全文获取类型
收费全文 | 3857篇 |
免费 | 174篇 |
国内免费 | 381篇 |
专业分类
电工技术 | 66篇 |
技术理论 | 1篇 |
综合类 | 108篇 |
化学工业 | 357篇 |
金属工艺 | 78篇 |
机械仪表 | 185篇 |
建筑科学 | 318篇 |
矿业工程 | 75篇 |
能源动力 | 159篇 |
轻工业 | 648篇 |
水利工程 | 42篇 |
石油天然气 | 82篇 |
武器工业 | 13篇 |
无线电 | 410篇 |
一般工业技术 | 341篇 |
冶金工业 | 81篇 |
原子能技术 | 979篇 |
自动化技术 | 469篇 |
出版年
2024年 | 7篇 |
2023年 | 46篇 |
2022年 | 99篇 |
2021年 | 112篇 |
2020年 | 115篇 |
2019年 | 89篇 |
2018年 | 86篇 |
2017年 | 122篇 |
2016年 | 157篇 |
2015年 | 125篇 |
2014年 | 182篇 |
2013年 | 369篇 |
2012年 | 231篇 |
2011年 | 326篇 |
2010年 | 262篇 |
2009年 | 247篇 |
2008年 | 191篇 |
2007年 | 248篇 |
2006年 | 208篇 |
2005年 | 126篇 |
2004年 | 129篇 |
2003年 | 113篇 |
2002年 | 88篇 |
2001年 | 97篇 |
2000年 | 85篇 |
1999年 | 83篇 |
1998年 | 58篇 |
1997年 | 50篇 |
1996年 | 40篇 |
1995年 | 55篇 |
1994年 | 40篇 |
1993年 | 33篇 |
1992年 | 28篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 26篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1959年 | 4篇 |
排序方式: 共有4412条查询结果,搜索用时 31 毫秒
81.
In traditional scheduling problems, the processing time for the given job is assumed to be a constant regardless of whether the job is scheduled earlier or later. However, the phenomenon named “learning effect” has extensively been studied recently, in which job processing times decline as workers gain more experience. This paper discusses a bi-criteria scheduling problem in an m-machine permutation flowshop environment with varied learning effects on different machines. The objective of this paper is to minimize the weighted sum of the total completion time and the makespan. A dominance criterion and a lower bound are proposed to accelerate the branch-and-bound algorithm for deriving the optimal solution. In addition, the near-optimal solutions are derived by adapting two well-known heuristic algorithms. The computational experiments reveal that the proposed branch-and-bound algorithm can effectively deal with problems with up to 16 jobs, and the proposed heuristic algorithms can yield accurate near-optimal solutions. 相似文献
82.
The Aerial Refueling Scheduling Problem (ARSP) can be defined as determining the refueling completion times for fighter aircrafts (jobs) on multiple tankers (machines) to minimize the total weighted tardiness. ARSP can be modeled as a parallel machine scheduling with ready times and due date-to-deadline window to minimize total weighted tardiness. ARSP assumes that the jobs have different ready times and a due date-to-deadline window between refueling due date and a deadline to return without refueling. In this paper, we first formulate the ARSP as a mixed integer programming model. The objective function is a piece-wise tardiness cost that takes into account due date-to-deadline windows and job priorities. Since ARSP is NP-hard, two heuristics are proposed to obtain solutions in reasonable computation times, namely (1) modified ATC rule (MATC), (2) a simulated annealing method (SA). The proposed heuristic algorithms are tested in terms of solution quality and CPU time through computational experiments with data randomly generated to represent aerial refueling operations of an in-theater air operation. Solutions provided by both algorithms were compared to optimal solutions for problems with up to 12 jobs and to each other for larger problems with up to 60 jobs. The results show that, MATC is more likely to outperform SA especially when the problem size increases, although it has significantly worse performance than SA in terms of deviation from optimal solution for small size problems. Moreover CPU time performance of MATC is significantly better than SA in both cases. 相似文献
83.
