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101.
金矿位于哀牢山构造变质岩带、金(贵金属)成矿带南部西侧,含金石英脉分布于小新街断裂两侧的次级构造裂隙中,矿脉严格受次级压扭性断裂控制. 相似文献
102.
103.
Caroline Bouvet de Maisonneuve Olivier Bachmann Alain Burgisser 《Bulletin of Volcanology》2009,71(6):643-658
Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit,
close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau
Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly
elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy”
pumice (highly porous with large, sub-rounded vesicles), which form 5–10 vol.% of the coarsest pyroclastic flow deposits,
(2) dominantly “microvesicular” and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic
flow units, and are characterized by many small (<50 μm in diameter) vesicles and few mm-sized, irregular voids, (3) grey
or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the
eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are
compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore,
record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total
of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We
show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices
show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular,
crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation
event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in porosity,
tortuosity and permeability in compositionally identical tube and frothy pumices are the result of variable shear rates in
different parts of the conduit. Differential shear rates may be the result of either: (1) pure shear, inducing a vertical
progression from frothy to tube and implying a relatively thick fragmentation zone to produce both types of pumices at the
same time or (2) localized simple shear, inducing strongly tubular vesicles along the wall and near-spherical bubbles in the
centre of the conduit and not necessarily requiring a thick fragmentation zone. 相似文献
104.
105.
再生烃油气系统成因及全球分布 总被引:5,自引:1,他引:4
经典油气系统理论与方法主要侧重于对由烃源岩一次生烃形成的原生油气系统的研究,而对由烃源岩二次生烃或多次生烃过程所形成的特殊油气系统的研究不够。提出了再生烃油气系统的定义为:曾经有过生烃过程但因后期抬升而暂停生烃的烃源岩被再次深埋或在构造热事件的作用下,由烃源岩二次或多次生烃过程所形成的油气系统,其中的油气藏称之为再生烃油气藏。指出了再生烃油气系统的特征为:(1)具多旋回构造演化历史;(2)烃类热成熟度较高,多表现为天然气及凝析油;(3)晚期成藏;(4)油气藏规模以中小型为多,少数为大型甚至特大型;(5)油气藏分布主要受“二次生烃”或晚期生烃中心控制。对再生烃油气系统的主要形成条件进行了阐述。介绍了潜在的再生烃油气系统在中国以及全球的分布状况。 相似文献
106.
We report on a marine electromagnetic (EM) survey across two portions of the New Jersey continental margin that have been previously shown to contain buried paleo-channels. The EM method used provides bulk porosity estimates to depths of around 20 m below the seafloor and is thus able to place porosity constraints on the nature of the channel infill and the contrast in physical properties across the channel boundaries. Our data show that a key condition for the channels to have an electrical signature is that they incise an underlying regional unconformity, R, thought to represent a subaerially eroded surface, exposed during the late Wisconsinan glaciation. Channels that cut R are seen through increases in apparent porosity. Another seismically imaged channel sequence, which lies within the outer-shelf sediment wedge sequence above R, does not have an electrical signature, indicating that the sediments above and below the channel boundaries have similar physical properties. 相似文献
107.
The significance of meteorite density and porosity 总被引:2,自引:1,他引:1
Non-destructive, non-contaminating, and relatively simple procedures can be used to measure the bulk density, grain density, and porosity of meteorites. Most stony meteorites show a relatively narrow range of densities, but differences within this range can be useful indicators of the abundance and oxidation state of iron and the presence or absence of volatiles. Typically, ordinary chondrites have a porosity of just under 10%, while most carbonaceous chondrites (with notable exceptions) are more than 20% porous. Such measurements provide important clues to the nature of the physical processes that formed and evolved both the meteorites themselves and their parent bodies. When compared with the densities of small solar system bodies, one can deduce the nature of asteroid and comet interiors, which in turn reflect the accretional and collisional environment of the early solar system. 相似文献
108.
109.
A frequency domain electromagnetic (FDEM) and ground penetrating radar (GPR) study was conducted on an ephemeral stream in
north-central Texas to determine if FDEM and GPR measurements can be combined to determine the electrical characteristics
of current and ancient stream channels. GPR data were collected at several frequencies to image sedimentary structures of
different scale lengths, and to determine the formation porosity and water content of stream sediments. FDEM measurements
were collected using Geonics EM31 and EM34 loop–loop instruments on a profile along the current stream channel and five profiles
perpendicular to the channel. The results indicate that the greater spatial resolution of the EM31 mapped the current and
possible ancient channels better than the EM34, however, the EM34 provided depth information on the formations underlying
the channel sediments that the EM31 could not image. GPR measurements taken along a point bar deposit with 200, 100 and 25 MHz
antennae indicated that the higher frequency antenna better resolved channel structures including laminar bedding, trough
scours and cross-bedding, however, lower frequency antenna (25 MHz) imaged sedimentary structures within the underlying channel
sediments. Common midpoint GPR measurements collected along the point bar deposit were used to estimate the sediment formation
porosity (26%) and the water content, during a dry period, of the unsaturated (12%) and saturated (26 or 100% of the pore
space) sediments. The combined results indicated that the FDEM data should be collected first because of the speed and ease
of measurements. The FDEM data (especially the EM31) pointed to the locations of possible sedimentary structures, which can
then be resolved by using different frequency GPR measurements. 相似文献
110.
工业CT在复合材料孔隙率分析中的应用 总被引:1,自引:0,他引:1
目的:研究应用高分辨率工业CT系统对陶瓷基复合材料的孔隙率进行分析的方法,材料和方法:采用俄罗斯INDINTRO公司的BT-50高分辨工业CT系统对陶瓷基复合材料试样进行CT扫描,用自行编制的后处理软件对得到的CT图像进行分析,得出材料的孔隙率,结果:通过此方法得出的结果与超声检测结果相符,说明用高分辨率工业CT系统测定复合材料的孔隙率是可行的,同时对材料进行缺陷检测,密度分析等。 相似文献