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   3440篇
  免费   227篇
  国内免费   11篇
电工技术   45篇
综合类   18篇
化学工业   644篇
金属工艺   68篇
机械仪表   94篇
建筑科学   187篇
矿业工程   8篇
能源动力   105篇
轻工业   261篇
水利工程   35篇
石油天然气   30篇
无线电   381篇
一般工业技术   635篇
冶金工业   477篇
原子能技术   17篇
自动化技术   673篇
  2023年   42篇
  2022年   69篇
  2021年   116篇
  2020年   82篇
  2019年   93篇
  2018年   103篇
  2017年   91篇
  2016年   115篇
  2015年   98篇
  2014年   122篇
  2013年   235篇
  2012年   149篇
  2011年   250篇
  2010年   165篇
  2009年   175篇
  2008年   184篇
  2007年   187篇
  2006年   146篇
  2005年   106篇
  2004年   70篇
  2003年   67篇
  2002年   62篇
  2001年   48篇
  2000年   47篇
  1999年   40篇
  1998年   100篇
  1997年   72篇
  1996年   44篇
  1995年   45篇
  1994年   44篇
  1993年   29篇
  1992年   36篇
  1991年   20篇
  1990年   26篇
  1989年   26篇
  1988年   16篇
  1987年   20篇
  1986年   16篇
  1985年   22篇
  1984年   19篇
  1983年   25篇
  1982年   23篇
  1981年   25篇
  1980年   13篇
  1979年   21篇
  1977年   19篇
  1976年   20篇
  1975年   14篇
  1974年   23篇
  1973年   13篇
排序方式: 共有3678条查询结果,搜索用时 15 毫秒
101.
Abstract— The direct voltage programming of active‐matrix organic light‐emitting‐diode (AMOLED) pixels with n‐channel amorphous‐Si (a‐Si) TFTs requires a contact between the driving TFT and the OLED cathode. Current processing constraints only permit connecting the driving TFT to the OLED anode. Here, a new “inverted” integration technique which makes the direct programming possible by connecting the driver n‐channel a‐Si TFT to the OLED cathode is demonstrated. As a result, the pixel drive current increases by an order of magnitude for the same data voltages and the pixel data voltage for turn‐on drops by several volts. In addition, the pixel drive current becomes independent of the OLED characteristics so that OLED aging does not affect the pixel current. Furthermore, the new integration technique is modified to allow substrate rotation during OLED evaporation to improve the pixel yield and uniformity. The new integration technique is important for realizing active‐matrix OLED displays with a‐Si technology and conventional bottom‐anode OLEDs.  相似文献   
102.
27年前当我还是个学生的时候,我每周六都会去一家英格兰的首批电脑卖场打工。起初我觉得工作的每一天都很漫长,也几乎没有什么工资,但在那里我很享受于能使用到早期的第一代微型计算机,很快让自己变得非常充实起来。我还记得那时电脑卖场办了一个英文叫做“Easy Sell”的活动,  相似文献   
103.
104.
The efficiency of neuronal encoding in sensory and motor systems has been proposed as a first principle governing response properties within the central nervous system. We present a continuation of a theoretical study presented by Zhang and Sejnowski, where the influence of neuronal tuning properties on encoding accuracy is analyzed using information theory. When a finite stimulus space is considered, we show that the encoding accuracy improves with narrow tuning for one- and two-dimensional stimuli. For three dimensions and higher, there is an optimal tuning width.  相似文献   
105.
We study stochastic stability of centralized Kalman filtering for linear time-varying systems equipped with wireless sensors. Transmission is over fading channels where variable channel gains are counteracted by power control to alleviate the effects of packet drops. We establish sufficient conditions for the expected value of the Kalman filter covariance matrix to be exponentially bounded in norm. The conditions obtained are then used to formulate stabilizing power control policies which minimize the total sensor power budget. In deriving the optimal power control laws, both statistical channel information and full channel information are considered. The effect of system instability on the power budget is also investigated for both these cases.  相似文献   
106.
