全文获取类型
收费全文 | 62202篇 |
免费 | 6657篇 |
国内免费 | 4092篇 |
专业分类
电工技术 | 5337篇 |
技术理论 | 4篇 |
综合类 | 4910篇 |
化学工业 | 7792篇 |
金属工艺 | 3741篇 |
机械仪表 | 4530篇 |
建筑科学 | 4776篇 |
矿业工程 | 1952篇 |
能源动力 | 1843篇 |
轻工业 | 4693篇 |
水利工程 | 1831篇 |
石油天然气 | 2981篇 |
武器工业 | 827篇 |
无线电 | 7441篇 |
一般工业技术 | 5681篇 |
冶金工业 | 4176篇 |
原子能技术 | 870篇 |
自动化技术 | 9566篇 |
出版年
2024年 | 316篇 |
2023年 | 970篇 |
2022年 | 1996篇 |
2021年 | 2743篇 |
2020年 | 2081篇 |
2019年 | 1594篇 |
2018年 | 1883篇 |
2017年 | 2132篇 |
2016年 | 1931篇 |
2015年 | 2920篇 |
2014年 | 3570篇 |
2013年 | 4154篇 |
2012年 | 4876篇 |
2011年 | 5307篇 |
2010年 | 4758篇 |
2009年 | 4402篇 |
2008年 | 4587篇 |
2007年 | 4382篇 |
2006年 | 3778篇 |
2005年 | 3025篇 |
2004年 | 2093篇 |
2003年 | 1480篇 |
2002年 | 1370篇 |
2001年 | 1166篇 |
2000年 | 958篇 |
1999年 | 749篇 |
1998年 | 1016篇 |
1997年 | 684篇 |
1996年 | 487篇 |
1995年 | 351篇 |
1994年 | 269篇 |
1993年 | 219篇 |
1992年 | 114篇 |
1991年 | 82篇 |
1990年 | 61篇 |
1989年 | 57篇 |
1988年 | 57篇 |
1987年 | 39篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 31篇 |
1979年 | 10篇 |
1977年 | 44篇 |
1976年 | 99篇 |
1959年 | 7篇 |
1955年 | 4篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Holding strategies are among the most commonly used operation control strategies in transit systems. In this paper, a dynamic
holding strategy is developed, which consists of two major steps: (1) judging whether an early bus should be held, and (2) optimizing
the holding times of the held bus. A model based on support vector machine (SVM), which contains four input variables (time-of-day,
segment, the latest speed on the next segment, and the bus speed on the current segment) for forecasting the early bus departure
times from the next stop is also developed. Then, in order to determine the optimal holding times, a model aiming to minimize
the user costs is constructed and a genetic algorithm is used to optimize the holding times. Finally, the dynamic holding
strategy proposed in this study is illustrated with the microscopic simulation model Paramics and some conclusions are drawn.
相似文献
Bin YuEmail: |
992.
Towards capacity and profit optimization of video-on-demand services in a peer-assisted IPTV platform 总被引:1,自引:0,他引:1
Yih-Farn Chen Yennun Huang Rittwik Jana Hongbo Jiang Michael Rabinovich Jeremy Rahe Bin Wei Zhen Xiao 《Multimedia Systems》2009,15(1):19-32
This paper studies the conditions under which peer-to-peer (P2P) technology may be beneficial in providing IPTV services over
typical network architectures. It has three major contributions. First, we contrast two network models used to study the performance
of such a system: a commonly used logical “Internet as a cloud” model and a “physical” model that reflects the characteristics
of the underlying network. Specifically, we show that the cloud model overlooks important architectural aspects of the network
and may drastically overstate the benefits of P2P technology. Second, we propose an algorithm called Zebra that pre-stripes
content across multiple peers during idle hours to speed up P2P content delivery in an IPTV environment with limited upload
bandwidth. We also perform simulations to measure Zebra’s effectiveness at reducing load on the content server during peak
hours. Third, we provide a cost-benefit analysis of P2P video content delivery, focusing on the profit trade-offs for different
pricing/incentive models rather than purely on capacity maximization. In particular, we find that under high volume of video
demand, a P2P built-in incentive model performs better than any other model, while the conventional no-P2P model generates
more profits when the request rate is low. The flat-reward model generally falls in between the usage-based model and the
built-in model in terms of profitability except for low request rates. We also find that built-in and flat-reward models are
more profitable than the usage-based model for a wide range of subscriber community sizes.
Funding for J. Rahe’s research has been provided by AT&T Labs, the State of California under the MICR Oprogram, and by the
Toshiba Corporation.
Zhen Xiao is partially supported by China MOST project (2006BAH02A10). 相似文献
993.
994.
995.
996.
997.
998.
999.
1000.
医学成像仪器产生12位的体数据,然而普通显示器只支持8位的灰度图。如果使用普通显示器来显示医学图像,显卡会自动将这些12位数据转化成8位数据,这就造成了数据动态范围被压缩。解决这一问题,在2D领域通常使用昂贵的医学专用灰阶显示器。在3D领域却限制了医生使用三维可视化软件。尝试将一些在2D图像处理中使用的图像增强技术如加权平均模板,不同程度曝光等来实现色调映射算法等应用到三维体数据的显示当中,通过种种复杂的数据变换,使得在普通显示器上显示的8位灰度图呈现出更高的动态范围,得到更为生动、更加丰富的显示效果。这种技术也可以实现任意位数的转化,使得12位显示器的显示效果也可以得到增强。 相似文献