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   32957篇
  免费   2872篇
  国内免费   1724篇
电工技术   3611篇
技术理论   6篇
综合类   2717篇
化学工业   1100篇
金属工艺   676篇
机械仪表   2438篇
建筑科学   10367篇
矿业工程   837篇
能源动力   739篇
轻工业   825篇
水利工程   1163篇
石油天然气   410篇
武器工业   322篇
无线电   1467篇
一般工业技术   2885篇
冶金工业   751篇
原子能技术   246篇
自动化技术   6993篇
  2024年   187篇
  2023年   476篇
  2022年   835篇
  2021年   966篇
  2020年   1206篇
  2019年   957篇
  2018年   846篇
  2017年   1155篇
  2016年   1183篇
  2015年   1305篇
  2014年   2464篇
  2013年   2843篇
  2012年   2140篇
  2011年   2374篇
  2010年   1823篇
  2009年   2001篇
  2008年   1831篇
  2007年   2149篇
  2006年   1894篇
  2005年   1580篇
  2004年   1276篇
  2003年   1062篇
  2002年   954篇
  2001年   797篇
  2000年   669篇
  1999年   489篇
  1998年   371篇
  1997年   319篇
  1996年   258篇
  1995年   233篇
  1994年   200篇
  1993年   146篇
  1992年   101篇
  1991年   92篇
  1990年   70篇
  1989年   52篇
  1988年   41篇
  1987年   32篇
  1986年   17篇
  1985年   44篇
  1984年   25篇
  1983年   29篇
  1982年   17篇
  1981年   4篇
  1980年   8篇
  1979年   12篇
  1964年   2篇
  1963年   2篇
  1959年   5篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Although rainfall input uncertainties are widely identified as being a key factor in hydrological models, the rainfall uncertainty is typically not included in the parameter identification and model output uncertainty analysis of complex distributed models such as SWAT and in maritime climate zones. This paper presents a methodology to assess the uncertainty of semi-distributed hydrological models by including, in addition to a list of model parameters, additional unknown factors in the calibration algorithm to account for the rainfall uncertainty (using multiplication factors for each separately identified rainfall event) and for the heteroscedastic nature of the errors of the stream flow. We used the Differential Evolution Adaptive Metropolis algorithm (DREAM(zs)) to infer the parameter posterior distributions and the output uncertainties of a SWAT model of the River Senne (Belgium). Explicitly considering heteroscedasticity and rainfall uncertainty leads to more realistic parameter values, better representation of water balance components and prediction uncertainty intervals.  相似文献   
2.
WRESTORE (Watershed Restoration Using Spatio-Temporal Optimization of Resources) is a web-based, participatory planning tool that can be used to engage with watershed stakeholder communities, and involve them in using science-based, human-guided, interactive simulation–optimization methods for designing potential conservation practices on their landscape. The underlying optimization algorithms, process simulation models, and interfaces allow users to not only spatially optimize the locations and types of new conservation practices based on quantifiable goals estimated by the dynamic simulation models, but also to include their personal subjective and/or unquantifiable criteria in the location and design of these practices. In this paper, we describe the software, interfaces, and architecture of WRESTORE, provide scenarios for implementing the WRESTORE tool in a watershed community's planning process, and discuss considerations for future developments.  相似文献   
3.
An organization requires performing readiness-relevant activities to ensure successful implementation of an enterprise resource planning (ERP) system. This paper develops a novel approach to managing these interrelated activities to get ready for implementing an ERP system. The approach enables an organization to evaluate its ERP implementation readiness by assessing the degree to which it can achieve the interrelated readiness relevant activities using fuzzy cognitive maps. Based on the interrelationship degrees among the activities, the approach clusters the activities into manageable groups and prioritizes them. To help work out a readiness improvement plan, scenario analysis is conducted.  相似文献   
4.
Optimization of tool path planning using metaheuristic algorithms such as ant colony systems (ACS) and particle swarm optimization (PSO) provides a feasible approach to reduce geometrical machining errors in 5-axis flank machining of ruled surfaces. The optimal solutions of these algorithms exhibit an unsatisfactory quality in a high-dimensional search space. In this study, various algorithms derived from the electromagnetism-like mechanism (EM) were applied. The test results of representative surfaces showed that all EM-based methods yield more effective optimal solutions than does PSO, despite a longer search time. A new EM-MSS (electromagnetism-like mechanism with move solution screening) algorithm produces the most favorable results by ensuring the continuous improvement of new searches. Incorporating an SPSA (simultaneous perturbation stochastic approximation) technique further improves the search results with effective initial solutions. This work enhances the practical values of tool path planning by providing a satisfactory machining quality.  相似文献   
5.
BDI模型能够很好地解决在特定环境下的Agent的推理和决策问题,但在动态和不确定环境下缺少决策和学习的能力。强化学习解决了Agent在未知环境下的决策问题,却缺少BDI模型中的规则描述和逻辑推理。针对BDI在未知和动态环境下的策略规划问题,提出基于强化学习Q-learning算法来实现BDI Agent学习和规划的方法,并针对BDI的实现模型ASL的决策机制做出了改进,最后在ASL的仿真平台Jason上建立了迷宫的仿真,仿真实验表明,在加入Q-learning学习机制后的新的ASL系统中,Agent在不确定环境下依然可以完成任务。  相似文献   
6.
7.
8.
江澄 《山西建筑》2006,32(4):42-43
从政策、城市与区域规划、环境、文化及其传承因素、基础设施等方面探析了高校新校区选址有关的主要影响因素,以满足高等学校大规模的扩建要求,促进高等教育的发展。  相似文献   
9.
移动机器人路径规划方法研究   总被引:3,自引:0,他引:3  
董宇欣 《信息技术》2006,30(6):108-111
移动机器人技术研究中的一个重要领域是路径规划技术,它分为基于模型的环境已知的全局路径规划和基于传感器的环境未知的局部路径规划。综述了移动机器人路径规划技术的发展现状指出了各种方法的优点与不足,最后对移动机器人路径规划技术的发展趋势进行了展望。  相似文献   
10.
The effects of parameter uncertainty on optimal policy have been a matter of interest for academics, and even for some policymakers, for a long time. Two lines of literature have developed analytical results on this matter. The first line uses static models and the second dynamic models. In this dynamic line most of the results are confined to models with a single state and a single control variable. In this paper we want to encourage the analysis of more general dynamic cases. To do so, the results in the dynamic line are extended from one-state and one-control finite horizon models to models with a pair of control variables. We then discuss some of the hurdles which must be surmounted for the results to be made more general and suggests some lines for further research. JEL classification: C61; E61  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