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排序方式: 共有479条查询结果,搜索用时 15 毫秒
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在相对运动平台的点对点通信中,天线如何快速、准确地进行跟踪对准是接收高质量通信信号的保证.针对于动态点对点通信中定向天线对准难的问题,提出了一种基于坐标跟踪法和信号跟踪法的联合天线跟踪控制法,并对此方法进行了系统的软、硬件设计.通过精度分析和试验得出该方法对准精度高,系统易于实现,能够满足微波通信天线对准工程实现中的快与准的要求. 相似文献
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对金字塔构型单框架控制力矩陀螺(SGCMG)的失效特性进行分析。结合SGCMG部分失效的特点,构建运用Legendre伪谱法的重规划姿态机动路径求解方法。考虑SGCMG失效情况的不可预测性,设计自适应操纵律,该操纵律可以根据指令力矩与输出力矩的偏差对SGCMG的失效情况进行诊断,从而调节操纵律的内部参数,实现失效情况操纵律的自适应调节。仿真结果表明,采用姿态机动路径重规划算法与自适应操纵律,在控制力矩陀螺部分失效的情况下,仍可以实现空间站的大角度姿态机动。姿态机动方法可以有效应对空间站大角度姿态机动过程中可能出现的SGCMG部分失效情况,从而提高空间站姿态机动任务的安全性与可靠性。 相似文献
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Leo J. Blanken 《Defence and Peace Economics》2013,24(3):317-334
We develop a model of military technology competition among states. States can choose to introduce new military technology, mimic rivals’ level of technology, or withdraw from the contest. States can choose to implement any level of technology within their current feasible technologies. We find that states with significant technological leads should sometimes withhold new technologies, only strategically releasing them to trump rivals’ efforts. We develop the model by refining Admiral Jackie Fisher’s roughly articulated concept of ‘plunging’. We then use this refined argument to reanalyze the case of naval rivalries among European powers between the Crimean War and the First World War. Finally, we conclude by discussing the model’s implications for current US military force structure planning. 相似文献
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HÅKAN FRIMAN 《African Security Review》2013,22(3):62-77
The armed conflict in the DRC has been characterised by appalling, widespread and systematic human rights violations. It varies from civil war to a war between national armies. Much of the conflict falls between these two categories due to the involvement of foreign troops in civil strife, as well as foreign rebel groups fighting their home government's troops but on Congolese soil. The most pressing need is to cease hostilities and address the humanitarian situation in the country. Questions of justice and accountability, and issues relating to the rule of law will have to be addressed soon in order to achieve a durable peace in the country and in the region. Since there are links between different conflicts in the region, a broader solution should preferably be found. However, this would further complicate an already difficult proposition. Efforts limited to the DRC would be more feasible and could lead to similar measures in other conflict ridden countries in the region. This essay therefore discusses the available processes for justice. 相似文献
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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
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In the aftermath of September 11, 2001 and Hurricane Katrina, the United States government has spent tens of billions of dollars to improve the nation's ability to respond to a natural disaster or terrorist attack, but the emphasis on immediate first response has left many long-term environmental, political, and technological challenges unaddressed. Although a dirty bomb attack is unlikely to yield the same amount of physical devastation and death as caused by Katrina or a nuclear weapon, the social, psychological, and economic impact would be enormous. At present, however, the United States lacks the technology necessary to decontaminate a large, densely populated urban area under time, political, and economic constraints. This article reviews past cleanup experiences and current decontamination capabilities to consider the long-term implications of a dirty bomb, identifies weaknesses in America's existing response capabilities, notes possible areas of political friction, and considers the implications of the failure to adequately prepare. Having the appropriate decontamination techniques established and long-term plans in place before an incident occurs will significantly improve the government's ability to protect public and environmental security, establish a viable decontamination strategy, allow residents to return to their homes, and get the local economy back on its feet. 相似文献