全文获取类型
收费全文 | 539篇 |
免费 | 12篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 87篇 |
机械仪表 | 3篇 |
建筑科学 | 9篇 |
能源动力 | 20篇 |
轻工业 | 26篇 |
水利工程 | 4篇 |
无线电 | 91篇 |
一般工业技术 | 58篇 |
冶金工业 | 11篇 |
原子能技术 | 1篇 |
自动化技术 | 236篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 31篇 |
2012年 | 35篇 |
2011年 | 48篇 |
2010年 | 40篇 |
2009年 | 42篇 |
2008年 | 38篇 |
2007年 | 31篇 |
2006年 | 32篇 |
2005年 | 18篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有551条查询结果,搜索用时 15 毫秒
51.
Man Lung Yiu Yufei Tao Nikos Mamoulis 《The VLDB Journal The International Journal on Very Large Data Bases》2008,17(3):379-400
Existing spatiotemporal indexes suffer from either large update cost or poor query performance, except for the B x -tree (the state-of-the-art), which consists of multiple B +-trees indexing the 1D values transformed from the (multi-dimensional) moving objects based on a space filling curve (Hilbert, in particular). This curve, however, does not consider object velocities, and as a result, query processing with a B x -tree retrieves a large number of false hits, which seriously compromises its efficiency. It is natural to wonder “can we obtain better performance by capturing also the velocity information, using a Hilbert curve of a higher dimensionality?”. This paper provides a positive answer by developing the B dual -tree, a novel spatiotemporal access method leveraging pure relational methodology. We show, with theoretical evidence, that the B dual -tree indeed outperforms the B x -tree in most circum- stances. Furthermore, our technique can effectively answer progressive spatiotemporal queries, which are poorly supported by B x -trees. 相似文献
52.
Vegetables and fruits have been recognized as a healthy and nutritive value food, with both a noticeable rise in consumption nowadays and greater frequency of foodborne illnesses associated with fresh produce. Current sanitation disinfectants fail to adequately control common spoilage microorganisms as well as potential harmful human pathogens. Alternative and effective disinfectants are being sought, with ozone being a viable alternative to traditional disinfectants. Despite the considerable commercial interest that ozone has attracted, several contradictions regarding the ozone efficiency are often found in the literature and further research is still needed to explore its potential application in the food industry as sanitizer. 相似文献
53.
Nikos Nikolopoulos Aristeidis Nikolopoulos Emmanouil Karampinis Panagiotis Grammelis 《Fuel》2011,90(1):198-214
The present paper presents a three-dimensional numerical investigation of a pulverized-fuel, tangentially-fired utility boiler located at Florina/Greece under air, partial and full oxy-fuel conditions. Heat and mass transfer and major species concentration, such as CO2, CO and O2 are calculated; whilst the results for the reference air case scenario studied are in good agreement with the corresponding operational data measured in the plant, both for combustion calculations and NOx emissions. Results for the partial and full oxy-fuel operation scenarios are in line with similar experimental and numerical investigations found in the recent literature. This numerical investigation of oxy-fuel conditions scenarios prior to their implementation under real scale conditions demonstrates the utmost of its importance, since significant results regarding the operation of a boiler in terms of lignite particle trajectories and burning rates are attained. Furthermore, NOx calculations have been performed for all the examined case studies. 相似文献
54.
The compatibility of an ethylene-acrylic rubber (R) with poly (chloroprene) (CR) and two chlorinated poly-ethylenes, containing 48 (CPE 48) and 25 (CPE 25) wt.-% chlorine, was investigated. Blends with the latter polymer were studied in the complete composition range. The techniques used were phase-contrast microscopy, differential scanning calorimetry, dynamic mechanical and stress-strain testing. The single Tg relaxation of blends and its almost linear variation with composition, together with results obtained using the techniques mentioned, support the view that the systems are miscible at the segmental level. At low rubber contents an antiplasticisation effect was observed for the R/CPE 25 system. At high rubber compositions a small reduction of crystallinity and a melting point depression of the PE phase in CPE were observed. Various equations proposed to predict the Tg of blends and their modulus using pure component data were also tested at varying compositions and temperatures. 相似文献
55.
