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   370篇
  免费   22篇
  国内免费   15篇
电工技术   26篇
综合类   19篇
化学工业   43篇
金属工艺   37篇
机械仪表   8篇
建筑科学   55篇
矿业工程   4篇
能源动力   18篇
轻工业   18篇
石油天然气   21篇
武器工业   6篇
无线电   45篇
一般工业技术   35篇
冶金工业   8篇
原子能技术   2篇
自动化技术   62篇
  2023年   3篇
  2022年   6篇
  2021年   15篇
  2020年   6篇
  2019年   1篇
  2018年   8篇
  2017年   5篇
  2016年   19篇
  2015年   13篇
  2014年   14篇
  2013年   21篇
  2012年   16篇
  2011年   34篇
  2010年   14篇
  2009年   41篇
  2008年   27篇
  2007年   41篇
  2006年   24篇
  2005年   15篇
  2004年   18篇
  2003年   17篇
  2002年   14篇
  2001年   3篇
  2000年   10篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   5篇
  1994年   2篇
  1993年   4篇
  1989年   1篇
  1987年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有407条查询结果,搜索用时 15 毫秒
1.
2.
为实时修正制导炸弹弹道轨迹从而精确命中目标,设计一种简易制导炸弹舵机控制系统.该系统硬件部分以dsPIC33EP512MC806为控制核心、以PWM信号驱动用H桥芯片BTS7970B控制直流电机、以外扩A/D采集芯片TLC2374采集经电位器测量的舵面位置反馈信号;软件采用C语言实现5个模块之间的通信.分析结果表明:该系统简化了电路设计的难度,提高了可靠性,满足了制导炸弹的性能要求.  相似文献   
3.
4.
This paper suggests that, for developing countries, the creation of economic regulatory agencies, separate from the ministry in charge of water and sanitation, may not be a necessary or sufficient condition to stimulate large scale private involvement (PPPs) in the sector. The odds of an impact are higher for Latin American countries than other regions and for countries with higher income levels. They are also better when inflation is high. At the margin, the odds are unrelated to the contract type, except for greenfield projects, for which they may be contraindicated.  相似文献   
5.
朱高建 《中国矿业》2021,30(S1):182-183
针对采厂矿车翻卸人工计数可靠性低、安全风险大等问题,提出一种矿车翻卸自动计数系统设计方案,以JRF33铁路车号识别装置为载体,以RS485为通讯协议,对采集数据进行统计分析。结果显示,计数系统运行良好,翻卸数据采集及时、准确、完整。系统对采矿原料运输数据统计、分析应用和生产指导有一定的指导意义。  相似文献   
6.
田雁飞  伍惠玲 《微电机》2020,(10):103-106
为提高电机转子磁钢固定的可靠性和经济性,本文采用了转子注塑工艺来对转子磁钢进行固定。通过对注塑材料的性能分析与验证确定注塑材料的可靠性。通过对转子注塑工艺进行验证,确定了注塑工艺参数,保证了注塑工艺的可行性。  相似文献   
7.
A comparative study of the purification of betanin   总被引:3,自引:0,他引:3  
Betanin is a natural pigment with antioxidant properties used as a food colourant. This work describes the spectrophotometric and chromatographic quantification of betanin (2S/15S) and its epimer isobetanin (2S/15R) in fresh beetroot juice, food-grade beetroot powder and betanin standard diluted in dextrin. Absorption spectra of all three samples were deconvoluted using a mixed three-function model. Food-grade beetroot powder has the largest amount of violet-red impurities, probably formed during processing. The purification of betanin from these complex matrices was carried out by seven different methods. Ion exchange chromatography was the most efficient method for the purification of betanin from all samples; however, fractions contain high amounts of salt. Reversed-phase HPLC as well as reversed-phase column chromatography also produced good results at a much faster rate. The longer retention time of isobetanin when compared to betanin in reversed-phase conditions has been investigated by means of quantum-mechanical methods.  相似文献   
8.
利用二氧化锰(MnO2)纳米材料新颖的化学、物理特性,研究其对三联吡啶钌(Ru(bpy)3^2+的电致化学发光(ECL)的催化作用,结果发现,纳米MnO2材料在温和的条件且较正的电位(+O.4V(VS.Ag/AgCl))下可以催化Ru(bpy)33^2+产生阴极ECL。同时推导了其催化机理,为制备一种新型的高灵敏度的ECLSensor奠定了理论基础。  相似文献   
9.
This study evaluates the relationship between the spatial distribution of broadband providers and the presence of knowledge intensive firm clusters in US counties. Results highlight this relationship is heterogeneous and localized. In some places, broadband appears to be an essential link that enables knowledge firms to strategically locate in lower cost counties and in close proximity to major knowledge centres. In other places, the availability of broadband Internet connections are unable the negative externalities associated with locations in more remote areas of the country. From a policy perspective, this suggests that broadband should be viewed as a key component, but not the only component, of comprehensive local economic development plans.  相似文献   
10.
This paper extends the seminal Blanchard and Katz regional labour market model to include interaction effects using a dynamic spatial panel data approach. Three key contributions of this extended model are: (i) the unrealistic assumption that regions are independent of one another no longer has to be made, (ii) the magnitude and significance of so‐called spillover effects can be empirically assessed, and (iii) both the temporal and spatial propagation of labour demand shocks can be investigated. Using annual data from 1986–2010 for 112 regions across eight EU countries, both the non‐spatial and spatial models are estimated. It is found that the majority of the spillover effects are highly significant. Consistent with economic theory, the impact of a region‐specific demand shock is largest in the region where the shock instigates. The shock also propagates to other regions, especially impacting the first and second‐order neighbours.  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