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   653篇
  免费   43篇
  国内免费   1篇
电工技术   11篇
综合类   2篇
化学工业   167篇
金属工艺   16篇
机械仪表   15篇
建筑科学   9篇
矿业工程   1篇
能源动力   20篇
轻工业   71篇
水利工程   3篇
石油天然气   7篇
无线电   52篇
一般工业技术   131篇
冶金工业   118篇
原子能技术   20篇
自动化技术   54篇
  2023年   15篇
  2022年   9篇
  2021年   36篇
  2020年   16篇
  2019年   13篇
  2018年   23篇
  2017年   23篇
  2016年   25篇
  2015年   27篇
  2014年   27篇
  2013年   34篇
  2012年   43篇
  2011年   42篇
  2010年   21篇
  2009年   26篇
  2008年   17篇
  2007年   24篇
  2006年   22篇
  2005年   16篇
  2004年   21篇
  2003年   5篇
  2002年   18篇
  2001年   7篇
  2000年   16篇
  1999年   9篇
  1998年   44篇
  1997年   30篇
  1996年   17篇
  1995年   16篇
  1994年   7篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1989年   1篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1977年   3篇
  1976年   10篇
  1975年   4篇
  1974年   1篇
  1965年   2篇
排序方式: 共有697条查询结果,搜索用时 15 毫秒
161.
162.
163.
A host material containing tetraphenylsilane moiety, 9-(4-triphenylsilanyl-(1,1′,4,1′′)-terphenyl-4′′-yl)-9H-carbazole (TSTC), was synthesized for green phosphorescent organic light emitting diodes. The tetraphenylsilane moiety was introduced to provide high triplet energy level, thermal and chemical stability, and glassy properties leading to high efficiency and operational stability of the devices. Ir(ppy)3 based OLEDs using the TSTC host and DTBT (2,4-diphenyl-6-(4′-triphenylsilanyl-biphenyl-4-yl)-1,3,5-triazine) hole blocking layer (HBL) resulted in the maximum external quantum efficiency of 19.8% and the power efficiency of 59.4 lm/W. High operational stability with a half lifetime of 160,000 h at an initial luminance of 100 cd/m2 was achieved from an electrophosphorescent device using TSTC host and BAlq HBL.  相似文献   
164.
A mathematical model of temperature and wheat moisture content distribution inside a triangular spouted bed dryer was developed. The model is based on analysis of heat and mass transfer inside the dryer. In addition to that, an empirical bulk density model has been developed for wheat and included in the drying simulation. A laboratory-scale triangular spouted bed (TSB) dryer was used to dry wheat grain to validate the model. The dryer was divided into three sections, namely spouting, downcomer, and fountain. A series of drying runs were conducted to record moisture and temperature profile. There were two distinct regions observed during wheat drying. A constant rate period was observed during the initial drying stage and the falling rate period took place at the later drying stage. Initial moisture content and operating drying temperature governed the timing of transition from constant rate period to falling rate period. The model can be used to accurately predict the moisture content of wheat during drying. The temperature prediction inside the TSB dryer was less accurate, especially at high temperatures due to heat losses in the experimental dryer. Further studies are needed to improve the accuracy of this model, especially with regard to the temperature prediction.  相似文献   
165.
This study presents a new approach to determine the damage degree of liquefaction caused by a large earthquake. We propose an artificial neural network (ANN) model based only on the seismic records of ground and define the degree of liquefaction “DDL” as a damage index. This ANN model predicts the degree of excess pore water pressure increase as the correct output label based on the seismic records obtained from the three-dimensional shaking table test. The proposed model achieved high accuracy, and the outcomes from training data indicated that the ANN model is suitable to function as a liquefaction assessment system. Further, to evaluate the applicability of the proposed ANN model in the real world, the datasets of waves from three actual seismic records were input to the ANN as validation data. The DDL judgment obtained was a good fit with the real phenomena observed.  相似文献   
166.
Surface modification of electrodes for realizing high electrochemical reactivity and thermal stability is an attractive strategy for high-performance low temperature solid oxide fuel cells (LT-SOFCs). Herein, the atomic-layer-deposited (ALD) CeO2-coated Pt anode structure is fabricated and applied to anodized aluminum oxide (AAO)-based thin-film LT-SOFC. The effect of Pt anode morphology on the infiltration of ALD CeO2 is elucidated. Anode kinetics are improved in the ALD CeO2-coated porous Pt anode cell possibly due to the larger Pt–CeO2 interface density, leading to a decrease in activation resistance by 86%. The maximum power density of the cell with the ALD CeO2-coated porous Pt anode shows 478 mW/cm2; a dramatic improvement by a factor of two compared to the bare porous Pt anode.  相似文献   
167.
环境保护是可持续发展战略的重要内容之一。要搞好环保工作关键是要在思想上给予高度的重视。建立健全环保制度,实行环保工作目标管理,积极引进新工艺、新设备,提高环保硬件水平,使环保工作更上一层楼。  相似文献   
168.
The electrochemical behaviour of massive chalcopyrite electrodes has been studied in an acid medium (pH1.5) containing silver ions (0.02gdm?3Ag+) and thermophilic bacteria (68°C). Preliminary tests on particulate electrodes made from graphite, elemental sulfur and Ag2S were included to determine the electrochemical response of reactants (Ag+) and products (S° and Ag2S) associated with the dissolution of chalcopyrite in the presence of silver. Massive chalcopyrite electrodes under potential scan showed a dependence on the dissolution of the Ag2S film with both the time of contact with the silver solution and [Ag+]. As well as Ag2S, metallic silver was detected on the chalcopyrite surface. It has been demonstrated that Fe3+ and bacteria play an important role in the regeneration of the Ag2S film. The breakdown of this film is a requirement for the further dissolution of chalcopyrite. The bioleaching of chalcopyrite with thermophilic microorganisms in the presence of silver decreased the decomposition potential of the electrode and favoured its electrodissolution. Bioleaching treatment in the presence of silver ions for periods of time longer than two weeks did not improve the surface reactivity. However, in the initial stages of the process, the lower reactivity of the bioleached electrodes was probably related to a toxic effect of silver on the microorganisms.  相似文献   
169.
We successfully fabricated cost-effective and efficient pulse electrodeposited Fe2O3 photoanodes for PEC water splitting application. Surface modifications of Fe2O3 by oxygen evolution catalysts like cobalt phosphate (Co–Pi), a monoclinic BiVO4 or both showed cathodic/anodic shift in photocurrent with significantly improved photo-response.  相似文献   
170.
Using self-reported survey data (N = 281), the present study explores the structural relationships among mobile users’ perceptions of the suitability of two types of mobile news (political feature news and entertainment news), users’ motivations for mobile news usage, and their behavioral patterns. Our findings show that two types of perceived suitability for mobile news, particularly for political feature news, are strongly associated with all dimensions of motivations for mobile news usage. Furthermore, as predicted, our findings show that the information-seeking motive is the very factor that determines mobile news usage. The results also reveal that the accessibility motive mediates the relationship between the perceived suitability of obtaining news via a mobile device and users’ mobile news behavior. However, contrary to our expectation, the social utility motive does not mediate the relationship between users’ perceptions of the suitability of mobile devices for this purpose and their mobile news usage. Finally, the information-seeking and accessibility motives each have an indirect effect on the association between perceived suitability and mobile news usage. The implications of the study and recommendations for future research are also discussed.  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