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   5066篇
  免费   149篇
  国内免费   38篇
电工技术   93篇
综合类   5篇
化学工业   952篇
金属工艺   122篇
机械仪表   199篇
建筑科学   97篇
能源动力   193篇
轻工业   231篇
水利工程   26篇
石油天然气   4篇
无线电   902篇
一般工业技术   913篇
冶金工业   564篇
原子能技术   25篇
自动化技术   927篇
  2023年   27篇
  2022年   76篇
  2021年   108篇
  2020年   35篇
  2019年   56篇
  2018年   66篇
  2017年   76篇
  2016年   101篇
  2015年   101篇
  2014年   177篇
  2013年   374篇
  2012年   269篇
  2011年   323篇
  2010年   232篇
  2009年   266篇
  2008年   271篇
  2007年   241篇
  2006年   229篇
  2005年   197篇
  2004年   162篇
  2003年   157篇
  2002年   126篇
  2001年   116篇
  2000年   86篇
  1999年   99篇
  1998年   250篇
  1997年   150篇
  1996年   114篇
  1995年   72篇
  1994年   96篇
  1993年   61篇
  1992年   45篇
  1991年   54篇
  1990年   36篇
  1989年   45篇
  1988年   53篇
  1987年   39篇
  1986年   32篇
  1985年   24篇
  1984年   28篇
  1983年   24篇
  1982年   11篇
  1981年   16篇
  1980年   15篇
  1979年   9篇
  1978年   12篇
  1977年   18篇
  1976年   34篇
  1975年   6篇
  1974年   7篇
排序方式: 共有5253条查询结果,搜索用时 109 毫秒
171.
172.
A modified circular harmonic filter may be used for the rotation-invariant discrimination of a target from another object which contains the same pattern as the target. The method is illustrated by the experimental rotation-invariant detection of the letter F in the presence of the letter E.  相似文献   
173.
Hsu SH  Wu SP 《Applied ergonomics》1991,22(6):395-400
Chopsticks are one of the most simple and popular hand tools ever invented by humans, but have not previously been investigated by ergonomists. Two laboratory studies were conducted in this research, using a randomised complete block design, to evaluate the effects of the length of the chopsticks on the food-serving performance of adults and children. Thirty-one male junior college students and 21 primary school pupils served as subjects for the experiment. The results showed that the food-pinching performance was significantly affected by the length of the chopsticks, and that chopsticks of about 240 and 180 mm long were optimal for adults and pupils, respectively. Based on these findings, the researchers suggested that families with children should provide both 240 and 180 mm long chopsticks. In addition, restaurants could provide 210 mm long chopsticks, considering the trade-offs between ergonomics and cost.  相似文献   
174.
Water shortage has become an emerging environmental issue. Reclamation of the effluent from municipal wastewater treatment plant (WWTP) is feasible for meeting the growth of water requirement from industries. In this study, the results of a pilot-plant setting in Futian wastewater treatment plant (Taichung, Taiwan) were presented. Two processes, sand filter - ultrafiltration - reverse osmosis (SF-UF-RO) and sand filter - electrodialysis reversal (SF-EDR), were operated in parallel to evaluate their stability and filtrate quality. It has been noticed that EDR could accept inflow with worse quality and thus required less pretreatment compared with RO. During the operation, EDR required more frequent chemical cleaning (every 3 weeks) than RO did (every 3 months). For the filtrate quality, the desalination efficiency of SF-EDR ranged from 75 to 80% in continuous operation mode, while the conductivity ranged from 100 to 120 μS/cm, with turbidity at 0.8 NTU and total organic carbon at 1.3 mg/L. SF-EDR was less efficient in desalinating the multivalent ions than SF-UF-RO was. However for the monovalent ions, the performances of the two processes were similar to each other. Noticeably, total trihalomethanes in SF-EDR filtrate was lower than that of SF-UF-RO, probably because the polarization effects formed on the concentrated side of the EDR membrane were not significant. At the end of this study, cost analysis was also conducted to compare the capital requirement of building a full-scale wastewater reclamation plant using the two processes. The results showed that using SF-EDR may cost less than using SF-UF-RO, if the users were to accept the filtrate quality of SF-EDR.  相似文献   
175.
In this note, we prove that both problems studied by Cheng et al. [Cheng, T. C. E., Hsu, C.-J., & Yang, D.-L. (2011). Unrelated parallel-machine scheduling with deteriorating maintenance activities. Computers and Industrial Engineering, 60, 602–605] can be solved in O(nm+3) time no matter what the processing time of a job after a maintenance activity is greater or less than its processing time before the maintenance activity, where m is the number of machines and n is the number of jobs.  相似文献   
176.
