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排序方式: 共有93条查询结果,搜索用时 15 毫秒
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D. Valenti L. Schimansky-Geier X. Sailer B. Spagnolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):199-203
The dynamics of a spatially extended system of two competing
species in the presence of two noise sources is studied. A
correlated dichotomous noise acts on the interaction parameter and
a multiplicative white noise affects directly the dynamics of the
two species. To describe the spatial distribution of the species
we use a model based on Lotka-Volterra (LV) equations. By writing
them in a mean field form, the corresponding moment equations for
the species concentrations are obtained in Gaussian approximation.
In this formalism the system dynamics is analyzed for different
values of the multiplicative noise intensity. Finally by comparing
these results with those obtained by direct simulations of the
time discrete version of LV equations, that is coupled map lattice
(CML) model, we conclude that the anticorrelated oscillations of
the species densities are strictly related to non-overlapping
spatial patterns. 相似文献
4.
It is shown that the renormalized finite temperature effective potential for continuumSU(2) Yang-Mills theory develops a non-perturbative minimum for sufficiently strong coupling, i.e. below a critical temperature. The corresponding phase can be the candidate for the confining phase of the continuum theory and becomes energetically favoured basicly due to the decay of theA 0 condensate into three gluons. 相似文献
5.
Herbert Schneckenburger Michael H. Gschwend Wolfgang S. L. Strauss Reinhard Sailer Rudolf Steiner 《Journal of fluorescence》1997,7(1):3-10
Spectroscopic and microscopic methods for probing mitochondrial malfunction were established using cultivated endothelial
cells from the calf aorta and various inhibitors of the respiratory chain, which is located at the inner mitochondrial membrane.
Time-gated fluorescence spectroscopy was used to measure autofluorescence of the coenzyme NADH as well as “energy transfer
efficacy” from excited NADH molecules (energy donor) to the mitochondrial marker rhodamine-123 (energy acceptor). Autofluorescence
usually exhibited a weak increase after specific inhibition of enzyme complexes of the respiratory chain. In contrast, a pronounced
increase in energy transfer efficacy was observed after inhibition of the same enzyme complexes. The detection of donor (NADH)
and acceptor (R123) fluorescence in different nanosecond time gates following the exciting laser pulses enhances selectivity
and improves quantification of energy transfer measurements. Therefore, timegated energy transfer spectroscopy is suggested
to be an appropriate tool for probing mitochondrial malfunction. 相似文献
6.
The mechanism of the ferroelectric transition of pure and rubidium-doped ammonium sulfate is investigated by means of Raman, Brillouin and dielectric measurements. The study contributes to spectroscopic evidences of temperature anomalies of lattice vibrations in the paraelectric and ferroelectric range. The different behaviour of rubidium-doped crystals with respect to their dielectric and elastic properties at the transition is interpreted as an indication that different order parameters might become active in this first order transformation. 相似文献
7.
G. Heidecke G. Stork J. G. Schindler M. v. Gülich W. Schmid H. Maier H. -O. Lindt und D. Sailer 《Fresenius' Journal of Analytical Chemistry》1980,301(5):406-409
Zusammenfassung Für die Na+-, K+- und Ca2+ -Bestimmung mit ionenselektiven Diskelektroden im medizinischen Bereich empfiehlt sich die Zweipunkteichung. Die mit diesem Verfahren erzielbare Reproduzierbarkeit wird theoretisch aufgrund des Ablesefehlers am Meßinstrument berechnet und mit experimentellen Werten verglichen. Die theoretisch berechneten und experimentellen Standardabweichungen liegen für 1-wertige Ionen bei 0,3 % und für 2-wertige bei 0,6 %. Die Genauigkeit wird nicht durch die Elektroden, sondern die gegenwärtig verfügbaren Meßgeräte begrenzt.
On the reproducibility of Na+-, K+- and Ca2+-selective disc electrodes as dependent on the indicating error of the potential measuring device
Summary In clinical analysis it is recommendable to use a two-point calibration for the determination of Na+, K+ and Ca2+ ions by ion-selective disc electrodes. The accuracy, which can be obtained by this calibration method, is treated theoretically, and the results are compared with experimental data. Theoretical and experimental standard deviations are in very good agreement, with 0.3 % for Na+ and K+ and 0.6 % for Ca2+. The precision is limited by the measuring instrument and not by the disc electrodes.
