首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   871篇
  免费   77篇
  国内免费   89篇
  2024年   1篇
  2023年   3篇
  2022年   2篇
  2021年   17篇
  2020年   8篇
  2019年   33篇
  2018年   31篇
  2017年   54篇
  2016年   55篇
  2015年   31篇
  2014年   71篇
  2013年   123篇
  2012年   41篇
  2011年   67篇
  2010年   44篇
  2009年   58篇
  2008年   49篇
  2007年   56篇
  2006年   73篇
  2005年   54篇
  2004年   37篇
  2003年   34篇
  2002年   23篇
  2001年   21篇
  2000年   10篇
  1999年   16篇
  1998年   6篇
  1997年   2篇
  1995年   4篇
  1994年   6篇
  1993年   4篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
排序方式: 共有1037条查询结果,搜索用时 859 毫秒
241.
Abstract

The rollback of Daesh’s territorial control during 2017 has (re-)established an area of limited statehood in large parts of Iraq that may endure for many years. The government of Iraq projects its authority into a large geographical and political space that it shares with a multitude of other state, non-state and hybrid actors, competing and collaborating to achieve advantageous security and political outcomes. This paper examines the heterarchy of actors in post-Daesh Iraq to develop a typology and start a critical discussion about post-Westphalian alternatives for security governance in Iraq during the coming period of reconstruction and reconciliation.  相似文献   
242.
The earlier work on the optimal design of the national security has focused on the opportunity cost of the draft in terms of foregone human capital formation. The current paper introduces the national security into the welfare analysis missing from the earlier work. This creates a trade-off between the private goods and the security as a public good in the social cost–benefit analysis. There are three major results. First, and arising from the intergenerational interaction, it is optimal to introduce a pay to the young generation when in duty even by resorting to a distortive tax. Second, when optimizing the size of the army, the optimal choice between the draft army and the professional army depends on the risk class of the country. A security gradient arises. Third, the choice is linked to the size and the quality of the reserve generated by the two approaches.  相似文献   
243.
International concern over nuclear terrorism has grown during the past few decades. This has driven a broad spectrum of efforts to strengthen nuclear security globally, including the widespread adoption of radiation-detection technology for border monitoring. Detection systems are now deployed at strategic locations for the purported purpose of detecting and deterring the smuggling of nuclear and radioactive materials. However, despite considerable investment in this area, few studies have examined how these programs are implemented or the operational challenges they face on a day-to-day basis. This article seeks to address this with a focus on radiation-detection efforts at maritime facilities. Utilizing practitioner interviews and a survey, this article identifies the factors that influence the planning and use of these systems in this fast-moving environment. The results clearly demonstrate that the implementation of these systems varies significantly across different national and organizational contexts, resulting in a fragmented global nuclear-detection architecture, which arguably undermines efforts to detect trafficked nuclear-threat materials. Greater consideration should therefore be given to developing international standards and guidance, designing and adopting tools to support key parts of the alarm assessment process, and broader sharing of good practice.  相似文献   
244.
Cyberspace is a new domain of operation, with its own characteristics. Cyber weapons differ qualitatively from kinetic ones: They generate effects by non-kinetic means through information, technology, and networks. Their properties, opportunities, and constraints are comparable to the qualitative difference between conventional and nuclear weapons. New weapons and their target sets in a new domain raise a series of unresolved policy challenges at the domestic, bilateral, and international levels about deterrence, attribution, and response. They also introduce new risks: uncertainty about unintended consequences, expectations of efficacy, and uncertainty about both the target’s and the international community’s response. Cyber operations offer considerable benefits for states to achieve strategic objectives both covertly and overtly. However, without a strategic framework to contain and possibly deter their use, make state and non-state behavior more predictable in the absence of reciprocal norms, and limit their impact, an environment where states face persistent attacks that nonetheless fall below the threshold of armed conflict presents a policy dilemma that reinforces collective insecurity.  相似文献   
245.
