全文获取类型
收费全文 | 265888篇 |
免费 | 26850篇 |
国内免费 | 15830篇 |
专业分类
电工技术 | 21010篇 |
技术理论 | 13篇 |
综合类 | 23106篇 |
化学工业 | 38458篇 |
金属工艺 | 16028篇 |
机械仪表 | 17863篇 |
建筑科学 | 21949篇 |
矿业工程 | 8206篇 |
能源动力 | 7770篇 |
轻工业 | 22474篇 |
水利工程 | 6250篇 |
石油天然气 | 13103篇 |
武器工业 | 2979篇 |
无线电 | 30808篇 |
一般工业技术 | 26760篇 |
冶金工业 | 10098篇 |
原子能技术 | 2981篇 |
自动化技术 | 38712篇 |
出版年
2024年 | 1040篇 |
2023年 | 4115篇 |
2022年 | 8304篇 |
2021年 | 11605篇 |
2020年 | 8704篇 |
2019年 | 6745篇 |
2018年 | 7486篇 |
2017年 | 8743篇 |
2016年 | 7649篇 |
2015年 | 11558篇 |
2014年 | 14798篇 |
2013年 | 17383篇 |
2012年 | 20444篇 |
2011年 | 21706篇 |
2010年 | 19963篇 |
2009年 | 18785篇 |
2008年 | 18646篇 |
2007年 | 17586篇 |
2006年 | 16246篇 |
2005年 | 12785篇 |
2004年 | 8969篇 |
2003年 | 7586篇 |
2002年 | 7419篇 |
2001年 | 6437篇 |
2000年 | 5233篇 |
1999年 | 4286篇 |
1998年 | 2884篇 |
1997年 | 2296篇 |
1996年 | 2094篇 |
1995年 | 1694篇 |
1994年 | 1376篇 |
1993年 | 899篇 |
1992年 | 745篇 |
1991年 | 542篇 |
1990年 | 400篇 |
1989年 | 351篇 |
1988年 | 229篇 |
1987年 | 165篇 |
1986年 | 141篇 |
1985年 | 60篇 |
1984年 | 52篇 |
1983年 | 44篇 |
1982年 | 52篇 |
1981年 | 62篇 |
1980年 | 72篇 |
1979年 | 32篇 |
1978年 | 11篇 |
1976年 | 12篇 |
1959年 | 18篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
192.
193.
Dujuan Li Wei Yan Ronghui Qi Li-Zhi Zhang 《International Journal of Hydrogen Energy》2021,46(14):9267-9279
PEM-based electrolytic air dehumidification is innovative in dehumidification that requires high precision and small space due to its high efficiency, compactness, and cleanness. However, the system dehumidification performance and durability are limited by using commercial Anatase-IrO2 catalysts. In this study, two types of structurally modified OER catalyst materials, ATO-IrO2 and ND-MnO2-IrO2, are developed to improve the performance of the system. System experiments showed that, compared to the commercial catalysts, the use of ATO-IrO2 and ND-MnO2-IrO2 as the anode catalyst can improve the dehumidification performance by 45% and 20%, respectively. Furthermore, in 50-h accelerated aging tests, the attenuation rates of the ATO-IrO2 and ND-MnO2-IrO2 systems are 3% and 8% respectively, which are far lower than the 35% attenuation of commercial catalyst. The results indicate that, as catalysts with a classic core-shell structure, ATO-IrO2 and ND-MnO2-IrO2 still have a significant impact on improving the performance of the electrolytic dehumidification systems. 相似文献
194.
Ziqian Wang Yalan Chen Yating He Weidong Jiang Yan Long Guangyin Fan 《International Journal of Hydrogen Energy》2021,46(21):11587-11596
Developing high-efficiency and low-cost catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) is significant and critical for the exploitation and utilization of hydrogen energy. Herein, the in-situ fabrication of well-dispersed and small bimetallic RuNi alloy nanoparticles (NPs) with tuned compositions and concomitant hydrolysis of AB are successfully achieved by using graphitic carbon nitride (g-C3N4) as a NP support without additional stabilizing ligands. The optimized Ru1Ni7.5/g-C3N4 catalyst exhibits an excellent catalytic activity with a high turnover frequency of 901 min?1 and an activation energy of 28.46 kJ mol?1 without any base additives, overtaking the activities of many previously reported catalysts for AB hydrolysis. The kinetic studies indicate that the AB hydrolysis over Ru1Ni7.5/g-C3N4 is first-order and zero-order reactions with respect to the catalyst and AB concentrations, respectively. Ru1Ni7.5/g-C3N4 has a good recyclability with 46% of the initial catalytic activity retained even after five runs. The high performance of Ru1Ni7.5/g-C3N4 should be assigned to the small-sized alloy NPs with abundant accessible active sites and the synergistic effect between the composition-tuned Ru–Ni bimetals. This work highlights a potentially powerful and simple strategy for preparing highly active bimetallic alloy catalysts for AB hydrolysis to generate hydrogen. 相似文献
195.
近年来,科技发展持续发展,人们的生活愈加富足.城市化进程不断加快,各种市场主体层出不穷,对消防监测培训工作提出更高的要求.在如今多媒体信息智能时代,如何逐步改进防火监测工作,通过先进信息手段提高防火监测工作的实效和成果,是防火部门始终摸索和研讨的问题.文章主要研究了当前防火监测管理任务中存在的弊端,深入研究了信息时代防火监测工作的改进举措,并为现代防火监测培训工作提出一些建议. 相似文献
196.
针对目前蒸汽吞吐产量预测模型假设条件简单、普适性差等问题,一般采用测试法和类比法综合确定海上稠油油田蒸汽吞吐初期产量。由于目前海上油田通常只开展常规测试,无法直接获得热采开发初期产量。笔者提出海上稠油油田蒸汽吞吐初期产量确定新方法,建立蒸汽吞吐相对于常规开发的初期产量倍数预测模型,通过蒸汽吞吐产量倍数,将常规测试确定的产量转化为蒸汽吞吐产量。研究表明,蒸汽吞吐初期产量倍数主要受储集层渗透率、原油黏度、注入强度、蒸汽干度等因素影响,利用正交试验设计和多元回归等方法,建立海上稠油油田蒸汽吞吐初期产量倍数与油藏地质参数及注入参数之间的非线性预测模型,该模型经实际生产数据验证,预测误差小于5%,可靠性高,能够为海上稠油油田蒸汽吞吐初期产量的确定提供依据。 相似文献
197.
This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests. 相似文献
198.
199.
200.