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51.
52.
Kiwamu Nishida 《Comptes Rendus Geoscience》2011,343(8-9):584-590
Ambient noise tomography has now been applied at scales ranging from local to global. To discuss the theoretical background of the technique, a simple form of a two-dimensional (2-D) Born sensitivity kernel was developed at a finite frequency for a cross-correlation function (CCF) of background surface waves. The use of far field representations of a Green’s function and a CCF in a spherically symmetric Earth model, assuming a homogeneous source distribution, is an efficient approach to the calculation of phase sensitivity kernels. The forms of a phase sensitivity kernel for major and minor arc propagations are the same as those for phase-velocity measurements of earthquake data. This result indicates the validity of ambient noise tomography under the given assumptions; however, the kernels are not equivalent in the case of an inhomogeneous source distribution. 相似文献
53.
Ryuji Tateyama Eiji Ohtani Hidenori Terasaki Keisuke Nishida Yuki Shibazaki Akio Suzuki Takumi Kikegawa 《Physics and Chemistry of Minerals》2011,38(10):801-807
The compositional dependence on the density of liquid Fe alloys under high pressure is important for estimating the amount
of light elements in the Earth’s outer core. Here, we report on the density of liquid Fe–Si at 4 GPa and 1,923 K measured
using the sink–float method and our investigation on the effect of the Si content on the density of the liquid. Our experiments
show that the density of liquid Fe–Si decreases from 7.43 to 2.71 g/cm3 non-linearly with increasing Si content (0–100 at%). The molar volume of liquid Fe–Si calculated from the measured density
gradually decreases in the compositional range 0–50 at% Si, and increases in the range 50–100 at% Si. It should be noted that
the estimated molar volume of the alloys shows a negative volume of mixing between Fe and Si. This behaviour is similar to
Fe–S liquid (Nishida et al. in Phys Chem Miner 35:417–423, 2008). However, the excess molar volume of mixing for the liquid Fe–Si is smaller than that of liquid Fe–S. The light element
contents in the outer core estimated previously may be an underestimation if we take into account the possible negative value
of the excess mixing volume of iron–light element alloys in the outer core. 相似文献
54.
Shotaro Suzuki Ryo Kaneko Taketoshi Kodama Fuminori Hashihama Shuhei Suwa Iwao Tanita Ken Furuya Koji Hamasaki 《Journal of Oceanography》2017,73(3):383-395
The subtropical and tropical regions of the Pacific Ocean are less productive than other oceanic regions. Although particle association should be an important strategy for heterotrophic prokaryotes to survive in such environments, we have little information on particle-associated (PA) prokaryotes in these regions. The specific aim of this study was to determine bacterial and archaeal community structures in the PA assemblage in comparison to the free-living (FL) assemblage in the North Pacific Subtropical Gyre, the South Pacific Subtropical Gyre, and an eastern equatorial region of the Pacific Ocean. Community profiles and phylogenetic identities were obtained by denaturing gradient gel electrophoresis, 454-pyrosequencing, and cloning followed by Sanger sequencing of 16Sr RNA gene amplicons. The distribution patterns of some abundant groups in three regions and two lifestyles (PA and FL) are shown in this study. Also, the PA community structures of bacteria differed from the FL ones and exhibited higher diversity than the FL ones, while the archaeal community structures did not show significant differences between PA and FL assemblages. We found that specific phylotypes of Gammaproteobacteria and Flavobacteria were abundant in PA bacterial assemblages, suggesting that they prefer to attach and consume particulate organic matter. In summary, the surface seawater PA assemblages represent very different bacterial and archaeal community structures between three different oceanic regions, each of which had distinct PA and FL community structures. These results imply that environmental factors determine microbial community structures. 相似文献
55.
