全文获取类型
收费全文 | 1904篇 |
免费 | 132篇 |
国内免费 | 53篇 |
专业分类
电工技术 | 114篇 |
综合类 | 148篇 |
化学工业 | 296篇 |
金属工艺 | 91篇 |
机械仪表 | 82篇 |
建筑科学 | 182篇 |
矿业工程 | 33篇 |
能源动力 | 59篇 |
轻工业 | 120篇 |
水利工程 | 33篇 |
石油天然气 | 142篇 |
武器工业 | 12篇 |
无线电 | 160篇 |
一般工业技术 | 257篇 |
冶金工业 | 110篇 |
原子能技术 | 28篇 |
自动化技术 | 222篇 |
出版年
2024年 | 11篇 |
2023年 | 34篇 |
2022年 | 56篇 |
2021年 | 81篇 |
2020年 | 74篇 |
2019年 | 80篇 |
2018年 | 52篇 |
2017年 | 60篇 |
2016年 | 53篇 |
2015年 | 64篇 |
2014年 | 72篇 |
2013年 | 114篇 |
2012年 | 125篇 |
2011年 | 141篇 |
2010年 | 96篇 |
2009年 | 101篇 |
2008年 | 95篇 |
2007年 | 80篇 |
2006年 | 111篇 |
2005年 | 81篇 |
2004年 | 55篇 |
2003年 | 28篇 |
2002年 | 44篇 |
2001年 | 31篇 |
2000年 | 47篇 |
1999年 | 37篇 |
1998年 | 57篇 |
1997年 | 43篇 |
1996年 | 32篇 |
1995年 | 32篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有2089条查询结果,搜索用时 0 毫秒
1.
2.
3.
Ming-yan Liu Wen Leng Ai-hong Qiang 《Chemical Engineering and Processing: Process Intensification》2008,47(12):2066-2075
In this work, the instantaneous data of inner wall temperatures obtained at given axial positions but for different heated tubes or at various axial positions but at the same heated tube in a tube-bank fluidized bed evaporator with a vapor–liquid–solid external natural circulation flow were analyzed by employing linear and nonlinear time series analysis methods, including correlation dimension and Kolmogorov entropy analyses besides time domain, power spectrum and autocorrelation analyses. It is found that nonlinear characteristics of the wall temperature time series vary with spatial position in the evaporator at given operation conditions, and thus the multi-phase flow boiling behavior. However, the signals obtained at given axial position but different heated tubes in the evaporator exhibit more similar nonlinear evolution behavior, and those measured in the same heated tube but at different axial heights in the evaporator undergo more distinct nonlinear dynamic behavior. Multi-scale phenomena in different spatial positions are also found and discussed. These transient aspects of inner wall temperatures are closely related to the average holdup of solid particles and motion of vapor bubbles in vapor–liquid–solid flow. These results can provide some valuable information on the system modeling and controlling from the point of view of nonlinearity. 相似文献
4.
The effects of boiling Aqua Regia (AQ), N2/Cl2 plasma followed by AQ and O2 plasma followed by AQ surface treatments prior to Ni/Au (20 nm/20 nm) metallization to p-GaN:Mg (∼ 3 × 1017 cm− 3) have been investigated. N2/Cl2 plasma was employed in a bid to lower the Ga/N and O/Ga ratios of the GaN surface to improve the contact properties to p-GaN, while O2 plasma was employed as an alternative to incorporate O into the Ni/Au system. Results show that a low Ga/N ratio does not necessarily correspond to a better contact. The positive effect of O2 over N2 anneal is observed only for the AQ-treated sample, although the mechanisms responsible for its positive effect: NiO formation and Ni/Au layer-reversal were observed for all O2-annealed contacts. We conclude that the effect of O2 anneal on the Ni/Au contact is dependant on the p-GaN surface prior to metallization. 相似文献
5.
冷英男 《辽宁石油化工大学学报》1994,(3)
提出了一个简单的理论模型.旨在为数据处理系统的性能评价提出一个理论框架.以此框架为基础,可形成实用的简单评估方法.该模型只含两个参数,它们是统计量,可用统计方法确定. 相似文献
6.
