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541.
This paper constitutes an experimental and numerical study, using uncertainty analysis of the most important parameters, to evaluate the mechanism for the combustion of CO + H2 mixtures at high pressures in the range 15-50 bar and temperatures from 950 to 1100 K. Experiments were performed in a rapid compression machine. Autoignition delays were measured for stoichiometric compositions of CO + H2 containing between 0 and 80% CO in the total fuel mixture. The experimental results showed an unequivocal monotonic increase as the proportion of CO in the mixture was raised. Comparisons were made also with the measured ignition delays in mixtures of H2 with increasing dilution by N2, corresponding to the proportions of CO present. These times also increased monotonically, albeit with a greater sensitivity to the extent of dilution than those measured in the CO + H2 mixtures. By contrast, numerical simulations for the same mixtures, based on a kinetic model derived by Davis et al. displayed a qualitative discrepancy as there was virtually no sensitivity of the ignition delay to the changing ratio of CO + H2, certainly up to 80% replacement. No exceptions to this trend were found, despite tests being made using seven other kinetic models for CO + H2 combustion. Global uncertainty analyses were then applied to the Davis et al. model in order to trace the origins of this discrepancy. The analyses took into account the uncertainties in all rate parameters in the model, which is a pre-requisite for evaluation against ignition delay data. It is shown that the reaction rate constant recommended by Baulch et al. for the HO2 + CO reaction, at T ∼ 1000 K, could be up to a factor of 10 too high and that lowering this rate corrected the qualitative anomaly between experiment and numerical prediction. 相似文献
542.
The study of microorganisms at the aqueous/metal interface is of great interest as their presence is often associated with surface deterioration or corrosion. Surfaces submerged in aquatic environments rapidly become fouled with organic macromolecules, such as proteins and/or glycoproteins. Bacteria adhering to this conditioning film typically produce extracellular polysaccharides that anchor the cells to the substrate. In a previous paper, the kinetics of polysaccharide adsorption and desorption on protein conditioning films formed on bare germanium internal reflection elements (IREs) were investigated in an effort to gain a better understanding of the fouling process. This work has been extended to the study of adsorption phenomena at an aqueous/copper interface. Alginic acid and dextran were exposed to protein-conditioned and untreated copper films. In the absence of a protein biofilm, greater erosion of the Cu film was observed with flowing saline than with a solution of alginic acid in saline, and more Cu was removed at pH 4.8 than at pH 7.0. The neutral polysaccharide was less corrosive than alginic acid. The presence of a film of bovine serum albumin (13.5 nm) conditioning film did not shield the Cu film from the corrosive effects of either polysaccharide. In all experiments, as Cu slowly eroded from the surface of the IRE, metal islands formed leading to the observation of surface-enhanced infrared absorption (SEIRA). The intensity of the C-O stretching band of adsorbed dextran on Cu islands was over an order of magnitude greater than would be observed with a uniform Cu film of the same thickness. Enhancement of the amide II band of BSA was also observed. In general, the effect of SEIRA complicated spectral processing and interpretation and thus interfered with the determination of surface coverage and polysaccharide adsorption/desorption kinetics on protein conditioning films. Copyright 1999 Academic Press. 相似文献
543.
544.
Kataoka M Fletcher JD See P Giblin SP Janssen TJ Griffiths JP Jones GA Farrer I Ritchie DA 《Physical review letters》2011,106(12):126801
We report the observation of nonadiabatic excitations of single electrons in a quantum dot. Using a tunable-barrier single-electron pump, we have developed a way of reading out the excitation spectrum and level population of the dot by using the pump current as a probe. When the potential well is deformed at subnanosecond time scales, electrons are excited to higher levels. In the presence of a perpendicular magnetic field, the excited states follow a Fock-Darwin spectrum. Our experiments provide a simple model system to study nonadiabatic processes of quantum particles. 相似文献
545.
Robert B. Griffiths 《Foundations of Physics》2011,41(4):705-733
It is argued that while quantum mechanics contains nonlocal or entangled states, the instantaneous or nonlocal influences
sometimes thought to be present due to violations of Bell inequalities in fact arise from mistaken attempts to apply classical
concepts and introduce probabilities in a manner inconsistent with the Hilbert space structure of standard quantum mechanics.
Instead, Einstein locality is a valid quantum principle: objective properties of individual quantum systems do not change
when something is done to another noninteracting system. There is no reason to suspect any conflict between quantum theory
and special relativity. 相似文献
546.
Julian C. Caesar D. Vaughan Griffiths John C. Tebby 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-4):123-127
Abstract The reaction of dialkyl phosphonites with dimethyl acetylenedicarboxylate proceeds via an analogous route to that previously established for the reaction of trialkyl phosphites although the intermediates are less stable. The five-coordinate phosphole (3; R = Et, R' = Ph) is sufficiently stable at -70°C to enable it to be converted to the oxo-phosphole (5; R' = Ph) by treatment with anhydrous hydrogen bromide. 相似文献
547.
D. Vaughan Griffiths Jayne E. Harris 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract We have previously shown that substituted bcnzoylphosphonates (1; Ar ? X-Ph) react with trimethyl phosphite to give anionic intermediates which in the absence of electrophiles decompose to give carbene intermediates (3). The nature of the subsequent reaction products depends on the type and position of the substituents on the aromatic ring.ll1 When proton donors are present the initially formed anionic intermediates (2) give the quasi-phosphonium salts (4) which usually decompose to give the phohphonate-phosphates (5). although for the case of (1; Ar ? 4-MeOPh) formation of the phosphonates (6) was observed. 相似文献
548.
D. Vaughan Griffiths Khalku Karim 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Dimethyl benzoylphosphonates (1) react with trimethyl phosphite to give anionic intermediates (2) which decompose to give carbenes (3) and trimethyl phosphate [1]. When suitable ortho-substituents are present on the benzoylphosphonate, intramolecular carbene insertion reactions can occur to give cyclic systems. With alkyl substitutents, where the length of the chain provides a choice of cyclisation pathways, insertion into an appropriate C[sbnd]H bond to give a 5-membered ring has been found to be the preferred option. We have therefore been investigating the behaviour of systems, such as (4), where insertion into a C[sbnd]H bond to give a 5-membered ring is prevented. 相似文献
549.
Dana K. Adkinson David C. Magri Jason L. Pitters Keith Griffiths Peter R. Norton Mark S. Workentin 《Photochemistry and photobiology》2013,89(5):1020-1028
The photochemical and thermal reactivity of a number of acyl azide‐substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single‐crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection‐absorption infrared spectroscopy by observation of C=O and N3 bands at 1700 cm?1, and 2100 and 1300 cm?1 respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm?1 with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles. 相似文献
550.
Patrick J. HeaphyJustin R. Griffiths Christopher J. DietzG. Paul Savage Ronny Priefer 《Tetrahedron letters》2011,52(48):6359-6362
Cubane is a highly strained unsaturated molecule that was first synthesized in 1964 by Philip E. Eaton. Since cubane’s discovery, it has been researched in pharmaceuticals, explosives, and polymers. Due to its range of uses, we have explored the thermo-stability of a number of cubane derivatives. Some derivatives have revealed its propensity to undergo cage opening/rearrangement. In examining 1-iodocubane-4-carboxaldehyde, we observed that benzoic acid, benzaldehyde, benzyl alcohol, and benzyl benzoate were surprisingly formed in this thermo-decay. 相似文献