全文获取类型
收费全文 | 339篇 |
免费 | 91篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 187篇 |
金属工艺 | 2篇 |
矿业工程 | 1篇 |
能源动力 | 4篇 |
轻工业 | 15篇 |
石油天然气 | 41篇 |
无线电 | 63篇 |
一般工业技术 | 108篇 |
冶金工业 | 5篇 |
原子能技术 | 5篇 |
出版年
2024年 | 3篇 |
2023年 | 40篇 |
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 29篇 |
2019年 | 42篇 |
2018年 | 30篇 |
2017年 | 26篇 |
2016年 | 25篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 6篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 15 毫秒
1.
氮杂冠醚合成中的双功能基试剂 总被引:1,自引:0,他引:1
综述了氮杂冠醚合成中的双功能基试剂的进展。着重讨论了典型的双功能基试剂,如取代多甘醇、二胺、氨基二醇、二卤代物、二醛和二酮以及3-烷氧丙烯醛等的制备方法。 相似文献
2.
Shufang Wang Yuanhui Ma Yanji Wang Wei Xue Xinqiang Zhao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1466-1471
BACKGROUND: A single‐step conversion of nitrobenzene (NB) to p‐aminophenol (PAP) through catalytic hydrogenation is a widely used synthesis route for PAP. The main shortcoming of this route is the use of sulfuric acid for rearrangement of the phenylhydroxylamine (PHA) intermediate. In this paper, S2O82?/ZrO2 (PSZ) solid acid and Pt‐S2O82?/ZrO2 (Pt‐PSZ) bifunctional catalysts were prepared for the synthesis of PAP in non‐acid medium. RESULTS: Calcination temperature has a substantial effect on the acidity, structure and activity for PHA rearrangement of PSZ. The highest PAP yield was 33.8% over PSZ calcined at 823 K when the reaction was carried out in water at 423 K. A high PAP yield of 23.9% was achieved by a single‐step reaction of nitrobenzene over Pt‐PSZ bifunctional catalysts. CONCLUSION: PSZ solid acid exhibits high activity for PHA rearrangement. Perfect tetragonal ZrO2 and much stronger acid sites play important roles in catalytic activity. Inhibiting the hydrogenation activity by reducing the amount of Pt loading on Pt‐PSZ can improve the competition of PHA rearrangement on acid sites with hydrogenation of PHA on metal active sites, resulting in better selectivity to PAP. Copyright © 2008 Society of Chemical Industry 相似文献
3.
对H2-O2气氛中丙烯环氧化反应所采用的催化剂、反应器及操作方式进行了评述.综合分析了所使用的钯(金或银)/钛硅分子筛(或氧化钛)双功能催化剂的各项性能指标以及所采用的反应器型式.结合H2-O2直接合成H2O2所用催化剂,对原位氧化丙烯反应过程进行了系统描述.指出进一步的研究方向是借助反应或分离耦合技术,创造有利于原位生成的H2O2及时进行环氧化而避免分解的操作环境,包括催化剂表面状态、反应器型式、溶剂体系和操作方式,并提出以丙烷路线经脱氢、环氧化是制取环氧丙烷的最佳组合. 相似文献
4.
5.
为开发高活性、高收率的合成气制低碳烯烃(STO)双功能催化剂,通过共沉淀法制备非化学计量尖晶石Zn-Cr-Al氧化物,对其织构性质、晶体结构、形貌特征以及表面电荷性质等进行研究。结果表明添加过量锌能够促进晶体粒径减小,表面氧空位增多。其中Zn/(Cr+Al)摩尔比为1.25时锌含量较为适宜,将其与SAPO-34沸石分子筛结合为双功能催化剂用于STO性能研究。在进气n(H2):n(CO)=2:1,3000 mL/(gcat·h),3.2 MPa,400 ℃反应条件下,实现46.9% CO转化率,C2-4烯烃收率高达15.9%,高于大部分已有文献报道(8~14%),特别是副产物CO2选择性仅29.2%,低于普遍报道的40~50% CO2选择性。并且催化剂运行100 h后活性良好,稳定的催化性能使其具有工业应用价值。 相似文献
6.
Xiao Fan Baitang Jin Shoujie Ren Shiguang Li Miao Yu Xinhua Liang 《American Institute of Chemical Engineers》2021,67(11):e17353
The roles of interaction between two catalyst components in CuO–ZnO–ZrO2–Al2O3 (CZZA)/HZSM-5 bifunctional catalyst for dimethyl ether (DME) synthesis via carbon dioxide hydrogenation were investigated. It was found that CZZA catalyst showed excellent stability during methanol (MeOH) synthesis for 100 h, while there was a severe loss of catalytic activity in the bifunctional catalyst for DME synthesis. Hence, the effects of different degrees of intimacy of two catalyst components were studied for DME synthesis, including mixed and separated modes. For the mixed mode, the particle size of catalysts and the amount of reaction intermediates were proven to influence the catalyst deactivation. For the separated mode, the catalysts showed rapid deactivation within a short time. Various characterizations indicated that the remarkable deactivation of separated mode was mainly caused by the decrease of copper active centers (e.g., sintering and oxidation) and blockage of acid sites via increased coke deposition on HZSM-5. 相似文献
7.
