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61.
Ichiro Hasegawa Syuichi Nakano 《Monthly notices of the Royal Astronomical Society》2003,345(3):883-888
The orbit of Comet C/2002C1 (Ikeya–Zhang) has a similarity to that of Comet C/1661C1 (Hevelius), and the numerical integration of the motion of C/2002C1 backward shows a possible linkage of those two comets. Thus, 153P/Ikeya–Zhang was designated a periodic comet. Historical records of comets in 877 and 1273 are also identified with Comet 153P/Ikeya–Zhang. The integrated orbital elements during 77 and 2362, and historical records of the comet are also presented and discussed. 相似文献
62.
Takahisa Furuichi Nobutomo Osanai Shin-ichiro Hayashi Norihiro Izumi Tomoko Kyuka Yasuhiro Shiono Tomoyoshi Miyazaki Tomoya Hayakawa Norihiro Nagano Naoki Matsuoka 《Landslides》2018,15(8):1645-1655
In August 2016, Typhoon 1610 (Lionrock) caused heavy rainfall in Hokkaido, which led to the discharge of a large volume of sediment and water from catchments on the eastern slope of the northern Hidaka Range. The eight catchments examined in this study are characterized by granitic lithology and late Pleistocene periglacial landforms with weakly cohesive, low-resistance periglacial debris thickly covering the weathered bedrocks. This characteristic of the landscape presumably provided a transport-limited condition where some debris flows were initiated by shallow landslides. As they moved, the debris flows grew larger through mobilization and erosion of sediment in channel beds and sidewalls. This sediment mobilization and erosion continued for an extensive distance along the course of the river. Morphological changes induced by channel aggradation and bank erosion were considerable and distinctive from upstream to downstream. Granitic periglacial sediments are amply present on the mountain slopes, river channels, and river banks in the area, likely due to the rarity of intensive rainfall events. These distinctive features of fossil periglacial catchments are important for disaster prevention and catchment-scale sediment management in sub-boreal areas, particularly in the context of climate change, which may generate more frequent and intensive rainfall events. 相似文献
63.
Topo-stress based probabilistic model for shallow landslide susceptibility zonation in the Nepal Himalaya 总被引:1,自引:1,他引:0
Ranjan Kumar Dahal Netra Prakash Bhandary Shuichi Hasegawa Ryuichi Yatabe 《Environmental Earth Sciences》2014,71(9):3879-3892
While dealing with slope stability issues, determining the state of stress and the relation between driving force and resisting force are the fundamental deterministic steps. Gravitational stresses affect geologic processes and engineering operations in slopes. Considering this fact, a concept of topo-stress evaluation is developed in this research and used to produce a shallow landslide susceptibility map in a model area. The topo-stress introduced in this research refers to the shear stress induced by the gravitational forces on the planes parallel to the ground surface. Weight of the material on a slope and friction angle of the jointed rock mass are the two fundamental parameters that are considered to govern topo-stress in this study. Considering topo-stress as a main factor for initiating shallow landslides, a GIS-based probabilistic model is developed for shallow landslide susceptibility zonation. An ideal terrain in central Nepal is selected as the study area for this purpose. Two event-based shallow landslide inventories are used to predict accuracy of the model, which is found to be more than 78 % for the first event-landslides and more than 76 % for the second event-landslides. It is evident from these prediction rates that the probabilistic topo-stress model proposed in this work is quite acceptable when regional scale shallow landslide susceptibility mapping is practiced, such as in the Himalayan rocky slopes. 相似文献
64.
In the epicentral region of subduction earthquakes, large-scale landslides are triggered by strong shaking of slopes weakened by flexural toppling. The distribution of flexural-toppled slopes is the primary information for predicting and mitigating landslide damage beforehand. This study proposes and tests a simple algorithm for extracting flexural-toppled slopes on a regional basis from a 10-m resolution digital elevation model by windows of two sizes. Local relief is extracted with a large window (200 × 200 pixels), and microtopography is extracted with a small window (3 × 3 pixels). The algorithm was derived from the region of the Kanagi-kuzure landslide in Shikoku, and tested at Aka-kuzure landslide in Honshu in Japan. Both areas are underlain by strongly tilted sedimentary rocks in epicentral regions of subduction earthquakes along the Nankai Trough. 相似文献
65.
Kana NAKATANI Yuki OKUYAMA Yuji HASEGAWA Yoshifumi SATOFUKA Takahisa MIZUYAMA 《山地科学学报》2013,10(2):273-280
Debris flows form deposits when they reach an alluvial fan until they eventually stop.However,houses located in the alluvial fan might affect the debris flow flooding and deposition processes.Few previous studies have considered the effects of houses on debris flow flooding and deposition.This study conducted model experiments and numerical simulations using the Kanako2D debris flow simulator to determine the influence of houses on debris flow flooding and deposition.The model experiments showed that when houses are present,the debris flow spreads widely in the cross direction immediately upstream of the houses,especially when the flow discharge is large or the grain size is small.Houses located in the alluvial fan also influence the deposition area.The presence of houses led to flooding and deposition damage in some places and reduced the damage in others.The simulation also demonstrated the influence of houses.Both the model experiment and the simulation showed that houses change the flooding and deposition areas. 相似文献
66.
以单次散射模型、球形辐射源、一维线性速度模型为基础计算理论包络线,通过尾波归一化方法把理论与观测包络线结合起来形成非线性方程组,用迭代最小二乘方法反演伽师强震群区的散射系数空间分布.结果表明,伽师强震群区下方中上地壳中存在明显的非均匀结构.在10~25 km各深度图像上,研究区中部都存在一低散射系数区,这个低散射系数区在10 km、15 km深度被高散射系数区包围,在20 km深度仅其东侧存在高散射系数区.1997年的7次Ms≥6.0级地震发生在研究区中部的低散射系数区内或低散射系数区向高散射系数区过渡带的低散射系数一侧. 相似文献
67.
