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421.
CFD predictions of LBO limits for aero-engine combustors using fuel iterative approximation 总被引:1,自引:0,他引:1
Lean blow-out (LBO) is critical to operational performance of combustion systems in propulsion and power generation. Current predictive tools for LBO limits are based on decadesold empirical correlations that have limited applicability for modern combustor designs. According to the Lefebvre’s model for LBO and classical perfect stirred reactor (PSR) concept, a load parameter (LP) is proposed for LBO analysis of aero-engine combustors in this paper. The parameters contained in load parameter are all estimated from the non-reacting flow field of a combustor that is obtained by numerical simulation. Additionally, based on the load parameter, a method of fuel iterative approximation (FIA) is proposed to predict the LBO limit of the combustor. Compared with experimental data for 19 combustors, it is found that load parameter can represent the actual combustion load of the combustor near LBO and have good relativity with LBO fuel/air ratio (FAR). The LBO FAR obtained by FIA shows good agreement with experimental data, the maximum prediction uncertainty of FIA is about ±17.5%. Because only the non-reacting flow is simulated, the time cost of the LBO limit prediction using FIA is relatively low (about 6 h for one combustor with computer equipment of CPU 2.66 GHz · 4 and 4 GB memory), showing that FIA is reliable and efficient to be used for practical applications. 相似文献
422.
超低空飞行的航空拖靶需要高精度的高度控制,而作为试验和训练的消耗性装备,其低成本设计要求使得航空拖靶不能采用常规飞行器的高度控制方法。针对以拖曳力为飞行动力的航空拖靶,研究其基于非姿态控制的定高飞行的运动特性。定高飞行航空拖靶采用高稳定性的气动布局,并基于准直接力控制的升降舵面进行高度调整操纵。通过建立拖靶的纵向运动数学模型,设计非姿态控制定高飞行控制方法,详细分析拖靶气动特性,并进行定高飞行控制的仿真计算。计算结果给出拖靶的高度控制能力及飞行状态,结果表明拖靶具有一定的高度调整能力,可以实现定高飞行。 相似文献
423.
A motorized spindle supported by active magnetic bearings(AMBs) is generally used for ultra-high-speed machining. Iron loss of radial AMB is very great owing to high rotation speed, and it will cause severe thermal deformation. The problem is particularly serious on the occasion of large power application, such as all electric aero-engine. In this study, a prototype motorized spindle supported by five degree-of-freedom AMBs is developed. Homopolar and heteropolar AMBs are independently adopted as radial bearings. The influences of the two types of radial AMBs on the dynamic characteristics of the motorized spindle are comparatively investigated by theoretical analysis, test modal analysis and actual operation of the system. The iron loss of the two types of radial AMBs is analyzed by finite element software and verified through run-down experiments of the system. The results show that the structures of AMB have less influence on the dynamic characteristics of the motorized spindle. However, the homopolar structure can effectively reduce the iron loss of the radial AMB and it is useful for improving the overall performance of the motorized spindle. 相似文献
424.
Turbulence affects both combustion and NO formation. Fluctuation correlations are ideally used for quantitative analysis. From the instantaneous chemical reaction rate expression,ignoring the third-order correlation terms, the averaged reaction rate will have four terms, including the term of averaged-variable product, a concentration fluctuation correlation term, and temperature-concentration fluctuation correlation term. If the reaction-rate coefficient is denoted as K, the temperature fluctuation would be included in the K fluctuation. In order to quantitatively study the effect of turbulence on NO formation in methane-air swirling combustion, various turbulencechemistry models are tested. The magnitudes of various correlations and their effects on the time-averaged reaction rate are calculated and analyzed, and the simulation results are compared with the experimental measurement data. The results show that among various correlation moments, the correlation between the reaction-rate coefficient K fluctuation with the concentration fluctuation is most important and is a strong nonlinear term. 相似文献
425.
比较全面地介绍了-宽带中频相位计的研制过程。论述了相位计的工作原理,给出了系统框图。对各个部件的设计做了介绍,并给出了相位计所达到的技术指标。还介绍了系统测试方法和检定方法,对系统的误差做了分析,并给出了理论计算误差与实测误差的对应关系,提出了今后的进一步设想。 相似文献
426.
介绍了基于二阶项重写技术的机器发现逻辑理论及两个实验系统DI和ALP.同时举例说明了ALP系统的工作原理,展示了机器发现逻辑在数学发现(?)逻辑程序自动设计领域的应用前景。 相似文献
427.
在互联网上实现合作设计 总被引:9,自引:0,他引:9
在介绍现代设计的一般过程和基本特征的基础上 ,叙述了现代设计对知识和知识获取的强烈依赖 ,在互联网上获取知识、实现网上合作设计以及需要进一步解决的问题。 相似文献
428.
为了研究太空微重力环境对InSb 晶体生长的影响,在空间进行了InSb 晶体的重熔和再结晶实验。实验结果表明,空间可以生长出结构较完整、组份均匀的高质量单晶。另外还证明了利用多用途单晶生长炉内一侧余热进行单晶生长的可行性。 相似文献
429.
在微重力条件下,表面张力成为液体流动的主要驱动力,毛细现象更为显著。我们将铟、镉试样封装在石英试管中,在卫星自由飞行期间加热熔化井缓慢冷却后,考察铟、镉之间以及它们和石英玻璃之间的润湿行为和其他一些表面现象。分析认为:铟在地面和石英玻璃是润湿的,铟、镉是互溶的。但在微重力条件下,铟和石英玻璃不润湿,在试管中形成一小球。我们对铟球的半径、圆度作了测量,对圆度偏差及其产生原因进行了初步探讨。 相似文献
430.