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   5797篇
  免费   587篇
  国内免费   222篇
电工技术   307篇
综合类   337篇
化学工业   1015篇
金属工艺   365篇
机械仪表   388篇
建筑科学   357篇
矿业工程   146篇
能源动力   177篇
轻工业   663篇
水利工程   99篇
石油天然气   153篇
武器工业   22篇
无线电   661篇
一般工业技术   747篇
冶金工业   327篇
原子能技术   81篇
自动化技术   761篇
  2024年   28篇
  2023年   116篇
  2022年   237篇
  2021年   285篇
  2020年   212篇
  2019年   150篇
  2018年   191篇
  2017年   192篇
  2016年   209篇
  2015年   253篇
  2014年   333篇
  2013年   423篇
  2012年   417篇
  2011年   441篇
  2010年   331篇
  2009年   359篇
  2008年   332篇
  2007年   284篇
  2006年   292篇
  2005年   219篇
  2004年   144篇
  2003年   168篇
  2002年   168篇
  2001年   139篇
  2000年   93篇
  1999年   85篇
  1998年   93篇
  1997年   54篇
  1996年   59篇
  1995年   62篇
  1994年   35篇
  1993年   35篇
  1992年   27篇
  1991年   23篇
  1990年   18篇
  1989年   13篇
  1988年   13篇
  1987年   9篇
  1986年   4篇
  1985年   3篇
  1984年   4篇
  1983年   6篇
  1981年   8篇
  1980年   6篇
  1977年   6篇
  1976年   6篇
  1975年   3篇
  1974年   3篇
  1969年   4篇
  1951年   2篇
排序方式: 共有6606条查询结果,搜索用时 0 毫秒
21.
Memory cost is responsible for a large amount of the chip and/or board area of customized video and image processing system realizations. In this paper, we present a novel technique-founded on data-flow analysis which allows one to address the problem of background memory size evaluation for a given nonprocedural algorithm specification, operating on multidimensional signals with affine indexes. Most of the target applications are characterized by a huge number of signals, so a new polyhedral data-flow model operating on groups of scalar signals is proposed. These groups are obtained by a novel analytical partitioning technique, allowing to select a desired granularity, depending on the application complexity. The method incorporates a way to tradeoff memory size with computational and controller complexity  相似文献   
22.
刍议小型水电站项目收购风险管理   总被引:1,自引:0,他引:1  
李曼 《小水电》2007,(3):9-11
相对于其他项目的收购风险评估,小型水电站(电站总装机容量5万kW以下)收购有其特殊性。在总结和归纳小型水电站特点的基础上,结合一般项目收购风险评估方法,分析项目收购各个阶段存在的风险和对策。为有收购水电项目意向的企业和个人提供决策依据。图1幅。  相似文献   
23.
Device degradation behaviors of typical-sized n-type metal-induced laterally crystallized polycrystalline silicon thin-film transistors were investigated in detail under two kinds of dc bias stresses: hot-carrier (HC) stress and self-heating (SH) stress. Under HC stress, device degradation is the consequence of HC induced defect generation locally at the drain side. Under a unified model that postulates, the establishment of a potential barrier at the drain side due to carrier transport near trap states, device degradation behavior such as asymmetric on current recovery and threshold voltage degradation can be understood. Under SH stress, a general degradation in subthreshold characteristic was observed. Device degradation is the consequence of deep state generation along the entire channel. Device degradation behaviors were compared in low Vd-stress and in high Vd-stress condition. Defect generation distribution along the channel appears to be different in two cases. In both cases of SH degradation, asymmetric on current recovery was observed. This observation, when in low Vd-stress condition, is tentatively explained by dehydrogenation (hydrogenation) effect at the drain (source) side during stress  相似文献   
24.
In this work, a model predictive control method combined with fuzzy identification, is applied to the design of the thermoelectric (TE) power control in the SP-100 space reactor. The future TE power is predicted by using the fuzzy model identified by a subtractive clustering method of a fast and robust algorithm. The objectives of the proposed fuzzy model predictive controller are to minimize both the difference between the predicted TE power and the desired power, and the variation of control drum angle that adjusts the control reactivity. Also, the objectives are subject to maximum and minimum control drum angle and maximum drum angle variation speed. The genetic algorithm that is effective in accomplishing multiple objectives is used to optimize the fuzzy model predictive controller. A lumped parameter simulation model of the SP-100 nuclear space reactor is used to verify the proposed controller. The results of numerical simulations to check the performance of the proposed controller show that the TE generator power level controlled by the proposed controller could track the target power level effectively, satisfying all control constraints.  相似文献   
25.
为使北京谱仪端盖族射计数器更好地工作在自猝灭流光SQS模式下,提高其能量分辨以及线性等指标,用Ar,CO2,Lsobutane三元工作气体对探测器的工作性能进行了仔细研究,找出了一适合于主雇地数器的工作气体,此外,还研究了异丁的纯度对探测器性能的影响。  相似文献   
26.
研究了65钢冷拔钢丝在500℃不同时间回火时的抗拉强度和延伸率的变化。试验结果发现,在回火初期,抗拉强度首先增长,然后随口火时间的延长连续降低,而延伸率始终在增长,增长速度是先快后慢。这种行为可归因于第一内应力的消除和ε-碳化物在形变铁素体中的析出以及后来再结晶的发生。  相似文献   
27.
This paper focuses on a method to integrate mobile devices such as a mobile robot, automated guided vehicle, and unmanned container transporter to form an automated material handling system. In this paper, the stationary devices are connected via a Profibus network while the mobile devices are communicating via an IEEE 802.11 wireless LAN. In order to integrate these two networks, a protocol converter is developed on a PC platform that runs two interacting processes with shared internal buffers. The protocol converter performs a role of translator between two different protocols by converting the format of a data frame. In addition to this basic conversion function, the protocol converter has a virtual polling algorithm to reduce the uncertainty involved in accessing the wireless network. Finally, the integrated network. of Profibus and IEEE 802.11 is experimentally evaluated for its data latency and throughput, which shows the feasibility of the Profibus-IEEE 802.11 network for industrial applications involving mobile devices  相似文献   
28.
OSMAR2000采用的是“一发八收,收发共用”模式的相控阵高频地波雷达.为了扩大其探测的范围,在新的雷达系统中将采用多发多收的模式,从而导致当信号通过通道后,信号的相位会因受到通道的调制而发生改变,使得雷达无法正常工作,因此需要对通道的相位进行实时监控和补偿.在参考了低频段的相位测量原理和射频段的相移电路的设计理论的基础上,该文提出了基于差分放大器、容阻和容感器件的高频地波雷达收发通道的相位控制系统.  相似文献   
29.
30.
A computer program to calculate the strip temperature heated in the continuous annealing furnace was developed, using the zone method for radiative heat transfer analysis with the measured gas temperature in the furnace. Using theF E Operator, the present study considered the effects of soot and transient species, in addition to the H2O−CO2 gas mixture on the gas radiative heat transfer. The predicted strip temperature distribution forF E=1.05 represented well the measured data. The maximum difference in the heat flux transfered to the strip from the combustion gas forF E=1.0 (without soot and transient species gas radiation) and 1.05 (with soot and transient species gas radiation) was about 15%. The present study also investigated the effects of line speed and thickness variations on the strip temperature, establishing the bases for the on-line computer model.  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