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111.
Emiliano Manzo Maria Letizia Ciavatta Margherita Gavagnin Chandrakant Govind Naik 《Tetrahedron letters》2007,48(14):2569-2571
Chemical analysis of the secondary metabolite pattern of the gorgonian Echinogorgia complexa, collected along South Indian coasts, showed the presence of two new tricyclic guaiane furanosesquiterpenes, iso-echinofuran (3) and 8,9-dihydro-linderazulene (4), co-occurring with the known echinofuran (5) and structurally related to the pigment linderazulene (1). The unprecedented molecules 3 and 4 were characterized by spectral methods, mainly by NMR techniques. Compounds 3-5 displayed moderate activity in the mitochondrial respiratory chain inhibition assay. 相似文献
112.
Vattuone L Savio L Gerbi A Okada M Moritani K Rocca M 《The journal of physical chemistry. B》2007,111(7):1679-1683
We have investigated oxygen adsorption on Cu(410) by high-resolution electron energy loss spectroscopy, dosing O2 with a supersonic molecular beam at different surface temperatures and for different angles of incidence and beam energies or by backfilling. In the investigated crystal temperature range (127 < T < 570 K), adsorption is always dissociative. Depending on T, impact energy, and angle of incidence, the oxygen atoms end up in different adsorption configurations, characterized by different vibrational signatures. In particular, at grazing incidence when only the step edge is exposed to O2, the adatoms end up initially preferentially at the step edge. An ordered overlayer forms at half monolayer coverage when the adsorbate is mobile. Oxide patches develop eventually for large exposures performed by backfilling and at high crystal temperature. 相似文献
113.
114.
Silvia Ghirga Letizia Chiodo Riccardo Marrocchio Javier G. Orlandi Alessandro Loppini 《Entropy (Basel, Switzerland)》2021,23(9)
The comprehension of neuronal network functioning, from most basic mechanisms of signal transmission to complex patterns of memory and decision making, is at the basis of the modern research in experimental and computational neurophysiology. While mechanistic knowledge of neurons and synapses structure increased, the study of functional and effective networks is more complex, involving emergent phenomena, nonlinear responses, collective waves, correlation and causal interactions. Refined data analysis may help in inferring functional/effective interactions and connectivity from neuronal activity. The Transfer Entropy (TE) technique is, among other things, well suited to predict structural interactions between neurons, and to infer both effective and structural connectivity in small- and large-scale networks. To efficiently disentangle the excitatory and inhibitory neural activities, in the article we present a revised version of TE, split in two contributions and characterized by a suited delay time. The method is tested on in silico small neuronal networks, built to simulate the calcium activity as measured via calcium imaging in two-dimensional neuronal cultures. The inhibitory connections are well characterized, still preserving a high accuracy for excitatory connections prediction. The method could be applied to study effective and structural interactions in systems of excitable cells, both in physiological and in pathological conditions. 相似文献
115.
Alessio Cesaretti Letizia Mencaroni Carmela Bonaccorso Valentina Botti Eleonora Calzoni Benedetta Carlotti Cosimo Gianluca Fortuna Nicol Montegiove Anna Spalletti Fausto Elisei 《Molecules (Basel, Switzerland)》2022,27(12)
Small organic molecules arouse lively interest for their plethora of possible biological applications, such as anticancer therapy, for their ability to interact with nucleic acids, or bioimaging, thanks to their fluorescence emission. Here, a panchromatic series of styryl-azinium bicationic dyes, which have already proved to exhibit high water-solubility and significant red fluorescence in water, were investigated through spectrofluorimetric titrations to assess the extent of their association constants with DNA and RNA. Femtosecond-resolved transient absorption spectroscopy was also employed to characterize the changes in the photophysical properties of these fluorophores upon interaction with their biological targets. Finally, in vitro experiments conducted on tumor cell lines revealed that some of the bicationic fluorophores had a peculiar localization within cell nuclei exerting important antiproliferative effects, others were instead found to localize in the cytoplasm without leading to cell death, being useful to mark specific organelles in light of live cell bioimaging. Interestingly, this molecule-dependent behavior matched the different amphiphilicity featured by these bioactive compounds, which are thus expected to be caught in a tug-of-war between lipophilicity, ensured by the presence of aromatic rings and needed to pass cell membranes, and hydrophilicity, granted by charged groups and necessary for stability in aqueous media. 相似文献
116.
