全文获取类型
收费全文 | 179篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
大气科学 | 7篇 |
地球物理 | 45篇 |
地质学 | 37篇 |
海洋学 | 56篇 |
天文学 | 28篇 |
综合类 | 1篇 |
自然地理 | 10篇 |
出版年
2024年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 8篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有184条查询结果,搜索用时 31 毫秒
121.
We carried out a spectral observation of traces of the comet impacts within the wavelength region between 440 and 830 nm. Three dark spots of fragments K, E, and G impact sites were investigated. The spectrum of these dark spots shows no special emission or absorption lines in this observation. The global spectral feature resembles that of Jovian zone cloud rather than that of the belt. While the continuum reflectivity of the dark spots of K and E sites is less than 0.42 at 600 nm, that of the G site is 0.33. These values should be interpreted as an upper limits because of the influence of atmospheric seeing. The equivalent width of the absorption lines at the K sites is also derived. Both the continuum reflectivity and the equivalent width of the dark spots are smaller than those of any Jovian zonal cloud. This indicates that the dark spots are low-albedo cloud formed at the upper atmosphere. 相似文献
122.
Takashi Kudo Minoru Sasaki Yoshihiro Uchiyama Akifumi Nozawa Hisashi Sasaki Takeshi Tokizawa Shinji Takarada 《Island Arc》2007,16(1):133-155
Abstract The Hakkoda‐Towada caldera cluster (HTCC) is a typical Late Cenozoic caldera cluster located in the northern part of the Northeast Japan Arc. The HTCC consists of five caldera volcanoes, active between 3.5 Ma and present time. The felsic magmas can be classified into high‐K (HK‐) type and medium‐ to low‐K (MLK‐) type based on their whole‐rock chemistry. The HK‐type magmas are characterized by higher K2O and Rb contents and higher 87Sr/86Sr ratios than MLK‐type magmas. Both magmas cannot be derived from fractional crystallization of any basaltic magma in the HTCC. Assimilation‐fractional crystallization model calculations show that crustal assimilation is necessary for producing the felsic magmas, and HK‐type magmas are produced by higher degree of crustal assimilation with fractional crystallization than MLK‐type magmas. Although MLK‐type magmas were erupted throughout HTCC activity, HK‐type magmas were erupted only during the initial stage. The temporal variations of magma types suggest the large contribution of crustal components in the initial stage. A major volcanic hiatus of 3 my before the HTCC activity suggests a relatively cold crust in the initial stage. The cold crust probably promoted crustal assimilation and fractional crystallization, and caused the initial generation of HK‐type magmas. Subsequently, the repeated supply of mantle‐derived magmas raised temperature in the crust and formed relatively stable magma pathways. Such a later system produced MLK‐type magmas with lesser crustal components. The MLK‐type magmas are common and HK‐type magmas are exceptional during the Pliocene–Quaternary volcanism in the Northeast Japan Arc. This fact suggests that exceptional conditions are necessary for the production of HK‐type magmas. A relatively cold crust caused by a long volcanic hiatus (several million years) is considered as one of the probable conditions. Intensive crustal assimilation and fractional crystallization promoted by the cold crust may be necessary for the generation of highly evolved HK‐type felsic magmas. 相似文献
123.
—?The stress state at the Hijiori hot dry rock site was estimated based on the inversion from focal mechanisms of microseismic events induced during hydraulic injection experiments. The best fit stress model obtained by inverting 58 focal mechanisms of seismic events simultaneously indicates that the maximum principal stress σ1 is vertical, while the minimum principal stress σ3 is horizontal and trends north-south. The average misfit between the stress model and all the data is 6.8°. The inversion results show that the average misfit is small enough to satisfy the assumption of homogeneity in the focal mechanism data and that the 95% confidence regions of σ1 and σ3 are well constrained, i.e., they do not overlap, suggesting that the inversion results are acceptable. The stress estimates obtained by the focal mechanism inversion essentially agree with other stress estimates previously obtained. It is therefore concluded that the focal mechanism inversion method provides a useful tool for estimating the stress state. The hypocentral distributions of microseismic events associated with the hydraulic fracturing experiments are distributed around the plane that spreads to almost east–west from the injection wells and declines to the north at a high angle. The vertical orientation and east–west strike of the seismic events are essentially coplanar with the caldera ring-fault structure in the southern portion of the Hijiori Caldera. This indicates that tensile fractures of intact rock were not being created, but pre-existing fractures were being re-opened and developed in the direction of the maximum horizontal principal stress, although microseismic events were caused by shear failures. 相似文献
124.
