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131.
Yutaka Nagata 《Journal of Oceanography》1979,35(3-4):141-150
The statistical properties of shallow temperature inversions in the Pacific Ocean near Japan were investigated using data obtained from. BT observations. In the sea east of Honshu, the Kuroshio front forms the southern boundary of the area where temperature inversions are abundant. Though the occurrence frequency of the temperature inversion layers is very low in the sea south of Honshu, the path of the Kuroshio influences its regional distribution in this region also, and the high occurrence area shifts offshore when the large cold water mass is present off Enshu-nada. The magnitude of the inversion temperature differences in the sea south of Honshu is considerably smaller than that in the sea east of Honshu. The magnitude of inversion thickness has a clear tendency to increase from south to north in the sea east of Honshu, reflecting the higher occurrence frequency of large-scale thick inversion layers in the northern part under the influence of the sub-arctic water mass. The frequency distribution of the inversion thickness in each sub-region (1° square area) in the sea south of Honshu is very similar to that in the region just south of the Kuroshio front in the sea east of Honshu, suggesting that the inversion layers may be generated by similar mechanisms in the sea south of the Kuroshio front. 相似文献
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134.
Tomoharu Hori Takeyuki Sugimoto Yutaka Ichikawa 《Physics and Chemistry of the Earth》2008,33(5):376-381
An estimation model of farm field irrigation water demand is developed. The model is based on the lumped kinematic wave model considering soil water balance. The lumped model approach reduces the computational load in rainfall-runoff analysis and allows application to large river basins. Evapotranspiration is estimated on hourly basis by the improvement of FAO’s method. Not only water volume necessary for farm field irrigation but also the number of the water charge and its interval can be estimated by the combined use of the lumped runoff model and the hourly evapotranspiration model. 相似文献
135.
Satoru Kojima Tamotsu Nozaki Hidehisa Nagata Ryota Tanahashi Ryoich Kondo Noriaki Okamura Kazuhiro Suzuki Akiko Ikeda Toshio Nakamura Tomoyuki Ohtani 《Environmental Earth Sciences》2014,71(6):2753-2763
Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry 14C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone. 相似文献
136.
Tetsuya Nishikawa Yutaka Hori Satoshi Nagai Kazutaka Miyahara Yukinobu Nakamura Kazuhiro Harada Minoru Tanda Takehiko Manabe Kuninao Tada 《Estuaries and Coasts》2010,33(2):417-427
Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration. 相似文献
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138.
Characteristics and climatic sensitivities of runoff from a cold‐type glacier on the Tibetan Plateau
Model calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow–ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter. Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
139.
Chuan-Lin Zhang Dong-Sheng Yang Hong-Yan Wang Yutaka Takahashi Hai-Min Ye 《Gondwana Research》2011,19(1):177-190
In this paper we report zircon U–Pb age, chemical compositions of rock-forming minerals, and whole-rock elemental and Sr–Nd isotopic data for the No. II mafic-ultramafic intrusive complex (N2MC) in the Quruqtagh area at the northeastern margin of the Tarim Block, northwestern China to evaluate its petrogenesis and tectonic significance. The N2MC with an exposure area of ca. 12 km2 has a funnel-shaped cross-section and intruded the Paleoproterozoic basement. U–Pb zircon dating gives a crystallization age of 760 ± 6 Ma. Rock types of the N2MC include lherzolite, pyroxenite, gabbro and minor diorite. Major elements geochemistry of these rocks exhibits a tholeiitic trend with a wide range of SiO2 contents (38.8–60 wt.%). On the other hand, they are systematically enriched in LILE, LREE and depleted in HFSE and HREE, thus leading to low HFSE/LREE ratios (e.g., Nb/La ≈ 0.3). Isotopically, the studied rocks are characterized by negative whole-rock εNd(t) values (? 7.6 to ? 2.8) and variable high (87Sr/86Sr)i (0.7095–0.7059). These features, together with chemical compositions of the rock-forming minerals and the presence of the primary phlogopite and hornblende, suggest that N2MC was likely formed via crystal fractionation/cumulation (with negligible crustal contamination) of a tholeiitic magma derived from a metasomatized subcontinental lithosphere mantle (SCLM) in an extensional environment. The enrichment of the mantle source could be ascribed to the metasomatism by subducted-slab-released fluids before partial melting. Overall, reported Neoproterozoic igneous rocks throughout the Tarim Block constitute two major phases of Neoproterozoic igneous activities, i.e., ca. 825–800 Ma and ca. 780–745 Ma, respectively. Similar to that of many other Rodinian continents, this feature is interpreted to be related to the two phases of Neoproterozoic mantle plume activity under the Rodinia. Furthermore, there exist two types of mafic-ultramafic complex at Quruqtagh, i.e., the ca. 820 Ma carbonatite-bearing and the ca. 760 Ma tholeiitic, which could reflect the presence of two different mantle sources. 相似文献
140.
This study was designed to develop a physically based hydrological model to describe the hydrological processes within forested mountainous river basins. The model describes the relationships between hydrological fluxes and catchment characteristics that are influenced by topography and land cover. Hydrological processes representative of temperate basins in steep terrain that are incorporated in the model include intercepted rainfall, evaporation, transpiration, infiltration into macropores, partitioning between preferential flow and soil matrix flow, percolation, capillary rise, surface flow (saturation‐excess and return flow), subsurface flow (preferential subsurface flow and baseflow) and spatial water‐table dynamics. The soil–vegetation–atmosphere transfer scheme used was the single‐layer Penman–Monteith model, although a two‐layer model was also provided. The catchment characteristics include topography (elevation, topographic indices), slope and contributing area, where a digital elevation model provided flow direction on the steepest gradient flow path. The hydrological fluxes and catchment characteristics are modelled based on the variable source‐area concept, which defines the dynamics of the watershed response. Flow generated on land for each sub‐basin is routed to the river channel by a kinematic wave model. In the river channel, the combined flows from sub‐basins are routed by the Muskingum–Cunge model to the river outlet; these comprise inputs to the river downstream. The model was applied to the Hikimi river basin in Japan. Spatial decadal values of the normalized difference vegetation index and leaf area index were used for the yearly simulations. Results were satisfactory, as indicated by model efficiency criteria, and analysis showed that the rainfall input is not representative of the orographic lifting induced rainfall in the mountainous Hikimi river basin. Also, a simple representation of the effects of preferential flow within the soil matrix flow has a slight significance for soil moisture status, but is insignificant for river flow estimations. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献