全文获取类型
收费全文 | 5402篇 |
免费 | 422篇 |
国内免费 | 227篇 |
专业分类
电工技术 | 213篇 |
综合类 | 335篇 |
化学工业 | 935篇 |
金属工艺 | 211篇 |
机械仪表 | 397篇 |
建筑科学 | 532篇 |
矿业工程 | 154篇 |
能源动力 | 162篇 |
轻工业 | 384篇 |
水利工程 | 119篇 |
石油天然气 | 243篇 |
武器工业 | 31篇 |
无线电 | 652篇 |
一般工业技术 | 633篇 |
冶金工业 | 261篇 |
原子能技术 | 98篇 |
自动化技术 | 691篇 |
出版年
2024年 | 18篇 |
2023年 | 83篇 |
2022年 | 167篇 |
2021年 | 185篇 |
2020年 | 166篇 |
2019年 | 133篇 |
2018年 | 155篇 |
2017年 | 187篇 |
2016年 | 163篇 |
2015年 | 226篇 |
2014年 | 295篇 |
2013年 | 325篇 |
2012年 | 337篇 |
2011年 | 365篇 |
2010年 | 321篇 |
2009年 | 347篇 |
2008年 | 299篇 |
2007年 | 279篇 |
2006年 | 297篇 |
2005年 | 245篇 |
2004年 | 168篇 |
2003年 | 142篇 |
2002年 | 164篇 |
2001年 | 119篇 |
2000年 | 132篇 |
1999年 | 145篇 |
1998年 | 110篇 |
1997年 | 73篇 |
1996年 | 91篇 |
1995年 | 45篇 |
1994年 | 52篇 |
1993年 | 31篇 |
1992年 | 29篇 |
1991年 | 29篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 2篇 |
排序方式: 共有6051条查询结果,搜索用时 0 毫秒
51.
Jae‐hyoun Yoo Jeongil Seo Hwan Shim Hyunjoo Chung Koeng‐Mo Sung Kyeongok Kang 《ETRI Journal》2011,33(6):977-980
Wave field synthesis (WFS) has been gathering more and more attention recently due to its ability to perfectly reproduce an original sound field. However, to realize theoretically perfect WFS, a four‐sided loudspeaker array that encloses the listener is required. However, it is difficult to build such a system except in large listening spaces, such as a theater or concert hall. In other words, if the listening space is a home, installing a side loudspeaker array is impractical. If the two side walls located to the left and right of the listener can be omitted, a setup using only front and rear loudspeaker arrays may be a solution. In this letter, we present a subjective listening experiment of sound localization/distance based on a WFS using a front and rear loudspeaker array system which is conducted on two listening points and shows average localization errors of 6.1° and 9.18°, while the average distance errors are –27% (0.5 m) and –29% (0.6 m), respectively. 相似文献
52.
Bocheng Bao Li Xu Zhimin Wu Mo Chen Huagan Wu 《International Journal of Electronics》2018,105(7):1159-1169
Based on a memristive diode bridge cascaded with series resistor and inductor filter, a modified memristive canonical Chua’s circuit is presented in this paper. With the modelling of the memristive circuit, a normalised system model is built. Stability analyses of the equilibrium points are performed and bifurcation behaviours are investigated by numerical simulations and hardware experiments. Most extraordinary in the memristive circuit is that within a parameter region, coexisting phenomenon of multiple bifurcation modes is emerged under six sets of different initial values, resulting in the coexistence of four sets of topologically different and disconnected attractors. These coexisting attractors are easily captured by repeatedly switching on and off the circuit power supplies, which well verify the numerical simulations. 相似文献
53.
科研机构向公众开放是其重要的社会责任和义务,有利于提升我国的科普能力。近年来,中科院利用自身的资源优势开展了“公众科学日”等开放的活动,本文在深入调研的基础上,从政策、组织运行、经费、评价激励等方面入手,对中科院向公众开放过程中存在的问题进行了分析,并尝试提出解决问题的建议。 相似文献
54.
