全文获取类型
收费全文 | 223篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 11篇 |
地球物理 | 42篇 |
地质学 | 116篇 |
海洋学 | 2篇 |
天文学 | 37篇 |
自然地理 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 20篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 11篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有231条查询结果,搜索用时 15 毫秒
161.
Cosmic ray interactions with lunar materials: Nature and composition of species formed 总被引:1,自引:0,他引:1
Nalin R. Mukherjee 《Earth, Moon, and Planets》1976,16(1):151-158
The solar and galactic cosmic rays interact directly with lunar surface materials, and the dominant nature of interactions is essentially the complete absorption of corpuscles. These corpuscles damage the lattice structure, and induce a complex set of reactions in the materials producing various species. The cosmic ray damage of the lattice would not produce an amorphous layer, similar to that produced by the solar wind, because the solar wind erosion rate is faster than the cosmic ray-induced amorphous layer formation rate. The species formation rate considered in this paper are those produced by protons, the dominant component of cosmic rays. Protons produce H, H2, OH, H2O, and hydrogenated species of carbon, nitrogen, sulfur, etc. These species, while migrating in the material, encounter oncoming cosmic ray corpuscles, and undergo a complex set of reactions. Although a variety of species are produced by protons, the dominant contributor to the atmosphere is H2. The H2 flux (molecules cm–2 sec–1) is about 1.5 × 105 as compared to the H flux of 8.4 × 101 and the H2O flux of 4.6 × 10–2. These fluxes are about 10–3 smaller than the fluxes of the same species produced by the solar wind protons. Thus the contributions of the cosmic ray-induced species to the atmosphere is very small compared to the solar wind-induced species. Although simulated experiments showed high concentractions of OH and H2O in the terrestrial materials of lunar type, these species concentrations in the lunar materials under the lunar environment is much smaller than those observed in the simulated experiments. 相似文献
162.
A new approach for dimensionality reduction of hyperspectral data has been proposed in this article. The method is based on extraction of fractal-based features from the hyperspectral data. The features have been generated using spectral fractal dimension of the spectral response curves (SRCs) after smoothing, interpolating and segmenting the curves. The new features so generated have then been used to classify hyperspectral data. Comparing the post classification accuracies with some other conventional dimensionality reduction methods, it has been found that the proposed method, with less computational complexity than the conventional methods, is able to provide classification accuracy statistically equivalent to those from conventional methods. 相似文献
163.
164.
Soumyajit Mukherjee Kieran F. Mulchrone 《International Journal of Earth Sciences》2012,101(7):1929-1947
The Tso Morari crystalline (TMC) gneiss dome in the Indian Himalaya extruded from a depth of?~120?km through an inclined subduction channel of sub-elliptical cross-section at the leading edge of the Indian plate. The velocity profile of this gneiss dome is derived after (1) presuming its incompressible Newtonian rheology, (2) finding the “best fit” of the outcrop of the gneiss dome to an ellipse, (3) taking into account different lithologies to have existed at the top of the extruding gneiss body, (4) considering the extrusion to have been driven by the buoyant push of the denser mantle beneath the lighter gneiss, and (5) assigning a range of plausible densities for different litho-units. Fitting the known rates of extrusion—from a few centimetres up to about one-hundredth of a millimetre per year—from?~53?Ma onwards of this gneiss dome to its velocity profile constrains its maximum possible viscosity to?~7.5?×?1022 Pa?s. This magnitude is?102–104 times higher than previous estimates for gneisses and granites. Alternative explanations of our data are the following: (1) There was a fall in extrusion rates of the TMC gneiss from 53?to?<30?Ma because of an increase in the estimated maximum viscosity from 6.2?×?1020 to 7.5?×?1022 Pa?s, possibly indicating a fall in temperature and/or compositional change of the TMC gneiss. (2) Lower the extrusion rates, higher are the estimated viscosities. (3) The TMC gneiss was more viscous probably due to its eclogite content. (4) The estimated maximum viscosity is?~102 times higher than that in collision zones and?102–104 times than that in the Tibetan lower crust, but broadly conforms to that for the crustal channel, and average lithospheric and asthenospheric values. The high magnitude of maximum possible Prandtl number of?~1028 of the TMC gneiss might be related to isothermal decompression of the gneiss during its extrusion. 相似文献
165.
