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41.
A 100 m laser strainmeter system installed in a 1 km deep tunnel at Kamioka, Gifu, Japan 总被引:1,自引:0,他引:1
Shuzo Takemoto Akito Araya Junpei Akamatsu Wataru Morii Hideo Momose Masatake Ohashi Ichiro Kawasaki Toshihiro Higashi Yoichi Fukuda Shinji Miyoki Takashi Uchiyama Daisuke Tatsumi Hideo Hanada Isao Naito Souichi Telada Nobuo Ichikawa Kensuke Onoue Yasuo Wada 《Journal of Geodynamics》2004,38(3-5):477
We have installed a laser strainmeter system in a deep tunnel about 1,000 m below the ground surface at Kamioka, Gifu, Japan. The system consists of three types of independent interferometers: (1) an EW linear strainmeter of the Michelson type with unequal arms, (2) an NS-EW differential strainmeter of the Michelson type with equal arms and (3) a NS absolute strainmeter of the Fabry–Perot type. These are configured in L-shaped vacuum pipes, each of which has a length of 100 m. (1) and (2) are highly sensitive (order of 10−13 strain) and have wide dynamical range (10−13–10−6). Observations with strainmeters (1) and (2) started on June 11, 2003. (3) is a new device for absolute-length measurements of the order of 10−9 of a long-baseline (100 m) Fabry–Perot cavity by the use of phase-modulated light. This third strainmeter will be ready for operation before the end of 2004. The laser source of strainmeters (1) and (2) is a frequency-doubled YAG laser with a wavelength of 532 nm. The laser frequency is locked onto an iodine absorption line and a stability of 2 × 10−13 is attained. The light paths of the laser strainmeter system are enclosed in SUS304 stainless steel pipes. The inside pressure is kept to be 10−4 Pa. Consequently, quantitative measurement of crustal strains of the order of 10−13 can be attained by employing the laser strainmeter system of (1) and (2) at Kamioka. This resolving power corresponds to that of a superconducting gravimeter. Using the laser strainmeter system, we expect to determine parameters related to fluid core resonance, core modes and core undertone as well as other geodynamic signals such as slow strain changes caused by silent earthquakes or slow earthquakes. 相似文献
42.
Estimability analysis of variance and covariance components 总被引:1,自引:1,他引:1
Although variance and covariance components have been extensively investigated and a number of elegant formulae to compute
them have been derived, nothing is known, without any ambiguity, about their estimability in the case of a fully unknown variance–covariance
matrix. We prove that variance and covariance components in this case are not estimable, thus clarifying the ambiguity of
the literature on the topic and correcting some erroneous statements in the literature. We also give a new theorem on the
estimability of a linear function of variance and covariance components. Then we propose a new method to estimate the variance–covariance
matrix with special structure, which can presumably be represented by, at most, r(r + 1)/2 independent parameters to guarantee its estimability in such a subspace, by directly implementing the positive definiteness
of the matrix as constraint to the restricted maximum likelihood method, where r is the number of redundant measurements. Therefore, our estimates of the variance and covariance components always reconstruct
a positive definite matrix and are always physically meaningful. 相似文献
43.
Silicate to Nitrate Ratio of the Upper Sub-Arctic Pacific and the Bering Sea Basin in Summer: Its Implication for Phytoplankton Dynamics 总被引:2,自引:0,他引:2
Isao Koike Hiroshi Ogawa Toshi Nagata Rumi Fukuda Hideki Fukuda 《Journal of Oceanography》2001,57(3):253-260
Consumption of silicate and nitrate (Si:N molar ratio) in the upper layer of the pelagic subarctic Pacific in summer was evaluated by a regression analysis of silicate vs. nitrate concentrations at the upper 100 m depth. Based on data of three cruises, the pelagic subarctic Pacific can be classified into two groups. First group is characterized by roughly 1:1 consumption of silicate and nitrate, and occupies rather larger area of subarcfic Pacific, i.e., the Gulf of Alaska and the Western Subarctic gyre (averaged slope of Si:N linear regression: 1.21, n = 10 and 1.45, n = 9, respectively). Second group is the regions of the Bering Sea basin and the Oyashio region, and showed higher silicate consumption compared to that of nitrate (averaged slope of Si:N linear regression: 2.14, n = 9 and 2.36, n = 3, respectively). The Si:N difference observed is possibly attributed to relative contribution of diatoms production among the phytoplankton assemblages in the regions, i.e., dominance of diatoms production in the regions of the second group. Higher accumulation of ammonium at the bottom of euphotic layer in the summer Bering Sea basin would also contribute to increase consumption ratio of Si:N amounts. 相似文献
44.
