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排序方式: 共有123条查询结果,搜索用时 78 毫秒
31.
Francesca Di Gaudio Sergio Indelicato Roberto Monastero Grazia Ida Altieri Francesca Fayer Ornella Palesano Manuela Fontana Angelo B. Cefalu Massimiliano Greco David Bongiorno Serena Indelicato Angela Aronica Davide Noto Maurizio R. Averna 《Analytical and bioanalytical chemistry》2016,408(9):2373-2373
32.
Stefano Provera Giuseppe Guercio Lucilla Turco Ornella Curcuruto Giuseppe Alvaro Tino Rossi Carla Marchioro 《Magnetic resonance in chemistry : MRC》2010,48(7):523-530
Liquid chromatography‐NMR (LC–NMR) spectroscopy was used to obtain detailed information regarding the structure of the major bulk drug impurities present in GW597599 (vestipitant). The one‐dimensional 1H LC–NMR experiments were performed in both continuous and stop‐flow modes on a sample of GW597599 (vestipitant) enriched with mother liquor impurities. The information derived from both LC–NMR and LC–MS data provided the structural information of all major impurities. The full characterisation of the impurities by high‐resolution NMR spectroscopy was ultimately performed on appropriately synthesised compounds. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
33.
D'Acquarica I Gasparrini F Giannoli B Badaloni E Galletti B Giorgi F Tinti MO Vigevani A 《Journal of chromatography. A》2004,1061(2):167-173
We describe a new tandem-columns chiral-achiral HPLC arrangement by using a chiral column (CHIROBIOTIC TAG) connected in series with an achiral column (Spherisorb S5 SCX), based on a strong cationic exchange mechanism; this approach is very useful for the analysis of chiral molecules, containing cationic groups in their structures. We used this special combination to develop an easy and convenient procedure for the enantio- and chemo-selective dosage of propionyl L-carnitine (1) and relative impurities (2-6), which allowed for the simultaneous separation and quantitation within 30 min. Under the best chromatographic conditions (acetonitrile-10 mM sodium dihydrogen phosphate 65:35, v/v (pHa 6.80) as the mobile phase and UV detection at 205 nm], all the individual peaks were well separated. The applicability of the method, fully validated, was demonstrated by the analysis of a pharmaceutical batch of propionyl L-carnitine, where we found the following contents: 98.5% for 1 (drug substance); 0.15% for 3; 0.1% for 5 and 0.2% for 6. The enantiomeric excess (e.e.%) measured for the drug substance was 98.9%. Finally, a single mixed-bed column, packed with a binary mixture of the chiral and achiral phases, in a 1:1 ratio, gave similar chromatographic results as the tandem-columns approach, and thus, offered an easy alternative solution to the separation of the considered mixture. 相似文献
34.
D'Errico G Ciccarelli D Ortona O Paduano L Sartorio R 《Journal of colloid and interface science》2004,270(2):490-495
The interaction between pentaethylene glycol n-octyl ether (C8E5) and low-molecular-weight poly(acrylic acid) (PAA, M(w)=2000) in aqueous solution has been investigated by various experimental techniques at constant polymer concentration (0.1% w/w) with varying surfactant molality. Spectrofluorimetry, using pyrene as molecular probe, shows (i) the formation of surfactant-polymer aggregates at a surfactant molality (T(1)) lower than the critical micelle concentration (cmc) of C8E5 in water and (ii) the formation of free micelles at a surfactant molality (T(2)) slightly higher than the cmc. Fluorescence quenching measurements indicate that the presence of PAA induces a lowering of the C8E5 aggregation number. Calorimetry confirms spectrofluorimetric evidence; in addition, it shows the presence of weak interactions below T(1) between monomeric surfactant molecules and the polymer chains. Tensiometry shows that, above T(1), only a low fraction of surfactant molecules interact with the polymer and that free micelle formation occurs before polymer saturation. The peculiarities of the interaction between surfactants and low-molecular-weight polymers have been discussed. 相似文献
35.
