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61.
62.
Groundwater surveys were performed by detailed(around 300 sites) grid-analysis of water temperature, pH, redox potential, electrical conductivity, 222Rn, alkalinity and by calculating the pCO2, throughout the Ciampino and Marino towns in the Alban Hills quiescent volcano (Central Italy). Following several episodes of dangerous CO2 exhalation from soils during the last 20 years and earlier ashistorically recorded, the work aimed at assessing the Natural Gas Hazard (NGH) including the indoor-Rn hazard. The NGH was defined as the probability of an area to become a site of poisonous peri-volcanic gas exhalations from soils to the lower atmosphere (comprising buildings). CO2 was found to be a ``carrier' for the other poisonous minor and in trace components (HsS, CH4, 222Rn, etc.). This assessment was performed by extrapolating in the aquifer CO2 and 222Rn conditions, and discriminating sectors where future CO2 flux in soils as well as indoor-Rn measurements have to be noted. A preliminary indoor-Rn survey was performed at about 200 sites. The highest values were found in the highest pCO2 and high 222Rn values in groundwater. This indicates convection and enhanced permeability in certain sectors of the main aquifer, i.e., along the bordering faults and inside the gas-trap of the Ciampino Horst., where ``continuous gas-phase micro-macro seepage mechanism' is invoked to explain the high peri-volcanic gases flux. 相似文献
63.
结合三维建模和电子地图的基本理论,根据地质公园的特点,利用ERDAS实现大面积区域三维可视化,并结合3DS MAX丰富的建模技术及强大的动画制作功能,在地质景观演化方面做了初步探讨。采用“超地图”的形式来组织各种地图数据以及超媒体相关信息,从内容结构设计及特点进行论述,实现了伊通火山群的三维电子地图,展示出“伊通型火山”的特点。为科研、科普和旅游提供了方便、直观的信息表现形式,拓宽了电子地图的应用领域,同时也丰富了电子地图的研究内容。 相似文献
64.
Jean -Luc Got Vadim Monteiller Jean Virieux Paul Okubo 《Pure and Applied Geophysics》2006,163(2-3):405-430
Seismic velocity parameters in limited, but heterogeneous volumes can be inferred using a double-difference tomographic algorithm,
but to obtain meaningful results accuracy must be maintained at every step of the computation. MONTEILLER et al. (2005) have devised a double-difference tomographic algorithm that takes full advantage of the accuracy of cross-spectral
time-delays of large correlated event sets. This algorithm performs an accurate computation of theoretical travel-time delays
in heterogeneous media and applies a suitable inversion scheme based on optimization theory. When applied to Kilauea Volcano,
in Hawaii, the double-difference tomography approach shows significant and coherent changes to the velocity model in the well-resolved
volumes beneath the Kilauea caldera and the upper east rift. In this paper, we first compare the results obtained using MONTEILLER
et al.'s algorithm with those obtained using the classic travel-time tomographic approach. Then, we evaluated the effect of using
data series of different accuracies, such as handpicked arrival-time differences (``picking differences'), on the results
produced by double-difference tomographic algorithms. We show that picking differences have a non-Gaussian probability density
function (pdf). Using a hyperbolic secant pdf instead of a Gaussian pdf allows improvement of the double-difference tomographic
result when using picking difference data. We completed our study by investigating the use of spatially discontinuous time-delay
data. 相似文献
65.
"琼北火山探查及喷发危险性研究"项目成果介绍 总被引:2,自引:0,他引:2
本文详细介绍了"火山灾害预警研究"项目的立项背景、目标、所开展的主要工作、取得的成果、研究成果的社会效益和对该领域研究未来工作的展望。 相似文献
66.
K. Garofalo F. Tassi O. Vaselli A. Delgado-Huertas D. Tedesco M. Frische T. H. Hansteen R. J. Poreda W. Strauch 《Bulletin of Volcanology》2007,69(7):785-795
Mombacho is a deeply dissected volcano belonging to the Quaternary volcanic chain of Nicaragua. The southern, historic collapse
crater (El Crater) currently hosts a fumarolic field with a maximum temperature of 121°C. Chemical and isotopic data from
five gas-sampling field campaigns carried out in 2002, 2003 and 2005 highlight the presence of high-temperature gas components
(e.g. SO2, HCl and HF), which indicate a significant contribution of juvenile magmatic fluids to the hydrothermal system feeding the
gas discharges. This is strongly supported by the mantle-derived helium and carbon isotopic signatures, although the latter
is partly masked by either a sedimentary subduction-related or a shallow carbonate component. The observed chemical and isotopic
composition of the Mombacho fluids seems to indicate that this volcanic system, although it has not experienced eruptive events
during the last centuries, can be considered active and possibly dangerous, in agreement with the geophysical data recorded
in the region. Systematic geochemical monitoring of the fumarolic gas discharges, coupled with a seismic and ground deformation
network, is highly recommended in order to monitor a possible new eruptive phase. 相似文献
67.
