全文获取类型
收费全文 | 3631篇 |
免费 | 340篇 |
国内免费 | 82篇 |
专业分类
电工技术 | 125篇 |
综合类 | 184篇 |
化学工业 | 1499篇 |
金属工艺 | 74篇 |
机械仪表 | 85篇 |
建筑科学 | 521篇 |
矿业工程 | 70篇 |
能源动力 | 194篇 |
轻工业 | 148篇 |
水利工程 | 22篇 |
石油天然气 | 466篇 |
无线电 | 221篇 |
一般工业技术 | 238篇 |
冶金工业 | 135篇 |
原子能技术 | 18篇 |
自动化技术 | 53篇 |
出版年
2024年 | 25篇 |
2023年 | 94篇 |
2022年 | 220篇 |
2021年 | 282篇 |
2020年 | 156篇 |
2019年 | 125篇 |
2018年 | 101篇 |
2017年 | 96篇 |
2016年 | 143篇 |
2015年 | 130篇 |
2014年 | 192篇 |
2013年 | 187篇 |
2012年 | 233篇 |
2011年 | 230篇 |
2010年 | 158篇 |
2009年 | 209篇 |
2008年 | 155篇 |
2007年 | 181篇 |
2006年 | 168篇 |
2005年 | 151篇 |
2004年 | 120篇 |
2003年 | 125篇 |
2002年 | 93篇 |
2001年 | 103篇 |
2000年 | 83篇 |
1999年 | 65篇 |
1998年 | 43篇 |
1997年 | 26篇 |
1996年 | 29篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有4053条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
This work investigates the regeneration of S-poisoned Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts under different CH4 containing atmospheres. Under lean combustion conditions in the presence of excess O2, partial regeneration took place for both systems only above 750 °C after decomposition of stable sulphate species adsorbed
on the support. Under alternate lean combustion/CH4-reducing pulse regeneration is markedly anticipated down to 550–600 °C. Experiments evidenced an effective role of ceria
in preventing PdO from sulphation and in promoting regeneration via sulphates decomposition under reducing conditions. 相似文献
35.
The Pennsylvania State University is researching an advanced oxidation system, which includes an air-phase photolytic chamber, an air/water stripping tower, and granular activated carbon (GAC) beds, for controlling volatile organic compounds (VOCs).A laboratory-scale experimental procedure has been employed that simulated certain aspects of several full-scale installations. The apparatus has been used to characterize the loading capacity and mass transfer zone of selected VOCs on coconut shell GAC. The GAC bed has then been placed in series with an ultraviolet reactor, which generates ozone and advanced oxidants in order to regenerate the loaded GAC at intensities of advanced oxidants that were higher than full-scale installations.VOC loading tests revealed that the adsorption of methyl isobutyl ketone (MIBK) was characterized by a well-defined mass transfer zone. Upon exposure to UV/O3, desorption and/or destruction of the MIBK and other VOCs occurred most prominently within the first inch of the GAC bed. This correlated with the penetration of advanced oxidants into the GAC bed, which also occurred most significantly in the bed's first inch. However, the amount of oxidant penetration increased with time. The removal of oxidants from air by GAC was accompanied by a decrease in mass of the GAC. The ability of oxidants to penetrate a GAC bed was altered when the bed was loaded with a VOC. 相似文献
36.
37.
催化剂烧炭再生是非定态过程。本文建立了绝热反应器内催化剂烧炭模型,利用移动边界正交配置法求解。以结炭的BO2催化剂再生为工作反应,模拟预测与实验值吻合良好。模拟计算表明,用递升进口温度序列烧炭,使再生时间明显缩短。 相似文献
38.
39.
Controlled calcination of ion-exchanged Wyoming Bentonite in the presence and absence of ammonia leads to layer charge reductions. Detailed chemical analyses of both unexchangeable and exchangeable species lead to the conclusion that in no case is there migration of the original interlamellar cations into the octahedral region of the layers although, in terms of ionic radius alone, Mg2+, Ni2+ and, possibly Co2+, might be expected to do so. The production of unexchangeable Mg, Ni or Co, is identified as resulting from high temperature hydrolysis leading to hydroxide or oxide formation. 相似文献
40.
离子交换法处理含Cr(Ⅵ)废水的研究 总被引:4,自引:2,他引:4
采用201×7强碱性阴离子交换树脂处理模拟含Cr(Ⅵ)废水,探讨了废水酸度、交换时间、浓度对Cr(Ⅵ)去除率的影响以及树脂再生所需的合适温度和再生剂浓度。结果表明,201×7强碱性阴离子交换树脂处理模拟含Cr(Ⅵ)废水,具有交换容量大、交换效果好、树脂再生条件较简单等优点。并对实际含铬废水进行了处理,废水中Cr(Ⅵ)的初始浓度为1 540 mg/L,处理量达52 BV(床体积)时,出水中Cr(Ⅵ)的浓度仍小于0.5 mg/L,达到国家排放标准。树脂交换容量约80 mg/g。用8%NaOH溶液,在50℃条件下进行再生效果较好,再生率大于95%,可实现树脂的重复使用。 相似文献