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961.
Computer simulation of coastal acoustic tomography with four, five, seven and nine stations was applied to two-dimensional
vortex fields of horizontal domain 5 km × 5 km. Travel time data obtained in reciprocal directions between all pairs of acoustic
stations were analyzed to reconstruct the vortex fields by the stochastic inverse method, reduced to the damped least squares
method. The weighting factor appearing in the inverse analysis was determined by applying the L-curve method, in which a point
making both the size of estimated error ‖y - Ex‖ and solution ‖x‖ as small as possible in a balance is specified as an optimum.
The performance of this method was examined using two-dimensional vortex models which have different wavenumber spectra and
adding the random error of different levels to the travel time difference data y. This study suggests that in the selection
of the optimal weighting factor the horizontal section of the simulated tidal vortex fields can be well reconstructed by the
coastal acoustic tomography system composed of five to seven acoustic stations located in the periphery of the vortex fields.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
962.
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
963.
Clay minerals of the surface sediments of Bransfield Strait, Antarctica, exhibit distinctive geographical distributions: kaolinite has the highest concentration near the shore of the South Shetland Islands in the northern strait (20%); chlorite, near Smith Island in the northwestern strait; illite, on the continental shelf off the Antarctic Peninsula in the southern strait (80%); and smectite, close to the Penguin and Bridgeman islands in the northeastern strait (25%). This distribution pattern, combined with hydrographic and climatic data for the strait, are used to infer clay mineral provenance and dispersal patterns. 相似文献
964.
Synoptic distributions of thermal surface mixed layer and thermocline were identified using four airborne expendable bathythermograph
(AXBT) surveys (September 1992 and February, May, and September 1993) in the southern Yellow and East China Seas. Seasonality
and a dominant driving mechanism of the surface mixed layer were examined. The dominant driving mechanisms differ between
seasons and between on-shelf and off-shelf regimes. Currents, eddies, and migration of bottom cold waters (on the shelf) also
affect the surface mixed layer. Thermocline thickness, temperature difference from thermocline top to bottom, and thermocline
intensity in warm seasons were measured, and their synoptic features were also discussed. 相似文献
965.
Jung-Suk Lee Kyu-Tae Lee Dong-Hoon Kim Chan-Kook Kim Jong-Hyeon Lee Kun-Ho Park Gyung-Soo Park 《Ocean Science Journal》2005,40(1):17-24
A series of experiments were conducted to develop standard test organisms and test protocols for measuring sediment toxicity
using candidate amphipods such asMandibulophoxus mai, Monocorophium acherusicum, Haustorioides indivisus, andHaustorioides koreanus, which are indigenous to Korea. The relevant association of test species with sediment substrates was one of the important
factors in sediment bioassay. The indigenous amphipodsM. mai andM. acherusicum were well associated with test sediments when they were exposed to various sediment substrates from sand to mud. The tolerant
limits to various physico-chemical factors affecting bioassay results such as temperature, salinity and ammonia, as well as
sensitivities to reference toxicant and contaminated sediments, were investigated usingM. mai andM. acherusicum in the present study. These amphipods were tolerant to relatively wide ranges of salinity (10~30 psu) and ammonia (<50 ppm),
and displayed relevant sensitivity to temperature as well. They are more sensitive to Cd, the reference toxicant, when compared
to the standard test species used in other countries. Field-sediment toxicity tests revealed thatM. mai would be more sensitive to sediment-associated pollutants thanM. acherusicum, while the sensitivity ofM. acherusicum was comparable to that ofLeptocheirus plumulosus, which has been used as a standard test species in the United States of America. Overall results of this first attempt to
develop an amphipod sediment toxicity test protocol in Korea indicated thatM. mai andM. acherusicum would be applicable in the toxicity assessment of contaminated sediments, following the further evaluation encompassing various
ecological and toxicological studies in addition to test method standardization. 相似文献
966.
Gyesoon Park Seokhoon Oh Heuisoon Lee Jung-Ho Kim Byung-Doo Kwon 《Journal of Applied Geophysics》2011,73(3):232-242
To enhance the spatial resolution, two types of complementary integration methods were developed using gravity and magnetotelluric (MT) data. The first method involves the enhancement processing of gravity vertical resolution using MT data. This is called a layer density correction (LDC) process which makes the density distribution more sensitive to geologic structure. The second method involves the spatial expansion processing of MT data using the enhanced gravity data. In this process, non-linear indicator transformation (NLIT) and simple kriging with varying local means (SKlm) methods were employed. The assumptions are that while the results are analyzed by different physical properties, each method senses the same underlying geologic structure and thus there is a relationship among the physical properties. The proposed geostatistical integration methods were tested using synthetic models and field data. The experiment illustrates that the integration method proposed in this study can provide improved structures. The method integrates constructively the gravity information having a wider spatial distribution and the MT information having higher vertical resolution. 相似文献
967.
