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排序方式: 共有114条查询结果,搜索用时 0 毫秒
31.
Clara Fournier Jean-Daniel Marty Christian Bourgerette Alain Boudet Monique Mauzac 《Liquid crystals》2003,30(4):435-443
Ordered beads were obtained by the suspension copolymerization of amesogenic methacrylate-based monomer and methacrylic acid. The stability of these particles and the liquid crystal organization inside the particles depend mainly on the time of polymerization and on the crosslinking. Suspended droplets of monomers or polymers can be obtained as well as solid spheres. The solid particles exhibit ordered microstructures with a liquid crystal configuration that has a variable form depending on polymerization time and observation temperature. Bead characteristics such as morphology, size and polydispersity, and porosity are discussed and compared with those of non-mesomorphic beads. The mesomorphic beads are smaller and their porosity lower. The presence of a crosslinker during the polymerization process leads to more mechanically stable particles with retention of polymorphism. 相似文献
32.
Jean-Daniel Boissonnat Olivier Devillers René Schott Monique Teillaud Mariette Yvinec 《Discrete and Computational Geometry》1992,8(1):51-71
This paper presents a general framework for the design and randomized analysis of geometric algorithms. These algorithms are
on-line and the framework provides general bounds for their expected space and time complexities when averaging over all permutations
of the input data. The method is general and can be applied to various geometric problems. The power of the technique is illustrated
by new efficient on-line algorithms for constructing convex hulls and Voronoi diagrams in any dimension, Voronoi diagrams
of line segments in the plane, arrangements of curves in the plane, and others.
This work has been supported in part by the ESPRIT Basic Research Action Nr. 3075 (ALCOM). 相似文献
33.
Smooth surface reconstruction via natural neighbour interpolation of distance functions 总被引:5,自引:0,他引:5
We present an algorithm to reconstruct smooth surfaces of arbitrary topology from unorganised sample points and normals. The method uses natural neighbour interpolation, works in any dimension and accommodates non-uniform samples. The reconstructed surface interpolates the data points and is implicitly represented as the zero set of some pseudo-distance function. It can be meshed so as to satisfy a user-defined error bound, which makes the method especially relevant for small point sets. Experimental results are presented for surfaces in
. 相似文献
34.
PdI2 in DMSO promoted the oxidation of functionalized diarylalkynes into benzil derivatives in excellent yields. This new oxidation reaction was achieved with short reaction times and low loading of palladium catalyst. This efficient catalytic process has been applied successfully to the one-pot construction of a series of nitrogen-containing heterocycles of biological interest according to a tandem oxidation-nitrogen nucleophiles condensation-cyclization. 相似文献
35.
Dr. Guillaume Naulet Aline Delamare Dr. Gilles Guichard Dr. Guillaume Compain 《European journal of organic chemistry》2023,26(10):e202300164
We report the direct incorporation of the hexafluoroisobutyl group on a chiral glycine Schiff base complex mediated by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The fluoroalkylation involves 2-(bromomethyl)-1,1,1,3,3,3-hexafluoropropane reagent, which generates in situ hexafluoroisobutylene (HFIB), and reacts then with the enolate through a tandem allylic shift/hydrofluorination process. We showed that the use of neutral organic base DBU generates in situ an original DBU⋅HF salt, which preserves the fluoride nucleophilicity and acts as a fluorinating agent. This fluoride salt promotes the hydrofluorination of the pentafluorinated alkene overcoming the usual fluoride β-elimination observed with α-CF3-vinyl reagents. With alkali metal bases, by contrast, the hydrofluorination is disfavored and the pentafluorinated alkene intermediate is obtained predominantly. This study highlights the critical role of the fluoride counter ion to preserve its nucleophilicity. The protocol is amenable to multidecagram scale synthesis of enantiopure (S)- and (R)-5,5,5,5’,5’,5’-hexafluoroleucine and their N-Fmoc or N-Boc derivatives in good overall yield. 相似文献
36.
Hyperbranched polyamidoamine as stabilizer for catalytically active nanoparticles in water 总被引:1,自引:0,他引:1
Marty JD Martinez-Aripe E Mingotaud AF Mingotaud C 《Journal of colloid and interface science》2008,326(1):51-54
Poly(amidoamine) hyperbranched polymers (HYPAM) were successfully used to synthesize platinum nanoparticles of ca. 1.8 nm and to stabilize these particles in water. Furthermore these hyperbranched-stabilized platinum nanoparticles proved to be effective and robust for hydrogenation reaction in water. 相似文献
37.
38.
Antonio Segalini Ramis Örlü Philipp Schlatter P. Henrik Alfredsson Jean-Daniel Rüedi Alessandro Talamelli 《Experiments in fluids》2011,51(3):693-700
A new approach to evaluate turbulence intensity and transverse Taylor microscale in turbulent flows is presented. The method
is based on a correction scheme that compensates for probe resolution effects and is applied by combining the response of
two single hot-wire sensors with different wire lengths. Even though the technique, when compared to other correction schemes,
requires two independent measurements, it provides, for the same data, an estimate of the spanwise Taylor microscale. The
method is here applied to streamwise turbulence intensity distributions of turbulent boundary layer flows but it is applicable
generally in any turbulent flow. The technique has been firstly validated against spatially averaged DNS data of a zero pressure-gradient
turbulent boundary layer showing a good capacity to reconstruct the actual profiles and to predict a qualitatively correct
and quantitatively agreeing transverse Taylor microscale over the entire height of the boundary layer. Finally, the proposed
method has been applied to available higher Reynolds number data from recent boundary layer experiments where an estimation
of the turbulence intensity and of the Taylor microscale has been performed. 相似文献
39.
Extracts of effluents from two different wastewater treatment plants (WWTP) in Switzerland taken during the application period of pesticides were examined by coupling an HPLC-MS system to a nuclear magnetic resonance spectrometer using a post column peak trapping device. By trapping 1 min portions of the chromatogram onto post column solid phase extraction cartridges (time slice-SPE-NMR) a comprehensive overview of proton carrying constituents could be achieved. Non-supervised statistical analysis of the NMR spectra obtained by this approach revealed NMR resonances pointing to contaminants present in decreasing proton concentration in the extracts. Comparison of exact mass data acquired during the trapping process to these NMR resonances enabled the identification of the pesticides Linuron, Metazachlor, Ethofumesate, Isoproturon, Metamitron, Propazine and Chloridazon. Desaminometamitron, a known transformation product of Metamitron could also be identified together with unexpected highly concentrated C8, C10 and C12 fatty acids and their glycerol mono- and di esters. Other compounds identified were a drug metabolite (3-Carboxymefenamic acid), a sun screen agent (Ensulizole: 2-Phenyl-1H-1,3-benzodiazole-6-sulfonic acid) and industrial chemicals (Benzotriazole, N-Benzyl-indole). In addition, a number of well-resolved proton spectra cannot be attributed to a mass response showing the need of further investigations using 2D-NMR and different ionization techniques. 相似文献
40.