全文获取类型
收费全文 | 38728篇 |
免费 | 4179篇 |
国内免费 | 2144篇 |
专业分类
电工技术 | 3083篇 |
技术理论 | 3篇 |
综合类 | 4844篇 |
化学工业 | 2080篇 |
金属工艺 | 739篇 |
机械仪表 | 1808篇 |
建筑科学 | 4842篇 |
矿业工程 | 2037篇 |
能源动力 | 1141篇 |
轻工业 | 4240篇 |
水利工程 | 2210篇 |
石油天然气 | 4305篇 |
武器工业 | 851篇 |
无线电 | 2416篇 |
一般工业技术 | 2455篇 |
冶金工业 | 1344篇 |
原子能技术 | 273篇 |
自动化技术 | 6380篇 |
出版年
2024年 | 237篇 |
2023年 | 605篇 |
2022年 | 1133篇 |
2021年 | 1358篇 |
2020年 | 1471篇 |
2019年 | 1179篇 |
2018年 | 1163篇 |
2017年 | 1250篇 |
2016年 | 1562篇 |
2015年 | 1610篇 |
2014年 | 2733篇 |
2013年 | 2397篇 |
2012年 | 3093篇 |
2011年 | 3187篇 |
2010年 | 2314篇 |
2009年 | 2374篇 |
2008年 | 2138篇 |
2007年 | 2583篇 |
2006年 | 2226篇 |
2005年 | 1966篇 |
2004年 | 1599篇 |
2003年 | 1348篇 |
2002年 | 967篇 |
2001年 | 868篇 |
2000年 | 677篇 |
1999年 | 595篇 |
1998年 | 436篇 |
1997年 | 393篇 |
1996年 | 321篇 |
1995年 | 260篇 |
1994年 | 201篇 |
1993年 | 160篇 |
1992年 | 98篇 |
1991年 | 98篇 |
1990年 | 60篇 |
1989年 | 79篇 |
1988年 | 32篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 21篇 |
1984年 | 26篇 |
1983年 | 29篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 7篇 |
1963年 | 7篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
针对太原可口可乐综合厂房主筋采用φ28、φ32三级钢存在的可焊性差的问题,提出了在施工中采用套筒挤压连接的方式,并对该方法的操作要点及质量控制措施进行了总结。 相似文献
32.
本文着重介绍了构成《现代勘探决策理论系统》的5个主要计算机模块,即:生油岩热演化处理、求任意曲边形面积、数学模拟预测资源量、勘探经济评价分析及决策、辅助处理等模块。该系统曾在塔里木盆地和准噶尔盆地的油气资源评价和勘探决策中发挥了作用,受到了专家和用户的好评。 相似文献
33.
手写体汉字识别问题综论 总被引:6,自引:0,他引:6
本文在讨论了人对汉字的认知心理试验研究结果之后,认为人类的汉字识别是经由整字属性及分层结构的多种途径复合而成的。这些途径中的大多数都可以在手写体汉字的机器识别中模仿运用。由此可把汉字的机器识别方法归纳为整模式法和子模式法两个大类,对它们的有利方面和困难方面进行了讨论;对影响其性能的因素进行了分析;对识别率以及它与识别字集大小和后处理等的关系提出了评估的问题。 相似文献
34.
James Rodgers Kaye Wolf Norm Willis Don Hamilton Ralph Ledbetter Curtis Stewart 《Color research and application》1994,19(5):322-331
A multiplant Quality Improvement Team [QIT] was firmed to develop and implement an evaluation program for various color measurement .systems as potential replacements for the then-current aging systems. The emphasis qf this article is the analytical methodology utilized to evaluate the various color systems. The evaluation program consisted cf two phases. Phase I was a general overview/review of several systems, while Phase II was an extensive internal comparative evaluation measurement systems. These were Milton-Roy's ColorMate HDS, HunterLab's Ultrascan, Datacolor's CS-5, and BYK-Gardner's The Color Sphere [TCS]. The main comparison criteria were interinstrument agreement [agreement between two instruments ofthe same system], user-friendly software and computer interface capability, vendor amenability to a long-term logistical and maintenance relationship, and price. All systems were evaluated by duplicate measurements on various color tiles, yarns, and polymer flakes-over 1600 measurements on each system. The systems were compared with an instrument matrix, a decision matrix, and a product matrix. The instrument matrix was a comparison qfinstrument parameters, software/math treatments, and economics. The decision matrix was a forced ranking of each system by each criteria category [1–4 scale, with 1 representing the best and 4 representing the worst]. The product matrix accentuated the relative importance ofone criterion category over another by multiplying the forced ranking by the criticality of the category. The criticality of a given category wus determined by consensus within the QIT. Thr combination qf the three matrices allowed the evaluator[.s] t o select the color rneasuremmt system that best satixfied the color measurement needs and requirements of their facility and their products. For this evaluation, all ofthe evaluated systems were superior to the then-current agingsystems. As a result of this methodology, one instrument emerged as clearly superior. © 1994 John Wrley & Sons, Inc. 相似文献
35.