Nikos Antonopoulos Patrick Linke Antonis Kokossis 《Chemical Engineering Communications》2005,192(10):1258-1271
This article presents a GRID framework for distributed computations in the chemical process industries. We advocate a generic agent-based GRID environment in which chemical processes can be represented, simulated, and optimized as a set of autonomous, collaborative software agents. The framework features numerous advantages in terms of scalability, software reuse, security, and distributed resource discovery and utilization. It is a novel example of how advanced distributed techniques and paradigms can be elegantly applied in the area of chemical engineering to support distributed computations and discovery functions in chemical process engineering. A prototype implementation of the proposed framework for chemical process design is presented to illustrate the concepts. 相似文献
56.
Reverse nearest neighbors in large graphs 总被引:3,自引:0,他引:3
Man Lung Yiu Dimitris Papadias Nikos Mamoulis Yufei Tao 《Knowledge and Data Engineering, IEEE Transactions on》2006,18(4):540-553
A reverse nearest neighbor (RNN) query returns the data objects that have a query point as their nearest neighbor (NN). Although such queries have been studied quite extensively in Euclidean spaces, there is no previous work in the context of large graphs. In this paper, we provide a fundamental lemma, which can be used to prune the search space while traversing the graph in search for RNN. Based on it, we develop two RNN methods; an eager algorithm that attempts to prune network nodes as soon as they are visited and a lazy technique that prunes the search space when a data point is discovered. We study retrieval of an arbitrary number k of reverse nearest neighbors, investigate the benefits of materialization, cover several query types, and deal with cases where the queries and the data objects reside on nodes or edges of the graph. The proposed techniques are evaluated in various practical scenarios involving spatial maps, computer networks, and the DBLP coauthorship graph. 相似文献
57.
Moses A. Boudourides Nikos A. Fotiades 《Dynamical Systems: An International Journal》2000,15(4):343-351
The dynamics of piecewise linear interval maps is studied with two branches, one expanding and one contracting. It is proved that such a map either has a periodic attractor or it is eventually expanding. In the latter case there exists an absolutely continuous invariant measure. 相似文献
58.
59.
Smita Dayal Matthew O. Reese Andrew J. Ferguson David S. Ginley Garry Rumbles Nikos Kopidakis 《Advanced functional materials》2010,20(16):2629-2635
The charge separation and transport dynamics in CdSe nanoparticle:poly(3‐hexylthiophene) (P3HT) blends are reported as a function of the shape of the CdSe‐nanoparticle electron acceptor (dot, rod, and tetrapod). For optimization of organic photovoltaic device performance it is crucial to understand the role of various nanostructures in the generation and transport of charge carriers. The sample processing conditions are carefully controlled to eliminate any processing‐related effects on the carrier generation and on device performance with the aim of keeping the conjugated polymer phase constant and only varying the shape of the inorganic nanoparticle acceptor phase. The electrodeless, flash photolysis time‐resolved microwave conductivity (FP‐TRMC) technique is used and the results are compared to the efficiency of photovoltaic devices that incorporate the same active layer. It is observed that in nanorods and tetrapods blended with P3HT, the high aspect ratios provide a pathway for the electrons to move away from the dissociation site even in the absence of an applied electric field, resulting in enhanced carrier lifetimes that correlate to increased efficiencies in devices. The processing conditions that yield optimum performance in high aspect ratio CdSe nanoparticles blended with P3HT result in poorly performing quantum dot CdSe:P3HT devices, indicating that the latter devices are inherently limited by the absence of the dimensionality that allows for efficient, prolonged charge separation at the polymer:CdSe interface. 相似文献