The past decade has seen substantial shifts in Swedish security policy and major change in the domestic debate about NATO. For the first time, all of the right-of-centre “alliance parties” are calling for a full NATO membership, and popular support for NATO has increased. Yet public opinion contains ambiguities and paradoxes that complicate the picture. At the same time as support for NATO has increased, the public is overwhelmingly for continued military non-alignment. Drawing on previous research, longitudinal data from national surveys, and other sources on defence and security issues, this article aims to increase our understanding of the development and change in Swedish public opinion on NATO. A key argument is that Erving Goffman’s theatre metaphor, combined with neo-institutional decoupling theory, to a large degree can help understand the public opinion paradox.  相似文献   
246.
A dynamic multi-stage decision-theoretic approach is introduced to establish the optimal offset and its incidence, the contract price arising from bargaining, and the scale of the acquisition. A new rationale is suggested for offsets in terms of their role as an insurance devise. Results are derived for the pricing of delivery contracts subject to offset claims and their national security implications. It is shown that the national security is strictly convex in the offset transaction. As to the incidence of the offset, the offset claim is shown to be capitalised in the delivery price. The bargaining price is shown to depend on the value of the product to be delivered for the national security, the relative negotiation power of the contracting partners and the social cost of public funds. The analysis highlights the expectation effects of offsets on the bargaining price and the scale of delivery. The results aid in explaining why offsets are widely used in procurement contracts for defence materiel. As they contribute to the national security, they should be allowed to survive and not be denied under competition laws.  相似文献   
247.
248.
Between 2014 and 2017, no less than 10 different non-governmental organizations (NGOs) conducted maritime Search and Rescue (SAR) operations off the coast of Libya. By rescuing over 100,000 migrants in three years, these NGOs became the largest provider of SAR in the Mediterranean. The theory of institutionalism suggests that organizations conducting similar activities are likely to converge in a process of mimetic isomorphism, deliberately imitating one another to increase their effectiveness and cope with uncertainty. These 10 SAR NGOs, however, developed two different rescue models: While some rescued migrants and disembarked them in Italian ports, others only simply assisted those in distress until the arrival of another ship transporting them to land. They also cooperated with Italian and European authorities to different degrees. Why did SAR NGOs imitated many elements of existing non-governmental rescue models, but discarded some others? This article argues that differences in material capabilities and organizational role conceptions are crucial to explain why newer SAR NGOs have imitated most but not all of their predecessors’ policies, engaging in a process of “selective emulation.”  相似文献   
249.
刘楝  孟宪民  李阳 《国防科技》2020,41(3):76-79,85
5G作为当今先进的通信技术,其广泛应用将给整个社会生产生活带来全新变革,相关技术和应用的安全问题,事关社会公共安全和军事利益安全,应纳入总体国家安全观视角下重点考量。本文主要梳理5G关键技术可能带来的网络安全风险,以及相关应用可能给网络监管带来的挑战,并从牢牢把控核心知识产权、综合构建安全保障体系、紧跟推进行业法律规范以及着力完善高效应急措施这四方面探讨相关的应对措施。  相似文献   
250.
《防务技术》2020,16(6):1106-1115
In order to study the instability propagation characteristics of the liquid kerosene rotating detonation wave (RDW), a series of experimental tests were carried out on the rotating detonation combustor (RDC) with air-heater. The fuel and oxidizer are room-temperature liquid kerosene and preheated oxygen-enriched air, respectively. The experimental tests keep the equivalence ratio of 0.81 and the oxygen mass fraction of 35% unchanged, and the total mass flow rate is maintained at about 1000 g/s, changing the total temperature of the oxygen-enriched air from 620 K to 860 K. Three different types of instability were observed in the experiments: temporal and spatial instability, mode transition and re-initiation. The interaction between RDW and supply plenum may be the main reason for the fluctuations of detonation wave velocity and pressure peaks with time. Moreover, the inconsistent mixing of fuel and oxidizer at different circumferential positions is related to RDW oscillate spatially. The phenomenon of single-double-single wave transition is analyzed. During the transition, the initial RDW weakens until disappears, and the compression wave strengthens until it becomes a new RDW and propagates steadily. The increased deflagration between the detonation products and the fresh gas layer caused by excessively high temperature is one of the reasons for the RDC quenching and re-initiation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号