全文获取类型
收费全文 | 73篇 |
免费 | 10篇 |
国内免费 | 10篇 |
专业分类
化学 | 28篇 |
晶体学 | 1篇 |
力学 | 12篇 |
综合类 | 2篇 |
数学 | 17篇 |
物理学 | 33篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 3篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有93条查询结果,搜索用时 15 毫秒
51.
Performance of supersonic model combustors with staged injections of supercritical aviation kerosene 总被引:1,自引:0,他引:1
Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Supercritical kerosene of approximately 760 K was prepared and injected in the overall equivalence ratio range of 0.5-1.46. Two pairs of integrated injector/flameholder cavity modules in tandem were used to facilitate fuel-air mixing and stable combustion. For single-stage fuel injection at an upstream location, it was found that the boundary layer separation could propagate into the isolator with increasing fuel equivalence ratio due to excessive local heat release, which in turns changed the entry airflow conditions. Moving the fuel injection to a further downstream location could alleviate the problem, while it would result in a decrease in combustion efficiency due to shorter fuel residence time. With two-stage fuel injections the overall combustor performance was shown to be improved and kerosene injections at fuel rich conditions could be reached without the upstream propagation of the boundary layer separation into the isolator. Furthermore, effects of the entry Mach number and pilot hydrogen on combustion performance were also studied. 相似文献
52.
53.
Elaine Rocha da Luz Thiago Fernando Mota Gonsalves Ricardo Queiroz Aucélio 《Journal of separation science》2009,32(12):2058-2065
SPE in combination with HPLC and fluorescence detection has been used for sensitive determination of six basic azaarenes (7,8-benzoquinoline, 7,9-dimethylbenz[c]acridine, 9-amino-1,2,3,4-tetrahydroacridine, 9-methylacridine, acridine, and dibenz[a,j]acridine) in aviation kerosene (jet fuel). SPE was performed in a single step using a strong cation exchange sorbent. The HPLC system consisted of C18 column with a selected detection program of optimal λexc and λem. A gradient elution with ACN and phosphate buffer (pH 6.5) at a flow rate of 1 mL/min allowed efficient and fast separation of azaarenes within 15 min. The LOD and LOQ values (S/N ratio 3:1 and 10:1, respectively) were between 0.0013 and 0.021 and from 0.0044 to 0.072 ng per injection. The calibration curves showed linear behavior from the LOQ to 250 μg/L (r2 >0.99). For the spiked concentration of 6.0 μg/L, recoveries were from 92 to 107% for jet fuel samples, except for 9-amino-1,2,3,4-tetrahydroacridine, which presented 68% recovery. The proposed method was applied to the quantification of those six basic azaarenes in one commercial kerosene and in three aviation kerosene samples. The presence of 7,8-benzoquinoline (up to 3.2 μg/L) and dibenzo[a,j]acridine (up to 6.3 μg/L) was confirmed in aviation kerosene. 相似文献
54.
尹富 《数学的实践与认识》2013,43(8):104-109
航空装备技术保障能力是组成航空兵战斗力的基本要素之一,其能力的高低直接影响到航空装备保障任务完成质量的优劣,因此对航空装备技术保障能力进行科学评价具有重要意义.在现有研究的基础上建立了航空装备技术保障能力评价指标体系,基于灰色关联分析方法提出了指标权重的确定方法,并利用灰色关联分析思想构建出航空装备技术保障能力评价模型,为航空装备技术保障能力评价提供量化分析模型,拓展了航空装备技术保障能力评价模型体系. 相似文献
55.
航空器在进行空-地通信时,信道中会存在大量非线性的干扰信号,导致通信信号发生鲁棒性变化。提出一种基于信息最大化算法的航空通信中干扰下的鲁棒性通信方法,根据航空通信的特点建立通信模型,利用均值化处理方法和白化处理方法对通信信号进行预处理,利用信息最大化算法对信号进行信澡分离,实现了航空通信信号的鲁棒性要求;在Matlab7.0平台上完成测试,实验时航空通信划分成外部干扰,能够忽略和外部干扰不可忽略两种情况;仿真时间定为3 000 s,干扰源数目为12个,实验结果表明利用该算法对原始信号的拟合率达到97%左右,鲁棒性误差平均在3%左右,而传统算法误差在10%以上,表明该算法信号的鲁棒性更强。 相似文献
56.
57.
58.
RP-3替代燃料自点火燃烧机理构建及动力学模拟 总被引:11,自引:0,他引:11
通过对RP-3 航空煤油成分的分析, 以及对8 组替代模型的对比实验, 选取了73.0%(质量分数)正十二烷, 14.7% 1,3,5-三甲基环己烷, 12.3%正丙基苯作为RP-3 航空煤油的替代模型. 使用本课题组自主研发的机理自动生成程序ReaxGen, 构建了RP-3 替代燃料的高温燃烧详细机理, 用该机理模拟了激波管点火延时, 并与实验数据进行比较. 用物质产率分析和近似轨迹优化算法(ATOA)简化方法简化了详细机理. 最后对燃烧机理在不同化学计量比及压力条件下的点火延时做了敏感度分析, 考察了燃烧机理在不同化学计量比下关键反应的异同. 结果表明, 该替代模型的燃烧机理能很好地描述RP-3煤油的高温点火特性. 相似文献
59.
In this paper, compressible flow of aviation kerosene at supercritical conditions has been studied both numerically and experimentally. The thermophysical properties of supercritical kerosene are calculated using a 10 species surrogate based on the principle of extended corresponding states (ECS). Isentropic acceleration of supercritical kerosene to subsonic and supersonic speeds has been analyzed numerically. It has been found that the isentropic relationships of supercritical kerosene are significantly different from those of ideal gases. A two-stage fuel heating and delivery system is used to heat the kerosene up to a temperature of 820 K and pressure of 5.5 MPa with a maximum mass flow rate of 100 g/s. The characteristics of supercritical kerosene flows in a converging-diverging nozzle (Laval nozzle) have been studied experimentally. The results show that stable supersonic flows of kerosene could be established in the temperature range of 730 K-820 K and the measurements in the wall pressure agree with the numerical calculation. 相似文献
60.
正癸烷燃烧机理及航空煤油点火延时动力学模拟 总被引:5,自引:0,他引:5
以单一正癸烷作为国产航空煤油的单组分替代模型, 应用自有的碳氢燃料反应机理生成程序ReaxGen-Combustion构建了燃烧反应的详细机理. 以国产煤油在加热型激波管上的燃烧实验为参考, 对比研究了文献报道的3组分替代模型(模型Ⅰ)、2组分替代模型(模型Ⅱ)以及本文的单组分替代燃烧反应机理(模型Ⅲ)在预测我国航空煤油点火延时特性方面的实用性. 结果表明, 温度在1052~1538 K时, 模型Ⅰ预测的点火延时与实验值相差较大; 模型Ⅲ在温度高于1176 K时的预测值与实验值符合较好, 在1052~1176 K之间时则相差较大; 模型Ⅱ与模型Ⅲ预测值符合很好, 由于前者考虑了低温反应机理, 因而对1052~1176 K区间的预测精度与模型Ⅲ相比有所改善. 计算还发现, 模型Ⅱ中添加的20%(质量分数)1,2,4-三甲基苯对高温段点火延时未产生明显影响. 相似文献