全文获取类型
收费全文 | 107318篇 |
免费 | 5524篇 |
国内免费 | 3506篇 |
专业分类
电工技术 | 4700篇 |
技术理论 | 27篇 |
综合类 | 7550篇 |
化学工业 | 15996篇 |
金属工艺 | 4582篇 |
机械仪表 | 5728篇 |
建筑科学 | 10781篇 |
矿业工程 | 6146篇 |
能源动力 | 6232篇 |
轻工业 | 11006篇 |
水利工程 | 2222篇 |
石油天然气 | 7584篇 |
武器工业 | 2172篇 |
无线电 | 8613篇 |
一般工业技术 | 5587篇 |
冶金工业 | 6041篇 |
原子能技术 | 524篇 |
自动化技术 | 10857篇 |
出版年
2024年 | 171篇 |
2023年 | 1064篇 |
2022年 | 2320篇 |
2021年 | 2961篇 |
2020年 | 3108篇 |
2019年 | 1951篇 |
2018年 | 1663篇 |
2017年 | 2420篇 |
2016年 | 2679篇 |
2015年 | 2942篇 |
2014年 | 7808篇 |
2013年 | 6043篇 |
2012年 | 7967篇 |
2011年 | 8299篇 |
2010年 | 6470篇 |
2009年 | 6461篇 |
2008年 | 5743篇 |
2007年 | 7138篇 |
2006年 | 6665篇 |
2005年 | 5797篇 |
2004年 | 4984篇 |
2003年 | 4580篇 |
2002年 | 3818篇 |
2001年 | 3151篇 |
2000年 | 2459篇 |
1999年 | 1926篇 |
1998年 | 1319篇 |
1997年 | 970篇 |
1996年 | 820篇 |
1995年 | 658篇 |
1994年 | 506篇 |
1993年 | 317篇 |
1992年 | 285篇 |
1991年 | 193篇 |
1990年 | 154篇 |
1989年 | 126篇 |
1988年 | 91篇 |
1987年 | 55篇 |
1986年 | 55篇 |
1985年 | 43篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 13篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
21.
Hydrogen production via ammonia decomposition catalyzed by Ni/M–Mo–N (M = Ni,Co) bimetallic nitrides
《International Journal of Hydrogen Energy》2022,47(77):32893-32902
This study demonstrates the significant improvement in NH3 decomposition using Ni-decorated M–Mo–N-based catalysts (M = Co and Ni) compared with conventional catalysts. Catalysts are prepared using a mixture of the corresponding metal salts and hexamethylenetetramine, and the impregnation method is used to decorate the Ni-particles on the catalysts. Among all the samples, 10 wt% Ni-decorated Co3Mo3N exhibits the highest NH3 conversion rate (71%) at 500 °C, and the performance remains stable for 30 h of long-term testing. According to the gas chromatography measurements, the H2/N2 ratio is approximately 3 in all cases, which is consistent with the theoretical value. X-ray photoelectron spectroscopy results show that Co3Mo3N possesses the highest NH3 conversion efficiency because of the weaker binding energy of Mo–N. Furthermore, Co3Mo3N exhibits a stronger Lewis acidity and higher NH3 decomposition, which is attributed to the easy breaking of the N–H bond on the Co3Mo3N surface. 相似文献
22.
Effect of heat loss on the syngas production by fuel-rich combustion in a divergent two-layer burner
《International Journal of Hydrogen Energy》2022,47(34):15270-15281
The effect of heat loss on the syngas production from partial combustion of fuel-rich in a divergent two-layer burner is numerically studied using two-dimensional model with detailed kinetics GRI-Mech 1.2. Both the radiation and wall heat losses to the surrounding are considered in the computations. It is shown that two types heat losses have different effects on the syngas production. The radiation heat loss has significant effect on the syngas temperature and the syngas temperature is dropped as radiation heat loss is increased, but it has neglected effect on the reforming efficiency and methane conversion efficiency. The wall heat loss has a comprehensive effect on the syngas production. The wall heat loss not only reduces the conversion efficiency, but also significantly decreases the syngas temperature. The effect of wall heat loss becomes weak as the equivalence is increased. The reforming efficiency drops from 0.440 to 0.424 for equivalence ratio of 2 and mixture velocity of 0.17 m/s for the predictions between adiabatic wall and non-adiabatic conditions. 相似文献
23.
