全文获取类型
收费全文 | 260篇 |
免费 | 101篇 |
国内免费 | 11篇 |
出版年
2024年 | 1篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 1篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 13篇 |
2010年 | 20篇 |
2009年 | 28篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 31篇 |
1998年 | 26篇 |
1997年 | 13篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1982年 | 2篇 |
排序方式: 共有372条查询结果,搜索用时 13 毫秒
191.
The test shell without projectile belt is widely used in the teaching, inspection and maintenance of modern automatic naval guns. In order to ensure the normal work of each mechanism, it is very important to design the buffer and limit of the test shell during the process of entering the bore. Taking a certain type of medium caliber naval gun as the research object, the design of colloidal fluid damper and cartridge lock was proposed to ensure the reliability of entering the bore and closing the breechblock. By combining the simulation methods of computational fluid dynamics (CFD) and multibody system dy-namic (MBD), it was analyzed whether the structural design can meet the engineering requirements. The research results show that the colloidal fluid damper can dissipate a large amount of kinetic energy of the shell, and the cartridge lock can limit the rebound movement. The combination of the two ensures the smooth process of closing the breechblock. The research provides a design method for the process of the test shell entering the bore, and provides theoretical support for the feasibility of the method. 相似文献
192.
Su-wei Wang Xiu-duo Song Zong-kai Wu Lei Xiao Guang-pu Zhang Yu-bing Hu Ga-zi Hao Wei Jiang Feng-qi Zhao 《防务技术》2021,17(6):1954-1966
The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base (CMDB) propellant. Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process. To improve the accuracy of the simulation results, material parameters and model structure were corrected based on actual conditions, and adaptive grid technology was applied in the local mesh refinement. In addition, the rheological behavior, motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps, rotational rates and temperatures of two rollers. The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet. Compared with the gap, the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging. Meanwhile, under the synergistic effect of contact heat transfer as well as convective heat exchange, heat accumulated near the outlet and diffused along the reflux movement, which led to the countercurrent heat dissipation behavior of CMDB propellant slurry. The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored, which provided theoretical guidance and reference data for the optimization of calendering process conditions. Based on the simulation results, the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle. 相似文献
193.
本文论述了用单球法测量大直径锯齿形螺纹中径的原理与方法,具体介绍了为实现这种方法而设计的检测装置。对这个装置进行了精度标定和测试,实验表明,该测量仪器使用方便,精度较高,具有较强的实用性。 相似文献
194.
本文分析了高空羽流流场的特性,论述了DSMC方法的原理以及涉及到的关键技术,应用DSMC方法数值求解了喷管出口附近及倒流区流场。仿真结果表明DSMC方法能够精确描述这一区域的流场特性。 相似文献
195.
建立了多部雷达情况下的系统误差观测模型,分析了系统的可观测度,得出可观测度不一定随观测数据的增多而增强的结论。在此基础上,通过数据筛选的方法,可以获得一个使系统可观测度增大的观测子集,用于误差估计。实验结果表明,使用本文的方法,可确保估计算法的有效性 相似文献
196.
本文对有泰氟隆烧蚀的化学非平衡粘性激波层流场进行了数值模拟。应用空间推进与总体迭代相结合的求解方法,采用19组元、29种反应的空气—泰氟隆化学反应系统,对化学非平衡粘性激波层流场与泰氟隆壁面烧蚀传热过程进行耦合求解,研究了平衡催化壁和非催化壁条件对粘性激波层烧蚀流场的影响。 相似文献
197.
测量船中心机实时监控专家系统应用于测量船中心机系统执行海上测量任务的时节,旨在提高整个系统的实时性和可靠性。本文围绕实时专家系统的时序性、时变性、时效性等特征,从系统设计与实现两个方面讨论建造该专家系统的一些关键技术。 相似文献
198.
在单语语料的使用上,统计机器翻译可通过利用语言模型提高性能,而神经机器翻译很难通过这种方法有效利用单语语料.针对此问题,文中提出基于句子级双语评估替补(BLEU)指标挑选数据的半监督神经网络翻译模型.分别利用统计机器翻译和神经机器翻译模型对无标注数据生成候选翻译,然后通过句子级BLEU指标挑选单语候选翻译,加入到有标注的数据集中进行半监督联合训练.实验表明,文中方法能高效利用无标注的单语语料,在NIST汉英翻译任务上,相比仅使用精标的有标注数据单系统,文中方法BLEU值有所提升. 相似文献
199.
强健的体魄是军人进行军事斗争的物质基础.但由于受多种因素的影响,军校学员的实际能力和身心状况与未来岗位的需求和自身的长远发展还存在着一定差距,更与高素质创新型军事人才的标准相距甚远.为了更好地推广和开展适合军校学员特点的体育教育,必须全面深化军校体育改革,提高教学质量.针对当前军校体育教学存在的问题,论述了改革军体教学的方式方法,以达到全面体育教育的目标,以及军校体育教学如何实现军队特色与高等教育之间的完美结合. 相似文献
200.
A single machine sequencing problem is considered in which there are ready-time and due-date constraints on jobs and vacation constraints on the machine. Each vacation has fixed starting and finish time and no preemption is allowed for the jobs. The objective is to minimize maximum lateness. An intriguing feature of this formulation is that it allows sequencing in disconnected time windows. A relaxation of the problem is obtained by modeling the vacations as a set of jobs with flexible ready-times and artificial due-dates and a branch and bound algorithm is developed for the problem. In the algorithm, the search is not only guided by the bounds but also by a careful manipulation of the artificial due-dates. Consequently; while searching in the relaxed solution space, solutions of the original problem are implicitly enumerated. Computational results indicate that the algorithm can satisfactorily solve problems with multiple vacations. 相似文献