全文获取类型
收费全文 | 333篇 |
免费 | 85篇 |
国内免费 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 13篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 45篇 |
2013年 | 31篇 |
2012年 | 34篇 |
2011年 | 28篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
排序方式: 共有437条查询结果,搜索用时 15 毫秒
401.
402.
利用对偶四元数的理论来分析航天器六自由度的相对运动,设计了一种考虑输入有界的姿轨一体化控制器。在介绍对偶数和对偶四元数的基础上推导六自由度相对运动的姿轨耦合模型;利用双曲正切函数绝对值小于1的特性来显式地构造有界控制器,分别设计两个相互耦合的自适应调节律来动态地改变控制器的输出,并基于李雅普诺夫稳定性理论严格证明了闭环系统的全局渐近稳定性;利用数学仿真实验来验证该控制器和控制力满足给定的约束条件,能够实现航天器六自由度相对运动的精确稳定控制,并且对模型参数不确定性和外界扰动具有鲁棒性。与其他方法相比,由该控制器计算得到的控制力矩器的收敛速度更快,输出的控制力矩和控制力的最大幅值更小,且消耗的能量也更少。 相似文献
403.
运用统计能量分析法解决高频声振问题的研究 总被引:3,自引:0,他引:3
为了得出统计能量分析法的适用范围和成功应用的关键因素,应用模态理论对系统的输入功率和耦合损耗因子进行了研究,挖掘了统计能量分析法中“统计”的更深层次的含义.通过对统计能量分析法原理的分析,提出增大系统的特征尺寸和系统阻尼、增大分析带宽和采用宽带激励均可提高统计能量分析的精度. 相似文献
404.
金梁 《国防科技大学学报》1991,13(3):1-9
本文研究了带挠性附件双自旋卫星的姿态稳定性问题。假定挠性双自旋卫星由无内部活动部件的半刚性平台、半刚性转子以及固连于平台的挠性附件构成,选择姿态角和模态坐标表示的相对能量函数为Liapunov 函数,建立了挠性双自旋卫星姿态稳定性判据。 相似文献
405.
Stephen Pampinella 《Small Wars & Insurgencies》2013,24(5):721-743
As US counterinsurgency campaigns draw to a close, doctrine for asymmetric warfare written during the War on Terror has come under heavy criticism. While many have argued that this shift to ‘winning hearts and minds’ is evidence that the United States is taking humanitarianism and nation-building seriously, others argue that a wide gap exists between US counterinsurgency doctrine and the protection of civilians afflicted by conflict. In this article, I show that the latter is true by comparing theories of instrumental and communicative action to US doctrine for operational design, stability operations, and counterinsurgency. I argue that these texts treat the people as an object to be manipulated for the achievement of pre-determined self-interested strategic goals rather than members of a community that jointly designs operations to fulfill shared objectives. However, US doctrine does contain communicative elements that, if prioritized, would better support humanitarian and state-building objectives otherwise subordinated in the War on Terror. 相似文献
406.
家庭教育投资行为决定着孩子的未来,文章通过459份问卷调查,从影响家庭投资行为的经济收入、教育投入、教育观念、教育方式、家长受教育年限、家庭子女受教育距离、子女的数量等因素进行统计分析,结果表明:家长受教育年限越长,家庭教育投资行为呈显著正相关,家庭中子女数量对家庭教育投资呈负影响。 相似文献
407.
将强度折减法引入强震作用下的海底隧道衬砌结构安全稳定性研究,利用FLAC3D软件建立了海底隧道-岩土体-海水相互作用的强度折减法数值模型,综合考虑海底隧道衬砌在强震作用下的位移、剪应变增量和塑性区变化,确定了海底隧道衬砌局部破坏的极限平衡状态和整体破坏的极限平衡状态,分析了海底隧道衬砌在强震作用下的破坏机理。结果表明:海底隧道衬砌在水平地震波的作用下,主要是围岩变形导致隧道衬砌破坏;隧道衬砌破坏位置发生在右侧侧墙中部,破坏形式为剪切破坏;隧道衬砌局部破坏的极限安全系数为1.47,整体破坏的极限安全系数为1.8,2种安全系数的极限状态可对应结构设计中的正常使用极限状态和承载力极限状态。研究成果可为海底隧道衬砌设计提供理论依据。 相似文献
408.
Stephen I. Schwartz 《The Nonproliferation Review》2013,20(2):205-208
This article offers a survey of risks that might arise for strategic stability (defined as a situation with a low probability of major-power war) with the reduction of US and Russian nuclear arsenals to “low numbers” (defined as 1,000 or fewer nuclear weapons on each side). These risks might include US anti-cities targeting strategies that are harmful to the credibility of extended deterrence; renewed European anxiety about a US-Russian condominium; greater vulnerability to Russian noncompliance with agreed obligations; incentives to adopt destabilizing “launch-on-warning” strategies; a potential stimulus to nuclear proliferation; perceptions of a US disengagement from extended deterrence; increased likelihood of non-nuclear arms competitions and conflicts; and controversial pressures on the UK and French nuclear forces. Observers in North Atlantic Treaty Organization (NATO) states who consider such risks significant have cited four possible measures that might help to contain them: sustained basing of US nonstrategic nuclear weapons in Europe; maintaining a balanced US strategic nuclear force posture; high-readiness means to reconstitute US nuclear forces; and enhanced US and allied non-nuclear military capabilities. These concrete measures might complement the consultations with the NATO allies that the United States would in all likelihood seek with respect to such important adjustments in its deterrence and defense posture. 相似文献
409.
410.
Dennis M. Gormley 《The Nonproliferation Review》2013,20(2):123-139
ABSTRACTThe dangers and risks of employing a Conventional Prompt Global Strike (CPGS) capability greatly exceed the benefits. More suitable, if less prompt, alternatives exist to deal with fleeting targets. Even a niche CPGS capability—consisting of approximately twenty systems—carries risks, to say nothing of proposals to develop hundreds or more. Most dangerously, CPGS could stir the pre-emption pot, particularly vis-à-vis states that correctly perceive to be within the gunsights of US CPGS weapons; other states, too, may feel emboldened to emulate this US precedent and undertake their own form of prompt, long-range strike capability. Compressed circumstances surrounding such a scenario could foster unwanted erratic behavior, including the misperception that the threatening missile carries a nuclear weapon. But the true Achilles's heel of the CPGS concept is the unprecedented demands it places on the intelligence community to provide decision makers with “exquisite” intelligence within an hour timeframe. Such compressed conditions leave decision makers with virtually no time to appraise the direct—and potentially unintended—consequences of their actions. 相似文献