全文获取类型
收费全文 | 111965篇 |
免费 | 13003篇 |
国内免费 | 9166篇 |
专业分类
电工技术 | 9655篇 |
技术理论 | 5篇 |
综合类 | 11873篇 |
化学工业 | 14273篇 |
金属工艺 | 8043篇 |
机械仪表 | 7652篇 |
建筑科学 | 7989篇 |
矿业工程 | 4147篇 |
能源动力 | 2823篇 |
轻工业 | 12067篇 |
水利工程 | 3872篇 |
石油天然气 | 4035篇 |
武器工业 | 1545篇 |
无线电 | 12655篇 |
一般工业技术 | 9902篇 |
冶金工业 | 4632篇 |
原子能技术 | 1785篇 |
自动化技术 | 17181篇 |
出版年
2024年 | 533篇 |
2023年 | 1785篇 |
2022年 | 4204篇 |
2021年 | 5435篇 |
2020年 | 3799篇 |
2019年 | 2921篇 |
2018年 | 3153篇 |
2017年 | 3353篇 |
2016年 | 3040篇 |
2015年 | 4765篇 |
2014年 | 5969篇 |
2013年 | 7120篇 |
2012年 | 8779篇 |
2011年 | 9270篇 |
2010年 | 8786篇 |
2009年 | 8391篇 |
2008年 | 8399篇 |
2007年 | 8444篇 |
2006年 | 7451篇 |
2005年 | 6062篇 |
2004年 | 4680篇 |
2003年 | 3636篇 |
2002年 | 3923篇 |
2001年 | 3383篇 |
2000年 | 2433篇 |
1999年 | 1270篇 |
1998年 | 577篇 |
1997年 | 486篇 |
1996年 | 406篇 |
1995年 | 320篇 |
1994年 | 273篇 |
1993年 | 234篇 |
1992年 | 150篇 |
1991年 | 134篇 |
1990年 | 120篇 |
1989年 | 98篇 |
1988年 | 61篇 |
1987年 | 46篇 |
1986年 | 39篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 7篇 |
1981年 | 18篇 |
1980年 | 33篇 |
1979年 | 15篇 |
1977年 | 12篇 |
1976年 | 24篇 |
1959年 | 16篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
32.
33.
Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride) 下载免费PDF全文
Mengjiao Zhang Weihong Wu Shaorui He Xue Wang Yunhong Jiao Hongqiang Qu Jianzhong Xu 《Polymer International》2018,67(4):445-452
The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO3) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO3 and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO3. In addition, the incorporation of AC and MoO3 greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO3 was 10 phr, PVC/AC/MoO3 had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m?2 and 0.1472 m2 s?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO3, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO3 produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry 相似文献
34.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger 下载免费PDF全文
35.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
36.
Hong Wei Li Li Ya‐Li Ma Ru‐Xue Liu Shuang‐Yan Meng Li‐Tong Niu Zhe Zhang Zhi‐Wang Yang 《火与材料》2019,43(7):868-879
Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism. 相似文献
37.
38.
39.
Multimedia Tools and Applications - Understanding human emotions through facial expressions is key enabling technology for interactive robots. Most approaches of facial expression recognition are... 相似文献
40.
以新型褶式滤筒为研究对象,选取滤筒褶数N_2、褶夹角θ、褶高h、过滤风速v为影响因子,除尘器压力损失为响应值,基于响应曲面法分析影响因子对压力损失的影响,建立滤筒除尘器压力损失的预测模型并得到滤筒褶皱结构最优参数。以滤筒内径D、筒体高度D_1为标准尺寸,依据相关国家标准设计滤筒筒体部分;以锥体高度D_2、锥体上圆直径D_3为系列尺寸,利用尺寸变化法设计锥体部分;通过Access软件建立滤筒产品数据库。结果表明:当θ=5.2°,N_2=50,v=0.01 m/s,h=0.035 m时,除尘器压力损失最低;当D_1=1 000 mm,D=320 mm时,D_2和D_3最佳值分别为600,130 mm,故采用D_2/D_1=0.6,D_3/D=0.4的比值设计相应滤筒锥体系列。 相似文献