全文获取类型
收费全文 | 49498篇 |
免费 | 5545篇 |
国内免费 | 2666篇 |
专业分类
电工技术 | 4139篇 |
技术理论 | 3篇 |
综合类 | 3593篇 |
化学工业 | 7506篇 |
金属工艺 | 2803篇 |
机械仪表 | 3406篇 |
建筑科学 | 4326篇 |
矿业工程 | 1855篇 |
能源动力 | 1409篇 |
轻工业 | 3089篇 |
水利工程 | 1052篇 |
石油天然气 | 2573篇 |
武器工业 | 523篇 |
无线电 | 5750篇 |
一般工业技术 | 5637篇 |
冶金工业 | 2092篇 |
原子能技术 | 606篇 |
自动化技术 | 7347篇 |
出版年
2024年 | 320篇 |
2023年 | 1032篇 |
2022年 | 1940篇 |
2021年 | 2787篇 |
2020年 | 2052篇 |
2019年 | 1582篇 |
2018年 | 1779篇 |
2017年 | 1862篇 |
2016年 | 1734篇 |
2015年 | 2459篇 |
2014年 | 2928篇 |
2013年 | 3380篇 |
2012年 | 3720篇 |
2011年 | 3777篇 |
2010年 | 3316篇 |
2009年 | 3057篇 |
2008年 | 2858篇 |
2007年 | 2725篇 |
2006年 | 2542篇 |
2005年 | 2176篇 |
2004年 | 1406篇 |
2003年 | 1168篇 |
2002年 | 1093篇 |
2001年 | 937篇 |
2000年 | 817篇 |
1999年 | 845篇 |
1998年 | 642篇 |
1997年 | 537篇 |
1996年 | 477篇 |
1995年 | 424篇 |
1994年 | 299篇 |
1993年 | 193篇 |
1992年 | 179篇 |
1991年 | 140篇 |
1990年 | 108篇 |
1989年 | 109篇 |
1988年 | 69篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1959年 | 8篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
目的:解决当前饮料瓶盖检测系统功能单一、体积偏大、颜色识别率低的问题。方法:提出一种基于ARM处理器的小型饮料瓶盖颜色识别系统设计方案,通过仿真软件HyperLynx的LineSim工具设计四层PCB板,设置传输线参数并进行阻抗匹配仿真分析;利用编译软件Jupyter Notebook实现阈值设置、目标轮廓检测、目标框出等功能。结果:在强、弱光条件下,识别系统对红、绿、蓝3种颜色瓶盖的识别率达到92.7%。结论:与傅里叶描述子相比,该识别系统识别准确率和精度更高,同时系统也具有人脸识别功能,适用于各种智能应用场景。 相似文献
3.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
4.
Tomohiro Toigawa Yasuhiro Tsubata Takeshi Kai Takuya Furuta Yuta Kumagai Tatsuro Matsumura 《溶剂提取与离子交换》2021,39(1):74-89
ABSTRACT Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process. 相似文献
5.
6.
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
7.
Wenlong Song Shoujun Wang Yang Lu Xuan Zhang Zixiang Xia Kai Sun Guangming Xin 《Ceramics International》2021,47(9):12631-12640
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed. 相似文献
8.
9.
Polymer Bulletin - Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic... 相似文献
10.