Emiliano Manzo Dario Pagano Genoveffa Nuzzo Margherita Gavagnin Maria Letizia Ciavatta 《Tetrahedron letters》2012,53(52):7083-7084
Parazoanthine A (7.0% overall yield) and its O-methyl derivative (6.2% overall yield) were prepared by a concise biomimetic synthesis based on the coupling reaction of l-arginine methyl ester dihydrochloride with isocyanate derivatives of p-coumaric acid and 4-methoxy-cinnamic acid, respectively. The synthetic approach is designed to obtain a wider class of parazoanthine analogs. 相似文献
117.
Patrizia Galzerano Dario Agostino Giorgio Bencivenni Dr. Letizia Sambri Dr. Giuseppe Bartoli Prof. Paolo Melchiorre Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):6069-6076
A simple and convenient method for the direct, aminocatalytic, and highly enantioselective Mannich reactions of aldehydes with in situ generated N‐carbamoyl imines has been developed. Both α‐imino esters and aromatic imines serve as suitable electrophilic components. Moreover, the judicious selection of commercially available secondary amine catalysts allows selective access to the desired stereoisomer of the N‐tert‐butoxycarbonyl (Boc) or N‐carbobenzyloxy (Cbz) Mannich adducts, with high control over the syn or anti relative configuration and almost perfect enantioselectivity. Besides the possibility to fully control the stereochemistry of the Mannich reaction, the main advantage of this method lies in the operational simplicity; the highly reactive N‐carbamate‐protected imines are generated in situ from stable and easily handled α‐amido sulfones. 相似文献
118.
Bartoli G Bosco M Carlone A Dalpozzo R Locatelli M Melchiorre P Sambri L 《The Journal of organic chemistry》2006,71(26):9580-9588
The reaction between alcohols and Boc2O leads to the formation of tert-butyl ethers and/or Boc-alcohols, depending on the nature of the Lewis acid catalyst. Product distribution is mainly tuned by the anionic part of the salt. Perchlorates and triflates, anions with highly delocalized negative charge, give prevalent or exclusive ether formation. On the other hand, Boc alcohols are the main or exclusive products with un-delocalized isopropoxide or low-delocalized acetate ions. The metal ion influences only the reaction rate, roughly following standard parameters for calculating Lewis acidity. A reaction mechanism is supposed, and a series of experimental evidences is reported to support it. These studies allowed us to conclude that, to synthesize tert-butyl ethers, in reactions involving aliphatic alcohols, Mg(ClO4)2 or Al(ClO4)3 represents the best compromise between costs and efficiency of the reaction, while, in reactions involving phenols, Sc(OTf)3 is the best choice, since aromatic tert-butyl ethers are not stable in the presence of perchlorates. 相似文献
119.
Maria Letizia Bertotti Marcello Delitala 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2010,61(4):583-602
In this paper we formulate a discrete version of the bounded confidence model (Deffuant et al. in Adv Complex Syst 3:87–98, 2000; Weisbuch et al. in Complexity 7:55–63, 2002), which is representable as a family of ordinary differential equation systems. Then, we analytically study these systems. We establish the existence of equilibria which correspond to opinion profiles displaying a finite number of isolated clusters. We prove the asymptotic stability of some of these equilibria and show that they represent the asymptotic trend of the solutions of the systems under consideration. For a particular case, we also characterize the initial profiles that lead to different cluster configurations. 相似文献
120.
Maria Letizia De Marco Dr. Sanaa Semlali Prof. Brian A. Korgel Dr. Philippe Barois Dr. Glenna L. Drisko Dr. Cyril Aymonier 《Angewandte Chemie (International ed. in English)》2018,57(17):4478-4498
Metamaterials have optical properties that are unprecedented in nature. They have opened new horizons in light manipulation, with the ability to bend, focus, completely reflect, transmit, or absorb an incident wave front. Optically active metamaterials in particular could be used for applications ranging from 3D information storage to photovoltaic cells. Silicon (Si) particles are some of the most promising building blocks for optically active metamaterials, with high scattering efficiency coupled to low light absorption for visible frequencies. However, to date ideal Si building blocks cannot be produced by bulk synthesis techniques. The key is to find a synthetic route to produce Si building blocks between 75–200 nm in diameter of uniform size and shape, that are crystalline, have few impurities, and little to no porosity. This Review provides a theoretical background on Si optical properties for metamaterials, an overview of current synthetic methods and gives direction towards the most promising routes to ideal Si particles for metamaterials. 相似文献