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21.
22.
Kruk M Dufour B Celer EB Kowalewski T Jaroniec M Matyjaszewski K 《The journal of physical chemistry. B》2005,109(19):9216-9225
Mesoporous carbons were synthesized from polyacrylonitrile (PAN) using ordered and disordered mesoporous silica templates and were characterized using transmission electron microscopy (TEM), powder X-ray diffraction, nitrogen adsorption, and thermogravimetry. The pores of the silica templates were infiltrated with carbon precursor (PAN) via polymerization of acrylonitrile from initiation sites chemically bonded to the silica surface. This polymerization method is expected to allow for a uniform filling of the template with PAN and to minimize the introduction of nontemplated PAN, thus mitigating the formation of nontemplated carbon. PAN was stabilized by heating to 573 K under air and carbonized under N2 at 1073 K. The resulting carbons exhibited high total pore volumes (1.5-1.8 cm3 g(-1)), with a primary contribution of the mesopore volume and with relatively low microporosity. The carbons synthesized using mesoporous templates with a 2-dimensional hexagonal structure (SBA-15 silica) and a face-centered cubic structure (FDU-1 silica) exhibited narrow pore size distributions (PSDs), whereas the carbon synthesized using disordered silica gel template had broader PSD. TEM showed that the SBA-15-templated carbon was composed of arrays of long, straight, or curved nanorods aligned in 2-D hexagonal arrays. The carbon replica of FDU-1 silica appeared to be composed of ordered arrays of spheres. XRD provided evidence of some degree of ordering of graphene sheets in the carbon frameworks. Elemental analysis showed that the carbons contain an appreciable amount of nitrogen. The use of our novel infiltration method and PAN as a carbon precursor allowed us to obtain ordered mesoporous carbons (OMCs) with (i) very high mesopore volume, (ii) low microporosity, (iii) low secondary mesoporosity, (iv) large pore diameter (8-12 nm), and (v) semi-graphitic framework, which represent a desirable combination of features that has not been realized before for OMCs. 相似文献
23.
This article focuses on the formulation of a hysteretic model used as anisolator restoring force model. The proposed model is based on operatorgoverning input and output functions that depend on the deflection andthe restoring force of the isolator. First, the mathematical formulationis demonstrated, then the hysteretic model proposed is applied toisolators having different types of behavior. The model parameters aresought using the experimental force-deflection loop of each of theisolators studied. Next, the transient response of a flexible structuremounted on an all-metal isolator is predicted by coupling the firstorder differential equation of the restoring force and the second orderdifferential equations of the structure's motion. The experimentalinvestigation validates the proposed hysteretic model applied to theall-metal mount. 相似文献
24.
In this Note, we first present a model for droplet secondary breakup, in liquid sprays. This model is based on the kinetic theory formalism and uses experimental correlations found in the literature (L.-P. Hsiang, G.M. Faeth, Int. J. Multiphase Flow 19 (5) (1993) 721–735; R. Maxey, J. Riley, Phys. Fluids 26 (4) (1983) 883–889; M. Pilch, C.A. Erdman, Int. J. Multiphase Flow 13 (6) (1987) 741–757) to determine the fragmentation rate and its outcome. We then conduct a mathematical study of the resulting kinetic equation. We prove, under some physically reasonable assumptions, an existence and uniqueness theorem and characterize the long-time behaviour of the solution. To cite this article: G. Dufour et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
25.
26.
Goumri-Said S. Salomon L. Dufour J. P. De Fornel F. 《Optical and Quantum Electronics》2004,36(9):787-806
Numerical simulation of a two-dimensional probe–object system for photon scanning tunneling microscope is presented. The R-matrix propagation algorithm incorporated into the Fourier modal method was used to achieve an extended capability for modeling of a realistic system consisting of both a probe and a sample. The type of the mode guided through the dielectric probe and the coupling of the near-field to fundamental guiding mode in the probe are discussed. The influence of the probe parameters on the near-field images is investigated. Three different probe shapes were simulated in the constant height scanning mode. The transmitted flux intensity through the probe was found to be strongly dependent on the tip shape. The analysis shows a good agreement of the obtained results with the available theoretical works and confirming experimental results. The proposed numerical scheme can find applications for near-field probe characterization and provides an understanding of the degree of perturbation introduced by a probe tip in the experiment. 相似文献
27.
Grandeury A. Renou L. Dufour F. Petit S. Gouhier G. Coquerel G. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):377-390
The crystallization behaviour and the physical characterization of supramolecular complexes formed between permethylated-α-cyclodextrin
(TMα-CD) and the enantiomers of phenylethanol (PE) are investigated. According to crystal structure analyses, complexes containing
the pure guest enantiomers are almost isomorphous, indicating that the host presents a poor ability to distinguish PE enantiomers
at a molecular level. Nevertheless, crystallizations from racemic PE in water induce an efficient chiral discrimination and
allow the enantio-separation of the guests despite the existence of a solid solution revealed by XRPD and coupled TG-DSC analyses.
The enantiodifferentiation is explained by solubility differences between the two diastereomeric complexes in the studied
temperature range. Moreover, it is shown that the diastereomeric complex TMα-CD/(S)-PE crystallizes in two distinct phases: a monohydrate and an anhydrous form, with a transition temperature close to 37°C.
The insertion of a water molecule in the crystals grown below 37°C does not involve any other change of the crystal packing
nor of the molecular conformation, but leads to different crystal growth mechanisms inducing different morphologies and distinct
thermal behaviours.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
F. S. Krasniqi O. Renner E. Dalimier E. Dufour R. Schott E. Förster 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):439-444
A systematic study of the Langmuir-wave-caused dips (L
dips) observed in profiles of the Al Ly γ line emitted from
laser irradiated sandwich targets indicates that these fine
spectral features can be used as a tool for density diagnostics in
intermediately coupled plasmas. The spectroscopic data required
for a reliable identification of L dips were collected by a
vertical-geometry Johann spectrometer providing high spectral and
spatial resolution. The electron densities deduced from the
evolution of the L dips along the laser target axis compare well
with those derived from hydrosimulations and from measurements of
the line widths and shifts. 相似文献
29.
30.
C. Cabot H. Gauvin Y. Le Beyec H. Delagrange J.P. Dufour Y. Llabador A. Fleury John M. Alexander 《Nuclear Physics A》1984,427(1):173-185
Fusion cross sections for the reaction 40Ar + 110Pd have been measured in the bombarding energy range 164–262 MeV. Evaporation residues and fission fragments have been detected by ΔE-E telescopes. We compare the fusion cross sections to various theoretical models with special attention to the high-energy data. An analysis is also given for entrance-channel spin zones for evaporation residues and fission. 相似文献