全文获取类型
收费全文 | 91427篇 |
免费 | 14020篇 |
国内免费 | 9102篇 |
专业分类
电工技术 | 9722篇 |
综合类 | 10246篇 |
化学工业 | 2737篇 |
金属工艺 | 2172篇 |
机械仪表 | 9913篇 |
建筑科学 | 3854篇 |
矿业工程 | 1979篇 |
能源动力 | 1234篇 |
轻工业 | 2299篇 |
水利工程 | 1264篇 |
石油天然气 | 1460篇 |
武器工业 | 1373篇 |
无线电 | 21962篇 |
一般工业技术 | 8676篇 |
冶金工业 | 1778篇 |
原子能技术 | 1200篇 |
自动化技术 | 32680篇 |
出版年
2024年 | 294篇 |
2023年 | 1420篇 |
2022年 | 2382篇 |
2021年 | 2931篇 |
2020年 | 2925篇 |
2019年 | 2208篇 |
2018年 | 2121篇 |
2017年 | 3068篇 |
2016年 | 3439篇 |
2015年 | 4115篇 |
2014年 | 5985篇 |
2013年 | 5454篇 |
2012年 | 7358篇 |
2011年 | 7670篇 |
2010年 | 6224篇 |
2009年 | 6297篇 |
2008年 | 6631篇 |
2007年 | 7554篇 |
2006年 | 6522篇 |
2005年 | 5579篇 |
2004年 | 4546篇 |
2003年 | 3785篇 |
2002年 | 2931篇 |
2001年 | 2450篇 |
2000年 | 1958篇 |
1999年 | 1520篇 |
1998年 | 1178篇 |
1997年 | 1186篇 |
1996年 | 873篇 |
1995年 | 743篇 |
1994年 | 651篇 |
1993年 | 515篇 |
1992年 | 376篇 |
1991年 | 281篇 |
1990年 | 278篇 |
1989年 | 194篇 |
1988年 | 166篇 |
1987年 | 114篇 |
1986年 | 91篇 |
1985年 | 91篇 |
1984年 | 96篇 |
1983年 | 69篇 |
1982年 | 57篇 |
1981年 | 34篇 |
1980年 | 21篇 |
1979年 | 17篇 |
1977年 | 12篇 |
1973年 | 11篇 |
1964年 | 10篇 |
1959年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
Fast image codecs are a current need in applications that deal with large amounts of images. Graphics Processing Units (GPUs) are suitable processors to speed up most kinds of algorithms, especially when they allow fine-grain parallelism. Bitplane Coding with Parallel Coefficient processing (BPC-PaCo) is a recently proposed algorithm for the core stage of wavelet-based image codecs tailored for the highly parallel architectures of GPUs. This algorithm provides complexity scalability to allow faster execution at the expense of coding efficiency. Its main drawback is that the speedup and loss in image quality is controlled only roughly, resulting in visible distortion at low and medium rates. This paper addresses this issue by integrating techniques of visually lossless coding into BPC-PaCo. The resulting method minimizes the visual distortion introduced in the compressed file, obtaining higher-quality images to a human observer. Experimental results also indicate 12% speedups with respect to BPC-PaCo. 相似文献
2.
3.
基于电信运营商数字化转型,系统性地提出了数据驱动的云网发展规划体系,以及六大关键数字化能力构建,设计和实现了一种云网规划数字化平台,该平台可用于实现目标网络精细规划、边缘计算精准预测等场景,并探讨了数字孪生在规划领域的应用前景,对运营商推进云网融合战略、推进高质量发展具有指导和参考意义。 相似文献
4.
Accurate and timely network traffic measurement is essential for network status monitoring, network fault analysis, network intrusion detection, and network security management. With the rapid development of the network, massive network traffic brings severe challenges to network traffic measurement. However, existing measurement methods suffer from many limitations for effectively recording and accurately analyzing big-volume traffic. Recently, sketches, a family of probabilistic data structures that employ hashing technology for summarizing traffic data, have been widely used to solve these problems. However, current literature still lacks a thorough review on sketch-based traffic measurement methods to offer a comprehensive insight on how to apply sketches for fulfilling various traffic measurement tasks. In this paper, we provide a detailed and comprehensive review on the applications of sketches in network traffic measurement. To this end, we classify the network traffic measurement tasks into four categories based on the target of traffic measurement, namely cardinality estimation, flow size estimation, change anomaly detection, and persistent spreader identification. First, we briefly introduce these four types of traffic measurement tasks and discuss the advantages of applying sketches. Then, we propose a series of requirements with regard to the applications of sketches in network traffic measurement. After that, we perform a fine-grained classification for each sketch-based measurement category according to the technologies applied on sketches. During the review, we evaluate the performance, advantages and disadvantages of current sketch-based traffic measurement methods based on the proposed requirements. Through the thorough review, we gain a number of valuable implications that can guide us to choose and design proper traffic measurement methods based on sketches. We also review a number of general sketches that are highly expected in modern network systems to simultaneously perform multiple traffic measurement tasks and discuss their performance based on the proposed requirements. Finally, through our serious review, we summarize a number of open issues and identify several promising research directions. 相似文献
5.
