全文获取类型
收费全文 | 126篇 |
免费 | 4篇 |
专业分类
化学工业 | 31篇 |
机械仪表 | 2篇 |
建筑科学 | 2篇 |
能源动力 | 2篇 |
轻工业 | 6篇 |
水利工程 | 5篇 |
无线电 | 10篇 |
一般工业技术 | 31篇 |
冶金工业 | 22篇 |
自动化技术 | 19篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 3篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有130条查询结果,搜索用时 15 毫秒
1.
2.
Large woody debris (LWD) can increase stream habitat heterogeneity by providing structure, altering flow patterns, enhancing sediment deposition, forming pools and retaining organic matter. In North America, the role of LWD has been studied extensively in streams of mature forests (e.g. Pacific Northwest), but few studies have assessed LWD in streams of younger forests (e.g. Midwestern USA). Our objectives were to: (1) quantify the volume and abundance of LWD in a set of Midwestern streams; (2) evaluate possible factors influencing LWD quantity; (3) identify the functional roles of LWD; and (4) compare LWD levels in the upper Midwest to those elsewhere in North America. In 2002 and 2003, we measured LWD and geomorphological variables in 15 low‐gradient streams draining previously logged watersheds in the Upper Peninsula of Michigan. Mean (±SE) LWD volume (0.77 ± 0.12 m3 100 m−2) and abundance (33 ± 3 pieces 100 m−1) were 71% and 10% lesser, respectively, than in streams of similar gradient elsewhere in North America. Channel shape (width:depth ratio) explained 30% of the variation in LWD volume (multiple stepwise regression, P = 0.015) while LWD length and length:channel width combined, explained 72% of the variation in LWD density (multiple stepwise regression, P < 0.0001). About 50% of the LWD either stored sediment or stabilized banks and 14% of the LWD formed pools, although pool density was not significantly related to LWD volume or density. LWD levels, overall, were low in upper Midwestern streams, but the relative importance of that LWD to ecosystem function may be magnified in these wood‐poor systems. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
Bordiga S. Ugliengo P. Damin A. Lamberti C. Spoto G. Zecchina A. Spanò G. Buzzoni R. Dalloro L. Rivetti F. 《Topics in Catalysis》2001,15(1):43-52
Defective silicalite, an efficient and selective catalyst in the gas phase Beckmann rearrangement reaction, has been characterised by infrared spectroscopy and by molecular modelling techniques. We report a detailed IR study on the effect of outgassing treatments at increasing temperature on silanols bands and on framework modes. The effect of a temperature decrease up to 100 K (during the IR measurement) on the H-bonding interactions has also been investigated. The interaction of silanols with mesitylene, a probe molecule which cannot penetrate the channels, has been studied in order to distinguish between internal and external OH groups. Molecular mechanics and ab initio methods have also been used to model the structure and the vibrational features of a properly designed nest in order to support the assignments of the IR spectrum. 相似文献
4.
A. Zecchina F. Geobaldo C. Lamberti S. Bordiga G. Turnes Palomino C. Otero Areán 《Catalysis Letters》1996,42(1-2):25-33
Fourier transform IR spectroscopy of CO and N2, adsorbed at liquid nitrogen temperature, was used to characterize an MFI-type H-FeZSM-5 ferrisilicate which was synthesized with a Si/Fe ratio of 50. Thermal treatment of this material at 773 and 973 K was performed in order to follow formation of extraframework species. On samples fired at 773 K Brønsted acid sites were present which gave an O-H stretching band at 3630 cm–1. These hydroxyl groups formed adducts with both probe molecules, which were monitored by the corresponding bathochromic shift, . Corresponding values for adsorbed CO and N2 were = –270 and = – 100, respectively. Increasing the firing temperature up to 973 K led to complete removal of iron from the zeolite framework, and consequent disappearance of Brønsted acidity. In this process, extraframework iron oxide species were formed which were also characterized by IR spectroscopy of the adsorbed probe molecules. Both CO and N2 gave Lewis-type adducts with coordinatively unsaturated Fe3+ ions present in the extraframework material. A comparison is made with results of a previous study on the H-GaZSM-5 isomorph. 相似文献
5.
