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91.
The planar laser-induced fluorescence (PLIF) imaging method was used to perform flow visualization and quantitative planar
thermometry in shock tube flow fields using toluene as a fluorescence tracer in nitrogen. Fluorescence quantum yield values
needed to quantify PLIF images were measured in a static cell at low pressures (<1 bar) for various toluene partial pressures
in nitrogen bath gas. Images behind incident and reflected shocks were taken in the core flow away from regions affected by
boundary layers. Temperature measurements from these images were successfully compared with predicted values using ideal shock
equations. Measured temperatures ranged between 296 and 800 K and pressures between 0.15 and 1.5 atm. The average temperature
discrepancies between measurements and the predicted values behind the incident and reflected shocks were 1.6 and 3.6%, respectively.
Statistical analyses were also conducted to calculate the temperature measurement uncertainty as a function of image resolution.
The technique was also applied to the study of more complex supersonic flows, specifically the interaction of a moving shock
with a wedge. Measured temperatures agreed well with the results of numerical simulations in all inviscid regions, and all
pertinent features of the single Mach reflection were resolved. 相似文献
92.
An IR laser absorption diagnostic has been further developed for accurate and sensitive time‐resolved measurements of ethylene in shock tube kinetic experiments. The diagnostic utilizes the P14 line of a tunable CO2 gas laser at 10.532 μm (the (0 0 1) → (1 0 0) vibrational band) and achieves improved signal‐to‐noise ratio by using IR photovoltaic detectors and accurate identification of the P14 line via an MIR wavemeter. Ethylene absorption cross sections were measured over 643–1959 K and 0.3–18.6 atm behind both incident and reflected shock waves, showing evident exponential decay with temperature. Very weak pressure dependence was observed over the pressure range of 1.2–18.6 atm. By measuring ethylene decomposition time histories at high‐temperature conditions (1519–1895 K, 2.0–2.8 atm) behind reflected shocks, the rate coefficient of the dominant elementary reaction C2H4 + M → C2H2 + H2 + M was determined to be k1 = (2.6 ± 0.5) × 1016exp(?34,130/T, K) cm3 mol?1 s?1 with low data scatter. Ethylene concentration time histories were also measured during the oxidation of 0.5% C2H4/O2/Ar mixtures varying in equivalence ratio from 0.25 to 2. Initial reflected shock conditions ranged from 1267 to 1440 K and 2.95 to 3.45 atm. The measured time histories were compared to the modeled predictions of four ethylene oxidation mechanisms, showing excellent agreement with the Ranzi et al. mechanism (updated in 2011). This diagnostic scheme provides a promising tool for the study and validation of detailed hydrocarbon pyrolysis and oxidation mechanisms of fuel surrogates and realistic fuels. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 423–432, 2012 相似文献
93.
We have studied the structure and shear flow behaviour of a side chain liquid crystal polymer, namely P12, in the smectic (SmAd) phase. Simultaneous oscillatory shear and small angle X-ray scattering experiments showed that, as expected, the shearing of P12 at high frequency and large strain amplitudes leads to the alignment of the smectic layer normals parallel to the neutral direction. It was also found that, on erasing the memory of the prior shear alignment through melting, P12 can unexpectedly orient with the smectic layers perpendicular to the shear flow direction (b-configuration). We speculate that the b-configuration is adopted due to a counter-balance between the rather long spacer in P12 which decouples mesogens from the backbone, and the oscillatory character of the shear applied to P12. 相似文献
94.
95.
In this note, we classify completely distributive CSLs up to approximate unitary equivalence. Our proof uses a new characterization of complete distributivity and leads to a generalization of a result of Arveson on ordered group lattices. As consequences of our results, we obtain a similarity theorem for hyperreflexive, completely distributive CSLs and some new perturbation results.Partially supported by an NSERC grantResearch partially supported by NSF grant DMS-9204811. 相似文献
96.
Davidson Sacha Bailey David Campbell Bruce A. 《Zeitschrift fur Physik C Particles and Fields》1994,61(4):613-643
We present model independent constraints on the masses and couplings to fermions ofB andL conserving leptoquarks. Such vector or scalar particles could have masses below 100 GeV and be produced at HERA; we list the generation dependent bounds that can be calculated from rare lepton and meson decays, meson-anti-meson mixing and various electroweak tests. 相似文献
97.
