全文获取类型
收费全文 | 6238篇 |
免费 | 158篇 |
国内免费 | 62篇 |
专业分类
6458篇 |
出版年
2025年 | 33篇 |
2024年 | 40篇 |
2023年 | 81篇 |
2022年 | 50篇 |
2021年 | 82篇 |
2020年 | 91篇 |
2019年 | 86篇 |
2018年 | 99篇 |
2017年 | 222篇 |
2016年 | 255篇 |
2015年 | 141篇 |
2014年 | 371篇 |
2013年 | 307篇 |
2012年 | 355篇 |
2011年 | 411篇 |
2010年 | 274篇 |
2009年 | 409篇 |
2008年 | 329篇 |
2007年 | 310篇 |
2006年 | 347篇 |
2005年 | 325篇 |
2004年 | 303篇 |
2003年 | 227篇 |
2002年 | 188篇 |
2001年 | 179篇 |
2000年 | 125篇 |
1999年 | 133篇 |
1998年 | 113篇 |
1997年 | 89篇 |
1996年 | 87篇 |
1995年 | 77篇 |
1994年 | 76篇 |
1993年 | 59篇 |
1992年 | 59篇 |
1991年 | 58篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1975年 | 1篇 |
排序方式: 共有6458条查询结果,搜索用时 0 毫秒
61.
裴建国 《中国人民武装警察部队学院学报》2013,(12):62-64
基于ZigBee的技术特点,提出一种新型无线火灾自动报警系统的设计要求和设计方案.该系统弥补了现有系统的不足,并具有良好的扩展性能,为火灾自动报警系统的设计和发展提供参考. 相似文献
62.
63.
This paper attempts to examine the effect of an anticipated foreign military threat on the steady‐state growth rate and the transitional behavior of the economy. The modeling strategy follows the Sandler and Hartley (1995) and Dunne et al. (2005) viewpoints to emphasize the role of national defense in affecting growth from the perspective of both the demand and the supply sides. We thus combine the public capital version of endogenous growth with a framework of competitive arms accumulation. It is found that the key factor determining the steady state and the transitional effects of a rise in the foreign military threat on the home weapon–capital ratio, the consumption–capital ratio, and the rate of economic growth, is the degree of relative risk aversion. 相似文献
64.
Peter Gastrow 《African Security Review》2013,22(1):39-43
This article discusses the validity of national security threats in Botswana and whether they justified the creation of the Directorate of Intelligence and Security Services (DISS), which has been controversial since its formation. Since its inception in 2008, the DISS has been accused of many human rights violations and politicisation. Without fully deliberating on the basis for its creation, some discourses have focused on the politicised operations without relation to what the DISS is supposed to be doing. The author works under the assumption that debates should be shaped by whether it was necessary to create the DISS, and, if so, how we can shape and steer debates on its oversight, management, reform and operations. This article argues that despite the politicisation of the DISS, Botswana's national security threats are both real and imagined; and that domestic threats to national security have moved from the conceptual ‘imagined’ category to the ‘real’. However, that in itself did not warrant the design and mandate of the DISS, and the article argues that it was external threats that really warranted the creation of a civilian intelligence agency. The article concludes that Botswana faces a plethora of external security threats – traditional and non-traditional – that warranted the creation and continuance of the DISS. 相似文献
65.
Chris M.A. Kwaja 《African Security Review》2013,22(2):153-161
This paper examines the rationale and centrality of private military and security companies (PMSCs) in humanitarian assistance operations in Sudan, asking why PMSCs are involved in humanitarian assistance operations in Sudan and what the principles underlying their activities are. To answer this question, the paper draws attention to the link between humanitarian crises and PMSC interventions. Where there is no meaningful alternative intervention, undergirded by humanitarian concerns that are also profit driven, PMSCs come in to provide the needed services. The protracted and complicated internal armed conflicts in Sudan, which have lasted for over two decades, have produced as many as 4,8 million internally displaced persons (IDPs) – the single largest number in the world. The kind of humanitarian assistance operations provided by PMSCs in Sudan have become critical to the provision of much-needed services which were inadequately provided by governmental authorities at both unilateral and multilateral levels. This paper argues that the humanitarian crises in Sudan created a regime that permits humanitarian assistance operations by both state and non-state actors. 相似文献
66.
The criticism of James, Solberg and Wolfson (JSW) (1999) by Oneal and Russett (OR) is not responsive to the methodologica] issues at stake. JSW argued that war is an endogenous feature of the world political and economic system. If its causes are to be measured, it must be as a structural equation in a simultaneous system. Wedded to the idea that “democracies never fight each other,” OR rely on a single equation to justify their view. JSW claim that such an equation may be an ad hoc reduced form with no causal implications unless the equation is explicitly identified as a structural equation. JSW expand the model to explain democracy and conflict as two endogenous variables. JSW do not claim to have discovered the true relationships between these variables by their minimal expansion of the structural relation. They do show that unless these (and other) variables are treated as part of a system, the results are unstable, contradictory, of minimal size and not a reliable guide to public policy. 相似文献
67.
The efforts of President Barack Obama and his administration to restore the United States as a driving force of multilateral arms control and nonproliferation negotiations are commendable, yet the lack of progress on such issues over the last eight years has ensured that U.S. policy has not kept pace with changes in the geostrategic environment and the evolving security agenda. Meanwhile, an alternative agenda has been articulated by non-Western countries. This article focuses on the arms control perspectives of Non-Aligned Movement states and others that have begun to embrace the idea of “disarmament as humanitarian action.” It explores this idea in the context of recent initiatives and argues that if the Obama administration wants to make progress on its arms control and nonproliferation priorities, it should consider a multifaceted approach that incorporates this emerging alternative agenda. 相似文献
68.
Lani Miyoshi Sanders Sharon M. DeLand Arian L. Pregenzer 《The Nonproliferation Review》2013,20(3):475-489
In his 2009 Prague speech and the 2010 Nuclear Posture Review, President Barack Obama committed the United States to take concrete steps toward nuclear disarmament while maintaining a safe, secure, and effective nuclear deterrent. There is an inherent tension between these two goals that is best addressed through improved integration of nuclear weapons objectives with nuclear arms control objectives. This article reviews historical examples of the interaction between the two sets of objectives, develops a framework for analyzing opportunities for future integration, and suggests specific ideas that could benefit the nuclear weapons enterprise as it undergoes transformation and that could make the future enterprise compatible with a variety of arms control futures. 相似文献
69.
针对舰艇武器布置问题的特点,提出了一种基于粒子群优化和分类器系统的协同优化算法,以粒子群优化进行优化计算,用分类器系统消除约束.计算实例表明,该算法能较好地实现优化计算,并能节省大量的计算时间. 相似文献
70.
高精度气压源的Fuzzy-PID控制研究 总被引:2,自引:0,他引:2
设计了Fuzzy-PID双模控制器并应用到高精度气源压力控制系统中.试验表明,单纯采用PID控制的高精度气源压力控制系统具有精度高的优点,但不适应系统参数的变化.Fuzzy-PID双模控制器具有响应速度快、稳态误差小、鲁棒性强的优点.通过试验比较了传统PID、Fuzzy控制和Fuzzy-PID双模控制3种控制策略,试验结果表明,Fuzzy-PID双模控制器综合了Fuzzy控制和PID控制的优点,适用于高精度气源压力控制系统. 相似文献