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551.
Yong-Kwon Koh Seon-Gyu Choi Chil-Sup So Sang-Hoon Choi Etsuo Uchida 《Mineralium Deposita》1992,27(1):58-65
The Taebaek Pb-Zn(-Ag) deposit of the Yeonhwa I mine, Republic of Korea, occurs in a broadly folded and reverse-faulted terrain of Paleozoic sedimentary rocks: the Taebaeksan basin. The orebodies consist of several thin tabular orebodies of hydrothermal replacement type where they are hosted by carbonate rocks. The Pb-Zn(-Ag) mineralization can be divided into four distinct stages based upon the mode of occurrence of ore minerals, ore textural relationships and their composition. Based on temperatures inferred from arsenopyrite compositions by means of electron microprobe and fluid inclusions, the estimated temperatures for the stages I, II, III and IV reach 330 to 350 °C, 270 to 340 °C, 230 to 250 °C, and <220 °C, respectively. The sulphur activity (atm) of ore formation at the Taebaek deposit was estimated for each stage as 10–11 to 10–11.5, 10–9.5 to 10–13, 10–13.5 to 10–15, and <10–15, respectively. Even though application of sphalerite geobarometry is problematic because of the absence of good mineral assemblages, sphalerite coexisting with pyrite but not with pyrrhotite was used to estimate the minimum mineralization pressure (about 1 kbar). 相似文献
552.
A marine magnetic survey was carried out in and around the northern part of Socotra Basin, offshore Korea (31°42′32″–32°46′29″N
and 123°56′26″–125°49′16″E), in order to better delineate its northern and eastern boundaries. Analyses of the observed magnetic
field and estimation of the basement depth were used to assess these boundaries. The power spectrum and the three-dimensional
analytical signal methods were used for depth estimation and to reconstruct basement configuration. Estimated depths resulting
from the power spectrum method range from 1.5 to 6.0 km for deep sources (basement troughs), and from 0.3 to 1.7 km for shallower
sources (basement peaks). An isopach map shows that the sedimentary sequence varies from 1.4 to 6.0 km in thickness. Estimated
depths from the analytic signal method fluctuate in the range 1.2–6 km. The results of the observed field analysis and depth
estimation indicate good agreement with the formerly proposed eastern boundary but disagreement with the northern boundary.
The findings suggest either an extension of the Socotra Basin or the existence of other sub-basins possibly interconnected
with the study area. 相似文献
553.
This study proposes a drag reduction device that uses three ribbons attached 120 degree apart to vertical pipes. Experiments were conducted in a circulating water channel to investigate the effects of the ribbon length and the direction of the flow on various current velocities. Drag on a vertical cylinder was measured by a resistance dynamometer. Flow visualizations were conducted using laser sheet beams. Laser Doppler Velocimetry (LDV) was used to measure the velocity field in the wake. This experiment demonstrates that attached ribbons can be used to reduce the drag force on vertical pipes for various directions of incoming flows. The ribbon-type device is very simple and easy to fabricate for field applications. The results are promising for the application to offshore structures. 相似文献
554.
The Bouwer and Rice method is a line-fitting method used to estimate the hydraulic conductivity of an aquifer by means of a slug test. When considering a relatively impermeable layer, called a filter cake, which may form at the interface between a cutoff wall and the natural soil formation, the assumptions of the Bouwer and Rice method are violated. A modification of the Bouwer and Rice method is proposed that incorporates the concept of a flow net, whereby the geometry of the cutoff wall and filter cake is effectively considered in estimating the hydraulic conductivity of a vertical cutoff wall. 相似文献
555.
