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   996篇
  免费   47篇
  国内免费   50篇
系统科学   19篇
丛书文集   24篇
教育与普及   26篇
理论与方法论   9篇
现状及发展   16篇
综合类   986篇
自然研究   13篇
  2024年   4篇
  2023年   16篇
  2022年   19篇
  2021年   21篇
  2020年   32篇
  2019年   26篇
  2018年   11篇
  2017年   33篇
  2016年   26篇
  2015年   39篇
  2014年   47篇
  2013年   43篇
  2012年   70篇
  2011年   79篇
  2010年   44篇
  2009年   59篇
  2008年   47篇
  2007年   69篇
  2006年   44篇
  2005年   53篇
  2004年   54篇
  2003年   38篇
  2002年   30篇
  2001年   18篇
  2000年   26篇
  1999年   21篇
  1998年   15篇
  1997年   18篇
  1996年   14篇
  1995年   13篇
  1994年   15篇
  1993年   14篇
  1992年   8篇
  1991年   7篇
  1990年   1篇
  1989年   8篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
排序方式: 共有1093条查询结果,搜索用时 93 毫秒
41.
探讨地学知识获取与融合方法,将领域知识转换为定量的模型约束条件或初始值,采用趋势面拟合及空间插值等方法进行农业气候资源空间分布曲面建模.基于所构建模型,利用1951 ~ 2002年间全国735个地面台站的气温纪录数据,考虑了气温与海拔高程、经度、纬度、地表复杂度等地形要素的综合影响构建了曲面模型,模拟1 km×1 km...  相似文献   
42.
改革开放30多年以来,中国的经济建设取得了令世人瞩目的成就,然而资源的枯竭、能源的利用率低下、生态环境日益恶化、人口剧增等等已成为当前亟待解决的问题。当前,能源消耗和环境污染主要有三大方面:工业、交通和建筑。因此在新的形势下建筑节能减排工作就显得尤为重要。文章通过对印度著名建筑设计大师查尔斯.柯里亚的代表作品—管式住宅进行分析,剖析其设计理念及手法,加深对管式生态建筑的理解,以唤起更多的人去关注生态建筑和建筑节能。  相似文献   
43.
全球气候博弈的实质是各国在承认地球资源和承载能力有限的前提下力图在未来世界能源、资源分配和温室气体排放空间的分配中获得尽可能大的份额。美国与中国的个案分析表明:气候公地的悲剧源于博弈主体对于自身短期利益的追求及对人类根本利益的忽视。具体说来,发达国家受制于自由民主制度放纵的内部博弈,而发展中国家则更多的受制于国际体系的无政府状态与不平等现状下外部博弈引发的安全需求。气候危机将人类带入困境的同时也加速了人类从工业文明迈向生态文明的进程。公地悲剧的出路在于强化国家在应对气候方面的作用;加强转型时期政策的系统性;以政治上的预防原则对应吉登斯悖论;国际社会对于责任认定的公平化。  相似文献   
44.
45.
在全球气候变化的背景下,特殊的气候条件引发的城市突发公共卫生事件不容忽视.城市规划是政府确保公共卫生安全的重要手段,从城市规划角度预防及控制气候变化带来的突发公共卫生事件并作出一定的规划响应,对于提升寒地城市居民健康水平具有重要意义.以寒地城市为例,分析了地域气候特征对突发公共卫生事件的影响,结合城乡人口空间分布、土地...  相似文献   
46.
This paper primarily aims to test a Pleistocene refuge-type scenario, as previously proposed for the gonyleptid Geraeocormobius sylvarum, a semi-deciduous forests dweller in subtropical Argentina, Brazil and Paraguay. Palaeodistributional models of this species were built using MaxEnt for two Last Glacial Maximum (LGM = 21,000 years ago) simulations – Community Climate System Model (CCSM) and Model for Interdisciplinary Research on Climate (MIROC) – and for 6000 years ago (?6k = HCO, the Holocene climatic optimum). Both LGM models retrieved a fragmented pattern. For CCSM, range was split into multiple, scattered fragments. MIROC resulted in very few patches, with a decided range reduction because of a strong humidity drop. Models for ?6k recovered a moderate range expansion. No past connection between the core area and the yungas was predicted. Analysis of variables importance showed that two precipitation predictors (bc18, precipitation warmest quarter; bc14, precipitation driest month) and two temperature predictors (bc7, temperature annual range; bc9, mean temperature driest quarter) scored as the most influencing overall. The Limiting Factor analysis recognized them as limiting too, in different parts of the species range. LGM palaeomodels of G. sylvarum are compatible with the refuge hypothesis invoked in previous molecular analyses, to explain the high genetic diversity found in the core area. Additionally, the results reinforced the hypothesis of the recent anthropogenic origin of the yungas disjunct populations.  相似文献   
47.
