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41.
The nucleophilic aromatic substitution of some activated aryl or heteroaryl halides has been performed in ionic liquid solution, using the 1-butyl-3-methylimidazolium azide as a nucleophile. The reaction course was studied varying the structures of both substrates and ionic liquids. In particular, in the latter case, the reaction of 2-bromo-5-nitrothiophene was carried out in five different ionic liquids ([bmim][BF 4], [bmim][PF 6], [bmim][NTf 2], [bm 2im][NTf 2], and [bmpyrr][NTf 2]). Finally, for all the substrates considered, a comparison with data obtained in MeOH solution in the presence of NaN 3 was also performed. Data collected indicate that in some cases it is possible to obtain aromatic or heteroaromatic azide derivatives in satisfactory yield by means of a S NAr reaction using [bmim][N 3] as the nucleophile. 相似文献
42.
The amino induced elimination of benzisoxazole into the relevant o-cyanophenolate ion (Kemp elimination) has been studied in [bmim][BF 4] solution at 298 K. To have information about the interactions between reactants and ionic liquid, the reaction has been carried out at different temperatures (293-313 K). Several primary, secondary, and tertiary amines have been used to study the effect of amine structure on the reaction rate. The collected data show that the amine structure seems to have a crucial role in determining the reaction rate. Furthermore, as different cation or anion structures of an ionic liquid can significantly affect its properties, the title reaction has been performed in four different ionic liquids ([bmim][PF6], [bmim][NTf 2], [bm 2im][NTf 2], and [bmpyrr][NTf 2]), using pyrrolidine and piperidine as model amines. An H-donor negative solvent (MeOH and [bmim][NTf 2]) effect on reaction rate was detected. Finally, a narrow range of activation parameters was calculated both for the reaction induced by different amines and for pyrrolidine and piperidine, in the presence of different ILs. This fact suggests the occurrence of an "early" transition state. 相似文献
43.
Guernelli S Fontana A Noto R Spinelli D Turco Liveri ML 《Journal of colloid and interface science》2012,370(1):67-72
The pH-induced swelling of poly(2-vinylpyridine) microgel particles was studied using dynamic light scattering. The increase in particle diameter with decreasing pH was modeled using a well-established thermodynamic model for microgel swelling. The Maxwell construction was applied to extend the model and yield a prediction for a pH-responsive microgel across the entire pH range. The model predicts a first order phase transition for polymer-solvent combinations with a Flory interaction parameter, χ, greater than a critical value χ(c). The modified theory compared favorably to the dynamic light scattering data for the hydrodynamic diameter of microgel particles based on 2-vinylpyridine at different pH values. In particular, the swelling transition is both predicted theoretically and observed experimentally to occur at a pH lower than the pK(a) of the polymer. 相似文献
44.
Intramolecular oxa-conjugate cyclization (IOCC) of α,β-unsaturated carbonyl compounds, triggered by deprotonation with a base, represents a straightforward method for the synthesis of tetrahydropyrans. However, it has been known that stereochemical outcome of IOCC depends on the local structure of substrates and sometimes requires harsh reaction conditions and/or prolonged reaction times for selective formation of 2,6-cis-substituted tetrahydropyrans. These shortcomings limit the feasibility of IOCC in the context of complex natural product synthesis. In this paper, we describe Br?nsted acid-catalyzed IOCC of α,β-unsaturated ester surrogates (e.g., α,β-unsaturated thioesters, oxazolidinone imides, and pyrrole amides) under mild reaction conditions, which affords a series of synthetically versatile 2,6-cis-substituted tetrahydropyran derivatives with good to excellent stereoselectivity (dr from 7:1 to >20:1). These α,β-unsaturated carbonyl compounds were found to be more reactive than the corresponding oxoesters that are generally unreactive toward Br?nsted acid-catalyzed intramolecular oxa-conjugate additions. The product tetrahydropyrans could be transformed into various derivatives in an efficient manner, highlighting the usefulness of our methodology. 相似文献
45.
Hajimo Yoshida Takejiro Kaneko Hiroyasu Fujimori Hiroaki Morita Koshichi Noto Kazuo Kamigaki 《高压研究》2013,33(1-6):114-116
Abstract The effect of pressure on Tc was studied on 110 K class Bi-Sr-Ca-Cu-O (1:1:1:2) compounds. Tc was varied with current in I3/2 , and defined at the value extrapolated to zero current. dTc /dP = + 0.18 K/kbar was obtained up to 10.9 kbars. 相似文献
46.
Francesca D'Anna Dr. Francesco Ferrante Dr. Renato Noto Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(47):13059-13068
Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3′‐di‐n‐butyl‐1,1′‐(1,3‐phenylenedimethylene)diimidazolium and 3,3′‐di‐n‐butyl‐1,1′‐(1,4‐phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co‐solvent such as methanol. 相似文献
47.
Aldona Kostuch Iwona A. Rutkowska Beata Dembinska Anna Wadas Enrico Negro Keti Vezz Vito Di Noto Pawel J. Kulesza 《Molecules (Basel, Switzerland)》2021,26(17)
Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O2-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, Ta2O5, Nb2O5, and ZrO2), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi- and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt–Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal–support interactions and interfacial structural changes affecting adsorption and activation of O2-molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional. 相似文献
48.
Noriaki Miura Yuuki Noto Shuusuke Kato Fumihito Yokoyama Susumu Kuwamura Naoshi Baba Yoichiro Hanaoka Shin’ichi Nagata Satoru Ueno Reizaburou Kitai Kiyoshi Ichimoto Hideki Takami 《Optical Review》2009,16(5):558-561
A solar adaptive optics system has been improved by using a high-speed electromagnetic deformable mirror and adopting a modified sum-of-absolute-differences algorithm in wavefront sensing. Results of laboratory experiments clearly show that the use of the mirror raises the temporal performance of the system. In solar observations, wavefront compensation using solar granules as a target is realized. 相似文献
49.
50.
Silvia Todros Arturo N. Natali Giuseppe Pace Vito Di Noto 《Journal of Polymer Science.Polymer Physics》2014,52(5):409-418
The effect of steam on chemical structure and mechanical properties of renewable poly(ether‐block‐amide)s (PEBAs) is investigated by different characterization techniques, i.e. FT‐IR, TGA, DSC, DMA, and BES. Steam sterilization is a mandatory process for materials used in medical applications. This process, employed during clinical practice and replicated in this study, affects polymer structure and morphology. Steam induces an increase of polyamide (PA) crystallinity in PEBAs with a majority of PA domains, due to the conformational transition from α‐helix to parallel and anti‐parallel β‐sheet, with stronger hydrogen bonding. In PEBAs with longer polyether (PE) blocks, steam induces an increase of random PA domains and the formation of a more extended hydrogen bonding network between ether and amide moieties of the two segments. As a consequence of these microdomain conformational variations, relevant changes occur in molecular relaxations as demonstrated by DMA and BES results. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 409–418 相似文献