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   127篇
  免费   4篇
  国内免费   3篇
测绘学   1篇
大气科学   2篇
地球物理   30篇
地质学   22篇
海洋学   31篇
天文学   43篇
综合类   1篇
自然地理   4篇
  2021年   3篇
  2019年   1篇
  2017年   4篇
  2016年   1篇
  2014年   7篇
  2013年   5篇
  2012年   5篇
  2011年   5篇
  2010年   8篇
  2009年   4篇
  2008年   8篇
  2007年   10篇
  2006年   8篇
  2005年   4篇
  2004年   3篇
  2003年   4篇
  2002年   7篇
  2001年   4篇
  2000年   4篇
  1999年   2篇
  1998年   6篇
  1994年   3篇
  1993年   1篇
  1992年   1篇
  1989年   4篇
  1988年   3篇
  1986年   2篇
  1985年   2篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1975年   1篇
  1974年   2篇
  1969年   1篇
  1966年   1篇
  1963年   1篇
排序方式: 共有134条查询结果,搜索用时 31 毫秒
91.
92.
It is shown that Mie theory predictions of extinction for pure water-ice with the optical constant measured at 100 K do not fit in detail the observed ice absorption feature in infrared objects, although we attempt to explain the observations by considering size distribution and shape of the grains.In addition, based on a similarity between the ice band and the absorption band found in carbon stars, we feel it is questionable whether or not the ice band can really be attributed to the interstellar water-ice.  相似文献   
93.
94.
Water injection experiments were performed in 1997, 2000 and 2003 at the 1800 m borehole near the fracture zone of the 1995 Hyogo-ken Nanbu earthquake. During these experiments, a contraction of about 10− 8–10− 7 was observed with three-component strainmeters at a bottom of the 800 m borehole, 70 m southwest of the 1800 m borehole. We estimated hydraulic properties of the fracture zone near the Nojima fault by using the strain data to investigate a healing of the fault during the postseismic stage. We calculated pore pressure changes due to the water injection using Darcy's equation and obtained strain changes due to the pore pressure changes as elastic deformations of the crust. The calculated strain changes have a nearly agreement with the observed strain changes. Hydraulic conductivity in 1997, 2000 and 2003 was determined to be 0.9 ± 0.2 × 10− 6, 0.8 ± 0.2 × 10− 6 and 0.4 ± 0.1 × 10− 6 m/s, respectively. The reduced hydraulic conductivities in 2000 and 2003 suggest that the fractures had been healing.  相似文献   
95.
电法探查海岸带含水层咸淡水界面的调查研究   总被引:6,自引:0,他引:6  
本文在理论上对电法探查多层土层组成的海岸带含水层的咸淡水界面的可能性进行探讨的基础上,对太平洋沿岸某地区进行了实地调查研究。在测量设置在海岸附近及分布于海岸纵深方向的调查井垂直方向电导率的同时,在调查井附近进行了电法探查。结果表明,电法探查的咸淡水界面的深度与依据井水电导率区分的混合区域上端几乎一致,即对于不同类别土质构成的岩土层,电法不但能探查确定咸淡水界面的深度,而且与以往的手法比较也是一种简单、快速、可靠、成本低廉的确定咸淡水界面深度的方法。  相似文献   
96.
Depleted reservoirs of natural gas and petroleum can provide excellent traps for carbon dioxide. Deep aquifers, which are not used due to high salinity, can host larger amount of the carbon dioxide under their high formation pressure than natural gas and oir reservoirs. Small fraction of aquifers in sedimentary basins in the world are enough to host about 87 gigaton-C of carbon dioxide.

A preliminary technical and economical survey on the carbon dioxide injection system suggests that the energy requirement for carbon dioxide injection into subterranean aquifers is about 269 kWh/ton-C and that the investment and operation costs for system are 79 $/ton-C. By our preliminary cost estimation in Japan, the CO2-emission-free electricity generation may become possible with a cost increase of 35% for natural-gas-fired power station, and of 60% for coal-fired-power station.  相似文献   

97.
