全文获取类型
收费全文 | 69篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 2篇 |
力学 | 7篇 |
数学 | 14篇 |
物理学 | 52篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 1篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有75条查询结果,搜索用时 156 毫秒
21.
22.
Philippe Baptiste 《Discrete Applied Mathematics》2010,158(5):583-587
The coupled tasks problem consists in scheduling n jobs on a single machine. Each job i is made of two operations with processing times ai and bi and a fixed required delay Li between them. Operations cannot overlap in time but operations of different jobs can be interleaved. The objective is to minimize the makespan of the schedule. In this note we show that the problem with identical jobs (∀i,ai=a,bi=b,Li=L) can be solved in O(logn) time when a,b,L are fixed. This problem is motivated by radar scheduling applications where tasks corresponding to transmitting radiowaves and listening to potential echoes are coupled. 相似文献
23.
Luther White Alan Shapiro Frances White 《Computational Optimization and Applications》2008,41(1):61-80
In this paper the problem of retrieving wind field information from Doppler radar data motivates the formulation of a method
to design radar network configurations. The problem of estimating wind velocities from radar data is posed and used to construct
a certain retrieval operator. This operator contains a factor that may be interpreted as an uncertainty multiplier. It depends
on the geometry of the configuration of the radar network. The uncertainty multiplier is shown to vary continuously with perturbations
of the network configuration. It is also shown to be a generalization of the Doppler angle condition used in meteorology.
Numerical examples are presented to determine a network of five radars minimizing the uncertainty multiplier for the problem.
Also, a configuration of sites is determined that maximizes the area of the Doppler region. 相似文献
24.
Manfred Thumm 《International Journal of Infrared and Millimeter Waves》2005,26(4):483-503
Gyrotron oscillators are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 1 MW gyrotrons employing synthetic diamond output windows is 5 s at 110 GHz (CPI and JAERI-TOSHIBA), 12 s at 140 GHz (FZK-CRPP-CEA-TED) and 10 s at 170 GHz (GYCOM and JAERI-TOSHIBA), with efficiencies slightly above 30%. Total efficiencies of 45–50 % have been obtained using single-stage depressed collectors (SDC). The energy world record of 160 MJ (0.89 MW at 180 s pulse length and 140 GHz) at power levels higher than 0.8 MW has been achieved by the European FZK-CRPP-CEA-TED collaboration at FZK. Operation at the 1st and the 2nd harmonic of the EC frequency enables gyrotrons to act as medium power step-tunable mm- and sub-mm wave sources in the frequency range from 38 GHz (fundamental) to 889 GHz (2nd harmonic) for plasma diagnostics, EC plasma discharges for generation of multi-charged ions, high-frequency broadband electron paramagnetic resonance (EPR) spectroscopy and medical applications. Gyrotrons have also been successfully used in materials processing. Such technological applications require gyrotrons with the following parameters: f 24 GHz, Pout = 4–50 kW, CW, 30%. Future applications which await the development of novel high-power gyro-amplifiers include high resolution radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators (supercolliders). The present paper reviews the state-of-the-art and future prospects of gyro-devices and their applications. 相似文献
25.
Michael Schilder 《Journal of statistical physics》1975,13(6):491-514
It is shown that radar and quantum mechanics may be modeled using the Kalman-Bucy state-equation observation approach. A method is given for realizing the optimal position filters. 相似文献
26.
采用双谱多类小波包特征的雷达信号聚类分选 总被引:1,自引:0,他引:1
针对现有雷达脉内特征参量对噪音敏感,难以适应复杂体制雷达聚类分选的问题,应用双谱多类小波包特征实现了宽信噪比条件下未知复杂雷达信号的高准确率聚类分选.首先对接收到的雷达信号求得双谱归一化系数,然后利用多类小波包提取双谱归一化系数的特征参量,并选取最佳小波包特征作为分选参量,最后通过提取8类雷达辐射源信号的双谱小波包特征,采用核模糊C均值聚类算法实现聚类分选.仿真结果表明:提取的特征参量在宽信噪比范围内均具有很好的分离性和稳定性,可实现复杂雷达辐射源信号的准确聚类分选. 相似文献
27.
Cloud Height, Cloud Temperature and Cloud Attenuation in Microwave and Millimeterwave Frequency Bands over Indian Tropical East Coast 总被引:1,自引:0,他引:1
S. K. Sarkar Iqbal Ahmad J. Das A. K. De 《International Journal of Infrared and Millimeter Waves》2005,26(2):329-340
Based on radar RHI (Range height indicator) measurements, cloud height has been deduced during the worst months (July–August) over Kolkata. Such cloud height results have been utilized to estimate cloud temperature. The attenuation of radiowave due to cloud in various probability levels has been determined in millimeter wave and microwave frequency bands. Such results on different probability levels are useful for satellite communication and remote sensing application over the aforesaid station in tropical India. 相似文献
28.
为满足对吸波涂层薄、轻、宽的要求,通过吸波涂层的优化设计,制备了密度较低的宽频带碳团簇型吸波涂层.该涂层为三层结构,总厚度为2.10 mm,在8~12.4GHz频率范围内,对微波的最小反射率为-42dB,其中反射率小于-10dB的工作频带达90%以上,且性能稳定,有较好的实用前景. 相似文献
29.
应用电感耦合等离子体质谱(ICP-MS)测定了收集于9个采样点的油菜蜜及其蜜源油菜花和油菜杆中Na,Mg,P,K,Ca,Mn,Zn,Rb,Sr和Ba等10种元素。在油菜蜜、油菜花和油菜杆中K,P,Ca,Mg和Na等五种元素含量均明显高于Zn,Rb,Mn,Sr和Ba,前五种元素含量大小顺序为K>P>Ca>Mg>Na,后五种元素含量在三者中的大小顺序则不尽相同。油菜花和油菜杆中K,P和Ca三种元素的含量均高于1 000 mg·kg-1,油菜花中P,Ca,Mn,Zn和Rb等五种元素的平均含量均高于油菜杆,可以初步推断油菜花富集元素的能力略强于油菜杆。在上述测定结果基础上,首次应用雷达图对油菜蜜及其蜜源油菜花和油菜杆中10种元素的关系进行了研究,主要是为了对将油菜花中元素含量用于蜂蜜溯源研究的可能性进行探索。从雷达图可以看出,10种元素在油菜蜜、油菜花和油菜杆中的星形基本类似。此研究为油菜蜜的相关研究提供基础数据,同时为利用油菜花中元素含量代替油菜蜜中元素含量进行油菜蜜溯源提供了一定的科学依据。 相似文献
30.
《Comptes Rendus Physique》2019,20(3):183-191
When designing a new radar system, standard resolution trade-offs play a major role, providing the basic parameters of the radar, such as size, update rate, and range. Besides, diversity has long been used for mitigating fading effects due to the fluctuation of targets and clutter.However, with the arrival of more flexible systems, using multiple parallel channels on transmit and receive, and wider instantaneous bandwidths, these standard trade-offs are becoming less simple—and more flexible. In this communication, we will analyse the benefits of diversity and its relations with range, Doppler, and angle, for detection and location of moving targets with wideband/wide-beam radar systems. The idea is to contribute to a better understanding of the real benefits of agile transmissions for detection/localization of moving targets, focusing on range, velocity, and angular measurement improvements, as well as on the benefits for detection of moving targets.Special attention will be given to the quality of the different wideband wide-beam sensor modes for long-range surveillance, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small target detection at long range, in difficult environments. 相似文献