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   392篇
  免费   40篇
  国内免费   63篇
测绘学   2篇
大气科学   14篇
地球物理   240篇
地质学   181篇
海洋学   9篇
天文学   10篇
综合类   6篇
自然地理   33篇
  2023年   7篇
  2022年   5篇
  2021年   11篇
  2020年   9篇
  2019年   12篇
  2018年   6篇
  2017年   9篇
  2016年   7篇
  2015年   6篇
  2014年   12篇
  2013年   8篇
  2012年   8篇
  2011年   13篇
  2010年   10篇
  2009年   31篇
  2008年   54篇
  2007年   24篇
  2006年   23篇
  2005年   27篇
  2004年   25篇
  2003年   17篇
  2002年   14篇
  2001年   14篇
  2000年   18篇
  1999年   37篇
  1998年   17篇
  1997年   13篇
  1996年   13篇
  1995年   12篇
  1994年   8篇
  1993年   9篇
  1992年   4篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   2篇
  1983年   2篇
  1977年   1篇
排序方式: 共有495条查询结果,搜索用时 15 毫秒
391.
The magma eruption rates of Merapi volcano form 1890 to 1992 are re-examined chronologically. For this volcano, movements of extruded lavas and domes as well as their extrusions are important because they control the modes of the subsequent activities and cause nuées ardentes and lahars. The monthly eruption rates varied widely, but the cumulative volume of lavas has increased linearly and is expressed as 0.1x106 m3/month. The magma production rate of this volcano may have been constant for these 100 years. Recurrent excessive effusion of lavas is tentatively interpreted by assuming a magma reservoir. The averaged eruption rate is small in comparison with other volcanoes such as Nyramuragia, Kilauea and Vesuvio. However, it is remarkable that the activity has been continuous for these 100 years and the total amount of lava discharged during this period reached more than 108 m3. A simple model for the formation of the 1992 lava dome is presented. The viscosity of the lavas is probably between 106 and 107 P and the length of the magma conduit is probably less than 10 km.  相似文献   
392.
出露于石棉田湾乡杜河坝-菩萨岗一带的石英角斑岩,以前被认为是侵入的花岗岩,其所在地层组为苏雄组,经研究,该岩石与围岩为沉积接触关系而非侵入接触关系,具变余斑状结构和变余流纹构造,该石英角斑岩成因的确定,为所赋存的地层组更名为观音崖组提供了重要依据。  相似文献   
393.
本文通过海底火山和海底水热活动对海温影响实例,指出海水温度不仅受大气状态的影响,而且还受海洋地壳热力状态的影响。在对海温变化的研究中,除考虑海气间的相互作用外,洋壳对海温的影响也是不可忽视的。对全球气候有重大影响的厄尼诺事件可能是洋壳、海水、大气相互作用的结果。  相似文献   
394.
火山喷发对气候影响信号的检测   总被引:3,自引:0,他引:3       下载免费PDF全文
该文从时序叠加和序列分析两个方面系统地评述了近年来火山活动影响气候的研究进展和代表性工作。给出了火山活动特征,如火山喷发强度、喷发位置和季节等对气候影响的时空分布规律。讨论了与之有关的几个重要问题,如火山指标,火山活动影响气候的途径及其和ENSO的联系等。最后指出了今后研究的几个方向。  相似文献   
395.
火山活动对气候影响的数值模拟研究   总被引:10,自引:0,他引:10       下载免费PDF全文
文章系统地总结了火山活动对气候影响的数值模拟研究,主要结论如下:近百年至千年的气候变化和火山活动关系密切,强火山喷发可造成平流层4℃以上的增温和地表年、月平均温度约0.4℃、1℃的下降。地表温度下降的时空分布受许多因素的影响,如火山喷发特征(包括喷发位置、季节、强度等);海陆分布;火山气溶胶的光学特性;及其由直接辐射强迫引起的经向潜热输送的变化等等。同时还回顾了1991年皮纳图博喷发的有关研究及其对全球气候的可能影响的数值模拟工作。  相似文献   
396.
In this paper,data of solar direct spectral radiance observation in summer and autumn of 1990 and 1991 were usedto derive the average atmospheric extinction spectra for very clear days each year.The difference of these two extinctionspectra is obvious and considered as the contribution of volcanic cloud resulting from Pinatobu's volcanic eruption inmiddle June of 1991.This average size distribution of volcanic cloud was retrieved from the difference spectra and givenin this paper which will be useful for estimation and modeling of the effects of volcanic eruption.  相似文献   
397.
