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   455602篇
  免费   43901篇
  国内免费   19542篇
电工技术   25435篇
技术理论   46篇
综合类   32051篇
化学工业   83835篇
金属工艺   24658篇
机械仪表   27213篇
建筑科学   33838篇
矿业工程   13255篇
能源动力   12272篇
轻工业   36169篇
水利工程   8430篇
石油天然气   25840篇
武器工业   3312篇
无线电   51977篇
一般工业技术   55042篇
冶金工业   21839篇
原子能技术   4502篇
自动化技术   59331篇
  2024年   1651篇
  2023年   6144篇
  2022年   11104篇
  2021年   15775篇
  2020年   12987篇
  2019年   12246篇
  2018年   13697篇
  2017年   15384篇
  2016年   14869篇
  2015年   19389篇
  2014年   23687篇
  2013年   28897篇
  2012年   29256篇
  2011年   31871篇
  2010年   29034篇
  2009年   27548篇
  2008年   26880篇
  2007年   25695篇
  2006年   25675篇
  2005年   22405篇
  2004年   16164篇
  2003年   14726篇
  2002年   14540篇
  2001年   12889篇
  2000年   11673篇
  1999年   11129篇
  1998年   8029篇
  1997年   6846篇
  1996年   6410篇
  1995年   5324篇
  1994年   4284篇
  1993年   2921篇
  1992年   2322篇
  1991年   1754篇
  1990年   1388篇
  1989年   1097篇
  1988年   930篇
  1987年   594篇
  1986年   445篇
  1985年   312篇
  1984年   245篇
  1983年   196篇
  1982年   146篇
  1981年   96篇
  1980年   115篇
  1979年   57篇
  1978年   25篇
  1977年   35篇
  1976年   43篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
本文对弧型小方坯连铸机工艺与设备进行了分析,介绍了连铸生产的PLC控制系统。及其软件设计。  相似文献   
103.
本文介绍了用饱和蒸汽对冷凝式汽轮机进行清洗除垢时主要参数的确定、操作要点及清洗方案,清洗后的汽轮机运行正常。  相似文献   
104.
We report a detailed mapping of a 2-D dopant profile on a fully processed industrial sample with large dynamic range and high spatial resolution by utilizing a dopant-selective etching process and Atomic Force Microscopy. The experimental results show excellent agreement with those obtained from SRP and SIMS as corroborative methods. We also discuss the most critical factors which influence the applicability, reproducibility, and reliability of this method  相似文献   
105.
The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process  相似文献   
106.
本文实验研究了BHP的浓度对产生O2(1△)的影响。实验结果表明:当BHP浓度大于3.5M时,Cl2利用率以及O2(1△)的产率将不依赖于BHP浓度的变化而变化,同时,实验结果表明,使用低浓度的BHP对COIL的操作是可行的。  相似文献   
107.
C.S. Li  P.K. Hopke 《Indoor air》1992,2(2):84-100
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased.  相似文献   
108.
The authors reply to the comments by Koppelaar and Tolhuizen (see ibid. vol.46, no.9, p.573, 1998). They state that the optimum choice of the slopes used to perform the encoding process in a projection code always results in maximizing the minimum Hamming distance so that d=2 r  相似文献   
109.
110.
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