Assessing flood disaster impacts in agriculture under climate change in the river basins of Southeast Asia 总被引:1,自引:0,他引:1
Shrestha Badri Bhakta Perera Edangodage Duminda Pradeep Kudo Shun Miyamoto Mamoru Yamazaki Yusuke Kuribayashi Daisuke Sawano Hisaya Sayama Takahiro Magome Jun Hasegawa Akira Ushiyama Tomoki Iwami Yoichi Tokunaga Yoshio 《Natural Hazards》2019,97(1):157-192
Natural Hazards - This study focused on flood damage assessment for future floods under the impact of climate change. Four river basins of Southeast Asia were selected for the study. They included... 相似文献
68.
Yukiko Taniuchi Tsuyoshi Watanabe Shigeho Kakehi Tomoko Sakami Akira Kuwata 《Journal of Oceanography》2017,73(1):1-9
Sendai Bay is located on the Pacific coast of northern Japan and suffered serious damage following the 2011 off the Pacific coast of Tohoku earthquake and tsunami in March 2011. To assess the impact on the marine ecosystem, information was needed on the phytoplankton communities and their seasonal variation. However, such information was limited. Therefore, an intensive monitoring of the phytoplankton was carried out from March 2012 to April 2014. Seasonal variation of the phytoplankton community was similar at coastal and offshore stations. Total phytoplankton biomass, based on Chl a concentration, peaked in spring and then decreased to a minimum in summer, before gradually increasing during early winter and peaking again in the following spring. This seasonal pattern was consistent with previous studies conducted before the earthquake and tsunami. Also, size structure of the phytoplankton community and its four main groups was estimated from the size-fractioned samples of Chl a. Our results also showed that the spring bloom consisted of large diatoms, with their growth ceasing due to nitrogen depletion. The bloom was followed by a summer period where cyanobacteria and picoeukaryote became dominant, with high cell densities in spite of low nutrient concentrations. In addition, sporadic environmental changes, such as those following typhoons, were observed. These resulted in large increases/decreases in individual phytoplankton groups. 相似文献
69.
Tsuyoshi Watanabe Yukiko Taniuchi Shigeho Kakehi Tomoko Sakami Akira Kuwata 《Journal of Oceanography》2017,73(1):133-144
Sendai Bay in northern Japan suffered serious damage from massive tsunamis generated by the 2011 off the Pacific coast of Tohoku earthquake. The physical disturbance caused by a tsunami may affect the coastal ecosystem, including the planktonic diatom community. We investigated seasonal changes in the diatom community structure at a coastal and an offshore station in Sendai Bay, from June 2011 (3 months after the tsunami) to April 2014. Diatom abundance increased at both stations during the spring. Sporadic increases were also recorded at the coastal station during the summer because of silicate input from river discharge. Seasonal succession of the diatom communities was similar at both the coastal and offshore stations. The onset of the spring bloom consisted mainly of Chaetoceros spp. when water temperatures were low. Subsequently, species such as Skeletonema costatum s.l. became dominant as salinity and nutrient concentrations decreased. Cell density decreased from summer into early winter. Leptocylindrus danicus became dominant in the summer, but was replaced by Thalassiosira cf. mala from autumn into winter. Redundancy analysis (RDA) showed that most of the variation in the diatom community could be explained by temperature, salinity, NO3 ?, NO2 ?, PO4 3?, and SiO2. In addition, the occurrence of diatom species before the tsunami showed a similar pattern to that after the tsunami, suggesting that the tsunami did not have a serious impact on the diatom community in Sendai Bay. 相似文献
70.
Kentaro Ando Yoshifumi Kuroda Yosuke Fujii Tatsuya Fukuda Takuya Hasegawa Takanori Horii Yasuhisa Ishihara Yuji Kashino Yukio Masumoto Keisuke Mizuno Motoki Nagura Iwao Ueki 《Journal of Oceanography》2017,73(4):403-426
The Triangle Trans‐Ocean Buoy Network (TRITON) project by the Japan Agency for Marine-Earth Science and Technology began with deployment in the western tropical Pacific Ocean in 1998 and has shifted to steady, long-term observations since 1999. After on-site inter-comparison with the Autonomous Temperature Line Acquisition System mooring system of the Tropical Atmosphere and Ocean (TAO) array by the National Oceanic and Atmospheric Administration, the TRITON array became the international TAO/TRITON array in 2000 as a key component of the Global Ocean and Climate Observing Systems. The TAO/TRITON array took over from the TAO array, which was developed during the Tropical Ocean and Global Atmosphere program (1985–1994), and replaced the western part of TAO with new additional real-time measurements of salinity and ocean currents. In 2001, two TRITON moorings were deployed in the eastern Indian Ocean for capturing the eastern pole of the Indian Ocean Dipole. From this initiative, the Indian Ocean Observing System (IndOOS) was designed, and the Indian Ocean mooring array (Research Moored Array for Africa–Asian–Australian Monsoon Analysis and Prediction) was developed as a key component of IndOOS. In this paper, 15 years of progress in the TRITON project in the western Pacific and eastern Indian Oceans is reviewed with regards to scientific outcomes, technological development, and collaborations with international and domestic partners. Future directions for sustainable observation in the Pacific and Indian Oceans are also discussed. 相似文献