全文获取类型
| 收费全文 | 5566篇 |
| 免费 | 2265篇 |
| 国内免费 | 689篇 |
专业分类
| 航空 | 4684篇 |
| 航天技术 | 1270篇 |
| 综合类 | 651篇 |
| 航天 | 1915篇 |
出版年
| 2025年 | 53篇 |
| 2024年 | 139篇 |
| 2023年 | 199篇 |
| 2022年 | 367篇 |
| 2021年 | 364篇 |
| 2020年 | 368篇 |
| 2019年 | 304篇 |
| 2018年 | 266篇 |
| 2017年 | 370篇 |
| 2016年 | 293篇 |
| 2015年 | 351篇 |
| 2014年 | 368篇 |
| 2013年 | 423篇 |
| 2012年 | 480篇 |
| 2011年 | 469篇 |
| 2010年 | 459篇 |
| 2009年 | 455篇 |
| 2008年 | 408篇 |
| 2007年 | 379篇 |
| 2006年 | 389篇 |
| 2005年 | 282篇 |
| 2004年 | 181篇 |
| 2003年 | 182篇 |
| 2002年 | 197篇 |
| 2001年 | 172篇 |
| 2000年 | 118篇 |
| 1999年 | 101篇 |
| 1998年 | 67篇 |
| 1997年 | 58篇 |
| 1996年 | 49篇 |
| 1995年 | 33篇 |
| 1994年 | 32篇 |
| 1993年 | 19篇 |
| 1992年 | 30篇 |
| 1991年 | 22篇 |
| 1990年 | 19篇 |
| 1989年 | 19篇 |
| 1988年 | 11篇 |
| 1987年 | 11篇 |
| 1986年 | 1篇 |
| 1985年 | 3篇 |
| 1984年 | 1篇 |
| 1983年 | 4篇 |
| 1982年 | 3篇 |
| 1965年 | 1篇 |
排序方式： 共有8520条查询结果，搜索用时 0 毫秒
1.
Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments.A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute. 相似文献
2.
To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) in a simple visual selective response task were compared between HDT and HUT in 9 normal subjects. The results were: The Target(T) and non-Target(NT) flash signals both induced significant slow positive potentials which were supposed to related to the attention state; the amplitude of the positive potentials in frontal regions decreased significantly especially for NT-ERPs during HDT comprared with that during HUT. The data reported provide new evidence indicating that more attention should be paid on the brain function study during space flight. 相似文献
3.
4.
本文对光线追踪求交算法进行了深入讨论。文中结合形体设计实例说明了此算法的正确性和实用性。 相似文献
5.
6.
7.
文章主要介绍了美国火星探测用降落伞研制过程以及在研制过程中的一些主要试验，并同时指出了试验中的一些特点。 相似文献
8.
In this paper a linear, closed-form analysis of the buckling behavior of an orthotropic plate with elastic clamping and edge reinforcement under uniform compressive load is presented. This is a typical structural situation found in aerospace engineering for instance as stiffeners in wings or the fuselage. All governing equations are transformed in a dimensionless system using common characteristic quantities to gain good analytical access. The buckling behavior is analyzed and generic buckling diagrams are presented. The solutions show excellent agreement with results from literature and numerical analyses.The minimum bending stiffness of the edge reinforcement needed to withstand buckling is examined and a minimum stiffness criterion is presented. Furthermore an absolute minimum bending stiffness is found which is sufficient to enable the reinforcement to act as a near-rigid support for arbitrarily long plates. These criteria are of interest for optimized lightweight design of stringers and stiffeners. 相似文献
9.
解为 《长沙航空职业技术学院学报》2013,(3):10-12
加强高职学生职业精神培育是高等职业教育的内涵发展要求。通过分析培育高职学生职业精神的重要性、阐述职业精神的构成要素和主要内容、结合高等职业院校自身特点提出职业精神培育的有效途径,以期使高等职业院校提高对学生职业精神培育的重视,并在实施过程中有所借鉴。 相似文献
10.
大曲率弯道和叶栅内的湍流数值模拟 总被引：3，自引：0，他引：3
本文在贴体曲线坐标系下应用非交错网格技术，发展了适于求解复杂流动的压力修正算法，采用速度的协变物理分量为动量方程的求解变量，推导得出一个适于任何曲线坐标系下控制单元体界面流通量的插值模式，可以有效地抑制不合理的波动压力场，计算表明，算法稳定收敛，计算值与试验值吻合良好，同时能预示通道内复杂的流动现象。 相似文献