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51.
Atena Shizuya Masahiro Oba Takuto Ando Yukari Ogata Reishi Takashima Hiroshi Nishi Toshifumi Komatsu Phong D. Nguyen 《Island Arc》2020,29(1)
The Hangenberg Crisis at the Devonian–Carboniferous boundary is known as a polyphase extinction event that affected more than 45 % of marine and terrestrial genera. As the cause of this event is still debated, analyses were carried out on sedimentary samples from the Devonian–Carboniferous Pho Han Formation in northeastern Vietnam to reconstruct the paleoenvironment around the time of this event using stable carbon isotopes; total sulfur; manganese; vanadium; molybdenum; and sedimentary organic matter, such as dibenzothiophenes, cadalene, and regular steranes. These geochemical signatures provide a high‐resolution redox history for this section and show that transgression‐driven high primary productivity, possibly enhanced by terrestrial input, caused severe oxygen depletion along the continental margin of the South China block during the Hangenberg Crisis. 相似文献
52.
53.
Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates? 下载免费PDF全文
Hikaru Komatsu Yoshinori Shinohara Tomonori Kume Kenji Tsuruta Kyoichi Otsuki 《水文研究》2016,30(13):2129-2137
Stand transpiration (E) estimated using the sap‐flux method includes uncertainty induced by variations in sap flux (F) within a tree (i.e. radial and azimuthal variations) and those between trees. Unlike radial variations, azimuthal variations are not particularly systematic (i.e. higher/lower F is not always recorded for a specific direction). Here, we present a theoretical framework to address the question on how to allocate a limited number of sensors to minimize uncertainty in E estimates. Specifically, we compare uncertainty in E estimates for two cases: (1) measuring F for two or more directions to cover azimuthal variations in F and (2) measuring F for one direction to cover between‐tree variations in F. The framework formulates the variation in the probability density function for E (σE) based on F recorded in m different azimuthal directions (e.g. north, east, south and west). This formula allows us to determine the m value that minimizes σE. This study applied the framework to F data recorded for a 55‐year‐old Cryptomeria japonica stand. σE for m = 1 was found to be less than the values for m = 2, 3 and 4. Our results suggest that measuring F for one azimuthal direction provides more reliable E estimates than measuring F for two or more azimuthal directions for this stand, given a limited number of sensors. Application of this framework to other datasets helps us decide how to allocate sensors most effectively. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
54.
The dynamics of the wind-driven circulations and surface transport processes in Suruga Bay have been examined by performing
numerical experiments. While strong winds exist outside the bay, the winds inside the bays are greatly reduced, which generates
a strong wind stress curl in winter and autumn. In particular, in winter, a strong positive curl region is located across
the bay mouth, and a strong surface circulation with counterclockwise rotation is generated beneath it. The circulation is
nearly geostrophic, but is not affected by the bottom topography in the deep bay. It is suggested that intense surface water
exchange through the bay mouth occurs in winter, whereas it is not active in the other seasons when no significant vorticity
is supplied on the bay mouth from the atmosphere. Moreover, we propose a hypothesis that the atmospheric wind stress curl
will cause the frequent appearance of the counterclockwise circulation in winter in the real ocean. 相似文献
55.
In a deciduous larch forest in eastern Siberia, the mean and standard deviation of the total evapotranspiration (E) during May to September (day of year (DOY) = 121–274) for 2003–2006 were 181.5 and 26.4 mm, respectively. The interannual variation (IAV) in the total E was caused by the IAV in E for the canopy‐foliated period (DOY = 164–253), not by the IAV in the dates of leaf expansion and leaf fall. For the years with higher total E, E in the canopy‐foliated period was consistently higher, which corresponded to the higher soil water content in these years. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
56.
Kiyoshi Tanaka Yutaka Michida Teruhisa Komatsu Kenji Ishigami 《Journal of Oceanography》2009,65(2):165-177
We have investigated the spreading of river water in Suruga Bay by performing numerical experiments and conducting field surveys
with drifting buoys. There are clear seasonal variations in the large river discharges into the bay: increased discharge in
the rainy summer season and decreased discharge in the dry winter season. The numerical model reproduces the main feature
that has been observed in the actual sea: the river water extends gradually from the northwestern to the southeastern regions
in the bay, especially in summer. The river water spreading is greatly influenced by the bottom topography of the bay: the
Fuji River water spreads over a deep continental slope as a surface-advected plume and extends well offshore, since a large
bulge (anticyclonic eddy at the river mouth) extends well offshore and effectively transports the river water offshore. On
the other hand, the Oi River water tends to flow parallel to isobaths (along a coastline) on a shallow continental shelf as
a bottomadvected plume. Moreover, the influences of seasonal variations in the stratification and a bay-scale, wind-driven
circulation are also investigated. Trajectories of the drifting buoys, which were released around the Fuji River mouth, certainly
suggest that the bulge exists there. 相似文献
57.
