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The influence of suspended fine particles of differing adsorbing capacity (activated carbon, avicell cellulose, SiO2, and molecular sieves) on the liquid-film mass transfer coefficient κL, was examined experimentally in a stirred cell of well-defined gas-liquid interfacial area by chemical methods. The greatest effect on κL was observed with the activated carbon (about a threefold increase). An addition of glycerine in excess of 2.5 × 10-3 k mol/m3, which was adsorbed on the particles preferentially, removed this increase in κL totally. Amongst other particles, only avicell cellulose showed measureable effects. The increase in κL values was inversely proportional to the temperature and the stirring speed, and the particle loading was found to be immaterial after a certain value. When the reaction rate increased (hence, when the thickness of dissolved gas-rich layer decreased) by gradual addition of a homogeneous catalyst (i.e. Co++ for sulphite oxidation), the effect of particles on κL decreased and eventually it disappeared. 相似文献
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Effect of operating parameters on color and COD removal performance of SBR: sludge age and initial dyestuff concentration 总被引:2,自引:0,他引:2
Effect of sludge and initial dyestuff concentration on color and COD removal performance of anaerobic-aerobic sequential batch reactor was investigated. Remazol Red RR a vinylsulphonyl (VS) and monochlortriazine (MCT), reactive azo dye was used in the study. Sludge age was varied between thetaC=12 days and thetaC=30 days and dyestuff concentration was between D0=50 and D0=500 mg l(-1). The maximum color and COD removal was obtained as 95% and 70% for D0=60 mg l(-1) and COD0=800 mg l(-1) at 15 days sludge retention time, respectively, and no further improvement was observed when sludge age was increased to 30 days. The main color removal phase in this operation system was the anaerobic phase. Because, the color removal efficiency was already above 95% under anaerobic condition and therefore, the contribution of aerobic phase to color removal was negligible. Increasing dyestuff concentration did not significantly affect the decolorization. It was possible to obtain over 90% dyestuff removal even at D0=500 mg l(-1). SBR system reduces 1000 mg l(-1) initial COD concentrations to about 400 mg l(-1) for dyestuff concentration up to 150 mg l(-1). COD removal efficiency decreased from 70% to 60% by increasing initial dyestuff concentration from 100 to 500 mg l(-1). The results indicated that dyestuff and COD are mainly used by anaerobic organisms and aeration does not improve the performance of SBR system. 相似文献
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Ideally, network bandwidth estimation algorithms should be independent of the end system performance. If end system capabilities are involved, then the measurement will be of the system throughput and will not indicate a correct assessment of network bandwidth. Packet dispersion‐based active bandwidth estimation schemes including Pathload, TOPP and pathChirp use delay correlation where the network‐induced delay on packets transmitted at certain rates is translated into bandwidth estimation. Since packet dispersion‐based active measurement schemes use delay correlation, bandwidth estimations are distorted by the host protocol stack‐induced delay variations. Studies revealed that the host protocol stack‐induced delay variations due to context switching are stovepiped in the network‐induced delay variations and impact the measurement process. This study explores the delay variations introduced by the host protocol stack in packet dispersion‐based techniques. The impact of host protocol delay variations and context switching on bandwidth estimation is analyzed and a new active bandwidth estimation tool minimizing the impact of context switching is proposed. Direct Injection Chirp (DIChirp) bypasses the TCP/IP protocol stack and directly interfaces with the network hardware. It uses the kernel for scheduling the outgoing packets, thus achieving more accurate estimation of bandwidth. Experiments revealed that the host protocol and context switching‐induced delay variations can be as high as 800µs and could result in bandwidth estimation errors near 20%. Experiments also revealed that the DIChirp is superior to the pathChirp implementation in performance estimation since the datapath utilized by DIChirp is less prone to delay variations induced by context switching. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Electrical insulation is a major security problem in aerospace applications where temperature can reach relatively low values. Epoxy resins are well known as easily formable dielectric materials and can be used to prepare complex insulator parts. In this study, the electrical performance of bisphenol A/epichlorohydrin epoxy resin matrix‐based nanocomposites containing 1, 3, or 6 wt% titanium oxide (TiO2) or aluminium oxide (Al2O3) nanofillers are investigated. Composites are characterized with thermogravimetric analysis, scanning electron microscopy‐coupled electron dispersive spectroscopy, and confocal Raman spectroscopy. Furthermore, the role of additives and their ratio on the resistivity performance of the composites are evaluated from 77 to 500 K by applying a direct current voltage from 1 to 20 V. It is observed that the electrical properties of the matrix are directly influencing the insulation performance of the nanocomposite. For example, the abrupt decrease at 370 K of the positive temperature coefficient of the resin for all nanocomposites. It is found that the most resistive composite contains 3 wt% TiO2 nanoparticles with a value above 3.7.1010 Ω from 77 to 370 K at 20 V. As a result, this work gives information on to the choice of appropriate insulator materials in extreme working conditions. 相似文献