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   293篇
  免费   11篇
  国内免费   1篇
测绘学   14篇
大气科学   5篇
地球物理   64篇
地质学   162篇
海洋学   19篇
天文学   30篇
综合类   2篇
自然地理   9篇
  2023年   2篇
  2022年   7篇
  2021年   9篇
  2020年   13篇
  2019年   7篇
  2018年   20篇
  2017年   24篇
  2016年   25篇
  2015年   14篇
  2014年   25篇
  2013年   31篇
  2012年   17篇
  2011年   14篇
  2010年   15篇
  2009年   17篇
  2008年   6篇
  2007年   5篇
  2006年   4篇
  2005年   3篇
  2004年   4篇
  2003年   5篇
  2002年   3篇
  2001年   7篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   2篇
  1994年   1篇
  1993年   5篇
  1992年   1篇
  1991年   6篇
  1990年   1篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
  1971年   1篇
排序方式: 共有305条查询结果,搜索用时 15 毫秒
1.
Natural Hazards - Highways in arid regions are highly exposed to damage by floods. This requires intensive analysis of flood quantity, time and direction that can be used to design the suitable...  相似文献   
2.
Natural Hazards - Risk perception plays a vital part in flood risk management and mitigation strategies. Therefore, this study aims at first to measure the risk perception of the vulnerable...  相似文献   
3.
Natural Resources Research - This study addresses the three-dimensional (3D) petrophysical modelling and volumetric analysis of the Farewell Reservoir in the Kupe Field in the southern Taranaki...  相似文献   
4.
5.
Natural Hazards - Tornadoes pose a significant threat to residential communities, causing enormous physical damage and losses to their social fabric. The dominant type of single-family residential...  相似文献   
6.
Discharge of the Shatt Al-Arab is believed to be a dominating component of the northern Arabian Gulf’s ecology and largely responsible for productivity of Kuwait’s fisheries. With major construction of dams on the Tigris and Euphrates Rivers in Turkey, river discharge has been substantially reduced, and flooding essentially eliminated. We attempted to relate river flow and shrimp landings indirectly by correlating 19 years of salinity and temperature data from Kuwait’s waters with corresponding annual shrimp landings. For green tiger prawns (Penaeus semisulcatus), the combination of October salinities and January temperatures provided the best correlation (r = 0.67) with landings in the following shrimping season. For the combined landings of jinga and kiddi shrimps (Metapenaeus affinis and Parapenaeopsis stylifera, respectively), December salinity during season and May temperature prior to season resulted in the best correlation (r = 0.87). Landings of these two species also correlated well with spring and summer temperatures. Under normal conditions, late winter or early spring temperatures prior to fishing season influence recruitment of the green tiger prawn, whereas December salinities during harvest season influence the abundance of jinga–kiddi shrimps. With further reductions in the Shatt Al-Arab discharge and the elimination of flood events, Kuwait’s shrimp landings will most likely decrease over time.  相似文献   
7.
The future development of agriculture, industry, and civil activity planned to be in the Western Desert. This strategy need to the groundwater resource. Vertical electrical soundings (VES) and electromagnetic (TEM) measurements conducted in the El Bawiti, northern Bahariya Oasis. The measurements give detailed information about the geometry of the different hydrogeological layers in the aquifer system and depth to them. A total of 22 VES and TEM were carried out within El Bawiti area. Thirty-one sub soil samples were collected from eight sites to determine the chemical characteristics and address the effects of lithogenic source and anthropogenic activity on them. The geoelectrical measurements and borehole information indicate the presence of five geoelectrical units, from top to base; the surface cover, sand and shale, upper aquifer (Nubian sandstone), sand and shale, and lower aquifer (Nubian sandstone). Surface cover was equally distributed in thickness and composed of dry sand, gravel, and clay deposits. The regional resistivity of the upper aquifer increased in the southwestern part and decline in the northern, eastern, southern, and western parts. The decline in the resistivity reflects the high water yields and potentiality, as well as low salinity. The resistivity of the lower aquifer increased due the northwestern part and the southwestern part. The information collected during this research provides valuable data for estimating the fresh- to brackish-water resources and for development of a groundwater management plan. The integrated analyses carried out represent a significant and cost-effective method for delineating the main aquifer in this area. In turn, future well locations can be placed with more confidence than before, in accordance with the evaluation of the potentiality of the groundwater aquifers in the area. The electrical conductivity of the soil ranges from 302 to 8,490 μS/cm, increases in the western and central-northern parts. It is attributed to the location from the salt-affected soils (playa), the relatively lower elevation units (depressions) and the position in landscape in the Oasis. Sodium adsorption ratio ranges from 0.44 to 11 and the exchangeable sodium ratio ranges from 0.11 to 5. The estimated magnesium hazard fluctuated below 50%. The statistical analyses were accomplished in soil chemistry and discussed.  相似文献   
8.
Soil particle size distribution (PSD) is used to estimate some soil processes, soil moisture characteristics, and infiltration rate (IR). Prediction of infiltration rate from soil texture data requires an accurate characterization of PSD. The objective of this study was to determine more important primary particle diameters that control IR. The experiments were conducted using double-ring method with constant head of 5 cm in 15 different soils and three replications. The range of measured IR for studied soils varied from 1.6 to 30.66 cm h?1. The results indicated that the primary PSD had a significant influence on IR. In other words, most D n fractions had significant positive effect on the final IR. Among different fractions, D 30, D 40, and D 60 showed higher relationships with IR than the others. These diameters are attributed to particles with diameter of 0.05, 0.08, and 0.16 mm, respectively. The results also showed that increasing the percent of sand have intensified influence on increasing the final IR. Reversely, clay and silt contents showed negative effects on final IR. Furthermore, the CaCO3 had a meaningful effect on the IR that showed the importance of lime in arid and semiarid regions. Finally, it is revealed that the role of texture was important, especially in behavior of infiltration, runoff, and production capability.  相似文献   
9.
Arabian Journal of Geosciences - The bauxite ore deposits are mainly found around the Az Zabirah area in the central northern part of Saudi Arabia. The age of the Az Zabirah bauxites was suggested...  相似文献   
10.
The present study describes the effect of clouds(macro-physical parameters) on global solar radiation(G).Data from four years of hourly measurements of G on a horizontal surface were used.These data were collected at the South Valley University(SVU) meteorological research station(26.2°N,32.7°E,96 m above mean see level.In addition,the cloud modification factor for G(CMFG) was estimated in three cases:high-level,mid-level,and low-level clouds.For every level,the variation of hourly CMFG as a function of cloud amount(CA) was illustrated.A third-order polynomial between hourly values of CMFG and CA was established.Furthermore,the effect of CA in the attenuation of G relative to its corresponding value in cloudless conditions is discussed.For cloud cover > 88%,G was reduced by 54%,34%,and 28% by low-,mid-,and high-level clouds,respectively.  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