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排序方式: 共有462条查询结果,搜索用时 15 毫秒
1.
2.
Wood inspection with non-supervised clustering 总被引:9,自引:0,他引:9
Abstract. The appearance of sawn timber has huge natural variations that the human inspector easily compensates for mentally when determining
the types of defects and the grade of each board. However, for automatic wood inspection systems these variations are a major
source for complication. This makes it difficult to use textbook methodologies for visual inspection. These methodologies
generally aim at systems that are trained in a supervised manner with samples of defects and good material, but selecting
and labeling the samples is an error-prone process that limits the accuracy that can be achieved. We present a non-supervised
clustering-based approach for detecting and recognizing defects in lumber boards. A key idea is to employ a self-organizing
map (SOM) for discriminating between sound wood and defects. Human involvement needed for training is minimal. The approach
has been tested with color images of lumber boards, and the achieved false detection and error escape rates are low. The approach
also provides a self-intuitive visual user interface.
Received: 16 December 2000 / Accepted: 8 December 2001
Correspondence to: O. Silvén 相似文献
3.
ZT Lalowicz M Punkkinen AH Vuorim?ki EE Ylinen A Detken LP Ingman 《Canadian Metallurgical Quarterly》1997,8(2):89-107
Expressions are derived for the initial relaxation rate 1/T1 of protons and deuterons of nontunnelling NH4 and ND4 groups reorienting about various symmetry axes in solids. The reorientation rates are modified by a trigonal, tetragonal or monoclinic distortion of the predominantly cubic hindering potential. When the rates differ sufficiently from each other, two T1 minima are observed with a characteristic ratio. Experiments were performed in NH4VO3, (NH4)2S2O8, (NH4)2PtCl4, and their deuterated modifications, which all exhibit two T1 minima. In NH4VO3 and ND4VO3 the relaxation and spectral data agree rather well with the model of trigonal distortion. Also (NH4)2S2O8 has a preferred threefold axis but there, the large tunnel splitting of protons has to be taken into account before an agreement is reached. All the purely reorientational models fail with (NH4)2PtCl4, where, instead, the ammonium groups are proposed to be ordered into domains at low temperatures. The groups inside the domains and boundary regions give rise to the high- and low-temperature T1 minima, respectively. The boundaries are also believed to give rise to the narrow component in the deuteron spectrum at low temperatures. Evidence for a proton tunnelling frequency of 32 MHz is found in (NH4)2PtCl4. 相似文献
4.
Sari M Soini Kari T Koskinen Matti J Vilenius Jaakko A Puhakka 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(8):903-909
Water hydraulic systems use water as a pressure medium and, thus, do not pose such adverse environmental impacts as oil hydraulics. Microbial deterioration of the pressure medium and biofouling of the surfaces restrict the applicability of the water‐based technology. The potential of microbial growth control by UV‐irradiation and filtration was studied in a pilot‐scale water hydraulic system. The UV‐irradiation (25 m Ws cm?2) of the pressure medium reduced the total viable counts of bacteria by 1–2 log10 cfu cm?3, whereas the total microbial cell numbers and the numbers of surface‐attached microorganisms remained unaffected. Prefiltration (1.2 µm, absolute) of the pressure medium decreased the total microbial cell number in the water phase and retarded the attachment of bacteria. The filtration during the operation (2 µm, absolute) decreased the total numbers of microbial cells and the total viable counts in the pressure medium, and microbial attachment on the surfaces. Microbial attachment was not prevented by filtration. The microbial water quality obtained by pre‐ and on‐line filtration of the pressure medium was sufficient to ensure the long‐term operation of the water hydraulic system assuming that clean work practices are complied with in assembly and during the operation. © 2002 Society of Chemical Industry 相似文献
5.
Engagement in virtual worlds has become pervasive, particularly among the young. At the same time, the number of virtual environments has increased rapidly. Due to intensifying competition, promoting sustained usage, i.e. continuance, has become a top priority for virtual world operators. Prior research has shown that network externalities play a key role in the adoption of communication technologies. However, a small amount of research has examined the role of network externalities in continued IT usage in general or with respect to the virtual world participation in particular. To fill in this gap, we examine how perceived network externalities affect the continuance of social virtual worlds. To this end, we introduce the concept of perceived aggregate network exposure (PANE). We extend the original information systems (IS) continuance model with perceived enjoyment and position PANE as a moderator. We test the model with data collected from 2134 Finnish Habbo Hotel users and employ structural equation modelling in the analysis. The results demonstrate that PANE moderates the influence of motivational factors on continued use intention and satisfaction. 相似文献
6.
Valeri Shevtsov Alexander Frolov Igor Lukashevich Eero Ylinen Pekka Malmi Matti Punkkinen 《Journal of Low Temperature Physics》1994,95(5-6):815-833
The combined techniques of ESR and NMR were used to investigate the process of ortho-para conversion in solid molecular hydrogen, containing small amounts ( 500 ppm) of hydrogen atoms as impurity. Although the impurity atoms catalyze the effective conversion of the neighboring ortho-H2, the total catalyzed conversion rate at temperatures from 2.2 K to 4.4 K is much less than expected from the rate of the H atoms recombination. A possible explanation is given in terms of the diffusion of H atoms, which is confined to some defects in the crystal. 相似文献
7.
