全文获取类型
收费全文 | 1033篇 |
免费 | 61篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 28篇 |
综合类 | 1篇 |
化学工业 | 379篇 |
金属工艺 | 26篇 |
机械仪表 | 19篇 |
建筑科学 | 22篇 |
矿业工程 | 2篇 |
能源动力 | 50篇 |
轻工业 | 81篇 |
水利工程 | 9篇 |
石油天然气 | 24篇 |
无线电 | 114篇 |
一般工业技术 | 190篇 |
冶金工业 | 45篇 |
原子能技术 | 5篇 |
自动化技术 | 104篇 |
出版年
2023年 | 19篇 |
2022年 | 38篇 |
2021年 | 49篇 |
2020年 | 33篇 |
2019年 | 47篇 |
2018年 | 74篇 |
2017年 | 50篇 |
2016年 | 42篇 |
2015年 | 38篇 |
2014年 | 41篇 |
2013年 | 82篇 |
2012年 | 58篇 |
2011年 | 59篇 |
2010年 | 48篇 |
2009年 | 34篇 |
2008年 | 30篇 |
2007年 | 17篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 25篇 |
2003年 | 25篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有1099条查询结果,搜索用时 10 毫秒
131.
Ahmed M. Nassef Enas Taha Sayed Cristina Rodriguez A.G. Olabi 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2019,41(17):2094-2103
Biodiesel is one of the promising energy sources that could replace petroleum oil in the near future. Microalgae is occupying a distinguished position among the promising sources for biodiesel production. Enhancement of the lipids production during the pretreatment is a key factor for the biodiesel production. High-pressure homogenizer is a better pretreatment procedure to enhance the lipid extraction from microalgae. In this research, a robust model of biodiesel system using fuzzy logic is built based on the experimental data for biodiesel system. Then, Particle Swarm Optimization (PSO) optimizer is applied for determining the best operating parameters of biodiesel system. The decision variables used in the optimization process are; pressure, number of passes, and reaction time that maximizes the percentage of recovery lipids of biodiesel. A comparison study was carried out between the optimized results thought PSO algorithm and those obtained by the experimental results and the optimized results through the Response Surface Methodology (RMS). Results demonstrated that using the proposed optimization methodology is significantly better than RSM, a nearly 78.7% increase in lipids extraction could be achieved according to the current model. 相似文献
132.
Magdy El-Hagary Said H. Moustafa Hany Hashem Essam R. Shaaban Mohamed Emam-Ismail 《Journal of the American Ceramic Society》2019,102(8):4737-4747
Mn-doped HgO nanostructured thin films (Hg1-xMnxO) have been prepared using electron beam evaporation technique on Corning glass (1022) substrate at room temperature with different concentrations x = 0, 0.015, 0.05, 0.1, 0.15, and 0.2. The microstructural, morphological, semiconducting, and optoelectronic properties of the films have been investigated. The X-ray diffraction spectra suggest a hexagonal wurtzite type structure with lattice parameters decreased with increasing Mn content. It was found that the average particle size of the films decreases with increasing Mn doping which is confirmed by FE-SEM and AFM micrographs. The optical band gap of the investigated Mn-doped HgO nanocrystalline films is determined from the absorption coefficient and found to increase with the increase of Mn concentration which is attributed to the sp-d exchange interaction and/or the quantum confinement effect. The refractive index and extinction coefficient of the Mn-doped HgO films are also reported. The refractive index dispersion n(λ) is analyzed by single-effective-oscillator dispersion model proposed by the Wemple–DiDomenico (WDD). The oscillator parameters were estimated. The obtained dispersion values are suitable for the design of optoelectronic devices. 相似文献
133.
Mona Y. Elnaggar El Sayed Fathy Enas Amdeha Medhat M. Hassan 《Polymer Engineering and Science》2019,59(4):807-813
This investigation focused on the opportunity of devulcanizing waste Rubber (WR) by ultrasonication to study the possibility of utilized as an added substance to replace with styrene‐butadiene rubber (SBR) in preparation process with the final aim of preparation new composites. The present work expects to compare the ultrasonic technique and the previous work on devulcanization by mechano‐chemical method. The influence of the ultrasonication treatment on the WR was explored by Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy analysis revealed that ultrasonication was observed to be the best factor impacting the devulcanization procedure, this procedure suggests that use of specific levels of ultrasonic waves to the vulcanized rubber with a specific aim to accomplish a particular breaking of compound connections: scission of C‐S and S‐S bonds without break carbon–carbon (C‐C) bonds. Various blends of devulcanized WR with SBR was treatments with gamma ray then investigated and compared with find out the rubber giving the highest compatibility for compounding and revulcanization. In addition, a comparison of these results was made with the ones of raw SBR rubber compound. POLYM. ENG. SCI., 59:807–813, 2019. © 2019 Society of Plastics Engineers 相似文献
134.
