全文获取类型
收费全文 | 531篇 |
免费 | 194篇 |
国内免费 | 33篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 33篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 21篇 |
2016年 | 50篇 |
2015年 | 26篇 |
2014年 | 57篇 |
2013年 | 63篇 |
2012年 | 44篇 |
2011年 | 36篇 |
2010年 | 26篇 |
2009年 | 43篇 |
2008年 | 25篇 |
2007年 | 40篇 |
2006年 | 27篇 |
2005年 | 38篇 |
2004年 | 25篇 |
2003年 | 22篇 |
2002年 | 11篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 19篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 3篇 |
排序方式: 共有758条查询结果,搜索用时 83 毫秒
71.
试验研究了穿甲子弹垂直侵彻高强防弹钢的机理,提出了一个分析靶板极限速度和弹体剩余速度的理论模型,该模型综合考虑了材料的应变率与热软化效应,结果表明,理论值与试验值吻合很好.分析了失效准则的影响,研究了剪切带温度和靶板耗能随入射速度的变化规律. 相似文献
72.
73.
利用LS—DYNA软件分析弹体攻角和目标运动对穿甲过程中装药安定性、弹体剩余速度及弹头姿态的影响。在穿甲过程中,弹体速度为300m/s,攻角分别为0°,10°和20°,弹体和目标板选择了考虑应变、应变率和温度效应的Johnson—cook材料模型。结果表明:随攻角的增大,装药局部受力显著增大,弹体剩余速度下降,弹头发生偏转;目标运动使穿甲能力减弱,但目标运动会使装药受到的外力在一定程度上减少。 相似文献
74.
75.
为了研究爆炸冲击波对武器装备的损伤,建立了炸药爆炸冲击靶板的有限元模型,对不同厚度靶板在确定爆炸冲击环境下的损伤进行了仿真试验。不同于传统的宏观破口尺寸损伤表征参数,引入了等效塑性应变来精确描述靶板损伤,并提出了一种基于主成分分析理论对靶板损伤进行评估的方法。结果表明:利用该方法所得到的计算结果与理论分析结果完全一致。这说明基于多元统计分析的靶板损伤评估方法是切实可行的,可以进一步应用于装备爆炸损伤评估与易损性研究中。 相似文献
76.
We consider a general linear filtering operation on an autoregressive moving average (ARMA) time series. The variance of the filter output, which is an important quantity in many applications, is not known with certainty because it depends on the true ARMA parameters. We derive an expression for the sensitivity (i.e., the partial derivative) of the output variance with respect to deviations in the model parameters. The results provide insight into the robustness of many common statistical methods that are based on linear filtering and also yield approximate confidence intervals for the output variance. We discuss applications to time series forecasting, statistical process control, and automatic feedback control of industrial processes. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010 相似文献
77.
基于ANSYS/LS—DYNA的电子装备爆炸冲击振动损伤建模研究 总被引:1,自引:0,他引:1
针对电子装备爆炸冲击振动损伤问题,设计了损伤模拟的基本方案;采用ANSYS/LS—DYNA建立了二维“爆炸源-地面-弹性体-电子装备”模型;通过模型试验,获得了与实际爆炸冲击振动特性相吻合的加速度、位移和应力等数据。 相似文献
78.
《防务技术》2019,15(3):363-368
The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20–26 mm in the composites as compared to 37 mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles. 相似文献
79.
80.
《防务技术》2019,15(4):495-505
Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge (RLSC) are investigated by experiments and simulations. The reactive materials liner with a density of 2.3 g/cm3 is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380 °C. Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of 0.5, 1.0, and 1.5 CD (charge diameter), respectively. The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff, while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff. To understand the unusual experimental results, numerical simulations based on AUTODYN-2D code are conducted to discuss the wave shaper effect, including the propagation behavior of detonation wave, the velocity and temperature distribution of reactive jet, and penetration depth of reactive jet. The simulations indicate that, compared with RLSC without wave shaper, there is a higher temperature produced inside reactive jet with wave shaper. This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline, which results in significantly decreasing its penetration performance. 相似文献