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   15篇
  免费   5篇
  国内免费   7篇
大气科学   7篇
地球物理   3篇
地质学   12篇
天文学   2篇
自然地理   3篇
  2023年   1篇
  2021年   3篇
  2017年   1篇
  2016年   1篇
  2015年   3篇
  2013年   1篇
  2010年   2篇
  2009年   1篇
  2008年   1篇
  2006年   2篇
  2005年   1篇
  2003年   1篇
  2000年   1篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1989年   1篇
  1988年   1篇
排序方式: 共有27条查询结果,搜索用时 15 毫秒
1.
房营光  曹洪 《岩土力学》2003,24(5):729-732
由拉格朗日方程导出地基 结构系统地震响应分析的动力方程,利用突变模型分析了系统对地震响应的复杂过程,并分析了振幅响应的跳跃现象和“路径”效应等非线性动力特性,得出了有意义的结论。分析结果对地基 结构系统的参数设计有一定的参考价值。  相似文献   
2.
人造气液包裹体方法及其在研究热液性质中的应用   总被引:3,自引:0,他引:3       下载免费PDF全文
张毅刚 《地质科学》1992,(2):141-148
人造气液包裹体方法在研究热液的物理化学性质方面较传统方法简便、易行。它可用于研究热液的等容线、不混溶性质及矿物在热液中的溶解度。本文解释了人造气液包裹体的合成方法和人造气液包裹体方法的原理,分述了应用此方法研究热液所取得的最新成果。此法不仅能用于研究热液的性质,也能用于其它方面的研究,具有广阔的前景。  相似文献   
3.
东海陆架盆地伸展率和压缩率及构造跃迁   总被引:1,自引:0,他引:1       下载免费PDF全文
东海陆架盆地位于欧亚板块的东南缘和西太平洋活动大陆边缘,本文选取了东海陆架盆地主要凹陷的17条地震剖面,采用平衡剖面技术,计算了主要凹陷新生代不同演化阶段的伸展率和压缩率。分析表明,东海陆架盆地构造演化总体由西向东跃迁。晚白垩世至晚古新世东海陆架盆地裂陷中心在西部坳陷带,始新世东迁至东部坳陷带,上新世东迁至东海陆架盆地东侧的冲绳海槽盆地。古新世中后期东海陆架盆地西部坳陷带北侧昆山凹陷反转;中新世东部坳陷带的西湖凹陷反转。东海陆架盆地西部坳陷带与东部坳陷带构造演化不同,证明了东海陆架盆地的东西分带。西部坳陷带北部的长江坳陷和南部的台北坳陷构造演化不同,东部坳陷带北部的西湖凹陷和南部的钓北凹陷构造演化不同,证明了东海陆架盆地的南北分块。  相似文献   
4.
Gravity modelling was carried out along five profiles that traverse the Eastern Cape Province of South Africa in order to determine the depositional surface and isochore thickness of the Ecca sediments.Gravity models of the subsurface rock density reveal that the Ecca Group has a maximum vertical thickness of about 3215 ± 160 m.The maximum depositional surface(elevation)above sea level for the Ecca sediments is about 500 m,whilst the depth below sea level reaches about10000 m.Correlation of the isochore thickness maps with the depositional surfaces shows that the sediments in the basement highs were subsided,deformed,eroded and deposited in the basement lows.The basement highs served as the source area(s) for the sediments in the basement lows,thus basement highs are characterized with thin sediment cover whilst the lows have thick sediment cover.  相似文献   
5.
Abstract Effects of post-entrapment fluid-inclusion modification are examined with reference to retrogression-related quartz veins from the Caledonian, Øse Thrust, northern Norway. The inclusions occur in secondary trails, and contain high-density hypersaline aqueous fluids. On morphological characteristics, they are subdivided into, Type A: elongate, ellipsoidal and/or irregular inclusions, and Type B: more equant, regular, and/or negative crystal form. With reference to previous research on post-entrapment modification of inclusions in quartz it is proposed that Type A inclusions experienced little or no post-entrapment modification, whereas Type B inclusions show features characteristic of post-entrapment permanent inelastic stretching and/or leakage. This produces increased homogenization temperatures ( T h), associated with increased inclusion volume and lowering of density, whilst maintaining constant salinity. The similarity of data for degree of fill and salinity between Type A and Type B inclusions indicates that Type B inclusions have primarily modified by stretch rather than leakage. However, the spread towards slightly larger volume of vapour in Type B inclusions suggests that some leakage has also occurred. Because stretched and/or partially leaked inclusions have increased T h, isochore projections significantly underestimate trapping pressure ( P t) relative to unmodified inclusions. Therefore, recognition of post-entrapment inclusion modification due to overpressure is crucial to avoid misinterpretation of data, but has considerable potential for constraining the detail of P-T trajectories of individual rocks. On this basis, rocks from the Øse Thrust zone, north Norway, are shown to have experienced rapid uplift on a 'clockwise' P-T-t path during the final stages of Caledonian (Scandian) orogenesis.  相似文献   
6.
