全文获取类型
收费全文 | 68031篇 |
免费 | 7146篇 |
国内免费 | 4439篇 |
专业分类
电工技术 | 7444篇 |
技术理论 | 1篇 |
综合类 | 6671篇 |
化学工业 | 3702篇 |
金属工艺 | 3857篇 |
机械仪表 | 8511篇 |
建筑科学 | 4658篇 |
矿业工程 | 6185篇 |
能源动力 | 1357篇 |
轻工业 | 3687篇 |
水利工程 | 1100篇 |
石油天然气 | 1145篇 |
武器工业 | 883篇 |
无线电 | 5273篇 |
一般工业技术 | 4215篇 |
冶金工业 | 2546篇 |
原子能技术 | 231篇 |
自动化技术 | 18150篇 |
出版年
2024年 | 340篇 |
2023年 | 1030篇 |
2022年 | 1968篇 |
2021年 | 2328篇 |
2020年 | 2388篇 |
2019年 | 1782篇 |
2018年 | 1632篇 |
2017年 | 2033篇 |
2016年 | 2408篇 |
2015年 | 2709篇 |
2014年 | 4581篇 |
2013年 | 3811篇 |
2012年 | 5442篇 |
2011年 | 5636篇 |
2010年 | 4308篇 |
2009年 | 4233篇 |
2008年 | 4069篇 |
2007年 | 4946篇 |
2006年 | 4369篇 |
2005年 | 3636篇 |
2004年 | 2865篇 |
2003年 | 2514篇 |
2002年 | 2017篇 |
2001年 | 1687篇 |
2000年 | 1373篇 |
1999年 | 1042篇 |
1998年 | 791篇 |
1997年 | 682篇 |
1996年 | 556篇 |
1995年 | 497篇 |
1994年 | 449篇 |
1993年 | 299篇 |
1992年 | 220篇 |
1991年 | 170篇 |
1990年 | 172篇 |
1989年 | 162篇 |
1988年 | 113篇 |
1987年 | 53篇 |
1986年 | 62篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1959年 | 6篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
介绍PAL制彩色全电视信号中色同步信号编码原理及恢复逐行倒相副载波的过程中,两种计算色同步信号相位角的方法。并且在实验的基础上得出:最小二乘法在PAL制电视信号的副载波相位角计算中不仅可以满足精度要求,而且简便灵活。 相似文献
92.
阮芙英 《纺织高校基础科学学报》1995,8(1):91-95
现代光学和通讯理论由于引入了傅里叶变换的方法,使计算光学系统和通讯系统的物像的对应关系简洁、清晰。该文用傅氏变换计算长为2a、照度为A的均匀缝光源在观察面上的光强分布为I(x)=│E(x)│^2=AA^2a^2(sin2πfa/2πfa)此方法也可运用于矩形孔、圆孔等。 相似文献
93.
94.
军事地理信息系统的现状与发展 总被引:5,自引:0,他引:5
在信息作战条件下,军事地理信息系统(MGIS)作为作战指挥自动化、数字化战场和现代武器系统的战场地理环境平台备受世界各国的重视。美国投入了大量人力、物力和财力先后研制并使用了地形分析系统等一系列应用系统,目前正着手研制地理影像情报综合管理系统(TPED)和地理影像与地理空间信息系统。我国的MGIS起步较晚,但发展很快,已成功地研制出了第一个具有自主版权的MGIS工具软件。该软件采用层次化体系结构和面向对象的设计方法,具有功能齐全、结构紧密、安全性好等特点。文章在分析国内外MGIS的基础上,着重介绍了军事地理信息系统软件的研制特点,并对军事地理信息系统进一步发展要解决的若干问题进行了探讨。 相似文献
95.
首先在结构上创造了新型螺栓、螺母和一套崭新的安装机。在主机上去掉了精密、复杂、昂贵的机器人或机械手,改用结构简单的集成齿轮机构,以实现同步旋拧功能;运用现代流体传动与控制的理论,建立流本控制的数学模型和传递函数,从而实现了4个同步安装的效果。 相似文献
96.
Negotiation support systems: roots, progress and needs 总被引:2,自引:0,他引:2
Abstract. This paper identifies game theories and social behavior science as important roots for negotiation support systems (NSS) research. As these are not typically cited in the NSS literature, summary reviews of them are provided with indications of their relevance to NSS study. On the other hand, neither offers a sufficiently general-purpose formal model of negotiation that could serve as a backbone for NSS research. A survey of that research is provided, indicating that prugress to date has been somewhat eclectic and devoid of such a model. Our central contention is that a theoretical foundation for NSS study is much needed. Desirable characteristics of a suitable negotiation model are identified as guidance for future research that will aim to devise (and subsequently apply and test) such a model. 相似文献
97.
在我国经济快速发展的大背景下,能源(水、电、油)的消耗在企业中所占的比重越来越高,也受到愈来愈大的重视。同时也由于房地产的快速发展需求,中央空调的市场需求呈现强劲的增长。在市场容量不断增大的吸引下,越来越多的厂家加入到商用中央空调的领域。变频技术应用于中央空调系统,对提升中央空调自动化水平、降低能耗.减少对电网的冲击,延长机械及管网的使用寿命,都具有重要的意义。 相似文献
98.
Tree-based partitioning of date for association rule mining 总被引:1,自引:1,他引:0
The most computationally demanding aspect of Association Rule Mining is the identification and counting of support of the frequent sets of items that occur together sufficiently often to be the basis of potentially interesting rules. The task increases in difficulty with the scale of the data and also with its density. The greatest challenge is posed by data that is too large to be contained in primary memory, especially when high data density and/or low support thresholds give rise to very large numbers of candidates that must be counted. In this paper, we consider strategies for partitioning the data to deal effectively with such cases. We describe a partitioning approach which organises the data into tree structures that can be processed independently. We present experimental results that show the method scales well for increasing dimensions of data and performs significantly better than alternatives, especially when dealing with dense data and low support thresholds.
Shakil Ahmed received a first class BSc (Hons) degree from Dhaka University, Bangladesh, in 1990; and an MSc (first class), also Dhaka University, in 1992. He received his PhD from The University of Liverpool, UK, in 2005. From 2000 onwards he is a member of the Data Mining Group at the Department of Computer Science of the University of Liverpool, UK. His research interests include data mining, Association Rule Mining and pattern recognition.
Frans Coenen has been working in the field of Data Mining for many years and has written widely on the subject. He received his PhD from Liverpool Polytechnic in 1989, after which he took up a post as a RA within the Department of Computer Science at the University of Liverpool. In 1997, he took up a lecturing post within the same department. His current Data Mining research interests include Association rule Mining, Classification algorithms and text mining. He is on the programme committee for ICDM'05 and was the chair for the UK KDD symposium (UKKDD'05).
Paul Leng is professor of e-Learning at the University of Liverpool and director of the e-Learning Unit, which is responsible for overseeing the University's online degree programmes, leading to degrees of MSc in IT and MBA. Along with e-Learning, his main research interests are in Data Mining, especially in methods of discovering Association Rules. In collaboration with Frans Coenen, he has developed efficient new algorithms for finding frequent sets and is exploring applications in text mining and classification. 相似文献
99.
100.
本文介绍了底板翻面机及其液压系统的工作原理和设计特点。该机结构紧凑、运行平稳、工作可靠、能耗低,其成功的设计经验对同类设备的设计改造具有一定的参考价值 相似文献