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   6611篇
  免费   191篇
  国内免费   18篇
电工技术   146篇
综合类   6篇
化学工业   1320篇
金属工艺   170篇
机械仪表   130篇
建筑科学   162篇
矿业工程   31篇
能源动力   302篇
轻工业   374篇
水利工程   27篇
石油天然气   19篇
无线电   807篇
一般工业技术   1378篇
冶金工业   996篇
原子能技术   45篇
自动化技术   907篇
  2023年   57篇
  2022年   80篇
  2021年   164篇
  2020年   154篇
  2019年   154篇
  2018年   182篇
  2017年   182篇
  2016年   148篇
  2015年   119篇
  2014年   168篇
  2013年   430篇
  2012年   232篇
  2011年   315篇
  2010年   258篇
  2009年   265篇
  2008年   269篇
  2007年   225篇
  2006年   211篇
  2005年   207篇
  2004年   161篇
  2003年   154篇
  2002年   137篇
  2001年   129篇
  2000年   103篇
  1999年   109篇
  1998年   254篇
  1997年   190篇
  1996年   128篇
  1995年   91篇
  1994年   122篇
  1993年   124篇
  1992年   92篇
  1991年   68篇
  1990年   69篇
  1989年   57篇
  1988年   69篇
  1987年   64篇
  1986年   57篇
  1985年   95篇
  1984年   69篇
  1983年   59篇
  1982年   48篇
  1981年   60篇
  1980年   57篇
  1979年   53篇
  1978年   37篇
  1977年   51篇
  1976年   57篇
  1974年   35篇
  1973年   37篇
排序方式: 共有6820条查询结果,搜索用时 15 毫秒
1.
2.
The Journal of Supercomputing - Currently, all online social networks (OSNs) are considered to follow a power-law distribution. In this paper, the degree distribution for multiple OSNs has been...  相似文献   
3.
ABSTRACT

A mathematical model has been developed by coupling genetic algorithm (GA) with heat and material balance equations to estimate rate parameters and solid-phase evolution related to the reduction of iron ore-coal composite pellets in a multi-layer bed Rotary hearth Furnace (RHF). The present process involves treating iron ore-coal composite pellets in a crucible over the hearth in RHF. The various solid phases evolved at the end of the process are estimated experimentally, and are used in conjunction with the model to estimate rate parameters. The predicted apparent activation energy for the wustite reduction step is found to be lower than those of the reduction of higher oxides. The thermal efficiency is found to decrease significantly with an increase in the carbon content of the pellet. Thermal efficiency was also found to increase mildly up to three layers. Multilayer bed remains as a potential design parameter to increase thermal efficiency.  相似文献   
4.
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   
5.

Floods are common and recurring natural hazards which damages is the destruction for society. Several regions of the world with different climatic conditions face the challenge of floods in different magnitudes. Here we estimate flood susceptibility based on Analytical neural network (ANN), Deep learning neural network (DLNN) and Deep boost (DB) algorithm approach. We also attempt to estimate the future rainfall scenario, using the General circulation model (GCM) with its ensemble. The Representative concentration pathway (RCP) scenario is employed for estimating the future rainfall in more an authentic way. The validation of all models was done with considering different indices and the results show that the DB model is most optimal as compared to the other models. According to the DB model, the spatial coverage of very low, low, moderate, high and very high flood prone region is 68.20%, 9.48%, 5.64%, 7.34% and 9.33% respectively. The approach and results in this research would be beneficial to take the decision in managing this natural hazard in a more efficient way.

  相似文献   
6.
7.
Neural Computing and Applications - The advanced high-end gadgets and sophisticated machines require effective mechanism of transferring heat away from the sources. In a large number of...  相似文献   
8.
9.
This investigation reports the effective use of the Diels–Alder (DA) click reaction in the preparation of self-healing bio-based dendritic methacrylates having reactive furfuryl functionality. Bio-based methacrylates were synthesized by modifying tannic acid with glycidyl methacrylate and furfuryl functionality was introduced by atom transfer radical polymerization with varied amount of furfuryl methacrylate monomer. The thermoreversible network was successfully achieved by DA and retro-DA reaction between the furfuryl groups and a bifunctional maleimide crosslinker, bismaleimide. This process was studied by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and solvent exposure tests. Differential scanning calorimetry analysis was used to determine the endothermic retro-DA reaction in the DA adduct. The self-healing property of the above crosslinked material was demonstrated by monitoring the repair of a scratch in the polymer film upon heating and cooling. This was analyzed by scanning electron microscopy. POLYM. ENG. SCI., 60:140–150, 2020. © 2019 Society of Plastics Engineers  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