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   2752篇
  免费   549篇
  国内免费   74篇
  2024年   1篇
  2023年   11篇
  2022年   25篇
  2021年   34篇
  2020年   33篇
  2019年   64篇
  2018年   59篇
  2017年   109篇
  2016年   114篇
  2015年   73篇
  2014年   231篇
  2013年   285篇
  2012年   188篇
  2011年   221篇
  2010年   191篇
  2009年   220篇
  2008年   166篇
  2007年   192篇
  2006年   171篇
  2005年   166篇
  2004年   151篇
  2003年   119篇
  2002年   82篇
  2001年   84篇
  2000年   47篇
  1999年   46篇
  1998年   32篇
  1997年   35篇
  1996年   33篇
  1995年   29篇
  1994年   38篇
  1993年   25篇
  1992年   25篇
  1991年   20篇
  1990年   28篇
  1989年   12篇
  1988年   11篇
  1987年   3篇
  1975年   1篇
排序方式: 共有3375条查询结果,搜索用时 0 毫秒
1.
针对复杂信号环境下雷达对抗情报侦察面临的信号分选问题,提出一种基于双站协同侦察的雷达信号分选新方法。根据不同位置雷达的脉冲信号到达两个侦察接收站的时间差不同进行信号分选。在满足误差的要求下,求解该方法的分选模糊区域,分析分选性能。调整布站,优化分选性能,提高分选准确性。理论分析和计算机仿真表明,该方法可以较好地解决制约雷达对抗情报获取中的信号分选瓶颈难题。  相似文献   
2.
离子束混合是一种材料改性和新材料研制的有效方法,本实验用Ar+离子束对Al-Mn多层薄膜在室温下进行轰击使其非晶化,并对样品电阻率随离子注入剂量及温度的变化关系进行原位测量.电阻温度系数TCR和TEM观测证实了样品离子束混合后电性能和结构发生改变生成了非晶相.  相似文献   
3.
Abstract

The concept of order is often neglected in the study of conflict – seemingly such a ‘disordering’ process. With the recent increase in the examination of rebel governance however, bringing order back into our understanding of rebel and insurgent groups has much to offer in exploring the everyday politics which connect authorities, rebel movements and the population itself, in a complex mass of intersubjective and power-based interactions and negotiations. Rebels both shape and are shaped by existing forms of order in complex and ongoing ways. This article explores how varying elements interact in the negotiation, framing and enforcement of order and develops an original analytical framework to examine the perpetual negotiations of rebel movements in their attempts to cement their control.  相似文献   
4.
提出了用变形的Fourier部分和来代替Fourier级数将输入数据光滑的一种新方法。该方法能稳定地解某些不适定的问题,如给定函数的近似,求函数微分的问题;Laplace方程Cauchy问题;时间逆向热传导方程的Cauchy问题等。  相似文献   
5.
在表格处理和光符识别软件中.歪斜图像校正是一项重要的预处理技术。针对文本和表格图像,本文提出了一种基于线条检测模型的高精度、快速的歪斜图像检测方法。  相似文献   
6.
A truly universal ban on anti-personnel mines cannot be realized without engagement of armed non-state actors and armed groups operating outside state control, including rebels and national liberation movements. Events after 9/11 have complicated engagement with organizations that can be classified as ‘terrorists’. Yet, the use of anti-personnel landmines itself can be viewed as an act of terrorism and African leaders have, on various occasions, classified the use of landmines and the presence of unexploded ordnance as engendering insecurity and a serious impediment to development. The success of a total ban ultimately depends upon ensuring that armed non-state actors act in accordance with international humanitarian law. The Geneva Call Deed of Commitment for Adherence to a Total Ban on Anti-Personnel Mines and for Cooperation in Mine Action (DoC) might be described as an alternative instrument to the Anti-Personnel Mine Ban Convention and can serve an important and impartial channel of communication with non-state actors. Already 18 armed groups in Africa have signed the Geneva Call DoC.  相似文献   
7.
I am afraid there is clear evidence that acts of gross misconduct have taken place. This is a shameful thing for the United Nations to have to say, and I am absolutely outraged by it.

—Kofi Annan, United Nations Secretary-General

Despite promulgating a comprehensive set of guidelines to deter UN personnel from committing acts of sexual misconduct, allegations of sexual exploitation and abuse have become widespread within United Nations peacekeeping missions. The policy of zero-tolerance for peacekeeper misconduct has not been matched by strong disciplinary measures, and crimes are often ignored and rarely punished: absentee fathers, rapists and murderers simply disappear back in their home countries. In countries where women and children rarely have the same economic resources, political rights and authority or control over their environment—or their bodies—they easily become prey for those in perceived positions of power and authority. By failing to hold those responsible to account, the UN may in fact be fuelling even greater discrimination and violence against women and children. In order to ensure those who are mandated to protect to do not become perpetrators of abuse, the UN must take a stronger stand against those who commit acts of sexual misconduct, and must ensure that victims see that their abuser is brought to justice and that reparation is offered. A recent report submitted by the Secretary-General's Special Envoy on Sexual Exploitation and Sexual Abuse makes a comprehensive set of recommendations to prevent, detect, and respond to these allegations. The aim of this essay is to highlight some of the main points of the Special Envoy's report, and to examine the practical challenges the UN and troop/police contributing countries will face when attempting to implement these recommendations.  相似文献   
8.
Abstract

A crisis is emerging in the Nile Basin, where some 300 million people in Egypt, Sudan, Ethiopia, Uganda, the Democratic Republic of Congo, Rwanda, Kenya, Tanzania and Burundi rely on the Nile directly or indirectly. Egypt and Sudan wish to preserve a regime based on treaties drawn up during the colonial era that allocated the vast majority of the Nile's water to them. Countries upstream are determined to challenge this. In 1999 the countries using the river formed the Nile Basin Initiative to try to resolve these differences. More than a decade of negotiations failed to break the impasse. In May Ethiopia, Kenya, Rwanda, Tanzania and Uganda decided to wait no longer and signed a new treaty, without the consent of Egypt and Sudan. The signatories have given the other Nile Basin countries one year to join the pact. For Egypt, which relies on the Nile for 95 per cent of its water, this is a question of life or death. Egypt has, in the past, indicated it will go to war if its share of the Nile is reduced. Talks continue, but the impasse is driving the region towards a crisis to which there is no easy resolution.  相似文献   
9.
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   
10.
In nuclear nonproliferation negotiations, many governments pursue multiple objectives, and changes in policy can occur rapidly—and often unexpectedly. For these reasons, understanding nonproliferation requires empathy and imagination rather than just historical fact. This article considers one teaching tool to encourage such insight—simulations—and demonstrates how teaching and scholarship can interact to improve our understanding of the complex decisions and negotiations involved in nuclear nonproliferation. The article consists of five parts: first, it explains the benefits of simulations as both a policy development tool in Washington and as a teaching tool in universities; second, it describes the pedagogical strategy of the Stanford University simulation program; third, it shows how the simulations have identified and highlighted theoretical and substantive insights that are often neglected in scholarly studies of nonproliferation; and fourth, it describes how students are tested to enhance the learning experience from the simulation. Fifth and finally, the article provides concluding observations about how using simulations in the classroom can help scholars develop insights that improve their understanding of real-world nuclear negotiation dynamics and outcomes.  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