全文获取类型
收费全文 | 49403篇 |
免费 | 4526篇 |
国内免费 | 2467篇 |
专业分类
电工技术 | 3041篇 |
技术理论 | 5篇 |
综合类 | 3913篇 |
化学工业 | 8310篇 |
金属工艺 | 2687篇 |
机械仪表 | 2930篇 |
建筑科学 | 3953篇 |
矿业工程 | 1149篇 |
能源动力 | 1272篇 |
轻工业 | 5429篇 |
水利工程 | 1097篇 |
石油天然气 | 2463篇 |
武器工业 | 448篇 |
无线电 | 5283篇 |
一般工业技术 | 5198篇 |
冶金工业 | 1893篇 |
原子能技术 | 593篇 |
自动化技术 | 6732篇 |
出版年
2024年 | 239篇 |
2023年 | 790篇 |
2022年 | 1456篇 |
2021年 | 1984篇 |
2020年 | 1530篇 |
2019年 | 1217篇 |
2018年 | 1393篇 |
2017年 | 1575篇 |
2016年 | 1411篇 |
2015年 | 2023篇 |
2014年 | 2514篇 |
2013年 | 3058篇 |
2012年 | 3531篇 |
2011年 | 3801篇 |
2010年 | 3366篇 |
2009年 | 3256篇 |
2008年 | 3250篇 |
2007年 | 2990篇 |
2006年 | 2836篇 |
2005年 | 2442篇 |
2004年 | 1681篇 |
2003年 | 1328篇 |
2002年 | 1284篇 |
2001年 | 1064篇 |
2000年 | 1012篇 |
1999年 | 1073篇 |
1998年 | 832篇 |
1997年 | 689篇 |
1996年 | 601篇 |
1995年 | 513篇 |
1994年 | 377篇 |
1993年 | 282篇 |
1992年 | 246篇 |
1991年 | 177篇 |
1990年 | 128篇 |
1989年 | 109篇 |
1988年 | 92篇 |
1987年 | 47篇 |
1986年 | 58篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Xiao-Ya Shangguan Bao-Lun Fang Chen-Xiao Xu Yuan Tan Yan-Gang Chen Zhi-Jun Xia Wei Chen 《Ceramics International》2021,47(5):6318-6328
A series of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn2S4/Bi2WO6 nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn2S4 and Bi2WO6. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn2S4 in FeIn2S4/Bi2WO6 nanocomposites and the optimized component ratio of FeIn2S4 to Bi2WO6 is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn2S4/Bi2WO6 nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment. 相似文献
22.
Biyun Fang Chuanfeng Zhang Zeliang Qi Chunyan Li Jun Ni Xiuyun Wang Jianxin Lin Chak-Tong Au Bingyu Lin Lilong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17849
The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo2C/CeO2 catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce3+ and surface oxygen species. The presence of Mo2C and CeO2 overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO2 catalyst prepared without carbonization, the Mo2C/CeO2 catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis. 相似文献
23.
24.
This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach. 相似文献
25.
26.
29.
30.
Zhimei Zheng Taixiu Liu Qibin Liu Jing Lei Juan Fang 《International Journal of Hydrogen Energy》2021,46(38):19846-19860
Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation. 相似文献