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   82757篇
  免费   7035篇
  国内免费   7070篇
电工技术   6882篇
技术理论   3篇
综合类   7294篇
化学工业   10377篇
金属工艺   7682篇
机械仪表   6536篇
建筑科学   6240篇
矿业工程   2181篇
能源动力   2395篇
轻工业   5987篇
水利工程   1967篇
石油天然气   3998篇
武器工业   870篇
无线电   9520篇
一般工业技术   8465篇
冶金工业   2517篇
原子能技术   1264篇
自动化技术   12684篇
  2024年   376篇
  2023年   1101篇
  2022年   2174篇
  2021年   2999篇
  2020年   2268篇
  2019年   1734篇
  2018年   1782篇
  2017年   2128篇
  2016年   1930篇
  2015年   2726篇
  2014年   3599篇
  2013年   4111篇
  2012年   5053篇
  2011年   7768篇
  2010年   5920篇
  2009年   5161篇
  2008年   5249篇
  2007年   4502篇
  2006年   4500篇
  2005年   3796篇
  2004年   5349篇
  2003年   3358篇
  2002年   3447篇
  2001年   2906篇
  2000年   1897篇
  1999年   2063篇
  1998年   1326篇
  1997年   1182篇
  1996年   777篇
  1995年   621篇
  1994年   501篇
  1993年   1267篇
  1992年   1018篇
  1991年   594篇
  1990年   582篇
  1989年   470篇
  1988年   257篇
  1987年   83篇
  1986年   63篇
  1985年   61篇
  1984年   40篇
  1983年   16篇
  1982年   27篇
  1981年   17篇
  1980年   25篇
  1979年   14篇
  1973年   2篇
  1965年   4篇
  1959年   6篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
“团队项目训练法”是充分利用各种市场资源,按照市场营销工作实际,让学生自组团队、自寻商机、自设项目,理论联系实际分析营销环境.对真实对象进行市场营销方案设计、实施、评估,亲历市场营销的完整过程,以此进一步掌握理论,训练技能,提高能力。介绍了重庆科技学院对市场营销专业本科生运用“团队训练法”进行实践教学的做法及效果。  相似文献   
72.
We presented the analysis of the incomplete conduction in bonding medium in high power GaN-based light-emitting diode (LED) packages. A numerical study was carried out with parametric model to understand the junction temperature variation due to bonding medium defects. Transient thermal measurement was performed to evaluate LED’s junction temperature. Thermal resistance from chip to lead frame was 20 K/W in our sample LED. It was suggested that only 60% of the surface area of the bonding medium was involved...  相似文献   
73.
Microgrooves were prepared on Si(100) surface by photolithography and wet etching.Subsequently,Si-N-O films were deposited on the microgrooves by unbalanced magnetron sputtering(UBMS) and micro-patterned surfaces of Si-N-O films were obtained.The size of the micropatterns was measured by surface profilometer.The chemical composition of Si-N-O films were characterized by X-ray photoelectron spectrometry(XPS) and the wettability of the micropatterned surfaces was evaluated by contact angle measurement.The beh...  相似文献   
74.
A novel double suction shaft-less mini pump was developed for heat control of small energy systems in this study.The mini pump impeller with an exit diameter of 40 mm was combined with the motor rotor supported by the hybrid dynamic bearing.The specific speed of the pump was 125 min-1 m3 min-1 m.The hydraulic performance of the pump was investigated experimen-tally under four rotational speeds.From the test results,it was recognized that the pump could provide a flow discharge of 5 L/min and head of 1.5 m,w...  相似文献   
75.
Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hol...  相似文献   
76.
The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus...  相似文献   
77.
Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation ...  相似文献   
78.
The structures and field emission properties of multi-walled carbon nanotube arrays implanted with Zn+ by MEVVA ion implanter have been investigated.The results revealed that Zn+implantation induced structural damage and that the top of carbon nanotubes with multi-layered graphite structure were transformed into carbon nanowires with amorphous structure.Meanwhile,C:Zn solid solution was synthesized after Zn+ implantation.The turn-on field and threshold field were 0.80 and 1.31 V/μm,respectively for original...  相似文献   
79.
Based on fast Markov chain simulation for generating the samples distributed in failure region and saddlepoint approximation(SA) technique,an efficient reliability analysis method is presented to evaluate the small failure probability of non-linear limit state function(LSF) with non-normal variables.In the presented method,the failure probability of the non-linear LSF is transformed into a product of the failure probability of the introduced linear LSF and a feature ratio factor.The introduced linear LSF wh...  相似文献   
80.
The modified hydrodynamic theory of long rod penetration into semi-infinite targets was established independently by Alek-seevskii and Tate over forty years ago and since then many investigators contributed much to the development of the high speed penetration mechanics.However,in all the models proposed so far,the target resistance Rt is not well defined and usually determined by adjusting it until the predicted depth of penetration comes to an agreement with experimental data.In this paper,assumptions are...  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