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   37606篇
  免费   6719篇
  国内免费   7973篇
测绘学   3529篇
大气科学   4874篇
地球物理   8171篇
地质学   20333篇
海洋学   3950篇
天文学   3383篇
综合类   2471篇
自然地理   5587篇
  2024年   118篇
  2023年   458篇
  2022年   1260篇
  2021年   1462篇
  2020年   1333篇
  2019年   1589篇
  2018年   1262篇
  2017年   1417篇
  2016年   1481篇
  2015年   1700篇
  2014年   2152篇
  2013年   2108篇
  2012年   2277篇
  2011年   2418篇
  2010年   2120篇
  2009年   2653篇
  2008年   2539篇
  2007年   2674篇
  2006年   2605篇
  2005年   2477篇
  2004年   2215篇
  2003年   2049篇
  2002年   1760篇
  2001年   1537篇
  2000年   1543篇
  1999年   1367篇
  1998年   1154篇
  1997年   854篇
  1996年   680篇
  1995年   602篇
  1994年   559篇
  1993年   475篇
  1992年   323篇
  1991年   288篇
  1990年   207篇
  1989年   167篇
  1988年   138篇
  1987年   73篇
  1986年   42篇
  1985年   35篇
  1984年   17篇
  1983年   12篇
  1982年   11篇
  1981年   8篇
  1980年   9篇
  1979年   8篇
  1978年   16篇
  1977年   5篇
  1976年   5篇
  1954年   7篇
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
951.
地震次生毒气泄漏与扩散的数值模拟与动态仿真   总被引:16,自引:1,他引:16  
文章对破坏性地震中可能发生的次生毒气泄漏与扩散灾害进行了数值模拟与动态仿真研究,设定了几种有实际意义的数值分析模型,分别进行了结构地震破坏,有毒有害气体泄漏,在一定泄漏和气象条件下的向周围空间扩散的动态仿真研究,给出了典型毒气扩散过程中可致人员死亡,严重危险和有感区域的范围的动态变化结果,作者认为地震次生毒气泄漏与扩散研究对大地震应急、城市和大型企业防灾都有重要的意义和广阔的应用前景。  相似文献   
952.
2001年11月14日新疆-青海交界8.1级地震   总被引:3,自引:0,他引:3  
简要介绍了2001年11月14日新疆-青海交界8.1级地震的预测情况,给出了中、美、日等对此次地震的震源参数测定和震源机制,以及余震的分布和加卸载响应比随时间的变化。进而对震区近期地震趋势进行预测。  相似文献   
953.
科学的进步使地形变监测事业得到长足发展,市场经济的繁荣催生出形变监测行业独有的管理之道。形变监测行业是个介于科研、IT及服务行业三者之间的特殊行业,因此,它的发展必须具有一定的科学性、前瞻性和服务性。  相似文献   
954.
This paper presents the results of a study undertaken todetermine the seismic hazard of Lebanon. The seismic hazard evaluation wasconducted using probabilistic methods of hazard analysis. Potential sourcesof seismic activities that affect Lebanon were identified and the earthquakerecurrence relationships of these sources were developed from instrumentalseismology data, historical records, and earlier studies undertaken toevaluate the seismic hazard of neighboring countries. The sensitivityof the results to different assumptions regarding the seismic sources in theLebanese segment and choice of the attenuation relationship wasevaluated. Maps of peak ground acceleration contours, based on 10percent of probability of exceedance in 50 years and 100 years time spans,were developed.  相似文献   
955.
