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31.
32.
P. G. Thirolf D. Habs A. Henig D. Jung D. Kiefer C. Lang J. Schreiber C. Maia G. Schaller R. Schützhold T. Tajima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(2):379-389
The ultra-high fields of high-power short-pulse lasers are expected to contribute to understanding fundamental properties of the quantum vacuum and quantum theory in very strong fields. For example, the neutral QED vacuum breaks down at the Schwinger field strength of 1.3×1018 V/m, where a virtual e+e- pair gains its rest mass energy over a Compton wavelength and materializes as a real pair. At such an ultra-high field strength, an electron experiences an acceleration of aS=2×1028g and hence fundamental phenomena such as the long predicted Unruh effect start to play a role. The Unruh effect implies that the accelerated electron experiences the vacuum as a thermal bath with the Unruh temperature. In its accelerated frame the electron scatters photons off the thermal bath, corresponding to the emission of an entangled pair of photons in the laboratory frame. While it remains an experimental challenge to reach the critical Schwinger field strength within the immediate future even in view of the enormous thrust in high-power laser developments in recent years, the near-future laser technology may allow to probe the signatures of the Unruh effect mentioned above. Using a laser-accelerated electron beam (γ~300) and a counter-propagating laser beam acting as optical undulator should allow to create entangled Unruh photon pairs (i.e., signatures of the Unruh effect) with energies of the order of several hundred keV. An even substantially improved experimental scenario can be realized by using a brilliant 20 keV photon beam as X-ray undulator together with a low-energy (γ≈2) electron beam. In this case the separation of the Unruh photon pairs from background originating from linearly accelerated electrons (classical Larmor radiation) is significantly improved. Detection of the Unruh photons may be envisaged by Compton polarimetry in a 2D-segmented position-sensitive germanium detector. 相似文献
33.
Kriegel I Jiang C Rodríguez-Fernández J Schaller RD Talapin DV da Como E Feldmann J 《Journal of the American Chemical Society》2012,134(3):1583-1590
The optical properties of stoichiometric copper chalcogenide nanocrystals (NCs) are characterized by strong interband transitions in the blue part of the spectral range and a weaker absorption onset up to ~1000 nm, with negligible absorption in the near-infrared (NIR). Oxygen exposure leads to a gradual transformation of stoichiometric copper chalcogenide NCs (namely, Cu(2-x)S and Cu(2-x)Se, x = 0) into their nonstoichiometric counterparts (Cu(2-x)S and Cu(2-x)Se, x > 0), entailing the appearance and evolution of an intense localized surface plasmon (LSP) band in the NIR. We also show that well-defined copper telluride NCs (Cu(2-x)Te, x > 0) display a NIR LSP, in analogy to nonstoichiometric copper sulfide and selenide NCs. The LSP band in copper chalcogenide NCs can be tuned by actively controlling their degree of copper deficiency via oxidation and reduction experiments. We show that this controlled LSP tuning affects the excitonic transitions in the NCs, resulting in photoluminescence (PL) quenching upon oxidation and PL recovery upon subsequent reduction. Time-resolved PL spectroscopy reveals a decrease in exciton lifetime correlated to the PL quenching upon LSP evolution. Finally, we report on the dynamics of LSPs in nonstoichiometric copper chalcogenide NCs. Through pump-probe experiments, we determined the time constants for carrier-phonon scattering involved in LSP cooling. Our results demonstrate that copper chalcogenide NCs offer the unique property of holding excitons and highly tunable LSPs on demand, and hence they are envisaged as a unique platform for the evaluation of exciton/LSP interactions. 相似文献
34.
G. M. Marshall A. Adamczak J. M. Bailey J. L. Beveridge G. A. Beer J. H. Brewer V. M. Bystritsky M. P. Faifman B. M. Forster M. C. Fujiwara T. M. Huber R. Jacot-Guillarmod P. Kammel K. R. Kendall N. P. Kherani S. K. Kim P. E. Knowles A. R. Kunselman M. Maier V. E. Markushin V. S. Melezhik G. R. Mason F. Mulhauser A. Olin C. Petitjean T. A. Porcelli L. A. Schaller V. A. Stolupin J. Zmeskal 《Hyperfine Interactions》2001,138(1-4):203-211
Since the discovery that muonic deuterium at energies near a few eV could travel distances of the order of 1 mm in condensed
hydrogen, and in particular that muonic tritium and muonic deuterium could emerge from the surface of a solid hydrogen layer,
the advantages of solid targets have enabled the study of several processes important in muon catalyzed fusion. A review of
the results is presented, emphasizing the strengths and limitations of the use of solid hydrogen layer targets.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
35.