Moustafa Saad Abdelkrim SadoudiEric Rondet Bernard Cuq 《Journal of food engineering》2011,102(4):293-301
A quantitative method was developed to evaluate the shape of wheat powder particles. The method relies on a dispersion system designed to scatter particles on a transparent glass slide. A digital image acquisition system based on specialized software was then used to analyze the acquired images. Particles (1000) were analyzed with respect to four shape factors (circularity, elongation, convexity, and compactness). Dispersion of experimental values characterizes the large heterogeneity in wheat flour particles’ shapes. The results demonstrate that small particles of wheat powders have more regular shape than big ones, due to possible erosion mechanisms occurred during milling. 相似文献
135.
Salah Abdulrhmann Minoru Yamada Moustafa Ahmed 《International Journal of Numerical Modelling》2011,24(3):218-229
Influence of the linewidth‐enhancement factor on the output and operations of InGaAs/InP pumping lasers emitting at a wavelength of 980 nm under strong optical feedback is investigated numerically. The investigations are performed based on intensive numerical integration of an improved time‐delay rate equations of semiconductor lasers over wide ranges of the linewidth‐enhancement factor and optical feedback strength. The results show that the semiconductor laser operates under strong optical feedback in continuous wave and pulsation at small values of the linewidth‐enhancement factor. Under large values of the linewidth‐enhancement factor, the laser happens to exhibit chaos and pulsation. We predict that semiconductor laser subjected to strong optical feedback exhibits much more stable pulsing operation under higher values of the linewidth‐enhancement factor, which indicates that the laser is locked at the external cavity frequency. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
136.
137.
Ravishankar Sathyamurthy Abd Elnaby Kabeel El‐Sayed El‐Agouz DSilva Rufus Hitesh Panchal Thirugnanasambantham Arunkumar Athikesavan Muthu Manokar David Gnanaraj Prince Winston 《国际能源研究杂志》2019,43(8):3295-3305
This work aims at augmenting the amount of potable water using MgO and TiO2 in stepped solar still. Experiments were carried out for the climatic conditions of Chennai, India, with two different concentrations of nanofluids inside a stepped basin under three different cases. Results show that there is an improvement in yield of fresh water from stepped solar still by 33.18% and 41.05% using 0.1% and 0.2% volume concentration of TiO2 nanofluid, respectively, whereas the freshwater yield from stepped still with MgO nanofluids improved by 51.7% and 61.89%. Furthermore, the economic analysis revealed that the cost of potable water from the modified solar still reduced from 0.029 to 0.016 $/kg. Similarly, the useful annual energy, yearly cost per kilogram, and annual cost per kilowatt hour are significantly profitable with the use of MgO nanofluid in the stepped basin and found as 512.46 kWh, 0.025 $/kg, and 0.026 $/kWh, respectively. It is also found that the cost of potable water from the modified still significantly increases as the amount of fresh water produced is decreased with increased fabrication cost of the solar still. 相似文献
138.
Abdelmoty M. Ahmed Reda Abo Alez Gamal Tharwat Muhammad Taha B. Belgacem Ahmad M. J. Al Moustafa 《成像科学杂志》2020,68(1):11-23
ABSTRACTArabic sign language (ArSL) is method of communication between deaf communities in Arab countries; therefore, the development of systemsthat can recognize the gestures provides a means for the Deaf to easily integrate into society. In this research we implemented a computational structurefor an intelligent interpreter that automatically recognizes the isolated dynamic gestures. The proposed system recognizes and translates gesturesperformed with one or both hands. It comprises five subsystems, building dataset, video processing, feature extraction, mapping between ArSL and Arabictext, and text generation. To apply the system, 100-signs of ArSL was used, which was applied on 1500 video files. It's were divided into five classes:alphabet, numbers, "prepositions, pronouns and question words", Arabic life expressions, and "nouns and verbs". The evaluation indicated that thesystem automatically recognizes and translates isolated dynamic ArSL gestures by highly accurate manner. The results showed that the system accuracy is 95.8%. 相似文献
139.
140.
Efficient 3D point clouds classification for face detection using linear programming and data mining
Most of the applications related to security and biometric rely on skin region detection such as face detection, adult 3D objects filtering, and gesture recognition. In this paper, we propose a robust method for skin detection on 3D coloured point clouds. Then, we extend this method to solve the problem of 3D face detection. To do so, we construct a weighted graph from initial coloured 3D point clouds. Then, we present a linear programming algorithm using a predictive model based on a data mining approach to classify and label graph vertices as skin and non-skin regions. Moreover, we apply some refinement rules on skin regions to confirm the presence of a face. Furthermore, we demonstrate the robustness of our method by showing and analysing some experimental results. Finally, we show that our method deals with many data that can be represented by a weighted graph such as 2D images and 3D models. 相似文献