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   9221篇
  免费   618篇
  国内免费   310篇
电工技术   385篇
综合类   377篇
化学工业   1652篇
金属工艺   434篇
机械仪表   423篇
建筑科学   619篇
矿业工程   161篇
能源动力   306篇
轻工业   544篇
水利工程   114篇
石油天然气   287篇
武器工业   34篇
无线电   1496篇
一般工业技术   1320篇
冶金工业   709篇
原子能技术   79篇
自动化技术   1209篇
  2024年   24篇
  2023年   124篇
  2022年   229篇
  2021年   315篇
  2020年   195篇
  2019年   196篇
  2018年   255篇
  2017年   256篇
  2016年   261篇
  2015年   256篇
  2014年   387篇
  2013年   554篇
  2012年   501篇
  2011年   620篇
  2010年   554篇
  2009年   521篇
  2008年   574篇
  2007年   458篇
  2006年   468篇
  2005年   336篇
  2004年   298篇
  2003年   304篇
  2002年   272篇
  2001年   229篇
  2000年   214篇
  1999年   227篇
  1998年   289篇
  1997年   219篇
  1996年   210篇
  1995年   157篇
  1994年   133篇
  1993年   98篇
  1992年   64篇
  1991年   52篇
  1990年   42篇
  1989年   40篇
  1988年   32篇
  1987年   28篇
  1986年   24篇
  1985年   16篇
  1984年   8篇
  1983年   8篇
  1982年   7篇
  1981年   9篇
  1980年   15篇
  1979年   13篇
  1978年   7篇
  1976年   13篇
  1975年   9篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
This paper presents an artificial intelligence approach of using evolutionary programming to estimate the transient and subtransient parameters of a generator under normal operation. The estimation using evolutionary programming is compared with that using a corrected extended Kalman filter. The comparisons with both simulation and micromachine test results show that evolutionary programming is robust to search the real values of parameters even when the data are highly contaminated by noise, while with the extended Kalman filter, the estimation tends to diverge with such data  相似文献   
12.
In this study, an aluminum based metallic matrix (Al-2wt.% Cu) was reinforced with SiC particulates using a conventional casting technique and a new disintegrated melt deposition technique. Microstructural characterization studies conducted on the samples taken from disintegrated melt deposition technique revealed a more uniform distribution of SiC particulates and good interfacial integrity between SiC particulates and metallic matrix when compared to the conventionally cast composite samples. Results of ambient temperature mechanical tests demonstrate an increase in 0.2% YS and ultimate tensile strength of samples taken from disintegrated melt deposition technique when compared with the unreinforced and conventionally cast composite samples. The results of microstructural characterization and mechanical testing were finally rationalized in terms of the nature of processing technique employed to reinforce Al-2wt.% Cu metallic matrix with SiC particulates.  相似文献   
13.
14.
Random switching techniques for inverter control   总被引:1,自引:0,他引:1  
New techniques which dramatically reduce acoustic noise by randomising the inverter switching frequency for inverter control are presented. It is shown that the proposed techniques combine the advantages of conventional pulsewidth modulation (PWM) techniques based on regular-sampling techniques and random PWM techniques  相似文献   
15.
16.
17.
Tramadol hydrochloride is a centrally acting synthetic analgesic in widespread clinical use. Despite different degrees of opioid-like characteristics in preclinical tests, it is characterized by lack of full naloxone reversibility or naloxone-precipitated withdrawal in humans. To investigate this apparent discrepancy, the present study measured the affinity of tramadol (and its enantiomers) and an active O-desmethyl metabolite (M1) (and its enantiomers) to cloned human opioid receptors of the mu, delta and kappa type stably expressed in HN9.10 neuroblastoma cells. At mu sites, the Ki values for tramadol, its (+) and (-) enantiomers, M1, and its (+) and (-) enantiomers were 17000, 15700, 28800, 3190, 153 and 9680 nM, respectively, compared to 7.1 nM for morphine. These results are consistent with the suggestion of a non-opioid contribution to the clinical profile of tramadol.  相似文献   
18.
Ternary alloying of MoSi2 with adding a series of transition elements was investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Iron, Co, Ni, Cr, V, Ti, and Nb were chosen as alloying elements according to the AB2 structure map or the atomic size factor. The studied MoSi2 base alloys were prepared by the arc melting process from high-purity metals. The EDS analysis showed that Fe, Co, and Ni have no solid solubility in as-cast MoSi2, while Cr, V, Ti, and Nb exhibit limited solid solubilities, which were determined to be 1.4±0.7, 1.4±0.4, 0.4±0.1, and 0.8±0.1. Micro-structural characterization indicated that Mo-Si-MVIII (MVIII=Fe, Co, Ni) and Mo-Si-Cr alloys have a two-phase as-cast microstructure, i.e., MoSi2 matrix and the second-phase FeSi2, CoSi, NiSi2, and CrSi2, respectively. In as-cast Mo-Si-V, Mo-Si-Ti, and Mo-Si-Nb alloys, besides MoSi2 and C40 phases, the third phases were observed, which have been identified to be (Mo, V)5Si3, TiSi2, and (Mo, Nb)5Si3.  相似文献   
19.
中频反应溅射SiO2膜与直流溅射ITO膜的在线联镀   总被引:2,自引:2,他引:0  
多数ITO透明导电玻璃生产线在实现SiO2膜与ITO膜在线联镀时,应用SiO2靶射频溅射沉积SiO2膜工艺和ITO靶直流溅射沉积ITO膜工艺,如果SiO2膜应用硅靶反应磁控溅射工艺,存在这种工艺是否可以与ITO靶直流溅射沉积ITO膜工艺在线联用以及如何实现联用的问题。作者对现有的生产线进行了改造设计、加工,做了大量实验、质谱分析和多项测试研究,成功地实现反应溅射SiO2膜与ITO膜在线联镀,做到SiO2镀膜室的工作状态的变化基本上不影响ITO镀膜室的工艺条件。  相似文献   
20.
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