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排序方式: 共有93条查询结果,搜索用时 140 毫秒
11.
Marina Sicignano Dr. Rosaria Schettini Luisa Sica Giovanni Pierri Prof. Dr. Francesco De Riccardis Prof. Dr. Irene Izzo Dr. Bholanath Maity Dr. Yury Minenkov Prof. Dr. Luigi Cavallo Dr. Giorgio Della Sala 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(29):7131-7141
The first highly enantioselective arylogous Michael reaction (AMR) of 3-unsubstituted phthalides has been described. This phase-transfer methodology, which uses catalytic amounts of KOH/18-crown-6 catalyst in mesitylene in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), gives access to a broad range of 3-monosubstituted phthalides with high levels of syn diastereoselectivity and good yields, starting from 3-unsubstituted derivatives and diverse α,β-unsaturated carbonyl compounds. The reaction also applies to unactivated 3-alkyl phthalides to afford 3,3-dialkyl derivatives. A plausible mechanism has been suggested. DFT analysis of possible transition states gives a rationale of the high syn diastereoselectivity observed and its correlation with the solvent's dielectric constant. 相似文献
12.
13.
Prof. Francesca Caterina Izzo Matilde Kratter Dr. Austin Nevin Prof. Elisabetta Zendri 《ChemistryOpen》2021,10(9):904-921
Up to 70 % of the oil paintings conserved in collections present metal soaps, which result from the chemical reaction between metal ions present in the painted layers and free fatty acids from the lipidic binders. In recent decades, conservators and conservation scientists have been systematically identifying various and frequent conservation problems that can be linked to the formation of metal soaps. It is also increasingly recognized that metal soap formation may not compromise the integrity of paint so there is a need for careful assessment of the implications of metal soaps for conservation. This review aims to critically assess scientific literature related to commonly adopted analytical techniques for the analysis of metal soaps in oil paintings. A comparison of different analytical methods is provided, highlighting advantages associated with each, as well as limitations identified through the analysis of reference materials and applications to the analysis of samples from historical paintings. 相似文献
14.
Bruno Charlier Albino Coglianese Francesca Felicia Operto Giangennaro Coppola Ugo de Grazia Pierantonio Menna Amelia Filippelli Fabrizio Dal Piaz Viviana Izzo 《Molecules (Basel, Switzerland)》2022,27(21)
Cenobamate (CNB) is the newest antiseizure medication (ASM) approved by the FDA in 2019 to reduce uncontrolled partial-onset seizures in adult patients. Marketed as Xcopri in the USA or Ontozry in the EU (tablets), its mechanism of action has not been fully understood yet; however, it is known that it inhibits voltage-gated sodium channels and positively modulates the aminobutyric acid (GABA) ion channel. CNB shows 88% of oral bioavailability and is responsible for modifying the plasma concentrations of other co-administered ASMs, such as lamotrigine, carbamazepine, phenytoin, phenobarbital and the active metabolite of clobazam. It also interferes with CYP2B6 and CYP3A substrates. Nowadays, few methods are reported in the literature to quantify CNB in human plasma. The aim of this study was to develop and validate, according to the most recent guidelines, an analytical method using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS) to evaluate CNB dosage in plasma samples. Furthermore, we provided a preliminary clinical application of our methodology by evaluating the pharmacokinetic parameters of CNB in two non-adult patients. Plasma levels were monitored for two months. Preliminary data showed a linear increase in plasma CNB concentrations, in both patients, in agreement with the increase in CNB dosage. A seizure-free state was reported for both patients at the dose of 150 mg per day. 相似文献
15.
A series of 7-chloro-1,4-dihydro-6-fluoro-1-[(2-methylthiazolyl)methyl]-4-oxoquinoline carboxylic esters 5 has been prepared. Dehydration of the intermediates 4-hydroxythiazolines 4 with trifluoroacetic anhydride resulted in the formation of a ylid 11 . Evidence for this was obtained by the X-ray analysis of the analogous product obtained in reactions carried out with 4-pyridone. 相似文献
16.
