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31.
avec la collaboration technique de N. Arnal F. Romain et G. Sagon J. de Villepin A. Novak 《Journal of Molecular Structure》1976,30(2):255-269
Infrared and Raman spectra of polycrystalline LiHC2O4, LiHC2O4, · H2O and their D and 6Li containing isotopic derivatives have been investigated at 300 and 90 K in the 4000–50 cm−1 region. All the internal and external optically active modes of lithium hydrogen oxalate monohydrate have been identified and an assignment is given. The spectroscopic data are consistent with X-ray data showing an asymmetric short hydrogen bond with a positive deuterium isotope effect. The dehydration of LiHC2O4, · H2O changes the type of hydrogen bond which becomes symmetric of the double minimum type. The deuteration of LiHC2O4, on the other hand. weakens the hydrogen bond and makes it asymmetric again. The asymmetry appears more pronounced at low temperature. 相似文献
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Competition between supernucleation and plasticization in the crystallization and rheological behavior of PCL/CNT‐based nanocomposites and nanohybrids
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Juan F. Vega Joel Fernández‐Alcázar Juan V. López Rose Mary Michell Ricardo A. Pérez‐Camargo Benoit Ruelle Javier Martínez‐Salazar María Luisa Arnal Philippe Dubois Alejandro J. Müller 《Journal of Polymer Science.Polymer Physics》2017,55(17):1310-1325
PCL was blended with pristine multiwalled carbon nanotubes (MWCNT) and with a nanohybrid obtained from the same MWCNT but grafted with low molecular weight PCL, employing concentrations of 0.25 to 5 wt % of MWCNT and MWCNT‐g‐PCL. Excellent CNT dispersion was found in all samples leading to supernucleation of both nanofiller types. Nanohybrids with 1 wt % or less MWCNTs crystallize faster than nanocomposites (due to supernucleation), while the trend eventually reverses at higher nanotubes content (because of plasticization). Rheological results show that yield‐like behavior develops in both nanocomposites, even for the minimum content of carbon nanotubes. In addition, the MWCNT‐g‐PCL family, when compared with the neat polymer, exhibits lower values of viscosity and modulus in oscillatory shear, and higher compliance in creep. These rheological differences are discussed in terms of the plasticization effect caused by the existence of low molecular weight free and grafted PCL chains in the nanohybrids. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1310–1325 相似文献
34.
Looking to the separation of irreducible unitary representations of an exponential Lie group G through the image of their moment map, we propose here a new way: instead to extend the moment map to the universal enveloping algebra of G, we define a non linear mapping Φ from the dual of the Lie algebra g of G to the dual g+∗ of a larger solvable group G+, and we extend the representation from G to G+, in such a manner that the corresponding coadjoint orbits in g+∗ have distinct closed convex hull. This allows us to separate the irreducible unitary representations of G. 相似文献
35.
Using the porosity of a binary exotemplate, with mesoporous core-shell structure (SiO2@ZrO2), opens a new pathway to produce hybrid core-shell spheres, composite hollow spheres, and porous hollow spheres -- all monodisperse in size. 相似文献
36.
Two new alkylamine-substituted nickel(II)-salphen complexes have been prepared and their interactions with DNA investigated. FRET studies have shown that these complexes have a remarkable ability to stabilize G-quadruplex DNA. Furthermore, TRAP/Taq assays have shown that these complexes inhibit telomerase at low micromolar concentrations. 相似文献
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38.
We give a new proof of a weak Paley-Wiener theorem for nilpotent Lie groups due to Lipsman and Rosenberg and we introduce a general notion of Q.U.P for any unimodular locally compact group.
39.
Didier Arnal 《Letters in Mathematical Physics》2004,69(1):205-222
A formality on a manifold M is a quasi isomorphism between the space of polyvector fields (T poly(M)) and the space of multidifferential operators (D poly(M)). In the case M=R d , such a mapping was explicitly built by Kontsevich, using graphs drawn in configuration spaces. Looking for such a construction step by step, we have to consider several cohomologies (Hochschild, Chevalley, and Harrison and Chevalley) for mappings defined on T poly. Restricting ourselves to the case of mappings defined with graphs, we determine the corresponding coboundary operators directly on the spaces of graphs. The last cohomology vanishes. 相似文献
40.
Arnaldo T. Lorenzo María L. Arnal Johan J. Snchez Alejandro J. Müller 《Journal of Polymer Science.Polymer Physics》2006,44(12):1738-1750
It is widely known that when a polymer is heated just above its melting point and is kept at a given temperature (denoted Ts) for a short time, when it is cooled down its nucleation density increases and its peak crystallization temperature shifts to higher temperatures, as detected for instance by differential scanning calorimetry (DSC). The Ts temperature range where the described process occurs has been named Domain II self‐nucleation (SN) because the selected Ts temperatures are high enough to melt the polymer without causing detectable annealing of any remnant crystals by DSC. Experimental results obtained by DSC, polarized light optical microscopy (PLOM), and rheology indicate that these techniques are unable to detect any remaining crystal fragments in Domain II. Our kinetic results demonstrate that Domain II SN is a transient phenomenon that can even disappear if enough time at Ts is allowed. Results of the study of the time dependence of the SN effect indicates two possibilities: (a) if crystal fragments are present (even if undetected by the employed techniques) their final melting is a very slow process (in the order of hours); (b) if all crystallites have melted in Domain II, then it may be more plausible to reinterpret self‐nuclei as arising from “precursors” whose detail nature has not been the subject of this investigation but that can be regarded as either a residual segmental orientation in the melt (i.e., a melt memory effect) or a mesophase in a preordered state. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1738–1750, 2006 相似文献