全文获取类型
收费全文 | 943篇 |
免费 | 34篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 20篇 |
综合类 | 42篇 |
化学工业 | 51篇 |
金属工艺 | 5篇 |
机械仪表 | 24篇 |
建筑科学 | 175篇 |
矿业工程 | 49篇 |
能源动力 | 119篇 |
轻工业 | 13篇 |
水利工程 | 4篇 |
石油天然气 | 35篇 |
武器工业 | 7篇 |
无线电 | 32篇 |
一般工业技术 | 83篇 |
冶金工业 | 49篇 |
原子能技术 | 16篇 |
自动化技术 | 290篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 38篇 |
2014年 | 62篇 |
2013年 | 70篇 |
2012年 | 87篇 |
2011年 | 80篇 |
2010年 | 51篇 |
2009年 | 65篇 |
2008年 | 62篇 |
2007年 | 57篇 |
2006年 | 76篇 |
2005年 | 46篇 |
2004年 | 41篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有1014条查询结果,搜索用时 15 毫秒
21.
运输问题的神经网络解法 总被引:6,自引:0,他引:6
给出了利用Hopfield连续模型求解运输问题的数值算法,是对运筹学知识的补充和完善,是借助人工神经网络计算机原理解决组合优化问题的一个成功范例。 相似文献
22.
《国际计算机数学杂志》2012,89(11):1373-1383
In this study, a circularization network flow problem with m?+?n?+?2 nodes and (m?+?1)(n?+?1) arcs is described as a planar four-index transportation problem of order 1?×?m?×?n?×?1. Construction and several algebraic characterizations of the planar four-index transportation problem of order 1?×?m?×?n?×?1 are investigated using the generalized inverse and singular value decomposition of its coefficient matrix. The results are compared with some results we obtained on the transportation problem with m sources and n destinations. It is shown that these problems can be solved in terms of eigenvectors of the matrices J m and J n , where J m is a m?×?m matrix whose entries are 1. 相似文献
23.
区域经济的发展是运输需求的源泉。新世纪以来,江西经济进入了持续稳定发展的快车道,极大地促进了运输需求的持续增长,运输线路长度不断延长,全社会运输量不断增加。随着江西经济社会快速发展,城镇化进程的加快,资源环境约束压力的加大,运输需求结构提升,对运输需求提出了更高的要求,运输需求多样化、个性化、机动化、快速化和网络化的趋势更加显著。 相似文献
24.
《Ergonomics》2012,55(7):1033-1041
Nocturnal sleep was assessed electroencephalographically in 9 males aged between 29 and 48 (mean 36·5) years in bed and in three seats with back angles to the vertical of 49·5° (sleeperette), 37·0° (reclining seat) and 17·5° (armchair). Sleep in the sleeperette did not differ from that in bed, but in the reclining seat the duration of sleep was reduced and the amount of awake activity was increased. Sleep in the armchair was markedly worse than in any of the other three conditions. Total sleep time was shorter and awake activity was increased with more awakenings. Sleep efficiency was also reduced. It would appear that adequate sleep may be obtained in seats as long as the back angle with the vertical approaches 40°. 相似文献
25.
习家口油田单井管线腐蚀严重,经常发生管线穿口事故。由于伴生气量少,翻斗计量工艺无法运行。针对这种情况采用流量计计井口计量和树杖状串联常温集输工艺,降低了能耗,避免了运输油过程中的烃类气体的排放,减少了环境污染。据统计,习家口油田年减少烃类气体挥发100万方左右,生产运行费用大幅降低,取得了较好的经济效益。 相似文献
26.
Mehrdad Kargari Mohammad Mehdi Sepehri 《Expert systems with applications》2012,39(5):4740-4748
Clustering of retail stores in a distribution network with specific geographical limits plays an important and effective role in distribution and transportation costs reduction. In this paper, the relevant data and information for an established automotive spare-parts distribution and after-sales services company (ISACO) for a 3-year period have been analyzed. With respect to the diversity and lot size of the available information such as stores location, order, goods, transportation vehicles and road and traffic information, three effecting factors with specific weights have been defined for the similarity function: 1. Euclidean distance, 2. Lot size 3. Order concurrency. Based on these three factors, the similarity function has been examined through 5 steps using the Association Rules principles, where the clustering of the stores is performed using k-means algorithm and similar stores are allocated to the clusters. These steps include: 1. Similarity function based on the Euclidean distances, 2. Similarity function based on the order concurrency, 3. Similarity function based on the combination of the order concurrency and lot size, 4. Similarity function based on the combination of these three factors and 5. Improved similarity function. The above mentioned clustering operation for each 5 cases addressed in data mining have been carried out using R software and the improved combinational function has been chosen as the optimal clustering function. Then, trend of each retail store have been analyzed using the improved combinational function and along with determining the priority of the depot center establishment for every cluster, the appropriate distribution policies have been formulated for every cluster. The obtained results of this study indicate a significant cost reduction (32%) in automotive spare-parts distribution and transportation costs. 相似文献
27.
Selecting the best transportation investment project (TIP) is often a difficult task, since many social, environmental and economic criteria have to be considered simultaneously. Evaluating a set of different projects, especially the best set of alternatives, portfolios, is even more complex. Pursuing the goal of selecting the best TIP portfolio, we propose a fuzzy assessment method to aid the selection process of a multi-criterion project by utilizing the concept of entropy and interval normalization procedure in a fuzzy analytic hierarchy process (F-AHP). Then, regarding this informative phase, we propose a fuzzy linear programming model to select the best TIP portfolio under uncertain cost pressure. A real case study is conducted to illustrate the efficiency of the proposed method. 相似文献
28.
基于GSM GPS短消息的车载移动终端的设计与实现 总被引:3,自引:0,他引:3
为了解决对城市车辆进行实时监督和统一管理的问题,基于GPS全球定位系统和GSM数字蜂窝网,以性价比较高的AVR微控制器开发设计了GPS车载移动终端设备.终端通过GPS获取当前位置和时间信息,并以短消息的形式通过GSM网络发往监控中心,在中心的电子地图上实时地显示出来.同时监控中心的控制指令,如跟踪监听,遥控设置等,通过GSM网络发往车辆上的终端设备,从而实现了系统的交互运作.终端功耗低,体积小,操作简单,便于在系统升级和维护. 相似文献
29.
出租车管理系统与交通公共信息平台数据交换方式研究 总被引:1,自引:0,他引:1
杨涛 《数字社区&智能家居》2005,(10):55-56
本文以上海大众交通(集团)有限公司提供的出租车GPS数据为基础,通过对源数据进行过滤和处理,满足了交通公共信息平台数据应用要求,实现了交通管理和建设所需要数据的提取,提高了交通资源的利用率. 相似文献
30.
In this paper, we present a new approach which is spanning tree-based genetic algorithm for bicriteria transportation problem. The transportation problem have the special data structure in solution characterized as a spanning tree. In encoding transportation problem, we introduce one of node encoding which is adopted as it is capable of equally and uniquely representing all possible basic solutions. The crossover and mutation was designed based on this encoding. And we designed the criterion that chromosome always feasibility converted to a transportation tree. In the evolutionary process, the mixed strategy and roulette wheel selection is used. Numerical experiments will be shown the effectiveness and efficiency of the proposed algorithm. 相似文献