全文获取类型
收费全文 | 1520028篇 |
免费 | 29460篇 |
国内免费 | 9083篇 |
专业分类
电工技术 | 36827篇 |
技术理论 | 5篇 |
综合类 | 9976篇 |
化学工业 | 276332篇 |
金属工艺 | 65882篇 |
机械仪表 | 44451篇 |
建筑科学 | 48974篇 |
矿业工程 | 12445篇 |
能源动力 | 51235篇 |
轻工业 | 114560篇 |
水利工程 | 15698篇 |
石油天然气 | 39415篇 |
武器工业 | 586篇 |
无线电 | 200071篇 |
一般工业技术 | 284229篇 |
冶金工业 | 149580篇 |
原子能技术 | 34420篇 |
自动化技术 | 173885篇 |
出版年
2021年 | 17164篇 |
2020年 | 13055篇 |
2019年 | 15543篇 |
2018年 | 16498篇 |
2017年 | 15976篇 |
2016年 | 22201篇 |
2015年 | 18939篇 |
2014年 | 30706篇 |
2013年 | 90105篇 |
2012年 | 37668篇 |
2011年 | 49972篇 |
2010年 | 44748篇 |
2009年 | 53123篇 |
2008年 | 46612篇 |
2007年 | 43340篇 |
2006年 | 46593篇 |
2005年 | 40778篇 |
2004年 | 42353篇 |
2003年 | 42031篇 |
2002年 | 41086篇 |
2001年 | 37686篇 |
2000年 | 36148篇 |
1999年 | 34925篇 |
1998年 | 40675篇 |
1997年 | 36780篇 |
1996年 | 33899篇 |
1995年 | 30089篇 |
1994年 | 28264篇 |
1993年 | 28035篇 |
1992年 | 26252篇 |
1991年 | 23237篇 |
1990年 | 23499篇 |
1989年 | 22508篇 |
1988年 | 21034篇 |
1987年 | 19341篇 |
1986年 | 18734篇 |
1985年 | 22010篇 |
1984年 | 22300篇 |
1983年 | 20252篇 |
1982年 | 19208篇 |
1981年 | 19281篇 |
1980年 | 17865篇 |
1979年 | 18483篇 |
1978年 | 17698篇 |
1977年 | 17188篇 |
1976年 | 17739篇 |
1975年 | 15965篇 |
1974年 | 15538篇 |
1973年 | 15590篇 |
1972年 | 13039篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
Xiaopo Wu Yangming Shi Weibo Meng Xiaofei Ma Nian Fang 《International Journal of Satellite Communications and Networking》2019,37(3):283-291
Electromagnetic signal emitted by satellite communication (satcom) transmitters are used to identify specific individual uplink satcom terminals sharing the common transponder in real environment, which is known as specific emitter identification (SEI) that allows for early indications and warning (I&W) of the targets carrying satcom furnishment and furthermore the real time electromagnetic situation awareness in military operations. In this paper, the authors are the first to propose the identification of specific transmitters of satcom by using probabilistic neural networks (PNN) to reach the goal of target recognition. We have been devoted to the examination by exploring the feasibility of utilizing the Hilbert transform to signal preprocessing, applying the discrete wavelet transform to feature extraction, and employing the PNN to perform the classification of stationary signals. There are a total of 1000 sampling time series with binary phase shift keying (BPSK) modulation originated by five types of satcom transmitters in the test. The established PNNs classifier implements the data testing and finally yields satisfactory accuracy at 8 dB(±1 dB) carrier to noise ratio, which indicates the feasibility of our method, and even the keen insight of its application in military. 相似文献
172.
Mobile Networks and Applications - Public cloud system offers Infrastructure-as-a-Service (IaaS) to deliver the computational resources on demand. Resource requirements of a cloud environment are... 相似文献
173.
Kozhitov L. V. Kiselev B. G. Raykova T. B. Popkova A. V. Kostishin V. G. Muratov D. G. Yakushko E. V. Kosushkin V. G. Bebenin V. G. 《Russian Microelectronics》2019,48(8):599-612
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical... 相似文献
174.
Breslavs’kyi D. V. Metel’yov V. O. Morachkovs’kyi O. K. Tatarinova O. A. 《Strength of Materials》2019,51(5):753-760
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A... 相似文献
175.
176.
Kazantsev Yu. N. Kraftmakher G. A. Mal’tsev V. P. 《Journal of Communications Technology and Electronics》2019,64(6):550-554
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice... 相似文献
177.
Zakharov A. V. Rozenko S. A. 《Journal of Communications Technology and Electronics》2019,64(4):430-438
Journal of Communications Technology and Electronics - Microstrip band-pass filters (BPFs) containing quarter-wavelength resonators and a Π-shaped half-wavelength resonator placed next to each... 相似文献
178.
Geetha R. Madhusudhan V. Padmavathy T. Lallithasree A. 《Wireless Personal Communications》2019,108(3):1957-1976
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the... 相似文献
179.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the... 相似文献
180.
When solving a mathematical problem, students who do not have sufficient conceptual understanding may perform poorly and exhibit misconceptions. This study was aimed to examine students' conceptual understanding and significant misconceptions when solving number sense‐related problems. An online three‐tier diagnostic test was administered to 125 fifth‐grade students with varied socio‐economic backgrounds in Hong Kong. Only 14.40% of the students exhibited high performance with high confidence, indicating that these students had a profound conceptual understanding of number sense. In addition, the majority of the students (66.40%) did not demonstrate number sense; these students exhibited several significant misconceptions and could solve the questions only by using a rule‐based method or guessing. Accordingly, most students performed unsatisfactorily on number sense‐related problems. This study is imperative in identifying early predictors and provides information for further compatible interventions in the teaching and learning of number sense in Hong Kong in particular and worldwide in general. 相似文献