Energy and thermal transfers in active volcanoes can play an important role incontrolling their dynamics depending on the hydrothermal state. Much geothermalenergy is released through the groundwater circulation, hot gas emission and thermalconduction. Therefore, it is very important to know the hydrological and thermalenvironments associated with volcanoes from the volcano-energetic point of view.However, it is difficult to evaluate these because of the availability of only a fewborehole data on the summit of volcanoes. Recent studies reveal that self-potential(SP) anomalies (up to some hundreds of mV) are observed on volcanoes, activefissure zones and/or fumarolic areas, suggesting that the SP anomalies are closelyrelated to heat-triggered phenomena such as thermoelectric and electrokinetic effectsdue to hydrothermal circulations. Therefore, SP studies can be appropriate for sensingthe thermal and hydrothermal states of volcanoes. In addition, monitoring SP anomaliescan be an efficient method for describing the change of thermal state and the evolutionof the hydrothermal (and volcanic) activities.In this paper, we have reviewed the origin of the SP anomalies associated withvolcanic phenomena theoretically as well as experimentally. Subsequently, wehave presented the results of many case studies and have classified the types ofanomalies in accordance with possible mechanisms. We have also described theresults of time variations of SP anomalies associated with volcanic activities. Timevarying SP fields exhibit the dynamic aspects of volcanic activities correspondingto the evolution of hydrothermal activity, changes in ground water circulation andmagma displacement. These morphological insights should lead to a quantitativeinterpretation of SP anomalies in volcanic regions. 相似文献
125.
126.
Kazunori Arita Takashi Ikawa Tanio Ito Akihiko Yamamoto Matsuhiko Saito Yasunori Nishida Hideyuki Satoh Gaku Kimura Teruo Watanabe Takeshi Ikawa Toru Kuroda 《Tectonophysics》1998,290(3-4):197-210
This study is the first integrated geological and geophysical investigation of the Hidaka Collision Zone in southern Central Hokkaido, Japan, which shows complex collision tectonics with a westward vergence. The Hidaka Collision Zone consists of the Idon'nappu Belt (IB), the Poroshiri Ophiolite Belt (POB) and the Hidaka Metamorphic Belt (HMB) with the Hidaka Belt from west to east. The POB (metamorphosed ophiolites) is overthrust by the HMB (steeply eastward-dipping palaeo-arc crust) along the Hidaka Main Thrust (HMT), and in turn, thrusts over the Idon'nappu Belt (melanges) along the Hidaka Western Thrust (HWT). Seismic reflection and gravity surveys along a 20-km-long traverse across the southern Hidaka Mountains revealed hitherto unknown crustal structures of the collision zone such as listric thrusts, back thrusts, frontal thrust-and-fold structures, and duplex structures. The main findings are as follows. (1) The HMT, which dips steeply at the surface, is a listric fault dipping gently at a depth of 7 km beneath the eastern end of the HMB, and cutting across the lithological boundaries and schistosity of the Hidaka metamorphic rocks. (2) A second reflector is detected 1 km below the HMT reflector. The intervening part between these two reflectors is inferred to be the POB, which is only little exposed at the surface. This inference is supported by the high positive Bouguer anomalies along the Hidaka Mountains. (3) The shallow portion of the IB at the front of the collision zone has a number of NNE-dipping reflectors, indicative of imbricated fold-and-thrust structures. (4) Subhorizontal reflectors at a depth of 14 km are recognized intermittently at both sides of the seismic profile. These reflectors may correspond to the velocity boundary (5.9–6.6 km/s) previously obtained from seismic refraction profiling in the northern Hidaka Mountains. (5) These crustal structures as well as the back thrust found in the eastern end of the traverse represent characteristics of collisional tectonics resulting from the two collisional events since the Early Tertiary. 相似文献
127.