Nalin R. Mukherjee 《Earth, Moon, and Planets》1979,21(3):307-317
The solar-wind interacts directly with the lunar surface due to tenuous atmosphere and magnetic field. The interaction results in an almost complete absorption of the solar-wind corpuscles producing no upstream bowshock but a cavity downstream. The solar-wind oxygen ionic species induce and undergo a complex set of reactions with the elements of the lunar minerals and the solar-wind derived trapped gases. The oxygen concentration indegeneous to the lunar surface material is about 60 at.%. Some of these oxygen are displaced from their crystal lattice locations by interactions of the solar-wind corpuscles. A small fraction of these displaced oxygen is in active state. The solar-wind oxygen species flux is about 6×104 cm–2 s–1. Besides inducing and undergoing various reactions these species become trapped as oxygen atoms in the lunar grains. Only a portion of these trapped oxygen atoms is in active state. For the contribution of oxygen atoms and molecules from the lunar surface grains to the atmosphere and their reactions with other species, the diffusion coefficients of oxygen atom and molecule should be known. However their values in the highly radiation-damaged lunar surface material are not known. The coefficients are calculated by using the apparent lifetimes of atomic and molecular oxygen in the lunar material. The atmospheric concentration of oxygen atoms and molecules near the lunar surface are found to be about 20 and 3 cm–3, respectively. These values appear to be very reasonable in comparison with the experimental data. The Apollo 17 lunar orbital UV spectrometer data indicate the atomic oxygen concentration is <8×101 cm–3. The Apollo 17 lunar surface mass spectrometer (sensitivity: 1 count=2×102 molecules cm–3) did not detect any oxygen molecules on the dayside of the Moon, but the sunrise concentration was reported to be 1±×103 cm–3. At the time of the sample collection on the Moon the oxygen content in the trapped gas layer was partly as oxygen atoms and partly as oxygen molecules. At the time of sample analysis on the Earth the concentrations of these two species did not change appreciably. 相似文献
166.
Nalin R. Mukherjee 《Earth, Moon, and Planets》1981,25(4):451-463
The lunar atmosphere and magnetic field are very tenuous. The solar wind, therefore, interacts directly with the lunar surface material and the dominant nature of interaction is essentially complete absorption of solar-wind particles by the surface material resulting in no upstream bowshock, but a cavity downstream. The solar-wind nitrogen ion species induce and undergo a complex set of reactions with the elements of lunar material and the solar-wind-derived trapped elements. The nitrogen concentration indigeneous to the lunar surface material is practically nil. Therefore any nitrogen and nitrogen compounds found in the lunar surface material are due to the solar-wind implantation of nitrogen ions. The flux of the solar-wind nitrogen ion species is about 6×103 cm–2 s–1. Since there is no evidence for accumulation of nitrogen species in the lunar surface material, the outflux of nitrogen species from the lunar material to the atmosphere is the same as the solar-wind nitrogen ion flux. The species of the outflux are primarily NO and NH3, and their respective concentrations in the near surface lunar atmosphere are found by calculation to be 327 and 295 cm–3. The calculated concentration of NH3 seems to be consistent with the sunrise concentration results of the mass spectrometer implanted on the lunar surface. This is not the case for the concentration of NO. According to the presently calculated concentration value of NO, the mass spectrometer should have detected NO at sunrise, but no report was made for its detection. There is also discrepancy about the concentration of N2 which is explained in this paper. The concentrations of nitrogen species in the lunar material at the time of sample collection on the Moon remained about the same when the samples were analyzed on the Earth. However, no specific experiment was planned to detect the nitrogen species in the lunar material samples. 相似文献
167.
