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   155090篇
  免费   15280篇
  国内免费   10256篇
电工技术   14107篇
技术理论   3篇
综合类   11180篇
化学工业   42547篇
金属工艺   11192篇
机械仪表   5058篇
建筑科学   6123篇
矿业工程   3175篇
能源动力   6529篇
轻工业   9572篇
水利工程   2535篇
石油天然气   7450篇
武器工业   1090篇
无线电   14462篇
一般工业技术   19601篇
冶金工业   6688篇
原子能技术   2498篇
自动化技术   16816篇
  2024年   604篇
  2023年   2672篇
  2022年   5226篇
  2021年   6005篇
  2020年   5097篇
  2019年   4666篇
  2018年   4304篇
  2017年   5178篇
  2016年   5548篇
  2015年   5635篇
  2014年   8115篇
  2013年   9328篇
  2012年   10161篇
  2011年   12209篇
  2010年   9272篇
  2009年   10515篇
  2008年   9289篇
  2007年   10673篇
  2006年   9719篇
  2005年   7675篇
  2004年   6605篇
  2003年   5691篇
  2002年   4623篇
  2001年   3652篇
  2000年   3234篇
  1999年   2641篇
  1998年   2140篇
  1997年   1628篇
  1996年   1523篇
  1995年   1301篇
  1994年   1254篇
  1993年   923篇
  1992年   726篇
  1991年   593篇
  1990年   492篇
  1989年   396篇
  1988年   264篇
  1987年   187篇
  1986年   160篇
  1985年   132篇
  1984年   98篇
  1983年   66篇
  1982年   85篇
  1981年   61篇
  1980年   55篇
  1979年   42篇
  1977年   23篇
  1976年   20篇
  1975年   20篇
  1951年   31篇
排序方式: 共有10000条查询结果,搜索用时 153 毫秒
71.
吴正立  严利人 《微电子学》1996,26(5):339-341
为了提高E^2PROM中N管源漏穿通电压,用实验的方法对制造工艺进行了研究。结果表明,高能量注入是提高VPT的有效手段,但受到pn结击穿的限制,只适用于低区短沟N管;DDD工艺大幅度高VPT,但pn结击穿电压低于20V,不能应用于高压MOS管;采用适量的防穿通注入和适当增大沟道长度为最理想的工艺途径。  相似文献   
72.
Electric power systems are expanding in size and complexity, and the requirement for the energy management system (EMS) is becoming more important. In this computer control system, a single control computer is used mainly as the primary computer and its software is very complicated because of its hugh number of small, quick tasks to obtain high response speed. Therefore, much effort is needed to develop and modify the programs, and the responsiveness of this centralized architecture varies greatly when many faults occur in the power system. This paper describes a new distributed architecture for the EMS. Distributed processors execute the functions cooperatively with periodic access to the common bulletin board database in which information about the power system exist. This architecture facilitates the software development and maintenance, and it also enhances the performance by the parallel processing of the distributed functions.  相似文献   
73.
The residual intergranular strains in textured Zircaloy-2 plate samples induced by cooling from 823 K to ambient temperatures, by cold-rolling by 1.5% and 25% and by deforming in tension by 1.5% were measured by neutron diffraction. The strong rolling texture, which gives rise to two ideal orientations, permitted the interpretation of much of the data in terms of strain tensors for the two orientations. The experimental results were compared with calculations based on the elasto-plastic self-consistent model with no adjustable parameters. Close agreement was obtained for samples in the as-cooled state and deformation in tension by 1.5% but the agreement is less satisfactory for cold-rolling.  相似文献   
74.
A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380  相似文献   
75.
When a fault occurs on transmission or distribution systems due to lightning or overvoltage, often an arc discharge occurs at the fault point. The arc discharge, which is caused by a fault current, has a high current, high temperature, strong light emission, etc., thus it sometimes causes heavy damages to electric power equipment. The arc discharge is influenced by the conditions around the arcs, i.e., gas, insulation materials, gap length, weather, etc. Also, the arc voltage along the arc column indicates the characteristics of the arc. If the voltage waveforms of the arcs caused by the fault on transmission or distribution systems are classified, it is possible to find the location and the equipment where the fault occurred. In this paper, the arc voltage data in 6-kV class XLPE cables and 6-kV class overhead lines are analyzed and an artificial neural network method is applied to classify the arc voltage waveforms. The results obtained from the six artificial neural networks developed show that the artificial neural network method is effective for classification of arc voltage waveforms if adequate input parameters are selected.  相似文献   
76.
Solid-liquid phase equilibria of the benzene + 2-methyl-2-propanol system have been investigated at temperatures from 278 to 323 K and pressures up to 300 MPa using a high-pressure optical vessel. The uncertainties of the measurements of temperature, pressure and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. The freezing pressure at a constant composition increases monotonously with pressure. The eutectic point shifts to a higher temperature and benzene-rich composition with increasing pressure. In order to describe the pressure-temperature-composition relation of high-pressure solid-liquid phase equilibria, a new simple equation has been proposed as follows:
  相似文献   
77.
本文介绍用堆中子活化分析法测定人群头发中I、Br、Mg、Mn、Cu、Na、V、Cl、Al、Ca、S等11种元素。研究人发中元素分布特征、相关性特征、性别年令分布特征。方法学中还从法庭科学应用角度介绍同一性识别中差异率和重合几率的双判据方法。  相似文献   
78.
基于J2EE平台的供应链管理系统研究   总被引:2,自引:0,他引:2  
介绍了供应链管理的基本原理和实现技术,从平台基础、移植性、扩展性等多个角度对J2EE平台进行了相应的分析,提出了一个基于J2EE平台的供应链管理系统框架,并从系统结构、系统功能模块等方面进行了说明。  相似文献   
79.
研究了一种制造低电电压氧化锌压敏电阻器的方法。在基本成分的基础上适当加入二氧化钛可降低梯度电压(V1mA/mm),适量掺硼和改进热处理工艺可减小元件的漏电流和提高其稳定性。  相似文献   
80.
1 INTRODUCTIONTheorthorhombicalloysareofgreattech nolog icalinterestinhightemperatureapplicationssincetheyhaveagoodbalanceamongst  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