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51.
52.
Treatment of conditioned seeds of four isolates of Striga hermonthica and one isolate of Striga aspera with various concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), caused complex stimulation of germination patterns. GR 24, the strigol analogue served as a positive control and its stimulatory activity was comparable to that of ACC. When conditioned Striga seeds were treated with negative control that did not contain ACC, the stimulatory effect was lost. Overall, the germination data suggested a hormonal mode of action by ACC, which involves indirect stimulation of biosynthesis of ethylene that then triggers seed germination. The various mechanisms that have been proposed for the chemical and biological oxidation of ACC to generate ethylene are discussed. 相似文献
53.
E. Ploetz S. Laimgruber S. Berner W. Zinth P. Gilch 《Applied physics. B, Lasers and optics》2007,87(3):389-393
A novel type of non-linear Raman microscopy, femtosecond stimulated Raman microscopy (FSRM), is introduced. It employs femtosecond
white light pulses and intense picosecond pulses which are derived from a femtosecond laser/amplifier system. The pulses are
coupled into a microscope set-up and induce a stimulated Raman process at the focus. The Raman interaction spectrally modulates
the white light. These modulations are read-out in multi-channel fashion and allow recording of a complete Raman spectrum
of the focal region. By raster-scanning the sample, complete Raman images can be obtained. Raman images of polystyrene beads
in water demonstrate the feasibility of the approach.
PACS 42.65.Dr; 42.30.Va; 42.65.Re 相似文献
54.
Yevgeny M. Paransky Alexander I. Berner Irena Y. Gotman Elazar Y. Gutmanas 《Mikrochimica acta》2000,134(3-4):171-177
The combination of energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques in scanning
electron microscope was employed to characterize the reacted interface between Ti matrix and AlN particles. Due to the high
localization of EDS and EBSD, representative measurements of chemical composition and reliable determination of the crystal
structure were possible for each phase in the reaction zone with complex morphology. The TiN1−x (cubic, NaCl type), Ti3AlN (cubic, perovskite type) and Ti-rich Ti3 Al (hexagonal, Ni3Sn type) phases were identified in the reaction zone after annealing at 1100 °C. EDS+EBSD combination is an efficient tool
for phase analysis at the interface in reactive multicomponent systems.
Received August 21, 1999. Revision November 21, 1999. 相似文献
55.
56.
The paper investigates the effects of heat transfer in MHD flow of viscoelastic stratified fluid in porous medium on a parallel plate channel inclined at an angle θ. A laminar convection flow for incompressible conducting fluid is considered. It is assumed that the plates are kept at different temperatures which decay with time. The partial differential equations governing the flow are solved by perturbation technique. Expressions for the velocity of fluid and particle phases, temperature field, Nusselt number, skin friction and flow flux are obtained within the channel. The effects of various parameters like stratification factor, magnetic field parameter, Prandtl number on temperature field, heat transfer, skin friction, flow flux, velocity for both the fluid and particle phases are displayed through graphs and discussed numerically. 相似文献
57.
From four Arnica species (A. angustifolia Vahl ssp. attenuata (Greene) Maguire, A. lonchophylla Greene ssp. lonchophylla Maguire (flowerheads), A. chamissonis Less. ssp. foliosa (Nutt.) Maguire, A. montana L. (roots and rhizomes)) a total of twelve lignans of the furofuran-, dibenzylbutyrolactone- and dibenzylbutyrolactol-type were isolated. No report on lignans as constituents of Arnica species exists so far. Besides the known pinoresinol, epipinoresinol, phillygenin, matairesinol, nortrachelogenin and nortracheloside, six dibenzylbutyrolactol derivatives with different stereochemistry and substitution at C-9 were isolated and their structures elucidated by NMR spectroscopic and mass spectral analysis. 相似文献
58.
Goriachko A He Y Knapp M Over H Corso M Brugger T Berner S Osterwalder J Greber T 《Langmuir : the ACS journal of surfaces and colloids》2007,23(6):2928-2931
Hexagonal boron nitride (h-BN) nanostructures were grown on Ru(0001), and are very similar to those previously reported on Rh(111). They show a highly regular 12 x 12 superstructure, comprising 2 nm wide apertures with a depth of about 0.1 nm. Valence band photoemission reveals two distinctly bonded h-BN species, and X-ray photoelectron spectroscopy indicates an h-BN monolayer film. The functionality of the h-BN/Ru(0001) nanomesh is demonstrated by using this structure for the assembly of gold nanoclusters. 相似文献
59.
Lloyd. M. Robeson Robert. A. Berner 《Journal of Polymer Science.Polymer Physics》2001,39(11):1093-1106
Polymer blend technology has been one of the most investigated areas in polymer science in the past 3 decades. The one area of polymer blends that has been virtually ignored involves simple emulsion blends, although several articles have recently appeared that address film formation and mechanical characteristics. In this study, we investigated the mechanical property behavior of emulsion blends composed of low/high‐glass‐transition‐temperature polymers (where low and high mean below and above the test temperature, respectively). The emulsions chosen for this study had similar particle sizes, and the mixtures were rheologically stable. Two conditions were chosen, a binary combination of polymers that were thermodynamically immiscible and another system that was thermodynamically miscible. The mechanical property results over the entire composition range were compared with the predictions of the equivalent box model (EBM) with the universal parameters predicted by percolation theory. An array of randomly mixed and equal‐size particles of differing moduli was expected to show excellent agreement with theory, and the emulsion blends provided an excellent experimental basis for testing the theory. For the immiscible blend, the EBM prediction for the modulus showed excellent agreement with experimental results. With tensile strength, the agreement between the modulus and theory was good if the yield strength for the higher glass‐transition‐temperature polymer was employed in comparison with the actual tensile strength. The phase inversion point (where both phases were equally continuous) was at a 0.50 volume fraction of each component (based on an analysis employing Kerner's equation), just as expected for a random mixture of equal‐size particles. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1093–1106, 2001 相似文献