全文获取类型
收费全文 | 1805篇 |
免费 | 300篇 |
国内免费 | 256篇 |
专业分类
航空 | 1256篇 |
航天技术 | 538篇 |
综合类 | 213篇 |
航天 | 354篇 |
出版年
2024年 | 18篇 |
2023年 | 37篇 |
2022年 | 60篇 |
2021年 | 107篇 |
2020年 | 102篇 |
2019年 | 117篇 |
2018年 | 150篇 |
2017年 | 144篇 |
2016年 | 142篇 |
2015年 | 129篇 |
2014年 | 75篇 |
2013年 | 57篇 |
2012年 | 150篇 |
2011年 | 103篇 |
2010年 | 99篇 |
2009年 | 88篇 |
2008年 | 122篇 |
2007年 | 108篇 |
2006年 | 113篇 |
2005年 | 73篇 |
2004年 | 58篇 |
2003年 | 44篇 |
2002年 | 43篇 |
2001年 | 35篇 |
2000年 | 27篇 |
1999年 | 36篇 |
1998年 | 27篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
排序方式: 共有2361条查询结果,搜索用时 890 毫秒
801.
《中国航空学报》2021,34(2):539-553
Complete and efficient detection of unknown targets is the most popular application of UAV swarms. Under most situations, targets have directional characteristics so that they can only be successfully detected within specific angles. In such cases, how to coordinate UAVs and allocate optimal paths for them to efficiently detect all the targets is the primary issue to be solved. In this paper, an intelligent target detection method is proposed for UAV swarms to achieve real-time detection requirements. First, a target-feature-information-based disintegration method is built up to divide the search space into a set of cubes. Theoretically, when the cubes are traversed, all the targets can be detected. Then, a Kuhn-Munkres (KM)-algorithm-based path planning method is proposed for UAVs to traverse the cubes. Finally, to further improve search efficiency, a 3D real-time probability map is established over the search space which estimates the possibility of detecting new targets at each point. This map is adopted to modify the weights in KM algorithm, thereby optimizing the UAVs’ paths during the search process. Simulation results show that with the proposed method, all targets, with detection angle limitations, can be found by UAVs. Moreover, by implementing the 3D probability map, the search efficiency is improved by 23.4%–78.1%. 相似文献
802.
介绍了结合Harmony系统工程(SE)建模方法进行综合模块化航空电子(IMA)系统应用的开发,采用Rhapsody Harmony框架作为系统设计工具,在IMA应用软件需求进行分析的基础上创建软件模型,对系统的用例图、活动图、时序图、内部块图以及状态图进行了分析.阐述了在软件模型的基础上,基于Vx Works 653操作系统(OS)的IMA应用开发过程,涉及到模块操作系统的构建、分区操作系统的构建、应用的构建以及综合的构建,其中,模块操作系统的构建涉及到核心操作系统Makefile的开发,分区操作系统的构建涉及到分区操作系统配置表以及其Makefile的开发,应用的构建涉及到应用源程序、应用配置表以及其Makefile的开发,综合的构建涉及到模块配置表以及其Makefile的开发,将应用加载到IMA模块上进行了功能测试,IMA应用运行状态与Harmony软件模型行为一致. 相似文献
804.
为了缩短半球谐振陀螺仪寿命实验周期,降低实验成本,提出了一种针对漂移数据的残差修正ARGM(1,1)(Autoregressive GM(1,1))寿命预测方法。该方法利用神经网络与支持向量机中的自回归方式改进灰色模型,提高了模型的自适应能力,增强了模型的学习能力与预测能力,降低了模型回归学习的时间消耗和数据量要求,提高了预测效率。采用小波包络分析预处理某型号半球谐振陀螺仪的漂移数据,利用提出的预测方法对处理后的数据进行长周期预测,并结合灰色关联分析方法,分析失效阶段并最终预测出半球谐振陀螺仪的寿命。实验表明,残差修正ARGM(1,1)模型对半球谐振陀螺仪漂移数据的长期预测精度高于传统GM(1,1)模型、BP神经网络与支持向量机,结果也表明了研究方法的正确性和有效性。 相似文献
805.
《中国航空学报》2021,34(6):67-78
The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding. This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075 (AA7075) substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing. The interfacial microstructures and the strength of the brazed diamond joints were studied. The cross-section of the brazed diamond joint consists of a molten filler alloy layer, a molten pool, a heat effect zone, a columnar crystal zone and an equiaxed crystal zone. Within the interface of the filler alloy/substrate metal, microstructures observed possibly were Ag(s.s), Al(s.s), TixAl, Al2Cu and Mg intermetallic compounds. A layer of TiC with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy. The averaged peak shear force of the brazed joints was found to be approximately 39.8 N. The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding. However, the pulled-off of grit was found to be the primary failure of this type of brazed joint. This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding. 相似文献
806.
在国家数值风洞(NNW)工程的资助下,依托NNW-FSI流固耦合模拟软件平台,从气动载荷作用下飞行器结构静变形大小与收敛过程无关的物理机制出发,基于变形增量叠加的方式,设计和实现了一种静气动弹性耦合加速策略,通过松弛因子对耦合迭代的收敛过程进行调整。结合超大展弦比无人机和CHN-T1模型两种不同外形,开展了不同松弛因子下的静气动弹性耦合数值模拟,对耦合加速策略的参数影响和加速效果进行了测试和评估。从计算误差控制角度对松弛因子加速耦合迭代收敛的作用机制进行了理论分析,弄清3种类型静气动弹性耦合模拟过程中松弛因子发挥的作用,并给出了松弛因子选取范围的建议。静气动弹性耦合模拟和理论分析结果表明,针对不同类型的静气动弹性耦合问题,选取合适的松弛因子,能够达到抑制振荡并加速收敛的效果。 相似文献
807.
D. Buresova L.-A. McKinnell T. Sindelarova B.A. De La Morena 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper presents results from the Storm-Time Ionospheric Correction Model (STORM) validation for selected Northern and Southern Hemisphere middle latitude locations. The created database incorporated 65 strong-to-severe geomagnetic storms, which occurred within the period 1995–2007. This validation included data from some ionospheric stations (e.g., Pruhonice, El Arenosillo) that were not considered in the development or previous validations of the model. Hourly values of the F2 layer critical frequency, foF2, measured for 5–7 days during the main and recovery phases of each selected storm were compared with the predicted IRI 2007 foF2 with the STORM model option activated. To perform a detailed comparison between observed values, medians and predicted foF2 values the correlation coefficient, the root-mean-square error (RMSE), and the percentage improvement were calculated. Results of the comparative analysis show that the STORM model captures more effectively the negative phases of the summer ionospheric storms, while electron density enhancement during winter storms and the changeover of the different storm phases is reproduced with less accuracy. The STORM model corrections are less efficient for lower-middle latitudes and severe geomagnetic storms. 相似文献
808.
809.
Research on the intelligent design system for investment casting die of aero-engine turbine blade based on knowledge 总被引:1,自引:0,他引:1
JIANG Rui-song 《航空动力学报》2010,25(5):1061-1067
To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality. 相似文献
810.
针对STL(stereo lithography)文件在传递复杂几何实体模型信息方面具有精度高的特点,提出了一种基于STL文件计算复杂结构角系数和外热流的方法.根据单元和节点的拓扑关系识别六面体网格边界单元并进行辐射换热计算.详细阐述了基于STL文件和有限元法进行复杂结构的角系数和外热流的计算方法.研究了导热-辐射耦合计算的有限元方法.最后利用有限元法计算航天器关键部件在轨的三维瞬态温度场. 相似文献