Yoshifumi Nogi Kumiko Nishi Nobukazu Seama Yoichi Fukuda 《Marine Geophysical Researches》2004,25(3-4):221-231
The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We
summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived
gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the
Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039–10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn
from NNW–SSE in the south to NNE–SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data
just to the east of Gunnerus Ridge. NNE–SSW structural trends and magnetic anomaly lineation trends that are perpendicular
to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend
NNE–SSW and magnetic polarity changes are normal to them. In contrast, almost NNW–SSE structural trends and ENE–WSW magnetic
polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW–ESE direction
in the south to NNE–SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them
are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence
that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural
trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading
direction from an initial NNW–SSE direction to NNE–SSW. Our results also suggest that these curved structural trends are fracture
zones that formed during initial breakup of Gondwana. 相似文献
45.
Masaaki Fukuda 《Journal of Oceanography》1974,30(2):67-76
The suspended matter in seawater near the bottom is distributed by the effects of sinking and diffusion. The author developed a method of estimation of the vertical eddy diffusivity near the sea bottom and the particle size distribution of bottom sediment, in the case of equilibrium state. This estimation was made by the comparison of measured and computed vertical distribution of beam attenuation. The parameters which were used for the computation were (1) median of the particle size distribution of bottom sediment, assuming that the particle size was a log-normal distribution, and (2) the proportional constant of vertical eddy diffusivity which was proportional to the height from the bottom.As the suspended matter in seawater contains particles of different sizes, the computation of the diffusion and beam attenuation was made for each particle size, and summarizing the results, the vertical distribution of beam attenuation coefficient was computed.In order to estimate the beam attenuation in high particle concentration, an equation by which the effect of overlapping of particle shadow in the light beam was eliminated, was used. 相似文献
46.
47.
WANG Xichang Yutaka Fukuda CHEN Shunsheng Masahito Yokoyama CHENG Yudong YUAN Chunhong QU Yinghong Morihiko Sakaguchi 《中国海洋大学学报(英文版)》2005,4(3):229-233
According to the three-dimensional contour maps showing the gel-forming properties of surimi derived from freshwater fish, 8 species of surimi were classified into two types. The-valley type surimi (silver carp, big-head carp, Chinese snake head and blunt snout bream) shows easy setting, low resistance to gel collapse, high enhancement ability with two-step heating, and narrow optimum heating temperature and time area, which are of the same characteristics as the walleye pollack surimi. In contrast, the Plateau type surimi (tilapia, grass carp, mud carp and common carp) exhibits difficult setting, high resistance to gel collapse, no enhancement ability with two-step heating, and wide optimum heating temperature and time area. There are seasonal changes of gelling properties of silver carp surimi, and the setting ability of surimi gel is higher in winter and lower in summer. The marine fish meat gels and the freshwater fish meat gels have the same acceptability for inland Chinese according to the sensory evaluation results. A slight increase in sensory scorings of kamaboko gels occurred when the extract from walleye pollack muscle was added, especially in the odor scoring of silver carp kamaboko gels. 相似文献
48.