Today, utility meters for water are tested for measurement behavior at stable operating conditions at specified flow rates as part of the approval process. The measurement error that occurs during start and stop or when changing between flow rates may not be taken into account. In addition, there are new technologies whose measuring behavior under real-world conditions is only known to a limited extend. To take these facts into account, a new method has been developed and tested to determine the measurement behavior of water meters under dynamic load profiles as they occur in the real application. For this purpose, a test rig for flow rate measurement was extended by a cavitation nozzle apparatus and the generation of dynamic load profiles was validated. For the cavitation nozzles used, possible factors influencing the flow rate, such as temperature and purity of the water as well as the upstream pressure were investigated. Using different types of domestic water meters, the applicability of the dynamic test procedure was demonstrated and the measurement behavior of the meters was characterised. 相似文献
6.
《International Journal of Hydrogen Energy》2022,47(56):23762-23771
Limiting current density at different temperatures, backpressures, and balance gases can be used to separate molecular diffusion resistance, Knudsen diffusion resistance and local transport resistance of membrane electrode assembly (MEA). However, the measurement of limiting current density has no unified protocol. The diverse choices in the literature, either in the control of current or voltage or in the atmosphere like relative humidity and O2 concentrations, make it difficult to compare the results and identify the true bottleneck hindering the mass transport. In this work, the current-voltage curves obtained by current scanning/stepping and voltage scanning/stepping methods under dilute O2 of different concentrations and a wide range of relative humidity were measured and analyzed systematically. It is found that the voltage stepping method is superior to the other three ways of control for the reliable determination of the limiting current density. Aided with simultaneous electrochemical impedance spectroscopy measurement, the limiting current density can be determined with pinpoint accuracy. When the limiting current density is just used to qualitatively evaluate different MEA, the voltage scanning method can be used instead for its high time efficiency. The selection of the atmosphere also plays an important role in suppressing the distortion from excessive water and reducing the spurious contribution from proton conduction resistance. It is found that O2 concentrations at 0.5 vol% and relative humidity at 90% can give the best estimation of O2 transport resistance in membrane electrode assembly. 相似文献
7.
现有的图像修复方法在处理大面积缺失或高度纹理化的图像时,通常会产生扭曲的结构或与周围区域不一致的模糊纹理,无法重建合理的图像结构。为此,提出了一种基于推理注意力机制的二阶段网络图像修复方法。首先通过边缘生成网络生成合理的幻觉边缘信息,然后在图像补全网络完成图像的重建工作。为了进一步生成视觉效果更逼真的图像,提高图像修复的精确度,在图像补全网络采用推理注意力机制,有效控制了生成特征的不一致性,从而生成更有效的信息。所提方法在多个数据集上进行了实验验证,结果表明该图像修复方法的结构相似性指数达到了88.9%,峰值信噪比达到了25.56 dB,与现有的图像修复方法相比,该方法具有更高的图像修复精确度,生成的图像更逼真。 相似文献
8.
在传统的轮胎表面缺陷依靠人工检测,存在劳动强度高、受人的主观影响大以及效率低下的问题。针对这一现象,研究了一种基于机器视觉的轮胎表面缺陷3D检测系统。该系统依靠机器视觉系统获取检测轮胎的表面图像,然后创建3D模型、判定缺陷类型,最终实现实时自动预警,为轮胎生产商提供一种自动化检测方案。系统集成了先进的技术、软件和工具,配套的信息管控系统可以对轮胎型号和生产数据进行采集、存储、分析,以便在生产过程中实现更高效、更可靠的质量控制,具有较高的实际应用推广价值。 相似文献
9.
10.
Michael Lommel Vera Froese Moritz Sieber Marvin Jentzsch Tim Bierewirtz Ümit Hasirci Tim Rese Josef Seefeldt Sebastian Schimek Ulrich Kertzscher Christian Oliver Paschereit 《Indoor air》2021,31(6):1860-1873
The SARS-CoV-2 pandemic has created a great demand for a better understanding of the spread of viruses in indoor environments. A novel measurement system consisting of one portable aerosol-emitting mannequin (emitter) and a number of portable aerosol-absorbing mannequins (recipients) was developed that can measure the spread of aerosols and droplets that potentially contain infectious viruses. The emission of the virus from a human is simulated by using tracer particles solved in water. The recipients inhale the aerosols and droplets and quantify the level of solved tracer particles in their artificial lungs simultaneously over time. The mobile system can be arranged in a large variety of spreading scenarios in indoor environments and allows for quantification of the infection probability due to airborne virus spreading. This study shows the accuracy of the new measurement system and its ability to compare aerosol reduction measures such as regular ventilation or the use of a room air purifier. 相似文献