全文获取类型
收费全文 | 7082篇 |
免费 | 457篇 |
国内免费 | 295篇 |
专业分类
电工技术 | 629篇 |
综合类 | 339篇 |
化学工业 | 553篇 |
金属工艺 | 227篇 |
机械仪表 | 603篇 |
建筑科学 | 184篇 |
矿业工程 | 78篇 |
能源动力 | 202篇 |
轻工业 | 587篇 |
水利工程 | 25篇 |
石油天然气 | 161篇 |
武器工业 | 47篇 |
无线电 | 1189篇 |
一般工业技术 | 875篇 |
冶金工业 | 99篇 |
原子能技术 | 100篇 |
自动化技术 | 1936篇 |
出版年
2024年 | 8篇 |
2023年 | 77篇 |
2022年 | 119篇 |
2021年 | 156篇 |
2020年 | 145篇 |
2019年 | 152篇 |
2018年 | 142篇 |
2017年 | 180篇 |
2016年 | 210篇 |
2015年 | 172篇 |
2014年 | 329篇 |
2013年 | 341篇 |
2012年 | 399篇 |
2011年 | 461篇 |
2010年 | 359篇 |
2009年 | 423篇 |
2008年 | 412篇 |
2007年 | 517篇 |
2006年 | 526篇 |
2005年 | 432篇 |
2004年 | 407篇 |
2003年 | 295篇 |
2002年 | 296篇 |
2001年 | 250篇 |
2000年 | 224篇 |
1999年 | 173篇 |
1998年 | 144篇 |
1997年 | 88篇 |
1996年 | 100篇 |
1995年 | 65篇 |
1994年 | 41篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有7834条查询结果,搜索用时 15 毫秒
1.
《中国稀土学报(英文版)》2022,40(8):1232-1237
Revealing the active species of the catalyst is conducive to the design of more efficient catalyst. Herein, we tried to demonstrate the roles of amorphous and crystalline structures on CePO4 catalyst during selective catalytic reduction (SCR) of NOx by NH3. Higher calcination temperature promotes the transfer of amorphous structure to crystalline structure on the surface of CePO4. Both amorphous and crystalline CePO4 species on CePO-X samples can provide acid sites for NH3 adsorption, but the former can provide more acid sites. The superior redox property of surface amorphous CePO4 species contributes to its high NH3-SCR activity at low temperature, but it also leads to the decrease of high temperature (>350 °C) NH3-SCR activity due to the oxidation of NH3. In contrast, crystalline CePO4 species shows high activity only at high temperature because of its poor redox property. Therefore, it can be inferred that amorphous and crystalline structures on CePO4 catalyst can be the efficient active species of NH3-SCR at low and high temperature, respectively. 相似文献
2.
Imbalance vibration is a typical failure mode of rotational machines and has significant negative effects on the effii-ciency,accuracy,and service life of equipment.To automatically reduce the imbalance vibration during the opera-tional process,different types of active balancing actuators have been designed and widely applied in actual produc-tion.However,the existing electromagnetic-ring active balancing actuator is designed based on an axial excitation structure which can cause structural instability and has low electromagnetic driving efficiency.In this paper,a novel radial excitation structure and the working principle of an electromagnetic-ring active balancing actuator with a combined driving strategy are presented in detail.Then,based on a finite element model,the performance param-eters of the actuator are analyzed,and reasonable design parameters are obtained.Self-locking torque measurements and comparative static and dynamic experiments are performed to validate the self-locking torque and driving effi-ciency of the actuator.The results indicate that this novel active balancing actuator has sufficient self-locking torque,achieves normal step rotation at 2000 r/min,and reduces the driving voltage by 12.5%.The proposed novel balancing actuator using radial excitation and a combination of permanent magnets and soft-iron blocks has improved electro-magnetic efficiency and a more stable and compact structure. 相似文献
3.
本文提出一种基于实时几何测距的船桥主动防撞方法。该方法对船的改动量甚微,仅需维持多项距离矩阵,通过告警逻辑矩阵进行展示与告警,能起到很好的船桥防撞提示效果。 相似文献
4.
5.
6.
