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51.
Surface-correlated noble gases in lunar soils are primarily implanted SW (solar wind) noble gases. However, they also include apparently orphan radiogenic 40Ar, 129Xe, and 244Pu-derived fission Xe in excess of plausible primordial solar origin. These orphan radiogenic components are usually assigned a lunar origin, in a scenario in which radiogenic noble gases produced in the lunar interior were degassed into the transient atmosphere and then re-implanted to the lunar surface together with SW. There are some quantitative difficulties with this scenario, however, and it requires special constraints on the degassing history of the Moon that have not emerged from more general thermal history models. We therefore urge consideration of alternative hypotheses. As a possible source for the orphan radiogenic noble gases, we have examined planetary pollution of the Sun, as suggested by studies of extrasolar planetary systems (e.g., Murray et al., 2001, Astrophys. J. 555, 801-815; Israelian et al., 2001, Nature 411, 163-166). Pollution of the Sun by 2M⊕ (two Earth mass) planetary materials (Murray et al., 2001, Astrophys. J. 555, 801-815) is likely not significant for Ar but could be important to account for orphan Xe in the Moon. 相似文献
52.
Yasunori Nejoh 《Astrophysics and Space Science》1992,198(2):309-319
We derive a mixed modified Korteweg-de Vries (MK-dV) equation from a semi-relativistic ion acoustic wave with hot ions by the fluid approximation. The positive cubic nonlinearity of the mixed MK-dV equation give rise to the periodic progressive waves and the algebraic solitary waves. The periodic wave bears a series of solitary pulses, and the algebraic solitary wave reduces the rarefactive solitary wave in the limit of the particular boundary condition. These nonlinear wave modes explain, respectively, the periodic pulse of the potential and the rarefactive solitary wave of the fine structure observed in space. 相似文献
53.
N. Sugiura K. Hashizume Y. Miura K. Kiyota S. Zashu 《Meteoritics & planetary science》1995,30(6):646-653
Abstract— The isotopic disequilibrium of N molecules in meteorites was examined. For a large data-set, consisting of mass compositions of N molecules extracted at 1200 °C by stepped combustion of chondrites and eucrites, we find that a cosmogenic-N-enriched component and a normal air-like N component are isotopically disequilibrated with each other. The isotopic composition of the cosmogenic-N-enriched component seems to be variable, although the cause for the variation is not clear. The abundance of indigenous atomic N in silicate minerals seems to be small. Indigenous N in meteoritic silicates, if present, may be present in the form of N molecules. 相似文献
54.
Chondrule formation due to the shock wave heating of dust particles with a wide variety of shock properties are examined. We numerically simulate the steady postshock region in a framework of one-dimensional hydrodynamics, taking into account many of the physical and chemical processes that determine the properties of the region, especially nonequilibrium chemical reactions of gas species. We mainly focus on the dust particle shrinkage due to the evaporation in the postshock hot gas and the precursor size conditions for chondrule formation. We find that the small precursors whose radii are smaller than a critical value, , cannot form chondrules because they evaporate away completely in the postshock region. The minimum value of is about 10 μm, though it depends on the shock speed and the preshock gas density. Furthermore, we demonstrate the chondrule size distributions which are formed through the shock-wave heating. These results indicate that the shock-wave heating model can be regarded as a strong candidate for the mechanism of chondrule formation. 相似文献
55.