A parametric study of droplet deformation through a microfluidic contraction: Shear thinning liquids
D.J.E. Harvie M.R. Davidson J.J. Cooper-White M. Rudman 《International Journal of Multiphase Flow》2007
Numerical simulations of a droplet passing through an axisymmetric microfluidic contraction are presented, focusing on systems where one of the two liquids present is shear thinning. The simulations are performed using a transient Volume of Fluid (VOF) algorithm. When the droplet is shear thinning and the surrounding phase Newtonian, droplets deform in a similar way to Newtonian droplets that have a viscosity equal to the average viscosity of the shear thinning fluid while it is within the contraction. When the surrounding phase is shear thinning and the droplet Newtonian, droplets deform in a similar way to droplets contained within a Newtonian liquid that has a viscosity that is lower than that of the droplet. In both cases the behaviour of the shear thinning fluid can be broadly described in terms of a ‘characteristic’ Newtonian viscosity: However, determining the exact value of this viscosity without performing a full shear thinning simulation is not possible. 相似文献
98.
In a previous paper by Davidson, Eisenstadt and Reiner, it was noted that, as the diameter ratio of an open-end, thick-walled cylinder approached unity, the stress state due to internal pressure approaches that of uniaxial tension. It was, therefore, proposed that the fatigue life of a cyclically pressurized thick-walled cylinder might be predicted from the results of axialtension fatigue tests. In this paper, the results of the thick-walled-cylinder fatigue tests, reported in Ref. 2, extrapolated to a diameter ratio of unity, are compared with the results of axial-tension fatigue tests on the same material. The effect of oil in contact with the surface of the axial fatigue specimens and that of varying the cyclic speed from 1800 cpm to 200 cpm are investigated. Rotating beam fatigue test results for the same material are also reported. The results of the axial-tension fatigue tests do not agree with the extrapolated thick-walled cylinder results in the range of fatigue lives from 104 to 106 cycles with the cylinder results showing the shorter lives. For less than 104 cycles, the results converge. No effect of cyclic speed or of oil in contact with the surface was found. The results of the rotating-beam tests generally lie between the axial-tension and extrapolated cylinder results. 相似文献
99.
Prof. Dr. Robin B. Bedford John G. Bowen Russell B. Davidson Dr. Mairi F. Haddow Annabelle E. Seymour‐Julen Dr. Hazel A. Sparkes Dr. Ruth L. Webster 《Angewandte Chemie (International ed. in English)》2015,54(22):6591-6594
Palladium(II) acetate is readily converted into [Pd3(μ2‐OH)(OAc)5] ( 1 ) in the presence of water in a range of organic solvents and is also slowly converted in the solid state. Complex 1 can also be formed in nominally anhydrous solvents. Similarly, the analogous alkoxide complexes [Pd3(μ2‐OR)(OAc)5] ( 3 ) are easily formed in solutions of palladium(II) acetate containing a range of alcohols. An examination of a representative Wacker‐type oxidation shows that the Pd‐OH complex 1 and a related Pd‐oxo complex 4 can be excluded as potential catalytic intermediates in the absence of exogenous water. 相似文献
100.
Vasu SS Huynh LK Davidson DF Hanson RK Golden DM 《The journal of physical chemistry. A》2011,115(12):2549-2556
Reactions of hydroxyl (OH) radicals with 1-butene (k(1)), trans-2-butene (k(2)), and cis-2-butene (k(3)) were studied behind reflected shock waves over the temperature range 880-1341 K and at pressures near 2.2 atm. OH radicals were produced by shock-heating tert-butyl hydroperoxide, (CH(3))(3)-CO-OH, and monitored by narrow-line width ring dye laser absorption of the well-characterized R(1)(5) line of the OH A-X (0, 0) band near 306.7 nm. OH time histories were modeled using a comprehensive C(5) oxidation mechanism, and rate constants for the reaction of OH with butene isomers were extracted by matching modeled and measured OH concentration time histories. We present the first high-temperature measurement of OH + cis-2-butene and extend the temperature range of the only previous high-temperature study for both 1-butene and trans-2-butene. With the potential energy surface calculated using CCSD(T)/6-311++G(d,p)//QCISD/6-31G(d), the rate constants and branching fractions for the H-abstraction channels of the reaction of OH with 1-butene were calculated in the temperature range 300-1500 K. Corrections for variational and tunneling effects as well as hindered-rotation treatments were included. The calculations are in good agreement with current and previous experimental data and with a recent theoretical study. 相似文献