全文获取类型
收费全文 | 19343篇 |
免费 | 2213篇 |
国内免费 | 1149篇 |
专业分类
电工技术 | 1503篇 |
技术理论 | 1篇 |
综合类 | 2157篇 |
化学工业 | 2103篇 |
金属工艺 | 998篇 |
机械仪表 | 1861篇 |
建筑科学 | 2207篇 |
矿业工程 | 563篇 |
能源动力 | 344篇 |
轻工业 | 788篇 |
水利工程 | 411篇 |
石油天然气 | 1581篇 |
武器工业 | 317篇 |
无线电 | 1900篇 |
一般工业技术 | 2329篇 |
冶金工业 | 500篇 |
原子能技术 | 89篇 |
自动化技术 | 3053篇 |
出版年
2024年 | 89篇 |
2023年 | 391篇 |
2022年 | 481篇 |
2021年 | 643篇 |
2020年 | 721篇 |
2019年 | 645篇 |
2018年 | 631篇 |
2017年 | 732篇 |
2016年 | 739篇 |
2015年 | 745篇 |
2014年 | 1134篇 |
2013年 | 1016篇 |
2012年 | 1252篇 |
2011年 | 1236篇 |
2010年 | 1037篇 |
2009年 | 1067篇 |
2008年 | 987篇 |
2007年 | 1328篇 |
2006年 | 1092篇 |
2005年 | 965篇 |
2004年 | 872篇 |
2003年 | 811篇 |
2002年 | 643篇 |
2001年 | 635篇 |
2000年 | 498篇 |
1999年 | 463篇 |
1998年 | 375篇 |
1997年 | 309篇 |
1996年 | 256篇 |
1995年 | 190篇 |
1994年 | 145篇 |
1993年 | 122篇 |
1992年 | 110篇 |
1991年 | 80篇 |
1990年 | 45篇 |
1989年 | 66篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Antonio Camurri Paolo Franchi Francesca Gandolfo Renato Zaccaria 《Journal of Intelligent and Robotic Systems》1993,8(1):99-123
In this paper, we propose a class of algorithms for the sub-optimal solution of a particular class of problems of process scheduling, particularly focusing on a case study in the area of flexible manufacturing systems (FMSs). The general class of problems we face in our approach is characterized as follows: there is a set of concurrent processes, each formed by a number of temporally related tasks (segments). Tasks are executable by alternate resource sets, different both in performance and costs. Processes and tasks are characterized by release times, due dates, and deadlines. Time constraints are also present in the availability of each resource in resource sets. It has been proven that such a problem does not admit an algorithm for an optimal solution in polynomial time. Our proposed algorithm finds a sub-optimal schedule according to a set of optimization criteria, based on task and process times (earliness, tardiness), and/or time independent costs of resources. Our approach to process scheduling is based on Timed Coloured Petri Nets. We describe the structure of the coordination and scheduling algorithms, concentrating on (i) the general-purpose component, and (ii) the application-dependent component. In particular, the paper focuses on the following issues: (i) theautomatic synthesis of Petri net models of the coordination subsystem, starting from the problem knowledge base; (ii) the dynamic behavior of the coordination subsystem, whose kernel is a High Level Petri net executor, a coordination process based on an original, general purpose algorithm; (iii) the structure of the real-time scheduling subsystem, based on particular heuristic sub-optimal multi-criteria algorithms. Furthermore, the paper defines the interaction mechanisms between the coordination and scheduling subsystems. Our approach clearly distinguishes the mechanism of the net execution from the decision support system. Two conceptually distinct levels, which correspond to two different, interacting implementation modules in the prototype CASE tool, have been defined: theexecutor and thescheduler levels. One of the outstanding differences between these levels is that the executor is conceived as a fast, efficient coordination process, without special-purpose problem-solving capabilities in case of conflicts. The scheduler, on the other hand, is the adaptive, distributed component, whose behavior may heavily depend on the problem class. If the scheduler fails, the executor is, in any case, able to proceed with a general-purpose conflict resolution strategy. Experimental results on the real-time performance of the kernel of the implemented system are finally shown in the paper. The approach described in this paper is at the basis of a joint project with industrial partners for the development of a CASE tool for the simulation of blast furnaces. 相似文献
52.
陈籁民 《建筑科学与工程学报》1996,(2)
基圆半径的确定方法,除了用图解法和试算法外,还可用解析法和图解分析法求解。4种方法各有优缺点,设计时要根据具体情况选择。 相似文献
53.
介绍85W/90卡车手动变速箱油的组分和添加剂,提出符合85W/90粘度级别的基础油,讨论影响85W/90卡车手动变速箱油性能的各种因素,给出符合85W/90卡车手动变速箱油规格的油品配方。 相似文献
54.
55.
56.
Sidhartha R. Das Basheer M. Khumawala 《International Journal of Flexible Manufacturing Systems》1991,3(2):121-147
Flexible manufacturing systems (FMSs) are a class of automated systems that can be used to improve productivity in batch manufacturing. Four stages of decision making have been defined for an FMS—the design, planning, scheduling, and control stages. This research focuses on the planning stage, and specifically in the area of scheduling batches of parts through the system.The literature to date on the FMS planning stage has mostly focused on the machine grouping, tool loading, and parttype selection problems. Our research carries the literature a step further by addressing the problem of scheduling batches of parts. Due to the use of serial-access material-handling systems in many FMSs, the batch-scheduling problem is modeled for a flexible flow system (FFS). This model explicitly accounts for setup times between batches that are dependent on their processing sequence.A heuristic procedure is developed for this batch-scheduling problem—the Maximum Savings (MS) heuristic. The MS heuristic is based upon the savings in time associated with a particular sequence and selecting the one with the maximum savings. It uses a two-phase method, with the savings being calculated in phase I, while a branch-and-bound procedure is employed to seek the best heuristic solution in phase II. Extensive computational results are provided for a wide variety of problems. The results show that the MS heuristic provides good-quality solutions. 相似文献
57.
58.
59.
指出湖滨带是连接湖泊水体和陆地的一个功能过渡界面区。它作为生物的重要栖息地,具有净化水质、缓解波浪等多种功能。因此,对湖滨带实行生态恢复建设,应予以高度的重视。笔者通过具体工程的实践,阐述了湖滨带生态恢复建设工程的特点、施工阶段的监理工作,以及对监理人员的素质要求,可供类似工程借鉴、参考。 相似文献
60.
根据电加热柔性连续抽油杆的特性、参数及井下基本工况,建立了三级混合抽油杆柱的有限元模型。运用有限元软件对混合杆柱的动态特性进行计算机模拟,得到各关键点位移、速度随时间变化曲线,以及计算机模拟的地面示功图,为抽油机、抽油杆设计和井下故障诊断提供理论依据。与传统电加热空心抽油杆相比,电加热柔性连续抽油杆在降载和节能方面优势显著。 相似文献