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排序方式: 共有159条查询结果,搜索用时 15 毫秒
51.
Maria E. Angelaki Manolis N. Romanias James B. Burkholder Vassileios C. Papadimitriou 《国际化学动力学杂志》2024,56(3):119-130
Rate coefficients, k1, for the gas-phase OH radical reaction with the heterocyclic ether C4H4O (1,4-epoxybuta-1,3-diene, furan) were measured over the temperature range 273–353 K at 760 Torr (syn. air). Experiments were performed using: (i) the photochemical smog chamber THALAMOS (thermally regulated atmospheric simulation chamber, IMT NE, Douai-France) equipped with Fourier Transform Infrared (FTIR) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) detection methods and (ii) a photochemical reactor coupled with FTIR spectroscopy (PCR, University of Crete, Greece). k1(273–353 K) was measured using a relative rate (RR) method, in which the loss of furan was measured relative to the loss of reference compounds with well-established OH reaction rate coefficients. k1(273–353 K) was found to be well represented by the Arrhenius expression (1.30 ± 0.12) × 10−11 exp[(336 ± 20)/T] cm3 molecule−1 s−1, with k1(296 K) measured to be (4.07 ± 0.32) × 10−11 cm3 molecule−1 s−1. The k1(296 K) and pre-exponential quoted error limits are 2σ and include estimated systematic errors in the reference rate coefficients. The observed negative temperature dependence is consistent with a reaction mechanism involving the OH radical association to a furan double bond. Quantum mechanical molecular calculations show that OH addition to the α-carbon (ΔHr(296 K) = −121.5 kJ mol−1) is thermochemically favored over the β-carbon (ΔHr(296 K) = −52.9 kJ mol−1) addition. The OH-furan adduct was found to be stable over the temperature range of the present measurements. Maleic anhydride (C4H2O3) was identified as a minor reaction product, 3% lower-limit yield, demonstrating a non-ring-opening active reaction channel. The present results are critically compared with results from previous studies of the OH + furan reaction rate coefficient. The infrared spectrum of furan was measured as part of this study and its estimated climate metrics are reported. 相似文献
52.
S.S. Hasnain T.D.S. Hamilton I.H. Munro E. Pantos 《Journal of Molecular Spectroscopy》1978,72(3):406-422
Absorption and luminescence excitation spectra of solid benzene and benzene isolated in rare-gas matrices have been studied. The absolute absorption cross sections of various electronic band systems including the Rydberg region of C6H6 are obtained using transmission spectra of C6H6-doped rare-gas films of different thickness. An interpretation of the structure in the Rydberg region is given in terms of two Rydberg series using the quantum defect method. A comparative study has been made of luminescence excitation spectra of matrix-isolated and of pure C6H6. The luminescence excitation spectra of matrix-isolated benzene gives information on the internal conversion and medium-induced vibrational relaxation. 相似文献
53.
Kyriaki S. Pafiti Eleni J. Kepola Manolis C. Vlasiou Edna N. Yamasaki Costas S. Patrickios Nikolaos P. Mastroyiannopoulos Leonidas A. Phylactou Patrick Théato 《Journal of polymer science. Part A, Polymer chemistry》2021,59(10):870-881
The present study aims to investigate an odd–even effect of the number of ethylene imine units in the side-groups of totally abiotic synthetic polymers on their efficiency in DNA transfection. A library of fifteen polymers was fabricated. Two star homopolymers and one linear homopolymer based on glycidyl methacrylate were synthesized and used as precursors to which five linear oligo(ethylene imine)s (OEI) were grafted. The number of ethylene imine groups of the OEIs was varied. Specifically, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine were used. Each of these fifteen OEI-grafted polymers was evaluated in terms of their efficiency to transfer plasmid DNA encoding firefly luciferase in C2C12 mouse myoblast cells. The transfection efficiency displayed an odd-even pattern, with all OEI-grafted polymers with an odd number of ethylene imine repeating units exhibiting higher transfection efficiency compared with those possessing an even number of ethylene imine repeating units. The odd–even effect was more pronounced for the star polymers with longer arms (degree of polymerization, DP = 100), while in case of the linear polymers, the odd–even effect was only observed for the lowest polymer loading. The cytotoxicity of the OEI-grafted polymers also followed an odd–even pattern, with the OEI-grafted star polymers with an arm DP of 100 and the linear polymers clearly presenting an odd-even effect, while the cytotoxicity of the OEI-grafted star polymers with an arm DP of 20 slightly increased with the number of ethylene imine repeating units. 相似文献
54.
Dr. Dimitris Kalaitzakis Myron Triantafyllakis Ioanna Alexopoulou Manolis Sofiadis Prof. Dr. Georgios Vassilikogiannakis 《Angewandte Chemie (International ed. in English)》2014,53(48):13201-13205
A highly efficient one‐pot transformation of readily accessible furans into 4‐hydroxy‐2‐cyclopentenones in H2O, using singlet oxygen as oxidant, has been developed. 相似文献
55.
