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151.
霍尔推力器典型效率在50%左右,其余能量在电离、加速、耦合等过程中耗散掉,为了明确推力器优化设计的重点方向,需要定量地研究各个物理过程中损失的能量。因此,本文从能量损失分析的角度入手研究影响霍尔推力器效率的典型物理过程及机理,建立了针对霍尔推力器能量损失的系统性评价方法,为霍尔推力器设计及优化提供理论支撑。从霍尔推力器能量转化过程入手,并以能量的最终作用对象及性质作为分类的标准,建立了新的能量损失体系,认为霍尔推力器损失的能量主要有:径向羽流动能、阳极沉积热能、壁面沉积热能、电离能、阴极耦合损失。针对各项损失能量建立了实验评估方法,实验结果显示,阳极热沉积、壁面热沉积、羽流发散导致的能量损失是制约霍尔推力器效率的主导因素,其占比分别达到5.2%、24.7%、6.1%。实验测得所有输出功率占输入阳极放电功率比例达到102.1%,经不确定度分析,认为是阳极热沉积、电离能、阴极耦合损失的高估导致的,但该方法诊断得到的各项损失相对数量级关系是确定的,利用实验校核了方法的可行性,为霍尔推力器性能以及设计水平的评价提供了新的视角。 相似文献
152.
金锡焊料具有强度高、抗氧化性好、抗疲劳、蠕变性能优良等优点,在混合集成电路中得到越来越多的应用,尤其是在大功率高可靠集成电路中通过共晶焊接来降低封装热阻和提高芯片焊接可靠性。本文分析了国产金锡焊料的基础特性,基于国产金锡焊料采用手动方式进行功率芯片摩擦共晶焊接关键控制参数焊接工艺研究;对功率芯片金锡焊接宇航应用可靠性进行验证。结果表明,经历系列严苛的宇航环境热力学试验,剪切强度满足相关标准要求并保持强度稳定,显示了焊接的高可靠性。 相似文献
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《中国航空学报》2020,33(2):572-588
The design, manufacture and experiment of a shaft power unit for converting a micro-turbojet engine to a micro-turboprop in the class of less than 20 kW with the aim of obtaining maximum shaft power were described in this study. For this purpose, a Wren100 micro-turbojet engine was used as the gas generator, and the specifications of its outflow were measured. The optimal configuration of the inter-stage diffuser, which was an annular S-type diffuser, was selected based on its small total pressure drop and outlet flow uniformity. The power turbine was a single stage axial turbine that was designed based on the fixed nozzle angle assumption without any taper or twist in its stator. The turbine rotor was a bladed disk (Blisk) in which its unique blade profiles were designed based on the Wilson method. Subsequently, the shaft power unit was completed by designing and manufacturing an exhaust complex and gearbox. Finally, the micro-turboprop engine was tested with an overloading propeller. The results show a significant increase in the extracted power, an acceptable efficiency of the power turbine, and a significant reduction in the Specific Fuel Consumption (SFC) compared to other engines that use similar gas generators. 相似文献
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157.
模糊层次分析法在机场备用电源选择中的应用 总被引:2,自引:0,他引:2
传统观念认为只有柴油发电机组才适合作机场备用电源,其实国际民航组织并没有对备用电源采用何种设备做出具体限制,备用电源的选择面很广。结合当前新兴的微型燃气轮机发电技术和燃料电池发电技术,采用模糊层次分析法(Fuzzy AHP),对这三种电源进行综合性能评价,把难以量化的因素数字化,做出了具体的方案排序向量,为设计人员在实际工程中选用备用电源提供了参考。 相似文献
158.
基于脉冲电源的MOSFET驱动电路研究及应用 总被引:1,自引:0,他引:1
分析了在电火花等精密加工中MOSFET驱动器的隔离技术及特点,提出了可靠驱动MOSFET的设计思路,并在实际中得到应用。 相似文献
159.
Q.W. Song G.L. Huang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(8):1188-1190
In this paper, we report the statistical analysis of flare events observed by NoRH during 1992–2005 and NoRP during 1994–2005. We give the power law indices for the frequency distribution of peak brightness temperature which is 1.87 ± 0.05 for 17 GHz observation and is 1.64 ± 0.04 for 34 GHz observation. We also present the frequency variation of power law indices for peak flux and total energy of flare for NoRP observation, which is mono-increasing from 1 to 17 GHz. 相似文献
160.
Two freedom linear parameter varying μ synthesis control for flight environment testbed 总被引:2,自引:0,他引:2
To solve the problem of robust servo performance of Flight Environment Testbed(FET)of Altitude Ground Test Facilities(AGTF) over the whole operational envelope, a two-degree-offreedom μ synthesis method based on Linear Parameter Varying(LPV) schematic is proposed, and meanwhile a new structure frame of μ synthesis control on two degrees of freedom with double integral and weighting functions is presented, which constitutes a core support part of the paper. Aimed at the problem of reference command's rapid change, one freedom feed forward is adopted, while another freedom output feedback is used to meet good servo tracking as well as disturbance and noise rejection; furthermore, to overcome the overshoot problem and acquire dynamic tuning,the integral is introduced in inner loop, and another integral controller is used in outer loop in order to guarantee steady errors; additionally, two performance weighting functions are designed to achieve robust specialty and control energy limit considering the uncertainties in system. As the schedule parameters change over large flight envelope, the stability of closed-loop LPV system is proved using Lyapunov inequalities. The simulation results show that the relative tracking errors of temperature and pressure are less than 0.5% with LPV μ synthesis controller. Meanwhile, compared with non-LPV μ synthesis controller in large uncertainty range, the proposed approach in this research can ensure robust servo performance of FET over the whole operational envelope. 相似文献