Huanran Zheng Shibin Wang Shoujie Liu Jiao Wu Jianping Guan Qian Li Yuchao Wang Yu Tao Shouyao Hu Yu Bai Jinxian Wang Xiang Xiong Yu Xiong Yongpeng Lei 《Advanced functional materials》2023,33(40):2300815
The rational design and construction of efficient and inexpensive bifunctional oxygen electrocatalysts are highly desirable for the development of rechargeable Zn–air batteries (ZABs). Although single-atom Fe sites anchored on N-doped carbon catalysts (Fe1/NC) ensure high oxygen reduction reaction activity, their unitary atomically dispersed active center faces difficult condition in catalyzing oxygen evolution reaction simultaneously. Herein, a composite catalyst containing heterointerface between Fe1/NC and selenides ((Fe,Co)Se2) is constructed. The obtained (Fe,Co)Se2@Fe1/NC exhibits extremely narrow potential gap of 0.616 V and remarkable stability in alkaline media, outperforming the benchmark catalysts (Pt/C+RuO2: 0.720 V). Experimental results and density functional theory calculations reveal that heterointerface between Fe1/NC and (Fe,Co)Se2 accelerates the electron transfer and provides more moderate adsorption sites, which endow (Fe,Co)Se2@Fe1/NC with extremely high bifunctional oxygen catalytic activity. This study not only provides a superior bifunctional catalyst for ZABs, but also enriches the application of single-atom catalysts in multifunctional energy storage and conversion devices. 相似文献
8.
Xin Ding Run Jiang Jialin Wu Minghui Xing Zelong Qiao Xiaofei Zeng Shitao Wang Dapeng Cao 《Advanced functional materials》2023,33(47):2306786
Developing low-cost and high-efficient bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is greatly significant for water electrolysis. Here, Ni3N-CeO2/NF heterostructure is synthesized on the nickel foam, and it exhibits excellent HER and OER performance. As a result, the water electrolyzer based on Ni3N-CeO2/NF bifunctional catalyst only needs 1.515 V@10 mA cm−2, significantly better than that of Pt/C||IrO2 catalysts. In situ characterizations unveil that CeO2 plays completely different roles in HER and OER processes. In situ infrared spectroscopy and density functional theory calculations indicate that the introduction of CeO2 can optimizes the structure of interface water, and the synergistic effect of Ni3N and CeO2 improve the HER activity significantly, while the in situ Raman spectra reveal that CeO2 accelerates the reconstruction of OV (oxygen vacancy)-rich NiOOH for boosting OER. This study clearly unlocks the different catalytic mechanisms of CeO2 for boosting the HER and OER activity of Ni3N for water splitting, which provides the useful guidance for designing the high-performance bifunctional catalysts for water splitting. 相似文献
9.
Mengmeng Liu Xiaohang Zhu Yujie Song Guanlin Huang Jiamin Wei Xiaokai Song Qi Xiao Tao Zhao Wan Jiang Xiaopeng Li Wei Luo 《Advanced functional materials》2023,33(11):2213395
Oxygen reduction reaction (ORR) and sulfur reduction reaction (SRR) play key roles in advanced batteries. However, they both suffer from sluggish reaction kinetics. Here, an interesting nitrogen doped porous carbon material that can simultaneously activate oxygen and sulfur is reported. The carbon precursor is a nitrogen containing covalent organic framework (COF), constituting periodically stacked 2D sheets. The COF structure is well preserved upon pyrolysis, resulting in the formation of edge-rich porous carbon with structure resembling stacked holey graphene. The nitrogen containing groups in the COF are decomposed into graphitic and pyridinic nitrogen during pyrolysis. These edge sites and uniform nitrogen doping endow the carbon product with high intrinsic catalytic activities toward ORR and SRR. The COF derived carbon delivers outstanding performances when assembling as cathodes in the Li-S and Li-O2 batteries. Simultaneous activation of oxygen and sulfur also enables a new battery chemistry. A proof-of-concept Li-S/O2 hybrid battery is assembled, delivering a large specific capacity of 2,013 mAh g−1. This study may inspire novel battery designs based on oxygen and sulfur chemistry. 相似文献
10.
A Cost‐Efficient Bifunctional Ultrathin Nanosheets Array for Electrochemical Overall Water Splitting
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ying Zhang Qi Shao Yecan Pi Jun Guo Xiaoqing Huang 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(27)
The design of cost‐efficient earth‐abundant catalysts with superior performance for the electrochemical water splitting is highly desirable. Herein, a general strategy for fabricating superior bifunctional water splitting electrodes is reported, where cost‐efficient earth‐abundant ultrathin Ni‐based nanosheets arrays are directly grown on nickel foam (NF). The newly created Ni‐based nanosheets@NF exhibit unique features of ultrathin building block, 3D hierarchical structure, and alloy effect with the optimized Ni5Fe layered double hydroxide@NF (Ni5Fe LDH@NF) exhibiting low overpotentials of 210 and 133 mV toward both oxygen evolution reaction and hydrogen evolution reaction at 10 mA cm?2 in alkaline condition, respectively. More significantly, when applying as the bifunctional overall water splitting electrocatalyst, the Ni5Fe LDH@NF shows an appealing potential of 1.59 V at 10 mA cm?2 and also superior durability at the very high current density of 50 mA cm?2. 相似文献