首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   749篇
  免费   149篇
  国内免费   26篇
电工技术   27篇
综合类   16篇
化学工业   438篇
机械仪表   1篇
建筑科学   1篇
矿业工程   11篇
能源动力   164篇
轻工业   3篇
石油天然气   225篇
无线电   1篇
一般工业技术   18篇
冶金工业   12篇
原子能技术   2篇
自动化技术   5篇
  2023年   18篇
  2022年   36篇
  2021年   32篇
  2020年   42篇
  2019年   44篇
  2018年   35篇
  2017年   18篇
  2016年   52篇
  2015年   31篇
  2014年   44篇
  2013年   49篇
  2012年   56篇
  2011年   65篇
  2010年   47篇
  2009年   59篇
  2008年   38篇
  2007年   23篇
  2006年   34篇
  2005年   22篇
  2004年   21篇
  2003年   21篇
  2002年   20篇
  2001年   15篇
  2000年   13篇
  1999年   15篇
  1998年   14篇
  1997年   12篇
  1996年   13篇
  1995年   14篇
  1994年   5篇
  1993年   6篇
  1990年   3篇
  1989年   1篇
  1951年   6篇
排序方式: 共有924条查询结果,搜索用时 15 毫秒
101.
Direct photoconversion of low‐concentration CO2 into a widely tunable syngas (i.e., CO/H2 mixture) provides a feasible outlet for the high value‐added utilization of anthropogenic CO2. However, in the low‐concentration CO2 photoreduction system, it remains a huge challenge to screen appropriate catalysts for efficient CO and H2 production, respectively, and provide a facile parameter to tune the CO/H2 ratio in a wide range. Herein, by engineering the metal sites on the covalent organic frameworks matrix, low‐concentration CO2 can be efficiently photoconverted into tunable syngas, whose CO/H2 ratio (1:19–9:1) is obviously wider than reported systems. Experiments and density functional theory calculations indicate that Fe sites serve as the H2 evolution sites due to the much stronger binding affinity to H2O, while Ni sites act as the CO production sites for the higher affinity to CO2. Notably, the widely tunable syngas can also be produced over other Fe/Ni‐based bimetal catalysts, regardless of their structures and supporting materials, confirming the significant role of the metal sites in regulating the selectivity of CO2 photoreduction and providing a modular design strategy for syngas production.  相似文献   
102.
Pt–Re supported on Ce0.52 Zr0.48 O2 was studied for the carbon dioxide reforming of methane at 800 °C. Diffuse reflectance fourier transform infrared spectroscopy and temperature programmed reduction studies suggest that Pt and Re segregation occurs during the reaction. The segregation results in an increase in the Pt sites available for CH4 decomposition and results in the bimetallic catalyst exhibiting an increase in the conversion of methane with time on stream. After 20 h of reaction, the CH4 conversion observed for the bimetallic catalyst was the same as the CH4 conversion observed for the monometallic catalyst.  相似文献   
103.
由下行床热解和提升管(或输送床)气化组合形成的流化床两段气化将煤气化反应过程解耦为煤热解和半焦气化两个反应阶段,热解产物完全进入气化反应器,利用其中的高温环境和输送的半焦催化作用分别实现焦油的热裂解与催化裂解,完成低焦油气化。利用该流化床两段气化的10 kg/h级实验室工艺实验装置,以榆林烟煤为原料、水蒸气/氧气作为气化剂,变化过量氧气系数ER、蒸汽炭比S/C、热解及气化温度等参数,研究水蒸气/氧流化床两段煤气化制备低焦油合成气的特性。结果表明,流化床两段气化系统可实现稳定运行(实验3 h以上),在ER=0.36和S/C=0.15时,热解和气化的代表温度分别稳定在735℃和877℃,合成气的CO、CO2、H2、CH4、C n H m 和N2含量分别为14.33%、10.07%、18.39%、9.89%、1.82%和45.50%,相应的合成气产量达到1.8 m3/kg,低位热值8.99 MJ/m3,焦油含量0.437 g/m3,展示了制备低焦油合成气的技术特征。对于实际的长时间连续运行,更高的气化温度将使流化床两段气化具有更好的低焦油特性。  相似文献   
104.
A novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo0.4Fe0.4Zr0.2O3– and the catalyst of LiLaNiO/-Al2O3. The POM reaction was performed successfully. Not only was a short induction period of 2 h obtained, but also a high catalytic performance of 96–98% CH4 conversion, 98–99% CO selectivity and an oxygen permeation flux of 5.4–5.8 mlcm–2min–1 (1.9–2.0 molm–2S–1Pa–1) at 850°C were achieved. Moreover, the reaction has been steadily carried out for more than 2200 h, and no interaction between the membrane material and the catalyst took place.  相似文献   
105.
天津IGCC是中国第一座整体煤气化联合循环电站。系统中燃气轮机的燃料为气化炉产生的热值较低的合成气,作为国内第一台应用于IGCC技术的燃气轮机,在运行过程中存在着合成气热值与设计值偏差大、烧嘴过热、燃烧室偏烧等问题。针对存在的问题,首先介绍了IGCC电站燃用低热值燃料的燃气轮机与普通燃气轮机在燃料、燃烧方式、燃烧器结构等方面的区别;然后结合实际运行参数分析,重点对存在的问题提出性能优化方案及措施。对燃用低热值燃料的燃气轮机后续发展具有一定的借鉴意义。  相似文献   
106.
王剑钊  钟祎勍  孙阳阳  周贤 《中国电力》2019,52(2):20-25,45
以国内250 MW级IGCC电站为研究对象,根据电站的运行特性和控制要求,介绍了协调控制系统的设计、系统的基本组成、负荷指令以及气化炉和燃机的控制策略。提出了气化炉控制为主、燃机/汽机跟随的负荷控制方案,现场运行结果表明,该方案简捷有效,完全能够满足IGCC机组的控制要求。  相似文献   
107.
The direct synthesis of lower olefins via the Fischer‐Tropsch reaction (FTO) has been performed over a series of Fe‐MnOx/SiO2 catalysts. The addition of MnOx could improve the dispersion of iron species, and promote the reduction of iron oxide during the activation and subsequent carburization. Moreover, the results of characterization demonstrated that MnOx could enhance the surface basicity of the catalysts due to electronic effects and promote the formation of iron carbides. For the first time, the intrinsic power‐law kinetics for FTO was obtained for both Fe20/SiO2 and Fe20‐Mn1/SiO2 catalysts. Kinetic parameters and structure characterizations indicated that MnOx could facilitate the CO dissociation on the catalyst surface, thus enhancing the adsorption strength and capacity of surface carbonaceous intermediates. The weak hydrogenation of carbonaceous species would boost the selectivities toward lower olefins. Finally, a plausible mechanism for FTO, involving the promotional effects of MnOx on Fe, has been proposed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4451–4464, 2017  相似文献   
108.
Process systems were investigated for syngas production from CO2 and renewable energy (solar) by the reverse water‐gas shift (RWGS) and the reverse water‐gas shift chemical looping (RWGS‐CL) process. Thermodynamic analysis and optimization was performed to maximize the solar‐to‐syngas (StS) efficiency ηStS. Special emphasis was laid on product gas separation. For RWGS‐CL, maximum StS efficiencies of 14.2 and 14.4% were achieved without and with heat integration, respectively. The StS efficiency is dictated by the low overall efficiency of H2 production. RWGS‐CL is most beneficial for the production of pure CO, where the StS efficiency is one percent point higher compared to that of the RWGS process with heat integration. Heat integration leads to significant reductions in external heat demand since most of the gas phase process heat can be integrated. The StS efficiencies for RWGS and RWGS‐CL achieve the same level as the reported values for solar thermochemical syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 63: 15–22, 2017  相似文献   
109.
王永锋 《化工设计》2004,14(2):49-51
介绍壳牌煤气化工艺流程中的合成气反吹系统的反吹介质可由洗涤后的粗合成气改为高温高压氮气。改造后 ,出气化装置的合成气组分既可满足下游装置的工艺要求 ,又可节省大量的工程投资  相似文献   
110.
Mg调变Ni基催化剂上甲烷部分氧化制合成气   总被引:8,自引:2,他引:6  
在固定床流动反应装置上考察了不同反应条件对Mg调变Ni基催化剂反应性能的影响。当催化剂床层径高比约为2,空速20×105h-1,床层最高温度940℃,V(CH4)/V(O2)=20时,甲烷转化率97%,CO选择性98%,H2选择性接近100%。500h的稳定性考察结果表明,甲烷转化率大于90%,CO及H2选择性均大于95%。反应后的催化剂经SEM分析没观察到积炭。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号