Structural characterization of Ti centres in Ti-silicalite and reaction mechanisms in cyclohexanone ammoximation 总被引:3,自引:0,他引:3
A. Zecchina S. Bordiga C. Lamberti G. Ricchiardi C. Lamberti G. Ricchiardi D. Scarano G. Petrini G. Leofanti M. Mantegazza 《Catalysis Today》1996,32(1-4):97-106
The main results obtained by means of many physical methods (IR, Raman, UV-Vis and XAFS spectroscopies) concerning the structure of the Ti centre in titanium silicalite and the reaction intermediates in the ammoximation of cyclohexanone are concisely reviewed.
The Ti is in tetrahedral coordination in vacuo and expands its coordination sphere upon interaction with adsorbates. In the presence of H2O and H2O/H2O2 solutions one of the SiOTi bridges is hydrolyzed with formation of (SiO)3L2TiOH (LH2O) and (SiO)3L2TiOOH species, respectively. When NH3 is dosed on (SiO)3L2TiOOH structures (SiO)3L2TiOO−NH4+ species are formed. These species are thought to play an important role in the ammoximation reaction. The geometries of the peroxidic species (open or bridged) are discussed also on the basis of ab initio calculations. 相似文献
6.
Peter Lassig Hermann-Josef Lamberti Prof. Dr. Clemens Jochum 《WIRTSCHAFTSINFORMATIK》2003,45(2):147-156
Scoring and double-sided due diligence processes employed with vendor selection for IT infrastructure outsourcing Outsourcing opens the procurement of semi-finished products from business partners that are able to provide the respective processes in the required quality but at lower prices, e. g. because of bundling effects and specialization advantages. In particular, services that are not based on core-processes of an enterprise are well-suited for outsourcing. The evaluation of IT service outsourcing is difficult, because of its strategic position in enterprises. Against this background, this article describes a method to select a suitable vendor for IT infrastructure outsourcing employing scoring and double-sided due diligence processes. Our findings are based on experiences when selecting the vendor for outsourcing the European Information Technology Infrastructure (IT/I) area of the Deutsche Bank AG. 相似文献
7.
8.
D. Caccavo P. Apicella G. Lamberti A. A. Barba 《Chemical Engineering Communications》2017,204(12):1333-1340
One of the main aims in agriculture is to guarantee soil wellness, which is a fundamental requirement to produce high-quality crops with high yields. Focused on this aim, periodical administrations of nutrients or phytostrengtheners are often necessary. The most relevant disadvantages of these administrations are the high dosage number required and the low availability of the substance within the soil. For these reasons, a crucial goal to increase the economic and environmental sustainability of the cultivation process is to reduce the dosage number, which can be obtained increasing the active substance availability in the soil. A granular hydroxypropyl methylcellulose (HPMC) matrix, produced using the wet granulation process, was used to encapsulate a phytostrengthener and to guarantee its controlled release. The granular product was characterized in terms of granules properties and phytostrengtheners leaching within the soil. The results showed good flowability and mechanical properties of the granules as well as the possibility to reduce the product leaching with the phytostrengtheners encapsulation in the HPMC matrices. 相似文献
9.
Gianluca Paravati Andrea Sanna Fabrizio Lamberti Luigi Ciminiera 《Mobile Networks and Applications》2011,16(3):385-393
Wireless communication advances have enabled emerging video streaming applications to mobile handheld devices. For example,
it is possible to display and interact with complex 3D virtual environments on mobile devices that don’t have enough computational
and storage capabilities (e.g. smart phones, PDAs) through remote rendering techniques, where a server renders 3D data and
streams the corresponding image flow to the client. However, due to fluctuations in bandwidth characteristics and limited
mobile device CPU capabilities, it is extremely challenging to design effective systems for streaming interactive multimedia
over wireless networks. This paper presents a novel approach based on a controller that can automatically adjust streaming
parameters basing on feedback measures from the client device. Experimental results prove the effectiveness of the proposed
solution in coping with bandwidth changes, thus providing high Quality of Service (QoS) in remote visualizations. 相似文献
10.