Yunqiang Yin Chin-Chia Wu Wen-Hsiang WuShuenn-Ren Cheng 《Computers & Operations Research》2012,39(5):1109-1116
This study addresses the problem of minimizing the total weighted tardiness on a single-machine with a position-based learning effect. Several dominance properties are established to develop branch and bound algorithm and a lower bound is provided to derive the optimal solution. In addition, three heuristic procedures are developed for near-optimal solutions. Computational results are also presented to evaluate the performance of the proposed algorithms. 相似文献
84.
85.
刘雄斌 《江汉石油职工大学学报》2013,(6):100-103
江汉油田井下作业处按照全员参与、全面落实、多维管理的原则,事前计划、事中控制和事后分析相统一的原则,PDCA循环体系运转的原则,与全面预算管理互相融合的原则构建了全员成本目标管理体系。全员成本目标管理体系由“指标、执行、监控、考核”四个子体系构成。建立指标体系以明确管理目标;建立执行体系以落实管理指标;建立监控体系以及时发现问题、及时纠偏;建立考核体系以调动、激励员工投身成本管理。通过子体系的有效运行,持续提升成本管理水平。 相似文献
86.
采用生化分析方法研究了吡虫啉亚致死剂量对禾谷缢管蚜Rhopalosiphum padi(Lin-naeus)酯酶的时间效应。结果表明,吡虫啉亚致死剂量处理禾谷缢管蚜48 h内,随着处理时间延长,其体内酯酶活力呈现动态变化。在亚致死剂量处理6 h内,禾谷缢管蚜总酯酶活力和酯酶比活力逐渐下降至最低值;之后逐渐回升,但至48 h时酯酶活力仍未恢复到正常值,并且所有处理组酶活力均显著低于对照组。表明亚致死剂量吡虫啉对禾谷缢管蚜酯酶具有一定的抑制作用,同时具有时间效应。 相似文献
87.
Pakistan's bedwear industry contributes significantly to Pakistan's industry in general and to its textile industrial output and exports in particular. The exports of bedwear have increased steadily. However, its key basis of competitive advantage has been low cost. After greater liberalization from 2005 onwards and due to tariffication of quotas, the bedwear industry will not only have to scale higher tariff walls but will be more exposed to the threat of anti-dumping duties as it relies primarily on low prices to penetrate the export markets. To enhance its competitiveness, it will have to combine better quality with low costs and quick response. Research in quality management in Pakistan's bedwear industry was, therefore, undertaken. A postal self-completion questionnaire was mailed to 38 members of Pakistan Bedwear Manufacturers' and Exporters' Association (PBMEA). The response rate was almost 79%. It was found that this industrial segment was in various stages of development. This study demonstrates both the effectiveness and the limits of quality assurance in improving the levels of quality which remain a moving target in a dynamic liberalizing international trade environment that is more competitive since 2005. The bedwear industry, therefore, needs to graduate to advanced practices in quality management in order to remain competitive in rapidly changing times. 相似文献
88.
Fretting is associated with small amplitude oscillatory movements between two surfaces in contact. One possible consequence of fretting is the formation and subsequent growth of cracks at the edges of the contact. This paper presents an experimental investigation of the cracking behaviour under fretting loading of two different aluminium alloys: 2024-T351 and 7075-T651. Systematic and controlled experiments with a cylinder-flat contact under partial slip fretting conditions were carried out. A model which combines both crack nucleation and propagation processes is used to predict the crack extension throughout the life of the component. The direction of crack propagation experimentally observed was taken into account by the model. Furthermore, an analytical prediction of crack nucleation based on the process volume approach is made. The predictions of both crack extension and nucleation are compared with the experimental results, and show good agreement. 相似文献
89.
一种线路极限传输容量的在线计算方法 总被引:8,自引:1,他引:8
提出了一种电力系统在线极限传输容量的计算模型和实用化算法。这一模型基于发电计划和短期负荷预测来定义负荷发电增长方向,全面地考虑了系统在一个预想故障集下的暂态稳定约束、静态稳定约束、电压和支路潮流等静态运行约束。文中采用了一种考虑暂态稳定约束的连续潮流算法来求解,在充分利用连续潮流可以有效地计及静态稳定和安全约束的同时,采用快速时域仿真技术来处理暂态稳定约束。对一个300节点的实际系统和50个故障组成的故障集的应用表明,文中所提模型和算法是有效实用的。 相似文献
90.