《Ceramics International》2022,48(8):10921-10931
Coatings were obtained by vacuum electro-spark alloying (VESA), pulsed cathodic arc evaporation (PCAE), magnetron sputtering (MS) techniques and VESA-PCAE-MS hybrid technology using Cr3C2–NiAl electrodes. The structure of the coatings was analyzed using scanning and transmission electron microscopy, X-ray diffraction and energy-dispersive spectroscopy. Mechanical properties were determined by nanoindentation, while tribological properties were assessed using pin-on-disk tribometer. Corrosion resistance was estimated by voltammetry in 1 N H2SO4 and 3.5%NaCl solutions. Oxidation resistance tests were performed at 800°С in air. The VESA coating had the highest thickness, low friction coefficient and high wear resistance. PCAE coating demonstrated the highest hardness (24 GPa) and elastic recovery (59%), oxidation resistance and superior corrosion resistance both in 1 N H2SO4 (icorr = 70 μА/cm2) and 3.5%NaCl (icorr = 0.74 μА/cm2) solutions. The MS coating had average mechanical properties and low corrosion current density (71 μА/cm2) in 1 N H2SO4. Deposition of coatings using VESA-PCAE-MS hybrid technology led to an increase in corrosion and oxidation resistance at least by 1.5 times in comparison with the VESA coating. 相似文献
24.
25.
华治国 《混凝土与水泥制品》2020,(6):70-72
选择了几份典型的外墙外保温系统标准,通过对这几份标准中胶粘剂和抹面胶浆的成型和检测方法的比较,分析了现有检测技术的优劣,并结合工作实践提出了建议。 相似文献
26.
构建工程咨询机构BIM技术应用能力评价的指标体系,提出改进的熵权TOPSIS评价模型,以4个典型的工程咨询单位为例,进行BIM技术运用能力评价。研究表明,BIM行业的整体水平已经有了明显的提升,但是区域间的发展还存在一定差距。 相似文献
27.
Zhongkai Zhao Yohanes A. Situmorang Ping An Nichaboon Chaihad Jing Wang Xiaogang Hao Guangwen Xu Abuliti Abudula Guoqing Guan 《化学工程与技术》2020,43(4):625-640
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils. 相似文献
28.
低品位热能制氢技术首先是将热能转换为溶液浓差能,然后通过逆电渗析(RED)反应器将溶液浓差能转换成氢能。为了验证RED反应器能将溶液浓差能转换为氢能,探索关键运行参数变化对能量转换过程的影响。设计了一个由40个膜对所构成的RED反应器,以NaCl水溶液为工作溶液,NaOH水溶液为电极液的制氢系统。通过改变浓/稀溶液入口浓度,溶液过膜流速以及输出电流来考察对RED反应器产氢率、制氢效率和能量转换效率的影响。实验结果发现,浓/稀溶液入口浓度,过膜流速变化均会影响RED反应器的输出电流。在外电路短接条件下,输出电流越大,反应器产氢率和制氢效率越高,但能量转换效率越低。 相似文献
29.
《Oil and Energy Trends》2020,45(1):56-58
Currency exchanges rates – updated monthly. Economic indicators of industrial production. Countries included: France, Germany, Italy, the United Kingdom, the United States, Canada, Japan (Total G-7), Eurozone and Total EU-28 (Total OECD). Updated monthly. Economic indicators of car registration in the United States, Canada, France, Germany, Italy, Poland, Spain, Turkey, the United Kingdom, Japan, Republic of Korea and Other OECD (Total OECD-30). Updated monthly. Monthly averages of crude steel production in thousand metric tons for the United States, Canada, Brazil, Mexico, Austria, Belgium, Czech Republic, France, Germany, Italy, Netherlands, Poland, Spain, Sweden, Turkey, the United Kingdom, Russia, Ukraine, South Africa, Iran, China, India, Japan, Republic of Korea, Taiwan and Australia. 相似文献
30.
添加剂是铜电解精炼生产管理的最关键要素,合适的添加剂使用方案可以有效保障电解生产系统长期稳定。结合添加剂生产实践和其它电解厂添加剂管理优点,提出探索添加剂精细化管理,进一步保障和提升铜电解添加剂管理实效。 相似文献