全文获取类型
收费全文 | 302篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 107篇 |
金属工艺 | 10篇 |
机械仪表 | 8篇 |
建筑科学 | 4篇 |
能源动力 | 44篇 |
轻工业 | 18篇 |
水利工程 | 1篇 |
石油天然气 | 8篇 |
无线电 | 18篇 |
一般工业技术 | 64篇 |
冶金工业 | 9篇 |
自动化技术 | 26篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 27篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 20篇 |
2011年 | 24篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有321条查询结果,搜索用时 15 毫秒
21.
Wireless sensor networks (WSNs) applications are growing rapidly in various fields such as environmental monitoring, health care management, and industry control. However, WSN's are characterized by constrained resources especially; energy which shortens their lifespan. One of the most important factors that cause a rapid drain of energy is radio communication of multivariate data between nodes and base station. Besides, the dynamic changes of environmental variables pose a need for an adaptive solution that cope with these changes over the time. In this paper, a new adaptive and efficient dimension reduction model (APCADR) is proposed for hierarchical sensor networks based on the candid covariance-free incremental PCA (CCIPCA). The performance of the model is evaluated using three real sensor networks datasets collected at Intel Berkeley Research Lab (IBRL), Great St. Bernard (GSB) area, and Lausanne Urban Canopy Experiments (LUCE). Experimental results show 33.33% and 50% reduction of multivariate data in dynamic and static environments, respectively. Results also show that 97–99% of original data is successfully approximated at cluster heads in both environment types. A comparison with the multivariate linear regression model (MLR) and simple linear regression model (SLR) shows the advantage of the proposed model in terms of efficiency, approximation accuracy, and adaptability with dynamic environmental changes. 相似文献
22.
Leaching of blended slag (BS) was investigated in a microwave oven using hydrogen peroxide and acetic acid. The BS was a mixture of converter and flash furnace slag containing 51% Fe2O3, 3.8% CuO, and 3.2% ZnO. The important variables that influence the metal extraction yield were leaching time, liquid-solid ratio, H2O2 and CH3COOH concentrations. The preferred leaching conditions were as follows: CH3COOH concentration 4 mol/L; H2O2 concentration 4 mol/L; microwave power 900 W; leaching time 30 min; liquid-solid ratio 25 mL/g BS; leaching temperature 100 °C. Under these conditions, the metal extractions of 95% Cu, 1.6% Fe, and 30% Zn were obtained. The results were compared with the traditional leaching results. It is evident that microwave heating causes a reduction in the leaching time. Also, the extraction yield results indicate that selective leaching of BS can be achieved under the preferred conditions. The dissolution kinetic of BS in hydrogen peroxide with acetic acid is controlled by a shrinking unreacted core model equation. The apparent activation energy and reaction order were found to be 16.64 kJ/mol and 1.09, respectively. 相似文献
23.
Ilham Zainal Abidin Catalin Mandache Gui Yun Tian Maxim Morozov 《NDT & E International》2009,42(7):599-605
In pulsed eddy current testing, repetitive excitation signals with different duty cycles have different spectral representations. This work studies the influence of duty cycle on the ability to detect holes and EDM notches beneath rivet heads in subsurface layers of stratified samples. Feature patterns for the integrity of rivet joints are proposed and verified. The proposed method has the added advantage in that no reference sample is needed while employing multiple pulse measurements, with different pulse widths. Experimental testing and modelling approaches are discussed in connection with defect depth quantification, which can be extended to the quantification of complex defects. 相似文献
24.
In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications. 相似文献
25.
Subsolidus pyrochlores with the proposed formula, Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) were successfully synthesised at the firing temperature of 1025 °C using conventional solid-state reaction. The excess Bi3+ charge was offset by removal of relative proportion of Mg2+ and Nb5+ together with creation of oxygen non-stoichiometry in order to preserve electroneutrality of the system. These samples were crystallised in cubic structure with space group of Fd3m, No. 227 and their refined lattice parameters were in the range of 10.5706 (3)–10.5797 (7) Å. The surface morphologies of the samples as confirmed by scanning electron microscopy analysis were of irregular shaped grains while their crystallite sizes of ~30–85 nm were calculated using the Scherrer equation and the Williamson–Hall method. No thermal event was discernable indicating these pyrochlores were thermally stable within a studied temperature range of ~30–1000 °C. The recorded dielectric constants of Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) subsolidus pyrochlores were generally above ~160 and their dielectric losses were in the order of 10−4–10−3 at the frequency of 1 MHz and temperature of ~30 °C. Meanwhile, these ceramic samples also exhibited negative temperature coefficient of relative permittivity between −528 and −742 ppm/°C in the temperature range of ~30–300 °C. 相似文献
26.
