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排序方式: 共有1425条查询结果,搜索用时 9 毫秒
121.
Henrik Wiinikka Fredrik Weiland Esbjörn Pettersson Olov Öhrman Per Carlsson Jesper Stjernberg 《Combustion and Flame》2014
In this paper submicron particles sampled after the quench during 200 kW, 2 bar(a) pressurised, oxygen blown gasification of three biomass fuels, pure stem wood of pine and spruce, bark from spruce and a bark mixture, have been characterised with respect to particle size distribution with a low pressure cascade impactor. The particles were also characterised for morphology and elemental composition by a combination of scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and high resolution transmission electron microscopy/energy dispersive spectroscopy/selected area electron diffraction pattern (HRTEM/EDS/SAED) techniques. The resulting particle concentration in the syngas after the quench varied between 46 and 289 mg/Nm3 consisting of both carbon and easily volatile ash forming element significantly depending on the fuel ash content. Several different types of particles could be identified from classic soot particles to pure metallic zinc particles depending on the individual particle relation of carbon and ash forming elements. The results also indicate that ash forming elements and especially zinc interacts in the soot formation process creating a particle with shape and microstructure significantly different from a classical soot particle. 相似文献
122.
An ultra-high pressure jet of water and air with simultaneous cement grouting is revolutionishing the practice of ground consolidation and foundation reinforcement. Swedish research has been studying this development, briefly explained here. The note report is based on a summary note issued by the Swedish Council for Building Research. 相似文献
123.
A probabilistic fracture mechanics method is presented and applied to glulam beams with holes. The method is based on a combination of Weibull weakest link theory and a mean stress method which is a generalization of linear elastic fracture mechanics. Combining these two methods means that the global strength will be governed by both fracture energy and material strength and also that the stochastic nature of the material properties are taken into account. The probabilistic fracture mechanics method is evaluated by comparison to experimental test results. The method shows good ability to predict strength, with the exception of very small beams where the capacity is overestimated. The comparison to experimental tests deals also with other methods for strength analysis including code design methods. 相似文献
124.
There is increasing demand to optimise yield and increase capacity of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and resent research has shown that the economic aspects of production have great influence on the optimisation results. The profitability of a product is influenced by several parameters, and control of all these parameters is necessary to use some sort of optimisation software.In this paper, we present a case study of a typical crushing plant, with the goal of reducing the number of crusher while keeping the plant capacity and quality. By reducing the number of crusher the plant will need less maintenance which will decrease the operating costs. The article presents a method to combine crushing plant simulation and optimisation with quality and economic considerations in order to successfully study alternative configurations of the plant. 相似文献
125.
Per Martin Rørvik Kiyoharu Tadanaga Masahiro Tatsumisago Tor Grande Mari-Ann Einarsrud 《Journal of the European Ceramic Society》2009,29(12):2575-2579
Nanotubes of ferroelectric lead titanate (PbTiO3) have been made by a template-assisted method. An equimolar Pb–Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO3 perovskite nanotubes were obtained by annealing at 700 °C for 6 h. The nanotubes had diameters of 200–400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single-phase PbTiO3 nanotubes. The influence of the heating procedure and the sol concentration is discussed. 相似文献
126.
Andreas Mattsson Christian Lejon Vclav tengl Snejana Bakardjieva Frantiek Oplutil Per Ola Andersson Lars
sterlund 《Applied catalysis. B, Environmental》2009,92(3-4):401-410
The structure and photocatalytic activity of Zr doped TiO2 nanocrystallites with a varying Zr content between 0 and 15 wt% prepared by an efficient and environmentally benign method has been studied by vibrational spectroscopy, TEM and XRD. It is shown that the presence of Zr4+ ions stabilizes the anatase structure and delays phase transformation to rutile upon annealing as well as retarding grain coarsening. All TiO2 samples up to 13 wt% Zr doping concentration show better or similar photoreactivity compared to P25 (Degussa) for decomposition of adsorbed 2-chloroethyl ethyl sulphide (CEES) and dimethyl methylphosphonate (DMMP) in synthetic air at room temperature. The most efficient sample for photodegradation of both CEES and DMMP is shown to be titania doped with 6.8 wt% Zr. The photodegradation of CEES is faster than DMMP under the same experimental conditions. On the undoped TiO2 sample urea residues are detected spectroscopically. Much less is detected on the Zr doped samples. Mode resolved in situ FTIR surface spectroscopy enables distinction of CEES or DMMP, decomposition products as well as the influence of residues from the particle synthesis. This facilitates extraction of intra-comparable reaction rates. Possible explanations for the improved reactivity of the Zr doped titania are discussed. 相似文献
127.
Transitional Thermal Creep of Early Age Concrete 总被引:1,自引:0,他引:1
Anders Boe Hauggaard Lars Damkilde Per Freiesleben Hansen 《Canadian Metallurgical Quarterly》1999,125(4):458-465
Couplings between creep of hardened concrete and temperature∕water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete that includes the transitional thermal effect. The model governs both early age concrete and hardened concrete. The development of the material properties in the model is assumed to depend on the hydration process and the thermal activation of water in the microstructure. The thermal activation is assumed to be governed by the Arrhenius principle, and the activation energy of the viscosity of water is found applicable in the analysis of the experimental data. Changes in temperature create an imbalance in the microstructure termed the microprestresses, which reduce the stiffness of the concrete and increase the creep rate. The aging material is modeled in an incremental way reflecting the hydration process in which new layers of cement gel solidify in a stress free state and add stiffness to the material. Analysis of experimental results for creep of early age and hardened concrete either at different constant temperature levels or for varying temperature histories illustrate the model. 相似文献
128.
利益相关者在不断呼吁改进公共事业单位和发展组织的响应能力,实现以绩效为导向、增加公共事业单位和发展组织的相关性;受其影响,许多公共事业单位和发展组织都开始努力改进其办事效力和效率.这种转变集中表现在对成果管理的关注以及对提高国家层面、机构层面和合作单位层面的发展力度的坚实承诺.本文旨在探讨成果管理的发展背景并阐述成果管理方法的一些核心概念. 相似文献
129.
130.