全文获取类型
收费全文 | 595篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 126篇 |
金属工艺 | 21篇 |
机械仪表 | 26篇 |
建筑科学 | 17篇 |
矿业工程 | 2篇 |
能源动力 | 103篇 |
轻工业 | 61篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 45篇 |
一般工业技术 | 97篇 |
冶金工业 | 25篇 |
原子能技术 | 12篇 |
自动化技术 | 73篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 20篇 |
2021年 | 31篇 |
2020年 | 31篇 |
2019年 | 22篇 |
2018年 | 43篇 |
2017年 | 23篇 |
2016年 | 36篇 |
2015年 | 19篇 |
2014年 | 29篇 |
2013年 | 52篇 |
2012年 | 40篇 |
2011年 | 46篇 |
2010年 | 31篇 |
2009年 | 40篇 |
2008年 | 27篇 |
2007年 | 35篇 |
2006年 | 16篇 |
2005年 | 6篇 |
2004年 | 10篇 |
2003年 | 15篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有629条查询结果,搜索用时 15 毫秒
61.
Support vector machines (SVM), a soft programming technique, has been used to estimate the temperature distribution and flow fields in a square porous enclosure heated discretely by three isothermal heaters from the left vertical wall. Right vertical wall of the cavity was isothermal but it has colder temperature than the heaters while remaining walls were adiabatic. A database was prepared by solving the governing equations which were written using Darcy flow model. Using finite difference method to discretize the equation, a computational fluid dynamics (CFD) code was written. A correlation was developed between Nusselt and Rayleigh numbers. Using obtained database, further values of temperature and velocities were estimated by SVM technique at different Rayleigh numbers and locations of heater. It was observed that SVM was a useful technique on estimation of streamlines and isotherms. Thus, SVM reduces the computational time and helps to solve some cases when CFD fails to solve due to numerical instability. 相似文献
62.
An ecological performance analysis for an irreversible dual-cycle cogeneration system has been performed. The objective function is called as the exergetic-performance coefficient (EPC) and defined as the ratio of total exergy output to the loss rate of availability. The general and optimal performances of the irreversible dual-cycle cogeneration system, having a finite-rate of heat transfer, heat leak and internal irreversibilities based on the EPC objective function have been investigated. Comparisons with respect to the optimal total-exergy output are also provided in order to establish the utility of the new exergetic-performance coefficient. The analyzed results of the dual-cycle cogeneration system considered, working at maximum EPC conditions, have a significant advantage in terms of entropy-generation rate and can be used for the selection of optimal design parameters. 相似文献
63.
Saricimen Huseyin Kahraman Ramazan Malaibari Zuhair Abdur Rauf Md. 《Protection of Metals and Physical Chemistry of Surfaces》2018,54(5):926-933
Protection of Metals and Physical Chemistry of Surfaces - The objective of this study was to characterize the surfaces of the steel products produced locally during their exposure to the industrial... 相似文献
64.
A numerical analysis of the entropy production has been performed due to natural convection heat transfer and fluid flow in isosceles triangular enclosures with partially heated from below and symmetrically cooled from sloping walls. Governing equations are solved by finite difference method. Governing parameters on flow and temperature fields are Rayleigh number (103 Ra 8.8 × 105), dimensionless length of heater (0.25 (ℓ′ = ℓ/L) 1.0), dimensionless location of heater (0.25 (c′ = c/L) 0.75) and inclination angle of slopping walls (30° β 60°). Heat transfer results are presented in terms of local and mean Nusselt numbers (Nu) while entropy production results are shown with entropy production number (Ns) and Bejan number (Be). Isotherms, streamlines, contours of entropy production due to heat transfer and fluid friction irreversibility are plotted. It is observed that entropy production number increases but Bejan number decreases with increasing of Rayleigh number. However, both entropy production due to heat transfer and fluid friction irreversibility are affected by higher inclination angle of triangle and length of heater. 相似文献
65.
M. Erdem Günay Fatma AkpinarZ. Ilsen Onsan Ramazan Yildirim 《International Journal of Hydrogen Energy》2012
The water gas shift activity of promoted Pt–CeO2/Al2O3 catalysts were investigated in this work. The catalysts were prepared by incipient to wetness impregnation and tested using a microflow reaction system. It was found that K has beneficial effects under product-containing feed compositions while Co and Ni promoters worsen catalyst performance. The reaction temperature and feed H2O/CO ratio positively affect the catalytic activity, whereas CO2 and H2 addition to the feed decreases CO conversion, as expected. The experimental results were also modeled using modular neural networks, at which the catalyst preparation and operational (reaction) variables were used together in the same network because they are interacting but processed differently because they are dissimilar in their form (i.e. categorical versus continuous) and their effects on catalytic activity. It was concluded that the effects of catalyst preparation and operational variables and their relative importance could be comprehended more accurately by using this approach, which may be also employed in other similar systems. 相似文献
66.