Post-earthquake field investigations of landslide occurrence have provided a basis for understanding, evaluating, and mapping the hazard and risk associated withearthquake-induced landslides. This paper traces thehistorical development of knowledge derived from these investigations. Before 1783, historical accounts of the occurrence of landslides in earthquakes are typically so incomplete and vague that conclusions based on these accounts are of limited usefulness. For example, the number of landslides triggered by a given event is almost always greatly underestimated. The first formal, scientific post-earthquake investigation that included systematic documentation of the landslides was undertaken in the Calabria region of Italy after the 1783 earthquake swarm. From then until the mid-twentieth century, the best information on earthquake-induced landslides came from a succession ofpost-earthquake investigations largely carried out by formal commissions that undertook extensive ground-based field studies. Beginning in the mid-twentieth century, when the use of aerial photography became widespread, comprehensive inventories of landslide occurrence have been made for several earthquakes in the United States, Peru, Guatemala, Italy, El Salvador, Japan, and Taiwan. Techniques have also been developed for performing ``retrospective' analyses years or decades after an earthquake that attempt to reconstruct the distribution of landslides triggered by the event. The additional use of Geographic Information System (GIS) processing and digital mapping since about 1989 has greatly facilitated the level of analysis that can applied to mapped distributions of landslides. Beginning in 1984, syntheses of worldwide and national data on earthquake-induced landslides have defined their general characteristics and relations between their occurrence and various geologic and seismic parameters. However, the number of comprehensive post-earthquake studies of landslides is still relatively small, and one of the most pressing needs in this area of research is for the complete documentation of landslides triggered by many more earthquakes in a wider variety of environments.  相似文献   
956.
957.
Introduction The measurements of the compressional wave velocity and electrical conductivity of minerals and rocks are of fundamental importance to look into the earths interior, including composition, geotherm, generation and distribution of fluids and melts. Hydrous minerals formed by metamatu-siom are abundant within the earth. Previous studies have been carried out on the dehydration effect on the electrical conductivity and wave velocity of rocks such as serpentine, amphibole, most of whi…  相似文献   
958.
Positive tectonic inversion is related to the transmission of compressional stresses along a décollement into the foreland of an orogenic zone. This stress and strain concentration in regions remote from the main orogenic front is commonly related to the presence of pre-existing rheological heterogeneities such as normal syn-depositional faults. During inversion, these pre-existing normal faults are reactivated as reverse faults. Tectonic inversion in the Rhenohercynian fold-and-thrust belt during the Variscan Orogeny shows that inversion is likely synchronous with the onset of collision in the hinterland. Here, we present the results of a simplified thermo-mechanical model (STM) which allows one to study strain partitioning between two orogenic zones. We show that, if the two orogenic zones have the same mechanical properties, the viscosity of the décollement, which links them, controls the initial strain partitioning. During subsequent finite shortening, erosional processes determine the partitioning of strain rate. The presence of a weak structure in the inverted zone and of a low-viscosity décollement leads to initial strain concentration in the inverted track rather than in the collision zone and a progressive decrease in strain partitioning between the two orogenic zones. The STM results are in good agreement with results of a 2D finite-element model. We conclude that, in the western part of the Rhenohercynian Massif, simultaneous uplift and deformation within the Mid-German Crystalline Rise (the main collision zone) and the Ardenne Anticlinorium (the inverted zone) lead to interpreting this orogenic event as a case of vice tectonic rather than the propagation of a ‘wave of folding’ towards the Variscan front, as suggested by previous authors.  相似文献   
959.
环渤海地区油气资源探查的思考   总被引:6,自引:6,他引:6  
回顾过去渤海勘探实践的经验,对于指导今后的研究工作是十分重要的。40年来渤海地区发现大量新老第三纪陆相石油资源,成为中国的重要产油区,也积累了丰富的勘探经验。深化环渤海地区油气资源的探查,首先应考虑前新生代海相油气资源。但其勘探是高难度的,前景是诱人的。应该认真贯彻下列认识原则:(1)区域指导局部;(2)深部制约浅层;(3)在地震处理解释创新的同时,大力发展综合地质地球物理研究。  相似文献   
960.
黄海及其边缘,经历史地震资料整理,地震参数估定与编目,截至1949年8月,共有M≥3级地震2187次,其中M≥43/4级地震259次,资料显示大致有三个相对集中活跃区,16世纪曾有过历史地震活动高潮。  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