According to widely held belief, annual evapotranspiration (ET) for broadleaf forests is less than that for coniferous forests, resulting in higher annual runoff for broadleaf forests. We processed 82 catchment runoff and 126 interception loss data from temperate regions and found that although the belief is valid under conditions of broadleaf deciduous forests and high winter precipitation (e.g. the United States), it is invalid under conditions of broadleaf evergreen forests (e.g. New Zealand) or low winter precipitation (e.g. Japan). Thus, forest management policies based on this belief should be reconsidered on the basis of our results for regions with broadleaf evergreen forests or low winter precipitation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
58.
Sohiko Kameyama Urumu Tsunogai Fumiko Nakagawa Motoki Sasakawa Daisuke D. Komatsu Akira Ijiri Junko Yamaguchi Takeo Horiguchi Hiroshi Kawamura Aika Yamaguchi Atsushi Tsuda 《Marine Chemistry》2009,115(1-2):92-101
During the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study ΙΙ (SEEDS-II), we monitored variations in the concentrations of non-methane hydrocarbons (NMHCs), CH3Cl, N2O, and CH4 within a phytoplankton bloom. Stable isotopic compositions were also determined to evaluate the sources of the variations. Although there was little variation in either the concentrations or the stable isotopic compositions of alkenes, CH3Cl, N2O, and CH4 during the 23-day observation period, alkane concentrations increased substantially as the phytoplankton bloomed. The column-integrated quantities of alkanes increased to 3 times pre-bloom levels for C2H6, 5 times for C3H8, and 20 times for n-C4H10. The δ13C values of both C2H6 and C3H8 remained almost constant while concentrations increased, whereas that of n-C4H10 increased by about 12‰. To evaluate the sources of the alkanes produced during the bloom, we compared their δ13C values with those of alkanes produced in axenic phytoplankton cultures in our laboratory. We concluded that during the SEEDS-ΙΙ experiment the major portions of C2H6 and C3H8 were produced during the autolysis of diatoms cells, whereas n-C4H10 was produced during autolysis of other phytoplankton cells such as cryptophytes and dinoflagellates. 相似文献
59.
Yoshiyuki Miyazawa Makiko Tateishi Hikaru Komatsu Tomo'omi Kumagai Kyoichi Otsuki 《水文研究》2011,25(18):2924-2930
To examine the feasibility of using ecophysiological data from excised leaves for a meteorological simulation model of gas exchange, we compared the obtained gas exchange rates and the modelled ones using excised leaves and those using intact leaves. Instantaneous gas exchange rates of excised leaves and stomatal control in response to environmental conditions were not significantly different from those of attached leaves. Modelled gas exchange rates based on excised leaf data showed a good fit to the diurnal patterns of in situ measurements. This suggests that use of excised leaf data to predict gas exchange of intact leaves is permissible as long as the effects of excision are pre‐screened as described in this paper. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
60.
Toshifumi KOMATSU Reishi TAKASHIMA TA Hoa PHUONG Tran Huyen DANG Duc Phong NGUYEN Huu Hung NGUYEN Satoru KATO Kento HIRATA Takumi MAEKAWA 《地球学报》2012,33(S1):38-38
The Pho Han Formation is exposed on southern Cat Ba Island, Hai Phong Province in northeastern Vietnam, and intercalates the Devonian and Carbonif-erous (D-C) boundary (Ta and Doan, 2007; Komatsu et al., 2012). The D-C boundary section consists mainly of limestone beds, numbered from 1 to 167, interca-lated with alternating black organic-rich shales. The limestone yields abundant brachiopods, crinoid-stems and conodonts. Preliminary investigations on strati-graphy (conodont biostratigraphy and δ13C) and sedi-mentology of beds 113-133 were undertaken in this study. 相似文献