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1.
Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on
a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like
structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the
slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the
high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric
subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur)
in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical
experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear
is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the
semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial
current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role
in transferring energy from high-mode internal tides to near-inertial internal waves. 相似文献
2.
Infrared (IR) and nearinfrared (NIR) absorption spectra of hydrous and F-rich topazes were measured to assign an OH bending
mode of topaz. Three absorption peaks at 1165, 3650, and 4803 cm−1 are assigned to OH related absorption peaks. Since a peak at 4803 cm−1 can be assigned to a combination mode of 1165 and 3650 cm−1, the 1165 cm−1 peak is harmonic with the 3650 cm−1 peak. Polarized IR absorption spectra of (100), (010), and (001) planes of the hydrous topaz were measured to examine IR
active orientation of the 1165 cm−1 OH related mode. Three pleochroic distributions of the absorption peak at 1165 cm−1 on (100), (010), and (001) planes indicate an active orientation of the 1165 cm−1 OH related mode. The IR active orientation of the 1165 cm−1 OH related mode in topaz is normal to the OH dipole. The orthogonality and harmonic combination mode indicate that the 1165 cm−1 peak is OH bending mode. The active orientation of OH bending mode is polarized in the plane normal to the OH dipole. The
polarization suggests that anisotropic thermal vibration of protons on the hydroxyl is maximum along the IR active orientation.
Received: August 16, 1996 / Revised, accepted: April 20, 1997 相似文献
3.
Nao Nakanishi Tetsuya Yokoyama Satoki Okabayashi Tomohiro Usui Hikaru Iwamori 《Meteoritics & planetary science》2018,53(5):1051-1065
We report Os isotope compositions of metal grains in two CBa chondrites (Bencubbin and Gujba) determined using a micromilling sampling coupled with thermal ionization mass spectrometry, together with the abundances of major and trace siderophile elements obtained by electron probe microanalysis and femtosecond laser ablation inductively coupled plasma–mass spectrometry. The CBa metal grains presented 187Os/188Os ratios akin to carbonaceous chondrites with limited variations (0.1257–0.1270). Most of the CBa metal grains were scattered along a 187Re-187Os reference isochron of IIIAB iron meteorites, indicating that the CBa metals experienced limited Re-Os fractionation at the time of their formation. The Re/Os ratios of sampling spots for the CBa metals, recast from the observed 187Os/188Os ratios, had a positive correlation with their Os/Ir ratios. In addition, the metal grains showed a positive correlation in a Pd/Fe versus Ni/Fe diagram. These correlations suggest that the CBa metal grains have formed via equilibrium condensation or evaporation from a gaseous reservoir at ~10−4 bar with enhanced metal abundances. Compared to the Bencubbin metals, the Gujba metals are characterized by having systematically lower Pd/Fe and Ni/Fe ratios that span subchondritic values. Such a difference was most likely induced by the compositionally heterogeneous impact plume from which the metals were condensed. 相似文献
4.
Abstract The Cetacea are the most diverse and highly aquatically adapted group of mammals. Their fossil record extends back at least to the Middle Eocene ( ca 50 Ma), and they will possibly be found earlier, judging by the relatively highly evolved nature of the earliest known whales. The most likely terrestrial ancestors of whales are the mesonychids, primitive hoofed mammals with omnivorous diets. Recently discovered archaeocetes with large, mesonychid-like heads and dentitions and functional hind limbs reconfirm earlier ideas about the mesonychid origin of cetaceans and the amphibious nature of the earliest transitional forms. Fossil cetaceans are relatively abundant and diverse thoughout the world, and are now known from every continent, including Antarctica. Odontocetes evolved echolocation to locate food. Mysticetes developed bulk feeding adaptations. Both undoubtedly evolved from archaeocetes, and the monophyly of Cetacea is the most parsimonious present hypothesis. Chromosomal and molecular evidence has taken an increasingly important role in determining cetacean relationships, but fossils and classical comparative morphological studies remain a necessary and pivotal source of information about cetacean phylogeny. 相似文献
5.
