全文获取类型
收费全文 | 15742篇 |
免费 | 2177篇 |
国内免费 | 786篇 |
专业分类
电工技术 | 7971篇 |
综合类 | 982篇 |
化学工业 | 568篇 |
金属工艺 | 245篇 |
机械仪表 | 845篇 |
建筑科学 | 186篇 |
矿业工程 | 296篇 |
能源动力 | 546篇 |
轻工业 | 98篇 |
水利工程 | 83篇 |
石油天然气 | 105篇 |
武器工业 | 59篇 |
无线电 | 3101篇 |
一般工业技术 | 422篇 |
冶金工业 | 1894篇 |
原子能技术 | 130篇 |
自动化技术 | 1174篇 |
出版年
2024年 | 24篇 |
2023年 | 233篇 |
2022年 | 382篇 |
2021年 | 477篇 |
2020年 | 543篇 |
2019年 | 414篇 |
2018年 | 368篇 |
2017年 | 647篇 |
2016年 | 701篇 |
2015年 | 746篇 |
2014年 | 1090篇 |
2013年 | 836篇 |
2012年 | 1250篇 |
2011年 | 1381篇 |
2010年 | 1025篇 |
2009年 | 945篇 |
2008年 | 1019篇 |
2007年 | 1186篇 |
2006年 | 1141篇 |
2005年 | 870篇 |
2004年 | 662篇 |
2003年 | 547篇 |
2002年 | 450篇 |
2001年 | 385篇 |
2000年 | 350篇 |
1999年 | 237篇 |
1998年 | 185篇 |
1997年 | 125篇 |
1996年 | 112篇 |
1995年 | 93篇 |
1994年 | 74篇 |
1993年 | 59篇 |
1992年 | 55篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
现有文献针对计及转子变流器(RSC)控制的双馈感应风电机组(DFIG)定子短路电流解析表达,将定子磁链当作一阶直流衰减分量或忽略功率外环控制。基于DFIG电压、磁链和RSC控制方程,得到定子电流关于定子电压和定子功率的传递函数,提出定子电流的精确解析表达式。基于RSC内、外环PI参数关系,推导直流分量衰减时间常数和角频率关于PI参数的表达式。分析了RSC内外环PI参数对定子电流直流衰减分量的影响。仿真结果验证了解析表达式的准确性,为PI参数选取和保护装置测量、整定提供依据。 相似文献
3.
Sanjeev Kumar Pandey S. L. Patil Praveen V. Pol S. B. Phadke 《International Journal of Electronics》2020,107(10):1682-1703
ABSTRACT In this paper, two control schemes for boost converters affected by uncertainties in input voltage and load are proposed. The boost converter dynamics is redefined in terms of new state variables to facilitate the use of a disturbance observer that can estimate matched and unmatched disturbances. A sliding surface, which is new in the context of boost converters, is proposed to enable tracking and regulation of output voltage without requiring measurement of input voltage and load current. The stability of the overall system including the disturbance observer, the sliding variable and the output is proved. The performance of the schemes is assessed for regulation of output voltage and tracking of reference voltage by simulation as well as experimentation in which various types of uncertainties and various types of reference voltages are considered. 相似文献
4.
为了实现太赫兹信号的可调谐滤波,设计了一种基于柔性材料的太赫兹可调谐滤波器。通过扭曲特氟龙(Teflon)波导形成环型谐振器,实现了160~200 GHz频段的带阻滤波功能。改变谐振腔长可实现自由频谱范围(FSR)和滤波频点的调谐,实验测试了自由频谱范围在1.9 GHz和2.8 GHz间切换以及相应的滤波特性。研究表明,谐振腔长一定时,改变弯曲半径可实现滤波阻带抑制度的调节,柔性材料太赫兹环型谐振器可用于可调谐滤波,且具有较高的自由度。 相似文献
5.
