全文获取类型
收费全文 | 1054篇 |
免费 | 51篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 259篇 |
金属工艺 | 12篇 |
机械仪表 | 28篇 |
建筑科学 | 53篇 |
矿业工程 | 11篇 |
能源动力 | 67篇 |
轻工业 | 131篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 89篇 |
一般工业技术 | 154篇 |
冶金工业 | 33篇 |
原子能技术 | 6篇 |
自动化技术 | 234篇 |
出版年
2023年 | 9篇 |
2022年 | 35篇 |
2021年 | 49篇 |
2020年 | 23篇 |
2019年 | 22篇 |
2018年 | 17篇 |
2017年 | 28篇 |
2016年 | 48篇 |
2015年 | 48篇 |
2014年 | 61篇 |
2013年 | 78篇 |
2012年 | 71篇 |
2011年 | 87篇 |
2010年 | 57篇 |
2009年 | 63篇 |
2008年 | 69篇 |
2007年 | 45篇 |
2006年 | 48篇 |
2005年 | 44篇 |
2004年 | 32篇 |
2003年 | 22篇 |
2002年 | 24篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1105条查询结果,搜索用时 0 毫秒
61.
Environmental exposure assessment of fluoroquinolone antibacterial agents from sewage to soil 总被引:7,自引:0,他引:7
Golet EM Xifra I Siegrist H Alder AC Giger W 《Environmental science & technology》2003,37(15):3243-3249
The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical-biological wastewater treatment was studied by mass flow analysis. In addition, the fate of FQs in agricultural soils after sludge application was investigated. Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection. FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction. Wastewater treatment resulted in a reduction of the FQ mass flow of 88-92%, mainly due to sorption on sewage sludge. A sludge-wastewater partition coefficient (log Kd approximately 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h. No significant removal of FQs occurred under methanogenic conditions of the sludge digesters. These results suggest sewage sludge as the main reservoir of FQ residues and outline the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment. Field experiments of sludge-application to agricultural land confirmed the long-term persistence of trace amounts of FQs in sludge-treated soils and indicated a limited mobility of FQs into the subsoil. 相似文献
62.
Galarza M De Mesel K Baets R Martínez A Aramburu C López-Amo M 《Applied optics》2003,42(24):4841-4846
We propose a concept for InGaAsP-InP 1.55-microm lasers integrated with spot-size converters based on modal interference between the modes of the structure formed by an active waveguide and an underlying fiber-matched antiresonant reflecting optical waveguide. Simulation results show that the spot-size converters exhibit low transformation loss, and narrowed far-field emission patterns (10 degrees x 20 degrees) and reduce the coupling loss to standard single-mode fibers from 8 to 2.6 dB over lengths approximately 200 microm shorter than the adiabatic concept. A tolerant design to fabrication variations is also proposed, which could be realized by standard processing techniques. 相似文献
63.
Approximate range aggregate queries are one of the most frequent and useful kinds of queries for Decision Support Systems
(DSS), as they are widely used in many data analysis tasks. Traditionally, sampling-based techniques have been proposed to
tackle this problem. However, their effectiveness degrade when the underlying data distribution is skewed. Another approach
based on the outlier management can limit the effect of data skews but fails to address other requirements of approximate
range aggregate queries, such as error guarantees and query processing efficiency. In this paper, we present a technique that
provides approximate answers to range aggregate queries on OLAP data cubes efficiently, with theoretical guarantees on the
errors. Our basic idea is to build different data structures to manage outliers and the rest of the data. Carefully chosen
outliers are organized in a quad-tree based indexing data structure to provide efficient access for query processing. A query-workload adaptive, tree-like synopsis data structure, called T
unable
P
artition-Tree (TP-Tree), is proposed to organize samples extracted from non-outlier data. Our experiments clearly demonstrate the merits of our
technique, by comparing with previous well-known techniques. 相似文献
64.
Sandra A. Mayén-Hernández Gerardo Torres-Delgado Rebeca Castanedo-Pérez Mario Gutiérrez Villarreal Alfredo Cruz-Orea Julio G. Mendoza Alvarez Orlando Zelaya-Angel 《Journal of Materials Science: Materials in Electronics》2007,18(11):1127-1130
ZnO + Zn2TiO4 thin films were obtained by the sol–gel method using precursor solutions with different Ti/Zn ratios in the 0.18–2.13 range.
