全文获取类型
收费全文 | 165篇 |
免费 | 123篇 |
国内免费 | 11篇 |
出版年
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 14篇 |
2012年 | 2篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 15篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 32篇 |
1998年 | 21篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 15 毫秒
221.
As a main oxidizer in solid composite propellants, ammonium perchlorate (AP) plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid com-posite propellants. To improve the performance of solid composite propellant, it is necessary to take measures to modify the thermal decomposition behavior of AP. In recent years, transition metal oxides and carbon-supported transition metal oxides have drawn considerable attention due to their extraor-dinary catalytic activity. In this review, we highlight strategies to enhance the thermal decomposition of AP by tuning morphology, varying the types of metal ion, and coupling with carbon analogue. The enhanced catalytic performance can be ascribed to synergistic effect, increased surface area, more exposed active sites, and accelerated electron transportation and so on. The mechanism of AP decom-position mixed with catalyst has also been briefly summarized. Finally, a conclusive outlook and possible research directions are suggested to address challenges such as lacking practical application in actual formulation of solid composite propellant and batch manufacturing. 相似文献
222.
To help optimize the spacecraft design and reduce the risk of spacecraft mission failure, a new approach to assess the survivability of spacecraft in orbit is presented here, including the following three steps:1) Sensitivity Analysis of spacecraft. A new sensitivity analysis method, a ray method based on virtual outer wall, is presented here. Using rays to simulate the debris cloud can effectively address the component shadowing issues. 2) Component Vulnerability analysis of spacecraft. A function"Component functional reduction degree — Component physical damage degree"is provided here to clearly describe the component functional reduction. 3) System-level Survivability Assessment of spacecraft. A new method based on expert knowledge reasoning, instead of traditional artificial failure tree method, is presented here to greatly improve the efficiency and accuracy of calculation. 相似文献
223.
双转子活塞发动机是一种新型的差速式转子发动机,与传统发动机相比较具有很多优点,如不需要复杂的阀门装置,而且功率密度更高等。为了分析和研究双转子活塞发动机的运行特性,针对该发动机工作循环的热力学过程建立了其零维模型,确定了主要的边界条件,运用Matlab/simulink进行了数值模拟。对应不同的主轴转角,计算出气缸内工质的质量值、压力值和温度值。基于算得的压力值,求取了该发动机的平均指示压力和功重比等参数,与传统发动机相比较,双转子活塞发动机气缸工作容积的利用程度更大,整体结构更加紧凑。 相似文献
224.
225.
研究了多域伪谱时域(MPSTD)算法应用于波导问题分析时的激励源设置,并在此基础上,采用MPSTD算法计算了波导截止频率和典型三维波导结构的S参数,计算结果与HFSS或FDTD的计算结果做了比较,数值仿真表明,将MPSTD算法应用于波导问题的分析,可实现对波导问题的精确建模,具有较高的计算效率和计算精度,波导问题的MPSTD分析拓展了MPSTD算法的应用领域,为复杂波导问题的精确求解提供了一种思路。 相似文献
226.
We analyze a general but parsimonious price competition model for an oligopoly in which each firm offers any number of products. The demand volumes are general piecewise affine functions of the full price vector, generated as the “regular” extension of a base set of affine functions. The model specifies a product assortment, along with their prices and demand volumes, in contrast to most commonly used demand models. We identify a fully best response operator which is monotonically increasing so that the market converges to a Nash equilibrium, when firms dynamically adjust their prices, as best responses to their competitors' prices, at least when starting in one of two price regions. Moreover, geometrically fast convergence to a common equilibrium can be guaranteed for an arbitrary starting point, under an additional condition for the price sensitivity matrix. 相似文献
227.
某新型飞机武器控制系统故障诊断过程复杂,故障征兆和故障原因之间存在着许多不确定因素,精确定位故障存在许多困难.针对这种情况,提出了基于模糊神经网络,研究了模糊神经网络技术在武器控制系统故障诊断领域的应用,并根据系统本身的特点,提出了诊断和算法模型.在此基础上,研制出武器控制系统检查仪,对该方法作了验证.结果表明:该方法是可行和有效的. 相似文献
228.
胡汉武 《军队政工理论研究》2010,11(6)
世博安保丰富了政治工作的实践,并启示我们,必须把思想领先原则、强化组织功能、扎实有效的思想政治教育、抓好安全防范、严守安全底线、警民联手共保平安等工作贯穿任务始终. 相似文献
229.
230.