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81.
Imene Mejri Mohamed Kadri Younes Abdelhamid Ghorbel 《Journal of Sol-Gel Science and Technology》2006,40(1):3-8
Aerogel and xerogel sulphated zirconia with defined atomic ratio S/Zr = 0.5 and molar hydrolysis ratio h = nH2O/nZrO2 = 3 show different textural and structural properties after calcination at high temperatures. The aerogel obtained just after
solvent evacuation develops only the tetragonal phase, whereas the xerogel dried in an oven is amorphous. Heating to a temperature
above 833 K, leads to transition of the tetragonal phase to the monoclinic one for the two solids, due to sulphur loss but
the tetragonal phase remains stable for the aerogel . Raman, Infrared and XPS spectroscopies show that the loss of the sulphur
at high temperatures seems to be easier for the xerogel than for the aerogel. 相似文献
82.
4‐Bromo‐1‐phenyl‐3,5‐pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4‐substituted derivatives 3–8 . The cyclized compounds 9–11 were achieved on refluxing compounds 3 , 4 or 6a in glacial acetic acid or diphenyl ether. 4,4‐Dibromo‐1‐phenyl‐3,5‐pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5‐pyrazolidinediones 13–15 , respectively. The 4‐aralkylidine derivatives 16a‐c , were subjected to Mannich reaction to give Mannich bases 17a‐c‐22a‐c , respectively. 4‐(p‐Methylphenylaminomethylidine)‐1‐phenyl‐3,5‐pyrazolidinedione 23 or 4‐(p‐methylphenylazo)‐1‐phenyl‐3,5‐pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S‐acetals to give pyrano[2,3‐c]pyrazole, pyrazolo[4′,3′:5,6]pyrano[2,3‐c]pyrazole, spiropyrazole‐4,3′‐pyrazole and spiropyrazole‐4,3′‐[1,2,4]triazolane derivatives 24–34 , respectively. 相似文献
83.
Gaël Poirier Younes Messaddeq Marcel Poulain 《Journal of solid state chemistry》2005,178(5):1533-1538
Transparent glasses were synthesized in the NaPO3-BaF2-WO3 ternary system and several structural characterizations were performed by X-ray absorption spectroscopy (XANES) at the tungsten LI and LIII absorption edges and by Raman spectroscopy. Special attention was paid to the coordination state of tungsten atoms in the vitreous network.XANES investigations showed that tungsten atoms are only six-fold coordinated (octahedra WO6) and that these glasses are free of tungstate tetrahedra (WO4).In addition, Raman spectroscopy allowed to identify a break in the linear phosphate chains as the amount of WO3 increases and the formation of P-O-W bonds in the vitreous network indicating the modifier behavior of WO6 octahedra in the glass network. Based on XANES data, we suggested a new attribution of several Raman absorption bands which allowed to identify the presence of W-O− and WO terminal bonds and a progressive apparition of W-O-W bridging bonds for the most WO3 concentrated samples (?30% molar) due to the formation of WO6 clusters. 相似文献
84.
Knoevenagel reactions involving carbonyl compounds and active methylene derivatives have been studied in the presence of alumina, KSF and K10 montmorillonites. With addition of water the ester group undergoes hydrolysis. A route is disclosed for the synthesis of coumarine compounds catalyzed by solid supports. 相似文献
85.
Seyed Mohammad Seyed Khademi Mahmoud Tabrizchi Ursula Telgheder Younes Valadbeigi Vahideh Ilbeigi 《International Journal for Ion Mobility Spectrometry》2017,20(1-2):15-21
Methyl tertiary-butyl ether (MTBE) is an organic compound which is used as a gasoline additive. Contamination of ground and surface water can occur due to large scale use of MTBE and its high solubility in water. According to United State Environmental Protection Agency (USEPA), MTBE is a possible human carcinogen at high doses and its detection and measurement in the water is important as concerned about human health. In this work, ion mobility spectrometry (IMS) equipped with a corona discharge ionization source was used for determination of MTBE in drinking water. Both pure and aqueous solutions of MTBE were studied and their ion mobility spectra were obtained at different temperatures. Using a calibration curve for detection of MTBE in drinking water, a detection limit (LOD) of 1 mg/L was obtained by IMS. This work proved that, IMS with corona discharge can be used for fast and direct detection of MTBE in water sample without any sample preparation. 相似文献
86.
The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe3?xTixO4) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe3?xTixO4@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity. 相似文献
87.
88.
Fernando Antonio Simas Vaz Arthur Damásio Moutinho Jose Paulo Rodrigues Furtado de Mendonça Ricardo Tavares de Araújo Sidney José Lima Ribeiro Ferminio César Polachini Younes Messaddeq Marcone Augusto Leal de Oliveira 《Microchemical Journal》2012
The preparation of photo-polymerized sol–gel monolithic stationary phases (MSP) within 100 μm internal diameter polyacrylate-coated fused-silica capillaries for use in capillary electrochromatography (CEC) was optimized. Eight mixtures containing different amounts of methacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid solution as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photo-initiator were irradiated at 370 nm inside the capillaries in order to complete the MSP polymerization, according to a fractional factorial experimental design 2IV4-1. All the preparation procedure, from capillary pretreatment until the MSP is ready to use in CEC, were made in less than four hours in mild conditions. A high pressurization injection device (HPID) useful for micro-volume syringes was built in order to achieve practical, controlled and precise injections of sols, solvents and electrolytes in the capillaries. The eight MSP were equally washed, conditioned and submitted to CEC procedures via short-end injection, which showed higher efficiency and peak height taking shorter analysis time. Electrochromatographic behaviors of the MSP were corroborated with morphological characterizations by scanning electron microscopy. The optimum condition, which allowed the separation of standard mixture containing thiourea (marker compound), naphthalene, acenaphthene, fluorene, phenanthrene and anthracene in twelve minutes without external pressure assistance, showed efficiencies up to 51,460 N/m, relative standard deviation from 0.05 to 3.3% for migration/retention time and from 0.14 to 1.6% for relative area (considering thiourea as an internal standard) and also showed no statistical evidence that three MSP prepared at the same condition are different within 95% confidence interval. 相似文献
89.
Younes Saadat Soleyman Hosseinzadeh Hormoz Eslami Faramarz Afshar-Taromi 《Colloid and polymer science》2012,290(13):1333-1339
In this work, we present a novel synthesis method for the preparation of micron-sized, monodisperse polymeric nonspherical particles without changing the shape of a precursor. In this technique, which we called micromolding–polymerization, nonspherical particles of second polymer were formed directly on the surface of micromolds (solvent-swollen polymeric particles). The experimental results showed that the affinity between the second polymer and micromolds, and size and concentration of the oligoradicals specify the shape of the particles. 相似文献
90.
Grgoire Willot Franois Gomez Pierre Vast Vronique Andries Marco Martines Younes Messaddeq Marcel Poulain 《Comptes Rendus Chimie》2002,5(12):899
A soft chemistry route is described to obtain glasses in the P2O5–Na2O–ZnO–H2O. It is based on the addition of zinc salts to coacervates prepared from sodium polyphosphate. The processing of these coacervates leads to polyphosphate glasses with the same properties as those of glasses prepared in the classical way. So far, little work has been implemented in this system using ‘coacervate route’. However, it makes an attractive method for coating and joining processes on the industrial scale. As the anion associated to zinc may take part in the adhesion mechanism, coacervate formation has been studied using zinc chloride, nitrate and sulphate as starting materials. The physical properties of the glasses obtained by this method are reported and potential applications of zinc and silver coacervate are described. 相似文献