全文获取类型
收费全文 | 34335篇 |
免费 | 3223篇 |
国内免费 | 1772篇 |
专业分类
电工技术 | 2072篇 |
技术理论 | 2篇 |
综合类 | 2567篇 |
化学工业 | 5375篇 |
金属工艺 | 2010篇 |
机械仪表 | 2193篇 |
建筑科学 | 2950篇 |
矿业工程 | 1143篇 |
能源动力 | 990篇 |
轻工业 | 2029篇 |
水利工程 | 608篇 |
石油天然气 | 2112篇 |
武器工业 | 318篇 |
无线电 | 3893篇 |
一般工业技术 | 3861篇 |
冶金工业 | 1594篇 |
原子能技术 | 337篇 |
自动化技术 | 5276篇 |
出版年
2024年 | 156篇 |
2023年 | 592篇 |
2022年 | 948篇 |
2021年 | 1320篇 |
2020年 | 1068篇 |
2019年 | 960篇 |
2018年 | 1009篇 |
2017年 | 1132篇 |
2016年 | 989篇 |
2015年 | 1344篇 |
2014年 | 1723篇 |
2013年 | 1948篇 |
2012年 | 2189篇 |
2011年 | 2283篇 |
2010年 | 2167篇 |
2009年 | 1962篇 |
2008年 | 1988篇 |
2007年 | 1913篇 |
2006年 | 1919篇 |
2005年 | 1710篇 |
2004年 | 1257篇 |
2003年 | 1325篇 |
2002年 | 1523篇 |
2001年 | 1268篇 |
2000年 | 820篇 |
1999年 | 821篇 |
1998年 | 554篇 |
1997年 | 500篇 |
1996年 | 434篇 |
1995年 | 372篇 |
1994年 | 284篇 |
1993年 | 182篇 |
1992年 | 151篇 |
1991年 | 142篇 |
1990年 | 103篇 |
1989年 | 74篇 |
1988年 | 59篇 |
1987年 | 33篇 |
1986年 | 36篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
2.
Hua Zhu Hai Zhang Tian-hao Zhang Shi-jin Yu Ping-chun Guo Yan-xiang Wang Zhi-sheng Yang 《Ceramics International》2021,47(12):16980-16985
Indium Tin Oxide (ITO) films were prepared, at room temperature, on a fluorphlogopite substrate using magnetron sputtering technology. At various temperatures of 500 °C, 600 °C, 700 °C, 800 °C, and 900 °C, the samples were (had) annealed for 2 h (a 2-h duration). The results showed improvement in the crystalline performance of ITO film at selected annealing temperatures, with a significant reduction in resistivity at 800 °C. The lowest resistivity is 4.08 × 10?4 Ω-cm, which is nearly an order of magnitude lower than the unannealed sample. All samples have an average light transmittance above 85% in the visible light range (400–800 nm), and with increasing annealing temperature, the average light transmittance tends to decrease. Besides, at the sensitive wavelength of 550 nm, the light transmittance is as high as 93.74%. The sheet resistance testing of the sample was through the number of bending times, which revealed that with the increase of the number of bending, the sheet resistance increases. However, after 1200 bending times, the change rate of the sheet resistance remains below 5%. Thus, the ITO film prepared on the flexible fluorphlogopite substrate revealed excellent optical and electrical properties, good flexibility, and improved stability after high-temperature annealing, which guarantees successful application in flexible electronic devices. 相似文献
3.
Yujie Chen Yiping Song Zhen Zhang Yali Chen Qiliang Deng Shuo Wang 《Advanced functional materials》2021,31(41):2104885
Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k−20°C < k4°C < k20°C < k35°C < k55°C. The activation energy (Ea) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL−1. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs. 相似文献
4.
5.
7.
Huizhu Cai Bingbing Chen Xiao Zhang Yuchen Deng Dequan Xiao Ding Ma Chuan Shi 《Nano Research》2021,14(1):122-130
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeⅡN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeⅡN4 species as highly active sites for the ORR. 相似文献
8.
9.
Xiaopu Lyu Yunxi Huo Jin Yang Dawen Yao Kaimin Li Haoxian Lu Yangzong Zeren Hai Guo 《Indoor air》2021,31(5):1340-1352
Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C28-C34 even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality. 相似文献
10.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献