The population of Fogo Island, in Cape Verde, shows a peculiar relationship with the living territory, given that the eminence of volcanic risk is a reality they face every day. The 1951 and 1995 eruptions were particularly scarring in this insular geography, leaving in several generations of Cape Verdeans, the mark of a creation‐destruction‐restart cycle, as well as an attitude of symbiosis with nature. This article is intended to present and discuss results from a scientific research paper based on a study conducted on Fogo Island, in Cape Verde, in February 2016, where researchers sought to understand the local population's response to the last volcanic eruption (from November 2014 to February 2015), in a logic of deterritorialization‐reterritorialization, namely in terms of community and territorial resilience. The analysis method was based on direct observation, with record of the views in a field journal, as well as the biographic narratives of all those who were affected, through questionnaires and interviews.  相似文献   
398.
Tsunami deposits in Kyushu Island, Southwestern Japan, have been attributed to the 7.3 ka Kikai caldera eruption, but their origin has not been confirmed. We analyzed an 83-cm-thick Holocene event deposit in the SKM core, obtained from incised valley fill in the coastal lowlands near Sukumo Bay, Southwestern Shikoku Island. We confirmed that the event deposit contains K-Ah volcanic ash from the 7.3 ka eruption. The base of the event deposit erodes the underlying inner-bay mud, and the deposit contains material from outside the local terrestrial and marine environment, including angular quartz porphyry from a small inland exposure, oyster shell debris, and a coral fragment. Benthic foraminifers and ostracods in the deposit indicate various habitats, some of which are outside Sukumo Bay. The sand matrix contains low-silica volcanic glass from the late stage of the Kikai caldera eruption. We also documented the same glass in an event deposit in the MIK1 core, from the incised Oyodo River valley in the Miyazaki Plain on Southeastern Kyushu. These two 7.3 ka tsunami deposits join other documented examples that are widely distributed in Southwestern Japan including the Bungo Channel and Beppu Bay in Eastern Kyushu, Tachibana Bay in Western Kyushu, and Zasa Pond on the Kii Peninsula as well as around the caldera itself. The tsunami deposits near the caldera have been divided into older and younger 7.3 ka tsunami deposits, the younger ones matching the set of widespread deposits. We attribute the younger 7.3 ka tsunami deposits to a large tsunami generated by a great interplate earthquake in the Northern part of the Ryukyu Trench and (or) the Western Nankai Trough just after the late stage of the Kikai caldera eruption and the older 7.3 ka tsunami deposits to a small tsunami generated by an interplate earthquake or Kikai caldera eruption.  相似文献   
399.
Explosive volcanic eruptions can cause long-term landscape change, leading to increased sediment discharge that continues after the cessation of the eruptions. During the period 1990–1995, eruptions of Mount Unzen, Japan, generated large amounts of pyroclastic material, resulting in 57 debris-flow events during 1991–2018. To investigate changes in the relationships between rainfall characteristics and debris-flow occurrence, we conducted the following: geometric analysis of two gullies (i.e., debris-flow initiation zones) using LiDAR (light detection and ranging)-generated 1 m DEMs (digital elevation models); rainfall analysis, based on the relationship between rainfall duration and mean intensity (i.e., considering the intensity–duration, or ID, threshold); and debris-flow monitoring during 2016–2018. Since 1991, rainfall runoff has caused erosion of the supplied pyroclastic material, generating a channel network consisting of incised gullies. With sufficient rainfall, debris flows formed, accompanied by further gully erosion; this resulted in both vertical and lateral adjustments of the cross-sectional geometry. In the two decades since the eruptions ceased, readily mobilized pyroclastic material has become scarce as the gullies have adjusted to local hydrographic conditions. At the same time, the infiltration capacity of the volcanic flank has increased, reducing the capacity for overland flow. As a result, since 2000, rainfall events with intensities above the ID threshold have occurred; however, the lack of sediment supplied by the gullies appears to have hindered the occurrence and development of debris flows. This suggests that debris flows in volcanically perturbed landscapes may occur at lower rainfall thresholds as long as the corresponding upland channels are evolving as a result of intense overland flow. However, as such channels evolve towards equilibrium geometries, the frequency of debris flows decreases in response to the reduction in sediment availability.  相似文献   
400.
阐述了龙岗火山的地质构造及历史喷发特点,重点分析了龙岗火山区的现今地震活动性及地壳变形特点。结果表明,龙岗火山区现今地震活动性在不断增强,震源深度逐渐变浅;地壳形变有明显变化,火山活动趋于加强,未来潜在喷发的危险性不容忽视。  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