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From solutions of ammonium molybdate this salt was precipitated with acetone. Decomposition in air at 330 °C yields MoO3 with a specific surface area of 17 m2/g, by means of reduction with hydrogen 4.5, 4 and 3.5 valent oxides may be formed with 30, 50 and 80 m2/g, respectively. Molybdenum (VI) oxide present as a monomolecular layer on supports is much less readily reduced than unsupported MoO3. This difference reflects the interaction of Mo ions with ions of the support. The reducibilities of the various catalysts show that Mo(VI) oxides interact far less with SiO2 than with Al2O3, CeO2 and ZrO2. This is also reflected in the rates of 2-propanol decomposition on these catalysts, the activities on MoOx and on MoOx–SiO2 being much higher than on the other catalysts.
. 330°C MoO3 17 2/; 4,5,4 3,5, 30, 50 80 2/, . (VI), , , MoO3 . Mo . , Mo(VI) SiO2, Al2O3, CeO2 n ZrO2. 2- . MoOx MoOx–SiO2 , .相似文献
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Nucleation processes in the binary water-sodium chloride system are investigated in the sense of the classical nucleation theory (CNT). The CNT is modified to be able to handle the electrolytic nature of the system and is employed to investigate the acceleration of the nucleation process due to the presence of sodium chloride in the steam. This phenomenon, frequently observed in the Wilson zone of steam turbines, is called early condensation. Therefore, the nucleation rates of the water-sodium chloride mixture are of key importance in the power cycle industry. 相似文献
87.
Peter Robrish Jing Xu Shigeki Kobayashi Pavlos G. Savvidis Borys Kolasa Greg Lee Dan Mars S. James Allen 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):325
Bloch oscillation in electrically biased semiconductor superlattices offer broadband terahertz gain from DC up to the Bloch frequency or Stark splitting. Useful gain up to 2–3 THz can provide a basis for solid-state electronic oscillators operating at 10 times the frequency of existing devices.A major stumbling block is the inherent instability of the electrically biased doped superlattices to the formation of static or dynamic electric field domains. To circumvent this, we have fabricated super-superlattices in which a large superlattice is punctuated with heavily doped regions. The short superlattice sections have subcritical “nL” products.Room temperature, terahertz photon-assisted transport in short InGaAs/InAlAs superlattice cells allows us to determine the Stark ladder splitting as the superlattice is electrically biased and confirms the absence of electric field domains in short structures.Absorption of radiation from 1.5 to 2.5 THz by electrically biased InAs/AlSb super-superlattices exhibit a crossover from loss to gain as the Stark ladder is opened. Measurements are carried out at room temperature in a novel planar terahertz waveguide defined by photonic band gap sidewalls and loaded with an array of electrically biased super-superlattices. The frequency-dependent crossover voltage indicates 80% participation of the super-superlattice. 相似文献
88.
Hubert Bray Sean Hayward Marc Mars Walter Simon 《Communications in Mathematical Physics》2007,272(1):119-138
Motivated by the conjectured Penrose inequality and by the work of Hawking, Geroch, Huisken and Ilmanen in the null and the
Riemannian case, we examine necessary conditions on flows of two-surfaces in spacetime under which the Hawking quasilocal
mass is monotone. We focus on a subclass of such flows which we call uniformly expanding, which can be considered for null
as well as for spacelike directions. In the null case, local existence of the flow is guaranteed. In the spacelike case, the
uniformly expanding condition leaves a 1-parameter freedom, but for the whole family, the embedding functions satisfy a forward-backward
parabolic system for which local existence does not hold in general. Nevertheless, we have obtained a generalization of the
weak (distributional) formulation of this class of flows, generalizing the corresponding step of Huisken and Ilmanen’s proof
of the Riemannian Penrose inequality. 相似文献
89.
Duhme-Klair AK Vollmer G Mars C Fröhlich R 《Angewandte Chemie (International ed. in English)》2000,39(9):1626-1628
90.
The cross sections and transverse spin asymmetries in the hard exclusive electroproduction of decuplet baryons are calculated in the large N(c) limit and found to be comparable to that of octet baryons. Large N(c) selection rules for the production amplitudes are derived, leading to new sensitive tests of the spin aspects of the QCD chiral dynamics both in the nonstrange and strange sectors. Importance of such studies for the reliable extraction of the pion form factor from pion electroproduction is explained. 相似文献