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   2401篇
  免费   39篇
电工技术   178篇
化学工业   424篇
金属工艺   35篇
机械仪表   44篇
建筑科学   30篇
矿业工程   2篇
能源动力   62篇
轻工业   156篇
水利工程   3篇
石油天然气   2篇
无线电   469篇
一般工业技术   381篇
冶金工业   465篇
原子能技术   55篇
自动化技术   134篇
  2023年   7篇
  2022年   13篇
  2021年   30篇
  2020年   10篇
  2019年   20篇
  2018年   16篇
  2017年   8篇
  2016年   30篇
  2015年   33篇
  2014年   28篇
  2013年   85篇
  2012年   68篇
  2011年   83篇
  2010年   59篇
  2009年   74篇
  2008年   102篇
  2007年   83篇
  2006年   70篇
  2005年   59篇
  2004年   72篇
  2003年   103篇
  2002年   70篇
  2001年   70篇
  2000年   51篇
  1999年   68篇
  1998年   197篇
  1997年   133篇
  1996年   104篇
  1995年   92篇
  1994年   54篇
  1993年   63篇
  1992年   38篇
  1991年   41篇
  1990年   34篇
  1989年   43篇
  1988年   42篇
  1987年   22篇
  1986年   34篇
  1985年   39篇
  1984年   29篇
  1983年   23篇
  1982年   18篇
  1981年   28篇
  1980年   16篇
  1979年   12篇
  1978年   13篇
  1977年   12篇
  1976年   20篇
  1974年   5篇
  1973年   5篇
排序方式: 共有2440条查询结果,搜索用时 31 毫秒
1.
The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power.  相似文献   
2.
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis.  相似文献   
3.
4.
Gas effusion spectra of fullerenes are studied. Three peaks of toluene are found in gas effusion spectra dp/dT-T. Two peaks of oxygen are found in gas effusion spectra dN/dt-T of samples kept in the air after annealing to avoid the toluene. These phenomena confirmed to be reversible are discussed by treating fullerenes as intercalated materials.  相似文献   
5.
a-Si alloy three-stacked solar cells have been studied to improve the stabilized efficiency of a-Si: H based solar cells. Based on the analysis by the individual characterization method of the component cells in stacked type cells, the a-Si :H middle cell was replaced with an a-SiGe :H cell. Furthermore, the optical confinement technology was improved to obtain a high-output current with thin i-layer thickness in the a-SiGe :H bottom cell. By this device design, the initial conversion efficiency was improved up to 12.4% and more than a 10% stabilized efficiency was obtained in a-SiC :H/a-SiGe :H/a-SiGe :H three-stacked cells. These cell characteristics were confirmed by measurements at the JQA Organization (the former JMI Institute).  相似文献   
6.
A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitatite disaturated species of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC. The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chroamtograms obtained by RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responsed in the same degree for different, authentic standards of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis among the molecular species containing disaturated species.  相似文献   
7.
8.
The mechanical, electrical and thermal properties of alkaline earth metal (Mg, Ca and Sr)-doped LaCrO3 have been examined as separators in planar-type high-temperature solid oxide fuel cells. The maximum three-point bending strength at 1000°C in air was measured and found to be 186 MPa for LaCr0.9Mg0.1O3, 36 MPa for La0.9Ca0.1CrO3 and 77 MPa for La0.9Sr0.1CrO3. The La0.8Sr0.2CrO3 separator placed in both an oxidizing and a reducing environment at 1000°C showed almost the same electrical conductivities of the H2 atmosphere, and the conductivity was independent of sample thickness in the range 0.5–3.0 mm. For all the doped LaCrO3 perovskites, a difference between the thermal expansion behaviours of air and the H2 atmosphere was observed. In particular, the thermal expansion slope for the first heating cycle under the H2 atmosphere showed a marked change. The volume changes were due to the formation of oxygen defects in the perovskite structure. This revised version was published online in November 2006 with corrections to the Cover Date.  相似文献   
9.
Yamamoto  M. Itoh  K. 《Electronics letters》1997,33(6):441-443
In a slot-coupled microstrip antenna with a triplate line feed, the parallel-plate mode is excited by the slot, resulting in a decrease of radiation efficiency. The authors present a technique for suppressing the parallel-plate mode in this type of the antenna. Measured results confirm the effective performance of the proposed method  相似文献   
10.
A micromachined lead zirconate titanate (PZT) force sensor for scanning force microscope (SFM) is conceptualized by its piezoelectricity. The fabrication procedure is interpreted, and mechanical characteristics of the micromachined PZT force sensors with various lengths are studied in this paper. A compact SFM is constructed by using the piezoelectric PZT sensor. A very clear image is taken by this SFM. The current study of the micromachined PZT force sensor can be considered as a breakthrough of design of SFM as well as a good example of integrated piezoelectric microdevices  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