全文获取类型
收费全文 | 380篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 17篇 |
地球物理 | 114篇 |
地质学 | 143篇 |
海洋学 | 23篇 |
天文学 | 31篇 |
综合类 | 3篇 |
自然地理 | 44篇 |
出版年
2024年 | 1篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 17篇 |
2015年 | 7篇 |
2014年 | 21篇 |
2013年 | 25篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 24篇 |
2009年 | 29篇 |
2008年 | 25篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 23篇 |
2004年 | 12篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有388条查询结果,搜索用时 15 毫秒
81.
82.
83.
An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials 总被引:2,自引:0,他引:2
Kenneth W.W. Sims James B. Gill Anthony Dosseto Dirk L. Hoffmann Craig C. Lundstrom Ross W. Williams Lary Ball Darren Tollstrup Simon Turner Julie Prytulak Justin J.G. Glessner J.J. Standish Tim Elliott 《Geostandards and Geoanalytical Research》2008,32(1):65-91
We present a concerted international effort to cross-calibrate five synthetic Th isotope reference materials (UCSC Th "A", OU Th "U", WUN, IRMM-35 and IRMM-36), and six rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2, USGS BHVO-2, LV18) using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We then compare our new values with a compilation of literature mass spectrometric data for these reference materials and derive recommended "consensus"230 Th/232 Th values for each. We also present isotope dilution U and Th concentration data for four rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2). 相似文献
84.
在剖析地域性认同双重内涵及其与土地利用关系的基础上,结合SoftGIS技术,研究构建土地利用地域性认同测度方法,并以荷兰为例进行实证分析。数据分析显示,传统GIS数据可与土地利用认知数据相融合,基于核密度修正法构建的土地利用地域性认同指数可测度地域性认同的空间差异,应用于土地利用评价或规划决策。结论表明,测度平台在问卷设计和调查空间尺度上具有灵活性,数据收集快捷,通过平台的高清卫星地图定位,调查对象可反馈空间准确、情景真实的土地利用地域性认同信息。 相似文献
85.
Mi-Kyung Yoon Mikhail Baykulov Stefan Dümmong Heinz-Jürgen Brink Dirk Gajewski 《International Journal of Earth Sciences》2008,97(5):887-898
The influence of deep crustal processes on basin formation and evolution and its relation to current morphology is not well
understood yet. A key feature to unravel these issues is a detailed seismic image of the crust. A part of the data recorded
by the hydrocarbon industry in the late 1970s and 1980s in the North German Basin were released to the public recently. The
seismic reflection data were recorded down to 15 s two-way travel time. The mean Common Midpoint fold of about 20 is relatively
low compared to contemporary seismic acquisitions. The processing of the 1980s focussed on the sedimentary structures to explore
the hydrocarbon potential of this area. We applied the Common Reflection Surface stack technique to the data sets, which is
well suited for low-fold data. The reprocessing was focussed on the imaging of the subsedimentary crustal range. The reprocessed
images show enhanced reflections, especially in the mid and lower crustal part. Also, the image of the salt structures in
the graben area was improved. Furthermore, the reprocessed images indicate an almost flat Moho topography in the area of the
Glückstadt Graben and an additional lower crustal structure, which can be correlated with a high-density body found in recent
gravity modeling studies. 相似文献
86.
Justus E. E. van Beusekom Dirk Mengedoht Christina B. Augustin Mario Schilling Maarten Boersma 《International Journal of Earth Sciences》2009,98(2):251-260
From March 2002 to until April 2003 we investigated the seasonal nutrient and phytoplankton dynamics in the central Bornholm
Basin (Baltic Sea) within the framework of the German GLOBEC Project. We choose a nested approach consisting of vertical fluorescence
profiles, phytoplankton counts and nutrient analyses. The Fluoroprobe (MultiProbe, BBE Moldaenke) is capable of distinguishing
four algal groups (Cryptophyceae, Cyanophyceae, Chlorophyceae, Bacillariophyceae + Dinophyceae). Winter nutrient concentrations
were about 5 μM NO3 and 0.5 μM PO4 in the central Basin. The spring phytoplankton bloom was dominated by the diatom Skeletonema sp. and reached a maximum of about 270 μg C/l before the onset of the seasonal stratification. Protozooplankton was dominated
by the Mesodinium rubrum (a phototrophic ciliate = Myrionecta rubra) and reached a maximum biomass of about 200–300 μg C/l about 2 weeks after the demise of the diatom spring bloom. During summer,
the water column was stratified and a subsurface maximum developed near the thermocline consisting of Bacillariophyceae, Cryptophycea
and other phototrophic flagellates. Phytoplankton and protozooplankton biomass was generally low. Nutrient concentrations
point towards a nitrogen limitation during this period. The stratification period ended during September and surface nutrient
concentrations increased again. Protozooplankton reached a second maximum during September. With the Fluoroprobe small scale
structures in the plankton community could be detected like a subsurface Cryptophyceae maximum near the thermocline that however,
could not be confirmed by cell counts. The chlorophyll a estimate of the Fluoroprobe was in good agreement with the phytoplankton
biomass estimated from counts. We conclude that only by combining modern sensing technology with microscopy, the small-scale
dynamics and taxonomic spectrum of the plankton can be fully captured. 相似文献
87.
