全文获取类型
收费全文 | 127435篇 |
免费 | 10939篇 |
国内免费 | 5098篇 |
专业分类
电工技术 | 6748篇 |
技术理论 | 6篇 |
综合类 | 6823篇 |
化学工业 | 22162篇 |
金属工艺 | 6705篇 |
机械仪表 | 8273篇 |
建筑科学 | 8098篇 |
矿业工程 | 2594篇 |
能源动力 | 3919篇 |
轻工业 | 9046篇 |
水利工程 | 1963篇 |
石油天然气 | 5095篇 |
武器工业 | 817篇 |
无线电 | 17457篇 |
一般工业技术 | 18342篇 |
冶金工业 | 6963篇 |
原子能技术 | 1542篇 |
自动化技术 | 16919篇 |
出版年
2024年 | 497篇 |
2023年 | 1931篇 |
2022年 | 3493篇 |
2021年 | 5043篇 |
2020年 | 3654篇 |
2019年 | 3425篇 |
2018年 | 3742篇 |
2017年 | 3880篇 |
2016年 | 4002篇 |
2015年 | 4918篇 |
2014年 | 6138篇 |
2013年 | 7923篇 |
2012年 | 8021篇 |
2011年 | 9129篇 |
2010年 | 7592篇 |
2009年 | 7378篇 |
2008年 | 7360篇 |
2007年 | 6582篇 |
2006年 | 6547篇 |
2005年 | 5547篇 |
2004年 | 4236篇 |
2003年 | 3894篇 |
2002年 | 4166篇 |
2001年 | 3489篇 |
2000年 | 2984篇 |
1999年 | 2849篇 |
1998年 | 2832篇 |
1997年 | 2215篇 |
1996年 | 1899篇 |
1995年 | 1578篇 |
1994年 | 1307篇 |
1993年 | 997篇 |
1992年 | 729篇 |
1991年 | 642篇 |
1990年 | 510篇 |
1989年 | 469篇 |
1988年 | 329篇 |
1987年 | 283篇 |
1986年 | 219篇 |
1985年 | 181篇 |
1984年 | 138篇 |
1983年 | 106篇 |
1982年 | 80篇 |
1981年 | 96篇 |
1980年 | 79篇 |
1979年 | 47篇 |
1978年 | 48篇 |
1977年 | 43篇 |
1976年 | 76篇 |
1975年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Peer-to-Peer Networking and Applications - P2P-TV is a TV system that receives content through a peer-to-peer network. Content is stored in the distributed manner then to be serviced to users, and... 相似文献
62.
Wai-Ching Liu Huey-Yuan Wang Lung-Chien Chen Shih-Wei Huang Chengtie Wu Ren-Jei Chung 《Ceramics International》2019,45(5):5668-5679
Tricalcium silicate (C3S) and hydroxyapatite (HAp) composites were fabricated through the sol-gel process. The aim of this research is to improve the biocompatibility of C3S through HAp addition and study the potential of using this as coating materials. The composites (HAp/C3S) were characterised by Fourier transform infrared spectrometry, thermal gravity-differential thermal analysis and X-ray diffraction. The working and setting times of cement pastes were tested using Gillmore needle. Mechanical properties were examined by nanoindentation and material testing system. In vitro biocompatibility of the materials were studied by cell attachment and viability of L929 and MG-63 cells. HAp/C3S as a coating material on gelatin film were measured with the surface roughness and imaged by scanning electron microscope. With the addition of HAp, no undesirable free CaO was detected with the synthesis by the sol-gel preparation. The pH values of HAp added groups were between 7.54 and 8.76, which were much lower than pure C3S group (pH?=?11.75). For in vitro studies, the presence of HAp could effectively enhance the cell attachment and viability of both L929 and MG-63 cells grown in the extract or directly on the composites. However, the mechanical properties of the composites were impaired as compared to pure C3S. Lastly, HAp/C3S cement could be evenly coated on gelatin film. HAp is successfully demonstrated to improve C3S biocompatibility with this new composites HAp/C3S. C-75 (75% C3S and 25% HAp), in particular, has good biocompatibility, relatively high compressive strength and can be uniformly coated onto gelatin film. Thus, C-75 is a promising material for further investigation as a coating on other biopolymers. 相似文献
63.
64.
65.
66.
本文提出了一种基于分散加载技术实现Boot程序和用户应用程序在同一个工程编写开发的固件更新方法 .通过编写分散加载规范文件在工程中实现代码存储区分区.为了保证固件更新的稳定性和可靠性,在固件下载过程中引入CRC校验、丢包错包重传等容错技术.实验结果 验证了方法的有效性和可靠性. 相似文献
67.
68.
69.
70.
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