The Haenam–Jindo area, located on the southwestern margin of the Korean Peninsula, was the site of vigorous volcanic activity during the Late Cretaceous and Early Tertiary periods. Large parts of the area record strong hydrothermal alteration, and there exist many clay–alunite and gold–silver deposits. We undertook potassium–argon (K–Ar) age dating of five mineral samples (including adularia, sericite and alunite) from the Eunsan, Moisan and Gasado epithermal gold–silver deposits in this area. The purities of the samples were confirmed by X‐ray diffraction analysis. The K–Ar ages of adularia from the Eunsan deposit and adularia and sericite from the Moisan deposit (related to gold–silver mineralization) are 75.0 ± 1.6, 74.7 ± 1.6 and 75.1 ± 1.6 Ma, respectively. The similarity of these ages, combined with the close proximity and similar geochemical characteristics of the deposits, indicates that the mineralization occurred as part of a single hydrothermal system. The K–Ar ages of alunite at the surface and adularia at depth within the Gasado deposit are 82.2 ± 1.9 and 70.7 ± 1.9 Ma, respectively, revealing that the clay–alunite and gold–silver mineralization formed at different ages. K–Ar age data indicate that the gold–silver mineralization in this area occurred mainly at 75–70 Ma, resulting from hydrothermal activity in the Haenam–Jindo area (82–70 Ma). This is the first time that the mineralization of precious metals in Korea has been identified during this period. 相似文献
556.
In order to account for the effects of elastic wave propagation in marine seismic data, we develop a waveform inversion algorithm for acoustic‐elastic media based on a frequency‐domain finite‐element modelling technique. In our algorithm we minimize residuals using the conjugate gradient method, which back‐propagates the errors using reverse time migration without directly computing the partial derivative wavefields. Unlike a purely acoustic or purely elastic inversion algorithm, the Green's function matrix for our acoustic‐elastic algorithm is asymmetric. We are nonetheless able to achieve computational efficiency using modern numerical methods. Numerical examples show that our coupled inversion algorithm produces better velocity models than a purely acoustic inversion algorithm in a wide variety of cases, including both single‐ and multi‐component data and low‐cut filtered data. We also show that our algorithm performs at least equally well on real field data gathered in the Korean continental shelf. 相似文献
557.
A new study investigates an unburied offshore “snaked” pipeline behavior under various types of seismic faults. The snaking of the pipeline is caused by the thermal/pressure expansion and soil friction. The snaking takes place at a certain distance from the pipeline's unrestrained end and gradually increases towards the restraint. It is shown that longitudinal seismic faults have less effect on a straight pipeline than a snaked pipeline. The new seismic analysis demonstrates that an increase of ground displacement causes a very small change in bending and longitudinal stresses. The new approach results in a safe, subsea pipeline construction and operation with a significant cost reduction. 相似文献
558.
559.
An acoustic laboratory experiment using 5-MHz signals was conducted to measure the volume backscattering strengths of red-tide causing microalgae, Chattonella antiqua, which is one of the species of harmful algal blooms in the coastal waters of Korea and Japan. The measured backscattering strengths increased with cell abundance, with a slope of approximately 10 dB per decade increase in cell numbers. The density and sound speed ratios of the Chattonella cell to the water medium were estimated via the density gradient centrifugation method and the time-travel difference method, respectively. Finally, the measured backscattering strengths were compared to those predicted by a fluid-sphere scattering model, in which the estimated sound speed and density contrasts were used as input parameters. 相似文献
560.
Characterizing the effect of heavy metal contamination on marine mussels using metabolomics 总被引:1,自引:0,他引:1
Marine mussels (Mytilus) are widely used as bioindicators to measure pollution in marine environments. In this study, (1)H NMR spectroscopy and multivariate statistical analyses were used to differentiate mussel groups from a heavy metal-polluted area (Onsan Bay) and a clean area (Dokdo area). Principal component analysis and orthogonal projection to latent structure-discriminant analysis revealed significant separation between extracts of mussels from Onsan Bay and from the Dokdo area. Organic osmolytes (betaine and taurine) and free amino acids (alanine, arginine, glutamine, phenylalanine, and threonine) were more highly accumulated in Onsan Bay mussels compared with Dokdo mussels. These results demonstrate that NMR-based metabolomics can be used as an efficient method for characterizing heavy metal contamination derived from polluted area compared to clean area and to identify metabolites related to environments that are contaminated with heavy metals. 相似文献