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71.
A repetitive potential cycling procedure was used to produce a specific multilayer hydrous oxide film on copper in base at
60 °C. Such a deposit undergoes reduction in a quasi-reversible manner at ca. −0.1 V (RHE), i.e. at a potential that is unrelated
to Pourbaix data for copper but, as demonstrated previously, is of major significance with regard to the electrocatalytic
behaviour of this electrode system. In accordance with the incipient hydrous oxide/adatom mediator model of electrocatalysis,
an active surface state of the metal (Cu*) is assumed to be involved both in electrocatalysis and as a primary product in
the hydrous oxide reduction reaction. While the latter process occurs very rapidly at −0.1 V, it is not usually reversible
as it is accompanied by subsequent rapid loss of the active state of the metal. The same general approach was used previously
to explain the hydrous oxide and electrocatalytic behaviour of a range of noble metals.
Received: 28 August 1999 / Accepted: 11 November 1999 相似文献
72.
G. T. Jones R. W. L. Jones B. W. Kennedy S. W. O'Neale H. Klein D. R. O. Morrison P. Schmid H. Wachsmuth F. Hamisi D. B. Miller M. M. Mobayyen S. Wainstein M. Aderholz D. Hantke E. Hoffmann U. F. Katz J. Kern N. Schmitz W. Wittek G. Corrigan G. Myatt D. Radojicic P. N. Shotton S. J. Towers F. W. Bullock S. Burke 《Zeitschrift fur Physik C Particles and Fields》1989,44(3):379-384
Within the framework of the quark-parton model, the quark and anti-quark structure functions of the proton have been measured by fitting them to the distributions of the events in the Bjorkeny variable. The data used form the largest sample of neutrino and antineutrino interactions on a pure hydrogen target available, and come from exposures of BEBC to the CERN wide band neutrino and antineutrino beams. It is found that the ratiod v /u v of valence quark distributions falls with increasing Bjorkenx. In the context of the quark-parton model the results constrain the isospin composition of the accompanying diquark system. Models involving scattering from diquarks are in disagreement with the data. 相似文献
73.
Ultrafine grain formation and coating mechanism arising from a blast coating process: A transmission electron microscopy analysis 下载免费PDF全文
Conor F. Dunne Kevin Roche Arne Janssen Xiangli Zhong M.G. Burke Barry Twomey Kenneth T. Stanton 《Surface and interface analysis : SIA》2017,49(12):1271-1278
This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings. 相似文献
74.
S. Dooley M. P. Burke M. Chaos Y. Stein F. L. Dryer V. P. Zhukov O. Finch J. M. Simmie H. J. Curran 《国际化学动力学杂志》2010,42(9):527-549
The oxidation of methyl formate (CH3OCHO) has been studied in three experimental environments over a range of applied combustion relevant conditions:
- 1. A variable‐pressure flow reactor has been used to quantify reactant, major intermediate and product species as a function of residence time at 3 atm and 0.5% fuel concentration for oxygen/fuel stoichiometries of 0.5, 1.0, and 1.5 at 900 K, and for pyrolysis at 975 K.
- 2. Shock tube ignition delays have been determined for CH3OCHO/O2/Ar mixtures at pressures of ≈ 2.7, 5.4, and 9.2 atm and temperatures of 1275–1935 K for mixture compositions of 0.5% fuel (at equivalence ratios of 1.0, 2.0, and 0.5) and 2.5% fuel (at an equivalence ratio of 1.0).
- 3. Laminar burning velocities of outwardly propagating spherical CH3OCHO/air flames have been determined for stoichiometries ranging from 0.8–1.6, at atmospheric pressure using a pressure‐release‐type high‐pressure chamber.
75.
Philip J. Burke William Clegg Terence C. Jenkins Ian T. Meikle 《Tetrahedron letters》2010,51(30):3918-7450
Treatment of the N-nitroaryl-3-hydroxypiperidine derivatives 12 and 13 with thionyl chloride afforded the corresponding N-aryl-2-chloromethylpyrrolidines 5 and 15 via a ring-contraction process involving an intermediate aziridinium ion. 相似文献
76.
