全文获取类型
收费全文 | 401篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
化学 | 1篇 |
综合类 | 1篇 |
数学 | 53篇 |
物理学 | 91篇 |
无线电 | 285篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 5篇 |
2014年 | 40篇 |
2013年 | 17篇 |
2012年 | 25篇 |
2011年 | 17篇 |
2010年 | 26篇 |
2009年 | 36篇 |
2008年 | 35篇 |
2007年 | 25篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有431条查询结果,搜索用时 15 毫秒
41.
本文提出了一种280Mb/s码率的HDTV压缩编码方案。亮度分量采用1/4亚取样配合自适应细节补传,色度分量采用1/2亚取样及R-Y/B-Y行轮换传送。在解码端,亮、色分量均采用2D内插重建复原,本方案的特点是抗误码能力强、算法简单、易于实现。实验获得了优良的重建图像质量。 相似文献
42.
在分析和讨论现有网上招投标理论和实践的基础上,利用校验机制、多方保密计算和位承诺设计了一个具有容错、保密和诚信的网上招投标协议,为解决目前网上招投标所面临的技术难题提供了一种切实可行的解决方案。 相似文献
43.
一种高达340Mbps的多速率QPSK解调器 总被引:1,自引:1,他引:0
首先讨论了遥感卫星高速数据中频接收解调系统的应用背景,然后介绍了一种新型多速率中频QPSK解调器的组成和工作原理,并给出了该设备的性能测试方法和测试结果。测试结果表明该解调器在280~340Mbps速率范围内均具有较好的误码率性能指标。 相似文献
44.
利用Bit承诺,单向函数和数字签名算法,对一种安全电子拍卖模型进行改进,提出了一种安全、简单、高效的密封式电子拍卖方案.它可以在注册中心离线的情况下,最大程度地缩小拍卖行的权力实现公共认证.同时,该方案不仅能对除中标者外的其他所有投标者的投标价进行保密,而且能有效防止拍卖行不诚实的行为. 相似文献
45.
We have investigated the return-to-zero (RZ) pulse duty cycle for single-channel Standard Single mode fiber (SSMF), Non Zero Dispersion shifted fibers (normal NZDSF and anomalous NZDSF fiber) for 10 Gbps optical fiber communication system. We give a comprehensive look on the behavior of variable duty cycle optical RZ pulse indicating that lowest bit error rate for duty cycle 0.8 among the duty cycle values 0.2, 0.4, 0.6 and 0.8 investigated for the case of SSMF. The single repeaterless mode fiber length is increased from existing 55 km at duty cycle 0.2 to fiber length 85 km by keeping duty cycle at 0.8. The result is also emphasized through the 10 dB Q value improvement and corresponding improvement in average eye opening diagram. The normal NZDSF show similar improvement but at greater fiber length, it offers BER 10−9 at length 110 km with duty cycle 0.2. NZDSF operating length can further be increased to length 160 km by keeping duty cycle 0.8. The corresponding 8 dB Q value improvement and Average eye opening improvement also supports the result through its graphical variation. Thirdly Anomalous NZDSF for same optical communication system showed that 0.2 duty cycle value give operational length of 130 km which could be extended to 160 km if 0.8 duty cycle is kept. The corresponding 8 dB Q value improvement, average eye-opening improvement endorsed the fact in the graphs. 相似文献
46.
Michal P. Dlubek Andrew J. Phillips Eric C. Larkins 《Optical and Quantum Electronics》2008,40(8):561-575
A new and straightforward optical signal quality metric, which is based on the approximation of the analytical probability
density function by its Laguerre expansion, is proposed. This expansion uses statistical moments to approximate the true statistics,
but, unlike the well-known Gaussian approximation, higher order moments can be used as well. The quality of the proposed metric
is discussed and the metric is compared with the Gaussian approximation. It is shown that the new metric provides not only
a good estimation of the bit error rate in the range of practical interest but, contrary to the Gaussian approximation, correctly
estimates optimum decision threshold and accurately pictures the shape of the noise distribution. 相似文献
47.
Gains in storage density in magnetic recording have fundamentally been achieved by scaling—reduced geometrical dimensions under the assumption that the recording physics does not change if all dimensions are scaled appropriately. It is becoming clear that evidence of the breakdown of scaling is now seen. We will here discuss ways to break the constraints on magnetic recording set by scaling. In particular, we will discuss energy-assisted recording, domain-wall-assisted recording, and bit-patterned media, with some emphasis on recording system considerations. 相似文献
48.
The haploid–diploid cycle where, under unfavorable conditions the population becomes diploid, is modeled by a Monte-Carlo method in the framework of the Jan–Stauffer–Moseley hypothesis. Diploidy and sex may have first arisen as a way to escape death, when a simple unicellular individual is threatened by too many deleterious mutations. Using a bit string model, we find that in a system where competition is present (through the Verhulst factor), diploids dominate. In this case the transition from haploid to essentially diploid population takes place in a short time interval reminiscent of phase transitions in physical systems. 相似文献
49.
This paper proposes a protocol for lottery and a protocol for auction on quantum Blockchain. Our protocol of lottery satisfies randomness, unpredictability, unforgeability, verifiability, decentralization and unconditional security. Our protocol of auction satisfies bid privacy, posterior privacy, bids’ binding, decentralization and unconditional security. Except quantum Blockchain, the main technique involved in both protocols is quantum bit commitment. 相似文献
50.
Spatial and temporal inconsistency of depth video deteriorates encoding efficiency in three dimensional video systems. A depth video processing algorithm based on human perception is presented. Firstly, a just noticeable rendering distortion (JNRD) model is formulated by combining the analyses of the influence of depth distortion on virtual view rendering with human visual perception characteristics. Then, depth video is processed based on the JNRD model from two aspects, spatial and temporal correlation enhancement. During the process of spatial correlation enhancement, depth video is segmented into edge, foreground, and background regions, and smoothened by Gaussian and mean filters. The operations of the temporal correlation enhancement include temporal–spatial transpose (TST), temporal smoothing filter and inverse TST. Finally, encoding and virtual view rendering experiments are conducted to evaluate the proposed algorithm. Experimental results show that the proposed algorithm can greatly reduce the bit rate while it maintains the quality of virtual view. 相似文献