全文获取类型
收费全文 | 4060篇 |
免费 | 447篇 |
国内免费 | 123篇 |
专业分类
电工技术 | 59篇 |
综合类 | 251篇 |
化学工业 | 1323篇 |
金属工艺 | 209篇 |
机械仪表 | 73篇 |
建筑科学 | 176篇 |
矿业工程 | 130篇 |
能源动力 | 197篇 |
轻工业 | 1282篇 |
水利工程 | 41篇 |
石油天然气 | 121篇 |
武器工业 | 9篇 |
无线电 | 72篇 |
一般工业技术 | 190篇 |
冶金工业 | 371篇 |
原子能技术 | 18篇 |
自动化技术 | 108篇 |
出版年
2024年 | 7篇 |
2023年 | 67篇 |
2022年 | 119篇 |
2021年 | 146篇 |
2020年 | 154篇 |
2019年 | 150篇 |
2018年 | 136篇 |
2017年 | 150篇 |
2016年 | 167篇 |
2015年 | 160篇 |
2014年 | 236篇 |
2013年 | 265篇 |
2012年 | 293篇 |
2011年 | 331篇 |
2010年 | 238篇 |
2009年 | 249篇 |
2008年 | 192篇 |
2007年 | 248篇 |
2006年 | 254篇 |
2005年 | 244篇 |
2004年 | 177篇 |
2003年 | 140篇 |
2002年 | 83篇 |
2001年 | 82篇 |
2000年 | 65篇 |
1999年 | 50篇 |
1998年 | 31篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 22篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有4630条查询结果,搜索用时 15 毫秒
21.
The anaerobic digestion (AD) performance of spent cow bedding was investigated with different hydrothermal pretreatment (HP) conditions. Spent cow bedding was pretreated with low temperatures (50, 70, and 90℃) and different pretreatment times (2-72 h) with ammonia and without ammonia. The results showed that spent cow bedding was a good raw material for AD. After pretreatment, the concentration of volatile fatty acids (VFAs) in the group of hydrothermal pretreatments with ammonia (HPA) was higher than that in the HP group at the same pretreatment temperature and time. The optimal pretreatment condition was achieved with an HPA of 50℃ holding for 72 h. At the optimal condition, the highest concentration of VFAs was 1.58-10.85 times higher than that of the other pretreated groups. The highest hemicellulose and lignin removal rates were 58.07% and 10.32%, respectively. The highest methane yield was 163.0 ml·(g VS)-1, which was 48.9% higher than that of the untreated group. The VFAs, pH, and reducing sugars showed positive relationships with the methane yield. Therefore, HP at low temperature can enhance the AD performance of spent cow bedding. 相似文献
22.
23.
Jin-Seok Park David Nkurunziza Vikash Chandra Roy Truc Cong Ho Sung-Yeoul Kim Seung-Chan Lee Byung-Soo Chun 《International Journal of Food Science & Technology》2022,57(8):5090-5101
This study investigated the effect of sequential extraction techniques and pretreatment methods in enhancing the recovery of high-value products from spent coffee ground. Supercritical carbon dioxide (SC-CO2) deoiling was performed to recover non-polar lipids, and subcritical water (SCW) hydrolysis of deoiled spent coffee ground (SCG) was conducted involving pretreatment with ultrasound (US-SCG), and sample particle size reduction (PS-SCG). SCW temperature, solid/liquid mixing ratio, constant pressure and residence time were studied for their effect on extracting reducing sugars (RS), total phenolic content (TPC), total flavonoid content (TFC), 5-HMF, and furfural. Temperature increase enhanced hydrolysis efficiency and promoted RS dehydration into 5-HMF and furfural. At 180 °C and 40 mg/600 mL, TPC, TFC and RS values increased significantly with ultrasound pretreatment correlating with improved antioxidant activities by DPPH and ABTS assays. Highest amount of 5-HMF and furfural was obtained at 210°C (highest temperature studied) with 44.71 and 2.36 mg/100 g. Chlorogenic acid recovery was the highest in the non-deoiled SCG (15.07 mg/100 g), with no significant difference observed in PS-SCG, suggesting an increase due to its reduced particle size. The results of this study provide comprehensive knowledge on the combined effects of integrated engineering systems to boost the valorisation of SCGs into high-value products. 相似文献
24.
25.
26.
文章介绍了"分流预处理+MBR+Fenton"工艺在印制电路板废水处理上的应用,该工艺自2013年10月投产至今处理效果稳定。出水各项指标均达到相关标准。 相似文献
27.
针状焦是碳素材料中的优质品种,是生产超高功率石墨电极的主要原料。原料预处理的目的是脱除煤沥青的喹啉不溶物,溶剂法和改质法是已经实现工业化生产的煤系针状焦原料预处理方法。文章主要就这两种方法在我国煤系针状焦生产企业中的研究进展进行介绍。 相似文献
28.
29.
光整铝车轮对表面光泽要求高,而普通预处理工艺极易破坏其表面质量,导致失光或变色。采用双官能团自组装分子(SAM)无铬封闭预处理技术对光整铝车轮进行表面处理,讨论了预处理工艺流程,对影响光整铝车轮表面光泽和耐蚀性能的主要工艺参数进行了正交试验,获得了最佳的工艺参数:脱脂碱洗总碱点为6,无铬转化膜电导率为120μS/cm,SAM封闭电导率为160μS/cm。在此条件下对光整铝车轮表面进行预处理,然后喷涂丙烯酸透明粉,与经过普通预处理的试样进行对比,测试了涂膜性能。结果表明,经过SAM无铬封闭预处理的光整铝车轮,其表面光泽度保持率达97.7%,附着力0级。与普通预处理相比,SAM无铬封闭能显著提高光整铝车轮的耐蚀性能。 相似文献
30.