全文获取类型
收费全文 | 400871篇 |
免费 | 33487篇 |
国内免费 | 18602篇 |
专业分类
电工技术 | 23742篇 |
技术理论 | 46篇 |
综合类 | 29064篇 |
化学工业 | 66395篇 |
金属工艺 | 23309篇 |
机械仪表 | 25359篇 |
建筑科学 | 30777篇 |
矿业工程 | 12894篇 |
能源动力 | 10716篇 |
轻工业 | 28991篇 |
水利工程 | 7793篇 |
石油天然气 | 25084篇 |
武器工业 | 3228篇 |
无线电 | 43952篇 |
一般工业技术 | 44244篇 |
冶金工业 | 20309篇 |
原子能技术 | 4147篇 |
自动化技术 | 52910篇 |
出版年
2024年 | 1701篇 |
2023年 | 6257篇 |
2022年 | 11264篇 |
2021年 | 15544篇 |
2020年 | 11783篇 |
2019年 | 9704篇 |
2018年 | 11173篇 |
2017年 | 12516篇 |
2016年 | 11508篇 |
2015年 | 15810篇 |
2014年 | 19863篇 |
2013年 | 23888篇 |
2012年 | 26076篇 |
2011年 | 28983篇 |
2010年 | 25741篇 |
2009年 | 24495篇 |
2008年 | 23980篇 |
2007年 | 22799篇 |
2006年 | 22886篇 |
2005年 | 19995篇 |
2004年 | 13633篇 |
2003年 | 11969篇 |
2002年 | 11115篇 |
2001年 | 9816篇 |
2000年 | 9533篇 |
1999年 | 9940篇 |
1998年 | 7512篇 |
1997年 | 6408篇 |
1996年 | 6041篇 |
1995年 | 4969篇 |
1994年 | 4043篇 |
1993年 | 2760篇 |
1992年 | 2171篇 |
1991年 | 1654篇 |
1990年 | 1288篇 |
1989年 | 1045篇 |
1988年 | 864篇 |
1987年 | 559篇 |
1986年 | 433篇 |
1985年 | 270篇 |
1984年 | 217篇 |
1983年 | 174篇 |
1982年 | 144篇 |
1981年 | 78篇 |
1980年 | 103篇 |
1979年 | 54篇 |
1978年 | 26篇 |
1977年 | 33篇 |
1976年 | 41篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
机电排灌工程是丘陵、滨湖地区的主要灌溉设施,必须建立适应市场经济的管理新机制,确保工程良性运行和巩固发展,满足不断发展的工农业生产需要。 相似文献
992.
Synchronization attacks like random cropping and time-scale modification are very challenging problems to audio watermarking techniques. To combat these attacks, a novel content-dependent localized robust audio watermarking scheme is proposed. The basic idea is to first select steady high-energy local regions that represent music edges like note attacks, transitions or drum sounds by using different methods, then embed the watermark in these regions. Such regions are of great importance to the understanding of music and will not be changed much for maintaining high auditory quality. In this way, the embedded watermark has the potential to escape all kinds of distortions. Experimental results show strong robustness against common audio signal processing, time-domain synchronization attacks, and most distortions introduced in Stirmark for Audio. 相似文献
993.
994.
本文引入L-,l-连通度的概念,把Rosenfeld等人建立的三维数字拓扑模糊化;并在三维地震处理中找到了它的应用模型. 相似文献
995.
Computers for symbolic processing 总被引:1,自引:0,他引:1
Wah B.W. Lowrie M.B. Li G.-J. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(4):509-540
A detailed survey on the motivations, design, applications, current status, and limitations of computers designed for symbolic processing is provided. Symbolic processing computations are performed at the word, relation, or meaning levels, and the knowledge used in symbolic applications may be fuzzy, uncertain, indeterminate, and ill represented. Various techniques for knowledge representation and processing are discussed from both the designers' and users' points of view. The design and choice of a suitable language for symbolic processing and the mapping of applications into a software architecture are then considered. The process of refining the application requirements into hardware and software architectures is treated, and state-of-art sequential and parallel computers designed for symbolic processing are discussed 相似文献
996.
Stephen Shaoyi Liao Huai Qing Wang Qiu Dan Li Wei Yi Liu 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(3):660-671
This paper presents a new method for learning Bayesian networks from functional dependencies (FD) and third normal form (3NF) tables in relational databases. The method sets up a linkage between the theory of relational databases and probabilistic reasoning models, which is interesting and useful especially when data are incomplete and inaccurate. The effectiveness and practicability of the proposed method is demonstrated by its implementation in a mobile commerce system. 相似文献
997.
想象热刺激和实际热刺激脑功能成像研究 总被引:2,自引:0,他引:2
本实验用功能性核磁共振成像技术(fMRI)对人想象热刺激和实际接受热刺激进行了研究。这是继想象冷刺激和实际接受冷刺激实验之后的另一个关于想象刺激与实际接受刺激的实验、实验结果发现想象热刺激与实际热刺激激活脑区既有相同之处也有不同之处。想象热刺激激活了初级体感区(SI)、左侧额上回、左侧额中回、运动区和扣带回。实际热刺激激活了初级体感区(SI)区、右侧额上回、右侧额中回、运动区。区别在于额叶和扣带回,这个结论与想象冷刺激和实际冷刺激实验的结论几乎相同,只是两种情况下在额叶的具体差别不同。 相似文献
998.
999.
1000.
A silicide coating was prepared on Ti3SiC2-based ceramic by pack cementation to improve the oxidation resistance of Ti3SiC2, which is a technologically important material for high temperature applications. The microstructure, phase composition and
oxidation resistance of the coated sample were investigated. The results demonstrated that the silicide coating was mainly
composed of TiSi2 and SiC. A single layer of a mixture of SiO2 and TiO2 was formed on the surface of the coated sample during isothermal oxidation at 1100 °C and 1200 °C for 20h. Compared to Ti3SiC2, the parabolic rate constant of silicide coated Ti3SiC2 decreased by 2~3 orders of magnitude. Furthermore, the coated sample showed much better cyclic oxidation resistance than
Ti3SiC2 during the cyclic oxidation at 1100 °C for 400 times. However, during the preparation of the coating, a number of fine cracks
formed in the outer layer of the coating. When these cracks penetrated the whole coating during the cyclic oxidation, the
oxidation rate was accelerated, which degraded the oxidation resistance.
Electronic Publication 相似文献