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821.
822.
823.
压缩拐角是高超声速飞行器上的典型非连续区域,其分离/再附结构对局部热环境有较大影响。本文采用基于Navier-Stokes方程的自研程序,开展了典型压缩拐角外形的气动热环境数值模拟研究,分析了不同壁温条件下压缩拐角的热环境分布规律。计算结果表明:随着壁温升高,流场整体结构变化不大,但由于近壁面流体物性参数变化较大,导致拐角分离涡分离点向前移动、再附点向后移动,拐角处干扰区扩大;压缩拐角大部分区域的热流随着壁温的升高而减小,且干扰区内热流减小的幅度比无干扰区更大,但热流并不完全遵循随壁温升高而减小的规律。另外,通过对比变壁温计算热流和热壁修正公式修正热流,发现热壁修正公式在干扰区存在精度降低、适用性不足的问题。本文的研究进一步加深了壁温对压缩拐角流动影响的认识,缩小了热壁修正公式的适用范围。 相似文献
824.
针对功能磁共振成像数据中含有多个高斯信号源的盲源分离问题,介绍了一种成组典型相关分析方法(Group BSS-CCA)。这个方法的组分析框架参照了GIFT工具箱中的Group ICA算法,具体的典型相关分析方法应用的是Friman等人提出的BSS-CCA算法。以验证该方法的有效性为目的,设计了仿真实验;结果表明,该方法能较好识别出混合在人脑功能磁共振成像数据的2个空间高斯信号。Group BSS-CCA算法对研究人脑的功能磁共振成像数据具有较高的实用价值。 相似文献
825.
826.
《中国航空学报》2023,36(3):202-211
The safety and reliability of space connection and separation device has become a key issue due to the increasing service span of deep space exploration mission. The long-term preload relaxation (a key failure mode) of connection and separation devices is focused in this paper. A series of tests have been designed and implemented to investigate the preload relaxation regulation and a comprehensive method has been constructed to analyze and predict the reliable lifetime of the device. The two-stage preload relaxation law of the device is found and reasonably considered. Due to the different relaxation mechanism, the first-stage preload relaxation is assessed based on the working-condition test results, and the second-stage preload relaxation is characterized by accelerated test results. Finally, the service reliability and reliable life are evaluated. The experiment and assessment results demonstrate the reasonability and effectiveness of the proposed method which can achieve long-service reliability analysis for space connection and separation device within limited time. 相似文献
827.
级间分离过程中,可重复使用运载器受到非定常扰动,可能会造成分离失败。为研究级间分离过程中可重复使用运载器运动特性及周围流场分布随分离高度的变化情况,建立航天器和运载器的运动方程,使用动网格技术和有限体积法求解N-S方程。研究结果表明:随着级间分离高度的升高,气动力不断减小,非定常扰动对分离产生的影响越来越小;分离过程中,航天器和运载器的平动速度差较小,角速度差越来越小,最大差值从30 km高空的0.427 rad/s减小到50 km 高空的0.1 rad/s,二者之间的最小距离变大,更有利于安全分离。 相似文献
828.
《中国航空学报》2023,36(8):91-100
Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles, this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests. The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages, as well as the influence of aerodynamic interference between the two stages on each other’s motion. From the perspective of multi-angle physical equations, the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively, so as to ensure the authenticity and credibility of wind tunnel test results. The similarity law is verified by an HIFiRE-5 air vehicle, and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation. The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles. By analyzing the separation trajectory curve of the typical state, it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%, which indicates that this method is credible. The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles. 相似文献
829.
针对星箭分离过程,建立了减冲击环结构模型,并分析了该结构的减冲原理。利用冲击响应谱的时域合成算法计算获得符合冲击谱规范的时域载荷,并以此作为结构优化设计中动力学模型的输入载荷工况。以减冲击环的连续层数、单层支撑块数、连续层厚度、支撑块层高度以及环的外半径和内半径6个结构参数为设计变量,以减冲效果和结构强度、刚度为约束,以质量最轻为目标,建立减冲击环的结构优化设计模型,这是一包含离散变量和连续变量的混合优化问题。为了在跨平台下求解该混合优化问题,采用代理模型策略和自适应模拟退火算法求解,并在最优点处开展结构性能对设计变量的敏度计算,对计算结果进行了分析评估。本研究对强冲击动力学环境下的航天器结构分析与设计有一定的指导意义。 相似文献
830.
《中国航空学报》2022,35(8):30-44
It has been recently shown that Sub Boundary layer Vortex Generator (SBVG, abbreviated as VG hereafter) can suppress the Cross-Flow (CF), and therefore, can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages. However, when VGs are applied in high-load compressors, it is difficult to achieve ideal results. This is because the definition of the VG attack angle in the presence of CF in existing research is confusing, and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle. Therefore, this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate. The differences in the flow phenomena around a VG both with and without CF are also studied. The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect. However, the cross velocity increases when surmounting the primary vortex induced by the VG, except that this enhanced CF is less conspicuous for larger VG heights. Compared to the cases without CF, the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF. 相似文献