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61.
H. Fricke 《Fresenius' Journal of Analytical Chemistry》1956,151(2):145-146
Ohne Zusammenfassung 相似文献
62.
63.
64.
V. Meden J. Fricke C. Wöhler K. Schönhammer 《Zeitschrift für Physik B Condensed Matter》1995,99(1):357-365
We present the exact solution for the time evolution of the electron and phonon momentum distribution for a one-dimensional
polaron model with alinear electronic energy dispersion. The electron momentum distribution is shown to obey aMarkovian quantum kinetic equation. Numerical results for the polaron model are compared to the corresponding exact results, when the
negative momentum states are filled in the initial state. The presence of this Fermi sea modifies the dynamics except in the
short time regime. The different, long time dynamics might show up in comparison of hot electron relaxation of undoped and
doped semiconductors. 相似文献
65.
Using the Multi-Configuration Dirac-Fock (MCDF) method we calculate with 9 configuration state functions the correlation energy as well as the total energy of the lowestJ=0 ground state of all two-electron systems from H? to Thorium (Z=90). A comparison with experimental data, which are available only in the lowZ region, shows a very good agreement. 相似文献
66.
C. Z. Dong S. Fritzsche B. Fricke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):317-323
Recent high precision measurements on the lifetime of
the metastable 6s[3/2]2 state of atomic xenon display a
difference with previous predictions by a factor of 2–3. In the
present work, a systematic relaxation and correlation approach,
which has been developed on the basis of a widely used
multi-configuration Dirac-Fock method, is applied to study the
electric dipole allowed E1 and forbidden M1, E2 and M2 transitions
between the 5p5 6s and
5p6 configurations. We systematically include the correlation effects
which arise from all the single and double excitations from the
occupied
shells into the
(n=6–10) active sets and the relaxation effects caused by change
of the electron density between the radiative initial- and final-states. This study not only reduces greatly the existing
discrepancy in the lifetime of the 6s[3/2]2 state, but also
presents rather consistent results for both the lifetime of the
metastable 6s'[1/2]0 state and the oscillator strength of the
5p5 6s - 5p6 E1 resonant transitions. 相似文献
67.
Fricke Christian Harms Hauke Maskow Thomas 《Journal of Thermal Analysis and Calorimetry》2020,141(5):1933-1942
Journal of Thermal Analysis and Calorimetry - A sudden expansion is a classical problem which is happened in different industries such as energy conversion, environmental control, and chemical... 相似文献
68.
Matthias Wrsching Sarah‐Kristin Fricke Jn Minr Robin Niklaus Constantin Hoch 《无机化学与普通化学杂志》2019,645(3):278-283
The subvalent nitridometalate Ba6[(Mo1–xTax)N4]N0.86 was prepared from mixtures of Mo powder with Ba, Na, and Ba2N at 600 °C in Ta ampoules. It crystallizes in space group Cmcm with a = 11.672(3), b = 10.177(2) and c = 10.8729(19) Å. Its crystal structure exhibits an orthorhombically distorted Perovskite topology with [Ba6N] building units forming the ReO3‐type lattice via common vertices, and the nitridometalate anions occupying half of the available distorted cuboctahedral interstices. [MN4] anions show statistically mixed occupancy of M by MoVI and TaV. They show no notable deviation from nitridometalate anions in known ionic nitridomolybdates and ‐tantalates, and the metrics of the [Ba6N] octahedra correspond to those found in similar subvalent compounds. The nitrogen atom position centering the [Ba6N] octahedra is underoccupied. Band structure calculations corroborate the subvalent character of the compound and the two individual anionic structural building units. 相似文献
69.
Dimethylthioarsinic anhydride: a standard for arsenic speciation 总被引:1,自引:0,他引:1
Dimethylthioarsinic acid (DMTAV) has recently been identified in biological, dietary and environmental matrices. The relevance of this compound to the toxicity of arsenic in humans is unknown and further exposure assessment and metabolic studies are difficult to conduct because of the unavailability of a well characterized standard. The synthesis of DMTAV was accomplished by the reaction of dimethylarsinic acid (DMAV) with hydrogen sulfide. The initial reaction product produced is DMTAV but multiple products over the course of the reaction are also observed. Therefore, a chromatographic separation was developed to monitor the reaction progress via LC-ICP-MS. In this synthesis, conversion of DMAV to DMTAV was not taken to completion to avoid the production of side products. The product was isolated from the starting material by standard organic techniques. Single crystal diffraction demonstrated that solid DMTAV is present in the form of the oxygen-bridged dimethylthioarsinic anhydride. Dissolution of the anhydride in water produces the acid form of DMTAV and the aqueous phase DMTAV provided a characteristic molecular ion of m/z 155 by LC-ESI-MS. The synthesis and isolation of dimethylthioarsinic anhydride provides a stable crystalline standard suitable for identification, toxicological study and exposure assessment of dimethylthioarsinic acid. 相似文献
70.
The physical origin of tip-induced motion of Cu adatoms on anisotropic Cu surfaces is investigated by means of total energy calculations which are based on three different semi-empirical potentials. The calculations show that for certain tip–adatom distances the activation barrier for the adatom to move towards the tip disappears completely, whereas the barrier in the opposite direction increases and the adatom experiences an attractive force towards the tip. The general trends do not depend on the shape and chemical nature of the tip, but quantitatively there appear differences. 相似文献