The films were deposited on glass substrates and annealed in an open atmosphere at 550 °C. The oxide was characterized by
X-ray diffraction and photoacoustic (PA) spectroscopy. The films were constituted of polycrystalline ZnO for the lowest Ti/Zn
ratio (0.18), polycrystalline Zn2TiO4 for the 0.70 and 1.0 ratios, and mixes of both oxides for the intermediate ratios (0.32 and 0.50). For the highest ratios
studied (1.44 and 2.13), the films were amorphous. The energy band gap (Eg) values were determined from optical absorption spectra, measured by means of the PA technique spectra. Eg varied in the 3.15 eV (ZnO) to 3.70 eV (Zn2TiO4) range. 相似文献
65.
Alfredo H Saaband Steve Logan 《电子设计技术》2007,14(10):108-108,110
随着新一代的LED实现了较高的功率和效率,这些元件的应用逐渐扩展到了新的领域,如手电筒或车辆应用等.大功率LED与白炽灯泡及荧光灯管等共同应用于环境照明中. 相似文献
66.
Electrocatalytic Detection: Magnetic Bead/Gold Nanoparticle Double‐Labeled Primers for Electrochemical Detection of Isothermal Amplified Leishmania DNA (Small 2/2016) 下载免费PDF全文
67.
Carmelo Cassisi Alfredo Ferro Rosalba Giugno Giuseppe Pigola Alfredo Pulvirenti 《Information Systems》2013
Clustering is a widely used unsupervised data mining technique. It allows to identify structures in collections of objects by grouping them into classes, named clusters, in such a way that similarity of objects within any cluster is maximized and similarity of objects belonging to different clusters is minimized. In density-based clustering, a cluster is defined as a connected dense component and grows in the direction driven by the density. The basic structure of density-based clustering presents some common drawbacks: (i) parameters have to be set; (ii) the behavior of the algorithm is sensitive to the density of the starting object; and (iii) adjacent clusters of different densities could not be properly identified. In this paper, we address all the above problems. Our method, based on the concept of space stratification, efficiently identifies the different densities in the dataset and, accordingly, ranks the objects of the original space. Next, it exploits such a knowledge by projecting the original data into a space with one more dimension. It performs a density based clustering taking into account the reverse-nearest-neighbor of the objects. Our method also reduces the number of input parameters by giving a guideline to set them in a suitable way. Experimental results indicate that our algorithm is able to deal with clusters of different densities and outperforms the most popular algorithms DBSCAN and OPTICS in all the standard benchmark datasets. 相似文献
68.
Stéphane Bressan Alfredo Cuzzocrea Panagiotis Karras Xuesong Lu Sadegh Heyrani Nobari 《Journal of Parallel and Distributed Computing》2013
The widespread usage of random graphs has been highlighted in the context of database applications for several years. This because such data structures turn out to be very useful in a large family of database applications ranging from simulation to sampling, from analysis of complex networks to study of randomized algorithms, and so forth. Amongst others, Erd?s–Rényi Γv,p is the most popular model to obtain and manipulate random graphs. Unfortunately, it has been demonstrated that classical algorithms for generating Erd?s–Rényi based random graphs do not scale well in large instances and, in addition to this, fail to make use of the parallel processing capabilities of modern hardware. Inspired by this main motivation, in this paper we propose and experimentally assess a novel parallel algorithm for generating random graphs under the Erd?s–Rényi model that is designed and implemented in a Graphics Processing Unit (GPU), called PPreZER. We demonstrate the nice amenities due to our solution via a succession of several intermediary algorithms, both sequential and parallel, which show the limitations of classical approaches and the benefits due to the PPreZER algorithm. Finally, our comprehensive experimental assessment and analysis brings to light a relevant average speedup gain of PPreZER over baseline algorithms. 相似文献
69.
70.
We measured turn-taking in terms of hand and head movements and asked if the global rhythm of the participants' body activity relates to word learning. Six dyads composed of parents and toddlers (M = 18 months) interacted in a tabletop task wearing motion-tracking sensors on their hands and head. Parents were instructed to teach the labels of 10 novel objects and the child was later tested on a name-comprehension task. Using dynamic time warping, we compared the motion data of all body-part pairs, within and between partners. For every dyad, we also computed an overall measure of the quality of the interaction, that takes into consideration the state of interaction when the parent uttered an object label and the overall smoothness of the turn-taking. The overall interaction quality measure was correlated with the total number of words learned.In particular, head movements were inversely related to other partner's hand movements, and the degree of bodily coupling of parent and toddler predicted the words that children learned during the interaction. The implications of joint body dynamics to understanding joint coordination of activity in a social interaction, its scaffolding effect on the child's learning and its use in the development of artificial systems are discussed. 相似文献