A one-dimensional numerical model with a level-2.5 turbulent closure scheme to provide vertical mixing coefficients has been
used to investigate the process by which the dichothermal water is formed in the Bering Sea, the density of which is about
26.6 sigma-theta. The water column to be simulated is assumed to move along a predetermined path. That is, the present model
is of the Lagrangian-type. Surface boundary conditions are given using the climatologies of heat, freshwater and momentum
fluxes. In order to obtain a plausible moving speed of the water column along the path, pre-liminary experiments were done
using the surface fluxes in the central part of the Bering Sea for the initial temperature and salinity profiles at the entrance
of the Sea. As a result, it was found that the temperature minimum layer, i.e., the dichothermal water with temperature similar
to the climatology at the exit of the Bering Sea, was formed after about two years of integration. Based on the result, the
movement speed of the water column along the path was set as 4.5 cm/s in the standard run. It was found that this model could
plausibly reproduce the subsurface temperature minimum layer. That is, the dichothermal water was formed in the winter mixed
layer process in the Bering Sea. The existence of the subsurface halocline (pycnocline) prohibited the deeper penetration
of the winter mixed layer, and therefore water with a temperature colder than that under the mixed layer was formed in the
mixed layer due to wintertime surface cooling. In the warming season this water remains as the subsurface temperature minimum
layer between the upper seasonal thermocline and the lower halocline.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
The temperature minimum layer, called “dichothermal water”, is a characteristic feature of the North Pacific subarctic gyre.
In particular, dichothermal water having a density of approximately 26.6 sigma-theta (σθ), which corresponds to the densest water outcropping in winter in the North Pacific, is seen in the Bering Sea. In order
to clarify the water properties, and the area in which and the process by which the dichothermal water is formed, a new seasonal
mean gridded climatological dataset with a fine resolution for the Bering Sea and adjacent seas has been prepared using historically
accumulated hydrographic data. Although the waters of the Alaskan Stream have temperature minimum layers, their temperature
inversions are very weak in climatologies and the core densities of the temperature minimum layers are much lighter than 26.6σθ. On the other hand, in the Bering Sea one can see the robust structure of temperature minimum layers, the core density of
the dichothermal water being around 26.6σθ. In addition, it has been found that the properties of the dichothermal water observed in the warming season are almost the
same as those in the winter mixed layer. That is, the dichothermal waters are formed in the winter mixed layer in the Bering
Sea. Since these waters are found in the Kamchatka Strait, i.e., the main exit of the Bering Sea waters, it can be supposed
that the dichothermal waters are exported from the Bering Sea to the Pacific Ocean by the Kamchatka Current.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
57.
Feeding Habits of the Mesopelagic Fish Gonostoma gracile in the Northwestern North Pacific 总被引:1,自引:0,他引:1
The diet of Gonostoma gracile, a numerically abundant mesopelagic fish in the Subtropical Region and the Transition Domain of the northwestern North Pacific,
was examined using 520 specimens collected during June–July 1988, June 1995 and November 1995. The prey included mainly copepods,
ostracods, amphipods and euphausiids. Copepods and ostracods were the most abundant, comprising approximately 70% of the total
diet. There was little evidence of an ontogenetic dietary shift; Pleuromamma copepods were the most abundant prey for all size classes of fish ranging from 19 to 116 mm in standard length. The size
range of prey increased with growth, but all fish sizes examined fed mainly on 1–4 mm long prey. Luminescent copepods and
ostracods were the most abundant prey, suggesting that G. gracile detects its prey visually.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
58.
59.
基于银因其具有良好的广谱抗茵活性和低毒性而在医学方面有着较为广泛的应用,对银离子(硝酸银)和含银不锈钢的抗茵活性进行了初步研究。实验结果表明,在10^6CFu/mL的初始接种浓度下,银离子对枯草杆菌、大肠杆菌和假单胞茵的最小抑茵质量浓度和最小杀菌质量浓度分别为2,6,8mg/L和2,8,10mg/L。大肠杆菌经8mg/L的银离子处理2h后,有99.9%以上的细菌被破坏。含银不锈钢也表现了较强的抗菌性能。在普通的、银合金和银涂层的sus304不锈钢表面附着的单层生物膜浸泡在PBS溶液中3d后,经CFDA-DAPI双染色和荧光显微镜观察计数获得的假单胞菌的平均存活率为98.0%,38.5%和15.1%。 相似文献
60.