Fuminori Hashihama Shinko Kinouchi Shuhei Suwa Masahiro Suzumura Jota Kanda 《Journal of Oceanography》2013,69(3):357-367
Trace concentrations of labile dissolved organic phosphorus (LDOP) in oligotrophic seawater were measured by use of an enzymatic procedure and a nanomolar phosphate analytical system consisting of a gas-segmented continuous flow analyzer with a liquid waveguide capillary cell. LDOP, defined as DOP hydrolyzed by alkaline phosphatase (AP) from Escherichia coli, was quantified as the difference between the phosphate concentrations of the seawater sample with and without AP treatment. For sensitive measurement of LDOP, we found that phosphate contamination derived from commercially available AP must be corrected, and azide treatment before AP treatment proved effective in removing biological effect that occurs during DOP hydrolysis. Field observations at six stations of the western North Pacific and the East China Sea during the boreal summer revealed that, in the upper 200 m of the water column, LDOP concentrations ranged from the detection limit (3 nM) to 243 nM, and phosphate concentrations ranged from 5 to 374 nM. The spatial distribution patterns of LDOP were similar to those of phosphate. Most of the depth profiles for LDOP and phosphate showed concentrations were extremely low, <25 nM, between the surface and the deep chlorophyll maximum layer (DCML) and increased below the DCML. Strongly depleted LDOP and phosphate above the DCML suggest that LDOP is actively hydrolyzed under phosphate-depleted conditions and utilized by microbes. 相似文献
56.
Potential and gravity changes raised by point dislocations 总被引:9,自引:0,他引:9
Shuhei Okubo 《Geophysical Journal International》1991,105(3):573-586
57.
T. Tanabé S. Nishida Y. Nakada T. Onaka I.S. Glass M. Sauvage 《Astrophysics and Space Science》1997,255(1-2):407-413
We report preliminary results of our systematic survey for infrared stars in the globular clusters of the Magellanic Clouds.
In the course of an ISOCAM survey for AGB stars in the intermediate-age clusters, we have discovered extremely red AGB stars
in NGC 419 and NGC 1978. From their colours and luminosities, they are thought to be experiencing intense mass-loss and to
be in the final or superwind phase of the AGB evolution. However, they seem to be of somewhat lower luminosity than the corresponding
visible AGB stars when only the mid-infrared data are taken into account. This suggests that hitherto unobserved infrared
excesses may exist at longer wavelengths.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
58.
Bottom mud was collected from the upper and lower reaches of 92 rivers in Japan to determine the distribution of 0.5N-HCI-soluble
heavy metals. The average concentrations of Cu, Zn, Pb, and Cd in the mud from the lower reaches were from two to three times
higher than those in the upper reaches. Japanese rivers were classified according to the degree of heavy metal pollution by
using the values of 0.5N-HCI-soluble metals in the lower reaches of rivers. The content of 0.5N-HCI-soluble heavy metals in
the mud of the upper reaches was used as the standard value. The classification of rivers was made by a cluster analysis according
to Euclidian distance. As a result, rivers in Japan could be classified into three groups based on the degree of metal pollution,
and the classification was in agreement with the pollution index. 相似文献
59.
The two-dimensional equation of motion containing the pressure gradient and Coriolis force is numerically solved for the wind field in and above the layers of a horizontally homogeneous canopy with a vertical distribution of leaf-area densities. The solution shows that, in the case of descending through the canopy, the wind vector turns with an angle which depends on the profile of leaf-area densities. In particular, for the canopy of a forest consisting of upper layers with higher densities and lower layers with smaller densities, the turning is striking; a secondary maximum in wind profile appears in the lower layers.Variations of the aerodynamic parameters for the flow above the canopy are indicated with respect to the leaf-area density. The roughness length varies in such a manner that a maximum appears in intermediate density values, depending on the shape of the profile of leaf-area density. In the case of very dense canopies, the shearing stress acting on the flow above the canopy is determined by the contribution from only the upper canopy elements, but not by that from the lower parts of the canopy. 相似文献
60.
Shingo Yamada Forecast Division Japan Meteorological Agency Tokyo Japan Shuhei Maeda Administration Division Climate Marine Department Japan Meteorological Agency Tokyo Japan K. Gambo c/o Department of Earth Planetary Physi 《大气科学进展》1997,(1)
NotesonExtended-RangeAtmosphericPredictionintheNorthernHemisphereWinterShingoYamadaForecastDivision,JapanMeteorologicalAgency... 相似文献