全文获取类型
收费全文 | 888篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 183篇 |
金属工艺 | 9篇 |
机械仪表 | 18篇 |
建筑科学 | 59篇 |
矿业工程 | 14篇 |
能源动力 | 33篇 |
轻工业 | 84篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 49篇 |
一般工业技术 | 62篇 |
冶金工业 | 264篇 |
原子能技术 | 8篇 |
自动化技术 | 92篇 |
出版年
2022年 | 12篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 23篇 |
2013年 | 57篇 |
2012年 | 26篇 |
2011年 | 28篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 31篇 |
2007年 | 26篇 |
2006年 | 22篇 |
2005年 | 29篇 |
2004年 | 14篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 24篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 12篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1982年 | 9篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1973年 | 8篇 |
1964年 | 7篇 |
1957年 | 9篇 |
1956年 | 7篇 |
排序方式: 共有904条查询结果,搜索用时 15 毫秒
21.
Kumar Siddharth Yian Wang Jing Wang Fei Xiao Gabriel Sikukuu Nambafu Usman Bin Shahid Fei Yang Ernest Pahuyo Delmo Minhua Shao 《Frontiers of Chemical Science and Engineering》2022,16(6):930
Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells, hydrogen production and understanding nitrogen cycle. Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media. In this study, Pt/nitrogen-doped graphene (NDG) and Pt/tungsten monocarbide (WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C. Pt/NDG exhibits a specific activity of 0.472 mA∙cm–2, which is 44% higher than commercial Pt/C, thus establishing NDG as a more effective support than carbon black. Moreover, it is demonstrated that WC as a support also impacts the activity with further 30% increase in comparison to NDG. Surface modification with Ir resulted in the best electrocatalytic activity with Pt-Ir/WC/NDG having almost thrice the current density of commercial Pt/C. This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification. 相似文献
22.
Composites comprising Poly(Methyl Methacrylate) (PMMA) and CaCu3Ti4O12 (CCTO) via melt mixing followed by hot pressing were fabricated. These were characterized using X‐ray diffraction, thermo gravimetric, scanning electron microscopy, and Impedance analyzer for their structural, morphology, and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. Theoretical models were employed to rationalize the dielectric behavior of these composites. At higher temperatures, the relaxation peak shifts to higher frequencies, due to the merging of both β and α relaxations into a single dielectric dispersion peak. The AC conductivity in the high frequency region was attributed to the electronic polarization. POLYM. ENG. SCI., 54:551–558, 2014. © 2013 Society of Plastics Engineers 相似文献
23.
The feasibility of using a potassium ferioxalate actinometer as a photochemical pyranometer was studied. The preparation, exposure, and spectrophotometric analysis of the pyranometer cell are described. By calibrating it against a Yellot Mark IV solameter, linear correlations were obtained with respect to total insolation and time of exposure. The spectral response, the quantum yields at different wavelengths, the mechanism of photochemical reaction, and the conversion factor for converting the absorption reading into cal/cm2/min are discussed. The advantages of the new pyranometer are its low cost, simplicity of operation and calibration, high sensitivity, and high tolerance to field conditions. It is useful for mapping solar intensity distribution over a wide area. 相似文献
24.
25.
Matsagopane Gaamangwe Olakanmi Eyitayo Olatunde Botes Annelize Kutua Said 《JOM Journal of the Minerals, Metals and Materials Society》2019,71(5):1840-1857
JOM - Documentation on the correct process and component requirements for setting up efficient aluminum powder production systems capable of manufacturing powder that meets the requirements for the... 相似文献
26.
Spray drying is a very useful method for manufacturing of amorphous solid materials. This is mainly due to the possibility of fast solvent evaporation that leads to a rapid transformation of solution to a solid state. Besides evaporation kinetics, there are various process parameters that influence physical and chemical characteristics of such obtained material. The possibility of obtaining a stable amorphous structure of the active pharmaceutical ingredient in a spray dryer was examined. A solution of the hydrochloride crystalline structure of the active pharmaceutical ingredient in a mixture of water and acetonitrile was dried at different temperatures and flowrates of nitrogen used for atomization, as well as the flowrates of the solution. The influence of the process conditions on the properties of the product was analyzed. The final dried products were characterized and identified with a variety of analytical and physical methods. The results showed that a stable amorphous structure of the high purity active pharmaceutical ingredient is obtained, and that the optimal conditions of the process are defined. The amorphous structure is stable at temperatures below 200°C when it is transformed into a new crystal structure. Conditions of high relative air humidity lead to partial transformation. 相似文献
27.
Monitoring of monosaccharides,oligosaccharides, ethanol and glycerol during wort fermentation by biosensors,HPLC and spectrophotometry 总被引:1,自引:0,他引:1
The aim of the present study was to analyze sugar levels (namely maltose, maltotriose, glucose and fructose) and alcohols (ethanol and glycerol) during the fermentation process in wort samples by amperometric enzymatic biosensors developed by our research group for industrial application, HPLC and spectrophotometry, and to compare the suitability of the presented methods for determination of individual analytes. We can conclude that for the specific monitoring of maltose or maltotriose only the HPLC method was suitable. On the other hand, biosensors and spectrophotometry reflected a decrease in total sugar concentration better and were able to detect both glucose and fructose in the later stages of fermentation, while HPLC was not. This can be attributed to the low detection limits and good sensitivity of the proposed methods. For the ethanol and glycerol analysis all methods proved to be suitable. However, concerning the cost expenses and time analysis, biosensors represented the best option. 相似文献
28.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献
29.
30.
Cover Picture: Tetrahydroisoquinolinone‐Based Steroidomimetic and Chimeric Microtubule Disruptors (ChemMedChem 1/2014) 下载免费PDF全文