Wir danken dem Fonds der Chemischen Industrie, dem Bundesministerium für Forschung und Technologie der Bundesrepublik Deutschland und der Dr. E. Fresenius KG, Bad Homburg v.d.H., für die Unterstützung der Arbeiten. 相似文献
8.
1-Hydroxy-3,3-dimethylindolin-2-ones (2) formed by intramolecular photocyclisation of o-nitro-t-butylbenzenes (1) are oxidized to aminyloxides (4a-g). Their ESR spectra are reported and discussed. 相似文献
9.
A good knowledge of the luminosity spectrum is mandatory for many measurements at future $\mathrm {e}^{+}\mathrm {e}^{-}$ colliders. As the beam-parameters determining the luminosity spectrum cannot be measured precisely, the luminosity spectrum has to be measured through a gauge process with the detector. The measured distributions, used to reconstruct the spectrum, depend on Initial State Radiation, cross-section, and Final State Radiation. To extract the basic luminosity spectrum, a parametric model of the luminosity spectrum is created, in this case the spectrum at the 3 TeV compact linear collider. The model is used within a reweighting technique to extract the luminosity spectrum from measured Bhabha event observables, taking all relevant effects into account. The centre-of-mass energy spectrum is reconstructed within 5 % over the full validity range of the model. The reconstructed spectrum does not result in a significant bias or systematic uncertainty in the exemplary physics benchmark process of smuon pair production. 相似文献
10.
Ammer J Sailer CF Riedle E Mayr H 《Journal of the American Chemical Society》2012,134(28):11481-11494
UV irradiation (266 or 280 nm) of benzhydryl triarylphosphonium salts Ar(2)CH-PAr(3)(+)X(-) yields benzhydryl cations Ar(2)CH(+) and/or benzhydryl radicals Ar(2)CH(?). The efficiency and mechanism of the photo-cleavage were studied by nanosecond laser flash photolysis and by ultrafast spectroscopy with a state-of-the-art femtosecond transient spectrometer. The influences of the photo-electrofuge (Ar(2)CH(+)), the photo-nucleofuge (PPh(3) or P(p-Cl-C(6)H(4))(3)), the counterion (X(-) = BF(4)(-), SbF(6)(-), Cl(-), or Br(-)), and the solvent (CH(2)Cl(2) or CH(3)CN) were investigated. Photogeneration of carbocations from Ar(2)CH-PAr(3)(+)BF(4)(-) or -SbF(6)(-) is considerably more efficient than from typical neutral precursors (e.g., benzhydryl chlorides or bromides). The photochemistry of phosphonium salts is controlled by the degree of ion pairing, which depends on the solvent and the concentration of the phosphonium salts. High yields of carbocations are obtained by photolyses of phosphonium salts with complex counterions (X(-) = BF(4)(-) or SbF(6)(-)), while photolyses of phosphonium halides Ar(2)CH-PPh(3)(+)X(-) (X(-) = Cl(-) or Br(-)) in CH(2)Cl(2) yield benzhydryl radicals Ar(2)CH(?) due to photo-electron transfer in the excited phosphonium halide ion pair. At low concentrations in CH(3)CN, the precursor salts are mostly unpaired, and the photo-cleavage mechanism is independent of the nature of the counter-anions. Dichloromethane is better suited for generating the more reactive benzhydryl cations than the more polar and more nucleophilic solvents CH(3)CN or CF(3)CH(2)OH. Efficient photo-generation of the most reactive benzhydryl cations (3,5-F(2)-C(6)H(3))(2)CH(+) and (4-(CF(3))-C(6)H(4))(2)CH(+) was only achieved using the photo-leaving group P(p-Cl-C(6)H(4))(3) and the counter-anion SbF(6)(-) in CH(2)Cl(2). The lifetimes of the photogenerated benzhydryl cations depend greatly on the decay mechanisms, which can be reactions with the solvent, with the photo-leaving group PAr(3), or with the counter-anion X(-) of the precursor salt. However, the nature of the photo-leaving group and the counterion of the precursor phosphonium salt do not affect the rates of the reactions of the obtained benzhydryl cations toward added nucleophiles. The method presented in this work allows us to generate a wide range of donor- and acceptor-substituted benzhydryl cations Ar(2)CH(+) for the purpose of studying their electrophilic reactivities. 相似文献