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   1279篇
  免费   30篇
  国内免费   2篇
测绘学   52篇
大气科学   61篇
地球物理   613篇
地质学   298篇
海洋学   22篇
天文学   235篇
综合类   5篇
自然地理   25篇
  2018年   31篇
  2017年   32篇
  2016年   54篇
  2015年   33篇
  2014年   47篇
  2013年   55篇
  2012年   20篇
  2011年   31篇
  2010年   43篇
  2009年   37篇
  2008年   32篇
  2007年   28篇
  2006年   28篇
  2005年   13篇
  2004年   23篇
  2003年   21篇
  2002年   29篇
  2001年   26篇
  2000年   22篇
  1999年   14篇
  1998年   19篇
  1997年   16篇
  1996年   31篇
  1995年   23篇
  1994年   23篇
  1993年   33篇
  1992年   21篇
  1991年   16篇
  1990年   16篇
  1989年   25篇
  1988年   18篇
  1987年   22篇
  1986年   21篇
  1985年   19篇
  1984年   18篇
  1983年   24篇
  1982年   21篇
  1981年   15篇
  1980年   20篇
  1979年   20篇
  1978年   26篇
  1977年   24篇
  1976年   18篇
  1975年   17篇
  1974年   13篇
  1973年   18篇
  1972年   12篇
  1971年   21篇
  1970年   11篇
  1969年   13篇
排序方式: 共有1311条查询结果,搜索用时 15 毫秒
31.
The preparation of the preliminary seismic hazard maps of the territory of Slovenia has been based on an expansion of the basic approach laid out by Cornell in 1968. Three seismic source models were prepared. Two of them are based mainly on the earthquake catalogue using the Poissonian probability model. A map of seismic energy release and a map of earthquake epicenter density are used to delineate seismic sources in these models. The geometry of the third model which is based on a rough estimate of seismotectonic setting is taken from the probabilistic seismic hazard analysis of a nuclear power plant in Slovenia. Published ground motion attenuation models based on strong motion records of recent strong earthquakes in Italy are used. Test maps for variable and uniform b-values are presented. The computer program, Seisrisk III, developed by the U.S. Geological Survey is used.  相似文献   
32.
Croatia, through its geographic position, is a Mediterranean/Adriatic and Central European/Danube state. As an Adriatic coastal state, it has a long maritime tradition, which is apparent in its well-developed shipping (2.4 million GT), the high-quality ship-building industry (among the top six in the world) and through its numerous sea ports, of which many were established in ancient times. The leading national port is Rijeka, which is at the same time an important transit port for Austria, Hungary, Slovakia and the Czech Republic.The exceptionally indented Croatian Adriatic coast with its attractive archipelagos and favorable climatic and oceanographic conditions in the coastal sea offers very advantageous conditions for comprehensive tourist utilization. This is particularly true of nautical tourism, which is complimented by a larger number of constructed and well-equipped yachting ports/marinas on the coast and islands.  相似文献   
33.
Špičák  A.  Mrlina  J.  Jindra  D.  Mervart  L. 《Studia Geophysica et Geodaetica》1997,41(4):319-328
The western part of the Bohemian Massif is characterized by repeated occurrences of intraplate earthquake swarms. To study surface deformations of this anomalous region, a network covering about 2000 square kilometres for repeated geodetic measurements was established in 1993 - 1994. The positions of the individual points of the network were carefully picked with respect to local tectonic structure and earthquake foci distribution. GPS and precise levelling measurements were performed 1-2 times a year. The GPS data were processed by Bernese GPS software. No tendency to any displacement - either horizontal or vertical - of geological blocks was derived from the geodetic data for the period 1993 - 96. Only displacements of less than 5 mm/year in average could occur in the whole region in that period; larger displacements would have been revealed by our measurements.  相似文献   
34.
35.
36.
37.
The respiratory potential [i.e. electron transport system activity (ETSA)] of soils and sediments from five floodplain habitats (channel, gravel, islands, riparian forest and grassland) of the Urbach River, Switzerland, and actual respiration rate (R) of the same samples exposed to experimental inundation were measured. Measurements were carried out at three incubation temperatures (4°C, 12°C and 20°C), and ETSA/R ratios (i.e. exploitation of the overall metabolic capacity) were investigated to better understand the effects of temperature and inundation on floodplain functional heterogeneity. Furthermore, ETSA/R ratios obtained during experimental inundation were compared with ETSA/R ratios from field measurements to investigate the exploitation in total metabolic potential at different conditions. Lowest ETSA and R were measured in samples from channel and gravel habitats, followed by those from islands. Substantially higher values were measured in soils from riparian forest and grassland. Both ETSA and R increased with increasing temperature in samples from all habitats, while the ETSA/R ratio decreased because of a rapid response in microbial community respiration to higher temperatures. The metabolic capacity exploitation (i.e. ETSA/R) during experimental inundation was lowest in predominantly terrestrial samples (riparian forest and grassland), indicating the weakest response to wetted conditions. Comparison of experimentally inundated and field conditions revealed that in rarely flooded soils, the metabolic capacity was less exploited during inundation than during non‐flooded conditions. The results suggest high sensitivity in floodplain respiration to changes in temperature and hydrological regime. ETSA/R ratios are considered good indicators of changes in metabolic activity of floodplain soils and sediments, and thus useful to estimate the impact of changes in hydrological regime or to evaluate success of floodplain restoration actions. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
38.
39.
40.
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