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81.
82.
Tsutomu Sato Isao Machida Makoto Takahashi Taro Nakamura 《Pure and Applied Geophysics》2006,163(4):809-823
Water was sampled from eight springs and a lake in volcanic Miyakejima Island of Japan after the 2000 eruption. Major chemical
and isotopic compositions of the water were analyzed. Significant increases of sulfate ion are observed in several springs
where the thickness of ejecta exceeds 32 mm. A good relationship of Cl/S mole ratios between spring water and leachate of
the ejecta is observed. Sulfur isotopic compositions of the spring water become close to that of leachate of the ejecta as
time elapses after the eruption. Consequently the sources of the added sulfate ion in the spring water after the eruption
are interpreted to be anhydrite and adhered sulfur of the ejecta. 相似文献
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84.
Isao Motoyama Nobuaki Niitsuma Toshiaki Maruyama Hiroki Hayashi Shin-ichi Kamikuri Masamichi Shiono Toshiya Kanamatsu Kaori Aoki Chikako Morishita Kyoko Hagino Hiroshi Nishi Motoyoshi Oda 《Island Arc》2004,13(1):289-305
Abstract Shipboard and shore‐based investigation on siliceous and calcareous microfossil biostratigraphy, magneto‐stratigraphy and tephrostratigraphy identified numerous datum events from the sedimentary sequences of Sites 1150 and 1151 drilled on the forearc basin of northern Japan by the Ocean Drilling Program Leg 186. Some 83 datum events were selected to construct new age–depth models for the sites. Based on the reliable magneto‐stratigraphy from the Pleistocene to the Upper Miocene, which were correlated to the standard geomagnetic polarity timescale, and on excellent records of diatom and radiolarian biostratigraphy throughout the sequences, the shipboard age model was revised. Major revisions referred to stratigraphic position of the Miocene–Pliocene boundary that has been shifted more than 200 m downward in each sequence. The age–depth relations of the forearc sites represent drastic changes in the sedimentation rate—extremely high (40 cm/k.y. on average) in the Early Pliocene and low (less than 2 cm/k.y. on average) in the Middle Miocene—and several hiatuses exist throughout the sequence. The drastic changes can be related mostly to changes in diatom sedimentation and the tectonics of the Japanese Island Arc. Local ages for some foraminiferal, calcareous nannofossil and radiolarian bioevents are estimated from the age–depth models at each site. These newly calibrated bioevents and biozones as well as established diatom biostratigraphy are incorporated into the updated magneto‐biochronologic timescale, which will contribute to an improvement in biochronologic accuracy of Neogene sediments in northern Japan and adjacent areas. 相似文献
85.
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Takashi Kitamura Soji Ohara Takeharu Konishi Katsufumi Tsuji Michiyuki Chikawa Wasaburo Unno Isao Masaki Kenji Urata Yukihiro Kato 《Astroparticle Physics》1997,6(3-4):279-291
Unexpected chaotic features are found in time series of arrival time intervals of successive air showers with (E > 3 × 1014 eV). Over 99 % of air shower arrival time intervals obey the Poisson distribution law representing stochastic behaviors, but occasionally there are air showers showing real chaotic behaviors as distinguished from both random and colored noises. With two systems of the Kinki university installations, we found 13 cases showing chaotic time series in 3.36 yr with the system-1 and the 1.37 yr with the system-2. Five out of 10 chaotic air showers of the Kinki installation are detected during the same time zone also by the Osaka City university installation which is at 115 km distance from the Kinki one. In a remarkable example of September 19, 1991, the correlation dimension was observed to have dropped from about 4 to the minimum of 1.3 and recovered smoothly in about 38 h. The chaos structure in this case is detected in nearly the same time zone at the Ohya station of the Institute for Cosmic Ray Research, University of Tokyo, which is separated from the Kinki one by 460 km. Formation of chaos structure due to energetic cosmic ray dust particles is suggested. Progress of cosmic ray physics may be expected with the study of air showers marked with chaos. 相似文献
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88.
Yuichi Nosaka Tomonori Isada Isao Kudo Hiroaki Saito Hiroshi Hattori Atsushi Tsuda Koji Suzuki 《Journal of Oceanography》2014,70(1):91-103
We investigated the water-column light utilization efficiency (Ψ) of phytoplankton photosynthesis in the Western Subarctic Gyre (WSG) of the North Pacific during summer 2008. The Ψ values (0.64–1.86 g C [g Chl a]?1 [mol photon]?1 m2) obtained were observed to increase significantly with decreasing daily photosynthetic available radiation (PAR) and were generally higher than those of previous studies, not only from the subarctic Pacific but also from the world’s oceans. To examine the effect of iron availability on Ψ in the WSG, Ψ values were estimated from the data of two in situ iron fertilization experiments: the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study I (SEEDS-I) and II (SEEDS-II). We found that iron availability did not affect Ψ values. Overall, this study revealed that Ψ values changed remarkably in the WSG during the summer, and that higher values were found at the stations where moderate PAR levels (ca. 10–30 mol photons m?2 day?1) were observed and where autotrophic flagellates predominated in the phytoplankton assemblages. 相似文献