Oily cold rolling mill (CRM) sludge contains lots of iron and alloying elements along with plenty of hazardous organic components, which makes it as an attractive secondary source and an environmental contaminant at the same time. The compound methods of "vacuum distillation + oxidizing roasting" and "vacuum distillation + hydrogen reduction" were employed for the recycle of oily cold rolling mill sludge. First, the sludge was dynamically vacuum distilled in a rotating furnace at 50 r/rain and 600℃ for 3 h, which removed almost hazardous organic components, obtaining 89.2wt% ferrous resultant. Then, high purity ferric oxide powders (99.2wt%) and reduced iron powders (98.9wt%) were obtained when the distillation residues were oxidized and reduced, respectively. The distillation oil can be used for fuel or chemical feedstock, and the distillation gases can be collected and reused as a fuel.  相似文献   
107.
Most of the extraction processes developed for the polymetallic sea nodules concentrated mainly on the recovery of strategically important metals viz. Cu, Ni and Co. The residue generated in such processes is quite high enough to upset the environmental balance for industrial scale operation. The economics of the process too cannot be favourable if manganese in the residue is not recovered. In this study an attempt has been made to utilize this residue, containing appreciable amount of manganese (about 20%) for producing ferrosilicomanganese, an important ferroalloy primarily used for deoxidation in the steel industry, through smelting process. In order to have an alloy of standard grade, the residue is enriched in its manganese content, by blending it with ferromanganese slag. Bench scale studies indicate that it is possible to produce ferrosilicomanganese, of the grade required by the steel industry, by reduction smelting of the sea nodule residue with ferromanganese slag. Metal recovery, however, was less because of metal entrapment.  相似文献   
108.
This paper discusses the development of virtual structural analysis program (VSAP). This is a virtual environment (VE) based structural analysis system developed through a collaborative effort between the School of Architecture + Design and the Department of Computer Science at Virginia Polytechnic Institute and State Univ. (Virginia Tech). The VSAP was developed by linking a visualization routine using the simple VE library and a structural analysis software, the PC-SAP4. Details of the design of four user interfaces for the VSAP are presented. These user interfaces are: the immersive pen and tablet interface, the desktop interface, the portable immersive interface, and the cave automatic VE immersive interface. Usability studies for each interface were conducted. Results of these studies indicated that the users of VSAP were highly satisfied with the experience. In addition, all the developed interfaces were found to be successful for their specific application.  相似文献   
109.
The Changes in Outlook Questionnaire (CiOQ; S. Joseph, R. Williams, & W. Yule, 1993) is a 26-item self-report measure that was designed to assess positive and negative changes in the aftermath of adversity. This article had 3 aims: 1st, to investigate the factor structure of the CiOQ; 2nd, to test for internal consistency reliability and convergent and discriminant validity; and, 3rd, to investigate the association between positive and negative changes in outlook, posttraumatic stress, and psychological distress. Three studies are reported. Study 1 provides evidence that positive and negative changes are statistically separable and that the 2-factor model is a better fit than the 1-factor model. Studies 2 and 3 provide evidence for internal consistency reliability, convergent and discriminant validity of the CiOQ, and its associations with posttraumatic stress and psychological distress. In conclusion, the CiOQ has much promise for research on responses to stressful and traumatic events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
110.
We report remote detections of physically buried specularly reflecting objects using microwave radar at two sites: Ashalim and Tseelim in the northern region of the Negev Desert, Israel. These detections provide confirmation that microwave subsurface remote sensing is a genuine phenomenon. At Ashalim, a scatterometer operating in the P-band (441 MHz, 68 cm) was mounted on a cherry picker truck at a height of 8 m and used to detect two triangular aluminum mesh reflectors (forming a 1-m square area reflector) buried down to a depth of 8 cm in dry sand. At Tseelim, the same scatterometer was mounted on an airplane flying at an altitude of 70 m and used to detect 1-m square aluminum reflectors (each one submerged at a different location along the airplane flight path) buried down to a depth of 20 cm. The experimental results compare favorably with a theoretical model that incorporates radar absorption effects arising in the sandy subsurface layer and radar interference effects arising from phase differences between reflections from the surface and buried reflector. The theoretical modeling also predicts the detection of a subsurface reflector down to a depth of about 4.4 m. This experiment and the associated modeling approach is the first of a series of planned experiments, which we outline for the detection and the theoretical evaluation of buried reflectors using remote microwave and VHF radar. We identify potential subject areas for environmental research.  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