首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8604篇
  免费   1421篇
  国内免费   215篇
电工技术   5349篇
综合类   739篇
化学工业   132篇
金属工艺   219篇
机械仪表   650篇
建筑科学   162篇
矿业工程   156篇
能源动力   199篇
轻工业   108篇
水利工程   85篇
石油天然气   79篇
武器工业   80篇
无线电   722篇
一般工业技术   234篇
冶金工业   133篇
原子能技术   10篇
自动化技术   1183篇
  2025年   112篇
  2024年   333篇
  2023年   282篇
  2022年   340篇
  2021年   418篇
  2020年   465篇
  2019年   363篇
  2018年   287篇
  2017年   429篇
  2016年   360篇
  2015年   379篇
  2014年   525篇
  2013年   437篇
  2012年   612篇
  2011年   666篇
  2010年   452篇
  2009年   453篇
  2008年   420篇
  2007年   548篇
  2006年   474篇
  2005年   387篇
  2004年   259篇
  2003年   233篇
  2002年   180篇
  2001年   148篇
  2000年   164篇
  1999年   114篇
  1998年   73篇
  1997年   68篇
  1996年   68篇
  1995年   51篇
  1994年   32篇
  1993年   32篇
  1992年   18篇
  1991年   11篇
  1990年   13篇
  1989年   11篇
  1988年   7篇
  1987年   9篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1980年   1篇
  1978年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Recently, a demand for small-capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines. It is desired that the structure of small-capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled. This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.  相似文献   
2.
This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033  相似文献   
3.
Brushless three-phase synchronous motor involving a rotating ac exciter on the same shaft as the motor and with the windings linked through a shaft-mounted rectifier is widely used as medium and large capacity machines. However, the motor needs to fit with damping windings for self-starting outside of the field winding in the rotor and needs to equip discharge resistance with complex electronic device to dispose of electromagnetic force induced in the field winding at starting. Therefore, the rotor structure is very complex, and there are disadvantages, especially for the robust and highly reliable motor that is desired. To solve the problem found in traditional motors, the authors proposed a brushless three-phase synchronous induction motor with two stators and one wound rotor. This problem is solved because the proposed motor is of two-stators structure: the rotor winding operates as a secondary winding of induction motor at starting and as the field winding at synchronous operation. The motor can self-start as a wound-rotor induction motor without external secondary resistance. Therefore, discharge resistance is not necessary; the starting equipment is very simple and the rotor structure is robust. It is possible to start with high torque. In this paper, the basic constitution of the proposed motor and the principles of operation are described in detail. The experimental results at starting and pulling into synchronism are shown for confirming the principles of operation and the experimental and numerical results of the starting characteristics. The load ones and the generating ones are shown and then the practical use of the proposed motor is confirmed.  相似文献   
4.
To study cell-cycle-related variations in wall permeability of Saccharomyces cerevisiae, two approaches were used. First, an asynchronous culture was fractionated by centrifugal elutriation into subpopulations containing cells of increasing size. The subpopulations represented different stages of the cell cycle as judged by light microscopy. Cell wall porosity increased when these subpopulations became enriched with budded cells. Secondly, synchronous cultures were obtained by releasing MATa cells from alpha-factor induced G1-arrest. These cultures grew synchronously for at least two generations. The cell wall porosity increased sharply in these cultures, shortly before buds became visible and was maximal during the initial stages of bud growth. It decreased in cells which had completed nuclear migration and before abscission of the bud had occurred. The porosity reached its lowest value during abscission and in unbudded cells. We examined the incorporation of mannoproteins into the wall during the cell cycle. SDS-extractable mannoproteins were incorporated continuously. However, the incorporation of glucanase-extractable mannoproteins, which are known to affect cell wall porosity, showed cyclic oscillations and reached its maximum after nuclear migration. This coincided with a rapid decrease in cell wall porosity, indicating that glucanase-extractable mannoproteins might contribute to this decrease.  相似文献   
5.
This paper presents a novel on‐line parameter identification method for sensorless control of Synchronous Reluctance Motors (SynRMs). Although conventional sensorless control methods based on mathematical models usually need some complex measurements of motor parameters in advance, the proposed identification method does not require them and can be realized on‐line. The proposed method identifies motor parameters under sensorless control, so rotor position and velocity cannot be used to identify these parameters. However, the proposed method does not need rotor position and velocity, and identified parameters are not affected by these estimation errors. The sensorless control using identified motor parameters is realized, and the effectiveness of the proposed method is verified by experimental results. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 62–69, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20258  相似文献   
6.
永磁同步伺服电动机的动态参数   总被引:2,自引:0,他引:2  
莫会成 《微电机》2006,39(2):3-5,13
动态参数是影响伺服电动机动态性能最主要的因素之一.动态参数的高低直接决定伺服电动机动态及稳态性能的好坏.对传统的伺服电动机而言,几个主要的动态参数都有较清晰的定义和概念,长期以来在工程实践中广泛使用.但对正弦波驱动的永磁伺服电动机来说,电机的力矩常数Kt、反电势常数Ke、电气时间常数τe、机械时间常数τm和阻尼因数D等都有了新的变化,实践中常引起误解和混淆.文中主要分析永磁同步伺服电动机几个动态参数的含义以及和传统参数之间的差异,并从控制系统的要求出发,对几个最基本的动态参数和参数之间的相互关系进行分析,得出了一些实用的结论.  相似文献   
7.
张耀安 《微特电机》2006,34(1):5-7,33
介绍了稀土永磁低速同步电动机原理结构特点,着重论述该电机在制造中的关键技术和研究。  相似文献   
8.
This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.  相似文献   
9.
This paper proposes a new method for properly estimating the rotor initial phase (i.e., the position) of the newly emerging self‐excited hybrid‐field synchronous motors (SelE‐HFSMs), which have the rotor held by both a permanent magnet and a diode‐shorted held winding. The proposed method injects a spatially rotating high‐frequency voltage and detects the rotor phase directly by evaluating the norm of the associated current. The method is very simple, but has a high degree of usability. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(3): 49–58, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.21027  相似文献   
10.
牵引控制系统是高速磁悬浮列车子系统之一。为降低成本、提高稳定性,交流电机无机械传感器调速控制一直是电工技术领域的研究热点。对滑模变结构控制无位置传感器技术控制进行了仿真研究和实验验证,该算法应用于长定子直线同步电机(Long Stator Linear Synchronous Motor,简称LSLSM)无位置传感器转子磁场定向控制时低速性能不佳,最好采用低速有位置传感器、中高速无位置传感器混合控制的控制方式。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号