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81.
Operational Data Assimilation System for the Kuroshio South of Japan: Reanalysis and Validation 总被引:3,自引:5,他引:3
Masafumi Kamachi Tsurane Kuragano Hiroshi Ichikawa Hirohiko Nakamura Ayako Nishina Atsuhiko Isobe Daisuke Ambe Masazumi Arai Noriaki Gohda Satoshi Sugimoto Kumi Yoshita Toshiyuki Sakurai Francesco Uboldi 《Journal of Oceanography》2004,60(2):303-312
We describe an operational ocean data assimilation system for the Kuroshio and its validation using a nine-year reanalysis
(historical run from 1993 to 2001) dataset of upper-ocean state estimation in the North Pacific. The horizontal structure
of volume transport of the Ryukyu Current System (RCS) is shown from the reanalysis: The RCS is connected to the flow of the
subtropical gyre, and its volume transport gradually increases from south-east of Okinawa (5–10 Sv) to the east of Amami-Ohshima
Island (20 Sv). Comparing the reanalysis with independent observations on the southeast slope of the Amami-Ohshima Island
indicates that the root mean square differences (RMSDs) are 0.076 (0.037) m/s in the period of December 1998 to November 1999
(November 1999 to November 2000) respectively. The reanalysis field has a bias (3.1 Sv) of the volume transport of the RCS
and the RMSD (3.5 Sv) which is larger than the observed variability (2.81 Sv). Surface velocity and the Kuroshio axis south
of Japan are also examined. Comparison of the reanalysis and ADCP data gave maximum RMSD of 0.749 (0.271) m/s in the strong
(weak) current regions, respectively. The annual mean value of the axis error is 19 km in 1998. The RMSD of the error is at
most 50 km, in 294 cases in the observation period, which is smaller than the observed root mean square variability of the
axis (64 km).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
82.
Experimental investigation on cohesionless sandy bank failure resulting from water level rising 总被引:1,自引:1,他引:0
In the last decade, sediment replenishment forming cohesionless sandy banks below dams has become an increasingly common practice in Japan to compensate for sediment deficits downstream. The erosion process of the placed cohesionless sediment is a combination of lateral toe-erosion and the following mass failure. To explore cohesionless bank failure mechanisms, a series of experiments was done in a soil tank using a compacted sandy soil mass exposed to an increasing water level. Two types of uniform sand(D_(50) = 0.40 mm and 0.17 mm) and two bank heights(50 cm and 25 cm) were used under the condition of a constant bank slope of 75°. The three dimensional(3D) geometry of the bank after failure was measured using a handheld 3D scanner. The motion of bank failure was captured using the particle image velocimetry(PIV) technique, and the matric suction was measured by tensiometers. The compacted sandy soil was eroded by loss of matric suction accompanying the rise in water level which subsequently caused rotational slide and cantilever toppling failure due to destabilization of the bank. The effect of erosion protection resulting from the slumped blocks after these failures is discussed in the light of different failure mechanisms. Tensile strength is analyzed by inverse calculation of cantilever toppling failure events. The tensile strength had non-linear relation with degree of saturation and showed a peak.The findings of the study show that it is important to incorporate the non-linear relation of tensile strength into stability analysis of cantilever toppling failure and prediction of tension crack depth within unsaturated cohesionless banks. 相似文献
83.
Takehiko Suzuki Seiji Maruyama Tohru Danhara Takafumi Hirata Hiroshi Machida Fusao Arai 《第四纪科学杂志》2020,35(1-2):316-333
Tephra fingerprinting techniques contributing to volcanology and palaeoenvironmental studies have been developed using a combination of laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). In particular, femtosecond LA-ICP-MS can determine major- and trace element abundances in individual glass shards. On the basis of the major oxide and trace element composition of the glass shards, using those methods, we re-examined the identification of four lower Pleistocene tephras originating from north-east Japan. All trace element abundances exhibited the typical pattern of tephras from the Hokkaido–Tohoku area, and major element concentrations were distinct. As a result, we re-examined the correlation of the widespread Tmg-R4 tephra (2.0 Ma), and newly defined the widespread Kd44-Naka tephra (1.968–1.781 Ma), both originating from the Sengan geothermal region. Furthermore, we re-examined identifications of Sr-Asn-Kd8 (1.219 Ma) and Sr-Kc-U8 (0.922–0.910 Ma) in central Japan, both derived from the Aizu volcanic region. The extensive distributions of the former two tephras suggest the occurrence of two large caldera-forming eruptions (Volcanic Explosivity Index 7) during a short period. Also, the distributions and volumes of the latter two tephras are broader and larger than those previously assumed. The results provide insight into large volcanic eruption history and terrestrial and marine palaeoenvironmental history. 相似文献
84.
Late Paleozoic blueschists present good exposures in the Pateyar metamorphic complex (south of Chupanan, Isfahan Province). They are formed by metamorphism of primitive basaltic lavas. Petrography and microprobe analyses show that the studied rocks consist of glaucophane, actinolite, actinolitic hornblende, plagioclase (albite), sphene, magnetite, quartz and apatite. Secondary minerals are epidote, chlorite, pyrite, hematite and calcite. Mineralogical assemblages are consistent with blueschist facies metamorphism, which is followed by a retrograde metamorphism in greenschist facies. Estimation of the metamorphic conditions suggests 300–400°C and 7–11 kbar. Chemical signatures of the studied metamorphic rocks conclude that they retain main geochemical characteristics of the protoliths, which allow the petrochemical interpretations. Geochemical analyses of these blueschists show that they were originally tholeiitic basalts. Evident negative anomalies of Nb, Ta and Ti relative to Th, La and Ce, in the primitive mantle normalized spider-gram, reveal subduction role in their petrogenesis. The studied metavolcanics exhibit an intermediate chemistry between the N-MORB (normal mid-ocean ridge basalt) and IATB (island arc tholeitic basalt). Enrichment in LREE (light rare earth elements) and LILE (large ion lithophile elements) and relative depletion in HFSE (high field strength elements) suggest a back-arc basin paleotectonic setting for the Chupanan samples. The primitive magma of the analyzed samples possibly have been produced by 8–13% melting of a spinel lherzolite. The field and petrological data propose that the studied Paleozoic metavolcanics were formed in a back-arc basin above the northward subduction of Paleo-Tethys oceanic lithosphere in Central Iran. The chemical criteria of the LILE/HFSE ratio suggests that the subduction zone was young and immature during the volcanism. 相似文献
85.