Gianluca Melillo Lorella Izzo Roberto Centore Angela Tuzi Alexander Z. Voskoboynikov Leone Oliva 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):29-33
The meso ansa zirconocene with dimethylsilyl bridge, activated by methylalumoxane, catalyses the ethylene polymerization, producing ethyl-branched polyethylene. With respect to the polymers obtained with the previously investigated meso zirconocenes, we have found higher branching amount and lower molecular weight. The rapid β-H transfer from the growing chain to the coordinated monomer could account for both these features of the polymer. The investigation on the structural parameters of the complex, through X-ray diffraction analysis, and on the electrophilicity of the cationic center, through NMR experiments, suggests, as a possible rationalization of this behavior, the obstruction in the inward site. 相似文献
17.
A method is described to screen bulk pharmaceuticals and their synthetic intermediates for common anions. Capillary electrophoresis (CE) is a rapid separation technique which operates on the basis of the differential migration of charged and uncharged species in an electric field. Capillary ion electrophoresis utilizes the principles of CE in combination with an osmotic flow modifier and indirect UV detection for the rapid determination and quantification of ions. A Waters Quanta 4000 capillary electrophoresis system, equipped with a 60 cm × 75 μm I.D. fused-silica capillary in conjunction with a patented chromate buffer and osmotic flow modifier is used. The detection limit of the assay is 0.5 μ/ml for most anions. Parameters have been optimized so that all analytes migrate within 5.0 min. A number of optimization experiments for parameters such as loading time, voltage, linearity, precision and detection limit of the system are demonstrated. The effects of the presence of organic solvents in the sample diluents on the migration times of anions are examined. Applications of the technique to pravastatin sodium, taxol and iopiperidol are illustrated. Comparison to ion chromatography, advantages and disadvantages, is discussed. 相似文献
18.
Andrea Tagliabue Lorella Izzo Massimo Mella 《Journal of Polymer Science.Polymer Physics》2019,57(9):491-510
Absorption of weak polyelectrolytes impacts on properties such as ionization, conformations, and counterion (CI) condensation that are important in several areas of applied and fundamental science. We used a weak polyelectrolyte model and Monte Carlo simulations to investigate how the mentioned properties depend on pH or the size of a spherical cavity (SC) permeable to CIs but not to polyelectrolytes; the latter have either linear or starlike topologies and may be allowed to form charged hydrogen bonds (c? H‐bonds) between ionized and neutral monomers. Average ionization decreases upon increasing the number of arms at a constant number of monomers; it instead increases with the arm length in large SC due to CI screening. The way SC size, c? H‐bonds, and pH values interrelate to define ionization is instead more complicate due to arm pairing or clustering when c? H‐bonds are possible. These induce oscillations in the arm local ionization and impact on both monomer and CI distributions in the complete simulation cell in a way that also depends on polymer topology. The impact of ionization on the confinement free energy is also estimated; this highlighted that c? H‐bonding may enhance absorption compared with neutral chains. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 491–510 相似文献
19.
Grazia Bencivenni Dr. Diana Salazar Illera Dr. Maria Moccia Prof. K. N. Houk Dr. Joseph A. Izzo Dr. Johanna Novacek Prof. Paolo Grieco Prof. Mathew J. Vetticatt Prof. Mario Waser Prof. Mauro F. A. Adamo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(44):11352-11366
Chiral phase-transfer catalysis provides high level of enantiocontrol, however no experimental data showed the interaction of catalysts and substrates. 1H NMR titration was carried out on Cinchona and Maruoka ammonium bromides vs. nitro, carbonyl, heterocycles, and N−F containing compounds. It was found that neutral organic species and quaternary ammonium salts interacted via an ensemble of catalyst +N−C−H and (sp2)C−H, specific for each substrate studied. The correspondent BArF salts interacted with carbonyls via a diverse set of +N−C−H and (sp2)C−H compared to bromides. This data suggests that BArF ammonium salts may display a different enantioselectivity profile. Although not providing quantitative data for the affinity constants, the data reported proofs that chiral ammonium salts coordinate with substrates, prior to transition state, through specific C−H positions in their structures, providing a new rational to rationalize the origin of enantioselectivity in their catalyses. 相似文献
20.
The enantioselective synthesis of 1-(R)-hydroxypolygodial and its epimer at C-9 is described. α-Ionone was the starting material. Key steps of these syntheses included a Corey-Bakshi-Shibata oxazaborolidine-mediated reduction and a stereoselective Diels-Alder reaction. No vanilloid activity was detected for both compounds in assays on VR1 vanilloid receptor in HEK cells transfected with the human VR1. 相似文献