1991年江淮早梅及其与过赤道气流异常的关系   总被引:3,自引:0,他引:3       下载免费PDF全文
讨论了1991年江淮早梅现象及其形成机制。结果表明:5月第4候西太平洋副热带高压脊线出现第一次北跳,夏季风影响到江南,江淮地区入梅,比常年早二十多天;这与120—130°E间异常地出现较强的过赤道气流有关。  相似文献   
7.
Acadian (Late Silurian to Early Devonian) metamorphism in the Central Maine Terrane (CMT) in central Massachusetts is characterized by an early low-P, high-T (Buchan-type) metamorphism followed by thickening at high temperature (>650d? C) and then by cooling to 100-200d? C below peak recorded temperatures before eventual unroofing. Mineralogical and textural evidence for this path includes sillimanite pseudomorphs after early andalusite, abundant cordierite in pelitic lithologies, replacement of low-P cordierite-bearing assemblages by high-P garnet-bearing assemblages, and recrystallization of mylonites associated with late shear zones to form lower-T and higher-P assemblages. Peak conditions in the highest grade rocks were 685-780d? C and 5-6 kbar; the cooling path passed through 550d? C at about 6.5 kbar. The well-constrained P-T path documented from geological and mineralogical evidence for the CMT offers an unusual opportunity to examine characteristics of fluid inclusions that have experienced a long-lived metamorphic event spanning a broad range of P-T conditions. Fluid inclusion data from the CMT document a range of fluid compositions (CO2-rich, mixed CO2-N2-rich, N2-rich and H2O-rich) and densities during metamorphism. Densities of CO2 fluid inclusions range from 0.20 to 1.03 g cm-3. Medium-density CO2 fluid inclusions are contained in quartz inclusions within garnets in partial melt leucosomes, and in quartz grains within migmatites. Fluid inclusions within the quartz inclusions indicate trapping conditions of 650-700d? C at pressures below 5 kbar. Other CO2 fluid inclusions from matrix quartz yield isochores which pass through 700d? C and 5.2 kbar. The highest density inclusions associated with rocks containing the late high-P assemblages have isochores which pass below the estimated P-T conditions for recrystallization of the mylonite. Fluid inclusion evidence suggests an early low-P heating event, followed by thickening at high temperature, and then by nearly isobaric cooling to about 500d? C with later decompression. This interpretation is also consistent with previously published petrological models and supports an anticlockwise P-T path for the CMT of south-central Massachusetts.  相似文献   
8.
海温和极冰对副热带高压季节性北跳影响的数值模拟   总被引:24,自引:12,他引:12  
道德以南海区域平均的候平均OLR值下降至235W/m,同时纬向风由东转成西为定义标准确定南海季风从1979到1994年间爆发的平均日期是5月第4候,然后对16年的OLR场,风场及θX场的时段叠加合成图进行了分析,认为南海夏季风的建立是南海-西太平洋系统所造成。  相似文献   
9.
China's policy on ecological compensation (eco-compensation) in watershed eco-systems is of economic,social and environmental significance for China's ecological gov-ernance and protection of natural areas.It involves balancing the interests of regional stakeholders,coordinating the development of regional environments and establishing effec-tive cooperation models,making it a classic topic for geographical research.This study in-troduces the concept of institutional "stickiness" to the theory of politics of scale to analyze the features and mechanisms of the game behavior of government entities in the process of im-plementing watershed eco-compensation in the Xin'an River Basin.Our results show the following:government entities at various levels,including the central,provincial and municipal governments,experienced the three stages of game strategy of competition,cooperation and"coopetition";building a government community of shared interests can promote watershed eco-compensation,and "appropriate intervention" by the central govemment is key to achieving inter-provincial watershed eco-compensation;there was clear institutional stickiness during the transition from a "vertical" model of watershed eco-compensation to a "vertical-horizontal"model,with government entities using policy innovations and social participation to limit and reduce stickiness so as to reshape the watershed eco-compensation system;scalar jumping is the core mechanism that promoted eco-compensation in the study basin,and government entities shaped the discourse on watershed eco-compensation by redistributing powers and capital and creating informal constraints,which promoted the transformation of eco-compensation from a "strong state-weak society" structural model,to a "strong state-strong society" model in the Xin'an River Basin.These results can provide theoretical support for the construction of inter-regional watershed eco-compensation mechanisms,pro-vide a scientific basis for the rational evaluation and guidance of watershed eco-compensation practices,and promote the coordinated and sustainable socioeconomic development of watersheds.  相似文献   
10.
In the Philippines, a Catholic social movement for local development and broad structural transformation, referred to as Basic Ecclesial Communities, offers a counter‐narrative to state development. Predicated on the power of networked local groups, the Diocese of San Carlos has taken the original concept and rescaled it, operating a variety of social‐action programmes at the diocese level. The focus of this paper is a unique partnership between the diocese and the Armed Forces of the Philippines, which has produced a number of measurable positive changes in under‐serviced areas. We remain uncertain, however, about the extent to which the church is cooperating with, or being co‐opted by, the military as it enters into partnership, and many members of the clergy share our scepticism. In this paper we draw upon Gramsci's concept of passive revolution (1971) as a means to conceptualize both the efforts of the church to reform society from within, and the reaffirmation of the hegemonic discourse that seems inevitable.  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