Ki-Young Heo Jeong-Wook Lee Kyung-Ja Ha Ki-Cheon Jun Kwang-Soon Park Jae-Il Kwon 《Natural Hazards》2009,51(1):151-162
High-quality informations on sea level pressure and sea surface wind stress are required to accurately predict storm surges
over the Korean Peninsula. The storm surge on 31 March 2007 at Yeonggwang, on the western coast, was an abrupt response to
mesocyclone development. In the present study, we attempted to obtain reliable surface winds and sea level pressures. Using
an optimal physical parameterization for wind conditions, MM5, WRF and COAMPS were used to simulate the atmospheric states
that accompanied the storm surge. The use of MM5, WRF and COAMPS simulations indicated the development of high winds in the
strong pressure gradient due to an anticyclone and a mesocyclone in the southern part of the western coast. The response to
this situation to the storm surge was sensitive. A low-level warm advection was examined as a possible causal mechanism for
the development of a mesocyclone in the generating storm surge. The low-level warm temperature advection was simulated using
the three models, but MM5 and WRF tended to underestimate the warm tongue and overestimate the wind speed. The WRF simulation
was closer to the observed data than the other simulations in terms of wind speed and the intensity of the mesocyclone. It
can be concluded that the magnitude of the storm surge at Yeonggwang was dependent, not only on the development of a mesocyclone
but on ocean effects as well. 相似文献
968.
The rapid intensification of Hurricane Charley (2004) near landfall is studied using the fifth-generation Pennsylvania State
University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model (MM5) and its adjoint system for both vortex
initialization and forecasts. A significant improvement in both track and intensity forecasts is achieved after an ill-defined
storm vortex, derived from large-scale analysis, in the initial condition is replaced by the vortex generated by a four-dimensional
data variational (4D-Var) hurricane initialization scheme. Results from numerical experiments suggest that both the inclusion
of the upper-level trough and the use of high horizontal resolution (6 km) are important for numerical simulations to capture
the observed rapid intensification as well as the size reduction during the rapid intensification of Hurricane Charley. The
approach of the upper-level trough significantly enhanced the upper-level divergence and vertical motion within simulated
hurricanes. Small-scale features that are not resolvable at 18 km resolution are important to the rapid intensification and
shrinking of Hurricane Charley (2004). Numerical results from this study further confirm that the theoretical relationship
between the intensification and shrinking of tropical cyclones based on the angular momentum conservation and the cyclostrophic
approximation can be applied to the azimuthal mean flows. 相似文献
969.
Toshihiro Ike Gregory F. Moore Shin'ichi Kuramoto Jin-Oh Park Yoshiyuki Kaneda Asahiko Taira 《Island Arc》2008,17(3):342-357
Abstract We documented regional and local variations in basement relief, sediment thickness, and sediment type in the Shikoku Basin, northern Philippine Sea Plate, which is subducting at the Nankai Trough. Seismic reflection data, tied with ocean drilling program drill cores, reveal that variations in the incoming sediment sequences are correlated with basement topography. We mapped the three-dimensional seismic facies distribution and measured representative seismic sequences and units. Trench-parallel seismic profiles show three regional provinces in the Shikoku Basin that are distinguished by the magnitude of basement relief and sediment thickness: Western (<200–400 m basement relief, >600 m sediment thickness), Central (>1500 m relief, ∼2000 m sediments), and Eastern (<600 m relief, ∼1200 m sediments) provinces. The total thickness of sediment in basement lows is as much as six times greater than that over basement highs. Turbidite sedimentation in the Shikoku Basin reflects basement control on deposition, leading to the local presence or absence of turbidite units deposited during the middle Oligocene to the middle Miocene. During the first phase of sedimentation, most basement lows were filled with turbidites, resulting in smooth seafloor morphology that does not reflect basement relief. A second phase of turbidite deposition in the Eastern Province was accompanied by significant amounts of hemipelagic sediments interbedded with turbidite layers compared to the other provinces because of its close proximity to the Izu–Bonin Island Arc. Both regional and local variations in basement topography and sediment thickness/type have caused lateral heterogeneities on the underthrusting plate that will, in turn, influence lateral fluid flow along the Nankai accretionary prism. 相似文献
970.
Kasemsan Manomaiphiboon Sun-Kyoung Park Armistead G. Russell 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(2):159-168
Probabilistic characterization of environmental variables or data typically involves distributional fitting. Correlations,
when present in variables or data, can considerably complicate the fitting process. In this work, effects of high-order correlations
on distributional fitting were examined, and how they are technically accounted for was described using two multi-dimensional
formulation methods: maximum entropy (ME) and Koehler–Symanowski (KS). The ME method formulates a least-biased distribution
by maximizing its entropy, and the KS method uses a formulation that conserves specified marginal distributions. Two bivariate
environmental data sets, ambient particulate matter and water quality, were chosen for illustration and discussion. Three
metrics (log-likelihood function, root-mean-square error, and bivariate Kolmogorov–Smirnov statistic) were used to evaluate
distributional fit. Bootstrap confidence intervals were also employed to help inspect the degree of agreement between distributional
and sample moments. It is shown that both methods are capable of fitting the data well and have the potential for practical
use. The KS distributions were found to be of good quality, and using the maximum likelihood method for the parameter estimation
of a KS distribution is computationally efficient. 相似文献