全文获取类型
收费全文 | 244篇 |
免费 | 74篇 |
国内免费 | 9篇 |
出版年
2024年 | 4篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 23篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 25篇 |
2013年 | 11篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
排序方式: 共有327条查询结果,搜索用时 15 毫秒
181.
Yf Reykers 《Contemporary Security Policy》2017,38(3):457-470
This article reviews the gloomy saga of the EU Battlegroups, focusing on four questions: Where do they come from? What do they look like? What have they been hindered by? And where do they go from here? It builds upon earlier findings in the literature and adds novel insights based on original data. In doing so, the article pays particular attention to the standby nations’ constant calculation of political and financial costs. It argues that recognizing these cost–benefit calculations allows for identifying the most crucial areas to be tackled to make the EU Battlegroups functional. In addition, the article stresses that these considerations play out in a setting wherein the Battlegroups are just one among many policy instruments available for rapid response. 相似文献
182.
美军"作战云"理论的制胜机理是以云计算技术作为物质基础和技术依托,以"云部署、云聚合、云攻击(防御)、云消散"体现作战过程,以"集中指挥、分布式控制和分散执行"为基本指控方式,以"跨域协同"作为作战协同的基本方式。由于该理论实现了战场信息的有效融合和共享,作战力量的动态聚能和释能,作战任务的临时赋予和即时完成以及不同领域作战能力的互补增效,因此将促使美军的武器装备、力量结构、作战方式及战场形态等发生新的重大变化。 相似文献
183.
184.
利用电爆丝的一种红外脉冲强光辐射新技术,从理论和实验上研究了电爆丝的爆炸机理。用电爆丝绝热加热模型数值模拟了电爆丝在冲击大电流作用下的电爆炸特性,电爆丝根数对电爆炸特性的影响。实验结果与理论模拟相一致。 相似文献
185.
对双连杆机构的运动学进行了理论分析,推导出了活塞的位移、速度和加速度公式及活塞侧连杆和曲轴侧连杆摆角公式,并且针对一实例进行了计算,与相同结构尺寸的传统曲柄连杆机构发动机作了比较分析. 相似文献
186.
研究了2种φ2mm粉芯丝材电弧喷涂Fe-Cr-Ni涂层和7Crl3涂层以及与2种典型润滑油抗磨添加剂的协同效应,并借助X光电子能谱(XPS)研究了其协同作用机理.结果表明DBP和ZDDP润滑油抗磨添加剂能明显地改善电弧喷涂Fe-Cr-Ni涂层和7Cr13涂层的抗磨性.添加剂DBP能显著地降低2种电弧喷涂涂层/GCr15摩擦副的摩擦系数,但ZDDP抗磨添加u剂的减摩效果不太显著.在含DBP和ZDDP添加剂油润滑条件下,涂层磨痕表面形成了摩擦化学反应膜. 相似文献
187.
Yu-xiang Sun Xin Wang Chong Ji Chang-xiao Zhao Pei-li Liu Lei Meng Kun Zhang Tao Jiang 《防务技术》2021,17(4):1496-1513
In this study, the anti-penetration performance of polyurea/ASTM1405-steel composite plate subjected to high velocity projectile was analyzed. Two kinds of modified polyurea material (AMMT-053 and AMMT-055) were selected and a ballistic impact testing system including speed measuring target system and high-speed camera was designed. This experiment was conducted with a rifle and 5.8 mm projectile to explore the effects by the polyurea coating thickness, the polyurea coating position and the glass-fiber cloth on the anti-penetration performance of polyurea/ASTM1405-steel composite plate. The result showed that the effects of polyurea coating position were different between two types of polyurea, and that the effects of glass-fiber position were disparate between two types of polyurea as well. For AMMT-053 polyurea material, it was better to be on front face than on rear face; whereas for AMMT-055 pol-yurea, it was better to be on rear surface although the difference was very subtle. Additionally, formulas had been given to describe the relationship between the effectiveness of polyurea and the thickness of polyurea coating. In general, AMMT-055 had better anti-penetration performance than AMMT-053. Furthermore, five typical damage modes including self-healing, crack, local bulge, spallation and local fragmentation were defined and the failure mechanism was analyzed with the results of SHPB test. Additionally, the bonding strength played an important role in the anti-penetration performance of polyurea/steel composite plate. 相似文献
188.
针对运载火箭伺服机构故障,提出一种基于扩展多模型自适应估计的故障检测与诊断算法。建立考虑伺服机构故障的运载火箭姿态动力学模型;将故障角度作为状态变量得到增广状态空间模型;利用扩展卡尔曼滤波器进行状态向量和故障参数的非线性估计,并基于传感器测量数据采用假设检验算法在线计算故障发生的概率;给出基于扩展多模型自适应估计的故障检测与诊断算法流程。仿真结果表明,该方法在无故障时可对伺服机构进行健康监测;在单台伺服机构故障下,可以及时准确判断出哪一台芯级伺服机构发生故障,并可准确估计出伺服机构故障下的发动机摆角角度。 相似文献
189.
We incorporate strategic customer waiting behavior in the classical economic order quantity (EOQ) setting. The seller determines not only the timing and quantities of the inventory replenishment, but also the selling prices over time. While similar ideas of market segmentation and intertemporal price discrimination can be carried over from the travel industries to other industries, inventory replenishment considerations common to retail outlets and supermarkets introduce additional features to the optimal pricing scheme. Specifically, our study provides concrete managerial recommendations that are against the conventional wisdom on “everyday low price” (EDLP) versus “high-low pricing” (Hi-Lo). We show that in the presence of inventory costs and strategic customers, Hi-Lo instead of EDLP is optimal when customers have homogeneous valuations. This result suggests that because of strategic customer behavior, the seller obtains a new source of flexibility—the ability to induce customers to wait—which always leads to a strictly positive increase of the seller's profit. Moreover, the optimal inventory policy may feature a dry period with zero inventory, but this period does not necessarily result in a loss of sales as customers strategically wait for the upcoming promotion. Furthermore, we derive the solution approach for the optimal policy under heterogeneous customer valuation setting. Under the optimal policy, the replenishments and price promotions are synchronized, and the seller adopts high selling prices when the inventory level is low and plans a discontinuous price discount at the replenishment point when inventory is the highest. 相似文献
190.
对于长径比较高的助推器来说,为了提高与芯级的连接可靠性,可采用超静定捆绑连接方式。这种捆绑连接方式增加了助推器动力学响应分析的难度。以超静定捆绑火箭助推器为研究对象,通过引入拉压双线性弹簧模拟捆绑连接装置,建立合理的动力学分析模型,对系统进行数值求解,获得径向冲击作用下助推器的动力学响应特性。通过与静定捆绑模型的对比,获得超静定捆绑助推器的广义位移、频谱和内力的响应,从而为工程应用提供一定的参考和理论支撑。 相似文献