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991.
992.
介绍气~液传质设备中浮阀复合塔板的应用情况,采用浮阀复合塔板可在尽可能不降低板效率的同时提高塔器的生产能力。 相似文献
993.
994.
晋城矿区赋有丰富的煤层气资源 ,为充分利用这部分煤层气资源 ,晋城无烟煤矿业集团利用美国的打钻、压裂、排采技术实施煤层气开发示范工程 ,经潘庄、寺河两矿煤层初步发电试验 ,取得成功 ,2 0 0 2年初运转的 1 1× 1 0 4kW发电示范工程 ,取得良好的经济效益 ,为后续煤层气资源利用积累了宝贵的经验。 相似文献
995.
F. Bergaya 《Journal of Porous Materials》1995,2(1):91-96
Pillared clays (PC) generally present textural complexity, geometrical constraints and possible chemical heterogeneity by pillaring. As far as surface area and porosity measurements by physical adsorption of nitrogen are concerned, this overall complexity introduces interpretation difficulties. We consider two aspects of this problem in pillared clays.The textural complexity stems from the distribution of charge density, from the deformation of the host layers and from their entanglement. The microtexture is controlled by the wet preparation chemistry, to a large extent by the drying method as examplified by the titanium pillared montmorillonites.The geometrical constraints arise from the fact that the interlamellar space of the PC is (so far) microporous or just mesoporous. The small distance between the layers, of the order of one or a few molecular diameters, is therefore expected to perturb the arrangement of the pore filling molecules. The molecular confinement is a major source of underestimation of the total pore volume in the interlamellar space. It makes the surface area determination difficult and of little physical significance. Probably microporosity values are more valuable criterion of pillaring as shown in the titanium pillared samples.In addition to these two aspects, one has also to consider a possible chemical heterogeneity arising from the simultaneous presence of pillars, exchangeable ions and precipitated species. This can lead to a complex behaviour of surface area and microporosity as examplified by the mixed aluminium-iron pillared laponites. 相似文献
996.
997.
为了改善纯ZrO_2气凝胶的高温稳定性,本研究以TEOS为硅源,以硝酸氧锆为锆源,通过滴加环氧丙烷,制备了ZrO_2-SiO_2复合气凝胶,探索了锆硅比例和热处理温度对复合气凝胶结构和性能的影响,结果表明,当锆硅比例为1:1时,制备的复合气凝胶比表面积最大,为551.7 m2/g;1000°C热处理后的比表面积为239.3 m2/g,1200°C热处理后的比表面积为89.5m2/g。与纯ZrO_2气凝胶相比,本研究所制得的ZrO_2-SiO_2复合气凝胶具有更好的热稳定性。 相似文献
998.
Three‐dimensional modeling of porosity development during the gasification of a char particle
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Kay Wittig Petr A. Nikrityuk Sebastian Schulze Andreas Richter 《American Institute of Chemical Engineers》2017,63(5):1638-1647
This work is devoted to the three‐dimensional, direct modeling of porosity and specific surface development during the gasification of a char particle. The model was developed for heterogeneous reactions occurring inside a char particle in a kinetically controlled regime. The main goal of this work is to analyze the impact of different pore size distributions on the particle carbon conversion rate. In particular, it is shown that under certain conditions the outer particle surface can influence the specific surface area. In this context the possible adaptation of the parameter ψ from the random pore model (RPM) developed by Bhatia and Perlmutter is explained. The results of simulations are compared against the RPM and discussed. Additionally, based on the results of simulations, the physics behind several input parameters used by the RPM are explored. Finally, the possible fragmentation of a chemically reacting char particle during its gasification in dependence of instantaneous porosity was investigated numerically. It was shown that the earliest fragmentation occurs at a carbon conversion of about 0.5–0.6 due to the disaggregation of the pore walls. The results are discussed and compared implicitly with data published in the literature. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1638–1647, 2017 相似文献
999.
《Ceramics International》2017,43(4):3797-3803
High surface area cobalt ferrite (CoFe2O4) powders were synthesized by solution combustion method. The dependence of the adiabatic temperature and the released gases during combustion reaction on the fuel content and cobalt precursor type, cobalt nitrate and cobalt acetate, was thermodynamically calculated. Thermal analysis, infrared spectroscopy, X-ray diffractometry, nitrogen adsorption–desorption, electron microscopy and vibrating sample magnetometer were used for investigation of the phase evolution, surface areas, morphology and magnetic properties of the synthesized CoFe2O4 powders. The specific surface area decreased from 285.4 to 35.7 m2/g with increasing of fuel to oxidant molar ratio, ϕ, from 0.5 to 1.25 for the cobalt nitrate precursor, while the maximum surface area of 182.1 m2/g was attained at ϕ=1 for the cobalt acetate precursor. The synthesized CoFe2O4 powders from the cobalt nitrate precursor exhibited the higher saturation magnetization and coercivity on account of the higher purity and crystallinity. 相似文献
1000.
Significance of char active surface area for appraising the reactivity of low- and high-temperature chars 总被引:1,自引:0,他引:1
M. Rashid Khan 《Fuel》1987,66(12):1626-1634
Contemporary char reactivity studies have focussed primarily on coal chars prepared under severe (high-temperature) conditions. In this study, the reactivity of chars prepared under mild (low-temperature) conditions has been addressed. A thermogravimetric analysis system (TGA) was used to determine the reactivity of chars in oxidizing atmosphere using isothermal or non-isothermal techniques. Coal chars were prepared in a TGA or in a slow heating rate organic devolatilization reactor (SHRODR) at a temperature range between 500 ° and 950 °C. The chars prepared by mild pyrolysis of coal at 500 °C are shown to be highly reactive. Comparison of reactivities of low- and high-temperature chars shows that the low-temperature chars exhibit higher reactivity than either the parent coals or the high-temperature chars. Correlation between isothermal reactivity results (e.g. time) and non-isothermal reactivity data (e.g. temperature) has been obtained. Hydrogen contents of chars correlate well with the reactivity of the chars. The study confirms the importance of oxygen chemisorption capacity as a significant reactivity parameter for both low- and high-temperature chars. A new approach has been used for calculating the oxygen chemisorption capacity of chars by accounting for the carbon surface sites occupied by hydrogen (and, therefore, these sites were unavailable for oxygen chemisorption). The occupied sites are readily freed during reactivity measurements and thus were available for participation in carbon-oxygen reactions. 相似文献