全文获取类型
收费全文 | 136篇 |
免费 | 3篇 |
专业分类
化学工业 | 36篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 10篇 |
能源动力 | 9篇 |
轻工业 | 24篇 |
无线电 | 5篇 |
一般工业技术 | 14篇 |
冶金工业 | 8篇 |
自动化技术 | 29篇 |
出版年
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有139条查询结果,搜索用时 15 毫秒
1.
The energy balance is discussed for the complex case of bronze or marble statuary horses and particularly the four horses of San Marco in Venice. Having computed the coefficient of exchange between bronze and the atmosphere, the daytime overheating is evaluated for different seasons and orientations of the statues. The equations can be solved with reasonable approximation and both the past and future overheatings can be evaluated as a function of the growing surface weathering and blackening. Therefore, the present analysis points out the chief characteristics of both the diurnal cycle and the variation over the centuries of the response of the bronzes to atmospheric variables. 相似文献
2.
Angela S. Rocha Arnaldo C. Faro Jr. Laetitia Oliviero Jacob Van Gestel Franoise Maug 《Journal of Catalysis》2007,252(2):321-334
The activity of NiMoS catalysts supported on niobia, alumina, and niobia/alumina was compared for the thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline (2,6-DMA) hydrodenitrogenation (HDN) reactions. To evaluate the acidity of the supports and identify the nature of the sulfide sites, adsorption of 2,6-dimethylpyridine, pyridine, and CO was performed and followed by IR spectroscopy. This study has shown that with niobia as a support, the activity of NiMoS catalysts in thiophene HDS and in HDN of 2,6-DMA was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. Moreover, it has been shown that on a niobia/alumina support, the formation of the NiMoS phase can be directly linked to the presence of alumina not covered by niobia. However, niobia is an interesting support for the HDN of 2,6-DMA, because it favors the formation of xylene through direct ammonia elimination involving low H2 consumption. The activity for xylene formation on niobia is linked to the electron-deficient nature of the Mo sulfide site, as demonstrated by CO adsorption followed by IR. 相似文献
3.
4.
This paper evaluates emissions to the atmosphere of biologically available nitrogen compounds in a region characterized by intensive sugar cane biofuel ethanol production. Large emissions of NH3 and NOx, as well as particulate nitrate and ammonium, occur at the harvest when the crop is burned, with the amount of nitrogen released equivalent to approximately 35% of annual fertilizer-N application. Nitrogen oxides concentrations show a positive association with fire frequency, indicating that biomass burning is a major emission source, with mean concentrations of NOx doubling in the dry season relative to the wetseason. During the dry season biomass burning is a source of NH3, with other sources (wastes, soil, biogenic) predominant during the wet season. Estimated NO2-N, NH3-N, NO3- -N and NH4+ -N emission fluxes from sugar cane burning in a planted area of ca. 2.2 x 10(6) ha are 11.0, 1.1, 0.2, and 1.2 Gg N yr(-1), respectively. 相似文献
5.
Ana A. Rodrigues Nilza A. Batista Vanessa P. Bavaresco Vitor Baranauskas Helder J. Ceragioli Alfredo C. Peterlevitz Arnaldo R. Santos William D. Belangero 《Carbon》2012,50(2):450-459
Polyvinyl alcohol (PVAl) hydrogel, alone and reinforced with two types of carbon nanoparticles, was studied in cultured cells to assess its potential use in treating osteochondral defects. The carbon nanoparticles were produced by hot-filament chemical vapour deposition. The carbon material was characterised with a Renishaw Invia Raman microscope system and the morphological particles were characterised with field emission scanning electron microscopy and high-resolution transmission electron microscopy. Cytotoxicity was evaluated by measuring the Vero fibroblast-type cells’ metabolic activity and studying their morphology. The osteogenic differentiation of mesenchymal stem cells obtained from rat bone marrow was evaluated by alkaline phosphatase (ALP) and alizarin red S (ARS) staining. Cell viability and morphology were assessed with thiazolyl blue tetrazolium bromide and scanning electron microscopy, respectively. The materials did not interfere with the viability, metabolic activity, morphology and spreading of either of the cell types analysed. Nodules of mineralised organic matrix were identified with ARS and ALP, confirming osteogenic differentiation. These results indicated higher concentration of ALP and mineralised matrix for PVAl with carbon nanoparticles. The results of this study indicate the potential use of carbon nanoparticles with PVAl hydrogels as orthopaedic biomaterials to treat osteochondral defects, but further in vivo investigations are still necessary. 相似文献
6.
7.
Tony Minoru Tamura Lopes Andre Augusto Ciré Cid Carvalho de Souza Arnaldo Vieira Moura 《Constraints》2010,15(2):151-189
Brazilian petrobras is one of the world largest oil companies. Recurrently, it faces a very difficult planning and scheduling problem: how to
operate a large pipeline network in order to adequately transport oil derivatives and biofuels from refineries to local markets.
In spite of being more economical and environmentally safer, the use of a complex pipeline network poses serious operational
difficulties related to resource allocation and temporal constraints. The current approaches known from the literature only
consider a few types of constraints and restricted topologies, hence they are far from being applicable to real instances
from petrobras. We propose a hybrid framework based on a two-phase problem decomposition strategy. A novel Constraint Programming (CP) model
plays a key role in modelling operational constraints that are usually overlooked in literature, but that are essential in
order to guarantee viable solutions. The full strategy was implemented and produced very adequate results when tested over
large real instances. 相似文献
8.
Personal memories composed of digital pictures are very popular at the moment. To retrieve these media items annotation is
required. During the last years, several approaches have been proposed in order to overcome the image annotation problem.
This paper presents our proposals to address this problem. Automatic and semi-automatic learning methods for semantic concepts
are presented. The automatic method is based on semantic concepts estimated using visual content, context metadata and audio
information. The semi-automatic method is based on results provided by a computer game. The paper describes our proposals
and presents their evaluations. 相似文献
9.
Universality for deterministic Timed Automata (TA) is PSPACE-complete but becomes highly undecidable when unrestricted nondeterminism is allowed. More precisely, universality for nondeterministic TA is Π11-hard and it is still open whether it is π11-complete. It is interesting to note that the entire arithmetical hierarchy is contained in this computability gap between determinism and nondeterminism. In this paper we consider three types of syntactical restrictions to nondeterministic TA, which may contribute to a better understanding of the universality problem for TA. For the first two types, which are of independent interest, the universality problem is shown to be Π11-complete. For the third one, universality is Π10-complete, which is the same as saying that the complementary problem is complete in the recursively enumerable class. We also show that all the restrictions define proper subclasses of the class of timed languages defined by nondeterministic TA; and establish the relationships between the classes. 相似文献
10.
M. J. V. Beattie Ph.D. Arnaldo Ismay 《JOM Journal of the Minerals, Metals and Materials Society》1990,42(1):31-35
Extensive batch and continuous testing has been completed using a high-temperature, nitric acid pressure leach (Redox) process for oxidizing the refractory gold-containing arsenopyrite tailings presently stockpiled at Snow Lake, Manitoba. This process has achieved up to 99% oxidation of the arsenopyrite compound and precipitated more than 90% arsenic into a stable iron-arsenic compound (resembling ferric arsenate) in less than eight minutes of overall retention time at temperatures of 195–210°C and an oxygen overpressure of 345 kPa. The oxidation step then exposes the contained gold, allowing a recovery of 91.5% in a standard carbon-in-leach circuit. The main advantages of this process are fast reaction rates, the high proportion of arsenic precipitated, and the stability of the precipitate. 相似文献