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   1333篇
  免费   111篇
  国内免费   134篇
测绘学   326篇
大气科学   72篇
地球物理   129篇
地质学   358篇
海洋学   136篇
天文学   10篇
综合类   142篇
自然地理   405篇
  2024年   13篇
  2023年   22篇
  2022年   63篇
  2021年   50篇
  2020年   54篇
  2019年   48篇
  2018年   46篇
  2017年   59篇
  2016年   55篇
  2015年   48篇
  2014年   66篇
  2013年   96篇
  2012年   64篇
  2011年   72篇
  2010年   55篇
  2009年   57篇
  2008年   77篇
  2007年   78篇
  2006年   85篇
  2005年   77篇
  2004年   69篇
  2003年   62篇
  2002年   37篇
  2001年   37篇
  2000年   46篇
  1999年   27篇
  1998年   24篇
  1997年   15篇
  1996年   17篇
  1995年   13篇
  1994年   16篇
  1993年   10篇
  1992年   7篇
  1991年   2篇
  1990年   3篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1983年   1篇
  1979年   1篇
排序方式: 共有1578条查询结果,搜索用时 421 毫秒
301.
主要论述用计算机代替手工实现综合解译的过程。该过程归纳为:从专业领域获取知识组织成专业模型,再将其转变翻译成知识模型,然后转移到计算机内实现推理目标。重点论述从专业模型到知识模型的过渡和推理目标的实现。通过在河北、山西的实践,证明用计算机综合解释圈定找矿靶区是可行的  相似文献   
302.
303.
陈伟  胡伦积 《矿物学报》1990,10(2):180-185
本文对广东河台云西金矿的石英进行了拉曼光谱研究。结果表明,含金石英与不含金石英的拉曼光谱有着本质的差异。作者通过量子理论的研究,对其差异进行了剖析,发现这种差异与它们之间成分、组构、形成温度的差异紧密联系。因此,作者得出结论:石英的拉曼光谱可以用于评价其含金性。  相似文献   
304.
基于粗糙集理论,以指标集为基础,建立了底板破坏深度影响因素的知识表达系统,提出了规则提取原则,通过粗糙集决策规则的数据处理,得出获得各因素对底板破坏深度的影响顺序为:采深、煤层倾角、工作面斜长、采厚、底板抗破坏能力、工作面是否有切穿型断层或破碎带。由于底板抗破坏能力、工作面是否有切穿型断层或破碎带这些参数难以确定,采用其余4种影响因素建立BP神经网络的预测模型,并根据建立的模型预测肥城煤田的9101和9507工作面的底板破坏深度。通过与实测结果对比,证明该网络模型的计算结果比规程提供的经验公式计算结果更接近实际。  相似文献   
305.
李勋  赵声蓉  王勇  吴俞  李玉梅 《气象科技》2016,44(4):585-595
利用2000—2014年热带气旋(TC)最佳路径、最终分析资料和静止卫星红外云顶亮温(TBB)资料,对比分析了西北太平洋(WNP),以及南海(SCS)的迅速加强(RI),与非迅速加强(non-RI)TC样本的环境背景和TBB统计特征,其中non-RI样本细分为不同的强度变化率即:缓慢加强(SI),强度稳定、缓慢减弱和迅速减弱等。结果表明,相对于SI,WNP海域的RI样本处于海表温度较高、海洋上层热容量较大、最大可能强度较大、高层辐散较强、风垂直切变(VWS)较弱和高层纬向风(U200)偏东分量较大等环境背景条件下;SCS海域的RI样本较易发生在VWS较弱的环境背景条件下。此外,相对于non-RI,支持RI发展的有利条件还包括中低层相对湿度较大、高层环境温度较低等。RI样本通常具备的TBB特征为TC内核的对流云覆盖率较大、TBB平均值相对较小。采用K最近邻分类算法进行RI预报试验,交叉检验结果表明,该方法对RI样本有一定的识别预报能力,RI样本概括率达到74.2%,技巧评分达到0.717。  相似文献   
306.
