全文获取类型
收费全文 | 40054篇 |
免费 | 4875篇 |
国内免费 | 3169篇 |
专业分类
电工技术 | 3617篇 |
综合类 | 4076篇 |
化学工业 | 5010篇 |
金属工艺 | 2412篇 |
机械仪表 | 2837篇 |
建筑科学 | 3295篇 |
矿业工程 | 1269篇 |
能源动力 | 1410篇 |
轻工业 | 3922篇 |
水利工程 | 1178篇 |
石油天然气 | 1318篇 |
武器工业 | 607篇 |
无线电 | 4518篇 |
一般工业技术 | 3767篇 |
冶金工业 | 1430篇 |
原子能技术 | 642篇 |
自动化技术 | 6790篇 |
出版年
2024年 | 201篇 |
2023年 | 502篇 |
2022年 | 1263篇 |
2021年 | 1707篇 |
2020年 | 1203篇 |
2019年 | 960篇 |
2018年 | 982篇 |
2017年 | 1178篇 |
2016年 | 1084篇 |
2015年 | 1646篇 |
2014年 | 2058篇 |
2013年 | 2465篇 |
2012年 | 2974篇 |
2011年 | 3053篇 |
2010年 | 3019篇 |
2009年 | 3007篇 |
2008年 | 3189篇 |
2007年 | 3094篇 |
2006年 | 2864篇 |
2005年 | 2355篇 |
2004年 | 1844篇 |
2003年 | 1609篇 |
2002年 | 1910篇 |
2001年 | 1506篇 |
2000年 | 1003篇 |
1999年 | 479篇 |
1998年 | 172篇 |
1997年 | 171篇 |
1996年 | 116篇 |
1995年 | 86篇 |
1994年 | 72篇 |
1993年 | 60篇 |
1992年 | 46篇 |
1991年 | 49篇 |
1990年 | 27篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1959年 | 7篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
油液监测是判断设备健康状况和提供设备故障隐患预警的有效方法。综述了用于监测润滑油中磨损颗粒的最新各类在线传感器的基本原理,包括批量磁吸附式传感器、微流体电容传感器、金属扫描传感器、双层平面线圈传感器、超声波传感器和光学传感器等,并讨论各种传感方法的优缺点以及未来发展面临的挑战;指出了高通量、高灵敏度、能区别金属与非金属磨粒、可采集磨粒图像信息的集成式传感器是未来研究的重点,集成式、智能化、无线传输的传感器是未来研发方向。 相似文献
2.
3.
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
5.
三唑并嘧啶磺酰胺类除草剂——五氟磺草胺 总被引:1,自引:0,他引:1
综述了新型三唑并嘧啶磺酰胺类除草剂五氟磺草胺的理化性质、毒性、分析方法、加工及应用,详细介绍了其合成工艺路线、相关专利与开发进展。 相似文献
7.
进入更广泛的历史语境探讨清乾隆时期镜清斋假山的营造思路,追溯至晚明江南的两种假山营造来源.在整体构思上,承续了17世纪前期张南垣所创的追求画意真山的"天然"假山;而在局部营造中,则采纳了16世纪后期盛行的追求胜景无穷的"人巧"假山.除镜清斋之外,在稍晚的苏州环秀山庄假山中也有显著表达,是清代假山发展高峰的体现.清末和1970年代对该假山的两次改造,未能很好理解原初的思路取向,一定程度上损害了当初追求的山意. 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.