全文获取类型
收费全文 | 24938篇 |
免费 | 3677篇 |
国内免费 | 600篇 |
专业分类
电工技术 | 9587篇 |
综合类 | 1835篇 |
化学工业 | 931篇 |
金属工艺 | 520篇 |
机械仪表 | 1711篇 |
建筑科学 | 2149篇 |
矿业工程 | 291篇 |
能源动力 | 6759篇 |
轻工业 | 98篇 |
水利工程 | 1403篇 |
石油天然气 | 426篇 |
武器工业 | 223篇 |
无线电 | 565篇 |
一般工业技术 | 1236篇 |
冶金工业 | 337篇 |
原子能技术 | 92篇 |
自动化技术 | 1052篇 |
出版年
2024年 | 87篇 |
2023年 | 462篇 |
2022年 | 967篇 |
2021年 | 929篇 |
2020年 | 1001篇 |
2019年 | 795篇 |
2018年 | 717篇 |
2017年 | 880篇 |
2016年 | 1099篇 |
2015年 | 1233篇 |
2014年 | 2161篇 |
2013年 | 1540篇 |
2012年 | 2251篇 |
2011年 | 2452篇 |
2010年 | 1555篇 |
2009年 | 1565篇 |
2008年 | 1323篇 |
2007年 | 1476篇 |
2006年 | 1301篇 |
2005年 | 922篇 |
2004年 | 759篇 |
2003年 | 703篇 |
2002年 | 546篇 |
2001年 | 511篇 |
2000年 | 431篇 |
1999年 | 327篇 |
1998年 | 204篇 |
1997年 | 175篇 |
1996年 | 160篇 |
1995年 | 131篇 |
1994年 | 99篇 |
1993年 | 96篇 |
1992年 | 64篇 |
1991年 | 61篇 |
1990年 | 51篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 26篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
《International Journal of Hydrogen Energy》2022,47(21):11177-11189
Chemical looping reforming (CLR) is an efficient technology to convert hydrocarbon fuels into CO2 and H2 using metal oxide based oxygen carriers. The novelty of the present study is to utilize electronic waste such as printed circuit board (PCB) to generate high quality syngas and metallic components for the CLR process. A portion of the syngas generated during e-waste pyrolysis is used with coal and polypropylene for effective combustion. A techno-economic analysis is performed for the production of hydrogen and electricity in the CLR method. The levelized costs for electricity (LCOE), hydrogen (LCOH), syngas (LCOS), and metal (LCOM) production using e-wastes are estimated as 92.28 $/MWh, 3.67 $/kg, 0.0034 $/kWh, and 24.32 $/ton, respectively. The LCOH is found to be the least of 2.90 $/kg under the co-feed conditions of PCB syngas-PP. The integration of the e-waste based CLR with a steam turbine system achieved a net efficiency of 50%. 相似文献
82.
83.
84.
85.
86.
In most of the existing studies, the frequency response in the variable speed wind turbines (VSWTs) is simply realized by changing the torque set-point via appropriate inputs such as frequency deviations signal. However, effective dynamics and systematic process design have not been comprehensively discussed yet. Accordingly, this paper proposes a proportional-derivative frequency controller and investigates its performance in a wind farm consisting of several VSWTs. A band-pass filter is deployed before the proposed controller to avoid responding to either steady state frequency deviations or high rate of change of frequency. To design the controller, the frequency model of the wind farm is first characterized. The proposed controller is then designed based on the obtained open loop system. The stability region associated with the controller parameters is analytically determined by decomposing the closed-loop system's characteristic polynomial into the odd and even parts. The performance of the proposed controller is evaluated through extensive simulations in MATLAB/Simulink environment in a power system comprising a high penetration of VSWTs equipped with the proposed controller. Finally, based on the obtained feasible area and appropriate objective function, the optimal values associated with the controller parameters are determined using the genetic algorithm (GA). 相似文献
87.
随着风能资源的广泛应用,机组组合问题求解愈显复杂。以减少煤耗费用提高系统经济性为目标,提出一种采用遗传萤火虫算法求解含风电电力系统机组组合问题的新方法。引入遗传算法双矩阵通路判断及约束修复策略,提高了初始解生成质量及产生速度;再利用萤火虫算法求解连续负荷经济优化分配,给出自适应交叉概率,从而提高了算法的收敛速度。应用所提算法对经典10机系统优化仿真表明,与其他算法相比,该方法能合理安排机组组合,提高系统供电的经济性,具有较好的实用价值。 相似文献
88.
Weighted Self-Adaptive Threshold Wavelets for Interpolation Point Selection Used in Interconnect MOR
超高膨胀比涡轮噪声控制技术研究
赵辛午,黄洪雁
(哈尔滨工业大学 能源科学与工程学院,哈尔滨 150001)
中文说明:
气动噪声控制是提高鱼雷隐身性能的关键技术之一。本文讨论了局部进气的超高膨胀比涡轮气动噪声产生机理。相邻喷嘴与流道之间形成的三角形非出气区域引起的尾迹、圆周局部进气设计引起的不稳定性、喷嘴和转子之间区域形成的复杂激波系是这类涡轮气动噪声产生的三种主要来源。因此,本文提出了两种气动噪声控制方法,增加转静子之间的轴向间距,喷嘴下俯、双侧修型和尾缘吹气。数值模拟结果表明:在对原涡轮气动性能影响不大的情况下,优化后涡轮的气动噪声下降10 dB以上。
关键词:超高膨胀比涡轮、气动噪声、流动特性、优化
相似文献89.
为分析预弯处理对10 MW级风力机叶片气动特性的影响,以DTU 10 MW风力机为例,采用CFD数值模拟方法,研究均匀来流不同风速下风力机的输出功率,并与BEM计算结果进行对比。同时,对比分析直叶片和预弯叶片风力机的功率特性、沿展向出力分布、沿展向不同截面翼型的流动特性。研究结果表明,直叶片各截面翼型的压力差较预弯叶片的大,做功能力较强。预弯通过对叶片的三维流动产生扰动,进而影响风力机的输出功率,且主要体现在叶片展向70%~90%的位置。研究成果可为风力机叶片气动性能的设计与优化提供参考。 相似文献
90.
A technoeconomic analysis and optimization of wind turbine size and layout are performed using WAsP software. A case study of a 100‐MW wind farm located in Egypt is considered. Wind atlas for Egypt was used as the input data of the WAsP software. Two turbine models of powers 52 and 80 MW are considered for this project. The wind turbine size and distributions are selected based on the technoeconomic optimization, namely minimum wake effect, maximum annual energy production (AEP) rate, optimum cash flow, and payback period. The future worth method is adopted in economic comparison between the two alternatives, and the cash flow diagram provided the payback period and future worth after the lifetime of the plant. The results showed that (1) the AEP dramatically decreases for a wind farm area less than 15 km2; (2) the turbine spacing, spacing‐to‐diameter ratio, and the setback distances decrease and the wind turbine density and wake losses increase with decreasing the wind turbines size; (3) the total net AEP using G52 is lower than that of using G80 by about 16%; (4) the technoeconomic analysis recommended using G80 as it has higher profit than those of G52 by about $20 million. 相似文献