Masoud Ebrahimzadeh Sari Granroth Sami Vuori Marko Punkkinen Mikko Miettinen Risto Punkkinen Mikhail Kuzmin Pekka Laukkanen Mika Lastusaari Kalevi Kokko 《Advanced Engineering Materials》2023,25(19):2300762
Manufacturing a low-resistive Ohmic metal contact on p-type InP crystals for various applications is a challenge because of the Fermi-level pinning via surface defects and the diffusion of p-type doping atoms in InP. Development of wet-chemistry treatments and nanoscale control of p-doping for InP surfaces is crucial for decreasing the device resistivity losses and durability problems. Herein, a proper combination of HCl-based solution immersion, which directly provides an unusual wet chemical-induced InP(100)c(2 × 2) atomic structure, and low-temperature Mg-surface doping of the cleaned InP before Ni-film deposition is demonstrated to decrease the contact resistivity of Ni/p-InP by the factor of 10 approximately as compared to the lowest reference value without Mg. Deposition of the Mg intermediate layer on p-InP and postheating of Mg/p-InP at 350 °C, both performed in ultrahigh-vacuum (UHV) chamber, lead to intermixing of Mg and InP elements according to X-ray photoelectron spectroscopy. Introducing a small oxygen gas background (O2 ≈ 10−6 mbar) in UHV chamber during the postheating of Mg/p-InP enhances the indium outdiffusion and provides the lowest contact resistivity. Quantum mechanical simulations indicate that the presence of InP native oxide or/and metal indium alloy at the interface increases In diffusion. 相似文献
8.
Abdenour Hadid Author Vitae Matti Pietikäinen Author Vitae 《Pattern recognition》2009,42(11):2818-2827
While many works consider moving faces only as collections of frames and apply still image-based methods, recent developments indicate that excellent results can be obtained using texture-based spatiotemporal representations for describing and analyzing faces in videos. Inspired by the psychophysical findings which state that facial movements can provide valuable information to face analysis, and also by our recent success in using LBP (local binary patterns) for combining appearance and motion for dynamic texture analysis, this paper investigates the combination of facial appearance (the shape of the face) and motion (the way a person is talking and moving his/her facial features) for face analysis in videos. We propose and study an approach for spatiotemporal face and gender recognition from videos using an extended set of volume LBP features and a boosting scheme. We experiment with several publicly available video face databases and consider different benchmark methods for comparison. Our extensive experimental analysis clearly assesses the promising performance of the LBP-based spatiotemporal representations for describing and analyzing faces in videos. 相似文献
9.
Mikko Kurimo Seppo Enarvi Ottokar Tilk Matti Varjokallio André Mansikkaniemi Tanel Alumäe 《Language Resources and Evaluation》2017,51(4):961-987
One particular problem in large vocabulary continuous speech recognition for low-resourced languages is finding relevant training data for the statistical language models. Large amount of data is required, because models should estimate the probability for all possible word sequences. For Finnish, Estonian and the other fenno-ugric languages a special problem with the data is the huge amount of different word forms that are common in normal speech. The same problem exists also in other language technology applications such as machine translation, information retrieval, and in some extent also in other morphologically rich languages. In this paper we present methods and evaluations in four recent language modeling topics: selecting conversational data from the Internet, adapting models for foreign words, multi-domain and adapted neural network language modeling, and decoding with subword units. Our evaluations show that the same methods work in more than one language and that they scale down to smaller data resources. 相似文献
10.
Water Resource Models in the Mekong Basin: A Review 总被引:6,自引:1,他引:5
Development of the water resources of the Mekong Basin is the subject of intense debate both within the Mekong region and
internationally. Water resources modelling is playing an increasingly important role in the debate, with significant effort
in building integrated modelling platforms to describe the hydrological, ecological, social and economic impacts of water
resource development. In the hydrological domain, a comprehensive set of models has been effective in building understanding
of the system, and in identifying and describing the issues and trade-offs involved in basin-scale water planning. In the
ecological and social domains, quantitative modelling has not progressed very far; geo-spatial analysis and qualitative frameworks
remain the most commonly used tools. Economic models have been used to assess the costs and benefits of water resources development
and to describe the trade-offs between different sectors and users. These analyses are likely to play an important role in
the policy and planning debate, but are hampered by uncertainties in valuation of ecosystem services. Future efforts should
focus on optimising the use of existing model platforms for the Mekong, including structured comparison of multiple hydrological
models to quantify errors and identify an optimum set of modelling tools for different applications. A comprehensive research
effort is needed to incorporate groundwater into hydrological models for regional planning. Options for social impact assessment
should be reassessed before major investments are made in complex modelling platforms, and participatory social survey methods
evaluated as part of an integrated assessment framework. 相似文献