全文获取类型
收费全文 | 476篇 |
免费 | 16篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 21篇 |
大气科学 | 26篇 |
地球物理 | 122篇 |
地质学 | 185篇 |
海洋学 | 26篇 |
天文学 | 83篇 |
综合类 | 6篇 |
自然地理 | 32篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 21篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 20篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 21篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有501条查询结果,搜索用时 31 毫秒
401.
Ralf Halama Khachatur Meliksetian Ivan P. Savov Patrick J. Sugden Krzysztof Sokół 《Geology Today》2020,36(3):101-108
Located in the heart of the Lesser Caucasus mountains, where the Arabian and Eurasian tectonic plates collide, Armenia occupies an exceptional geological position shaped through millions of years of subduction and collision. It is a unique place on the Earth recording extensive intrusive and volcanic activity related to the long-standing continental convergence. The volcanoes of Armenia provide a rare opportunity to study the sources and processes involved in this unusual type of magmatism. More than 500 Quaternary volcanoes have been mapped in Armenia, most of them formed from single eruptive episodes. Among several large composite volcanoes, the mighty Aragats stands out as the largest volcano in Armenia and the region altogether. Volcanic deposits testify to the range of eruptive styles—from the ignimbrites formed in eruptions as explosive and voluminous as any seen globally in the modern era to the enormous fissure-fed lava flows that form the Southern Caucasus flood basalt province, the smallest and youngest Large Igneous Province in the world. Several pre-historical and historical eruptions have been documented, highlighting the potential for future volcanic activity in the region. In recent years, research has focused on the volcanic hazards associated with the Armenian Nuclear Power Plant, located in the foothills of Aragats volcano. This article highlights some of the extraordinary volcanic and intrusive features observed in Armenia and summarizes aspects of recent volcanological and petrological research. 相似文献
402.
X-ray fluorescence scanning with synchrotron radiation was performed to study sediment core records of floods in Amur Bay,Sea of Japan.Interlayers of 3–8 mm with abnormally low bromine content were formed by the Razdolnaya River discharge to the central part of the bay during extreme floods,accompanied by severe storms at sea.Such conditions in the region are typical for periods of deep tropical cyclones(typhoons),to which the distinguished interlayers were compared on the timescale.This approach was made possible thanks to the high rate of sedimentation in the bay(3–5 mm/a) and low bioturbation of sediments under anoxic conditions. 相似文献
403.
Axel Wittmann Randy L. Korotev Bradley L. Jolliff Anthony J. Irving Desmond E. Moser Ivan Barker Douglas Rumble III 《Meteoritics & planetary science》2015,50(2):326-352
The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7–1.4 Ga, and a third that launched NWA 7475 from Mars ~5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock‐heating that resulted from these shock pressures would have been insufficient to sterilize this water‐bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium‐carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma‐ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of ~5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475. 相似文献
404.
Cosmogenic nuclides in the Košice meteorite: Experimental investigations and Monte Carlo simulations
下载免费PDF全文
![点击此处可从《Meteoritics & planetary science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pavel P. Povinec Jozef Masarik Ivan Sýkora Andrej Kováčik Juraj Beňo Matthias M. M. Meier Rainer Wieler Matthias Laubenstein Vladimir Porubčan 《Meteoritics & planetary science》2015,50(5):880-892
Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides (7Be, 22Na, 26Al, 46Sc, 48V, 54Mn, 56Co, 57Co, 58Co, and 60Co) in 19 fragments of the Ko?ice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic‐ray particles in the space affecting radionuclides with different half‐lives. Monte Carlo simulations of the production rates of 60Co and 26Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Ko?ice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Ko?ice meteorite is 5–7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Ko?ice is a regolith breccia. The agreement between the simulated and observed 26Al activities indicate that the meteoroid was mostly irradiated by a long‐term average flux of galactic cosmic rays of 4.8 particles cm?2 s?1, whereas the short‐lived radionuclide activities are more consistent with a flux of 7.0 protons cm?2 s?1 as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall. 相似文献
405.
