全文获取类型
收费全文 | 142篇 |
免费 | 2篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 28篇 |
地球物理 | 34篇 |
地质学 | 37篇 |
海洋学 | 16篇 |
天文学 | 3篇 |
自然地理 | 24篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1966年 | 2篇 |
1955年 | 1篇 |
1950年 | 1篇 |
1913年 | 1篇 |
排序方式: 共有144条查询结果,搜索用时 875 毫秒
41.
A geophysical study of the northern Svalbard continental margin 总被引:1,自引:0,他引:1
42.
43.
The roughness height z
0 and the zero-plane displacement height d
0 were determined for a region of complex terrain in the Pre-Alps of Switzerland. This region is characterized by hills of the order of 100 m above the valley elevations, and by distances between ridges of the order of 1 km; it lies about 20 to 30 km north from the Alps. The experimental data were obtained from radiosonde observations under near neutral conditions. The analysis was based on the assumption of a logarithmic profile for the mean horizontal wind existing over one half of the boundary layer. The resulting (z
0/h) and (d
0/h) (where h is the mean height of the obstacles) were found to be in reasonable agreement with available relationships in terms of placement density and shape factor of the obstacles, which were obtained in previous experiments with h-scales 2 to 4 orders of magnitude smaller than the present ones. 相似文献
44.
Regional roughness of the landes forest and surface shear stress under neutral conditions 总被引:2,自引:1,他引:2
Mean wind velocity profiles were measured by means of radio-windsondes over the Landes region in southwestern France, which consists primarily of pine forests with scattered villages and clearings with various crops. Analysis of neutral profiles indicated the existence of a logarithmic layer between approximately z – d
0 = 67(±18)z
0 and 128(+-32)z
0 (z is the height above the ground, z
0 the surface roughness and d
0 the displacement height). The upper limit can also be given as z – d
0 = 0.33 (±0.18)h, where h is the height of the bottom of the inversion. The profiles showed that the surface roughness of this terrain is around 1.2 m and the displacement height 6.0 m. Shear stresses derived from the profiles were in good agreement with those obtained just above the forest canopy at a nearby location with the eddy correlation method by a team from the Institute of Hydrology (Wallingford, England). 相似文献
45.
New seismic data off East Greenland were acquired in the summer of 2002, between 77°N and 81°N, north of the Greenland Fracture zone. The data were combined with results from the Greenland Basin and ODP site 909, and indicate a pronounced middle Miocene unconformity within the deep sea basins between 72°N and 81°N. Seismic unit NA-1 consists of sediments older than middle Miocene age and unit NA-2 contains sediments younger than the middle Miocene. Classification of a thinly bedded succession in the Molloy Basin resulted in a subdivision into four units (unit I, unit II, unit IIIA and unit IIIB). A comparison of volume estimations and sediment thickness maps between 72°N and 81°N indicates differences in sediment accumulation in the Greenland, Boreas and Molloy basins. Important controls on the variation of accumulation included different opening times of the basins, as well as tectonic conditions and varying sources of sediment transport.Due to prominent basement structures and the varying reflection character of the sediments along the entire East Greenland margin, we defined an age model of shelf sediments on the basis of similar sediment deposit geometry and known results from other regions. The seismic sequences on the shelf up to an age of middle Miocene are divided into three sub-units along the East Greenland margin: middle Miocene–middle late Miocene (SU-3), middle late Miocene–Pleistocene (SU-2), Pleistocene (SU-1). The differences in the geometry of the sequences show more ice stream related sedimentation between 72°N and 77°N and more ice sheet related sedimentation north of 78°N. The region south of 68°N is dominated by more aggradational sedimentary strata so that a glacio-fluvial drainage seems the main transport mechanism. Due to the Greenland Inland–ice borderlines, we assume the glaciers between the Scoresby Sund and 68°N did not reach the shelf break. A first comparison of the sediment structure of the Northeast Greenland margin with the Southeast Greenland margin made it possible to demonstrate significant differences in sedimentation along this margin. 相似文献
46.
Armin Freundt Wilfried Strauch Steffen Kutterolf Hans-Ulrich Schmincke 《Pure and Applied Geophysics》2007,164(2-3):527-545
This paper emphasizes the fact that tsunamis can occur in continental lakes and focuses on tsunami triggering by processes
related to volcanic eruptions and instability of volcanic edifices. The two large lakes of Nicaragua, Lake Managua and Lake
Nicaragua, host a section of the Central American Volcanic Arc including several active volcanoes. One case of a tsunami in
Lake Managua triggered by an explosive volcanic eruption is documented in the geologic record. However, a number of events
occurred in the past at both lakes which were probably tsunamigenic. These include massive intrusion of pyroclastic flows
from Apoyo volcano as well as of flank-collapse avalanches from Mombacho volcano into Lake Nicaragua. Maar-forming phreatomagmatic
eruptions, which repeatedly occurred in Lake Managua, are highly explosive phenomena able to create hugh water waves as was
observed elsewhere. The shallow water depth of the Nicaraguan lakes is discussed as the major limiting factor of tsunami amplitude
and propagation speed. The very low-profile shores facilitate substantial in-land flooding even of relatively small waves.
Implications for conceiving a possible warning system are also discussed. 相似文献
47.
48.
Wilfried Brutsaert 《Advances in water resources》2000,23(8):447
The parameter n in the well-known expression for hydraulic conductivity K=K0Sen (where K0 is its value at satiation and Se the effective saturation) is determined as a function of the exponent in the power form of the soil–water retention relationship. The result is validated with an extensive experimental database comprising some 43 soils, collected by Mualem. 相似文献
49.
Wilfried Heller 《GeoJournal》2000,50(2-3):151-155
There is no standard model of transformation for post- socialist countries and each country encounters specific problems rooted
in the geographical characteristics of the areas concerned. The human resources are of the greatest importance because it
really matters how people (especially the decision-makers) perceive system change and continually reformulate their expectations
and strategies; so investigations into the views of people caught up in the transformation can provide a deeper understanding
of the background to structural change. Working the national, regional level and local levels in Romania, experts were asked
to consider the advantages and disadvantages arising out of the transformation, the most important problems and constraints
for future rural development and the policies needed. The paper examines the responses on demographic and social issues. It
emerges the most detailed responses were supplied by local-level representatives while respondents at the regional level steered
a middle course between the need to address local problems and the prime importance of stimulating the Romanian economy so
as to generate resources for welfare programmes (with the latter issue the overriding concern of interviewees at national
level). There was general agreement on the importance of foreign investment and European integration for economic development,
with local actors taking only small steps in line with the existing opportunities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
Crustal extension during and following continental collision is well documented in the Arctic Caledonian fold belt. However, models for the post-collisional extension of the Caledonides are mainly based on geoscientific data from Scandinavia. For a more complete understanding of the evolution of the Caledonides, knowledge of the crustal structure of East Greenland is vital. Seismic and gravity studies have revealed a pronounced Moho topography and a west-dipping lower crustal reflector beneath the fjord region of East Greenland. These deep crustal structures are related to Late Caledonian extensional structures at the surface. The observations can be satisfactorily explained by applying simple shear or eduction models proposed for upper crustal extension in Scandinavia to the complementing lower crustal structures in East Greenland. However, exhumation of the Caledonian Northeast Greenland eclogite province cannot be accomplished by these models. Instead, a synthesis of geoscientific data has shown marked differences in the crustal structure of East Greenland north and south of about 76°N, indicating a different crustal evolution of the northern and southern parts of the East Greenland Caledonides. 相似文献