一种基于时间分层决策矩阵的综合评价算法 总被引:1,自引:0,他引:1
综合评价系统用四元总体(A,Z,X^(k),D)表示,其中决策矩阵X^(k)是具有对象维i,指标维j,时间维k的三维矩阵,将三维矩阵X(k)按时间划分形成m个二维矩阵,每个二维矩阵分别代表每个年度n个评价对象对应于p个指标的属性集,讨论了按时间分层决策矩阵的多指标综合评价问题,描述了按时间分层的决策矩阵的求解算法,并采用Visual Foxpro数据库语言编程实现。 相似文献
36.
G. Colombo G. Pennoni 《International Journal of Satellite Communications and Networking》1987,5(2):77-84
The continuing improvement of RF components, particularly in the field of spot-beam antennas, combined with the steady progress in digital technology, leads us to consider the advantages of a satellite system able to provide full connectivity to ground stations operating at different data rates. For low data rates, two different access methods: continuous TDM and Multi-carrier TDMA, are compared for earth-stations operating at 2Mb/s. The two methods are compared from the point of view of efficiency and adaptability in a non-uniform load environment. Some control criteria are proposed for the Multi-carrier system. Both methods are particularly suited for small users. 相似文献
37.
38.
Since Samuel's work on checkers over thirty years ago, much effort has been devoted to learning evaluation functions. However, all such methods are sensitive to the feature set chosen to represent the examples. If the features do not capture aspects of the examples significant for problem solving, the learned evaluation function may be inaccurate or inconsistent. Typically, good feature sets are carefully handcrafted and a great deal of time and effort goes into refining and tuning them. This paper presents an automatic knowledge-based method for generating features for evaluation functions. The feature set is developed iteratively: features are generated, then evaluated, and this information is used to develop new features in turn. Both the contribution of a feature and its computational expense are considered in determining whether and how to develop it further.
This method has been applied to two problem-solving domains: the Othello board game and the domain of telecommunications network management. Empirical results show that the method is able to generate many known features and several novel features and to improve concept accuracy in both domains. 相似文献
This method has been applied to two problem-solving domains: the Othello board game and the domain of telecommunications network management. Empirical results show that the method is able to generate many known features and several novel features and to improve concept accuracy in both domains. 相似文献
39.
针对战时装备供应链的特点,以远程精确打击、敌特后方袭扰和恶劣天气等三个因素为主要风险指标,运用修正的模糊信息熵权对TOPSIS法进行改进,提出了一种新的战时装备供应链风险评估方法。首先利用原始数据产生的模糊信息熵权进行客观赋权,并引入专家因素对权重进行主观修正,利用逼近理想解排序方法进行运算,最后通过实例计算与分析,验证该评估方法简便易行,结论合理,有效降低了指挥员决策的主观随意性。 相似文献
40.
如何提升系统的互操作性是当前仿真领域需要着力解决的问题,而理解互操作问题产生的根源则是提升互操作性的前提。从互操作性的概念分析人手,剖析了仿真系统互操作问题产生的原因,将之概括为组织、抽象和实现三个层面,并提出了相应的解决框架。框架通过建立概念模型库和平台无关模型库解决抽象层面的问题,利用模型实现的自动化和服务化解决实现层面的问题,可以作为领域内解决互操作问题的借鉴。最后提出了使用对比法和测试法评估系统互操作性的思路。 相似文献