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271.
Jin Koo Kim Jeong -Ho Park Jung Hwa Choi Kwang Ho Choi Yeong Min Choi Dae Soo Chang Young Seop Kim 《Ocean Science Journal》2007,42(2):61-67
Three barracudina fishes (Paralepididae) were newly recorded from the southern sea of Korea. Lestidium prolixum is characterized
by a single band of luminous ducts on the midventral line and absence of a papilla anterior to the eye. Lestrolepis intermedia
and L. japonica are similar in having a black papilla immediately in front of the eye and two bands of luminous ducts on the
midventral line. However, the dorsal fin of L. intermedia is located more posterior along the body than that of L. japonica,
and L. intermedia have larger number of anal fin rays 42 (vs. 36–40) and vertebrae 95 (vs. 86–87) than L. japonica. 相似文献
272.
The Ieodo Ocean Research Station(IORS) is an integrated meteorological and oceanographic observation base which was constructed
on the Ieodo underwater rock located at a distance of about 150 km to the south-west of the Mara-do, the southernmost island
in Korea. The underwater ambient noise level observed at the IORS was similar to the results of the shallow water surrounding
the Korean Peninsula (Choi et al. 2003) and was higher than that of deep ocean (Wenz 1962). The wind dependence of ambient
noise was dominant at frequencies of a few kHz. The surface current dependence of ambient noise showed good correlation with
the ambient noise in the frequency of 10 kHz. Especially, the shrimp sound was estimated through investigations of waveform
and spectrum and its main acoustic energy was about 40 dB larger than ambient noise level at 5 kHz. 相似文献
273.
Bok Kyoung Choi Bong -Chae Kim Byoung -Nam Kim Suk Wang Yoon 《Ocean Science Journal》2006,41(4):195-199
Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water.
Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125–130 (2001)]
reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation.
It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results
of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement
with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing
in the ocean. 相似文献
274.
With the implementation of the Jason-1 satellite altimeter mission, the goal of reaching the 1-cm level in orbit accuracy was set. To support the Precision Orbit Determination (POD) requirements, the Jason-1 spacecraft carries receivers for DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) and GPS (Global Positioning System), as well as a retroreflector for SLR (Satellite Laser Ranging). The overall orbit accuracy for Jason will depend on the quality and the relative weighting of the available tracking data. In this study, the relative importance of the SLR, DORIS, and GPS tracking data is assessed along with the most effective parameterization for accounting for the unmodeled accelerations through the application of empirical accelerations. The optimal relative weighting for each type of tracking data was examined. It is demonstrated that GPS tracking alone is capable of supporting a radial orbit accuracy for Jason-1 at the 1-cm level, and that including SLR tracking provides additional benefits. It is also shown that the GRACE (Gravity Recovery and Climate Experiment) gravity model GGM01S provides a significant improvement in the orbit accuracy and reduction in the level of geographically correlated orbit errors. 相似文献
275.
276.
GyungNam Jo Hang S. Choi 《Oceanic Engineering, IEEE Journal of》2006,31(3):565-573
This paper discusses the problems related to constructing a receding horizon filter for underwater inertial navigation systems which are subject to external disturbances. Noises are assumed to be bounded, additive, and contained in both state and measurement equations. An estimator is designed according to the sliding-window strategy to minimize the receding horizon estimation cost function. The derived filter is applied to a velocity-aided inertial navigation system. Simulations show that the derived filter is more accurate than the standard Kalman filter (KF) for underwater navigation systems subject to temporary unknown disturbances 相似文献
277.
To understand the changing rainfall–runoff relationship, this study examined climate and streamflow data in the Milwaukee River Basin in southeastern Wisconsin, of which four catchments with different degrees of urbanization were selected for analysis. This study analyzed temperature, precipitation, and streamflow data with a range of statistical methods, including the Mann–Kendall test, double-mass technique, and quantile regression. Runoff ratios and extreme flow indexes were higher in more urbanized catchments. Catchments with long-term data (>forty years) showed significantly increasing runoff ratios and slopes in double-mass curves. Overall, there are signs of changes in the rainfall–runoff relationship, but how much they can be attributed to land use changes is uncertain. 相似文献
278.
Jon Chorover Sunkyung Choi R. Jeff Serne Caleb Strepka Karl T. Mueller 《Geochimica et cosmochimica acta》2008,72(8):2024-2047
Cation partitioning and speciation in an aqueous soil suspension may depend on the coupling of reaction time, sorbate amount and mineral weathering reactions. These factors were varied in sediment suspension experiments to identify geochemical processes that affect migration of Sr2+ and Cs+ introduced to the subsurface by caustic high level radioactive waste (HLRW). Three glacio-fluvial and lacustrine sediments from the Hanford Site (WA, USA) were subjected to hyperalkaline (pH > 13), Na-Al-NO3-OH solution conditions within a gradient field of (i) sorptive concentration (10−5-10−3 m) and (ii) reaction time (0-365 d). Strontium uptake (qSr) exceeded that of cesium at nearly all reaction times. Sorbent affinity for both Cs+ and Sr2+ increased with clay plus silt content at early times, but a prolonged slow uptake process was observed over the course of sediment weathering that erased the texture effect for Sr2+; all sediments showed similar mass normalized uptake after several months of reaction time. Strontium became progressively recalcitrant to desorption after 92 d, with accumulation and aging of neoformed aluminosilicates. Formation of Cs+ and Sr2+-containing cancrinite and sodalite was observed after 183 d by SEM and synchrotron μ-XRF and μ-XRD. EXAFS data for qSr ≈ 40 mmol kg−1 showed incorporation of Sr2+ into both feldspathoid and SrCO3(s) coordination environments after one year. Adsorption was predominant at early times and low sorbate amount, whereas precipitation, controlled largely by sediment Si release, became increasingly important at longer times and higher sorbate amount. Kinetics of contaminant desorption at pH 8 from one year-weathered sediments showed significant dependence on background cation (Ca2+ versus K+) composition. Results of this study indicate that co-precipitation and ion exchange in neoformed aluminosilicates may be an important mechanism controlling Sr2+ and Cs+ mobility in siliceous sediments impacted by hyperalkaline HLRW. 相似文献
279.
Radio-emission of pulsars is investigated through computer simulation. We assume that electronpositron plasma is thermal and beam particles have
b
in the plasma rest frame. The main purpose of this study is to search for unstable electromagnetic waves which may be caused by beam-plasma interactions. We obtain the dominant waves in the range of radio frequencies in the observer frame. The results show that transverse electromagnetic waves grow rapidly, while electrostatic waves have very slow growth. 相似文献
280.