Adriana De Stefanis Giorgio Perez Anthony A.G. Tomlinson Ornella Ursini Edo Lilla 《Reaction Kinetics and Catalysis Letters》2003,78(2):267-273
Protonation of (1R)-(+)-a-pinene using gaseous H3
+ ions led to a racemic mixture of camphene and limonene, to partial and no racemization, in acidic solutions and in solid
acids, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
36.
O. Curcuruto P. Traldi C. Cativiela M. D. Diaz De Villegas J. I. Garcia J. A. Mayoral D. Aj 《Journal of heterocyclic chemistry》1990,27(5):1495-1499
The mass spectrometric behaviour of four isomeric oxazolones is rationalized by means of metastable ion studies and bond order calculations via semiempirical methods. The data allow the identification of a possible intermediate structure of molecular species that accounts easily for the observed primary decomposition pathways. 相似文献
37.
Di Tullio A D'Acquarica I Gasparrini F Desiderio P Giannessi F Muck S Piccirilli F Tinti MO Villani C 《Chemical communications (Cambridge, England)》2002,(5):474-475
The enantiomers of carnitine are converted on-line in the injection port of a gas chromatograph into beta-hydroxy-gamma-butyrolactones and are separated on a derivatized beta-cyclodextrin chiral stationary phase. 相似文献
38.
D'Errico G Ortona O Paduano L Vitagliano V 《Journal of colloid and interface science》2001,239(1):264-271
Intradiffusion coefficients, D, of n-alkyltrimethylammonium bromides [CH(3)-(CH(2))(n-1)-N(CH(3))(3)Br, C(n)TAB] (n=6, 8, 10, 12) in mixtures with heavy water were measured by the PGSE-NMR technique at 25 degrees C. The experimental data permitted evaluation of the influence of the alkyl chain length on the surfactant self-aggregation process. For all the surfactants considered, the D trend showed a slope change corresponding to the critical micellar composition (cmc). In the premicellar composition range, D decreased linearly with the square root of the surfactant molality. The D values extrapolated at infinite dilution were related to the limiting mutual diffusion coefficients, determined through the Taylor dispersion technique. In the micellar composition range, solubilized tetramethylsilane (TMS) molecules were used to determine the micelle intradiffusion coefficient, D(M), from which the aggregate radii and the aggregation numbers were obtained. The decreasing trend of D(M) with increasing surfactant molality was interpreted in terms of interparticle electrostatic repulsion. D(M) values allowed evaluation of the Gouy-Chapman layer thickness. The solvent intradiffusion coefficient in the heavy water-C(n)TAB mixtures, D(w), was also measured. It decreased with increasing surfactant molality. For n=8, 10, 12 the D(w) trend presented a slope change at the cmc, which could be ascribed to the strong decrease in hydration of surfactant molecules upon micellization. Because of its short hydrophobic tail, C(6)TAB exhibited peculiar aggregation behavior. Its cmc, which is poorly marked, is lower than the value predicted by extrapolating the cmc values obtained for the other terms of the series. The C(6)TAB aggregates do not solubilize TMS molecules; the estimated aggregation number is extremely low ( approximately 3). Finally, no abrupt slope change in the solvent intradiffusion coefficient trend was detected. This evidence suggests that C(6)TAB molecules do not micellize in aqueous solution, but form trimers in which the surfactant hydrophobic tails are not hidden from contact with water molecules. Copyright 2001 Academic Press. 相似文献
39.
Franco Cataldo Ornella Ursini Pietro Ragni 《Plasma Chemistry and Plasma Processing》2013,33(1):355-365
The trichloromethylation of C60 fullerene was achieved either under plasmalysis conditions, i.e. by arcing a solution of C60 in CCl4 between two graphite electrodes, or by sonolysis of C60 in CCl4. The resulting products were studied by UV–VIS and FT-IR spectroscopy as well as by thermogravimetric analysis in comparison to the trichloromethyl adducts formed by radiolysis or photolysis of C60 in CCl4. A reference study on the plasmalysis of pure CCl4 has revealed the formation of carbon soot and hexachlorobenzene. The formation of the latter compound was suppressed when C60 was present in CCl4. 相似文献
40.