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51.
Protoporphyrin IX‐Functionalized AgSiO2 Core–Shell Nanoparticles: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production 下载免费PDF全文
Marjorie Lismont Laurent Dreesen Benoît Heinrichs Carlos A. Páez 《Photochemistry and photobiology》2016,92(2):247-256
Metal‐enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the viewpoint of dye fluorescence and photoactivity. Herein, protoporphyrin IX (PpIX) is grafted onto the surface of silver core silica shell NPs in order to investigate the effect of silver (Ag) localized surface plasmon resonance (LSPR) on PpIX fluorescence and PpIX singlet oxygen (1O2) production. Using two Ag core sizes, we report a systematic study of these photophysical processes as a function of silica (SiO2) spacer thickness, LSPR band position and excitation wavelength. The excitation of Ag NP LSPR, which overlaps the PpIX absorption band, leads to the concomitant enhancement of PpIX fluorescence and 1O2 production independently of the Ag core size, but in a more pronounced way for larger Ag cores. These enhancements result from the increase in the PpIX excitation rate through the LSPR excitation and decrease when the distance between PpIX and Ag NPs increases. A maximum fluorescence enhancement of up to 14‐fold, together with an increase in photogenerated 1O2 production of up to five times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating. 相似文献
52.
A least-squares spectral collocation scheme for the Stokes and incompressible Navier–Stokes equations is proposed. The original domain is decomposed into quadrilateral subelements and on the element interfaces continuity of the functions is enforced in the least-squares sense. The collocation conditions and the interface conditions lead to overdetermined systems. These systems are directly solved by QR decomposition of the underlying matrices. By numerical simulations it is shown that the direct method leads to better results than the approach with normal equations. Furthermore, it is shown that the condition numbers can be reduced by introducing the Clenshaw–Curtis quadrature rule for imposing the average pressure to be zero. Finally, our scheme is successfully applied to the regularized and lid-driven cavity flow problems. 相似文献
53.
J. Heinrichs 《Solid State Communications》1982,44(6):897-900
A simple model in which electrons are assumed to be specularly reflecting on a plane located a distance u above the boundary of a homogeneous metallic region is proposed for studying dynamical properties of metal surfaces. This model is believed to incorporate essential effects of the inhomogeneity of a pure jellium surface in a new way. It leads to a strong reduction of hydrodynamic dispersion effects for long wavelengths surface plasmons, in agreement with experiment and with various previous calculations. The model is also applied to surface phonons and exact numerical dispersion curves for both surface phonons and plasmons at arbitrary wavelengths are presented. 相似文献
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J. Heinrichs 《Zeitschrift für Physik B Condensed Matter》1996,102(1):137-144
Using an earlier density matrix formalism in momentum space we study the motion of a particle in a time-dependent random potential with a finite correlation time τ, for 0 < t ? τ. Within this domain we consider two subdomains bounded by kinetic time scales (t c 2 = 2m? -1 c 2, c 2 = σ 2, ξ 2, σξ, with 2σ the width of an initial wavepacket and the correlation length of the gaussian potential fluctuations), where we obtain power law scaling laws for the effect of the random potential in the mean squared displacement 〈x 2〉 and in the mean kinetic energy 〈E kin〉. At short times, ? min (t σ 2, 1/2t ξ 2), 〈x 2〉 and 〈E kin〉 scale classically as t 4 and t 2, respectively. At intermediate times, t σξ ? t ? 2t σ 2 and 1/2t ξ 2 ? t ? t σξ, these quantities scale quantum mechanically as t 3/2 and as √t, respectively. These results lie in the perspective of recent studies of the existence of (fractional) power law behavior of 〈x 2〉 and 〈E kin〉 at intermediate times. We also briefly discuss the scaling laws for 〈x 2〉 and 〈E kin〉 at short times in the case of spatially uncorrelated potential. 相似文献
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58.
Enantioselective recognition of a chiral quaternary ammonium ion by C3 symmetric cyclic hexapeptides
Heinrichs G Vial L Lacour J Kubik S 《Chemical communications (Cambridge, England)》2003,(11):1252-1253
C3 Symmetric cyclic hexapeptides containing alternating L-proline and 3-aminobenzoic acid derivatives as subunits possess different affinities towards the two enantiomers of the N,N,N-trimethyl-1-phenylethyl ammonium cation. 相似文献
59.
J. Heinrichs 《Solid State Communications》1973,12(3):167-170
The hydrodynamic model of the electron gas is used to study the surface-plasmon dispersion relation for diffuse reflection of electrons at the surface. A previous treatment is generalized to the case of a metal bounded by a dielectric medium. The results obtained for the dispersion and for the Landau-damping are consistent with a recent analysis of ILEED data for Al. 相似文献
60.
H. Heinrichs 《Fresenius' Journal of Analytical Chemistry》1979,294(5):345-351
Summary The analysis of bismuth, cadmium and thallium in rock samples can be performed by flameless atomic absorption spectrometry, after separation and preconcentration by a volatilization technique. This method has the major advantage that small amounts of substance can be used with a minimum consumption of chemicals, so that sources of contamination are reduced. The detection limit for Bi and Tl is about 1 ppb and for Cd about 0.1 ppb in the rock. Depending on the content in the rock samples, the relative standard deviation is between 2 and 30%. Several attempts have been made to determine the yields of Bi, Cd and Tl from synthetic and natural samples.
Bestimmung von Wismut, Cadmium und Thallium in 33 internationalen Standard-Gesteinsproben durch fraktionierte Destillation in Verbindung mit flammenloser AAS
Zusammenfassung Die Bestimmung von Wismut, Cadmium und Thallium in Gesteinen kann mit der flammenlosen Atomabsorptions-Spektroskopie nach verdampfungsanalytischer Abtrennung erfolgen. Die Verdampfungsnalyse hat den Vorteil, daß bei geringem Reagentienverbrauch kleine Mengen analysiert werden können. Die Gefahr der Einschleppung von Verunreinigungen wird erheblich vermindert. Die Nachweisgrenze bezogen auf die Probe beträgt für Wismut und Thallium ca. 1 ppb und für Cadmium ca. 0.1 ppb. In Abhängigkeit von der Konzentration liegt die relative Standardabweichung zwischen 2 und 30 %. An synthetischen und natürlichen Proben sind die Ausbeuten an diesen Elementen bestimmt worden.相似文献