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41.
V. I. Kochubei Yu. G. Konyukhova K. E. Gyunsburg 《Journal of Applied Spectroscopy》2002,69(2):265-269
It is shown that xray spectral methods — those of EXAFS and XEOL spectroscopy — allow determination both of the structure of inherent or impurity centers of luminescence in alkalihalide crystals and investigation of the dynamics of their change under the action of ionizing radiation. The methods are noted for high sensitivity. The possibilities of the methods are demonstrated for KBr, NaCl:Ni, and NaCl:Ni,Cu crystals taken as an example. New data on the structures of different luminescence centers investigated and dynamics of their change are obtained. 相似文献
42.
Ressler T 《Analytical and bioanalytical chemistry》2003,376(5):584-593
Time-resolved X-ray absorption spectroscopy (TR-XAS) possesses excellent capabilities to reveal quantitative phase composition and average valence together with the evolution of the local structure of a system under dynamic reaction conditions. The work discussed here focused on time-resolved in-situ XAS investigations aiming, first, at understanding structural evolution under dynamic conditions and, second, at revealing properties of the system studied not available from investigations under stationary conditions. Hence, not only was the local structure of a material studied under reaction conditions, but characteristic properties of the reaction, such as reaction intermediates or the kinetics of the reaction, were also elucidated. The solid–gas reactions presented here clearly demonstrate the potential of TR-XAS investigations to extend the suitability of XAS for in-situ studies in solid-state chemistry to investigations under dynamic conditions. 相似文献
43.
N.L. Saini A. Lanzara A. Bianconi H. Oyanagi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):257-261
Instantaneous in-plane Cu-O bond distribution in the Bi2Sr2CaCu2O8+β (Bi2212) superconductor has been investigated by high k-resolution Cu K-edge extended X-ray absorption fine structure (EXAFS) measured with polarized vector parallel to the two
orthogonal Cu-O-Cu bonds of the CuO2 square plane. The results show an anisotropic Cu-O distribution in the two directions and provide further information on
the local atomic displacements in the lattice-charge stripes.
Received 5 June 2000 相似文献
44.
U. Vainio K. Pirkkalainen K. Kisko G. Goerigk N. E. Kotelnikova R. Serimaa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):93-101
Microcrystalline cellulose is a porous natural material which
can be used both as a support for nanoparticles and as a reducer of metal ions.
Cellulose supported nanoparticles can act as catalysts in many reactions.
Cu, CuO, and Cu2O particles were prepared in microcrystalline cellulose
by adding a solution of copper salt
to the insoluble cellulose matrix and by reducing the copper ions
with several reducers.
The porous nanocomposites were studied using anomalous small angle X-ray
scattering (ASAXS), X-ray absorption spectroscopy, and X-ray diffraction.
Reduction of Cu2+ with cellulose in ammonium hydrate medium
yielded crystalline CuO nanoparticles and
the crystallite size was about 6–20 nm irrespective of
the copper concentration. The size distribution of the CuO particles
was determined with ASAXS measurements and
coincided with the crystallite sizes.
Using sodium borohydrate or hydrazine sulfate as a reducer
both metallic Cu and Cu2O nanoparticles
were obtained and the crystallite size and the oxidation state
depended on the amount of reducer. 相似文献
45.
J.A. Sans J.F. Snchez-Royo J. Pellicer-Porres A. Segura E. Guillotel G. Martinez-Criado J. Susini A. Muoz-Pez V. Lpez-Flores 《Superlattices and Microstructures》2007,42(1-6):226
In this paper, we investigate the Co site configuration in Zn1−xCoxO thin films by means of different spectroscopic techniques. Thin films were prepared by pulsed laser deposition with Co proportion from 1% to 30%. The Co 2p doublet observed in the X-ray photoelectron spectra exhibits the spin–orbit splitting and shake-up satellites typical of Co+2 ionization states. X-ray absorption spectra at the Co K-edge, taken in fluorescence mode, unambiguously show that Co atoms are in tetrahedral configuration substituting for Zn over the whole composition range. Optical absorption spectra provide further evidence of the tetrahedral coordination of Co cations, both through the internal transitions in the Co 3d shell and through the shift to higher energies of the band-to-band absorption edge with the increase of the Co proportion. 相似文献
46.
47.
A. Stephen K. Hashmi Prof. Dr. Christian Lothschütz Dipl.‐Chem. Martin Ackermann Dipl.‐Chem. René Doepp Dipl.‐Chem. Sankaran Anantharaman Benjamin Marchetti Dipl.‐Chem. Helmut Bertagnolli Prof. Dr. Frank Rominger Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(27):8012-8019
Gold complexes were prepared and investigated as catalysts for the oxidative esterification of aldehydes. Stabilisation by pyridine ligands gave good conversions and the in situ extended X‐ray absorption fine structure (EXAFS) study of the reactions indicated that the reaction mixtures contained only mononuclear gold species. Thus, this is the first proof for a homogeneous gold‐catalysed oxidation reaction; the presence of nanoparticles could be excluded experimentally. 相似文献
48.
49.
50.
Marcus Walter Joseph Somers Boris Brendebach 《Journal of solid state chemistry》2009,182(12):3305-12445
Yttria stabilised zirconia (YSZ) based (Zr,Y,U)O2−x and (Zr,Y,Np)O2−x solid solutions with 6 and 20 mol% actinide were prepared with Y/Zr ratios ranging from 0.2 to 2.0 to investigate uranium and neptunium oxidation behaviour depending on the oxygen vacancies in the defect fluorite lattice. Sintering at 1600 °C in Ar/H2 yields a cubic, fluorite-type structure with U(IV) and Np(IV). Annealing (Zr,Y,U)O2−x with Y/Zr=0.2 at 800 °C in air results in a tetragonal phase, whereas (Zr,Y,U)O2−x with higher Y/Zr ratios and (Zr,Y,Np)O2−x retain the cubic structure. XANES and O/M measurements indicate mixed U(V)-U(VI) and Np(IV)-Np(V) oxidation states after oxidation. Based on X-ray diffraction, O/M and EXAFS measurements, different oxidation mechanisms are identified for U- and Np-doped stabilised zirconia. In contrast to U, excess oxygen vacancies are needed to oxidise Np in (Zr,Y,Np)O2−x as the oxidation process competes with Zr for oxygen vacancies. As a consequence, U(VI) and Np(V) can only be obtained in stabilised zirconia with Y/Zr=1 but not in YSZ with Y/Zr=0.2. 相似文献