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101.
Investigation of the role of cadmium sulfide in the surface passivation of lead sulfide quantum dots
Mark Ferne Andrew Watt Jamie Warner Jamie Riches Norman Heckenberg Halina Rubinsztein-Dunlop 《Journal of Crystal Growth》2004,270(3-4):380-383
Surface passivation of PbS nanocrystals (NC), resulting in strong photoluminescence, can be achieved by the introduction of CdS precursors. The role of CdS in the surface passivation of PbS NCs is uncertain, as the crystalline structure of CdS and PbS are different, which should impede effective epitaxial overgrowth. Absorption spectroscopy is used to show that the CdS precursors strongly interact with the PbS NC surface. Electron microscopy reveals that the introduction of CdS precursors results in an increased particle size, consistent with overcoating. However, we also find the process to be highly non-uniform. Nevertheless, evidence for epitaxial growth is found, suggesting that effective surface passivation may be possible. 相似文献
102.
103.
Proper orthogonal decomposition (POD) is a method of examining spatial coherence in unsteady flow fields from an ensemble
of multidimensional measurements. When applied to experimental data, the proper orthogonal decomposition is generally restricted
to data sets with low spatial resolution. This is because of the inherent difficulties in generating an ensemble of measurements
that contain a large number of data points. In this paper, a system for obtaining a large ensemble of three-dimensional scalar
measurements using interferometric tomography is presented. The proper orthogonal decomposition is applied in three spatial
dimensions to experimental data of two jet-like flows. The coherent structure present in the near field of a neutrally buoyant,
helium–argon jet and the far field of a buoyant helium jet into air is visualized. The POD results of the helium–argon jet
clearly reveal the breakdown region of a sequence of vortex rings and a large-scale flapping motion in the jet far field.
The POD of the buoyant helium jet shows a number of competing modes with varying degrees of helicity.
Received: 14 January 2000/Accepted: 26 September 2000 相似文献
104.
The paper describes an investigation of the preparation and properties of amylose phenylosazone and phenylhydrazone. Under the conditions used, amylose phenylosazone was not formed quantitatively and considerable degradation of the amylose occurred. The phenylhydrazone, however, can readily be prepared in quantitative yield and the polymer remains undergraded. Solutions of amylose phenylhydrazone in dimethylsulfoxide may be used to determine the number average molecular weight of amylose samples. 相似文献
105.
Conversion of the Wieland-Miescher ketone to a bicyclic dienophile capable of providing the AB rings of the picrasane skeleton of the guassinoids required the introduction of a C-8α methyl group in a 2-decalone. Among the routes explored, the conversion of the Wieland-Miescher ketone to a 4,4a,5,6,7,8-hexahydro-4aβ-methyl-8-methylene-2(3H)-napthalenone and subsequent reduction to a 3,4,4a,5,6,7,8,8aα-octahydro-4aβ,8α-dimethyl-2(1H)-napthalenone proved most useful. 相似文献
106.
We report a miniaturized resonant/non-resonant multi-fiber raster scanner that is paired with a gradient-index lens assembly to achieve a compact and flexible multifocal multiphoton endoscope capable of longitudinal parallel image acquisition. Multiphoton images are obtained simultaneously at three axial depths, separated by ≥4.8 μm, by incorporating three axially offset double clad optical fibers into the miniaturized scanner. The fabricated endoscope has an outer diameter of 3 mm, a rigid length of 4 cm, and acquires images at 4 frames/s per focal plane, with lateral and axial resolutions for two-photon imaging of 0.8 and 10 μm, respectively. 相似文献
107.
Ferm M Watt J O'Hanlon S De Santis F Varotsos C 《Analytical and bioanalytical chemistry》2006,384(6):1320-1330
A new passive particle collector (inert surrogate surface) that collects particles from all directions has been developed.
It was used to measure particle deposition at 35 test sites as part of a project that examined corrosion of materials in order
that variation in particulate material could be used in development of dose–response functions in a modern multi-pollutant
environment. The project, MULTI-ASSESS, was funded by the EU to examine the effects of air pollution on cultural heritage.
Passive samplers were mounted rain-protected, and both in wind-protected and wind-exposed positions, to match the exposure
of the samples for corrosion studies. The particle mass and its chemical content (nitrate, ammonium, sulfate, calcium, sodium,
chloride, magnesium and potassium) were analysed. The loss of light reflectance on the surrogate surface was also measured.
Very little ammonium and potassium was found, and one or more anions are missing in the ion balance. There were many strong
correlations between the analysed species. The mass of analysed water-soluble ions was fairly constant at 24% of the total
mass. The particle mass deposited to the samplers in the wind-protected position was about 25% of the particles deposited
to an openly exposed sampler. The Cl−/Na+ ratios indicate a reaction between HNO3 and NaCl. The deposited nitrate flux corresponds to the missing chloride. The Ca2+ deposition equals the deposition and the anion deficiency. The deposition most likely originates from SO2 that has reacted with basic calcium-containing particles either before or after they were deposited. The particle depositions
at the urban sites were much higher than in nearby rural sites. The deposited mass correlated surprisingly well with the PM10 concentration, except at sites very close to traffic. 相似文献
108.
A. D. Martin W. J. Stirling R. S. Thorne G. Watt 《The European Physical Journal C - Particles and Fields》2010,70(1-2):51-72
We study the sensitivity of our recent MSTW 2008 NLO and NNLO PDF analyses to the values of the charm- and bottom-quark masses, and we provide additional public PDF sets for a wide range of these heavy-quark masses. We quantify the impact of varying m c and m b on the cross sections for W, Z and Higgs production at the Tevatron and the LHC. We generate 3- and 4-flavour versions of the (5-flavour) MSTW 2008 PDFs by evolving the input PDFs and α S determined from fits in the 5-flavour scheme, including the eigenvector PDF sets necessary for calculation of PDF uncertainties. As an example of their use, we study the difference in the Z total cross sections at the Tevatron and LHC in the 4- and 5-flavour schemes. Significant differences are found, illustrating the need to resum large logarithms in $Q^{2}/m_{b}^{2}$ by using the 5-flavour scheme. The 4-flavour scheme is still necessary, however, if cuts are imposed on associated (massive) b-quarks, as is the case for the experimental measurement of $Zb\bar{b}$ production and similar processes. 相似文献
109.
Arylenediamines are mono-N-alkylated by dialkyl carbonates in the presence of NaY zeolite catalyst in a regioselective and nontoxic process. 相似文献
110.
Watt M Hardebeck LK Kirkpatrick CC Lewis M 《Journal of the American Chemical Society》2011,133(11):3854-3862
Parallel face-to-face arene-arene complexes between benzene and substituted benzenes have been investigated at the MP2(full)/6-311G** and M05-2X/6-311G** levels of theory. A reasonably good correlation was found between the binding energies and the ∑|σ(m)| values of the substituted aromatics. It is proposed that a substituent |σ(m)| value informs on both the aromatic substituent dispersion/polarizability and the effect the substituent has on the aromatic electrostatics. Supporting this hypothesis, a combination of electrostatic (∑σ(m)) and dispersion/polarizability (∑M(r)) substituent constant terms gives an excellent, and statistically significant, correlation with the benzene-substituted benzene binding energy. Symmetry adapted perturbation theory energy decomposition calculations show the dominant attractive force is dispersion; however, the sum of all nonelectrostatic forces is essentially a constant, while the electrostatic component varies significantly. This explains the importance of including an electrostatic term when predicting benzene-substituted benzene binding energies. 相似文献