In wireless local area network (WLAN), improving the quality of service (QoS) of users is often at odd with striking fairness among users. In this work, we suggest that in WLAN, multiple types of network resources should be jointly allocated to users to achieve “QoS fairness”, which is a new fairness concept targeting at balancing QoS and fairness in WLAN by allocating multiple types of network resources to users. To this end, we first transform user QoS requirements to multi-resource demands and apply the dominant resource fairness scheme to allocate network resources for each user. We prove several salient QoS-based fairness properties based on a model mapping between QoS and resources. We further discuss about more general conditions for diverse mapping models where QoS fairness properties can be satisfied. We find that the QoS fairness properties can be guaranteed as long as the mapping model meets a few practical requirements, indicating the wide applicability of our scheme. To consolidate our multi-resource allocation scheme, we design a practical protocol for WLAN. The simulation results validate that the QoS fairness can be guaranteed in practical WLAN scenario. 相似文献
55.
56.
Moonsoo Kang Jeonghoon Mo Seong-Lyun Kim 《Communications Letters, IEEE》2005,9(11):1018-1020
The loss recovery architecture of TCP under wireless environment is considered. We propose sent-time ordered two lists architecture as an alternative to sequence number ordered single list architecture. By keeping the sent-time order, the recovery mechanism can be more efficient and-simpler and transmission decision is decoupled from loss recovery using the second list. Simulation results show the superiority of our mechanism. 相似文献
57.
本文介绍了一种基于MPEG视频的实时流媒体数字水印方案设计与实现,为数字水印技术在广播电视领域应用于非法信号插播、错播节目、私插广告等监测提供了思路。 相似文献
58.
In social network services, such as Facebook, Google+, Twitter, and certain postings attract more people than others. In this paper, we propose a novel method for predicting the lifespan and retweet times of tweets, the latter being a proxy for measuring the popularity of a tweet. We extract information from retweet graphs, such as posting times; and social, local, and content features, so as to construct prediction knowledge bases. Tweets with a similar topic, retweet pattern, and properties are sequentially extracted from the knowledge base and then used to make a prediction. To evaluate the performance of our model, we collected tweets on Twitter from June 2012 to October 2012. We compared our model with conventional models according to the prediction goal. For the lifespan prediction of a tweet, our model can reduce the time tolerance of a tweet lifespan by about four hours, compared with conventional models. In terms of prediction of the retweet times, our model achieved a significantly outstanding precision of about 50%, which is much higher than two of the conventional models showing a precision of around 30% and 20%, respectively. 相似文献
59.
K. F. Tsang L. Mo Z. B. Ye 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(6):1005-1022
In this paper, both fast Fourier transformation (FFT) and preconditioned CG technique are introduced into method of lines (MOL) to further enhance the computational efficiency of this semi-analytic method. Electromagnetic wave scattering by an infinite plane metallic grating is used as the examples to describe its implementation. For arbitrary incident wave, Helmholz equation and boundary condition are first transformed into new ones so that the impedance matrix elements are calculated by FFT technique. As a result, this Topelitz impedance matrix only requires O(N) memory storage for the conjugate gradient FFT method to solve the current distribution with the computational complexity O(N log N) . Our numerical results show that circulate matrix preconditioner can speed up CG-FFT method to converge in much smaller CPU time than the banded matrix preconditioner. 相似文献
60.
Zheng Wang Jia-Jia Liu Shao-Yun Yin Meng-Yang Li Ya-Jun Hou Dan Wang Jun-Ting Mo Guang Chen 《Advanced functional materials》2023,33(16):2212985
Materials taking abundant advantage of triplet states luminescence have risen lots of attention in decades. In this work, a Cu(I) metal-organic framework (MOF) with synchronous metal-to-ligand charge transfer (MLCT) state and triplet emission of the ligand is synthesized from a D–π–A–π–D ligand with suitable energy gap. The Cu(I) MOF possessed MLCT emission in the range of 450–505 nm with microsecond lifetimes (1.07 to 5.38 µs) and a triplet state emission in near infrared (NIR) region ≈705 nm with lifetimes of 1.85 ms at 300 K and 25.16 ms at 77 K, much longer than those of reported Cu(I) MOFs. Moreover, a white light is obtained through adjusting the relative intensity of dual peaks. More importantly, NIR long persistent luminescence of Cu-MOF is observed by naked eyes under cryogenic condition. Multiple factors such as the delicate design of the D–π–A–π–D structure of ligand, the enhanced spin-orbital coupling by Cu(I) networks, and the tight packing mode of the framework promote the generation of MLCT emission and ultralong NIR room temperature phosphorescence. The combination of calculation and experiment to analyse the luminescence mechanism of Cu(I) MOFs provides ideas for the development of Cu(I)-based intelligently responsive materials with RTP properties. 相似文献