全文获取类型
收费全文 | 749篇 |
免费 | 158篇 |
国内免费 | 38篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 13篇 |
2020年 | 25篇 |
2019年 | 22篇 |
2018年 | 8篇 |
2017年 | 29篇 |
2016年 | 42篇 |
2015年 | 32篇 |
2014年 | 53篇 |
2013年 | 89篇 |
2012年 | 41篇 |
2011年 | 44篇 |
2010年 | 47篇 |
2009年 | 55篇 |
2008年 | 54篇 |
2007年 | 54篇 |
2006年 | 47篇 |
2005年 | 40篇 |
2004年 | 51篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 23篇 |
2000年 | 24篇 |
1999年 | 16篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有945条查询结果,搜索用时 0 毫秒
231.
232.
233.
飞行控制软件导航仿真模型遥测数据注入仿真 总被引:1,自引:0,他引:1
研究了飞行控制软件导航仿真模型遥测数据注入仿真中的一些问题,构造了遥测数据输入序列的误差补偿算法,重建相应的输入序列,使得将它们注入到相应的数字仿真模型进行仿真时,得到的输出与飞行试验中弹上计算机发送的遥测数据相符。 相似文献
234.
机动目标建模及机动检测算法 总被引:1,自引:0,他引:1
为解决机动目标跟踪问题,建立了非机动(匀速直线运动)和机动目标当前统计两种动态模型,并对机动目标当前统计模型的输入控制的估计进行了适当改进.同时对非机动模型的观测残差和机动模型的输入估计进行检验,以便准确检测目标机动. 相似文献
235.
In progressive censoring, items are removed at certain times during the life test. Commonly, it is assumed that the removed items are used for further testing. In order to take into account information about these additional testing in inferential procedures, we propose a two‐step model of stage life testing with one fixed stage‐change time which incorporates information about both the removed items (further tested under different conditions) and those remaining in the current life test. We show that some marginal distributions in our model correspond either to progressive censoring with a fixed censoring time or to a simple‐step stress model. Furthermore, assuming a cumulative exposure model, we establish exact inferential results for the distribution parameters when the lifetimes are exponentially distributed. An extension to Weibull distributed lifetimes is also discussed. 相似文献
236.
Reliability data obtained from life tests and degradation tests have been extensively used for purposes such as estimating product reliability and predicting warranty costs. When there is more than one candidate model, an important task is to discriminate between the models. In the literature, the model discrimination was often treated as a hypothesis test and a pairwise model discrimination procedure was carried out. Because the null distribution of the test statistic is unavailable in most cases, the large sample approximation and the bootstrap were frequently used to find the acceptance region of the test. Although these two methods are asymptotically accurate, their performance in terms of size and power is not satisfactory in small sample size. To enhance the small‐sample performance, we propose a new method to approximate the null distribution, which builds on the idea of generalized pivots. Conventionally, the generalized pivots were often used for interval estimation of a certain parameter or function of parameters in presence of nuisance parameters. In this study, we further extend the idea of generalized pivots to find the acceptance region of the model discrimination test. Through extensive simulations, we show that the proposed method performs better than the existing methods in discriminating between two lifetime distributions or two degradation models over a wide range of sample sizes. Two real examples are used to illustrate the proposed methods. 相似文献
237.
为用户设计了一个航空武器试验靶场,具备空空、空地和地空导弹试验能力,可机动部署,具有易于运行和运维代价低的特点。靶场由载机遥测系统、测量雷达、光电跟踪系统、微波和光纤通信系统、靶机遥测站、指挥控制等6个子系统构成;指挥控制子系统之外的5个子系统均使用国产成熟产品。在总体方案和指挥控制子系统设计中,对互联集成方案、机动部署、试验航线设计和发布、自动化领航、自动化指挥决策等5项关键技术进行了着重优化。在实际应用中,全靶场运行仅需20多成员(不含飞行和机场机务人员),3天内完成新试验场部署和联调,对作战部队飞行员进行5架次航线训练后即进行实弹试验,2天内完成多发中程拦截和近距格斗空空导弹试验。 相似文献
238.
Steady‐state diffusion approximations for discrete‐time queue in hospital inpatient flow management
下载免费PDF全文
![点击此处可从《海军后勤学研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this article, we analyze a discrete‐time queue that is motivated from studying hospital inpatient flow management, where the customer count process captures the midnight inpatient census. The stationary distribution of the customer count has no explicit form and is difficult to compute in certain parameter regimes. Using the Stein's method framework, we identify a continuous random variable to approximate the steady‐state customer count. The continuous random variable corresponds to the stationary distribution of a diffusion process with state‐dependent diffusion coefficients. We characterize the error bounds of this approximation under a variety of system load conditions—from lightly loaded to heavily loaded. We also identify the critical role that the service rate plays in the convergence rate of the error bounds. We perform extensive numerical experiments to support the theoretical findings and to demonstrate the approximation quality. In particular, we show that our approximation performs better than those based on constant diffusion coefficients when the number of servers is small, which is relevant to decision making in a single hospital ward. 相似文献
239.
《防务技术》2019,15(2):179-185
In this article, parametric study of single confined fragment launch device was carried out. The configuration proposed was further studied to derive the empirical relationship for effect of fragment size, charge size, confinement thickness on fragment velocity. The simulations were carried out using ANSYS-AUTODYNE explicit solver. Fragment velocities were estimated as a function of different parametric combinations of explosive quantities, charge length to diameter ratio, fragment height to diameter ratio, confinement thickness, fragment material and fragment mass. The data was further converted to charge to metal ratio under fragment and confinement. It was observed that, increase in confinement thickness, charge quantity and decrease in fragment height increases the fragment velocity. It is also noted that, charge to metal mass ratio under fragment significantly affects the fragment velocity. At the end, an empirical relationship for fragment velocity interms of all these parameters was established. Using these relations, two velocities 1831.92 m/s and 2523.9 m/s required for NATO STANAG 4496 IM test were estimated. The design parameters for these velocities are presented. Also, the results estimated using the empirical relationship has been compared with published experimental data. Error in the predicted velocities is within the acceptable range. The empirical relationship proposed will be useful for finalization of design of the fragment launch device. 相似文献
240.
在过阻尼RLC电路分时放电的基础上,提出新型高压方波脉冲产生方法。理论分析表明:过阻尼RLC电路产生的双指数电压波与脉冲形成线产生的方形电压波具有类似的上升沿和平顶。电路模拟表明:通过人工过零技术可以对双指数电压波进行截尾,从而形成完整的高压方波脉冲。建立了原理验证性样机,由两组RLC电路构成,每组电路包含一台脉冲电容器和一只三电极场畸变气体开关,两组电路共用一个上升沿调节电感。实验证明:样机可以在电阻负载上输出幅值为17 kV、平顶宽度为330 ns~5.8μs、上升沿为100~350 ns的单极性高压方波脉冲。该方法适应性强,对负载变化不敏感,同时具有良好的可调节性,方波上升沿、平顶宽度连续独立可调。 相似文献