Complex products such as satellites, missiles, and aircraft typically have demanding requirements for dynamic data management and process traceability. The assembly process for these complex products involves high complexity, strong dynamics, many uncertainties, and frequent rework and repair, especially in the model development stage. Achieving assembly data management and process traceability for complex products has always been a challenge. A recently proposed solution involves one-to-one mapping of the corresponding physical entity, also known as the digital twin method. This paper proposes a digital twin-based assembly data management and process traceability approach for complex products. First, the dynamic evolutionary process of complex product assembly data was analyzed from three dimensions: granularity, period and version. Then, a framework of digital twin-based assembly data management and process traceability for complex products was constructed. Some core techniques are: 1) workflow-based product assembly data organization and version management; 2) synchronous modeling of the product assembly process based on digital twin; and 3) hierarchical management and traceability of product assembly data based on digital twin. On this basis, an algorithm flowchart for generating a product assembly data package was created, which includes product assembly data management, assembly process traceability, and generation of a product assembly data package. Furthermore, the Digital Twin-based Assembly Process Management and Control System (DT-APMCS) was designed to verify the efficiency of the proposed approach. Some aerospace-related assembly enterprises are currently using DT-APMCS and achieving satisfactory results. Finally, a summary of our work is given, and the future research work is also discussed. 相似文献
7.
8.
In order to improve the global searching ability of Water Cycle Algorithm (WCA), the hierarchical learning concept is introduced and the Hierarchical Learning WCA (HLWCA) is proposed in this paper. The underlying idea of HLWCA is to divide the solutions into collections and give these collections with hierarchy differences. One of the collections has a higher hierarchy than others and utilizes an exploration-inclined updating mechanism. The solutions in this high hierarchy collection are the exemplars of other collections. The other collections are sorted according to the exemplars’ function value and the solutions in these collections actively choose whether to follow their own exemplar or not. Through different updating mechanisms of collections, the global searching ability is improved while the fast convergence and strong local search ability of WCA are retained. The proposed HLWCA is firstly experimented on IEEE CEC 2017 benchmark suite to testify its performance on complex numerical optimization tasks. Then, it is tested on four practical design benchmark problems to verify its ability of solving real-world problems. The experimental results illustrate the efficiency of the proposed algorithm. 相似文献
9.
为促进我国消费者对香肠的合理消费与饮食健康,引导企业生产营养健康的香肠,利用《中国食物成分表》(第1册第2版)的16 种香肠及其营养素数据,构建富含营养素食物(nutrient-rich foods,NRF9.3)模型,评价香肠整体营养价值,并借鉴瑞典的锁孔(Keyhole)标识和英国的多交通灯信号标签进行相应的包装正面(front of package,FOP)标签应用探索。结果表明:除了儿童肠、火腿肠外,14 种香肠的NRF9.3<0,每100 kcal的推荐性营养素含量均低于限制性营养素,对人体的营养价值较低,适合采用总结指示体系和特定营养素体系的FOP标签进行标示;因此,居民日常应限制香肠摄入,建议对脂肪、盐含量超标的香肠采用红色交通灯信号标签提醒消费者,对NRF9.3>0的香肠实施单一的健康选择标识推荐消费者选购。 相似文献
10.
Ze-Hao Wu 《International journal of control》2020,93(6):1408-1427
ABSTRACTIn this paper, we apply the active disturbance rejection control, an emerging control technology, to output-feedback stabilisation for a class of uncertain multi-input multi-output nonlinear systems with vast stochastic uncertainties. Two types of extended state observers (ESO) are designed to estimate both unmeasured states and stochastic total disturbance which includes unknown system dynamics, unknown stochastic inverse dynamics, external stochastic disturbance without requiring the statistical characteristics, uncertain nonlinear interactions between subsystems, and uncertainties caused by the deviation of control parameters from their nominal values. The estimations decouple approximately the system after cancelling stochastic total disturbance in the feedback loop. As a result, we are able to design an ESO-based stabilising output-feedback and prove the practical mean square stability for the closed-loop system with constant gain ESO and the asymptotic mean square stability with time-varying gain ESO, respectively. Some numerical simulations are presented to demonstrate the effectiveness of the proposed output-feedback control scheme. 相似文献