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1.
Ocean Science Journal - This study examines the different effects of high and low freshwater discharge on the water physical structure of the water column and plankton community in a tide-dominated... 相似文献
2.
Average velocity in streams is a key variable for the analysis and modelling of hydrological and hydraulic processes underpinning water resources science and practice. The present study evaluates the impact of the sampling duration on the quality of average velocity measurements acquired with contemporary instruments such as Acoustic Doppler Velocimeters (ADV) an Acoustic Doppler Current Profilers (ADCP). The evaluation combines considerations on turbulent flows and principles and configurations of acoustic instruments with practical experience in conducting customized analysis for uncertainty analysis purposes. The study sheds new insights on the spatial and temporal variability of the uncertainty in the measurement of average velocities due to variable sampling durations acting in isolation from other sources of uncertainties. Sampling durations of 90 and 150 s are found sufficient for ADV and ADCP, respectively, to obtain reliable average velocities in a flow affected only by natural turbulence and instrument noise. Larger sampling durations are needed for measurements in most of the natural streams exposed to additional sources of data variability. 相似文献
3.
Ocean Science Journal - The carbon isotopic compositions (δ13C) of n-alkanes in various environmental samples have been previously proposed as suitable fingerprints for assessing the origin of... 相似文献
4.
Kang Yoonja Kang Hee-Yoon Kim Dongyoung Lee Young-Jae Kim Tae-Ik Kang Chang-Keun 《Ocean Science Journal》2019,54(3):467-486
Ocean Science Journal - Coastal water around the archipelago off southwestern Korea has been bathed in an unprecedented pool of warm water in summer in recent years. Here, we examined phytoplankton... 相似文献
5.
Palaeoflood hydraulic modelling is essential for quantifying ‘millennial flood’ events not covered in the instrumental record. Palaeoflood modelling research has largely focused on one-dimensional analysis for geomorphologically stable fluvial settings because two-dimensional analysis for dynamic alluvial settings is time consuming and requires a detailed representation of the past landscape. In this study, we make the step to spatially continuous palaeoflood modelling for a large and dynamic lowland area. We applied advanced hydraulic model simulations (1D–2D coupled set-up in HEC-RAS with 950 channel sections and 108 × 103 floodplain grid cells) to quantify the extent and magnitude of past floods in the Lower Rhine river valley and upper delta. As input, we used a high-resolution terrain reconstruction (palaeo-DEM) of the area in early mediaeval times, complemented with hydraulic roughness values. After conducting a series of model runs with increasing discharge magnitudes at the upstream boundary, we compared the simulated flood water levels with an inventory of exceeded and non-exceeded elevations extracted from various geological, archaeological and historical sources. This comparison demonstrated a Lower Rhine millennial flood magnitude of approximately 14,000 m3/s for the Late Holocene period before late mediaeval times. This value exceeds the largest measured discharges in the instrumental record, but not the design discharges currently accounted for in flood risk management. 相似文献
6.
Pile foundations that support transmission towers or offshore structures are dominantly subjected to cyclic lateral load induced by wind and waves. For a successful design, it is crucial to investigate the effect of cyclic lateral loads on the pile behavior that is loaded laterally. Although the p–y curve method is generally utilized to design the cyclic laterally loaded pile foundations, the effect of cyclic lateral loads on the pile has not been properly implemented with the p–y curve. This reflects a lack of consideration of the overall stiffness change in soil–pile interaction. To address this, a series of model pile tests were conducted in this study on a preinstalled aluminum flexible pile under various sandy soil conditions. The test results were used to investigate the effect of cyclic lateral loads on the p–y behavior. The cyclic p–y curve, which properly takes into account this effect, was developed as a hyperbolic function. Pseudo-static analysis was also conducted with the proposed cyclic p–y curve, which showed that it was able to properly simulate cyclic laterally loaded pile behavior in sandy soil. 相似文献
7.
8.
Juhyun Kim 《Marine Georesources & Geotechnology》2018,36(5):579-588
Classification of fine-grained soils is typically conducted using plasticity charts. The typically used plasticity chart proposed by Casagrande was questioned by Polidori proposing different classification criterion in separating clayey and silty soils. Using natural clayey and silty soils sampled from four different coastal sites in Korea, applicability of both Casagrande’s and Polidori’s plasticity charts was evaluated. Classification results of Korean natural soils based on the Casagrande’s and Polidori’s plasticity charts did not match well with those based on the soils’ behavior reported in the previous publication. The disagreement in classification of Korean natural fine-grained soils may result from disregard of considerable silt fraction effect on plastic and liquid limits for Polidori’s chart. Consequently, revised proposal of Polidori’s plasticity chart was tentatively made for further classification of fine-grained soils suitable for Korean natural soils by accounting the effect of silt fraction on soil classification. 相似文献
9.
Theoretical and Applied Climatology - The results of the present study prove that snowfall occurred due to the polar low (PL) in the Korean Peninsula and six cases of snowfall exceeding a snow... 相似文献
10.
Despite its potential significance for industrial utilization, any activities associated with the mining of manganese (Mn) nodules might have substantial impacts on benthic ecosystems. Because microorganisms respond quickly to changing environmental conditions, a study of microbial communities provides a relevant proxy to assess possible changes in benthic ecosystems associated with mining activities. We investigated fine-scale microbial community composition and diversity inside and on the surface of Mn nodules and in nearby deep-sea sediments in the Korea Deep Ocean Study (KODOS) area located in the Clarion-Clipperton Fracture Zone (CCFZ) of the northeast equatorial Pacific. Although microbial cell density was lower within nodules (3.21 × 106 cells g-1) than in sediment (2.14 × 108 cells g-1), nodules provided a unique habitat for microorganisms. Manganese-oxidizing bacteria including Hyphomicrobium and Aurantimonas in Alphaproteobacteria and Marinobacter in Gammaproteobacteria were abundant in nodules, which implied that these bacteria play a significant role in nodule formation. In contrast, Idiomarina in Gammaproteobacteria and Erythrobacter and Sulfitobacter in Alphaproteobacteria were abundant in sediments. Meanwhile, Thaumarchaeota, a phylum that consists of ammonia-oxidizing chemolithoautotrophs, were the predominant archaeal group both in nodules and sediment. Overall, microbial communities in Mn nodules were unique compared to those observed in sediments. Furthermore, the phylogenetic composition of microorganisms in the KODOS area was distinguishable from that in the nodule provinces claimed by China and Germany in the CCFZ and nodule fields in the central South Pacific Gyre, respectively. 相似文献