在我国经济快速发展的大背景下,能源(水、电、油)的消耗在企业中所占的比重越来越高,也受到愈来愈大的重视。同时也由于房地产的快速发展需求,中央空调的市场需求呈现强劲的增长。在市场容量不断增大的吸引下,越来越多的厂家加入到商用中央空调的领域。变频技术应用于中央空调系统,对提升中央空调自动化水平、降低能耗.减少对电网的冲击,延长机械及管网的使用寿命,都具有重要的意义。 相似文献
7.
Tree-based partitioning of date for association rule mining 总被引:1,自引:1,他引:0
The most computationally demanding aspect of Association Rule Mining is the identification and counting of support of the frequent sets of items that occur together sufficiently often to be the basis of potentially interesting rules. The task increases in difficulty with the scale of the data and also with its density. The greatest challenge is posed by data that is too large to be contained in primary memory, especially when high data density and/or low support thresholds give rise to very large numbers of candidates that must be counted. In this paper, we consider strategies for partitioning the data to deal effectively with such cases. We describe a partitioning approach which organises the data into tree structures that can be processed independently. We present experimental results that show the method scales well for increasing dimensions of data and performs significantly better than alternatives, especially when dealing with dense data and low support thresholds.
Shakil Ahmed received a first class BSc (Hons) degree from Dhaka University, Bangladesh, in 1990; and an MSc (first class), also Dhaka University, in 1992. He received his PhD from The University of Liverpool, UK, in 2005. From 2000 onwards he is a member of the Data Mining Group at the Department of Computer Science of the University of Liverpool, UK. His research interests include data mining, Association Rule Mining and pattern recognition.
Frans Coenen has been working in the field of Data Mining for many years and has written widely on the subject. He received his PhD from Liverpool Polytechnic in 1989, after which he took up a post as a RA within the Department of Computer Science at the University of Liverpool. In 1997, he took up a lecturing post within the same department. His current Data Mining research interests include Association rule Mining, Classification algorithms and text mining. He is on the programme committee for ICDM'05 and was the chair for the UK KDD symposium (UKKDD'05).
Paul Leng is professor of e-Learning at the University of Liverpool and director of the e-Learning Unit, which is responsible for overseeing the University's online degree programmes, leading to degrees of MSc in IT and MBA. Along with e-Learning, his main research interests are in Data Mining, especially in methods of discovering Association Rules. In collaboration with Frans Coenen, he has developed efficient new algorithms for finding frequent sets and is exploring applications in text mining and classification. 相似文献
8.
B. P. Somerday Yang Leng R. P. Gangloff 《Fatigue & Fracture of Engineering Materials & Structures》1995,18(5):565-582
Abstract—The plane-strain initiation and growth fracture toughnesses of powder-metallurgy-processed, SiC particulate-reinforced 2009 plate were measured at temperatures from 25°C to 316°C. Initiation toughness from electrical potential monitoring ( K JICi ) is 18 MPa°m at 25°C, and is nearly constant to 220°C before decreasing sharply to 6 MPa°m at 316°C. Growth toughness, given by the tearing modulus ( T R ), is less than 3 from 25°C to 125°C, and increases dramatically above 200°C. The magnitude and temperature dependence of initiation toughness depend on detection of the critical fracture event. Standard measures of toughness K IC and K JIC exceed K JICi and increase to a plateau with increasing temperature. The fracture mode for the composite is microvoid nucleation, growth and coalescence at all temperatures. Void nucleation is associated with SiC; such particles both crack and create stress and plastic strain concentrations that rupture the interface or adjacent matrix, particularly at corners. Matrix plasticity and cavitation increase with increasing temperature. Void growth is regular at all temperatures, but limited by adjacent SiC particles. Both K JICi and T R are governed by the temperature-dependent crack-tip plastic stress and strain fields, and the intrinsic damage resistance of the composite microstructure. 相似文献
9.
In this paper, the photocatalytic activity of industrial titanium dioxide (TiO2) based nacreous pigments was researched as functional building materials for photocatalytic NO remove. Three industrial TiO2 based nacreous pigments were selected to estimate the photocatalytic activity for NO remove. This study is a good proof that pearlescent pigments can eliminate NO, and its performance is positively correlated with its titanium dioxide content. And this research will widen the application of nacreous pigments in functional building materials, and provide a new way to eliminate in door nitric oxide pollution. 相似文献
10.