全文获取类型
收费全文 | 1163篇 |
免费 | 107篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 420篇 |
金属工艺 | 26篇 |
机械仪表 | 34篇 |
建筑科学 | 33篇 |
能源动力 | 73篇 |
轻工业 | 188篇 |
水利工程 | 26篇 |
石油天然气 | 12篇 |
无线电 | 87篇 |
一般工业技术 | 165篇 |
冶金工业 | 21篇 |
原子能技术 | 5篇 |
自动化技术 | 176篇 |
出版年
2024年 | 5篇 |
2023年 | 24篇 |
2022年 | 57篇 |
2021年 | 117篇 |
2020年 | 107篇 |
2019年 | 90篇 |
2018年 | 117篇 |
2017年 | 112篇 |
2016年 | 91篇 |
2015年 | 46篇 |
2014年 | 95篇 |
2013年 | 113篇 |
2012年 | 82篇 |
2011年 | 64篇 |
2010年 | 49篇 |
2009年 | 30篇 |
2008年 | 23篇 |
2007年 | 14篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有1274条查询结果,搜索用时 46 毫秒
41.
In this article, the nondestructive eddy current (EC) method was used for microstructural evaluation of Ni-hard4 cast iron (NiHCI). Different destabilizing heat treatments were used to produce different microstructures and hardness. The microstructural analysis and hardness measurement were done for conventional characterization of the reference blocks. Then, the EC techniques were applied to evaluate the hardness and microstructural changes by the detection of EC parameters at different frequencies. Metallurgical investigations showed that increasing the destabilizing soaking time and temperature decreases the amount of retained austenite in NiHCIs. The nondestructive evaluation method (NDT) revealed that it can be good correlated between retained austenite amount and hardness with EC parameters. This shows that the EC technique can detect NiHCIs products according to the metallurgical characterization with good accuracy. 相似文献
42.
43.
Investigating the effect of paper properties on color reproduction of digital printing 总被引:1,自引:0,他引:1
Digital printing is affected by several parameters including printer and paper type which determine the final printed color gamut and the quality of reproduction. For investigation of those effects, tests were done on the three types of laser printer and six types of paper with different properties of whiteness, roughness, and gloss. The gamut volume was generated by Eye-One spectrophotometer, ProfileMaker, and ColorThink software. Properties of the different types of paper were measured by the atomic force microscopy, spectrophotometer and, goniophotometer. Results showed that the reproducibility was considerably dependent on the type of printer and type of paper. High whiteness and gloss increased the color gamut volume, while high roughness decreased the reproducibility of the printer. Tests on paper properties showed that whiteness had the most significant effect on color gamut volume. 相似文献
44.
Mohammad Reza Foroughi Saeed Karbasi Maryam Khoroushi Abbas Ali Khademi 《Journal of Porous Materials》2017,24(6):1447-1460
Scaffolds and their features play a central role in tissue engineering; so this study is based on the production of a series of electrospun PHB/Chitosan/nBG nanocomposite scaffolds with 9 wt% polyhydroxybutyrate, 10, 15 and 20 wt% chitosan and 7.5, 10 and 15 wt% nanobioglass (nBG). Electrospinning process was performed with optimal conditions of spinning machine including voltage of 16 kV, syringe-collector spacing of 16 cm, and output rate of 1 µl per hour. The developed phases and the formation of chemical bonds between ceramic and polymer bands were studied through XRD and FTIR analyses. The FE-SEM and TEM analyses showed uniform morphology of nanofibers and dispersion of bioglass nanoparticles in the fiber structure. The presence of 10 wt% bioglass nanoparticles and 15 wt% chitosan increased the tensile strength of fibers to 3.42 MPa, which was about four times greater than strength of control sample (pure PHB). The developed fibers were kept 28 days in SBF solution and 60 days in PBS solution to assess their bioactivity and biodegradability. The results showed that the presence of bioglass nanoparticles leads to a dramatic increase in absorption of calcium and phosphorus ions and weight loss of scaffold. The developed scaffold can be used for bone and teeth tissue engineering applications. 相似文献
45.
An efficient synthesis of 5-arylidene-2,4-thiazolidinediones and 5-benzylidene rhodanines by the Knoevenagel condensation of 2,4-thiazolidinedione or rhodanine with aromatic aldehydes was studied. It proceeded smoothly in the presence of tetrabutylammonium hydroxide/H 2O-EtOH to afford the corresponding products in high yields at 50°C. Also, a series of dihydrothiophene derivatives were synthesized via the four-component reaction of aldehyde, malonitrile, 2,4-thiazolidinedione, and piperidine in the presence of Bu4NOH as a basic ionic liquid in aqueous medium. This new method offers several advantages, such as excellent yields, short reaction times, and simple procedure. 相似文献
46.
Computational Visual Media - Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from... 相似文献
47.
48.
Vahid Ghasemzadeh-mohammadi Bahman Zamani Maryam Afsharpour Abdorreza Mohammadi 《Food science and biotechnology》2017,26(5):1281-1290
In this research, optimal conditions for extraction of caffeine and polyphenols were established from Iranian green tea leaves. In the first step, caffeine was extracted with efficacy about 86% versed to 4.5% of EGC + EGCG. The EGCG + EGC was extracted from partially decaffeinated green tea leaves through microwave-assisted extraction (MAE) and ultrasound-assisted extraction (USE) with efficiency levels of 95 and 85%, respectively. The best results for the MAE process were obtained with 7.8 min and three number of extraction cycles and for the USE process were as followed: time 57 min, temperature 65 °C, and the number of extraction cycles 3. The total phenol content values at the best conditions of MAE and the USE processes were 125 ± 5 and 96 ± 6 mg gallic acid/g DW. The 50% inhibition (IC50) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) were 56 and 66 mg/g of phenol for the MAE and USE processes. 相似文献
49.
Maryam Fattahi Hassan Abedini Mohammad Amin Anbaz 《Petroleum Science and Technology》2017,35(11):1117-1123
Favorable properties of aqueous solutions are improved with the addition of different materials for separation of hydrogen sulfide (H2S). Also, equilibrium data and available equations for solubility estimation of this gas are only valid for specific solutions and limited ranges of temperature and pressure. In this regard, a machine learning model based on Support vector machine (SVM) algorithm is proposed and developed with mixtures containing different amines and ionic liquids to predict H2S solubility over wide ranges of temperature (298–434.5 K), pressure (13–9319 kPa), overall mass concentration (3.82–100%) and mixture's apparent molecular weight (18.39–556.17 g/mol). The accuracy of the performance of this network was evaluated by regression analysis on calculated and experimental data, which had not been used in network training. 相似文献
50.
Maryam Masjedi-Arani Masoud Salavati-Niasari 《International Journal of Hydrogen Energy》2017,42(2):858-866
Zn2SnO4 nanostructures were obtained via facile and rapid co-precipitation approach in presence of amines with different long chain as a novel basic and capping agents. The effect of different amines such as NH3, ethylenediamine, triethylenetetramine, tetraethylenepentamine on the size of Zn2SnO4 nanostructures were investigated. The results demonstrated that applying the appropriate amount of organic amine could be effective in particle size control. The obtained nanostructure products were specified by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and ultraviolet–visible (UV–vis) spectroscopy. Dye sensitized solar cells (DSSC) were created by the constructed electrodes as working electrode and then were studied by current density–voltage (J–V) curve. It was found that incorporating of TiO2 nanoparticles to optimized Zn2SnO4 nanostructures has significant role on the constructed DSSCs photovoltaic properties. 相似文献