全文获取类型
收费全文 | 502篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 164篇 |
金属工艺 | 10篇 |
机械仪表 | 8篇 |
建筑科学 | 8篇 |
能源动力 | 29篇 |
轻工业 | 107篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 40篇 |
一般工业技术 | 94篇 |
冶金工业 | 16篇 |
原子能技术 | 2篇 |
自动化技术 | 46篇 |
出版年
2024年 | 9篇 |
2023年 | 19篇 |
2022年 | 39篇 |
2021年 | 63篇 |
2020年 | 37篇 |
2019年 | 45篇 |
2018年 | 23篇 |
2017年 | 31篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 33篇 |
2012年 | 33篇 |
2011年 | 33篇 |
2010年 | 13篇 |
2009年 | 18篇 |
2008年 | 12篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 31 毫秒
41.
Kentaro Kukita Indra Nur Adisusilo Yoshinari Kamakura 《Journal of Computational Electronics》2014,13(1):264-270
Heat conduction properties in Si nanostructures are analyzed using a Monte Carlo method developed for solving the phonon Boltzmann transport equation. The thermal resistances are evaluated for the systems with various sizes, and the transition from the diffusive to the ballistic heat conduction are investigated. We compare the two different phonon dispersion models (the realistic dispersion relation based on the adiabatic bond charge model and the analytically approximated model), and it is shown that the correct implementation of the phonon dispersion relation is essential to accurately simulate the quasi-ballistic heat conduction properties, which becomes obvious in the structures smaller than the phonon mean free path. 相似文献
42.
Hidayah Rahmalan Nur Azman Abu Siaw Lang Wong 《Pattern Recognition and Image Analysis》2010,20(4):505-512
Orthogonal moment is known as better moment functions compared to the non-orthogonal moment. Among all the orthogonal moments,
Tchebichef Moment appear to be the most recent moment functions that still attract the interest among the computer vision
researchers. This paper proposes a novel approach based on discrete orthogonal Tchebichef Moment for an efficient image compression.
The image compression is useful in many applications especially related to images that are needed to be seen in small devices
such as in mobile phone. Meanwhile, the method incorporates simplified mathematical framework techniques using matrices, as
well as a block-wise reconstruction technique to eliminate possible occurrences of numerical instabilities at higher moment
orders. In addition, a comparison between Tchebichef Moment compression and JPEG compression is conducted. The result shows
significant advantages for Tchebichef Moment in terms of its image quality and compression rate. Tchebichef moment provides
a more compact support to the image via sub-block reconstruction for compression. Tchebichef Moment Compression is able to
perform potentially better for a broader domain on real digital images and graphically generated images. 相似文献
43.
The rehabilitation, repair, and strengthening of concrete structures has increased worldwide with a growing number of systems employing externally applied fiber-reinforced polymer (FRP) composites. However, the service life and effectiveness of FRP repair and strengthening techniques when applied to concrete in corrosive marine environments is still not well understood. This paper presents the results of an experimental study on the corrosion performance of embedded steel reinforcement in cylindrical reinforced concrete specimens with 13 different surface treatment options. Samples were subjected to an impressed current and a high salinity solution. Test variables included the type of epoxy, wrap fiber orientation, and the number of wrap layers. Samples were evaluated for corrosion activity by monitoring corrosion potentials and impressed current flow levels, and by examining reinforcement mass loss and concrete chloride content among samples. Test results indicated that FRP wrapped specimens had prolonged test life, decreased reinforcement mass loss, and reduced concrete chloride content. The performance of wrapped specimens was superior to that of either control samples or those coated only with epoxy. Epoxy type had a significant effect on the performance of samples regarding their resistance to corrosion. It was concluded that carbon FRP wraps were able to confine concrete, slowing deterioration from cracking and spalling and inhibiting the passage of salt water. 相似文献
44.
In this paper, we will present our recent research on the growth and characterization of some Si-based heterostructures for
optical and photonic devices. The heterostructures to be discussed are ZnO nanorods on Si, SiO2, and other substrates such as SiN and sapphire. We will also consider strained Si1−xGex/Si heterostructures for Si optoelectronics. The performance and functionality extension of Si technology for photonic applications
due to the development of such heterostructures will be presented. We will focus on the results of structural and optical
characterization in relation to device properties. The structural characterization includes x-ray diffraction for assessment
of the crystallinity and stress in the films and secondary ion mass spectrometry for chemical analysis. The optical properties
and electronic structure were investigated by using photoluminescence. The device application of these thin film structures
includes detectors, lasers, and light emitting devices. Some of the Si-based heterostructures to be presented include devices
emitting and detecting up to the blue-green and violet wave lengths. 相似文献
45.
This study aims to find a correlation between winter outdoor design temperature (WDT) and mass of the building envelope. The daily variations of the inside surface temperatures and heat fluxes of the walls under various climatic conditions and different wall constructions have been calculated by a computer program based on the response factor technique, which uses variable outside air temperature and solar radiation and constant inside air temperature values as input climatic data. The analysis of the relation between mass of the walls and inside surface heat fluxes resulted with the correction values for winter design temperature (WDTCV) depending on the mass of the wall and on the direction of facades for different climatic zones. 相似文献
46.
