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   92626篇
  免费   1339篇
  国内免费   510篇
电工技术   997篇
综合类   2503篇
化学工业   13109篇
金属工艺   5089篇
机械仪表   3355篇
建筑科学   2476篇
矿业工程   664篇
能源动力   1428篇
轻工业   4149篇
水利工程   1370篇
石油天然气   496篇
武器工业   16篇
无线电   10279篇
一般工业技术   18308篇
冶金工业   3712篇
原子能技术   361篇
自动化技术   26163篇
  2023年   84篇
  2022年   143篇
  2021年   218篇
  2020年   191篇
  2019年   152篇
  2018年   14642篇
  2017年   13517篇
  2016年   10131篇
  2015年   794篇
  2014年   476篇
  2013年   751篇
  2012年   3496篇
  2011年   9798篇
  2010年   8627篇
  2009年   5879篇
  2008年   7096篇
  2007年   8070篇
  2006年   412篇
  2005年   1457篇
  2004年   1346篇
  2003年   1375篇
  2002年   727篇
  2001年   265篇
  2000年   391篇
  1999年   279篇
  1998年   350篇
  1997年   285篇
  1996年   267篇
  1995年   202篇
  1994年   189篇
  1993年   178篇
  1992年   157篇
  1991年   167篇
  1990年   101篇
  1989年   106篇
  1988年   119篇
  1987年   104篇
  1986年   90篇
  1985年   127篇
  1984年   121篇
  1983年   134篇
  1982年   95篇
  1981年   95篇
  1980年   84篇
  1979年   87篇
  1978年   74篇
  1977年   65篇
  1976年   72篇
  1955年   65篇
  1954年   69篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Ganapati  Reddi  Samoju  Visweswara Rao  Jammu  Bhaskara Rao 《SILICON》2021,13(9):2869-2880
Silicon - This paper presents, analytical modeling of surface potential,threshold voltage and DIBL for a Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET considering the parabolic...  相似文献   
3.
4.
利用模糊控制和比例积分微分(PID)控制相结合的手段对注塑机料筒温度进行了控制,同时以Matlab 6.0软件为仿真平台,对料筒温度控制进行了模拟仿真研究。实验发现,在注塑机料筒升温过程中利用CHR整定的PID控制手段和模糊控制手段,恒温过程中利用人工整定的PID控制手段,可保证快速的料筒升温响应速率和稳定的保温过程。通过实际注塑实验对该仿真结果进行了验证,在十组实验中,料筒温度误差不超过2%,产品翘曲变形量不超过0.059 mm。  相似文献   
5.
The performance of low-to-intermediate temperature (400–800?°C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped ceratezirconate and hybrid-doped ceratezirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application.  相似文献   
6.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms.  相似文献   
7.
8.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
9.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  相似文献   
10.
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