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191.
Chushiro Hayashi Kiyoshi Nakazawa Hiroshi Mizuno 《Earth and Planetary Science Letters》1979,43(1):22-28
When the proto-Earth was growing by the accretion of planetesimals and its mass became greater than about 0.1 ME, where ME is the present Earth's mass, an appreciable amount of gas of the surrounding solar nebula was attracted towards the proto-Earth to form an optically thick, dense atmosphere. We have studied the structure of this primordial atmosphere under the assumptions that (1) it is spherically symmetric and in hydrostatic equilibrium, and (2) the net energy outflow (i.e., the luminosity) is constant throughout the atmosphere and is given by GMM/R with M = M/106yr or M/107yr where M and R are the mass and the radius of the proto-Earth, respectively.The results of calculations show that the temperature at the bottom of the atmosphere, namely, at the surface of the proto-Earth increases greatly with the mass of the proto-Earth and it is about 1500°K for M = 0.25 ME. This high temperature is due to the blanketing effect of the opaque atmosphere. Thus, as long as the primordial solar nebula was existing, the surface temperature of the proto-Earth was kept high enough to melt most of the materials and, hence, the melted iron sedimented towards the center to form the Earth's core. 相似文献
192.
Power spectral density which describes frequency content is considered one of the most significant properties to be taken into account when generating ground motions through the use of stochastic processes. Using a smoothed and normalized Fourier amplitude spectrum, frequency content for components of motion along a set of principal axes is estimated. Fourier amplitude spectra obtained by this moving-window technique are presented which show the time dependency of frequency content for motions produced by the San Fernando earthquake of 9 February 1971. A mathematical model to simulate ground motion processes is proposed for which both the intensity and frequency content are non-stationary. Using this mathematical model with parameter characteristics along principal axes similar to those of the motions recorded during the San Fernando earthquake, three-dimensional ground motions are synthetically generated. The properties of the simulated motions show general characteristics similar to the characteristics observed in real accelerograms. The suggested model is considered adequate for engineering purposes. 相似文献
193.
Harunobu Masuko Kohei Arai Naoto Ebuchi Masanori Konda Masahisa Kubota Kunio Kutsuwada Teruko Manabe Akira Mukaida Tetsuo Nakazawa Atsushi Nomura Akira Shibata Yoshihiko Tahara 《Journal of Oceanography》2000,56(5):495-505
In order to validate wind vectors derived from the NASA Scatterometer (NSCAT), two NSCAT wind products of different spatial resolutions are compared with observations by buoys and research vessels in the seas around Japan. In general, the NSCAT winds agree well with the wind data from the buoys and vessels. It is shown that the root-mean-square (rms) difference between NSCAT-derived wind speeds and the buoy observations is 1.7 ms–1, which satisfies the mission requirement of accuracy, 2 ms–1. However, the rms difference of wind directions is slightly larger than the mission requirement, 20°. This result does not agree with those of previous studies on validation of the NSCAT-derived wind vectors using buoy observations, and is considered to be due to differences in the buoy observation systems. It is also shown that there are no significant systematic trends of the NSCAT wind speed and direction depending on the wind speed and incidence angle. Comparison with ship winds shows that the NSCAT wind speeds are lower than those observed by the research vessels by about 0.7 ms–1 and this bias is twice as large for data observed by moving ships than by stationary ships. This result suggests that the ship winds may be influenced by errors caused by ship's motion, such as pitching and rolling. 相似文献
194.
The Kurosegawa zone in southwest Japan is a 600 km long serpentinite mélange in the Chichibu terrains. It runs generally E-W but is slightly oblique to the subparallel arrangement of the Ryoke, Sanbagawa and Chichibu belts of Southwest Japan. A variety of geological units occurs in the Kurosegawa zone:
- 1. (1) granodiorite, gneiss and amphibolite of ca. 400 Ma,
- 2. (2) Siluro-Devonian formations,
- 3. (3) Upper Carboniferous to Jurassic formations,
- 4. (4) Upper Jurassic to Lower Cretaceous formations,
- 5. (5) serpentinite and
- 6. (6) low- to medium-grade metamorphic rocks of various baric types (ages, 220, 320, 360 and 420 Ma by K-Ar).
195.
Tetsuo Irifune Eiji Ohtani Mineo Kumazawa 《Physics of the Earth and Planetary Interiors》1982,27(4):263-272
The stability field of knorringite (Mg3Cr2Si3O12) is studied experimentally. Knorringite is stable at pressures above 10.5 GPa at 1200°C and 11.8 GPa at 1400°C. Below these pressures, knorringite decomposes to enstatite + eskolaite. A phase diagram of the pyrope-knorringite system is described based on the available experimental data. The solubility of the knorringite molecule in pyrope is essentially dependent only on pressure, and the Cr/Cr+Al value of garnet is considered to be an indicator of the minimum pressure of equilibration. Consideration of the genesis of Cr-rich pyrope and other peridotitic inclusions in diamonds indicates that the fractionation process should have taken place, at least at depths to ca. 240 km, to give rise to the Cr-rich complement of Cr-poor upper mantle materials such as undepleted lherzolite. The knorringite-rich peridotitic suite in diamond will be identified with this complement, which may be the material constituting the deep upper mantle. 相似文献
196.
Tetsuo Hasegawa Takaaki Arai Nobuyuki Yamaguchi Fumio Sato 《Astrophysics and Space Science》2008,313(1-3):91-94
We report mapping observations of a 35 pc × 35 pc region covering the Sgr B2 molecular cloud complex in the 13CO (3-2) and the CS (7-6) lines using the ASTE 10 m telescope with high angular resolution. The central region was mapped
also in the C18O (3-2) line. The images not only reproduce the characteristic structures noted in the preceding millimeter observations,
but also highlight the interface of the molecular clouds with a large velocity jump of a few tens of km s−1. These new results further support the scenario that a cloud–cloud collision has triggered the formation of massive cloud
cores, which form massive stars of Sgr B2. Prospects of exciting science enabled by ALMA are discussed in relation to these
observations. 相似文献
197.
Crustal structures around the Yamato Basin in the southeastern Sea of Japan, inferred from recent ocean bottom seismography (OBS) and active-source seismological studies, are reviewed to elucidate various stages of crustal modification involved from rifting in the crust of the surrounding continental arc to the production of oceanic crust in the Yamato Basin of the back-arc basin. The northern, central, and southern areas of the Yamato Basin have crustal thicknesses of approximately 12–16 km, and lowermost crusts with P-wave velocities greater than 7.2 km/s. Very few units have P-wave velocities in the range 5.4–6.0 km/s, which corresponds to the continental upper crust. These findings, combined with previous geochemical analysis of basalt samples, are interpreted to indicate that a thick oceanic crust has been formed in these areas of the basin, and that this oceanic crust has been underplated by mantle-derived magma. In the central Yamato Basin, the original continental crust has been fully breached and oceanic crust has been formed. Conversely, the presence of a unit corresponding to the continental upper crust and the absence of a high-velocity part in the lower crust implies that the southwestern edge of the Yamato Basin has a rifted crust without significant intrusion. The Oki Trough has a crust that is 17–19 km thick with a high-velocity lower crust and a unit corresponding to the continental upper crust. The formation of the Oki Trough resulted from rifting with magmatic intrusion and/or underplating. We interpret these variations in the crustal characteristics of the Yamato Basin area as reflecting various instances of crustal modification by thinning and magmatic intrusion due to back-arc extension, resulting in the production of a thick oceanic crust in the basin. 相似文献