Maisara Othman Richard Ritikos Noor Hamizah Khanis Nur Maisarah Abdul RashidSaadah Abdul Rahman Siti Meriam Ab GaniMuhamad Rasat Muhamad 《Thin solid films》2011,519(15):4981-4986
Carbon nitride (CNx) thin films were deposited by radio frequency plasma enhanced chemical vapour deposition (rf PECVD) technique from a gas mixture of methane (CH4), hydrogen (H2) and nitrogen (N2). The effects of rf power on the structural properties of CNx thin films were discussed in this paper. It was found that rf power had significant effects on the growth rate, structural and morphological properties of the deposited films. The point of transition of the growth rate trend marked the equilibrium condition for primary and secondary reactions in growth kinetics of the film with respect to rf power. The films grown at this optimum rf power were most ordered in structure with high surface roughness and had the lowest N incorporation. This work showed that H etching effects and ion bombardment effects increase with increase in rf power and strongly influenced the structure of the CNx films. 相似文献
47.
Güzide alk Nur Pehlivan lknur enver
zelik Pnar alk Tuner H
zdamar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(11):1243-1250
Serine alkaline protease (SAP) production in a complex medium based on physically pretreated molasses by recombinant Bacillus subtilis carrying pHV1431::subC gene is described. The effects of oxygen transfer were investigated in 3.5 dm3 bioreactor systems with controls for agitation rate, dissolved oxygen, pH, temperature, and foam formation under two different agitation rates, ie N = 500 and 750 min?1, and four different air flow rates, ie Q/VR = 0.2, 0.5, 0.7, and 1.0 vvm, at a molasses concentration equivalent to initial sucrose concentration (CSo) of 20 kg m?3. The yield values (YX/S, YX/O, YS/O) and maintenance coefficient of oxygen (mO), were calculated. mO decreased with the increase in the air‐inlet rate. Increase in oxygen transfer rate increased the rate of growth and SAP activity, and affected the cultivation time to achieve maximum expression of SAP activity. At Q/VR = 0.5 vvm and N = 750 min?1, SAP activity reached 2250 U cm?3 at t = 36 h. The oxygen transfer coefficient (KLa) and oxygen uptake rate (?rO) were measured throughout the fermentations and their variation with the oxygen transfer conditions determined. New correlations for the calculation of KLa and ?rO are proposed. Copyright © 2004 Society of Chemical Industry 相似文献
48.
Effective properties of cemented granular materials 总被引:7,自引:0,他引:7
Jack Dvorkin Amos Nur Hezhu Yin 《Mechanics of materials : an international journal》1994,18(4):351-366
An analytical model is developed to describe the effective elastic properties of a cemented granular material that is modeled as a random packing of identical spheres. The elastic moduli of grains may differ from those of cement. The effective bulk and shear moduli of the packing are calculated from geometrical parameters (the average number of contacts per sphere and porosity), and from the normal and tangential stiffnesses of a two-grain combination. The latter are found by solving the problems of normal and tangential deformation of two elastic spherical grains cemented at their contact. A thin cement layer is approximated by an elastic foundation, and the grain-cement interaction problems are reduced to linear integral equations. The solution reveals a peculiar distribution pattern of normal and shear stresses at the cemented grain contacts: the stresses are maximum at the center of the contact region when the cement is soft relative to the grain, and are maximum at the periphery of the contact region when the cement is stiff. Stress distribution shape gradually varies between these two extremes as the cement's stiffness increases. The solution shows that it is mainly the amount of cement that influences the effective elastic properties of cemented granular materials. The radius of the cement layer affects the stiffness of a granular assembly much more strongly than the stiffness of the cement does. This theoretical model is supported by experimental results. 相似文献
49.
Simultaneous adsorption of a mixture of paraquat and dye by NaY zeolite covered with alkylsilane 总被引:1,自引:0,他引:1
The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites. 相似文献
50.
This paper describes a simple and rapid photocatalytic pretreatment procedure that removes contaminants from glassy carbon (GC) surfaces. The effectiveness of TiO2 mediated photocatalytic pretreatment procedure was compared to commonly used alumina polishing procedure. Cyclic voltammetric and chronocoulometric measurements were carried out to assess the changes in electrode reactivity by using four redox systems. Electrochemical measurements obtained on photocatalytically treated GC electrodes showed a more active surface relative to polished GC. In cyclic voltammograms of epinephrine, Fe(CN)63−/4− and ferrocene redox systems, higher oxidation and reduction currents were observed. The heterogeneous electron transfer rate constants (ko) were calculated for Fe(CN)63−/4− and ferrocene which were greater for photocatalytic pretreatment. Chronocoulometry was performed in order to find the amount of adsorbed methylene blue onto the electrode and was calculated as 0.34 pmol cm−2 for photocatalytically pretreated GC. The proposed photocatalytic GC electrode cleansing and activating pretreatment procedure was more effective than classical alumina polishing. 相似文献