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   94984篇
  免费   1630篇
  国内免费   733篇
电工技术   1267篇
综合类   2660篇
化学工业   13589篇
金属工艺   5281篇
机械仪表   3528篇
建筑科学   2605篇
矿业工程   751篇
能源动力   1483篇
轻工业   4265篇
水利工程   1444篇
石油天然气   703篇
武器工业   54篇
无线电   10462篇
一般工业技术   18531篇
冶金工业   3824篇
原子能技术   480篇
自动化技术   26420篇
  2023年   124篇
  2022年   265篇
  2021年   364篇
  2020年   322篇
  2019年   229篇
  2018年   14728篇
  2017年   13599篇
  2016年   10232篇
  2015年   935篇
  2014年   637篇
  2013年   933篇
  2012年   3660篇
  2011年   9955篇
  2010年   8754篇
  2009年   5994篇
  2008年   7233篇
  2007年   8211篇
  2006年   508篇
  2005年   1534篇
  2004年   1396篇
  2003年   1423篇
  2002年   771篇
  2001年   322篇
  2000年   453篇
  1999年   336篇
  1998年   387篇
  1997年   317篇
  1996年   310篇
  1995年   219篇
  1994年   213篇
  1993年   191篇
  1992年   168篇
  1991年   178篇
  1990年   105篇
  1989年   112篇
  1988年   124篇
  1987年   110篇
  1986年   92篇
  1985年   129篇
  1984年   122篇
  1983年   134篇
  1982年   96篇
  1981年   97篇
  1980年   84篇
  1979年   89篇
  1978年   75篇
  1977年   66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 15 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.
氢工质在新能源与动力、航天推进、化工材料等领域有着广泛应用。通过开展高温氢工质热力学与输运性质研究,建立了原子态氢、分子态氢、热解平衡态氢的热物理性质计算模型,开发了热物性计算程序Prop_H_H2,适用范围为温度100~3 500 K、压力104~5×107 Pa 。验证表明,Prop_H_H2在适用范围内计算氢工质的物性参数合理可靠,在温度200~3 000 K、压力104~107 Pa范围内,程序预测值更加准确,相对偏差在±5%左右。本研究可为氢工质相关的航天推进、应用物理学、能源动力等行业的科研和应用提供支持借鉴。  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