全文获取类型
收费全文 | 204篇 |
免费 | 7篇 |
国内免费 | 39篇 |
专业分类
化学 | 212篇 |
力学 | 5篇 |
物理学 | 33篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 11篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 6篇 |
2010年 | 11篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 12篇 |
2006年 | 19篇 |
2005年 | 23篇 |
2004年 | 17篇 |
2003年 | 21篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
排序方式: 共有250条查询结果,搜索用时 62 毫秒
61.
62.
63.
利用小型固定流化床实验装置研究了催化裂化(FCC)汽油在专门开发的多产低碳烯烃催化剂上的裂解性能。研究表明,反应温度对原料转化率、总低碳烯烃产率的影响最大,剂油比和水油比对低碳烯烃的产率影响较小,而随着重时空速的增大,总低碳烯烃产率略有降低;确定了FCC汽油催化裂解制低碳烯烃的实验室最优反应条件,即反应温度、剂油比、重时空速和水油比分别为660℃、12、15h-1和0.8。根据反应条件与裂解产物的关系提出了催化裂解反应深度函数,并建立裂解产物产率与催化裂解反应深度函数之间的关联模型。随催化裂解反应深度函数的增加,乙烯产率持续增加,而丙烯和丁烯产率出现最大值,利用此模型可以对产物产率进行预测。 相似文献
64.
Sun Choi Seung Hoon Oh Yong Seung Kim Kyeong Hak Seong Byeung Soo Lim Jong Hyung Lee 《Catalysis Surveys from Asia》2006,10(2):110-116
SK Corporation developed an advanced pyrolysis gasoline (pygas) upgrading (APUSM) technology based on a catalytic process for producing valuable benzene, toluene and xylenes (BTX) and liquefied petroleum gas (LPG) from pygas containing aromatics and non-aromatic hydrocarbons. Hydrodealkylation of heavy aromatics and hydrocracking of non-aromatic hydrocarbons occurred with facility in the conversion of pygas over a proprietary catalyst, metal promoted zeolite. This catalytic process produced benzene and toluene with high purity corresponding to chemical grade while giving mixed xylenes with reduced ethylbenzene. In the present study, we described novel features of the APUSM technology in terms of the process and catalyst. The influence of the process conditions was also examined. This technology has been commercially proven, and hence is available for licensing through Axens, which is a major engineering and licensing company. 相似文献
65.
Katerina Goundani Christina Papadopoulou Christos Kordulis 《Reaction Kinetics and Catalysis Letters》2004,82(1):149-155
The reduction of benzene from benzene-rich real gasoline fractions has been studied in a high-pressure fixed-bed reactor using
a Pt/TiO2 catalyst. It was found that the yield of this process decreases with the toluene content in the feedstock, but it is independent
of the kind of the saturated hydrocarbons.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
66.
The oxidation of several mixtures of surrogate for gasoline was studied using a jet stirred reactor and a shock tube. One representative of each classes constituting gasoline was selected: iso-octane, toluene, 1-hexene and ethyl tert-butyl ether (ETBE). The experiments were carried out in the 800-1880 K temperature range, for two different initial pressures (0.2 and 1 MPa), with an initial fuel molar fraction of 0.001. The equivalence ratio varied from 0.5 to 1.5. Each hydrocarbon sub-mechanism was validated using shock tube data. The full mechanism describing the surrogate fuel oxidation is constituted of the sub-mechanisms for each fuel components and by adding interaction reactions between different hydrocarbon fragments. Good agreement between the experimental results and the computations was observed under JSR and shock tube conditions. 相似文献
67.
In an r-FIA single-line manifold, 10-l portions of 5,5-dithiobis (2-nitrobenzoic acid) and 2% (v/v) ethylenediamine in 80 20 inethanol: acetone are injected from pressurized containers via high-speed on/off valves into a flowing gasoline stream. The reaction product, 2-nitro-5-mercaptobenzoate, is detected optically at 412 nm after a reaction time of 15s. The system is intended for the measurement of mercaptans in the 0–2 mM (0–64 ppm S) concentration range. The response for C1–C10n-mercaptans ranges from 0.766–0.159 mAU/mM, the response to C1–C5n-mercaptans is 630 mAU/mM (±18.5% RSD). The response ratio of C1 and C5 mercaptans is 1 0.653. The system permits extreme conservation of reagents; only 10 l of each reagent is consumed per determination. 相似文献
68.
FCC汽油模型化合物光催化氧化脱硫的研究 总被引:9,自引:1,他引:8
以噻吩的二甲苯溶液作为FCC汽油的模型化合物, 双氧水为氧化剂, 研究了在光催化作用下, 双氧水体积分数、 高速均质时间和二氧化钛的加入量等工艺条件对脱硫率的影响, 在适宜条件下, 模型化合物的脱硫率可达到80%以上. 以FCC汽油为实际体系, 在适宜的光催化条件下, 脱硫率可达到59%. 分析结果表明, 含硫化合物的氧化产物为更高极性的物质. 相似文献
69.
汽油样品类型的模式识别研究与应用 总被引:3,自引:0,他引:3
研究了应用化学计量学方法解决汽油单体烃的气相色谱分析中单体烃定性库的自动选择问题。通过提取汽油单体烃谱图中的29个组分及其含量信息作为特征值,利用主成分分析法对不同工艺得到的催化裂化汽油、焦化汽油、直馏汽油、重整汽油和烷基化汽油进行分类,结合相似分析方法(即SIMCA方法)建立了各类汽油样本的类模型,借助这些类模型可以实现对未知样本的类型判别。所提出的识别方法可方便快速地判别待分析样品所属的汽油类别,并据此推荐适合该样品的定性模型库,从而实现汽油单体烃的快速、自动分析。 相似文献
70.
Young-Sam Shim Gyung-Min Choi Duck-Jool Kim 《International Journal of Multiphase Flow》2009,35(10):885-895
The spray–wall impingement process in gasoline direct injection (GDI) engines, which is caused by the interaction among spray, wall and air to move the air–fuel mixture near the spark plug, directly influences the engine performance and emissions. Therefore, a detailed understanding of this process is very important in designing an injection system and controlling a strategy of GDI engines. The purpose of this study is to understand the spray–wall impingement characteristics for more efficient designing of the injection system in GDI engines and to supply the fundamental data under engine operation conditions. The wall impingement processes of hollow-cone fuel spray according to ambient gas conditions and wall geometry are calculated by validated spray models. The calculated results were compared with the experimental results obtained by the laser-induced exciplex fluorescence (LIEF) technique. It was found that the spray and vortex cloud at the high ambient pressure were distributed at inner area of cavity and the more fuel film mass observed at this condition. The fuel film mass decreased with the increase of ambient temperature, while the fuel film mass increased at high cavity angles. 相似文献