which crystallize in the centrosymmetric space group Rm. All the atoms in the title structure are coordinated by rhombic dodecahedra (coordination number = 14), similar to the atoms in related structures. According to electronic structure calculations using the tight‐binding–linear muffin‐tin orbital–atomic spheres approximation (TB–LMTO–ASA) method, strong covalent Ge—Ge and Ge—B interactions were established. 相似文献
58.
Volodymyr Pavlyuk Grygoriy Dmytriv Ivan Tarasiuk Hermann Pauly Helmut Ehrenberg 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):i73-i75
The new ternary lithium copper aluminide, Li12Cu16+xAl26−x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li12Cu16+xAl26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl2 and Li8Cu12+xAl6−x) and to the well known CaCu5 structure. 相似文献
59.
V. A. Nadolinnyi N. V. Chernei A. V. Sinitsyn A. A. Pavlyuk S. F. Solodovnikov 《Journal of Structural Chemistry》2008,49(5):859-864
The binary molybdate Li2Zn2(MoO4)3 of a new crystal type was characterized by EPR, optical spectroscopy, and X-ray diffraction methods. The crystals have the Pnma symmetry group and the lattice parameters a = 5.1139(5) Å, b = 10.4926(13) Å, c = 17.6445(22) Å; Z = 4. The crystals possess scintillation properties; emission is caused by the presence of impurity levels in the forbidden band. The EPR studies of the nature of the impurity centers responsible for the scintillation characteristics of the crystal showed that the centers were Cu2+ ions substituted for zinc ions in the oxygen octahedra. The directions of the main values of the g and tensors (g zz , A zz ) correspond to the direction of O-Cu-O of the oxygen octahedron distorted along the Z axis. The EPR spectra of the copper ions are described by the spin Hamiltonian with the parameters g ‖ = 2.38, g ⊥ = 2.06; A ‖ = 116 G, A ⊥ = 0 G. 相似文献
60.