Alberto G. Fairén Dirk Schulze-Makuch Wolfgang Fink Esther R. Uceda Ricardo Amils 《Planetary and Space Science》2009,57(3):276-318
The Mars Exploration Rover (MER) missions have confirmed aqueous activity on Mars. Here we review the analyses of the field-based MER data, and conclude that some weathering processes in Meridiani Planum and Gusev crater are better explained by late diagenetic water-rock interactions than by early diagenesis only. At Meridiani, the discovery of jarosite by MER-1 Opportunity indicates acidic aqueous activity, evaporation, and desiccation of rock materials. MER-based information, placed into the context of published data, point to local and limited aqueous activity during geologically recent times in Meridiani. Pre-Amazonian environmental changes (including important variations in the near-surface groundwater reservoirs, impact cratering, and global dust storms and other pervasive wind-related erosion) are too extreme for pulverulent jarosite to survive over extended time periods, and therefore we argue instead that jarosite deposits must have formed in a climatically more stable period. Any deposits of pre-existent concretionary jarosite surviving up to the Amazonian would not have reached completion in the highly saline and acidic brines occurring at Meridiani. MER-2 Spirit has also revealed evidence for local and limited Amazonian aqueous environmental conditions in Gusev crater, including chemical weathering leading to goethite and hematite precipitation, rock layering, and chemical enhancement of Cl, S, Br, and oxidized iron in rocks and soils. The estimated relative age of the impact crater materials in Gusev indicates that these processes have taken place during the last 2 billion years. We conclude that minor amounts of shallow acidic liquid water have been present on the surface of Mars at local scales during the Amazonian Period. 相似文献
88.
The Phoenix Lander landed on Mars on 25 May 2008. It has instruments on board to explore the geology and climate of subpolar Mars and to explore if life ever arose on Mars. Although the Phoenix mission is not a life detection mission per se, it will look for the presence of organic compounds and other evidence to support or discredit the notion of past or present life.The possibility of extant life on Mars has been raised by a reinterpretation of the Viking biology experiments [Houtkooper, J. M., Schulze-Makuch, D., 2007. A possible biogenic origin for hydrogen peroxide on Mars: the Viking results reinterpreted. International Journal of Astrobiology 6, 147-152]. The results of these experiments are in accordance with life based on a mixture of water and hydrogen peroxide instead of water. The near-surface conditions on Mars would give an evolutionary advantage to organisms employing a mixture of H2O2 and H2O in their intracellular fluid: the mixture has a low freezing point, is hygroscopic and provides a source of oxygen. The H2O2-H2O hypothesis also explains the Viking results in a logically consistent way. With regard to its compatibility with cellular contents, H2O2 is used for a variety of purposes in terran biochemistry. The ability of the anticipated organisms to withstand low temperatures and the relatively high water vapor content of the atmosphere in the Martian arctic, means that Phoenix will land in an area not inimical to H2O2-H2O-based life. Phoenix has a suite of instruments which may be able to detect the signatures of such putative organisms. 相似文献
89.
Wannes Hubau Jan Van den Bulcke Peter Kitin Florias Mees Geert Baert Dirk Verschuren Laurent Nsenga Joris Van Acker Hans Beeckman 《Quaternary Research》2013
Charcoal was sampled in four soil profiles at the Mayumbe forest boundary (DRC). Five fire events were recorded and 44 charcoal types were identified. One stratified profile yielded charcoal assemblages around 530 cal yr BP and > 43.5 cal ka BP in age. The oldest assemblage precedes the period of recorded anthropogenic burning, illustrating occasional long-term absence of fire but also natural wildfire occurrences within tropical rainforest. No other charcoal assemblages older than 2500 cal yr BP were recorded, perhaps due to bioturbation and colluvial reworking. The recorded paleofires were possibly associated with short-lived climate anomalies. Progressively dry climatic conditions since ca. 4000 cal yr BP onward did not promote paleofire occurrence until increasing seasonality affected vegetation at the end of the third millennium BP, as illustrated by a fire occurring in mature rainforest that persisted until around 2050 cal yr BP. During a drought episode coinciding with the ‘Medieval Climate Anomaly’, mature rainforest was locally replaced by woodland savanna. Charcoal remains from pioneer forest indicate that fire hampered forest regeneration after climatic drought episodes. The presence of pottery shards and oil-palm endocarps associated with two relatively recent paleofires suggests that the effects of climate variability were amplified by human activities. 相似文献
90.
Lucia Villar-Muñoz Jan H. Behrmann Juan Diaz-Naveas Dirk Klaeschen Jens Karstens 《Geo-Marine Letters》2014,34(2-3):185-198
Between 33°S and 47°S, the southern Chile forearc is affected by the subduction of the aseismic Juan Fernandez Ridge, several major oceanic fracture zones on the subducting Nazca Plate, the active Chile Ridge spreading centre, and the underthrusting Antarctic Plate. The heat flow through the forearc was estimated using the depth of the bottom simulating reflector obtained from a comprehensive database of reflection seismic profiles. On the upper and middle continental slope along the whole forearc, heat flow is about 30–60 mW m–2, a range of values common for the continental basement and overlying slope sediments. The actively deforming accretionary wedge on the lower slope, however, in places shows heat flow reaching about 90 mW m–2. This indicates that advecting pore fluids from deeper in the subduction zone may transport a substantial part of the heat there. The large size of the anomalies suggests that fluid advection and outflow at the seafloor is overall diffuse, rather than being restricted to individual fault structures or mud volcanoes and mud mounds. One large area with very high heat flow is associated with a major tectonic feature. Thus, above the subducting Chile Ridge at 46°S, values of up to 280 mW m–2 indicate that the overriding South American Plate is effectively heated by subjacent zero-age oceanic plate material. 相似文献