Diker Aykut Sönmez Yasin Özyurt Fatih Avcı Engin Avcı Derya 《Multimedia Tools and Applications》2021,80(16):24777-24800
Multimedia Tools and Applications - The accurate separation of ECG signals has become crucial to identify heart diseases. Machine learning methods are widely used to separate ECG signals. The aim... 相似文献
67.
Mahsa Varmazyari Yasin Khani Farzad Bahadoran Zahra Shariatinia Saeed Soltanali 《International Journal of Hydrogen Energy》2021,46(1):565-580
Cu(BDC) metal–organic framework (MOF) was used as a support for the copper (Cu) catalyst applied in the methanol steam reforming (MSR) process at low temperatures (130–250 °C) with a feed WHSV = 9.2 h?1 within the monolithic reactor. Also, the effects of diverse promoters were examined on the catalytic activities of the Cu/X–Cu(BDC) (X = Ce, Zn, Gd, Sm, La, Y, Pr) catalysts. Results showed that the Ce/Sm–Cu(BDC) supports exhibited highest activities, lowest reduction temperatures and largest specific surface areas, which caused highest distributions of the active copper metal nanoparticles on the supports. The reactor tests displayed that the activities of Cu/X–Cu(BDC) (X = Ce, Zn, Gd, Sm, La, Y, Pr) catalysts followed the order X = Ce > Sm > Y > La > Pr > Cu(BDC) > Zn > Gd. The highest activities of Ce and Sm containing catalysts were attributed to the presence of CeO2 and Sm2O3 caused the oxygen vacancies on the catalyst surface which had positive effects on the methanol reforming process. The time-on-stream stability tests showed the highest resistance of the Cu/Ce–Cu(BDC) catalyst to the carbon formation during 32 h. Consequently, the Cu/Ce–Cu(BDC) with the highest stability, methanol conversion and carbon monoxide selectivity could be used in practical industrial applications. 相似文献
68.
Irshad Ahmad Shazia Shukrullah Muhammad Yasin Naz Muhammad Athar Rasheed Mukhtar Ahmad Ejaz Ahmed Muhammad Shoaib Akhtar N.R. Khalid Abid Hussain Sadia Khalid 《International Journal of Hydrogen Energy》2021,46(53):26711-26724
CNTs were decorated onto Sr doped ZnO nanoparticles to construct an efficient photocatalyst via a facile sol-gel method. The as-fabricated Sr doped ZnO/CNTs with recyclability exhibits Sr and CNTs content dependent hydrogen evolution activit under visible light illumination. The Sr doped ZnO/CNTs photocatalyst shows the highest hydrogen evolution rate of 2732.2 μmolh?1g?1, which is 33.7 and 2.83 times higher than pure ZnO and Sr doped ZnO photocatalysts, respectively. The improved hydrogen evolution activity of Sr doped ZnO/CNTs is primarily assigned to high surface area, Sr doping and construction of heterojunction, which can extend the light absorption, decrease the optical band gap and improve the charge separation. Moreover, the underlying photocatalytic mechanism is proposed on the basis of Mott-Schottky study and explains the interfacial charge transfer process from ZnO to CNTs and Sr. This work open new strategies to synthesize CNTs based nanocomposite for hydrogen evolution. 相似文献
69.
Khurram A. Khan Ramazan Kahraman Esam Z. Hamad Shaikh A. Ali Syed H. Hamid 《应用聚合物科学杂志》1997,64(4):645-652
A liquid crystalline polymer (LCP) was synthesized by an interfacial polycondensation reaction at room temperature from terephthaloyl chloride and p,p′-dihydroxydiphenyl sulfone. The LCP synthesized was so stable and molecularly rigid that it did not show any phase transition until it degraded at about 320°C. Composites of the LCP with polycarbonate (PC), polystyrene (PS), and sulfonated polystyrene (SPS) were formed by compression molding at a temperature at which the thermoplastic matrix was in the melt state. They were thermally analyzed by differential scanning calorimetry. Tensile specimens were cut from the compression-molded plates, and mechanical tests were performed. The morphology of the material systems was studied by performing scanning electron microscopy analysis on cryogenically fractured specimens. For LCP/PS and LCP/SPS systems, a sharp two-phase morphology was formed, which suggested poor interfacial adhesion. The tensile strength of both systems decreased with LCP addition. The LCP/PC system also revealed a two-phase morphology; however, the interfaces between the LCP domains and the PC matrix were not so well defined, showing better interfacial adhesion than the two previous systems studied. Stronger bonding between the LCP and PC resulted in a significant improvement in the mechanical behavior of PC by LCP addition. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 645–652, 1997 相似文献
70.
Tekin Ramazan Ertuğrul Ömer Faruk Kaya Yılmaz 《Multimedia Tools and Applications》2020,79(43-44):32541-32561
Multimedia Tools and Applications - In this paper, four novel, simple and robust approaches, which are left to right local binary patterns (LBPLL2R), top to down local binary patterns (LBPT2D),... 相似文献