全文获取类型
收费全文 | 89377篇 |
免费 | 11222篇 |
国内免费 | 7119篇 |
专业分类
电工技术 | 8363篇 |
技术理论 | 2篇 |
综合类 | 8526篇 |
化学工业 | 11225篇 |
金属工艺 | 5844篇 |
机械仪表 | 6112篇 |
建筑科学 | 7190篇 |
矿业工程 | 3463篇 |
能源动力 | 2454篇 |
轻工业 | 8347篇 |
水利工程 | 2973篇 |
石油天然气 | 3611篇 |
武器工业 | 1180篇 |
无线电 | 10676篇 |
一般工业技术 | 8163篇 |
冶金工业 | 3610篇 |
原子能技术 | 1498篇 |
自动化技术 | 14481篇 |
出版年
2024年 | 566篇 |
2023年 | 1537篇 |
2022年 | 3414篇 |
2021年 | 4624篇 |
2020年 | 3320篇 |
2019年 | 2466篇 |
2018年 | 2642篇 |
2017年 | 3121篇 |
2016年 | 2827篇 |
2015年 | 4281篇 |
2014年 | 5333篇 |
2013年 | 6241篇 |
2012年 | 7530篇 |
2011年 | 7933篇 |
2010年 | 7315篇 |
2009年 | 6884篇 |
2008年 | 6689篇 |
2007年 | 6721篇 |
2006年 | 5865篇 |
2005年 | 4692篇 |
2004年 | 3322篇 |
2003年 | 2327篇 |
2002年 | 2207篇 |
2001年 | 1808篇 |
2000年 | 1373篇 |
1999年 | 704篇 |
1998年 | 393篇 |
1997年 | 295篇 |
1996年 | 254篇 |
1995年 | 228篇 |
1994年 | 159篇 |
1993年 | 99篇 |
1992年 | 95篇 |
1991年 | 69篇 |
1990年 | 54篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 29篇 |
1979年 | 17篇 |
1977年 | 9篇 |
1976年 | 19篇 |
1959年 | 18篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
对PCB废水总氮的处理,从源头削减、分质收集、分质预处理到末端处理提出了多种方法,着重分析了MAP+管式微滤膜处理氨氮废水、多级组合式RO处理硝态氮废水和A2O+MBR处理综合废水,提出PCB废水总氮达标的组合工艺,项目建成后达到预期效果。 相似文献
32.
ABSTRACTImproving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%. 相似文献
33.
34.
35.
36.
按照管道加工工艺的不同,管道可分为内径控制管和外径控制管。通过热轧工艺生产的外径控制无缝钢管,可满足火力发电厂汽水系统中绝大部分管道的使用要求。对于超(超)临界机组的主蒸汽和高温再热蒸汽管道采用的P91/P92材质的大口径厚壁无缝钢管,由于对材料性能和加工工艺有特殊要求,因此宜采用内径控制管。 相似文献
37.
Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm2 for Mg alloy to 13 μA/cm2 for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications. 相似文献
38.
Although Mg alloy possesses high specific strength, low density, and good biocompatibility, poor corrosion resistance hinders its further applications. In the present study, an innovative protective layer against corrosion was prepared on the AZ31 Mg alloy via alkali pretreatment followed by vanillic acid treatment. The alkali pretreatment supplied –OH for the AZ31 Mg alloy surface to react with vanillic acid. The vanillic acid treatment played a crucial role in enhancing the corrosion resistance due to the excellent ability to act as a barrier and retard aqueous solution penetration, which effectively isolated the underlying Mg alloy from the corrosive environment. The corrosion current density of alkali and vanillic acid-treated Mg alloy (AZ31V) almost showed two orders of magnitude lower values in comparison with that of the AZ31 Mg alloy, and the corrosion potential of AZ31V Mg alloy increased from −1.41 to −1.25 V. The immersion tests proved that there was no occurrence of severe corrosion. Hence, the alkali pretreatment and vanillic acid treatment may represent a promising method to improve the corrosion resistance of Mg alloy. 相似文献
39.
40.