全文获取类型
收费全文 | 6370篇 |
免费 | 810篇 |
国内免费 | 229篇 |
专业分类
电工技术 | 267篇 |
综合类 | 306篇 |
化学工业 | 2447篇 |
金属工艺 | 238篇 |
机械仪表 | 76篇 |
建筑科学 | 423篇 |
矿业工程 | 507篇 |
能源动力 | 278篇 |
轻工业 | 285篇 |
水利工程 | 27篇 |
石油天然气 | 1263篇 |
无线电 | 211篇 |
一般工业技术 | 468篇 |
冶金工业 | 555篇 |
原子能技术 | 20篇 |
自动化技术 | 38篇 |
出版年
2024年 | 37篇 |
2023年 | 130篇 |
2022年 | 208篇 |
2021年 | 191篇 |
2020年 | 274篇 |
2019年 | 250篇 |
2018年 | 199篇 |
2017年 | 236篇 |
2016年 | 299篇 |
2015年 | 260篇 |
2014年 | 452篇 |
2013年 | 410篇 |
2012年 | 459篇 |
2011年 | 491篇 |
2010年 | 338篇 |
2009年 | 290篇 |
2008年 | 248篇 |
2007年 | 331篇 |
2006年 | 336篇 |
2005年 | 297篇 |
2004年 | 245篇 |
2003年 | 262篇 |
2002年 | 200篇 |
2001年 | 178篇 |
2000年 | 155篇 |
1999年 | 133篇 |
1998年 | 98篇 |
1997年 | 68篇 |
1996年 | 80篇 |
1995年 | 44篇 |
1994年 | 28篇 |
1993年 | 32篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有7409条查询结果,搜索用时 15 毫秒
61.
The sulfur tolerance of a barium-containing NOx storage/reduction trap was investigated using infrared analysis. It was confirmed that barium carbonate could be replaced by barium sulfate by reaction with low concentrations of sulfur dioxide (50 ppm) in the presence of large concentrations of carbon dioxide (10%) at temperatures up to 700 °C. These sulfates could at least be partially removed by switching to hydrogen-rich conditions at elevated temperatures. Thermodynamic calculations were used to evaluate the effects of gas composition and temperature on the various reactions of barium sulfate and carbonate under oxidizing and reducing conditions. These calculations clearly showed that if, under a hydrogen-rich atmosphere, carbon dioxide is included as a reactant and barium carbonate as a product then barium sulfate can be removed by reaction with carbon dioxide at a much lower temperature than is possible by decomposition to barium oxide. It was also found that if hydrogen sulfide was included as a product of decomposition of barium sulfate instead of sulfur dioxide then the temperature of reaction could be significantly lowered. Similar calculations were conducted using a selection of other alkaline-earth and alkali metals. In this case calculations were simulated in a gas mixture containing carbon monoxide, hydrogen and carbon dioxide with partial pressures similar to those encountered in real exhausts during switches to rich conditions. The results indicated that there are metals such as lithium and strontium with less stable sulfates than barium, which may also possess sufficient NOx storage capacity to give sulfur-tolerant NOx traps. 相似文献
62.
Transient experiments were performed to study sulfur deactivation and regeneration of Pt/BaO/Al2O3 and Pt/SrO/Al2O3 NO
x
storage catalysts. It was found that the strontium-based catalysts are more easily regenerated than the barium-based catalysts
and that a higher fraction of the NO
x
storage sites are regenerated when H2 is used in combination with CO2 compared to H2 only. 相似文献
63.
64.
壳牌煤气化配套硫回收工艺方案的选择 总被引:2,自引:0,他引:2
对壳牌煤气化合成气处理技术进行了分析,总结了从粗煤气中脱除的酸性气的特点。对硫回收技术的8种工艺方案从H2S浓度要求、生产能力、环保、投资和运行费用方面进行了对比,指出了壳牌煤气化硫回收工艺方案的选择要领。 相似文献
65.
天然气中含汞会对天然气的开发及使用带来危害,实验采用固定床吸附法脱除天然气中的汞。实验以Al2O3和活性炭复合颗粒为载体,通过浸渍法负载S、CuS和CuS x 多组分活性物,制备了天然气脱汞吸附剂,考察了制备工艺条件的影响。采用X射线衍射检测(XRD)与扫描电镜(SEM)对活性物负载情况进行了表征。结果表明,在载体上成功负载了CuS和S,其中CuS质量分数为12.80%,总S质量分数为8.32%。以含汞空气模拟含汞天然气,考察了进气口汞含量、停留时间对脱汞吸附剂脱汞效果的影响。结果表明,脱汞剂处理汞含量为300μg/m3的天然气,停留时间为1s时,出口汞含量为24.99μg/m3,已达到工业天然气要求。当停留时间为2s、进气口汞含量达到600μg/m3时,经脱汞剂脱汞后,出口汞含量为18.92μg/m3,达到小于28μg/m3要求。脱汞吸附剂的汞容量达到6.36%。 相似文献
66.
为了寻求炼铁、炼钢工序经济适宜的铁水硫含量,通过对生产数据的统计,分析了攀钢西昌钢钒1号高炉铁水硫含量与技术经济指标的关系,得到了攀钢西昌钢钒高炉铁水钛含量与铁水硫含量及焦比的回归公式;并依据高炉冶炼过程中实际的矿焦比与铁水钛含量的经验数据,计算分析了不同铁水硫含量与炼铁的原、燃料成本的关系,综合考虑炼钢脱硫成本的变化,得出当前硫负荷条件下铁水适宜的硫含量(质量分数)应控制在0.085%左右. 相似文献
67.
68.
The aim of this study was to improve the understanding of the deleterious effect of sulfur impurities on the adherence of the thermally-grown oxide on the boundary layer in thermal-barrier-coating systems. In Part I, the sulfur segregation on the free surface of NiAl(001) and at different interfaces between metal and transient alumina scales has been characterized by AES, XPS and LEED. The sulfur diffusion coefficient in the alloy has been determined (D = 0.15 exp(–218,000/RT) cm2/s). It is by three orders of magnitude larger than the nickel and aluminum self-diffusion coefficients. It has also been observed that the sulfur de-segregates upon Al enrichment of the metallic surface. The saturation of the metallic surface with an amorphous alumina layer formed at room temperature blocks the segregation of S. However, in the initial stages of oxidation where the transient -alumina grows by cationic transport and inject vacancies at the interface, S segregates at the interface between the alumina thin films and the metallic substrate. 相似文献
69.
70.
1 INTRODUCTIONCyanidationprocess ,characterizedbyeffectivenessandlowoperatingcost,asaconventionaltechnologyforgoldextractionfromores ,hasbeenusedinindustryforover 10 0years .Howeverthecyanideisahighlytoxicchemical,andcommercialcyanidationprocessislimitedint… 相似文献