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   389635篇
  免费   28964篇
  国内免费   17689篇
电工技术   22979篇
技术理论   59篇
综合类   47739篇
化学工业   38581篇
金属工艺   14980篇
机械仪表   27908篇
建筑科学   63612篇
矿业工程   18525篇
能源动力   10838篇
轻工业   20649篇
水利工程   17343篇
石油天然气   15876篇
武器工业   3927篇
无线电   26013篇
一般工业技术   32136篇
冶金工业   18009篇
原子能技术   3354篇
自动化技术   53760篇
  2024年   1091篇
  2023年   3788篇
  2022年   6803篇
  2021年   8745篇
  2020年   9122篇
  2019年   7475篇
  2018年   7104篇
  2017年   8599篇
  2016年   10237篇
  2015年   11509篇
  2014年   23484篇
  2013年   20454篇
  2012年   26339篇
  2011年   28227篇
  2010年   22852篇
  2009年   23859篇
  2008年   22076篇
  2007年   28098篇
  2006年   25718篇
  2005年   22451篇
  2004年   18911篇
  2003年   17184篇
  2002年   14029篇
  2001年   11800篇
  2000年   9905篇
  1999年   8011篇
  1998年   6219篇
  1997年   5341篇
  1996年   4850篇
  1995年   4060篇
  1994年   3547篇
  1993年   2624篇
  1992年   2237篇
  1991年   1707篇
  1990年   1406篇
  1989年   1267篇
  1988年   989篇
  1987年   700篇
  1986年   492篇
  1985年   471篇
  1984年   464篇
  1983年   332篇
  1982年   322篇
  1981年   203篇
  1980年   176篇
  1979年   144篇
  1978年   82篇
  1977年   91篇
  1976年   63篇
  1975年   65篇
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
61.
This short communication presents a generic mathematical programming formulation for computer-aided molecular design (CAMD). A given CAMD problem, based on target properties, is formulated as a mixed integer linear/non-linear program (MILP/MINLP). The mathematical programming model presented here, which is formulated as an MILP/MINLP problem, considers first-order and second-order molecular groups for molecular structure representation and property estimation. It is shown that various CAMD problems can be formulated and solved through this model.  相似文献   
62.
This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.  相似文献   
63.
来水利 《云南化工》2019,(7):180-181
有机化学是化学化工、材料、制药、食品等多个专业的基础课程,在其教学过程中,教师可以根据课程的内容及特点,分别以有机化学发展中的重大历史事件、有机化物的性质及有机反应为引导,开展学生的思想品德教育,加强课程思政建设。  相似文献   
64.
65.
To improve the convertibility of reconfigurable manufacturing system (RMS), the concept of delayed reconfigurable manufacturing system (D-RMS) was proposed. RMS and D-RMS are both constructed around part family. However, D-RMS may suffer from ultra-long system problem with unacceptable idle machines using generic RMS part families. Besides, considering the complex basic system structure of D-RMS, machine selection of D-RMS should be addressed, including dedicated machine, flexible machine, and reconfigurable machine. Therefore, a system design method for D-RMS based on part family grouping and machine selection is proposed. Firstly, a part family grouping method is proposed for D-RMS that groups the parts with more former common operations into the same part family. The concept of longest relative position common operation subsequence (LPCS) is proposed. The similarity coefficient among the parts is calculated based on LPCS. The reciprocal value of the operation position of LPCS is adopted as the characteristic value. The average linkage clustering (ALC) algorithm is used to cluster the parts. Secondly, a machine selection method is proposed to complete the system design of D-RMS, including machine selection rules and the dividing point decision model. Finally, a case study is given to implement and verify the proposed system design method for D-RMS. The results show that the proposed system design method is effective, which can group parts with more former common operations into the same part family and select appropriate machine types.  相似文献   
66.
Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.  相似文献   
67.
ABSTRACT

Health self-management technology has the potential to significantly improve the Quality of Life of patients suffering from chronic diseases. However, designing the technology involves numerous highly context-dependent design decisions. In this paper, we analyse a case study of self-monitoring technology in the field of congestive heart failure. We analyse the design process of the technology from the perspective of design trade-offs. Three important trade-offs related to health self-monitoring technology are described in detail, related to patient autonomy, technology appropriation, and patient well-being. For each of the trade-offs, various mediating factors that influence design decisions are described in detail. On a practical level, this analysis can inform future developments in self-management technology. In addition, this design trade-off analysis provides intermediary knowledge that can contribute to a better theoretical understanding of health self-management technology.  相似文献   
68.
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。  相似文献   
69.
70.
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