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排序方式: 共有169条查询结果,搜索用时 15 毫秒
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L. Tamašauskaitė-Tamašiūnaitė A. RadomskisK. Antanavičiūtė J. JablonskienėA. Balčiūnaitė A. ŽielienėL. Naruškevičius R. KondrotasE. Norkus 《International Journal of Hydrogen Energy》2014
In the study presented herein a rapid microwave heating method was used to prepare the graphene supported PtCo catalysts with Pt:Co molar ratio 1:7, 1:22 and 1:44. The transmission electron microscopy was employed to characterize the catalysts. Inductively coupled plasma optical emission spectrometry was used for estimation of Pt and Co metal loadings. The electrocatalytic activity of the synthesized catalysts towards the oxidation of borohydride was investigated by means of cyclic voltammetry and chronoamperometry. The kinetics of the catalytic hydrolysis of NaBH4 in the presence of the synthesized catalysts was investigated. 相似文献
53.
V. Ambrazevičienė R. Brazis A. Kunigėlis 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(4):373-380
The second harmonic radiation in millimeter wave region is found in semiconductors in the absence of the dc electric field. The observed resonant maximum of radiation intensity is shown to be related to the excitation of the free-electron plasma oscillations in the dc magnetic field. 相似文献
54.
Mortality of silver eels migrating through different types of hydropower turbines in Lithuania
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Hydropower plants (HPP) are considered to be one of the major threats to the survival of European eels when they migrate downstream along inland water bodies during the early part of their annual journey to the spawning area in the Sargasso Sea. There are 98 HPPs in Lithuania and thousands throughout Europe. Numerous studies describe HPP induced mortality rates among European eels as variable depending on local, environmental, and technical factors. This heterogeneity in effect complicates theoretical extrapolation to eel mortality arising from specific types of HPP, necessary for effective management of local stocks. Silver eel mortality was estimated for 4 different HPPs in Lithuania. Mortality was estimated using RFID (Radio Frequency Identification, passive integrated transponders) tags and acoustic telemetry in a large HPP (>100 MW) with Kaplan turbines, a small HPP (<1 MW) with a Kaplan turbine and a fish passage, and for the first time in two small HPPs (<1 MW) with CINK turbines. The results supported a hypothesis that the mortality rate of migrating eels depends mainly on the type and size of the turbine. HPP induced mortality varied from 100% in a small CINK turbine down to 25% in the large HPP with Kaplan turbines. The importance of simple mitigation measures was highlighted by 34% of all tagged eels bypassing one of the HPP via an adjacent fish passage constructed for upstream migration of salmonids. The observed differences in mortality provide essential information for long term strategies designed to restore depleted eel populations in Lithuania and other European countries. 相似文献
55.
Pure Cu and Cu(Fe) thin films containing 0.1 and 1.0 at % Fe were prepared by low-temperature deposition onto a liquid-helium-cooled substrate. The Cu(Fe) films were annealed sequentially at approximately 17, 70, and 270 K. After each annealing stage the resistivity was measured down to 1.5K. The Cu(Fe) films exhibited a region in which the resistivity was proportional to ln T; in this region the logarithmic slope of the resistivity curve was only weakly affected by annealing. Below 10 K annealing produced a significant decrease in the impurity (Fe) contribution to the resistivity. The results are interpreted as due to increased interactions between Fe atoms produced by an increase in conduction-electron mean free path.This work was supported by the Materials Research Center, University of North Carolina, under Grant Number GH-33632 from the National Science Foundation. 相似文献
56.
A heterostructure consisting of a graded-gap p-AlxGa1?xAs layer on an n-GaAs substrate is studied in relation to its role as a photoelectric-response detector of X-ray photons and α particles. It is found that the current-power sensitivity of the detector is as high as 0.13 A/W and the voltage-power sensitivity exceeds 106 V/W. The effect of preliminary irradiation with 5.48-MeV α particles (241Am) on the detector’s sensitivity is studied. It is established that the detector’s sensitivity is reduced by a factor of 1.5–2 after irradiation with α particles at a dose of 5 × 109 cm?2. A further increase in the radiation dose to 4 × 1010 cm?2 does not affect the detector’s sensitivity. 相似文献
57.
D. Kaušpėdienė A. Gefenienė R. Ragauskas V. Pakštas 《Chemical Engineering Communications》2017,204(11):1258-1269
Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO3 were used for the removal of CN– and Ag–CN complex from model wastewater. The formed Ag0 centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag0 participating in CN– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The KF values for the CN– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN–, and plain, removing the rest of Ag–CN. 相似文献
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Elena Jasiūnienė Vaidotas Cicėnas Paulius Grigaliūnas Žymantas Rudžionis Arūnas Aleksandras Navickas 《Materials and Structures》2018,51(4):103
The interest in potential applications produced with self-compacting fibre reinforced concrete continues to grow, but in practice, problems associated with an uneven distribution and orientation of fibres in the concrete structure occur. It is not clear what exactly influences uneven distribution of fibres in self-compacting concrete (SCC) mixtures, especially during the casting and how different factors influence fibre orientation. The objective of this work was to investigate how rheological properties influence the steel fibre distribution in self-compacting concrete. This work also focuses on the investigation of steel fibre spatial orientation dependence on rheological properties of SCC, while keeping other casting parameters and the proportions of mixture components constant. Mixtures with three different rheological properties were chosen based on slump flow, slump flow time t500 and static segregation values. The steel fibre orientation, volumetric concentration and spatial distribution values were determined in separate beam sections using three different non-destructive testing methods: electromagnetic induction, image analysis and computed tomography (CT scan). The comparison of the results is presented. The results show how different rheological properties of SCC affect the steel fibre orientation and distribution for the case of beams produced with the flow-induced casting method. 相似文献