全文获取类型
收费全文 | 761篇 |
免费 | 52篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 191篇 |
金属工艺 | 16篇 |
机械仪表 | 33篇 |
建筑科学 | 17篇 |
能源动力 | 64篇 |
轻工业 | 69篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 73篇 |
一般工业技术 | 176篇 |
冶金工业 | 58篇 |
原子能技术 | 4篇 |
自动化技术 | 100篇 |
出版年
2024年 | 6篇 |
2023年 | 16篇 |
2022年 | 40篇 |
2021年 | 47篇 |
2020年 | 44篇 |
2019年 | 45篇 |
2018年 | 53篇 |
2017年 | 35篇 |
2016年 | 39篇 |
2015年 | 25篇 |
2014年 | 31篇 |
2013年 | 62篇 |
2012年 | 39篇 |
2011年 | 42篇 |
2010年 | 37篇 |
2009年 | 50篇 |
2008年 | 43篇 |
2007年 | 20篇 |
2006年 | 16篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 10篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1981年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有817条查询结果,搜索用时 15 毫秒
1.
Waheed Iqbal Mariam Batool Arslan Hameed Saghir Abbas Muhammad Arif Nadeem 《International Journal of Hydrogen Energy》2021,46(49):25050-25059
Transition metal oxyhydroxides have been used as promising electrocatalysts for water splitting however, their catalytic activity is restricted due to low surface area and poor conductivity. Herein, we report novel composite FeOOH@ZIF-12/graphene composite as electrocatalyst for water oxidation, whereby ZIF-12 provide extra surface for the FeOOH dispersion whilst graphene act as excellent electron mediator. The composite shows a low overpotential value of 291 mV to attain a current density of 10 mA cm?2 and a low Tafel slope value of 78 mV dec?1. The catalyst offers a maximum current density of 101 mA cm?2, while it gives a turnover frequency (TOF) value of 0.031 s?1 at an overpotential of 291 mV only. The excellent activity and remarkable stability of composite is attributed to highly conductive and porous support. 相似文献
2.
Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations 总被引:2,自引:0,他引:2
F. Necati Catbas Mustafa Gul Jason L. Burkett 《Mechanical Systems and Signal Processing》2008,22(7):1650-1669
The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented. 相似文献
3.
The phenomena of natural convection caused by a concentration gradient usually creates currents as a result of buoyancy forces. These forces are formed from the combined effect of a fluid density gradient and the body force (gravitational force). The above phenomenon was studied experimentally in a circular glass column of 0.08 m diameter and 1 m length. This column was erected vertically and filled with distilled water with a salt bag placed on top of it and partially immersed in water. The dissolution mechanism was then modelled and a finite difference method was used to solve the formulated equations by using the implicit scheme of MacCormack (Anderson et al., 1984). The experimental results and the numerical predictions are represented graphically and give compatible agreement. 相似文献
4.
Deactivation of copper-ion-exchanged hydrogen-mordenite-type zeolite catalyst by SO2 for NO reduction by NH3 was examined in a fixed-bed flow reactor. The deactivation of the catalyst was strongly dependent on reaction temperature. At high reaction temperatures over 300°C, the catalyst did not lose its initial activity up to 50 h of operation, regardless of SO2 feed concentration from 500 to 20,000 ppm. However, at low reaction temperatures near 250°C, apparent deactivation did occur. Changes in the physicochemical properties such as surface area and sulfur content of deactivated catalyst well correlated with catalyst activity, depending upon reaction temperatures. The deactivation was due to pore blocking and/or filling by deactivating agents, which plugged and/or filled the pores of catalyst. The deactivating agents deposited on the catalyst surface were presumed to be (NH4)2SO4 and/or (NH4)HSO4 from the results of TGA and ion-chromatography measurement. 相似文献
5.
6.
A study of radiation effects on various types of glasses, dielectric optical coatings, cemented optics and fiber was undertaken with a view to select them for extreme radiation environments. Samples were exposed to different radiation doses in the Pakistan Research Reactor-I (PARR-I) for neutron and Cobalt 60 source for gamma irradiation. Transmissions were measured before and after irradiation. The dielectric coatings were subjected to additional tests (adhesion, abrasion and humidity, etc.) as per MIL-M-13508C and MIL-C-675C. All 15 glasses studied showed varying amounts of transmission loss as expected, with negligible degradation for three types. Recovery of transmissions with time/ageing was also studied, with more or less complete recovery with temperature annealing. A faster bleaching of darkened/brown glasses was achieved by using UV lamps or UV laser. The dielectric coatings (HR, AR) and one of the two commercial optical cements showed excellent resistance to neutrons and gamma radiations, and could be good candidates for the fabrication and utilization of optical components in extreme radiation environments. The data allowed several Chinese glasses to be studied for the first time. 相似文献
7.