This paper introduces a 9-bit time-based capacitance-to-digital converter (T-CDC). This T-CDC adopts a new design methodology for parasitic cancellation with a simple calibration technique. In T-CDCs, the input sensor capacitance is first converted into a delay pulse using a capacitance-to-time converter (CTC) circuit; then this delay signal is converted into a digital code through a time-to-digital converter (TDC) circuit. A prototype of the proposed T-CDC is implemented in UMC 0.13 μm CMOS technology. This T-CDC consumes 8.42 μW and achieves a maximum SNR of 45.14 dB with a conversion time of 1 μs that corresponds to a figure of merit (FoM) of 16.4 fJ/Conv. 相似文献
6.
增大源距是提高随钻电磁波电阻率测井仪器探测深度的有效方法,但是接收信号随源距增大严重衰减。本文将谐振原理引入随钻电磁波电阻率测井,采用双发单收谐振型线圈系结构,提高接收线圈的电压幅度。实验室通常采用刻度环模拟地层电导率,开展仪器响应特性研究。双发单收谐振型线圈系的刻度方法与传统的开路线圈系结构完全不同。本文基于DOLL几何因子理论,对双发单收谐振型线圈系刻度环参数选择方法进行研究,发现参数选择应该兼顾相对平稳度与刻度环电阻分辨度,以减小测量误差。实验比较了均匀地层中接收线圈开路和谐振响应特性,表明谐振方法只增大了接收响应的幅值而没有改变幅度比,验证了刻度环参数选择方法的正确性以及谐振方法的正确性。 相似文献
7.
Soheil Khosrogorji Sepehr Soori Hossein Torkaman 《International Journal of Circuit Theory and Applications》2019,47(10):1645-1663
In this paper, a new design procedure for LLC converter has been introduced. In fact, this method is a computer-based design algorithm based on a numerical technique. In the process of designing, the value of the resonant element is obtained by solving the LLC converter fundamental equation. This converter will be controlled by using state feedback, such as output voltage variable. As a matter of fact, in a control system, the change of output voltage (because of load variation) will affect the switching frequency, so the output voltage will be tuned. In the designing process, the fundamental equations of LLC converter are obtained, and the value of the resonant elements is calculated. Also, a comparison analysis is carried out between the proposed and typical methods. The simulation is done to investigate the validity of the proposed method. Moreover, a prototype is manufactured, and the experimental test is done to evaluate its applicability. 相似文献
8.
高速磁悬浮涡轮分子泵(Turbo Molecular Pump, TMP)因其高能量密度、微振动、无需润滑等优点被广泛应用于工业领域,但外部电源失效时,高速转子跌落后与保护轴承产生剧烈撞击和摩擦,将给系统带来致命损害。针对以上问题,提出一种基于平均功率平衡法的电力失效补偿控制(Power Failure Compensation Control, PFCC)方法。首先,设计电机能量回馈电路;其次,对Buck-Boost变换器进行数学建模,设计一种双环非线性控制器,其中电流内环使用滑模控制,电压外环使用平均功率平衡控制(Average Power Balance Control, APBC),并利用Lyapunov函数推导出系统的稳定性条件;最后,通过搭建磁悬浮分子泵PFCC实验平台,对所提出的方法进行实验验证。结果表明:本文所提出的方法具有快速响应和输出鲁棒性,磁悬浮转子由额定转速21000 r/min降至3900 r/min时跌落,电机能量转化效率为96.6%,提高了磁轴承系统的安全性。 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(2):1241-1255
The realization of dc-dc converters performs a vital function in exploiting renewable energy sources such as solar photovoltaic (PV) and fuel cell applications. This paper demonstrates a single-switch unidirectional buck-boost dc-dc converter for continuous power flow control, excluding the hybrid switched-capacitor. The proposed converter utilizes a limited number of passive components, only four diodes and three inductors required, in addition to six capacitors. The converter can operate at a wide input voltage range with continues input current. The converter has experimented under real-time conditions with 660 W PV system. The obtained efficiency ranges from 93% to 98%. Furthermore, the converter has interfaced with 550 W fuel cell operated under different fuel pressure. The realized efficiency ranges from 91% to 97%. The maximum measured inductance current ripple is limited to under 0.70 A in both scenarios, whereas 0.16 V is the maximum output voltage ripple. 相似文献
10.
《International Journal of Hydrogen Energy》2021,46(73):36398-36414
In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS. 相似文献