Recovery of online service is an issue in need of study. The current study empirically examines (1) the relationships among perceived justice, satisfaction with recovery of online service and repurchase intention of online service/failure encounters; and (2) the moderating effects of transaction frequency on these relationships. The current study collects 187 self-administered questionnaires to gather customers’ perceptions of actual online service/failure encounters. Research findings demonstrate that distributive justice, interactional justice and procedural justice can positively lead to satisfaction with recovery of online service and repurchase intention toward online service. These results further show that customers with low transaction frequency tend to focus more on interactional justice to establish their satisfaction with recovery of online service. On the other hand, customers with high transaction frequency focus more on procedural justice.  相似文献   
177.
This paper proposes a method to detect slip-only events and fall events based on the motion activity measure and human silhouette shape variations. Here, we also apply the Bayesian Belief Network (BBN) to model the causality of the events before and after the fall and slip-only events. The motion measure is obtained by analyzing the energy of the motion active (MA) area in the integrated spatiotemporal energy (ISTE) map. Unlike the motion history image (MHI), the ISTE map can be applied to detect fall and slip-only events. The contributions of this study are: (a) proposing the ISTE map; (b) detecting the fall parallel to the optical axis; (c) application to non-fixed frame rate video; (d) identifying the slip-only event; and (e) using BBN to model the causality of the slip or fall events with other events. Early identification of a slip-only event can help prevent falls and injuries. In the experiments, we demonstrate that our method is effective in detecting both fall and slip-only events.  相似文献   
178.
I‐Ching Hsu 《Software》2012,42(10):1211-1227
Web 2.0 Mashups offer entirely new opportunities for context‐aware application (CAA) developers by integrating Web 2.0 technologies to facilitate interoperability among heterogeneous context‐aware systems. From a software engineering perspective, a visualized approach for Web 2.0‐based CAA modeling is crucial. Current CAA development, however, cannot provide a conceptual model for Web 2.0‐based CAA. Therefore, the development efficiency and potential for reuse are decreased. The UML is a general purpose modeling language with potential for use in many application domains. However, UML often lacks elements needed to model concepts in specific domains, such as Web 2.0‐based CAA modeling. To address the above issues, this study presents the Web 2.0‐based CAA UML profile, a UML profile for modeling Web 2.0‐based CAA. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
179.
Though the control performances of the fuzzy neural network controller are acceptable in many previous published papers, the applications are only parameter learning in which the parameters of fuzzy rules are adjusted but the number of fuzzy rules should be determined by some trials. In this paper, a Takagi–Sugeno-Kang (TSK)-type self-organizing fuzzy neural network (TSK-SOFNN) is studied. The learning algorithm of the proposed TSK-SOFNN not only automatically generates and prunes the fuzzy rules of TSK-SOFNN but also adjusts the parameters of existing fuzzy rules in TSK-SOFNN. Then, an adaptive self-organizing fuzzy neural network controller (ASOFNNC) system composed of a neural controller and a smooth compensator is proposed. The neural controller using the TSK-SOFNN is designed to approximate an ideal controller, and the smooth compensator is designed to dispel the approximation error between the ideal controller and the neural controller. Moreover, a proportional-integral (PI) type parameter tuning mechanism is derived based on the Lyapunov stability theory, thus not only the system stability can be achieved but also the convergence of tracking error can be speeded up. Finally, the proposed ASOFNNC system is applied to a chaotic system. The simulation results verify the system stabilization, favorable tracking performance, and no chattering phenomena can be achieved using the proposed ASOFNNC system.  相似文献   
180.
The advantage of using cerebellar model articulation control (CMAC) network has been well documented in many applications. However, the structure of a CMAC network which will influence the learning performance is difficult to select. This paper proposes a dynamic structure CMAC network (DSCN) which the network structure can grow or prune systematically and their parameters can be adjusted automatically. Then, an adaptive dynamic CMAC neural control (ADCNC) system which is composed of a computation controller and a robust compensator is proposed via second-order sliding-mode approach. The computation controller containing a DSCN identifier is the principal controller and the robust compensator is designed to achieve L2 tracking performance with a desired attenuation level. Moreover, a proportional–integral (PI)-type adaptation learning algorithm is derived to speed up the convergence of the tracking error in the sense of Lyapunov function and Barbalat’s lemma, thus the system stability can be guaranteed. Finally, the proposed ADCNC system is applied to control a chaotic system. The simulation results are demonstrated that the proposed ADCNC scheme can achieve a favorable control performance even under the variations of system parameters and initial point.  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