Oceanic crust production and climate during the last 100 Myr   总被引:2,自引:0,他引:2  
In order to evaluate the possible influence of oceanic crust production on climatic changes during the past 100Myr variations in total oceanic crust for this period including production at mid-ocean ridges, oceanic plateaus, and back-arc basins were calculated using the most recent and accurate time-scales. The rates presented here differ from those of Larson (1991a, b) on Cenozoic fluctuations and show that (1) maximum production values occurred during the Cenomanian, Palaeocene, and late Oligocene-early Miocene and (2) minimum values occurred in Campanian-Maastrichtian, late Eocene, and middle Miocene. Significantly, variations of oceanic crust production correspond with variations in the δ18O of deep-water benthic foraminifera: maximum values of oceanic crust production correspond with minimum values of δ18O, and minimum production values with maximum values of δ18O. This latter synchronism suggests that changes in land-sea relationships and atmospheric CO2 related to major fluctuations in oceanic crust production were the main cause of mid-Cretaceous warming and Late Cretaceous cooling, and of climatic quasi-cycles having a periodicity of 33–38 million years over the last 100 Myr. This is the first report showing variations of ocean crust production synchronized with the Cenozoic climate changes.  相似文献   
98.
Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m−2 day−1) and organic matter (mainly detritus; 333 mg m−2 day−1) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81–93 mg m−2 day−1) and opal as biosilica (51–67 mg m−2 day−1), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 106 cells m−2 day−1), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.  相似文献   
99.
Gridded data of global surface wind/wind-stress vectors, called J-OFURO v2, were obtained from satellite scatterometer (QuikSCAT/SeaWinds) data for the decade from August 1999 to July 2009. The data were validated by comparing with (1) in situ measurements from moored buoy observations, (2) a data product from the same scatterometer using a different gridding procedure (IFREMER), and (3) data products based on numerical models (NCEP-1 and NCEP-2). The results on averaging all buoy data revealed lower mean differences, lower root-mean-square (RMS) differences, and higher correlations for the wind/wind-stress components for the J-OFURO v2 product than the other data products. The statistical values calculated for each buoy station showed tendencies of decreasing reliability with increasing latitude in the mid-latitude region, while the reliabilities in the equatorial areas were low. We performed intercomparisons between the J-OFURO v2 data and the other data sets to clarify discrepancies among different wind products in open ocean regions with few moored buoys. We determined that the meridional wind components from the NCEP products exhibited poleward deviations compared to data from the J-OFURO v2 product. Relatively high mean differences, high RMS differences, and low correlations were found in the equatorial ocean for the NCEP products. Striped features were spatially correlated with buoy locations in the equatorial Pacific, which suggested that the reliability of the NCEP products was governed by buoy locations in this region.  相似文献   
100.
Hydrological and sediment fluxes were monitored for a 1 yr period in a tropical headwater catchment where a 3 yr old logging road caused substantial Hortonian overland flow (HOF) and intercepted subsurface flow (ISSF). On a 51·5 m road section, ISSF became an increasingly important component of total road runoff, up to more than 90% for large storms. The proportion of ISSF contributed by road cuts along more or less planar slopes compared with ISSF from a zero‐order basin (convergent slopes) truncated by the road declined with increasing rainfall. During the monitored storms that generated ISSF along the road, on average, 28% of sediment export and 79% of runoff from the road section were directly attributable to ISSF. Estimates of total sediment export from the road surface (170 t ha?1 yr?1) and suspended sediment export from the logging‐disturbed catchment (4 t ha?1 yr?1) were exceptionally high despite 3 yr of recovery. ISSF caused not only additional road‐generated sediment export, but also exacerbated HOF‐driven erosion by creating a poor foundation for vegetation recovery on the road surface. Copyright © 2007 John Wiley & Sons, Ltd.  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