全文获取类型
收费全文 | 288篇 |
免费 | 87篇 |
国内免费 | 15篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 4篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 22篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 18篇 |
2008年 | 31篇 |
2007年 | 16篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 25篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
排序方式: 共有390条查询结果,搜索用时 31 毫秒
241.
242.
以胡锦涛为总书记的党中央提出的科学发展观对我军现代化建设跨越式发展有着重大的推动作用。坚持全面发展观,可以加强我军现代化建设跨越式发展的宏观规划;坚持协调发展观,可以科学处理我军现代化建设跨越式发展中的内外关系;坚持可持续发展观,可以建立健全我军现代化建设跨越式发展的动力机制;坚持以人为本的发展观,可以快速提升军事人才的综合素质。 相似文献
243.
利用通信信号的循环平稳特性,在循环累积量域内提出了一种基于高阶循环累积量的载波相位估计算法,该算法通过提取观测样本的循环累积量特征并对其进行归一化,有效消除了信号能量、时延和成形脉冲参数对算法性能的影响。理论分析和仿真结果均证明了算法的正确性和有效性。 相似文献
244.
毫米波合成孔径雷达(SAR:Synthetic Aperture Radar)成像技术是雷达技术、现代电子技术和数字信号处理技术的有机结合,使系统雷达的功能发生了质的飞跃.随着SAR成像处理技术的发展,其成像质量不断提高,成为当今高科技条件下一种不可取代的探测、侦察手段,在军事、经济和科学研究等方面都有重大价值和广泛应用前景.主要介绍了毫米波成像雷达与微波雷达相比具有的技术特点,较详细地讨论了毫米波合成孔径雷达的成像原理技术. 相似文献
245.
应用一维流体仿真软件FLOWMASTER2,对坦克传动装置润滑系统的流动进行了模拟,提出了基于FLOWMASTER2软件的传动装置润滑系统的稳态流动仿真模型,并对某型坦克液力机械传动装置润滑系统的流动进行了仿真,预测了润滑系统的流量、流速和压力分布。该研究为坦克及其它车用传动装置润滑系统的流动性能提供了一种有效的理论分析手段和仿真方法。 相似文献
246.
Feature extraction is an important part of signal processing, which is significant for signal detection, classification, and recognition. The nonlinear dynamic analysis method can extract the nonlinear characteristics of signals and is widely used in different fields. Reverse dispersion entropy (RDE) proposed by us recently, as a nonlinear dynamic analysis method, has the advantages of fast computing speed and strong anti-noise ability, which is more suitable for measuring the complexity of signal than traditional permutation entropy (PE) and dispersion entropy (DE). Empirical wavelet transform (EWT), based on the theory of wavelet analysis, can decompose a complex non-stationary signal into a number of empirical wavelet functions (EWFs) with compact support set spectrum, which has better decomposition performance than empirical mode decomposition (EMD) and its improved algorithms. Considering the advantages of RDE and EWT, on the one hand, we introduce EWT into the field of underwater acoustic signal processing and fault diagnosis to improve the signal decomposition accuracy; on the other hand, we use RDE as the features of EWFs to improve the signal separability and stability. Finally, we propose a novel signal feature extraction technology based on EWT and RDE in this paper. Experimental results show that the proposed feature extraction technology can effectively extract the complexity features of actual signals. Moreover, it also has higher distinguishing ability for different types of signals than five latest feature extraction technologies. 相似文献
247.
Hong-bin Xie Hui-ya Yang Jian Yu Ming-yu Gao Jian-dong Shou You-tong Fang Jia-bin Liu Hong-tao Wang 《防务技术》2021,17(2):429-439
Electromagnetic railgun attracts more and more attention due to its advantage in speed,cost,and obscurity.It is found that the rail should withstand huge mechanical and thermal shocks during the launching operation.The forms of rail failure are accompanied by gouge,grooving,transition,and arc ablation,etc.The service life of the rail has become a bottleneck restricting the development of elec-tromagnetic railgun technology.A series of researches are carried out to solve rail failure,including analysing the failure mechanism and using various advanced rail materials.This paper provides a comprehensive review of rail materials,including material composition,preparation,microstructure,and properties.We begin from a short background of the requirement of the rail material.Then a detailed investigation of rail materials is described,and the performances of those materials are introduced.Finally,further development prospect of rail material is discussed. 相似文献
248.
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
249.
在线性分辨分析(LDA)基础上,通过遗传算法寻找Fisher准则下最优的线性映射中心和相应的最优映射,使不同模式在特征空间内具有最大的可分离性,并将该算法用于雷达目标一维距离像特征提取与识别中。实验表明,和原算法相比,新算法在特征提取性能和目标正确识别率上有较大提高,说明了算法的有效性。 相似文献
250.
美国西点军校以其在人才培养方面的巨大成就而举世闻名。“严格”、“精心”和“气派”的政治学课程的开发和设计,在一定程度上体现了西点军校的教学目标和要求。它不仅为以政治学为主攻方向的学员打下坚实的理论基础,而且对学员的政治思想观念产生积极的影响,使关于美国政府、美国政治制度、美国政治价值观的“优越性”的教育导向潜移默化在政治知识的学习过程之中,从而达到为美国的全球战略服务之目的。 相似文献