36.
Ohne Zusammenfassung
Optimization of gas-chromatographic element analysis via di(trifluoroethyl)dithiocarbamates相似文献
37.
H. Schaller und R. Neeb 《Fresenius' Journal of Analytical Chemistry》1986,323(5):469-472
Zusammenfassung Die Reaktion des Cr(VI) mit Dialkyldithiocarbamaten in saurer wäßriger Lösung wurde untersucht. Als Nebenprodukte konnten, außer im Falle des fluorierten Chelates, sauerstoffhaltige Cr(III)-Chelate nachgewiesen werden.Zur capillar-gas-chromatographischen Bestimmung des Cr(VI) erwies sich das Di(trifluorethyl)dithiocarbamat, mit Einschränkung auch das Diethyldithiocarbamat, als geeignet. Mit Hilfe des Di(trifluorethyl)dithiocarbamats ist die Bestimmung des Cr(VI) im unteren ppb-Bereich möglich.
Teil III: Fresenius Z Anal Chem 315:422
Die Untersuchungen wurden in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbands der Chemischen Industrie — Fonds der Chemie —, sowie durch das leihweise Überlassen einer Capillarsäule durch die Firma Macherey & Nagel unterstützt. 相似文献
Dialkyldithiocarbamates as reagents for the gas-chromatographic determination of metalsIV. Reaction of Cr(VI) with dialkyldithiocarbamates in aqueous solution — Application for the capillary-gas-chromatographic determination of chromium
Summary The reaction of Cr(VI) with dialkyldithiocarbamates in acid aqueous solution is investigated. Oxygen-containing Cr(III) chelates were found to be formed as byproducts, except in the case of the fluorinated chelate.For the capillary-gas-chromatographic determination of Cr(VI) di(trifluoroethyl)dithiocarbamate was suitable, with restriction also diethyldithiocarbamate. The determination of Cr(VI) was possible at the lower ppb-level with di(trifluoroethyl) dithiocarbamate.
Teil III: Fresenius Z Anal Chem 315:422
Die Untersuchungen wurden in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbands der Chemischen Industrie — Fonds der Chemie —, sowie durch das leihweise Überlassen einer Capillarsäule durch die Firma Macherey & Nagel unterstützt. 相似文献
38.
Gartner B. Ackerbauer P. Breunlich W. H. Cargnelli M. Fischer A. Kammel P. King R. Kminek G. Lauss B. Marton J. Prymas W. Steininger E. Zmeskal J. Petitjean C. Chatellard D. Egger J. -P. Jeannet E. Hartmann F. J. Kosak A. Mühlbauer M. von Egidy T. Piller C. Schaller L. A. Schellenberg L. Schneuwly H. Thalmann Y. -A. Tresch S. Werthmüller A. 《Hyperfine Interactions》1996,101(1):249-255
Muon transfer from the ground state of muonic deuterium to a helium atom proceeds mainly via the formation of a muonic molecule in an excited state. A large number of decay X rays ( 6.8 keV) from these (dµHe)* molecules were observed for the4He as well as for the3He case. The time distributions of these X rays allow the determination of the ground state transfer rate. The simultaneous employment of Ge/Si-detectors and CCDs for the same target conditions allows the determination of the branching ratio of radiative to nonradiative decay for the first time. 相似文献
39.
40.
K. Schaller R. Lenhardt V. Weber C. Euler 《Fresenius' Journal of Analytical Chemistry》1988,329(6):701-706
Summary It could be shown that the flow injection technique can be well introduced in labs which need a high sample throughput without any loss of precision. For normal labs with agrochemical tasks it is possible to adapt the proposed flow injection methods for nitrogen and phosphorus. For the determination of ammonia in juices and musts flow injection is better in precision and faster than the conventional methods. The determination of nitrate in plant extracts can be performed without any clean-up of the crude extract by introducing a dialysis cell in the normal flow injection system. For the determination of proline and arginine methods were developed for flow injection. Both are selective with a high precision and crude plant extracts can be injected for determination. Flow diagrams and equipment parameters are described. 相似文献