Hiroshi Nagaoka Yuzuru Karouji Tomoko Arai Mitsuru Ebihara Nobuyuki Hasebe 《Polar Science》2013,7(3-4):241-259
The lunar meteorite Northwest Africa (NWA) 2200 is a regolith breccia with a ferroan feldspathic bulk composition (Al2O3 = 30.1 wt.%; Mg# = molar 100 × Mg/(Mg + Fe) = 59.2) and low Th content (0.42 μg/g). Lithologically, NWA 2200 is a diverse mixture of lithic and glassy clasts, mineral fragments, and impact glass spherules, all embedded in a dark glassy matrix. NWA 2200 contains some feldspathic brecciated rock components (ferroan anorthositic granulitic breccia, poikiloblastic granulitic breccia, and glassy melt breccia with an intersertal texture). The bulk compositions of these brecciated components indicate they are derived from ferroan troctolitic or noritic anorthosite lithologies (bulk Al2O3 = 26–30 wt.%; bulk FeO/MgO > 1.0). The bulk composition of NWA 2200 is more ferroan and feldspathic than the Apollo feldspathic regolith samples and feldspathic lunar regolith meteorites, and is also more depleted in incompatible elements (e.g., rare earth elements) than Apollo 16 feldspathic regolith samples. We conclude that NWA 2200 originated from a location different to the Apollo landing sites, and may have been sourced from the ferroan KREEP-poor highlands, “KREEP” materials are enriched in such elements as potassium (K), rare earth elements (REE), phosphorus (P). 相似文献
86.
87.
To examine the accumulation pattern of organotins (OTs) in relation to the migration of diadromous fish, tributyltin (TBT) and triphenyltin (TPT) and their derivatives were determined in the muscle tissue of both sea-run (anadromous) and freshwater-resident (nonanadromous) types of the white-spotted charr Salvelinus leucomaenis. Ontogenic changes in otolith strontium (Sr) and calcium (Ca) concentrations were examined along life history transect to discriminate migration type. Mean Sr:Ca ratio from the core to the edge of the otolith in sea-run individuals was significantly higher than those in freshwater-resident one. There were no significant correlations in S. leucomaenis between OT accumulation and various biological characteristics. It is noteworthy that TBT and TPT concentrations in sea-run type were significantly higher than those in freshwater-resident individuals, although they are both of the same species. These results suggest that sea-run S. leucomaenis have a higher ecological risk of OT exposure than freshwater-residents during their life histories. 相似文献
88.
Condensed aromatic rings are important skeletal components with regard to the recalcitrant nature of humic acids (HAs) in the environment. However, they have not been extensively studied. The relative content and composition (size distribution) of condensed aromatic rings in HAs were obtained from various soils subjected to transmission electron microscopy (TEM) and X-ray diffraction (XRD) profile analysis. In the XRD profiles of all the HAs, the 11 band that was derived from the carbon layer planes was clearly observed. Analysis of the 11 band indicated that the size of the carbon layer planes in HAs ranged from 0.48-1.68 nm, corresponding to 4- to 37-ring condensed aromatic structures. The contents of the total and larger carbon layer planes were larger in HAs with darker color and larger aromatic carbon content. At the same time, the carbon layer planes in HAs were smaller than those in a carbon black reference (from 0.24 to >3.66 nm). In the TEM analysis, fringes observed in HAs were less distinct and less ordered than those in carbon black, which was in agreement with the XRD result. 相似文献
89.
In analyses of compositional data, it is important to select a suitable unchanging component as a reference to detect the
behavior of a single variable in isolation. This paper introduces two tests for detecting the unchanging component, based
on a new approach that utilizes the coefficient of variation of component ratios. That is, the coefficient of variation of
a compositional ratio is subject to change when the unchanging component is switched between the denominator and numerator,
and the coefficient of variation tends to be small when the unchanging component occurs as the denominator against any arbitrary
components (Test 1). In addition, the ratio of the component pair that gives the lowest coefficient of variation is most likely
to represent the two unchanging components (Test 2). However, Tests 1 and 2 are not necessary and sufficient conditions for
uniquely finding the unchanging component. To verify the effectiveness of the tests, 500 artificial datasets were analyzed
and the results suggest that the tests are able to identify the unchanging component, although Test 1 underperforms when the
dataset includes a component with skewness greater than 0.5, and Test 2 fails when the dataset includes components with a
correlation coefficient greater than 0.75. These defects can be overcome by interpreting the two test results in a complementary
manner. The proposed tests provide powerful yet simple criteria for identifying the unchanging component in compositional
data; however, the reliability of this approach needs to be assessed in further studies. 相似文献
90.
Dynamical behaviour of an evaporating black hole is investigated for a Vaidya-type metric. The Raychaudhuri equation is examined with including terms up to the second order in the luminosity near the event horizon. Such a solution is found that the luminosity increases as the mass decreases during the evaporation. 相似文献