Yoshihiro Fujiwara Masaru Kawato Tomoko Yamamoto Toshiro Yamanaka Waka Sato-Okoshi Chikayo Noda Shinji Tsuchida Tomoyuki Komai Sherine Sonia Cubelio Takenori Sasaki Karen Jacobsen Kaoru Kubokawa Katsunori Fujikura Tadashi Maruyama Yasuo Furushima Kenji Okoshi Hiroshi Miyake Masayuki Miyazaki Yuichi Nogi Akiko Yatabe & Takashi Okutani 《Marine Ecology》2007,28(1):219-232
We report the first study of sperm whale‐fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2‐year period on replicate sperm‐whale carcasses implanted at depths of 219–254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis‐based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep‐water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep‐water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale‐fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls. 相似文献
128.
Akihiro Shiomoto Katsuyuki Sasaki Toru Shimoda Satsuki Matsumura 《Journal of Oceanography》1994,50(2):209-222
Primary productivity was measured byin situ method using13C in the offshore Oyashio region in the spring (May) and summer (September) of 1990. Most of the values were within the range of 0.1 to 4 gC 1–1 h–1 although a very large value, 7.96 gC l–1 h–1, was observed in summer. Most daily primary production fell within the range of 372 to 633 mgC m–2 d–1 although a very large value, 2,109 mgC m–2 d–1, was observed around the frontal area in summer. Chlorophylla (Chl.a) exceeded 1 g l–1 in many cases, and the maximum was 4.61 g l–1 in spring and 7.53 g l–1 in summer. Most primary productivity per unit Chl.a (photosynthetic assimilation ratio) was within the range of 0.1 to 3 gC gChl.a
–1 h–1 although higher values, 3–6 gC gChl.a
–1 h–1, were observed where small-size phytoplanktons (<2 m) were dominant. These results were compared with results obtained until now in the Oyashio region. The values beyond the range obtained so far in the offshore region were also observed in this study. Furthermore, it was pointed out that the size composition of phytoplankton community has significant influence on the results of Chl.a and photosynthetic assimilation ratio in the Oyashio region. 相似文献
129.
In order to determine quantitatively the reason for the high productivity in the Oyashio Region, which is the southwest part
of the Pacific Subarctic Region, the annual-mean vertical circulation of nitrogen in the region was estimated from the vertical
profiles of nitrate, dissolved oxygen and salinity, and sediment-trap data by adapting them to the balance equations. Estimates
of the upwelling velocity (1.7×10−5cm sec−1) and the vertical diffusivity (2.1 cm2 sec−1) in the abyssal zone and the primary and secondary productivities (44 and 4 mgN m−2day−1, respectively) in the euphotic zone were close to those of previous works. The estimated vertical circulation of nitrogen
strongly suggested that, since the divergence (5 mgN m−2day−1) is caused by the abyssal convergence (6 mgN m−2day−1) and the positive precipitation, the local new production (22 mgN m−2day−1) necessarily exceeds not only the sinking flux (10 mgN m−2day−1) itself but also the sum of the sinking flux and the downward diffusion of dissolved and particulate organic matter (7 mgN
m−2day−1) produced probably in the euphotic zone. The important roles of the abyssal circulation, the winter convection, and the metabolic
activity in the bathyal zone to support the high productivity in the euphotic zone were clarified quantitatively. 相似文献
130.
Hiroshi Murakami Kosei Sasaoka Kohtaro Hosoda Hajime Fukushima Mitsuhiro Toratani Robert Frouin B. Greg Mitchell Mati Kahru Pierre-Yves Deschamps Dennis Clark Stephanie Flora Motoaki Kishino Sei-Ichi Saitoh Ichio Asanuma Akihiko Tanaka Hiroaki Sasaki Katsumi Yokouchi Yoko Kiyomoto Hiroaki Saito Cécile Dupouy Absornsuda Siripong Satsuki Matsumura Joji Ishizaka 《Journal of Oceanography》2006,62(3):373-393
The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April
2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between
GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for
aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI
ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences
(MedPD) between GLI and in-situ data were 14.1–35.7% for nLws at 380–565 nm, 52.5–74.8% nLws at 625–680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6%
for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products
are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated
in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that
we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection
for further applications, including coastal monitoring and the combined use of products from multiple sensors. 相似文献