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101.
Juan M. Asensio Ana B. Miguel Pier‐Francesco Fazzini Piet W. N. M. vanLeeuwen Bruno Chaudret 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11428-11432
Magnetic heating has recently been demonstrated as an efficient way to perform catalytic reactions after deposition of the heating agent and the catalyst on a support. Here we show that in solution, and under mild conditions of mean temperature and pressure, it is possible to use magnetic heating to carry out transformations that are otherwise performed heterogeneously at high pressure and/or high temperature. As a proof of concept, we chose the hydrodeoxygenation of acetophenone derivatives and of biomass‐derived molecules, namely furfural and hydroxymethylfurfural. These reactions are difficult, require heterogeneous catalysts and high pressures, and, to the best of our knowledge, have no precedent in standard solution. Here, hydrodeoxygenations are fully selective under mild conditions (3 bar H2, moderate mean temperature of the solvent). The reason for this reactivity is the fast heating of the particles well above the boiling temperature of the solvent and the local creation of hot spots surrounded by a vapor layer, in which high temperature and pressure may be present. This technology may be practicable for many organic transformations. 相似文献
102.
Essential embedding of cyclic modules in projectives 总被引:2,自引:0,他引:2
José L. Gó mez Pardo Pedro A. Guil Asensio 《Transactions of the American Mathematical Society》1997,349(11):4343-4353
Let be a ring and its injective envelope. We show that if every simple right -module embeds in and every cyclic submodule of is essentially embeddable in a projective module, then has finite essential socle. As a consequence, we prove that if each finitely generated right -module is essentially embeddable in a projective module, then is a quasi-Frobenius ring. We also obtain several other applications and, among them: a) we answer affirmatively a question of Al-Huzali, Jain, and López-Permouth, by showing that a right CEP ring (i.e., a ring such that every cyclic right module is essentially embeddable in a projective module) is always right artinian; b) we prove that if is right FGF (i.e., any finitely generated right -module embeds in a free module) and right CS, then is quasi-Frobenius.
103.
104.
Asensio JL Hidalgo A Bastida A Torrado M Corzana F Chiara JL García-Junceda E Cañada J Jiménez-Barbero J 《Journal of the American Chemical Society》2005,127(23):8278-8279
Herein, we describe how the conformational differences exhibited by aminoglycosides in the binding pockets of the ribosome and those enzymes involved in bacterial resistance can be exploited in the design of new antibiotic derivatives with improved activity in resistant strains. The simple modification shown in the figure, leading to the conformationally restricted 5, provides an effective protection against aminoglycoside inactivation by Staphylococcus aureus ANT4, both in vivo and in vitro. 相似文献
105.
Chávez MI Andreu C Vidal P Aboitiz N Freire F Groves P Asensio JL Asensio G Muraki M Cañada FJ Jiménez-Barbero J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(23):7060-7074
The specific interaction of a variety of modified hevein domains to chitooligosaccharides has been studied by NMR spectroscopy in order to assess the importance of aromatic-carbohydrate interactions for the molecular recognition of neutral sugars. These mutant AcAMP2-like peptides, which have 4-fluoro-phenylalanine, tryptophan, or 2-naphthylalanine at the key interacting positions, have been prepared by solid-phase synthesis. Their three-dimensional structures, when bound to the chitin-derived trisaccharide, have been deduced by NMR spectroscopy. By using DYANA and restrained molecular dynamics simulations with the AMBER 5.0 force field, the three-dimensional structures of the protein-sugar complexes have been obtained. The thermodynamic analysis of the interactions that occur upon complex formation have also been carried out. Regarding binding affinity, the obtained data have permitted the deduction that the larger the aromatic group, the higher the association constant and the binding enthalpy. In all cases, entropy opposes binding. In contrast, deactivation of the aromatic rings by attaching fluorine atoms decreases the binding affinity, with a concomitant decrease in enthalpy. The role of the chemical nature of the aromatic ring for establishing sugar contacts has been thus evaluated. 相似文献
106.
M. Sc. Juan M. Asensio Dr. Simon Tricard Dr. Yannick Coppel Dr. Román Andrés Prof. Dr. Bruno Chaudret Prof. Dr. Ernesto de Jesús 《Angewandte Chemie (International ed. in English)》2017,56(3):865-869
The coordination of N-heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC PdII complex. NMR studies after 13CO adsorption established that the KS shifts the 13C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight-shifted to 600 ppm for 13C-labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car–Purcell–Meiboom–Gill (CPMG) echo train acquisition NMR experiments. 相似文献
107.
