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   71308篇
  免费   1130篇
  国内免费   659篇
测绘学   1714篇
大气科学   5031篇
地球物理   14230篇
地质学   25250篇
海洋学   6187篇
天文学   16342篇
综合类   210篇
自然地理   4133篇
  2022年   396篇
  2021年   704篇
  2020年   777篇
  2019年   825篇
  2018年   1896篇
  2017年   1763篇
  2016年   2240篇
  2015年   1320篇
  2014年   2178篇
  2013年   3771篇
  2012年   2279篇
  2011年   3125篇
  2010年   2608篇
  2009年   3508篇
  2008年   3256篇
  2007年   3052篇
  2006年   2878篇
  2005年   2355篇
  2004年   2259篇
  2003年   2115篇
  2002年   1932篇
  2001年   1802篇
  2000年   1718篇
  1999年   1379篇
  1998年   1470篇
  1997年   1387篇
  1996年   1102篇
  1995年   1142篇
  1994年   962篇
  1993年   872篇
  1992年   856篇
  1991年   759篇
  1990年   856篇
  1989年   718篇
  1988年   650篇
  1987年   815篇
  1986年   664篇
  1985年   856篇
  1984年   923篇
  1983年   862篇
  1982年   831篇
  1981年   707篇
  1980年   663篇
  1979年   606篇
  1978年   603篇
  1977年   552篇
  1976年   539篇
  1975年   499篇
  1974年   506篇
  1973年   469篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
371.
Natural Resources Research - Identification of geochemical anomalies is of particular importance for tracing the footprints of anomalies. This can be implemented by advanced techniques of...  相似文献   
372.
373.
The onset of the confinement transition in the early universe is studied within the Friedmann model. Exploiting a bag model equation of state for the deconfined matter, which is generalized to include also metastable states, the possibility of a mini-inflationary epoch is demonstrated. A criterion of metastability is derived to estimate parameters of this mini-inflation.  相似文献   
374.
375.
376.
Strain style, magnitude and distribution within mass‐transport complexes (MTCs) are important for understanding the process evolution of submarine mass flows and for estimating their runout distances. Structural restoration and quantification of strain in gravitationally driven passive margins have been shown to approximately balance between updip extensional and downdip contractional domains; such an exercise has not yet been attempted for MTCs. We here interpret and structurally restore a shallowly buried (c. 1,500 mbsf) and well‐imaged MTC, offshore Uruguay using a high‐resolution (12.5 m vertical and 15 × 12.5 m horizontal resolution) three‐dimensional seismic‐reflection survey. This allows us to characterise and quantify vertical and lateral strain distribution within the deposit. Detailed seismic mapping and attribute analysis shows that the MTC is characterised by a complicated array of kinematic indicators, which vary spatially in style and concentration. Seismic‐attribute extractions reveal several previously undocumented fabrics preserved in the MTC, including internal shearing in the form of sub‐orthogonal shear zones, and fold‐thrust systems within the basal shear zone beneath rafted‐blocks. These features suggest multiple transport directions and phases of flow during emplacement. The MTC is characterised by a broadly tripartite strain distribution, with extensional (e.g. normal faults), translational and contractional (e.g. folds and thrusts) domains, along with a radial frontally emergent zone. We also show how strain is preferentially concentrated around intra‐MTC rafted‐blocks due to their kinematic interactions with the underlying basal shear zone. Overall, and even when volume loss within the frontally emergent zone is included, a strain difference between extension (1.6–1.9 km) and contraction (6.7–7.3 km) is calculated. We attribute this to a combination of distributed, sub‐seismic, ‘cryptic’ strain, likely related to de‐watering, grain‐scale deformation and related changes in bulk sediment volume. This work has implications for assessing MTCs strain distribution and provides a practical approach for evaluating structural interpretations within such deposits.  相似文献   
377.
Natural Resources Research - Oil shale impurities prevent its direct usage as a source of energy. Removing or reducing of these impurities before retorting can reduce the cost of oil shale...  相似文献   
378.
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   
379.
Izvestiya, Atmospheric and Oceanic Physics - On the basis of a parametrization of the ionospheric potential (IP), the seasonal dynamics of the diurnal IP variation for 2016–2017 is simulated...  相似文献   
380.
The Lynton Beds represent shallow marine sediments with a restricted fauna dominated by brachiopods. The age indicated by the brachiopod fauna is late Emsian, although the possibility of a younger date for the uppermost horizons cannot be discounted.  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