The in vitro antifungal activity of chitosan against Fusarium oxysporum f. sp. cubense Race 4 (FocR4) the causal agent of banana wilt was investigated. Chitosan at all concentrations tested reduced the hyphal growth of FocR4 on potato dextrose agar media and recording maximum inhibition of 76.36% at 8 mg/mL. The inhibitory effect was found to increase as chitosan concentration increases. The 50% effective concentration value was estimated by probit analysis, and it was 1.4 mg/mL. Chitosan was more effective in potato dextrose broth where it completely inhibited the mycelial growth of FocR4 at all concentrations tested. Chitosan inhibited the sporulation of FocR4 by a maximum of 96.53% at 8 mg/mL chitosan, and 100% inhibition for spore germination was recorded at all concentrations tested. Chitosan at concentrations of more than 1.6 mg/mL was also found to induce morphological changes in FocR4 characterized by agglomeration of hyphae, abnormal shapes, vesicles, or empty cells devoid of cytoplasm in the mycelia. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
27.
Zurina Zainal Abidin Fatin Nordalila Omar Dayang Radiah Awang Biak Yaakob Che Man 《International Journal of Food Properties》2016,19(5):1127-1138
Dielectric property at high microwave frequency region has been utilized for possible rapid detection and screening of different types of meat, especially for halal authentication. This investigation focused on both raw and sterilized (processed) beef, pork, and chicken samples. Dielectric response that consists of dielectric constant and dielectric loss factor was measured over the range of 0.5 to 50 GHz. All raw and sterilized meat samples could be differentiated by the dielectric values. Two distinct peaks were observed only for both raw and sterilized pork samples at the frequency around 7.43 and 31.19 GHz. These peaks can potentially be linked to compounds that exist only in pork such as DNA, microbes, enzyme, proteins, amino acids, and many others. Dielectric values for sterilized samples were lower than raw samples due to molecule structural changes that occurred in the samples. The dielectric results promise a great potential of utilizing dielectric properties as a rapid on-site detection approach prior to subsequent laborious analysis. 相似文献
28.
CaCu3Ti4O12 electroceramic was prepared by a microwave assisted solid-state reaction technique from CaCO3, CuO and TiO2 powders. Processing involved the preparation of raw material, mixing and milling, calcination, pellet forming and sintering processes. Conventional furnace and microwave assisted sintering processes were employed in order to improve phase structures, morphology and dielectric properties of CaCu3Ti4O12 ceramics. Surface and fracture FESEM analysis showed that the microwave assisted sintered CaCu3Ti4O12 produced better densification and more uniform grain size compared to the conventional sintered sample. 相似文献
29.
30.
Mohd Zobir bin Hussein Asmah Hj Yahaya Zulkarnain Zainal Loo Hee Kian 《Science and Technology of Advanced Materials》2005,6(8):956-962
Controlled release formulation of an herbicide, 2,4-dichlorophenoxyacetate (24D) was developed by the virtue of the formation of organic–inorganic nanohybrid material and its ion exchange property. The inorganic Zn–Al layered double hydroxide (ZAL) was used as a matrix, hosting an active agent or a guest, 24D by self-assembly technique. The resulting material (ZAD) was subsequently used to study the release property of 24D into aqueous solutions containing chloride, carbonate as well as distilled water. The release of the guest 24D was found to be rapid initially followed by a more sustained release thereafter and this behavior was dependent on the type of anions and their concentrations in the release medium, the aqueous solution. The mechanism of release has been interpreted on the basis of the ion exchange process between the 24D anion intercalated into the interlamellae host and carbonate or chloride and/or hydroxyl anions in the aqueous solution. 相似文献