Jorge A. Soria-Alcaraz Gabriela Ochoa Jerry Swan Martin Carpio Hector Puga Edmund K. Burke 《European Journal of Operational Research》2014
Course timetabling is an important and recurring administrative activity in most educational institutions. This article combines a general modeling methodology with effective learning hyper-heuristics to solve this problem. The proposed hyper-heuristics are based on an iterated local search procedure that autonomously combines a set of move operators. Two types of learning for operator selection are contrasted: a static (offline) approach, with a clear distinction between training and execution phases; and a dynamic approach that learns on the fly. The resulting algorithms are tested over the set of real-world instances collected by the first and second International Timetabling competitions. The dynamic scheme statistically outperforms the static counterpart, and produces competitive results when compared to the state-of-the-art, even producing a new best-known solution. Importantly, our study illustrates that algorithms with increased autonomy and generality can outperform human designed problem-specific algorithms. 相似文献
77.
Aleksandra Swiercz Edmund K. Burke Mateusz Cichenski Grzegorz Pawlak Sanja Petrovic Tomasz Zurkowski Jacek Blazewicz 《Central European Journal of Operations Research》2014,22(3):567-589
This paper introduces a new approach to applying hyper-heuristic algorithms to solve combinatorial problems with less effort, taking into account the modelling and algorithm construction process. We propose a unified encoding of a solution and a set of low level heuristics which are domain-independent and which change the solution itself. This approach enables us to address NP-hard problems and generate good approximate solutions in a reasonable time without a large amount of additional work required to tailor search methodologies for the problem in hand. In particular, we focused on solving DNA sequencing by hybrydization with errors, which is known to be strongly NP-hard. The approach was extensively tested by solving multiple instances of well-known combinatorial problems and compared with results generated by meta heuristics that have been tailored for specific problem domains. 相似文献
78.
This paper concerns smoothing by infimal convolution for two large classes of functions: convex, proper and lower semicontinous as well as for (the nonconvex class of) convex-composite functions. The smooth approximations are constructed so that they epi-converge (to the underlying nonsmooth function) and fulfill a desirable property with respect to graph convergence of the gradient mappings to the subdifferential of the original function under reasonable assumptions. The close connection between epi-convergence of the smoothing functions and coercivity properties of the smoothing kernel is established. 相似文献
79.
Anthony J. Burke Elisabete da Palma Carreiro Nuno M.M. Moura Ana Isabel Rodrigues 《Journal of organometallic chemistry》2007,692(22):4863-4874
In our quest to find new ligands for highly stereoselective reactions, we tested a variety of chiral non-racemic pseudo-C2 symmetric bis-oxazolines derived from malonic acid containing an arylidene bridge unit (and appropriately termed Arylid-Box) in the catalytic asymmetric cyclopropanation (CAP) reaction of styrene and ethyl diazoacetate using between only 1-2 mol% of a Cu(I) pre-catalyst. Some very good e.e.s (up to 86%), were obtained. It was possible to isolate 10a′-[Cu(CH3CN)4]PF6 which existed as a bench stable solid that proved to be more efficient than the catalyst prepared in situ. Cu(I) pre-catalysts were used for the first time in the CAP reaction with the Isbut-Box ligands 13a and 13b and, although, the e.e.s were better for ligand 13a using these pre-catalysts, in the case of ligand 11b this was not the case. Spectroscopic studies (UV-Vis and 1H NMR) were carried out to gain an insight into the nature of the catalytic species at work so that the conditions could be optimised giving better results. Some theoretical studies were conducted to try to explain the better enantioselectivities obtained using Evans’ tert-Box-Cu(I) complex over our complex. 相似文献
80.
The underlying metal was observed to corrode when a ruthenium dioxide-coated titanium electrode was anodized in an aqueous methanol solution. With a similarly coated platinum electrode peaks were observed on the voltammogram below 1.0 V which were attributed to methanol oxidation on the underlying metal. This effect was more pronounced when the electrode was subjected during cycling to potentials close to 0 V. Rapid oxidation of methanol on RuO2 was observed at potentials above 1.0 V, the rate at a given potential increasing in an approximately linear manner with increasing alcohol concentration. The rate of reaction also increased with increasing temperature and increasing surface roughness. Tafel slope values were rather high (>100 mV decade?1) and a mechanism involving anodically generated species such as OHads was proposed to account for these results. The variation of activity with pH was similar to that reported earlier for oxygen evolution at these anodes and this was again explained in terms of partial deactivation of the surface due to a combination of proton loss and phosphate ion adsorption at intermediate pH values. The release of carbon dioxide from aqueous solutions of higher alcohols at 25°C confirmed the high oxidizing power of RuO2 anodes. 相似文献