Deciphering the Non‐Equivalence of Serine and Threonine O‐Glycosylation Points: Implications for Molecular Recognition of the Tn Antigen by an anti‐MUC1 Antibody 下载免费PDF全文
Dr. Nuria Martínez‐Sáez Jorge Castro‐López Jessika Valero‐González Dr. David Madariaga Ismael Compañón Dr. Víctor J. Somovilla Míriam Salvadó Dr. Juan L. Asensio Dr. Jesús Jiménez‐Barbero Dr. Alberto Avenoza Dr. Jesús H. Busto Dr. Gonçalo J. L. Bernardes Dr. Jesús M. Peregrina Dr. Ramón Hurtado‐Guerrero Dr. Francisco Corzana 《Angewandte Chemie (International ed. in English)》2015,54(34):9830-9834
The structural features of MUC1‐like glycopeptides bearing the Tn antigen (α‐O‐GalNAc‐Ser/Thr) in complex with an anti MUC‐1 antibody are reported at atomic resolution. For the α‐O‐GalNAc‐Ser derivative, the glycosidic linkage adopts a high‐energy conformation, barely populated in the free state. This unusual structure (also observed in an α‐S‐GalNAc‐Cys mimic) is stabilized by hydrogen bonds between the peptidic fragment and the sugar. The selection of a particular peptide structure by the antibody is thus propagated to the carbohydrate through carbohydrate/peptide contacts, which force a change in the orientation of the sugar moiety. This seems to be unfeasible in the α‐O‐GalNAc‐Thr glycopeptide owing to the more limited flexibility of the side chain imposed by the methyl group. Our data demonstrate the non‐equivalence of Ser and Thr O‐glycosylation points in molecular recognition processes. These features provide insight into the occurrence in nature of the APDTRP epitope for anti‐MUC1 antibodies. 相似文献
108.
Supercritical carbon dioxide (scCO2) is an efficient reaction medium to perform the Baeyer-Villiger oxidation with hydrated silica-supported potassium peroxomonosulfate (h-SiO2.KHSO5) under flow-through conditions. Hydration modulates the reactivity of the active surface by softening the acidity of the KHSO4 present in the supported reagent. The reaction in scCO2 is much more efficient than in n-hexane under similar conditions, which is attributed to better transport and solvating properties of the supercritical medium with regard to n-hexane. 相似文献
109.
María Machín‐Sánchez María Asensio‐Ramos Javier Hernández‐Borges María Candelaria Gil‐Rodríguez 《Journal of separation science》2014,37(6):711-716
The use of CE–ESI‐MS has been considered as a new chemical strategy for the possible discernment of genera and species of the Laurencia complex. After the selection of the CE–MS and the extraction conditions, a total of 28 specimens of the complex, including different species of four genera (Laurencia, Laurenciella, Palisada, and Osmundea) collected from five intertidal locations on the Island of Tenerife (Canary Islands, Spain) were analyzed. CE–MS fingerprints revealed that CE–MS can be used as a useful tool for these studies in order to assess similarities and differences between them and that it constitutes an important starting point for further studies in the field. 相似文献
110.
Modulating Weak Interactions for Molecular Recognition: A Dynamic Combinatorial Analysis for Assessing the Contribution of Electrostatics to the Stability of CH–π Bonds in Water 下载免费PDF全文
Ester Jiménez‐Moreno Dr. Ana M. Gómez Dr. Agatha Bastida Dr. Francisco Corzana Dr. Gonzalo Jiménez‐Oses Dr. Jesús Jiménez‐Barbero Dr. Juan Luis Asensio 《Angewandte Chemie (International ed. in English)》2015,54(14):4344-4348
Electrostatic and charge‐transfer contributions to CH–π complexes can be modulated by attaching electron‐withdrawing substituents to the carbon atom. While clearly stabilizing in the gas phase, the outcome of this chemical modification in water is more difficult to predict. Herein we provide a definitive and quantitative answer to this question employing a simple strategy based on dynamic combinatorial chemistry. 相似文献