全文获取类型
收费全文 | 29076篇 |
免费 | 2392篇 |
国内免费 | 954篇 |
专业分类
电工技术 | 1246篇 |
综合类 | 1610篇 |
化学工业 | 6080篇 |
金属工艺 | 1085篇 |
机械仪表 | 1154篇 |
建筑科学 | 1556篇 |
矿业工程 | 435篇 |
能源动力 | 790篇 |
轻工业 | 4460篇 |
水利工程 | 539篇 |
石油天然气 | 754篇 |
武器工业 | 136篇 |
无线电 | 2537篇 |
一般工业技术 | 3365篇 |
冶金工业 | 1552篇 |
原子能技术 | 245篇 |
自动化技术 | 4878篇 |
出版年
2024年 | 111篇 |
2023年 | 397篇 |
2022年 | 1023篇 |
2021年 | 1245篇 |
2020年 | 951篇 |
2019年 | 830篇 |
2018年 | 913篇 |
2017年 | 976篇 |
2016年 | 952篇 |
2015年 | 1268篇 |
2014年 | 1734篇 |
2013年 | 2183篇 |
2012年 | 2357篇 |
2011年 | 2564篇 |
2010年 | 2124篇 |
2009年 | 2052篇 |
2008年 | 1883篇 |
2007年 | 1764篇 |
2006年 | 1393篇 |
2005年 | 1035篇 |
2004年 | 737篇 |
2003年 | 553篇 |
2002年 | 484篇 |
2001年 | 340篇 |
2000年 | 271篇 |
1999年 | 250篇 |
1998年 | 406篇 |
1997年 | 269篇 |
1996年 | 196篇 |
1995年 | 130篇 |
1994年 | 119篇 |
1993年 | 121篇 |
1992年 | 74篇 |
1991年 | 78篇 |
1990年 | 57篇 |
1989年 | 71篇 |
1988年 | 51篇 |
1987年 | 66篇 |
1986年 | 48篇 |
1985年 | 40篇 |
1984年 | 36篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 24篇 |
1976年 | 40篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Wen Juan Zeng Hao Wang Yuzhu Liu Shurong Xue Yiming 《Multimedia Tools and Applications》2021,80(2):2517-2536
Multimedia Tools and Applications - Speech is one of the essential ways of communication. The study of speech steganography provides great value in information security. To improve imperceptibility... 相似文献
23.
设计了基于MSP430单片机的灾害性天气预警管理系统,针对常见的雨量、风速及温度自然因素实现实时的监测,并对数据进行分析和处理,设置出相应的警报等级,并能根据警报的等级控制相应的三路设备。 相似文献
24.
Juan Pedro Muñoz-Gea Josemaria Malgosa-Sanahuja Pilar Manzanares-Lopez 《Peer-to-Peer Networking and Applications》2013,6(3):340-360
Recently, a new peer-assisted architecture to build content delivery systems has been presented. This architecture is based on the use of the storage capacity of end-users’ set-top boxes (STBs), connected in a peer-to-peer (P2P) manner in order to help the content servers in the delivery process. In these systems, the contents are usually split into a set of smaller pieces, called sub-streams, which are randomly injected at the STBs. The present paper is focused on Video on Demand (VoD) streaming and it is assumed that the STB-based content delivery system is deployed over the global Internet, where the clients are distributed over different ISP networks. In this scenario, three different strategies are studied for increasing the percentage of data uploaded by peers, in order to offload the content servers as much as possible. First of all, a new mechanism is presented which determines which sub-stream has to be placed at which STB by a Non-Linear Programming (NLP) formulation. A different strategy for reducing the content server load is to take advantage of the available bandwidth in the different ISP networks. In this sense, two new mechanisms for forwarding the VoD requests to different ISP networks are presented. Finally, the present paper also shows that in some situations the available uplink bandwidth is associated with STBs that do not have the required sub-streams. Regarding this concern, a new mechanism has been designed that dynamically re-allocates some streams, which are being transmitted from specific STBs, to different STBs, in order to find the necessary resources to start new streaming sessions. 相似文献
25.
Jorge E. Camargo Juan C. Caicedo Fabio A. Gonzalez 《Journal of Visual Languages and Computing》2013,24(1):53-67
While search engines have been a successful tool to search text information, image search systems still face challenges. The keyword-based query paradigm used to search in image collection systems, which has been successful in text retrieval, may not be useful in scenarios where the user does not have the precise way to express a visual query. Image collection exploration is a new paradigm where users interact with the image collection to discover useful and relevant pictures. This paper proposes a framework for the construction of an image collection exploration system based on kernel methods, which offers a mathematically strong basis to address each stage of an image collection exploration system: image representation, summarization, visualization and interaction. In particular, our approach emphasizes a semantic representation of images using kernel functions, which can be seamlessly harnessed across all system components. Experiments were conducted with real users to verify the effectiveness and efficiency of the proposed strategy. 相似文献
26.
随着现今社会互联网、个人终端技术的飞越发展,电子商务越来越多的出现在人们的生活与工作中,这种全新的商务模式具有便捷、高效率、低成本的特点.同时,这种全新的商务模式对管理水平、信息传递技术都提出了更高的要求,其中安全的重要性尤为突出. 相似文献
27.
李娟 《数码设计:surface》2009,(12):289-291
卷草纹是中国传统装饰纹样之一,它的形成和发展记载了中国装饰艺术旺盛的生命力。本文分析了卷草纹的发展过程、形象构成以及艺术特征,并通过具体案例诠释了它在现代设计各个领域的延展和应用。旨在探索传统装饰纹样在现代设计中的传承与发展的方向。 相似文献
28.
文章阐述了地税网上申报系统开发的背景和意义;介绍了基于J2EE的网上报税系统的结构、软件的主要功能及具体的实现方法和所用的关键技术;总结了所用技术的优势以及系统中难点的处理。 相似文献
29.
Rafael Diaz 《国际生产研究杂志》2016,54(8):2487-2498
The warehouse order-picking operation is one of the most labour-intense activities that has an important impact on responsiveness and efficiency of the supply chain. An understanding of the impact of the simultaneous effects of customer demand patterns and order clustering, considering physical restrictions in product storage, is critical for improving operational performance. Storage restrictions may include storing non-uniform density stock keeping units (SKUs) whose dimensions and weight constrain the order-picking operation given that a priority must be followed. In this paper, a heuristic optimisation based on a quadratic integer programming is employed to generate a layout solution that considers customer demand patterns and order clustering. A simulation model is used to investigate the effects of creating and implementing these layout solutions in conjunction with density zones to account for restrictions in non-uniform density SKUs. Results from combining layout optimisation heuristics and density zoning indicate statistical significant differences between assignments that ignore the aforementioned factors and those that recognise it. 相似文献
30.