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131.
Magdy A. Ezzat Noorah S. AlSowayan Zeid I. A. Al-Muhiameed Shereen M. Ezzat 《Heat and Mass Transfer》2014,50(7):907-914
A new mathematical model for Pennes’ bioheat equation using the methodology of fractional calculus was constructed. The thermal behavior in living tissue subjected to instantaneous surface heating was investigated. Numerical calculations were performed to study the temperature transients in the skin exposed to instantaneous surface heating. Some comparisons were shown in figures to estimate the effect the fractional order parameter α on the thermal wave. In this novel theory, the fractional parameter α is an indicator of bioheat efficiency in living tissues. 相似文献
132.
Hard coatings are used in a very broad range of applications, for example in the automotive, tooling and gas industries. The apparently simplest way to compare different coatings is to measure their hardness. However, interpreting such measurements is not a trivial problem for thin coatings (10 μm or less); standard micro-indenters (with a typical minimum applied load of 10gf) usually produce a penetration depth such that the substrate influences the measurements, giving a ‘composite’ hardness value of the coating and the substrate. At the same time there might be a more or less evident recovery of the indentation, because of residual elasticity around the sub-indentation plastic zone or because of residual stresses. One possible solution is the use of a nano-indenter. An alternative method for obtaining ‘true’ Vickers hardness values for the coating is described here, using changes in shape of Knoop micro-indentations to characterize the elastic recovery effects, together with use of a composite model for thin film microhardness. Results of hardness testing on thin WC-based coatings, using nano-indentation, Vickers and Knoop indenters, are compared. 相似文献
133.
Embedded-atom method potentials and atomistic models of coherent (010) interfaces were used to study slip across interfaces in cube-on-cube oriented Cu/Ni nanolayered materials. (111) disconnections form during slip across Cu–Ni interfaces and become significant barriers to continued deformation. A significant barrier exists for the flat coherent interface owing to the large coherency stresses in the Cu/Ni layers that must be overcome by applied stresses but, once these have been overcome, interface transection occurs readily. A disconnection adds an additional barrier because of a residual dislocation with a Burgers vector magnitude equal to the difference between b Cu and b Ni. This barrier depends on the position of the disconnection relative to the glide plane of the transecting glide dislocation and on the disconnection height. Disconnections cause work hardening that prevents shear band formation during deformation and encourages homogeneous shear processes. Disconnection energies are shown to be relatively small and to depend on the disconnection type and size. 相似文献
134.
Roll-bonded diffusion couples are used to investigate a transformation of intermetallic particles from Al6(Fe,?Mn) to α-Al–(Fe,?Mn)–Si that occurs upon homogenization of 3XXX aluminium alloys. By diffusing silicon into an Al–Fe–Mn alloy, the couples permit a progressive increase in the driving force for this 6-to-α transformation, thus allowing study of the nucleation of the transformation. Initially, the aluminium matrix is highly defected from rolling. This microstructure gives frequent (yet stochastic) nucleation of a eutectoid 6-to-α transformation expected from study of direct-chill-cast 3XXX alloys. However, once the matrix has recrystallized, nucleation is restricted to particles that lie on the matrix grain boundaries. The remaining particles, unable to transform eutectoidally, dissolve and supply growth of these α-phase particles, producing marked coarsening. 相似文献
135.
The sputtering behaviour of hexagonal or wurtzite polycrystal nitrides of boron, aluminium, and gallium was explored employing methods of molecular dynamics. The sputtering yield Y of nitrides and the average energy ē 1 of emitted particles were studied as dependent on the mass m 1 of bombarding He, Li, B, N, Ne, Al, Ar, Ni, Ga, Kr, and Xe ions with the initial energy E 0 between 200 and 10,000 eV. Y(m 1) and ē 1(m 1) were researched upon for preferential sputtering of nitride components at low E 0. It was revealed that the ratio between the sputtering yield of the light component and that of the heavy one depends on ion energy and mass. At E 0=200 eV and m 1=40, the ratio for BN, AlN, and GaN amounts to 1.2, 2.2, and 2.4, respectively. For nitride components, an anomalous dependence of sputtering on ion mass was found, its maximum occurring at a certain ratio m 2/m 1, where m 2 is the averagè mass of two nitride components. 相似文献
136.
Blend hydrogels composed of carboxymethyl chitosan (CMCh) and poly (acrylonitrile) (PAN) were synthesized via crosslinking
method. Several analyses were made to investigate both physical and thermal properties of CMCh/PAN hydrogels like; FTIR, scanning
electron microscope, XRD and thermogravimetric analysis (TGA). TGA results showed that CMCh/PAN hydrogels are thermally more
stable than CMCh and their thermal stability increases as PAN content increases in the hydrogel. Moreover, the swelling behavior
of CMCh/PAN hydrogels was studied in different buffer solutions. It was found that CMCh/PAN hydrogels swell much more than
PAN especially at pH 9. The hydrogels sorption for different dyestuff and various metal ions like; Cu2+, Cd2+ and Co2+ were also studied. In this work, antibacterial characteristic of hydrogels was mainly investigated towards Escherichia coli (E. coli) as a serious disease-leading bacterium. All tested hydrogels have clearly presented good antibacterial activity as CMCh
content increases in the hydrogels. 相似文献
137.