Tadashi Akamatsu Mineo Kumazawa Nobuyuki Aikawa Humihiko Takei 《Physics and Chemistry of Minerals》1993,19(7):431-444
The divalent cation distribution in olivine (Mg, Fe)2SiO4 under high pressure and temperature was studied to clarify the detailed state of olivine in the mantle. Single crystal samples were heated for a sufficient period of time for the cations to migrate and quenched fast enough to preserve the equilibrated state under high pressures, and the crystal structure was determined with X-ray method. The pressure effect on the distribution coefficient K D[= (Fe/Mg) M1/(Fe/Mg) M2] was determined for the first time; dK D/dP?0.02 GPa?1. A set of five thermodynamic parameters required to describe the regular solution model was determined from data concerning the pressure dependence and the known temperature and compositional effects. As a result we have shown how K D depends on pressure, temperature, and composition. The notable feature clarified is the very large contribution of nonideality in the olivine solid solution. The K D of olivine crystals in the mantle is predicted; K D increases to ~ 2.2 at the depth of 400 km, in contrast to 0.9 ~ 1.2 of natural samples available at the surface of the Earth. 相似文献
6.
Concentrations of Fe, Zn, Cu, Se, Mn, Mo, Hg, Cd, Cr, Ag, Pb, Sr and V were determined in skins of Dall's porpoises (Phocoenoides dalli) of the Pacific coast truei-type population (PT population) (N=45), and the Sea of Japan-Okhotsk dalli-type population (JD population) (N=31) from the northern waters of Japan. Cutaneous Hg concentrations in both PT and JD populations were significantly correlated with age, indicating a possible alternative method of age estimation. A significant correlation was also noted between Hg concentrations in skin and liver, suggesting that biopsy samples of skin can provide a non-lethal surrogate for monitoring Hg contamination in this species. Trace element accumulation patterns differed strongly between PT and JD populations, when analyzed by principal component analysis, suggesting these patterns could be utilized as non-lethal tracers of population identification. 相似文献
7.
In order to investigate the behaviour of proton in brucite under pressure, polarized IR absorption spectra and polarized absorbance
distributions of (001) and (110) oriented single crystal of brucite under high pressure were measured by Fourier transform
polarized infrared microspectroscopy with diamond anvil cell. A pressure-induced absorption peak at 3645 cm−1 observed under pressures over 2.9 GPa was confirmed to be due to a secondarily formed OH dipole. Polarized absorbance distribution
measured under pressure of (110) suggests that the secondary OH dipole is oriented 136.0° to c-axis under 5.3 GPa. Isotropic
absorbance distribution of (001) suggests that the secondary OH dipole is disorderly trifurcated. Abrupt onset of the secondary
peak and its reverse pleochroism suggest that the process of secondary OH dipole formation is due to proton transfer between
layers in brucite. The calculated orientation of the secondary OH dipole consistent with the O-H···O′ angle revealed by neutron
diffraction supports the existence of proton transfer along H···O′. The secondary OH dipole implies a new site of proton in
brucite under pressure.
Received: 6 March 1997 / Revised, accepted: 9 June 1997 相似文献
8.
Nobuyuki Kinoshita 《Boundary-Layer Meteorology》2014,152(1):91-105
Near-surface air temperature is the most important variable in the climatic analysis of global warming. The air temperature near the surface is affected by the artificial surface (asphalt, concrete and buildings for example) surrounding the thermometer. However, there is no quantitative method for evaluating the observational environment. Therefore, a practical evaluation method with a scientific basis is required to aid observational network managers and data users. The magnitude of the artificial surface influence on the air temperature and its characteristics are investigated using numerical experiments with various road widths and wind speeds. The results show that the temperature increase in the lee of the road depends on the distance from the road, the road width, the wind speed and the thermal stratification and that the temperature increase can be estimated using an analytical footprint model. In order to estimate the largest value of the temperature increase, a function is developed from the footprint model; it depends on the normalized distance based on the road width, and thus can be calculated easily. A practical method using this function is proposed for the evaluation of the effect of the observational environment. 相似文献
9.
10.
Nobuyuki YagiMichael L. Clark Lee G. AndersonRagnar Arnason Rebecca Metzner 《Marine Policy》2012,36(1):241-245
ITQs have not yet been introduced by the Government of Japan. In coastal areas, fishery cooperative associations have traditionally played an important role in managing fisheries through self-imposed rules and peer-monitoring systems. Recently, however, the economic competitiveness of Japanese fisheries in the international market is being questioned. In this paper, a detailed examination of the pros and cons of the current system in Japan is compared to the current fishery management measures of Iceland and the United States, where attaining economically or biologically efficient outcomes may be prioritized in making fisheries management decisions. For many coastal fisheries in Japan, maintaining a management scheme in which stakeholders play an active role in determining fisheries measures seems more relevant if their priority is to maintain the stability of coastal communities and equity of stakeholders. Intensive dialog among stakeholders would be necessary to identify shared objectives of their fishery operations and to make decisions to establish specific steps toward the goal of increasing economic efficiency, environmental sustainability, or stability of communities and equity of stakeholders. 相似文献