Adam Carter Benjamin van Wyk de Vries Karim Kelfoun Patrick Bachèlery Pierre Briole 《Bulletin of Volcanology》2007,69(7):741-756
A clear model of structures and associated stress fields of a volcano can provide a framework in which to study and monitor
activity. We propose a volcano-tectonic model for the dynamics of the summit of Piton de la Fournaise (La Reunion Island,
Indian Ocean). The summit contains two main pit crater structures (Dolomieu and Bory), two active rift zones, and a slumping
eastern sector, all of which contribute to the actual fracture system. Dolomieu has developed over 100 years by sudden large
collapse events and subsequent smaller drops that include terrace formation. Small intra-pit collapse scars and eruptive fissures
are located along the southern floor of Dolomieu. The western pit wall of Dolomieu has a superficial inward dipping normal
fault boundary connected to a deeper ring fault system. Outside Dolomieu, an oval extension zone containing sub-parallel pit-related
fractures extends to a maximum distance of 225 m from the pit. At the summit the main trend for eruptive fissures is N80°,
normal to the north–south rift zone. The terraced structure of Dolomieu has been reproduced by analogue models with a roof
to width ratio of approximately 1, suggesting an original magma chamber depth of about 1 km. Such a chamber may continue to
act as a storage location today. The east flank has a convex–concave profile and is bounded by strike-slip fractures that
define a gravity slump. This zone is bound to the north by strike-slip fractures that may delineate a shear zone. The southern
reciprocal shear zone is probably marked by an alignment of large scoria cones and is hidden by recent aa lavas. The slump
head intersects Dolomieu pit and may slide on a hydrothermally altered layer known to be located at a depth of around 300 m.
Our model has the summit activity controlled by the pit crater collapse structure, not the rifts. The rifts become important
on the mid-flanks of the cone, away from pit-related fractures. On the east flank the superficial structures are controlled
by the slump. We suggest that during pit subsidence intra-pit eruptions may occur. During tumescence, however, the pit system
may become blocked and a flank eruption is more likely. Intrusions along the rift may cause deformation that subsequently
increases the slump’s potential to deform. Conversely, slumping may influence the east flank stress distribution and locally
control intrusion direction. These predictions can be tested with monitoring data to validate the model and, eventually, improve
monitoring. 相似文献
68.
The magma evolution of Tianchi volcano, Changbaishan 总被引:4,自引:0,他引:4
The Changbaishan Tianchi volcano is composed of the basaltic rocks at the shield-forming stage, the trachyte and pantellerite
at the cone-forming stage and modern eruption. Studies on their REE, incompatible elements and Sr, Nd, Pb isotopes suggest
that rocks at different stages have a common magma genesis and close evolution relationship with differentiation crystallization
playing the key role. The co-eruption of basaltic trachyandesite magma and pantellerite magma indicates that there exist both
crustal magma chamber and mantle magma reservoir beneath the Tianchi volcano.
Project supported by the National Natural Science Foundation of China (Grant No. 49672109). 相似文献
69.
腾冲火山活动监测,预测与对策研究中的若干重要问题 总被引:2,自引:1,他引:1
《膳冲火山活动监测、预测与对策研究》项目是一项集火山活动监测研究、防灾及资源综合开发与利用为一体的系统工程。需要火山地质、地震、地球化学、地球物理、地壳形变及地热等诸多相关学科的合理配置和联合攻关。在过去的30年,众多学和研究实体对腾冲火山进行 大量的观察和研究获得一批与火山活动的相关的基础研究成果。其中也不乏说明腾冲火山存在在喷发危险性的证据。为了保证本重大项目能在有限时间内及有限的人力、财务 相似文献
70.