全文获取类型
收费全文 | 1678篇 |
免费 | 470篇 |
国内免费 | 531篇 |
专业分类
测绘学 | 87篇 |
大气科学 | 420篇 |
地球物理 | 261篇 |
地质学 | 740篇 |
海洋学 | 587篇 |
天文学 | 47篇 |
综合类 | 129篇 |
自然地理 | 408篇 |
出版年
2024年 | 15篇 |
2023年 | 43篇 |
2022年 | 84篇 |
2021年 | 121篇 |
2020年 | 92篇 |
2019年 | 95篇 |
2018年 | 89篇 |
2017年 | 91篇 |
2016年 | 101篇 |
2015年 | 127篇 |
2014年 | 119篇 |
2013年 | 126篇 |
2012年 | 96篇 |
2011年 | 85篇 |
2010年 | 79篇 |
2009年 | 104篇 |
2008年 | 111篇 |
2007年 | 108篇 |
2006年 | 95篇 |
2005年 | 116篇 |
2004年 | 90篇 |
2003年 | 95篇 |
2002年 | 92篇 |
2001年 | 74篇 |
2000年 | 68篇 |
1999年 | 56篇 |
1998年 | 50篇 |
1997年 | 39篇 |
1996年 | 38篇 |
1995年 | 22篇 |
1994年 | 31篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有2679条查询结果,搜索用时 15 毫秒
991.
Arne Lohrberg Klaus Schwarzer Daniel Unverricht Andreas Omlin Sebastian Krastel 《第四纪科学杂志》2020,35(7):892-906
Tunnel valleys are assumed to form near the margin of ice sheets. Hence, they can be used to reconstruct the dynamics of former ice margins. The detailed formation and infill of tunnel valleys, however, are still not well understood. Here, we present a dense grid of high-resolution 2D multi-channel reflection seismic data from the German sector of the southeastern North Sea imaging tunnel valleys in very great detail. Three tunnel valley systems were traced over distances ranging between 11 and 21 km. All tunnel valleys are completely filled and buried. They differ in incision depth, incision width and number of incisions. The tunnel valleys cut 130–380 m deep into Neogene, Palaeogene and Cretaceous sediments; they show a lower V-shaped and an upper U-shaped morphology. For individual tunnel valleys, the overall incision direction ranges from east–west to northeast–southwest. Two tunnel valleys intersect at an oblique angle without reuse of the thalweg. These valleys incise into a pre-existing glaciotectonic complex consisting of thrust sheets in the northwest of the study area. The analysis of the glaciotectonic complex and the tunnel valleys leads us to assume that we identified several marginal positions of (pre-)Elsterian ice lobes in the southeastern North Sea. 相似文献
992.
近年来全球强震频发,其灾难发生的原因可能是由地磁减弱引起的。研究表明,地磁减弱的原因在于两极冰盖融化导致地壳和地幔转动惯量增大及自转减慢,由此引发核幔差异旋转在数值和方向上的改变。在磁场减弱和磁极反向过程中,太阳辐射的增强和核幔热能的释放与灾害有一一对应关系。这一研究结论与美国学者最近发现的“浅核磁场”相一致。全球变暖与地磁减弱的相关性表明,气候变暖不仅会导致海平面上升,而且会导致频繁的地震、火山活动。 相似文献
993.
SCICEX Investigations of the Arctic Ocean System 总被引:1,自引:0,他引:1
994.
995.
Associations between the autumn Arctic sea ice concentrations (SICs) and North American winter precipitation were examined using singular value decomposition. The results show that a reduced SIC in the majority of the Arctic is accompanied by dry conditions over the Great Plains, the southern United States, Mexico, eastern Alaska, and southeastern Greenland, and by wet conditions over the majority of Canada, the northeastern United States, and the majority of Greenland. Atmospheric circulation anomalies associated with the SIC variability show a wave train structure that is persistent from autumn to winter and is responsible for the covariability between the autumn Arctic SICs and North American winter precipitation. This relationship suggests a potential long-term outlook for the North American winter precipitation. 相似文献
996.
997.
l.Introducti0nTheclimateformationandvariabilityisnotonlythereflectionofatmosphericinternalbe-havi0rbutalsotheinnuencefromtheinteractionexistSintheclimatesystem.Becausetherela-tivecooIingandheatingsourcesofatmospherearelocatedinthePOlarandtropicalregionrespectively,itiseasytounderstandthattheArcticseaicecoverandSSTanomalieswhichim-pocttheatmosphericheatingtosomeextentcanexerttheirinfluenceontheremotCatmosphericcirculation-Inthisregard,thefocusrelatedtheinflueneeofArcticseaicecoverandtropica… 相似文献
998.
This paper evaluates the simulation of Arctic sea ice states using an ocean-ice coupled model that employs LASG/IAP(the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/the Institute of Atmospheric Physics) Climate Ocean Model(LICOM) and the sea-ice model from the Bergen Climate Model(BCM).It is shown that the coupled model can reasonably reproduce the major characteristics of the mean state,annual cycle,and interannual variability of the Arctic sea ice concentration.The coupled model also shows biases that were generally presented in other models,such as the underestimation of summer sea ice concentration and thickness as well as the unsatisfactory sea ice velocity.Sensitivity experiments indicate that the insufficient performance of the ocean model at high latitudes may be the main reason for the biases in the coupled model.The smoother and the fake island,which had to be used due to the model’s grid in the North Pole region,likely caused the ocean model’s weak performance.Sea ice model thermodynamics are also responsible for the sea ice simulation biases.Therefore,both the thermodynamic module of the sea ice component and the model grid of the ocean component need to be further improved. 相似文献
999.
EFFECTS OF VARIATION OF WINTER SEA-ICE AREA IN KARA AND BARENTS SEAS ON EAST ASIA WINTER MONSOON* 下载免费PDF全文
By analyzing the observation data and performing the numerical simulation tests,it is shown that the Kara and the Barents Sea area is a key region to influence climate variation over the Northern Hemisphere.The variation of winter sea-ice area in the key region is closely associated with that of the EU teleconnection pattern at 500 hPa and East Asia winter monsoon(EAWM) intensity.When a heavy sea-ice prevails in the key region,the EU teleconnection pattern at 500 hPa is excited easily(there are positive 500 hPa height anomalies over around Japan and West Europe),and winter Siberia high is weakened,meanwhile,sea level pressure(SLP) has positive anomalies over the Northern Pacific.Therefore,EAWM will be weakened,winter temperature over East Asia is above normal and the frequency of cold-air activity in February in China will be decreased.When the light sea-ice occurs in the key region,the results will be opposite. 相似文献
1000.
The growth of segregated ice lenses in frost susceptible sediments in the discontinuous permafrost zone is the dominant mechanism for the formation of permafrost mounds, such as palsas, lithalsas and permafrost plateaus. Thawing of these mounds creates thermokarst lakes, which are particularly abundant in Nunavik, east of the Hudson Bay area. The inception of the permafrost in mounds and their growth are regulated by climate conditions, by local Quaternary geology and by environmental factors such as topography, vegetation, snow cover and surface humidity. Variable sizes and morphology of the permafrost mounds can be attributed to local factors that affect the ice segregation process, particularly the supply of water needed for ice‐lens growth and grain‐size composition of the soil into which aggradation takes place. Computer image analysis of CT scans on high quality cores obtained from permafrost mounds and plateaus of various shapes reveal that the ice layer sequences and permafrost internal structure vary with landform types. A relationship therefore exists between different morphological type within a family of landforms and their microscale internal structure. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献