全文获取类型
收费全文 | 21589篇 |
免费 | 1891篇 |
国内免费 | 925篇 |
专业分类
电工技术 | 1216篇 |
技术理论 | 2篇 |
综合类 | 1390篇 |
化学工业 | 3640篇 |
金属工艺 | 1171篇 |
机械仪表 | 1394篇 |
建筑科学 | 1967篇 |
矿业工程 | 756篇 |
能源动力 | 591篇 |
轻工业 | 1251篇 |
水利工程 | 358篇 |
石油天然气 | 1515篇 |
武器工业 | 122篇 |
无线电 | 2254篇 |
一般工业技术 | 2613篇 |
冶金工业 | 1046篇 |
原子能技术 | 238篇 |
自动化技术 | 2881篇 |
出版年
2024年 | 99篇 |
2023年 | 442篇 |
2022年 | 689篇 |
2021年 | 978篇 |
2020年 | 778篇 |
2019年 | 636篇 |
2018年 | 673篇 |
2017年 | 757篇 |
2016年 | 632篇 |
2015年 | 828篇 |
2014年 | 1119篇 |
2013年 | 1224篇 |
2012年 | 1408篇 |
2011年 | 1440篇 |
2010年 | 1298篇 |
2009年 | 1163篇 |
2008年 | 1147篇 |
2007年 | 1111篇 |
2006年 | 1175篇 |
2005年 | 1102篇 |
2004年 | 654篇 |
2003年 | 569篇 |
2002年 | 509篇 |
2001年 | 479篇 |
2000年 | 446篇 |
1999年 | 587篇 |
1998年 | 462篇 |
1997年 | 392篇 |
1996年 | 357篇 |
1995年 | 313篇 |
1994年 | 239篇 |
1993年 | 140篇 |
1992年 | 129篇 |
1991年 | 113篇 |
1990年 | 87篇 |
1989年 | 69篇 |
1988年 | 54篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
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
3.
Li Qian Chen Yan Sun Shikun Zhu Muyuan Xue Jing Gao Zihan Zhao Jinfeng Tang Yihe 《Water Resources Management》2022,36(12):4799-4817
Water Resources Management - Increasing water consumption in agriculture due to global climate change has posed considerable challenges to food security, thus improving the efficiency of water... 相似文献
4.
5.
6.
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
7.
8.
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
9.
10.
江河湖海疏浚工程对于拓展和保障航运安全、促进生态恢复、维护/改善远海岛礁环境具有不可或缺的作用.目前,在绞吸和耙吸疏浚船上,多采用射线密度计及电磁流量计对输泥密度、产量等进行在线计量,并作为实现疏浚系统自动控制的重要参量.由于射线密度计潜在的人员健康、公共安全和环保风险,在一些国家和地区已建立了放射源的有序退出机制.电阻层析成像使用安装于管壁的电极阵列获得管道内流体的电导率分布,进而推导出管道内的泥浆密度,具有无辐射、全场测量及实时可视化的优点.电阻层析成像测量系统经过特殊设计,可适应从内陆淡水到海水的巨大电导率变化.初步测试表明,电阻层析成像测量数据与射线密度计具有良好一致性,具备了作为在线泥浆密度测量的可行性.此外,ERT可提供实时的流动成像,对于提高对疏浚管道监测能力和降低堵管概率具有重要意义. 相似文献