In site investigation, the amount of observation data obtained for geotechnical property characterisation is often too sparse to obtain meaningful statistics and probability distributions of geotechnical properties. To address this problem, a Bayesian equivalent sample method was recently developed. This paper aims to generalize the Bayesian equivalent sample method to various geotechnical properties, when measured by different direct or indirect test procedures, and to implement the generalized method in Excel by developing an Excel VBA program called Bayesian Equivalent Sample Toolkit (BEST). The BEST program makes it possible for practitioners to apply the Bayesian equivalent sample method without being compromised by sophisticated algorithms in probability, statistics and simulation. The program is demonstrated and validated through examples of soil and rock property characterisations.  相似文献   
307.
Culture provides an important perspective to understand society. It is one of the key factors that impact how people behave themselves, interact with one another, view the world; what they believe and value. Therefore, a good understanding of public disaster awareness and disaster coping is impossible without taking their culture context into consideration. Since the 1960s, cultural dimension in disaster issues and/or disaster reduction practices has been attracting increasingly attention; many empirical or theoretical explorations have been reported. This review aims to give an overview of research progresses on how culture impacts public awareness and coping of disasters, and analyze the corresponding implications for disaster research and disaster reduction practice. This review summarizes that: ①There is unanimous consensus on public awareness and coping of disaster, which are affected by their culture context. While the knowledge about the ways and degree of impact is still limited, further research is warranted. In addition, more systematic and in-depth studies conducted from cross-cultural perspectives are needed to design to further explore the origins of variance in public disaster awareness and coping, and to what extent from cultural differences. ②Research on public awareness of disaster, emergency response and recovery indicated that culture might have double-side impacts on disaster management—sometimes cultural factors such as value, norm, custom and belief might lead to people more vulnerable than the others, even could be the root causes, but they could also be the source of people’s resilience to disaster in some cases. How to identify those positive and negative impacts, then develop cultural-oriented disaster management policy is a challenge issue, which need special attention. ③There is an increasing acknowledgement that local knowledge and disaster subculture could play an important role in public disaster coping, while the lacking of the awareness of the value of local knowledge, the change of lifestyle, and the impact from external culture pose a threat to the inheritance of some local, traditional disaster coping strategies. So exploring how to conserve, protect, identify, document them, then combine them with modern science and technology should and will be the focus of relevant studies. On the bases of these summarizations, in terms of cultural dimension of natural disaster research in China, systematic and in-depth studies are needed to explore how Chinese culture affects public disaster awareness and coping, what cultural resources can be used in disaster (risk) reduction and for building and enhancing disaster resilience, and how to use them.  相似文献   
308.
This article draws on a process of collaborative research associated with the brown crab fishery in Devon, UK. It charts the mobilisation of knowledge in the struggle over ‘ownership’ and influence in the coastal zone. Using methods from the social and behavioural sciences the article outlines different perspectives on a number of key contestations across the domains of sustainable use and a new conservation agenda ushered in by the introduction of European and UK national marine spatial planning tools for the South Coast of England. Along with their introduction and the ‘opening up’ of marine space, new opportunities emerge for fishers, who, by building alliances with scientists and managers, and by drawing upon the methods and materials of science, are better able to negotiate for their own interests over access and control of marine resources. The paper concludes by outlining the emergence of a new type of scientifically literate fisherman, a ‘political actor with a new crew’, better able to implement collective actions towards the sustainable use of brown crab resources.  相似文献   
309.
选取哈尔滨市周边地区作为试验区,基于资源三号卫星影像和历史DLG信息,综合利用栅格计算方法和矢量套合比较方法进行变化发现,按照地物类别特性和指标构建变化检测知识库来消除大部分伪变化,辅助解译人员更新要素,为以后的常态性更新提供参考。  相似文献   
310.
灾害遥感研究与应用中积累的判读知识是灾害应急中灾情信息快速、准确提取的重要依据,为了重复利用专家所掌握的不可多得的判读知识,需要通过知识库将其存储管理起来,以实现共享和利用。本文采用面向对象和模糊加权产生式规则的知识表达方法,研制了灾害遥感判读知识库,实现了知识获取、管理与推理,为判读人员提供了学习灾害判读知识和灾害应急应用的平台,对自动化和智能化的灾害遥感信息提取研究将起到推动作用。  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