Seena K. Thomas P. M. Sabura Begum C. D. Midhun Dominic Nisa V. Salim Nishar Hameed Sanjay Mavinkere Rangappa Suchart Siengchin Jyotishkumar Parameswaranpillai 《应用聚合物科学杂志》2021,138(15):50213
Acacia caesia (L.) Willd (soap bark) fiber is an abundant natural resource, that is rich in cellulose. The study reports the effective utilization of underutilized Acacia caesia fiber for the isolation of nanocellulose whiskers. The nanocellulose whiskers were isolated successfully from Acacia caesia fibers by following alkali, bleaching, and sulfuric acid treatment. The obtained nanocellulose whiskers were carefully investigated for its chemical composition, structure, morphology, crystallinity, and thermal stability. The chemical composition and Fourier transform infrared spectra of nanocellulose whiskers showed the elimination of the non-cellulosic parts present in the raw Acacia caesia fibers. The X-ray diffraction analysis showed an upsurge in the crystallinity of the cellulose fibers after the chemical treatments. The isolation of nanocellulose whiskers from Acacia caesia raw fiber was confirmed by electron microscopy analysis. The thermogravimetric analysis showed remarkably high char residue for the nanocellulose whiskers compared to raw fibers. Based on the properties of nanocellulose whiskers, it can be concluded that the nanocellulose whiskers produced from Acacia caesia raw fibers are potential reinforcing material for developing high-performance green composites. 相似文献
8.
Nouman Ali Shah Yue Ren Ri-Tong Lan Jia-Cheng Lv Rizwan M. Gul Peng-Fei Tan Shishu Huang Lin Tan Jia-Zhuang Xu Zhong-Ming Li 《应用聚合物科学杂志》2021,138(43):51261
Highly crosslinked ultrahigh molecular weight polyethylene (UHMWPE) stabilized by vitamin E (VE) is widely applied in artificial joints as the bearings. Despite the approval, there is a discord that VE lowers the crosslinking efficiency, limiting its use at high concentration. In this work, we aim to obtain highly crosslinked and oxidation resistant UHMWPE through the conjunction of tea polyphenol and chemical crosslinking. We hypothesized that highly incorporated tea polyphenol with multiple reactive sites can ameliorate crosslinking efficiency of chemical crosslinked UHMWPE in comparison to VE. Epigallocatechin gallate (EGCG) as representative tea polyphenol was incorporated into UHMWPE at high concentration (2–8 wt%), followed by chemical crosslinking with 2 wt% organic peroxide. Unlike VE/UHMWPE blends as the control, chemical crosslinking achieved an increasing trend in crosslink density of EGCG/UHMWPE blends with increasing antioxidant concentration. High concentration of EGCG also enhanced the oxidation stability of UHMWPE. Intriguingly, EGCG endowed UHMWPE with an excellent antimicrobial property, which was inefficient in VE/UHMWPE. Cell viability was hardly affected by the high loaded antioxidant and peroxide. The chemically crosslinked UHMWPE blended with EGCG is proved to be a reasonable, cost effective and realistic alternative for use in artificial joints. 相似文献
9.
During the recent years, there has been a tremendous growth in the development and deployment of multimedia based networked applications such as video streaming, IP telephony, interactive games, among others. These applications, in contrast to elastic applications such as email and data sharing, are delay and delay jitter sensitive but can tolerate certain level of packet loss. A vital element of end-to-end delay and delay jitter is the random queueing delays in network switches and routers. Analysis of robust mechanisms for buffer management at network routers needs to be carried out in order to reduce end-to-end delay for traffic generated by multimedia applications. In this context, a threshold based buffer management scheme for accommodating multiple class multimedia traffic in network routers has been analysed. This technique effectively controls the allocation of buffer to various traffic classes according to their delay constraints. The forms of the joint state probabilities, as well as basic performance measures such as blocking probabilities are analytically established at equilibrium. Typical numerical experiments are included to illustrate the credibility of the proposed mechanism in the context of different quality of service (QoS) grades for various network traffic classes. This model, therefore, can be used as a powerful tool to provide a required grade of service to a particular class of multimedia based web traffic in any heterogeneous network. 相似文献
10.
D.R.W. Holton I. Nafea M. Younas I. Awan 《Journal of Network and Computer Applications》2009,32(2):455-460
This paper is an investigation into the performance of E-commerce applications. E-commerce has become one of the most popular applications of the web as a large population of web users is now benefiting from various on-line services including product searches, product purchases and product comparison. E-commerce provides users with 24-7 shopping facilities. However, the consequence of these benefits and facilities is the excessive load on E-commerce web servers and the performance degradation of E-commerce (eCom) requests they process. This paper addresses this issue and proposes a class-based priority scheme which classifies eCom requests into high and low priority requests. In E-commerce, some requests (e.g. payment) are generally considered more important than others (e.g. search or browse). We believe that by assigning class-based priorities at multiple service levels, E-commerce web servers can perform better and can improve the performance of high priority eCom requests. In this paper, we formally specify and implement the proposed scheme and evaluate its performance using multiple servers. Experimental results demonstrate that the proposed scheme significantly improves the performance of high priority eCom requests. 相似文献