Information on the freshwater fauna of the remote Arctic territories is very patchy, and most of the isolated islands of the Arctic Ocean remain absolutely unexplored. The pioneer data on the species composition of microcrustaceans of Shokalsky Island (northwest Siberia, Russia) is reported here. The initial three-year research revealed a total of 31 new for the area species of Cladocera and Copepoda, including new records for the whole of northwestern Siberia. Comparing the interannual differences in faunal composition, we suggested the hypothesis of the existence of a cryptic pool of species’ resting stages, which can invade the community in the event of favourable environmental conditions in the Arctic freshwaters. We also compiled all the available data from different parts of northern Siberia and compared them with the fauna of Shokalsky Island to analyse the connection between the diversity and distributional patterns of copepods and cladoceran species and the climate conditions of different territories.  相似文献   
48.
Temperature changes are known to affect the social and environmental determinants of health in various ways. Consequently, excess deaths as a result of extreme weather conditions may increase over the coming decades because of climate change. In this paper, the relationship between trends in mortality and trends in temperature change (as a proxy) is investigated using annual data and for specified (warm and cold) periods during the year in the UK. A thoughtful statistical analysis is implemented and a new stochastic, central mortality rate model is proposed. The new model encompasses the good features of the Lee and Carter (Journal of the American Statistical Association, 1992, 87: 659–671) model and its recent extensions, and for the very first time includes an exogenous factor which is a temperature‐related factor. The new model is shown to provide a significantly better‐fitting performance and more interpretable forecasts. An illustrative example of pricing a life insurance product is provided and discussed.  相似文献   
49.
激活员工创造力、凝聚新的发展动力是企业面临的紧迫任务.基于系统而权变的视角,以"语义感知-心理计量-行为强化"为理论主线,针对60个团队274名员工样本,运用跨层次分析考察了不同成就动机氛围下奖励(水平和结构)对创造力的影响.结果表明,精熟氛围、扁平型奖励结构正向影响突破式创造力;表现氛围、陡峭型奖励结构正向影响渐进式创造力:三项交互检验显示,在高精熟氛围及扁平型结构下,提高奖励水平能够更好地激活突破式创造力;而在高表现氛围和陡峭性结构下,提高奖励水平能够更好地激活渐进式创造力.研究揭示,成就动机氛围、奖励结构与创造力类型之间存在一种相对最优的匹配关系.蕴含的实践价值在于,企业应从执行角度在项目团队营造表现动机氛围并辅以竞争性激励结构,以提升渐进式创造力,快速获取局部竞争优势;但鉴于"渐进式创新有余,突破式创新不足"的企业创新格局,我们更应从战略视角在技术核心部门营造精熟氛围并辅以高位均衡的激励模式,以催生突破式创造力,赢得持久竞争优势.  相似文献   
50.
Vegetation cover change is critical for understanding impacts and responses of vegetation to climate change. A study found that vegetation in the regions between 45°N-70°N was increasing using normalized difference vegetation index( NDVI) from 1981 to 1991 ten years ago. The global vegetation growth has changed because of climate change in recent twelve years( 2001- 2012). After thorough analysis based on satellite data,it is found that it is evident that the global vegetation changed( NDVI) little,and it is increasing slightly in Northern hemisphere while it is decreasing slightly in Southern Hemisphere. For different latitudes,vegetation is increasing 0.17% every year from 60°N to 70 °N( R~2= 0.47,P 0.013),while the vegetation is decreasing 0.11% every year from 10°N to 10° S( R~2= 0.54,P 0.004). For different continents,the vegetation in South America is decreasing 0.16% every year( R~2= 0.78,P 0.0001) and it is increasing 0.05% every year in Asia( R~2= 0.28,P 0.072) and 0.25% every year in Oceania( R~2= 0.24,P 0.1). The analysis of global vegetation in different seasons indicates that spatial distribution of global temperature and water vapor will affect the spatial distribution of vegetation,in turn,the spatial distribution of vegetation will also regulate the global temperature and water vapor spatial distribution at large scale. The growth and distribution of vegetation are mainly caused by the orbit of the celestial bodies,and a big data model based on gravitational-magmatic change with the solar or the galactic system as its center is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatial-temporal variations of global vegetation and temperature at large scale. These findings promise a holistic understanding of the global climate change and potential underlying mechanisms.  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