全文获取类型
收费全文 | 22515篇 |
免费 | 1912篇 |
国内免费 | 947篇 |
专业分类
电工技术 | 1267篇 |
技术理论 | 2篇 |
综合类 | 1449篇 |
化学工业 | 3754篇 |
金属工艺 | 1219篇 |
机械仪表 | 1444篇 |
建筑科学 | 2045篇 |
矿业工程 | 777篇 |
能源动力 | 601篇 |
轻工业 | 1301篇 |
水利工程 | 389篇 |
石油天然气 | 1598篇 |
武器工业 | 136篇 |
无线电 | 2330篇 |
一般工业技术 | 2720篇 |
冶金工业 | 1117篇 |
原子能技术 | 244篇 |
自动化技术 | 2981篇 |
出版年
2024年 | 81篇 |
2023年 | 420篇 |
2022年 | 585篇 |
2021年 | 904篇 |
2020年 | 752篇 |
2019年 | 637篇 |
2018年 | 683篇 |
2017年 | 771篇 |
2016年 | 651篇 |
2015年 | 858篇 |
2014年 | 1171篇 |
2013年 | 1284篇 |
2012年 | 1478篇 |
2011年 | 1537篇 |
2010年 | 1375篇 |
2009年 | 1252篇 |
2008年 | 1216篇 |
2007年 | 1206篇 |
2006年 | 1265篇 |
2005年 | 1164篇 |
2004年 | 694篇 |
2003年 | 607篇 |
2002年 | 552篇 |
2001年 | 525篇 |
2000年 | 477篇 |
1999年 | 632篇 |
1998年 | 490篇 |
1997年 | 420篇 |
1996年 | 373篇 |
1995年 | 336篇 |
1994年 | 258篇 |
1993年 | 146篇 |
1992年 | 136篇 |
1991年 | 118篇 |
1990年 | 87篇 |
1989年 | 70篇 |
1988年 | 53篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 11篇 |
1984年 | 10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 |
1969年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
实施独立计量分区(district metered area,DMA)是辅助供水管网管理和漏损识别的重要手段.图划分算法是进行DMA分区的方法之一,常规图划分算法应用中,存在解空间受限、分区后原水流状态易发生较大改变、形成较多串联分区(对流量计算不利)的缺点.在常规图划分算法基础上进行了改进:粗化阶段按照特定规则匹配、合并非输水干管两端的节点,形成简化的管网拓扑结构;分区阶段得到管网初步分区方案;细化阶段提出基于贪心算法、枚举算法、蒙特卡洛算法的分区调整方法,结合改进的仪表安置方法、水力模拟、优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS),对分区方案进行调整.将该方法应用于YX市供水管网,成功进行了分区. 相似文献
4.
5.
6.
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.
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