Saibal Gupta Jagatbikas Nanda Sumit Kumar Mukherjee Manasij Santra 《Gondwana Research》2005,8(3):403-419
Linear domains of deformed alkaline rocks and carbonatites have recently been identified as representing sites of ancient suture zones. In peninsular India, the western margin of the Proterozoic Eastern Ghats Belt (EGB) is characterized by a series of alkaline plutons that are aligned close to the contact with the Archaean Craton. Most of the complexes were deformed and metamorphosed during a subsequent orogenic event. Unlike other plutons in the belt, the alkaline complex at Koraput reportedly escaped deformation and granulite facies metamorphism forming an anomalous entity within the zone. Multiply-deformed country rocks hosting this complex underwent syn-D1CR granulite facies metamorphism followed by D2CR thrusting, with pervasive shearing along a NE-SW trending foliation. A second granulite facies event followed localized D3CR shearing. Within the Koraput Complex, strain partitioning was responsible for preserving igneous textures in the gabbroic core, but aligned magmatic amphibole needles and plagioclase laths occasionally define a S1AC fabric. Along the margins, S1AC is rotated parallel to a NE-trending, east-dipping S2AC fabric in the gabbro, fringing syenodiorite and nepheline syenite bands. Locally, D3AC shearing follows D2AC deformation; S2AC and S3AC parallel S2CR and S3CR in the country rocks. High-grade metamorphism represented by recrystallization of amphibole and plagioclase, and breakdown of amphibole and biotite to garnet, pyroxene and K-feldspar in the complex follows D3AC. Unlike earlier reports, therefore, the Koraput body is also deformed and metamorphosed. The aligned alkaline complexes in the EGB probably represent deformed alkaline rocks and carbonatites formed by rifting related to an earlier episode of continental break-up that were deformed during subsequent juxtaposition of the EGB with the Archaean Craton. This supports the contention that the western margin of the EGB and its contact with the Archaean Craton is a suture zone related to the Indo-Antarctica collision event. 相似文献
168.
169.
G. K. Mukherjee 《Pure and Applied Geophysics》1987,125(5):845-852
The average latitude of theSq(X) focus along the longitude 75°E has been estimated using the Tsyganenko model (Tsyganenko, 1981) of the external magnetic field for storm time conditions of the magnetosphere. It is observed that the shift of the focal latitudes, due to magnetospheric currents, is only about 1 to 2° even during strong storms. It is also shown that the shift is asymmetric about the equator and longitude dependent. The day to day changes in observed focal position are much larger and the magnetospheric currents cannot, therefore, be regarded as a dominant mechanism of focal movement.The paper was presented at the IAGA General Assembly meeting held in Prague, Czechoslovakia, during August 1985. 相似文献
170.
The Yamato diogenite, Y-74013, shows a high degree of textural equilibrium with the apparent crystallization sequence: troilite and metal → orthopyroxene → plagioclase. The position of the large chromite crystals in this sequence is unclear. Except chromite, all other minerals have composition similar to common orthopyroxene achondrites. The chromite is more magnesian than in common diogenites, strongly zoned and, on the whole, intermediate in composition between chromites of diogenites and pallasites. Texture, mineral composition data and an equilibrium thermodynamic analysis of the mineral association strongly indicate that the chromite crystallized earlier than the silicates at a much higher temperature (possibly above 1100°C) and rapidly grew in a medium which was progressively enriched in Mg, Al and Ti. But the chromite failed to reach chemical equilibrium, even at its outermost rim, with the orthopyroxene. The calculated equilibrium log fO2 of the Yamato diogenite, ?20·21 to ?11·08 for temperatures between 880°C and 1500°C is well within the normal oxygen fugacity range of pyroxene achondrites. 相似文献