406.
407.
Marian Ivan 《Journal of Seismology》2011,15(2):317-328
Crustal thickness (CT) in Vrancea region (Romania) and adjacent area is investigated using 1294 S to P converted waves from
the Moho discontinuity. A total of 269 local earthquakes in the depth range 99.8 to 171.1 km and recorded by 76 permanent
and 46 temporary stations of the Romanian Seismological Network are used. Time difference between the converted wave and the
direct P phase is corrected to a first order for epicentral distance and for the errors in focal depth, being finally inverted
to CT. Greatest values for the Moho depth are observed for stations located in the Carpathians molasse foredeep and smaller
values are observed in the Southern part of the Moesian Platform, for stations in the eastern part of Moldavian (East-European)
Platform and in Dobrogea area, close to the Black Sea shoreline. In Vrancea epicentral area, an important CT variation is
observed, from 42 km at MLR and 41.8 km at SIR, stations placed in the south-western part of the epicentral area, to 30.9 km
at VRI, located above north-eastern part of the seismogenic volume. Stations CVO and OZU, placed in Transylvanian Basin in
the proximity of the epicentral area, have CT values of 32.1 and 24.1 km, respectively. The results seem to support that a
mantle delamination process is responsible for Vrancea intermediate depth seismicity. 相似文献
408.
The 2007 Chuetsu Oki earthquake (MJMA = 6.6) triggered more than one hundred slope failures in the northwest part of Niigata prefecture, Japan. A reconnaissance
survey conducted by the authors revealed that although most of the failures were only a few meters deep, they still caused
significant damage to roads, railways, and houses. It was also found that a vast number of shallow slides were concentrated
along the coastal line of the Japan Sea, while only few, but relatively larger failures occurred in a mountainous part of
the study area, which is located in a considerable distance from the earthquake’s epicenter. This paper summarizes the reconnaissance
observations, describes the geologic characteristics of the area covered by landslides, provides characterization of major
types of the landslides, and examines the causes and mechanisms of typical failures. In addition, this paper seeks to investigate
the mechanism of the Ohzumi landslide, the largest slide triggered by the Chuetsu Oki earthquake. For this purpose, a comprehensive
analysis that included field investigation and laboratory testing of soils samples was performed. Results of field investigation
suggested that the failure plane of the Ohzumi landslide formed in a saturated layer of sandy soil near a boundary with bedrock.
Data from undrained cyclic loading triaxial compression tests indicated that the sandy material was highly susceptible to
generation of high excess pore-water pressures during earthquake loading. On the basis of the obtained results and the outcome
of seismic response and slope stability analyses, the authors posited an explanation on the mechanism of the Ohzumi landslide. 相似文献
409.
The relationship of soil gas radon Rn222 and indoor radon was studied within the Quaternary fluvial sediments of the Czech Republic. The processing of data selection
from the radon database of the Czech Geological Survey and indoor radon data (database of the National Radiation Protection
institute) has proved the concentration dependence of radon in Quaternary fluvial sediments on deeper bedrock. The ArcGIS
processing was accompanied by the field verification in five profiles, intersecting the granitoid Central Bohemian Plutonic
Complex and its rim rock types. Both theoretical and experimental results show dependence of soil gas radon and indoor radon
concentrations in Quaternary fluvial sediments on deeper geological basement, thus leading to the conclusion that the lateral
transport of Quaternary sediments does not play such a dominant role in radon concentrations, as was thought previously. This
fact will enable to determine precisely the radon index of Quaternary sediments (in the Czech radon mapping classified as
an intermediate index) into three categories according to the lithology of their geological basement. 相似文献
410.
Horsburgh Kevin Haigh Ivan D. Williams Jane De Dominicis Michela Wolf Judith Inayatillah Addina Byrne David 《Ocean Dynamics》2021,71(6-7):715-730
Ocean Dynamics - In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels... 相似文献