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   27579篇
  免费   933篇
  国内免费   615篇
电工技术   731篇
综合类   971篇
化学工业   5821篇
金属工艺   4702篇
机械仪表   974篇
建筑科学   786篇
矿业工程   264篇
能源动力   258篇
轻工业   1678篇
水利工程   113篇
石油天然气   340篇
武器工业   124篇
无线电   2053篇
一般工业技术   7355篇
冶金工业   534篇
原子能技术   291篇
自动化技术   2132篇
  2024年   34篇
  2023年   168篇
  2022年   573篇
  2021年   579篇
  2020年   368篇
  2019年   321篇
  2018年   369篇
  2017年   496篇
  2016年   845篇
  2015年   1472篇
  2014年   1629篇
  2013年   1638篇
  2012年   1514篇
  2011年   2780篇
  2010年   2219篇
  2009年   2178篇
  2008年   1795篇
  2007年   1662篇
  2006年   1179篇
  2005年   1209篇
  2004年   1212篇
  2003年   1255篇
  2002年   1118篇
  2001年   429篇
  2000年   334篇
  1999年   364篇
  1998年   247篇
  1997年   213篇
  1996年   160篇
  1995年   128篇
  1994年   98篇
  1993年   65篇
  1992年   61篇
  1991年   37篇
  1990年   36篇
  1989年   35篇
  1988年   32篇
  1987年   20篇
  1986年   24篇
  1985年   24篇
  1984年   25篇
  1983年   14篇
  1982年   21篇
  1981年   33篇
  1980年   72篇
  1979年   8篇
  1978年   9篇
  1977年   7篇
  1975年   5篇
  1973年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
串行接口LED数码管及键盘管理器件ZLG7289A的原理与应用   总被引:2,自引:0,他引:2  
介绍了LED数码管及键盘管理器ZLG7289A的原理与应用。该芯片具有SPI串行接口,可同时驱动8位共阴式数码管(或64只独立LED),还可连接多达64键的键盘矩阵,单块芯片即可完成LED显示、键盘接口等全部功能。文章给出了ZLG7289A的特点、引脚功能、指令说明和经典电路.并以单片机AT89C51为例,给出了其接口电路及相应源程序。  相似文献   
122.
123.
124.
本文通过对摩擦片厚度在线测量装置系统构成的全面分析,对其驱动电路子系统进行了理论探索和技术研究,完成了相应的电路设计、误差分析及器件选择等工作,并进行了具体的实验验证,证明该驱动电路具有良好的性能,可圆满实现摩擦片厚度在线检测和实时分析的工作任务。  相似文献   
125.
本文提出了一种基于LonWorks和DSPs的智能节点设计方案,并给出了具体的实现方法。该方案简单、可靠,充分利用了LonWorks强大的网络性、可靠性和DSPs强大的数据处理能力,大大提升了节点的智能化程度。  相似文献   
126.
The kinetics of the carbothermal reduction of clay under argon atmosphere has been investigated by the X-ray diffraction method. The clay-carbon (excess) mixture was formed into 2 cm diameter disks of different thicknesses. Experimental data evidences the significant effect of sample thickness on the reaction rate at 1400 °C. Decreasing thickness promotes mullite dissociation and formation of SiC and alumina powders. Mathematical modeling of the reaction system showed the gas diffusion in the Knudsen regime through the pellet to be the rate controlling step. Diffusivity of CO and reacted core tortuosity factor have been calculated.  相似文献   
127.
The effect of heat treatment on microstructure of a plain-weave carbon fabric reinforced carbon-carbon composite with phenolformaldehyde-derived carbon matrix was investigated by X-ray diffraction. The diffraction patterns were analysed by the least-square fitting program Carbonxs. After heat treatment from 1000 to 2800 °C the interplanar distance of (002) planes decreased from 3.488 to 3.420 Å and the lattice parameter in basal plane increased from 2.440 to 2.464 Å, respectively. Simultaneously, the coherent block size in the basal plane directions increased from 18 to 54 Å, which was accompanied by an increase of the fraction of organised carbon atoms from 0.50 to 0.85. The 002 diffraction profile of the composite was much narrower than the sum of peaks of the matrix and fabric alone. This can probably be caused by a better crystallographic ordering (or by a partial graphitisation) of the matrix in the composite. On the other hand, the composite Young’s modulus slightly decreased with the treatment temperature increasing from 2200 to 2800 °C in spite of the established strong improvement of fibre crystallinity and, therefore, fibre modulus. The mechanisms diminishing the modulus of composite (e.g. partial matrix graphitisation at the fibre/matrix interface and decreasing fibre/matrix contact area) probably prevailed over the increasing contribution of the fibre modulus.  相似文献   
128.
在辽宁省工业城市进行 A3钢大气暴露试验。两年后测出不同地点腐蚀率。依据所记录的各试验点的气象数据和污染数据,讨论了 A3钢的大气腐蚀规律。  相似文献   
129.
The growth time, growth mode and the method of preparing the supported catalysts play an important role in the growth of single-walled nanotubes (SWNTs). Their effects on the chemical vapor deposition (CVD) growth of SWNTs with MgO-supported catalysts were investigated in this study. It is shown that the growth rate of SWNTs was large during the initial few minutes of growth, however the quality of the tubes was low owing to the formation of many defects. Long term growth may favor the formation of tubes with high quality and high yield, but the introduction of other forms of carbon (impurities) is also unavoidable. There was a balance between the increase in yield and quality and sacrifice of the purity during growth of SWNTs. MgO-supported catalysts prepared by the co-precipitation method were found to be more effective for the synthesis of SWNTs than those prepared by the widely used impregnation method. The size and dispersion state of the catalyst were found to be crucial in enhancing the growth of SWNTs. In addition, growth on the surface of SWNTs over nanosized catalyst films was shown to be more favorable for the synthesis of tube products with higher quality, yield and purity.  相似文献   
130.
The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.  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