Ilias Malgarinos Nikolaos Nikolopoulos Marco Marengo Carlo Antonini Manolis Gavaises 《Advances in colloid and interface science》2014
Introduction
In this study,a novel numerical implementation for the adhesion of liquid droplets impacting normally on solid dry surfaces is presented. The advantage of this new approach, compared to the majority of existing models, is that the dynamic contact angle forming during the surface wetting process is not inserted as a boundary condition, but is derived implicitly by the induced fluid flow characteristics (interface shape) and the adhesion physics of the gas–liquid-surface interface (triple line), starting only from the advancing and receding equilibrium contact angles. These angles are required in order to define the wetting properties of liquid phases when interacting with a solid surface.Methodology
The physical model is implemented as a source term in the momentum equation of a Navier-Stokes CFD flow solver as an “adhesion-like” force which acts at the triple-phase contact line as a result of capillary interactions between the liquid drop and the solid substrate. The numerical simulations capture the liquid–air interface movement by considering the volume of fluid (VOF) method and utilizing an automatic local grid refinement technique in order to increase the accuracy of the predictions at the area of interest, and simultaneously minimize numerical diffusion of the interface.Results
The proposed model is validated against previously reported experimental data of normal impingement of water droplets on dry surfaces at room temperature. A wide range of impact velocities, i.e. Weber numbers from as low as 0.2 up to 117, both for hydrophilic (θadv = 10° – 70°) and hydrophobic (θadv = 105° – 120°) surfaces, has been examined. Predictions include in addition to droplet spreading dynamics, the estimation of the dynamic contact angle; the latter is found in reasonable agreement against available experimental measurements.Conclusion
It is thus concluded that theimplementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as an approximate boundary condition for such simulations. Clearly, this model is mostly influential during the spreading phase for the cases of low We number impacts (We < ˜80) since for high impact velocities, inertia dominates significantly over capillary forces in the initial phase of spreading. 相似文献56.
Lykakis IN Psyllaki A Stratakis M 《Journal of the American Chemical Society》2011,133(27):10426-10429
Gold nanoparticles supported on TiO(2) (0.1-1% mol) catalyze at room temperature and at extremely mild conditions the unprecedented oxidative cycloaddition of 1,1,3,3-tetramethyldisiloxane to alkynes, forming substituted 2,5-dihydro-1,2,5-oxadisiloles, with concomitant evolution of hydrogen gas. For the majority of the substrates, the yields are exceptional (up to 99%). The reaction proceeds at room temperature, tolerates a variety of functional groups, and can be performed in several solvents. 相似文献
57.
Sotirios I. Pantos Ekaterini Tiligada 《International journal of quantum chemistry》2013,113(8):1095-1106
Residual dipolar couplings (RDC) of proteins dissolved in anisotropic media promise to speed up the determination of protein structures. We consider the backbone as a robotic mechanism and formulate inverse kinematics problems using RDC restraints from two media. The φ, ψ of each secondary structure element (SSE) are computed from oriented vectors in consecutive peptide planes. We search for the optimum conformation joining the solutions of two independent backbone halves. The matrix transforming the vector Z of a global frame from one SSE into the other determines their orientation. Three distance constraints between two oriented SSE determine their relative position by solving nine polynomial equations. The benefit of this method is that complete and accurate solutions are obtained overcoming the local minima problems of heuristic procedures. The algorithm is implemented on MAPLE using the least number of experimental data; the runtimes take an order of seconds on a common PC. © 2013 Wiley Periodicals, Inc. 相似文献
58.
L. Bertrand D. Vantelon E. Pantos 《Applied Physics A: Materials Science & Processing》2006,83(2):225-228
The information that can be retrieved from the study of ancient materials and studies on their conservation rely strongly
on the development and application of new techniques of physical analysis. This is particularly important at a time when global
changes affecting our environment and way of life impose new stresses putting heritage preservation at risk. For this purpose,
synchrotron techniques are particularly suited to the non- (or micro-) destructive characterisation of such heterogeneous
materials, and a steep increase in the number of publications has been noticed recently from cultural heritage works using
synchrotron radiation.
In 2004, an interface dedicated to archaeology and cultural heritage was launched at the SOLEIL synchrotron to allow researchers
from the international scientific community to be granted specific expertise. This interface aims at easing the access of
researchers to the synchrotron, facilitating contacts, providing technical support and informing the community. The very first
applications of SOLEIL beamlines in the heritage field are illustrated through works recently carried out at the first beamline
of SOLEIL, LUCIA, currently located at the Swiss Light Source (SLS). The setup of the beamline is succinctly described.
PACS 07.85.Qe; 87.59.-e 相似文献
59.
Marshall LJ Almond MJ Cook SR Pantos M Tobin MJ Thomas LA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):854-861
Mineralised organic remains (including apple pips and cereal grains) collected during the ongoing excavations of Insula IX at the Roman town of Silchester, Hampshire have been analysed by a combination of SEM-EDX, powder XRD and IR spectroscopy. The experiments included mapping experiments using spatially resolved versions of each technique. IR and powder XRD mapping have been carried out utilising the synchrotron source at The Daresbury Laboratory on stations 11.1 and 9.6. It is concluded that these samples are preserved by rapid mineralisation in the carbonate-substituted calcium phosphate mineral, dahllite. The rapid mineralisation leads to excellent preservation of the samples and a small crystal size. The value of IR spectroscopy in studying materials like this where the crystal size is small is demonstrated. A comparison is made between the excellent preservation seen in this context and the much poorer preservation of mineralised remains seen in Context 5276 or Cesspit 5251. Comments on the possible mechanism of mineralisation of these samples are made. 相似文献
60.
Evgeny A. Kataev Patricia Pantos Elizabeth Karnas Grigory V. Kolesnikov Ivan G. Tananaev Vincent M. Lynch 《Supramolecular chemistry》2015,27(5-6):346-356
Cyclo[8]pyrrole, an octapyrrolic expanded porphyrin with no meso-linking atoms, was found to interact with a series of anions in the solid state and in a chloroform solution. The anion selectivities have been determined relative to a structurally characterised salt, H2cyclo[8]pyrrole2+·I? ·I3 ? , via counter anion exchange. Although cyclo[8]pyrrole demonstrates a general selectivity for sulfate, it interacts well with both the pertechnetate and perrhenate anions. Moreover, it has been shown to act as a phase-transfer catalyst facilitating the extraction of pertechnetate from an aqueous to an organic phase in the presence of sulfate. 相似文献