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   152篇
  免费   6篇
  国内免费   8篇
测绘学   2篇
大气科学   14篇
地球物理   46篇
地质学   47篇
海洋学   30篇
天文学   16篇
综合类   4篇
自然地理   7篇
  2022年   1篇
  2020年   2篇
  2019年   6篇
  2018年   4篇
  2017年   5篇
  2016年   5篇
  2015年   6篇
  2014年   9篇
  2013年   12篇
  2012年   8篇
  2011年   11篇
  2010年   4篇
  2009年   1篇
  2008年   6篇
  2007年   9篇
  2006年   12篇
  2005年   8篇
  2004年   9篇
  2003年   9篇
  2002年   2篇
  2001年   5篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1971年   1篇
  1968年   1篇
  1938年   1篇
排序方式: 共有166条查询结果,搜索用时 250 毫秒
91.
Ulva are ubiquitous and opportunistic green algae species that easily adapt to various environmental conditions. These algae are responsible for the green  相似文献   
92.
The study of historical earthquakes itself has an interesting history, and Nick Ambraseys figures highly in it. This historiographic tribute relates the pivotal role that he played in the development of the British and Scandinavian Earthquake Archives. Maintaining his academic distance from direct hazard consulting, he nevertheless exerted a significant influence on the scientific conduct of hazard analyses. From the collection of instrumental and macroseismic data to the assignment of magnitudes, the modus operandi which he recommended was followed in pioneering seismic hazard studies in Britain, the North Sea and Norway, during the 1980s. Because of the confidentiality of seismic hazard reports produced for the UK nuclear industry, there is little record in the open seismological literature of the contribution of Nick Ambraseys. As a civil engineer, he had an exceptional interest in the earthquake evidence that could be gleaned from historical documents. An illustrative reference is given to the discovery of fresh evidence from an Aegean earthquake that shows how even the most knowledgeable of earthquake historians can be surprised.  相似文献   
93.
94.
95.
In an effort to assess the reliability of satellite altimeter systems, the authors conduct a comparative analysis of sea level data that were collected from the TOPEX/POSEIDON (T/P) altimeter and 10 tide gauges (TG) near the satellite passing ground tracks. The analysis is made using datasets collected from marginal sea regions surrounding the Korean Peninsula at T/P cycles of 2 to 230, which correspond to October 1992 to December 1998. Proper treatment of tidal errors is a very critical step in data processing because the study area has very strong tide. When the T/P data are processed, the procedures of Park and Gamberoni (1995) are adapted to reduce errors associated with the tide. When the T/P data are processed in this way, the alias periods of M2, $2, and K1 constituents are found to be 62.1, 58.7, and 173 days repectively. The compatibility of the T/P and TG datasets are examined at various filtering periods.The results indicate that the low-frequency signals of the T/P data can be interpreted more safely with longer filtering periods (such as up to the maximum selected value of 200 days). When RMS errors for the 200-day low-pass filter period are compared with all 10 tidal stations, the values span the range of 2.8 to 6.7 cm. The results of a correlation analysis for this filtering period also show a strong agreement between the T/P and TG datasets across all stations investigated (e.g., p-values consistently less than 0.001). Hence according to the analysis, the conclusion is made that the analysis of surface sea level using satellite altimeter data can be made safely with reasonably extended filtering periods such as 200 days.  相似文献   
96.
The non-marine Cretaceous Kyongsang Supergroup, which is divided into the Sindong, the Hayang and the Yuchon groups, is widely distributed in southeastern Korea. Radiolarian-bearing pebbles are collected from the conglomerates of the Kumidong and the Kisadong formations of the Hayang Group. The age of radiolarian fossils range from Late Permian to Middle Jurassic. In Korea, Permian to Middle Jurassic marine chert beds are not exposed. The directions of paleocurrents of the Kumidong and the Kisadong formations are mainly from the northeast to southwest. During Cretaceous time, the Mino-Tamba Belt, within which Permian to Middle Jurassic chert beds are exposed, is suggested to have been located northeast of the Kyongsang Basin. The radiolarian faunas of the Hayang Group are similar to those of the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan (e.g. the Ashio Belt). The provenance of the radiolarian-bearing pebbles collected from the Kumidong and the Kisadong formations is interpreted to be the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan.  相似文献   
97.
韩国的溶洞开发虽然起步较晚,但其对溶洞的保护却有许多值得学习和借鉴之处,本文以幻仙洞为例介绍了韩国的溶洞开发现状、管理问题、相关法律法规及保护措施,并提出了作者的建议。  相似文献   
98.
The objective of this study is to investigate the effect of masonry infills on the seismic performance of low‐rise reinforced concrete (RC) frames with non‐seismic detailing. For this purpose, a 2‐bay 3‐storey masonry‐infilled RC frame was selected and a 1 : 5 scale model was constructed according to the Korean practice of non‐seismic detailing and the similitude law. Then, a series of earthquake simulation tests and a pushover test were performed on this model. When the results of these tests are compared with those in the case of the bare frame, it can be recognized that the masonry infills contribute to the large increase in the stiffness and strength of the global structure whereas they also accompany the increase of earthquake inertia forces. The failure mode of the masonry‐infilled frame was that of shear failure due to the bed‐joint sliding of the masonry infills while that of the bare frame appeared to be the soft‐storey plastic mechanism at the first storey. However, it is judged that the masonry infills can be beneficial to the seismic performance of the structure since the amount of the increase in strength appears to be greater than that in the induced earthquake inertia forces while the deformation capacity of the global structure remains almost the same regardless of the presence of the masonry infills. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
99.
Evaluation of pedestrian winds around tall buildings by numerical approach   总被引:4,自引:0,他引:4  
Summary A numerical model based on the compressible flow equations has been used to simulate the pedestrian wind fields around the programming tall buildings in Beijing city. The model results are well agreed with those of the wind tunnel experiments. Since numerical model can provide the detailed flow field data at each grid point and each time step, it has a great advantage compared with the wind tunnel experiment in accurately evaluating the wind effects on pedestrian and other environmental issues. Furthermore, advance computational technology has made the numerical modeling become fast and cheaply. It is believed that the numerical simulation will play an increasingly more important role in the coming years, especially in dealing with wind environment.  相似文献   
100.
We conducted various field studies at the seawater intrusion monitoring wells located in the eastern part of Jeju Island, Korea, to observe the tidal effect on groundwater–seawater flow in the coastal aquifer. Studies included monitoring the fluctuations of groundwater and tide levels, electrical and temperature logging, and 2-D heat-pulse flowmeter tests. According to time-series analysis, tidal effects on groundwater level reached up to 3 km inland from the coastline. Water-level variation was more sensitive to tidal fluctuations near the coast, and more related to rainfall toward inland areas. Temporal and spatial variations in the shape and location of the freshwater–saltwater interface were analyzed using data from nine monitoring wells. The results indicated that the interface toe is located at a distance of 6–8 km from the coastline and its location was related to geological layers present. Long-term seasonal variations revealed no major changes in the interface; minor variations were due to moving boundary conditions induced by tidal fluctuations. Using the two-dimensional heat-pulse flowmeter, groundwater flow directions and velocities at four tidal stages were measured on three monitoring wells drilled into the multilayered aquifers. This direct measurement enabled us to relate the differences of flow velocities and directions with geology and tidal fluctuations. Combining the results of EC logging and flowmeter tests, we found a zone where freshwater and saltwater moved alternately in opposite directions, as influenced by the tidal fluctuations. Integrating various physical logging and flowmeter data with water-level fluctuations improved our understanding of the behavior of fresh and seawater flow in the coastal aquifers.  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