Magdy W. Sabaa Samira T. Rabie Riham R. Mohamed 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1503-1513
Pyrazolodithiones of expected biological activity were examined as thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride) (PVC) in air at 180?°C. Their high stabilizing efficiency were shown by their high thermal stability values (T s), which is the time needed for the liberation of HCl gas, if compared with dibasic lead carbonate (DBLC) and calcium?Czinc soap (Ca?CZn soap) reference stabilizers used industrially, with better extent of discoloration. Blending these derivatives with reference stabilizers in different ratios greatly lengthens the thermal stability value and improves the extent of discoloration of the PVC. The structure of the novel organic stabilizers was confirmed by elemental analysis, FTIR, Mass spectra, and 1H-NMR. Thermogravimetric analyses confirmed the improved stability of PVC in the presence of the investigated organic stabilizers, compared to blank PVC and PVC stabilized with the reference stabilizers. Also, GPC measurements were done to investigate the changes occurred in the molecular masses of the degraded samples of PVC in presence of the newly synthesized stabilizers. The stabilizing efficiency of pyrazolodithiones is attributed to the replacement of the labile chlorine atoms on the PVC chains by a relatively more stable moiety of the organic stabilizer. The investigated stabilizers showed a good antimicrobial activity toward two kinds of bacteria, Escherichia coli and Staphylococcus aureus; and also toward two kinds of fungi, Aspergillus flavus and Candida albicans. They also exhibited antitumor activity against both liver and colon human cell lines. 相似文献
138.
Thin (100–150 Å thick) single crystals of large lateral dimensions have been grown from dilute solution in xylene of random terpolymer, thermotropic, liquid crystal polymers containing approximately equimolar amounts of C6 or C7 flexible segments, oxybenzoate, and dioxyphenyl. With both polymers having molecular lengths of 800 Å or longer, electron diffraction patterns indicate chain folding. The crystal structure, hexagonal, is less perfect than found previously for thin films of the C7 (and C5) polymer crystallized from the nematic state by slow cooling (orthorhombic). Annealing of the crystals below the crystal-liquid crystal transition results in merging of overgrowths and rough crystal edges into the main crystal and a surface roughening, followed, at longer times and/or higher temperatures, by lamella thickening. Annealing in the nematic state results in the development of rosettes of lamellae. Implications of the results for crystallization mechanisms and morphology of the nematic state are discussed. 相似文献
139.
A. Anguiano-García A. Cruz H. Luna-García E. Poulain S. Castillo † 《Molecular physics》2013,111(5):447-460
The study of the interaction of a pyramidal tetramer of Cu2Pt2 with the H2 is reported here through ab initio multiconfigurational self-consistent field (MC-SCF) calculations, plus extensive multireference configuration interaction (MR-CI), variational and perturbative calculations. The lowest three electronic states X 1A′, a 3A′ and a 1A′ of the bare cluster were considered in order to study this interaction. For the H2 Cs approaching a Pt vertex, results show that the Cu2Pt2 pyramid cluster in its X 1A′ and a 1A′ states can spontaneously capture and dissociate the H2. For the H2 Cs approaching a Cu vertex, where H2 is located in the Cs reflecting plane, the Cu2Pt2 cluster in its X 1A′ electronic state shows capture of the hydrogen molecule after surmounting an energy barrier; moreover, in this approach the Cu2Pt2 cluster in its a 1A′ electronic state shows spontaneous capture of the hydrogen molecule. For the H2 approaching a Cu vertex, where the Cs reflecting plane bisects the H2 molecule, the Cu2Pt2 cluster in its three lowest-lying states is able to capture the hydrogen molecule after surmounting a small barrier. The Cu2Pt2+H2 Cs face-on interactions show a lower H2 activation than that which was obtained in the equivalent Pt4+H2 interactions. 相似文献
140.
Phosphorus doped hydrogenated amorphous silicon (a-Si:H) films were prepared by decomposition of silane using RF plasma glow discharge. Both DC dark conductivity measurements, and spectrophotometric optical measurements through the range 200–3000 nm were recorded for the prepared films. The DC conductivity activation energy Ea decreased from 0.8 eV for the undoped sample to 0.34 eV for the highest used doping value. The optical energy gap Eg decreased ranging from 1.66 eV to 1.60 eV. The refractive index n, the density of charge carriers N/m* and the plasma frequency ωp showed an opposite behavior, i.e. an increase in value with doping. Fitting the dispersion values to Sellmeier equation led to the determination of the material natural frequency of oscillating particles. A correlation between the changes in these parameters with the doping has been attempted. 相似文献