Sang Hoon Lee Jang J. Bahk Han J. Kim Kyung E. Lee Hyeong T. Jou Bong C. Suk 《Geo-Marine Letters》2010,30(2):133-142
The depositional characters of densely dated turbidite successions originating from the southwestern margin of the Ulleung
Basin reveal changes in high-resolution frequency, failing areas, and relative volumes of slope failures over the past 29.4
cal. ka. Between 29.4 and 19.1 cal. ka B.P., various thin- to very thick-bedded turbidites accumulated at an average recurrence
interval of ca. 605 years. After 19.1 cal. ka B.P., turbidites were deposited with an average recurrence interval of 3,183
years, and their thickness abruptly decreased upward. These features suggest that various-scale slope failures occurred frequently
during the eustatic lowering of sea level, and the frequency and relative volumes of slope failures suddenly decreased after
sea level began to rise. When sea level was lowest (20.0–19.1 cal. ka B.P.), successive stacks of very thick turbidites can
most likely be ascribed to larger-volume mass failures. An upward change from muddy to sandy turbidites around 21.4 cal. ka
B.P. suggests that the failing areas retrograded from the muddy upper-middle slope to the sandy uppermost slope when sea level
was nearly at its lowest. Based on these findings together with published evidence, frequent mass failures between 29.4 and
19.1 cal. ka B.P. were plausibly triggered by earthquakes, in combination with reduced hydrostatic pressure that promoted
gas-hydrate dissolution during the eustatic lowering of sea level. These data on the frequency, scale, failing areas, and
triggering causes of slope failures along the southwestern margin over the past 29.4 cal. ka, not documented in earlier studies,
provide invaluable information to better understand the basin-scale characters and occurrences of latest Quaternary slope
failures in the Ulleung Basin. 相似文献
49.
Christopher E. Ndehedehe Joseph L. Awange Michael Kuhn Nathan O. Agutu Yoichi Fukuda 《水文研究》2017,31(18):3206-3224
There is some evidence of rapid changes in the global atmosphere and hydrological cycle caused by the influence of climate variability. In West Africa, such changes impact directly on water resources leading to incessant extreme hydro‐meteorological conditions. This study examines the association of three global climate teleconnections—El‐Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Atlantic Multi‐decadal Oscillation (AMO) with changes in terrestrial water storage (TWS) derived from both Modern‐Era Retrospective Analysis for Research and Applications (MERRA, 1980–2015) and Gravity Recovery and Climate Experiment (GRACE, 2002–2014). In the Sahel region, positive phase of AMO coincided with above‐normal rainfall (wet conditions) and the negative phase with drought conditions and confirms the observed statistically significant association (r = 0.62) between AMO and the temporal evolutions of standardised precipitation index. This relationship corroborates the observed presence of AMO‐driven TWS in much of the Sahel region (though considerably weak in some areas). Although ENSO appears to be more associated with GRACE‐derived TWS over the Volta basin (r =?0.40), this study also shows a strong presence of AMO‐ and ENSO‐induced TWS derived from MERRA reanalysis data in the coastal West African countries and most of the regions below latitude 10°N. The observed presence of ENSO‐ and AMO‐driven TWS is noticeable in tropical areas with relatively high annual/bimodal rainfall and strong inter‐annual variations in surface water. The AMO has a wider footprint and sphere of influence on the region's TWS and suggests the important role of North Atlantic Ocean. IOD‐related TWS also exists in West Africa and its influence on the region's hydrology maybe secondary and somewhat complementary. Nonetheless, presumptive evidence from the study indicates that ENSO and AMO are the two major climatic indices more likely to impact on West Africa's TWS. 相似文献
50.
Mario?UchimiyaEmail author Hideki?Fukuda Shigeto?Nishino Takashi?Kikuchi Hiroshi?Ogawa Toshi?Nagata 《Journal of Oceanography》2011,67(5):589-599
This study examined possible environmental factors that affect prokaryote variables in surface waters (upper 100 m of water
column) in the Canada Basin, western Arctic Ocean. We collected data on prokaryote abundance and heterotrophic production
([3H]leucine incorporation) at eight stations deployed along a slope-to-offshore transect during September 2009. Prokaryote production
and growth tended to increase with increasing chlorophyll a (Chl. a) and temperature and with decreasing salinity. The combination of Chl. a, temperature, and salinity accounted for a large fraction (74%) of the variability in prokaryote production, with the highest
contribution made by Chl. a (r
2 = 0.56), followed by salinity (r
2 = 0.14) and temperature (r
2 = 0.03). Similarly, the variability in prokaryote growth rate was largely accounted for by the combination of the three environmental
variables (overall r
2 of 0.64), with Chl. a making the largest contribution to variability (r
2 = 0.33), followed by salinity (r
2 = 0.27) and temperature (r
2 = 0.05). These data are consistent with the notion that organic matter supply associated with freshwater inputs to surface
layers can result in enhanced prokaryote production and growth in the Canada Basin. Our results provide insights into the
regulation of the microbial loop in the Canada Basin where freshening has been proceeding rapidly due to increasing river
discharge and sea-ice melting. 相似文献