全文获取类型
收费全文 | 117026篇 |
免费 | 19417篇 |
国内免费 | 12749篇 |
专业分类
电工技术 | 14114篇 |
技术理论 | 3篇 |
综合类 | 13471篇 |
化学工业 | 6125篇 |
金属工艺 | 3175篇 |
机械仪表 | 10160篇 |
建筑科学 | 3703篇 |
矿业工程 | 2864篇 |
能源动力 | 4069篇 |
轻工业 | 4273篇 |
水利工程 | 2444篇 |
石油天然气 | 3207篇 |
武器工业 | 1824篇 |
无线电 | 15973篇 |
一般工业技术 | 8750篇 |
冶金工业 | 2232篇 |
原子能技术 | 501篇 |
自动化技术 | 52304篇 |
出版年
2024年 | 980篇 |
2023年 | 2458篇 |
2022年 | 4383篇 |
2021年 | 4763篇 |
2020年 | 5267篇 |
2019年 | 4421篇 |
2018年 | 4203篇 |
2017年 | 4993篇 |
2016年 | 5615篇 |
2015年 | 6454篇 |
2014年 | 8789篇 |
2013年 | 8442篇 |
2012年 | 10061篇 |
2011年 | 10356篇 |
2010年 | 7789篇 |
2009年 | 8096篇 |
2008年 | 7920篇 |
2007年 | 8680篇 |
2006年 | 6985篇 |
2005年 | 5706篇 |
2004年 | 4605篇 |
2003年 | 3687篇 |
2002年 | 2847篇 |
2001年 | 2263篇 |
2000年 | 1930篇 |
1999年 | 1421篇 |
1998年 | 1215篇 |
1997年 | 1000篇 |
1996年 | 789篇 |
1995年 | 613篇 |
1994年 | 515篇 |
1993年 | 378篇 |
1992年 | 348篇 |
1991年 | 238篇 |
1990年 | 238篇 |
1989年 | 177篇 |
1988年 | 118篇 |
1987年 | 44篇 |
1986年 | 54篇 |
1985年 | 45篇 |
1984年 | 42篇 |
1983年 | 42篇 |
1982年 | 44篇 |
1981年 | 22篇 |
1980年 | 34篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1975年 | 16篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
变结构变参数设计方法及其在机械CAD中的应用 总被引:4,自引:0,他引:4
提出了一种新颖的机械结构设计思想-变结构变参数设计方法,并结合实例,阐述了变结构变参数设计的概念、原则、实施措施和意义。由此对I-deas软件包进行了二次开发,编制了发动机曲轴专用CAD软件程序,并用某型号发动机曲轴进行了验证。 相似文献
82.
We study the application of the geographic nearest neighbor approach to two problems. The first problem is the construction of an approximately minimum length rectilinear Steiner tree for a set ofn points in the plane. For this problem, we introduce a variation of a subgraph of sizeO(n) used by YaO [31] for constructing minimum spanning trees. Using this subgraph, we improve the running times of the heuristics discussed by Bern [6] fromO(n
2
log
n) toO(n log2
n). The second problem is the construction of a rectilinear minimum spanning tree for a set ofn noncrossing line segments in the plane. We present an optimalO(n logn) algorithm for this problem. The rectilinear minimum spanning tree for a set of points can thus be computed optimally without using the Voronoi diagram. This algorithm can also be extended to obtain a rectilinear minimum spanning tree for a set of nonintersecting simple polygons.The results in this paper are a part of Y. C. Yee's Ph.D. thesis done at SUNY at Albany. He was supported in part by NSF Grants IRI-8703430 and CCR-8805782. S. S. Ravi was supported in part by NSF Grants DCI-86-03318 and CCR-89-05296. 相似文献
83.
Thomas L. Landers Melinda K. Beavers Malik Sadiq Don E. Stuart 《Computers & Industrial Engineering》1994,27(1-4):245-248
This paper describes an approach, conceptual framework, and software architecture for dynamic reconfiguration of the order picking system. The research and development project was sponsored by the Material Handling Research Center (MHRC), a National Science Foundation sponsored Cooperative Industry/University Research Center. The storage configuration is assumed to be an in-the-aisle order picking system in which stockkeeping units (SKUs) can occupy variable capacity storage locations and stock-splitting is allowed among zones (clusters). The product mix may include multiple product families with different life cycles, correlated demand within families and commonality of demand across families. 相似文献
84.
85.
86.
This paper attempts to shed light on the determinants of energy demand in Turkey. Energy demand model is first proposed using the ant colony optimization (ACO) approach. It is multi-agent systems in which the behavior of each ant is inspired by the foraging behavior of real ants to solve optimization problem. ACO energy demand estimation (ACOEDE) model is developed using population, gross domestic product (GDP), import and export. All equations proposed here are linear and quadratic. Quadratic_ACOEDE provided better-fit solution due to fluctuations of the economic indicators. The ACOEDE model plans the energy demand of Turkey until 2025 according to three scenarios. The relative estimation errors of the ACOEDE model are the lowest when they are compared with the Ministry of Energy and Natural Resources (MENR) projection. 相似文献
87.
郑文新 《水科学与工程技术》2007,(4):25-27
黑河水利枢纽右岸溢洪洞为缩短引渠左导墙的长度,减少施工开挖量,降低施工难度,减少工程投资,进行优化试验.通过对7种不同的方案对比分析,选择了合适的体型,满足了工程要求. 相似文献
88.
模糊规划在炼油厂生产计划优化中的应用 总被引:7,自引:1,他引:6
生产计划的编制是炼油化工企业生产经营管理中的一个关键环节,然而由于市场变化的不确定性,使得企业的长远规划制定受到限制,笔者将模糊数学应用于炼厂生产计划的编制,通过模糊规划对炼油企业生产计划进行优化,使编得的生产计划在一定程度上反映市场的变化并使企业的生产效益最优,为企业管理决策者进行长期规划给予指导,给出了实例来说明该方法的可行性。 相似文献
89.
90.
Many real-world problems are multi-objective optimization problems and evolutionary algorithms are quite successful on such problems. Since the task is to compute or approximate the Pareto front, multi-objective optimization problems are considered as more difficult than single-objective problems. One should not forget that the fitness vector with respect to more than one objective contains more information that in principle can direct the search of evolutionary algorithms. Therefore, it is possible that a single-objective problem can be solved more efficiently via a generalized multi-objective model of the problem. That this is indeed the case is proved by investigating the computation of minimum spanning trees.This work was supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the Collaborative Research Center Computational Intelligence (SFB 531) and by the German-Israeli Foundation (GIF) in the project Robustness Aspects of Algorithms. 相似文献