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   77674篇
  免费   6662篇
  国内免费   4245篇
电工技术   4521篇
技术理论   1篇
综合类   7227篇
化学工业   12310篇
金属工艺   4251篇
机械仪表   4881篇
建筑科学   5276篇
矿业工程   1768篇
能源动力   2121篇
轻工业   7095篇
水利工程   1556篇
石油天然气   2939篇
武器工业   568篇
无线电   9359篇
一般工业技术   8463篇
冶金工业   3367篇
原子能技术   1106篇
自动化技术   11772篇
  2024年   245篇
  2023年   877篇
  2022年   1698篇
  2021年   2360篇
  2020年   1844篇
  2019年   1636篇
  2018年   1785篇
  2017年   2011篇
  2016年   2035篇
  2015年   2776篇
  2014年   3734篇
  2013年   4532篇
  2012年   5263篇
  2011年   5697篇
  2010年   5288篇
  2009年   5263篇
  2008年   5229篇
  2007年   4975篇
  2006年   4862篇
  2005年   4062篇
  2004年   3321篇
  2003年   3038篇
  2002年   3584篇
  2001年   3116篇
  2000年   2117篇
  1999年   1557篇
  1998年   1049篇
  1997年   842篇
  1996年   780篇
  1995年   685篇
  1994年   494篇
  1993年   374篇
  1992年   294篇
  1991年   234篇
  1990年   197篇
  1989年   122篇
  1988年   122篇
  1987年   89篇
  1986年   37篇
  1985年   61篇
  1984年   48篇
  1983年   40篇
  1982年   20篇
  1981年   29篇
  1980年   27篇
  1979年   15篇
  1978年   11篇
  1977年   19篇
  1976年   24篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
11.
There is no good method to measure the shape and the strain distributions of a structure changing with time. We have previously proposed the Fourier transform grid method (FTGM) to measure the three-dimensional shape and surface strain distributions of stationary objects by analysing the two-dimensional grating images recorded with two cameras. In the stereoscopic method, it is very important to determine the accurate geometric parameters of the camera system. In this paper, the positions and the directions of cameras are accurately determined using the FTGM applied to images of a reference object on which a two-dimensional grating is drawn. Applications for analysing shape and strain distributions of vibrating rubber plates and a moving human skin are shown.  相似文献   
12.
13.
曹红梅 《山西建筑》2003,29(18):34-35
介绍了阳泉市煤矿采空区对公路建设所造成的危害,对其上覆岩层变形破坏的地质因素及其破坏机理作了分析,指出应该采取各种措施减少对公路的破坏。  相似文献   
14.
预应力钢-混凝土组合梁的应用与研究   总被引:1,自引:0,他引:1  
回顾了预应力钢 混凝土组合梁国内外应用与研究历史 ,分析了现有规范及理论的不足 ,并指出了有待解决的问题。  相似文献   
15.
The current-voltage (I-V) characteristics of metal-oxide-semiconductor tunneling diodes distributed over a 3-in Si wafer were analyzed to investigate the stress distribution on the wafer. Generally, the substrate injection saturation current (J/sub sat/) decreases as the gate injection leakage current (J/sub g/) increases, the latter being dominated by oxide thickness via a trap related mechanism. A universal curve to fit all analyzed data was found and it is suggested that devices with extremely high (low) J/sub sat/ at a given J/sub g/ should be located in areas of the silicon lattice with relatively high external compressive (tensile) stress because of the stress-induced bandgap variation effect. The mapped locations of the highly stressed devices on a 3-in [100] Si wafer correspond to the patterns of slips caused by thermal stress during rapid thermal processing, as described in previous reports.  相似文献   
16.
17.
The humidity response characteristics of La doped BaTiO3 with different sintered densities and room temperature electrical conductivities were investigated using complex impedance measurement. The samples with low density and high resistivity showed the large and nearly linear sensitivity to the change of humidity. The impedance spectra of samples, when exposed to high humidity, can exhibit microstructure-related features, even though they do not give rise to a noticeable characteristic change when exposed to low humidity. The observed impedance patterns were dependent upon the density, and hence the oxidation kinetics of BaTiO3.  相似文献   
18.
The temperature dependence characteristics of hydrogenated amorphous silicon thin-film transistors were investigated. The results indicate that as the temperature was increased, the threshold voltage and the field-effect mobility were first increased, and then decreased, which may be controlled by different mechanisms at low and high temperatures. In addition, if the temperature was higher than 420 K, the Fermi level was promoted to the degenerate-like states, the current channel always existed due to the temperature effect, and the threshold voltage became negative.  相似文献   
19.
为使北京谱仪端盖族射计数器更好地工作在自猝灭流光SQS模式下,提高其能量分辨以及线性等指标,用Ar,CO2,Lsobutane三元工作气体对探测器的工作性能进行了仔细研究,找出了一适合于主雇地数器的工作气体,此外,还研究了异丁的纯度对探测器性能的影响。  相似文献   
20.
A new method to predict the critical heat flux (CHF) is proposed, based on the fuzzy clustering and artificial neural network. The fuzzy clustering classifies the experimental CHF data into a few data clusters (data groups) according to the data characteristics. After classification of the experimental data, the characteristics of the resulting clusters are discussed with emphasis on the distribution of the experimental conditions and physical mechanism. The CHF data in each group are trained in an artificial neural network to predict the CHF. The artificial neural network adjusts the weight so as to minimize the prediction error within the corresponding cluster. Application of the proposed method to the KAIST CHF data bank shows good prediction capability of the CHF, better than other existing methods.  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