全文获取类型
收费全文 | 44717篇 |
免费 | 6791篇 |
国内免费 | 3505篇 |
专业分类
电工技术 | 7436篇 |
技术理论 | 8篇 |
综合类 | 4605篇 |
化学工业 | 4060篇 |
金属工艺 | 877篇 |
机械仪表 | 2561篇 |
建筑科学 | 4067篇 |
矿业工程 | 1223篇 |
能源动力 | 1497篇 |
轻工业 | 1237篇 |
水利工程 | 2234篇 |
石油天然气 | 668篇 |
武器工业 | 634篇 |
无线电 | 9307篇 |
一般工业技术 | 3596篇 |
冶金工业 | 728篇 |
原子能技术 | 314篇 |
自动化技术 | 9961篇 |
出版年
2024年 | 127篇 |
2023年 | 796篇 |
2022年 | 1183篇 |
2021年 | 1540篇 |
2020年 | 1789篇 |
2019年 | 1490篇 |
2018年 | 1407篇 |
2017年 | 1823篇 |
2016年 | 1935篇 |
2015年 | 2098篇 |
2014年 | 3197篇 |
2013年 | 3025篇 |
2012年 | 3679篇 |
2011年 | 4009篇 |
2010年 | 3101篇 |
2009年 | 3038篇 |
2008年 | 3041篇 |
2007年 | 3445篇 |
2006年 | 2982篇 |
2005年 | 2322篇 |
2004年 | 1792篇 |
2003年 | 1537篇 |
2002年 | 1123篇 |
2001年 | 987篇 |
2000年 | 735篇 |
1999年 | 585篇 |
1998年 | 415篇 |
1997年 | 363篇 |
1996年 | 301篇 |
1995年 | 260篇 |
1994年 | 197篇 |
1993年 | 162篇 |
1992年 | 117篇 |
1991年 | 97篇 |
1990年 | 61篇 |
1989年 | 71篇 |
1988年 | 39篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1965年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mengru Liu Weihai Zhang Limin Ma 《International Journal of Adaptive Control and Signal Processing》2022,36(1):69-87
The article investigates the finite-time adaptive fuzzy control for a class of nonlinear systems with output constraint and input dead-zone. First, by skillfully combining the barrier Lyapunov function, backstepping design method, and finite-time control theory, a novel adaptive state-feedback tracking controller is constructed, and the output constraint of the nonlinear system is not violated. Second, the fuzzy logic system is used to approximate unknown function in the nonlinear system. Third, the finite-time command filter is introduced to avoid the problem of “complexity explosion” caused by repeated differentiations of the virtual control signal in conventional backstepping control schemes. Meanwhile, a new saturation function is added in the compensating signal for filter error to improve control accuracy. Finally, based on Lyapunov stability analysis, all the signals of the closed-loop are proved to be semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood region of the origin in a finite time. A simulation example is presented to demonstrate the effectiveness for the proposed control scheme. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(5):2926-2935
Development of highly efficient and cheap electrocatalysts towards the hydrogen evolution reaction (HER) is of great importance for electrochemical water splitting. Herein, hybrid Cu/NiMo-P nanowires on the copper foam were successfully fabricated via a simple two-step method. The hierarchically structured Cu/NiMo-P exhibits large surface areas and rapid electron transfer ability, leading to enhanced catalytic activity. The as-prepared Cu/NiMo-P electrodes need overpotentials of 34 mV and 130 mV to obtain 10 mA cm?2 for HER in acidic and alkaline solutions, respectively. Density functional theory (DFT) calculations reveal that the Cu/NiMo-P hybrid has a more thermo-neutral hydrogen adsorption free energy and enhanced charge transfer ability as well. 相似文献
3.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
4.
5.
6.
《Advanced Powder Technology》2022,33(8):103602
To operate a bag filter continuously, pulse-jet cleaning of dust particles from the filter medium is commonly required, and the pulse-jet pressure significantly affects the filter performance. In this study, the accumulation structure of residual dust particles inside and on the surface of a filter medium at different pulse-jet pressures was investigated by constructing a simple model, and the influence of the dust structure on the filter performance was clarified. Using a simple model, we determined the effective ratio of filtration area β, which represents the ratio of the filterable area to the total filtration area, the true resistance coefficient due to the primary dust layer ζp’ thinly deposited on the filter surface, and the true resistance coefficient inside the filter media itself ζf’. The effective ratio of filtration area β decreased with operation time for all pulse-jet pressures; however, it maintained a high value when the pulse-jet pressure was high. The validity of β analyzed by the model was verified using two different methods, and the results showed good agreement, indicating that the model is effective in identifying real conditions. The true resistance coefficient due to the primary dust layer ζp’ decreased as the pulse-jet pressure increased; however, the true resistance coefficient inside the filter media itself ζf’ was the highest at 0.5 MPa. In addition, the dust collection efficiency was different at each pulse-jet pressure, which was considered to be caused by the difference in the dust particle accumulation structure. 相似文献
7.
8.
9.
10.
CO2捕集作为温室气体排放控制的有效手段已成为重要研究课题。作为新兴捕集技术之一,低温CO2捕集因产品纯度高、无附加污染等优势受到关注。然而,该技术能耗和捕集率对于气体中CO2浓度十分敏感,对于高CO2浓度气体可获得较高的CO2捕集率和较低能耗水平。基于此,本文提出了耦合膜分离的新型CO2低温捕集系统,通过膜材料选择渗透性实现待捕集气体CO2浓度主动调控,并在最优浓度下进行CO2低温捕集。首先基于不同传统低温捕集系统特点,对比分析了不同耦合系统模式,从而确定了最优耦合系统结构。针对最优耦合系统进行了运行参数优化,并分别基于实现系统捕集能耗最低与捕集率最高的目标,获得了膜渗透侧CO2浓度与进气CO2浓度间的关系式,为该耦合系统中膜组件选型提供指导。研究表明,本文提出的耦合系统捕集能耗为1.92MJ/kgCO2,相比于传统单一低温系统捕集能耗可降低16.5%。 相似文献