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111.
Sheila J. Seaman Helle Gylling John P. Hogan Frank Karner G. Christopher Koteas 《Contributions to Mineralogy and Petrology》2011,162(6):1291-1314
The Tunk Lake pluton of coastal Maine, USA is a concentrically zoned granitic body that grades from an outer hypersolvus granite
into subsolvus rapakivi granite, and then into subsolvus non-rapakivi granite, with gradational contacts between these zones.
The pluton is partially surrounded by a zone of basaltic and gabbroic enclaves, interpreted as quenched magmatic droplets
and mushes, respectively, as well as gabbroic xenoliths, all hosted by high-silica granite. The granite is zoned in terms
of mineral assemblage, mineral composition, zircon crystallization temperature, and major and trace element concentration,
from the present-day rim (interpreted as being closer to the base of the chamber) to the core (interpreted as being closer
to the upper portions of the chamber). The ferromagnesian mineral assemblage systematically changes from augite and hornblende
with augite cores in the outermost hypersolvus granite to hornblende, to hornblende and biotite, and finally, to biotite only
in the subsolvus granite core of the pluton. Sparse fine-grained basaltic enclaves that are most common in the outermost zone
of the pluton suggest that basaltic magma was present in the lower portions of the magma chamber at the same time that the
upper portions of the magma chamber were occupied by a granitic crystal mush. However, the slight variations in initial Nd
isotopic ratio in granites from different zones of the pluton suggest that contamination of the granitic melt by basaltic
melt played little role in generating the compositional gradation of the pluton. The zone of basaltic and gabbroic chilled
magmatic enclaves, and gabbroic xenoliths, hosted by high-silica granite, that partially surround the pluton is interpreted
as mafic layers at the base of the pluton that were disrupted by invading late-stage high-silica magma. These mafic layers
are likely to have consisted of basaltic lava layers and basalt that chilled against granitic magma to produce coarse-grained
gabbroic mush. Basaltic and gabbroic magmatic enclaves and gabbroic xenoliths are hornblende-bearing, suggesting that their
parent melts were relatively hydrous. The water-rich nature of the underplating mafic magmas may have prevented extensive
invasion of the granitic magma by these magmas, owing to the much greater viscosity of the granitic magma than the mafic magmas
in the temperature range over which magma interaction could have occurred. 相似文献
112.
The escape of trajectories of a spacecraft, or comet or asteroid in the presence of the Earth–Moon system is investigated in detail in the context of the planar circular restricted three-body problem, in a scattering region around the Moon. The escape through the necks around the collinear points \(L_1\) and \(L_2\) as well as the leaking produced by considering collisions with the Moon surface, taking the lunar mean radius into account, were considered. Given that different transport channels are available as a function of the Jacobi constant, four distinct escape regimes are analyzed. Besides the calculation of exit basins and of the spatial distribution of escape time, the qualitative dynamical investigation through Poincaré sections is performed in order to elucidate the escape process. Our analyses reveal the dependence of the properties of the considered escape basins with the energy, with a remarkable presence of fractal basin boundaries along all the escape regimes. Finally, we observe the plentiful presence of stickiness motion near stability islands which plays a remarkable role in the longest escape time behavior. The application of this analysis is important both in space mission design and study of natural systems, given that fractal boundaries are related with high sensitivity to initial conditions, implying in uncertainty between safe and unsafe solutions, as well as between escaping solutions that evolve to different phase space regions. 相似文献
113.
K.P. Stewart B.C. Hicks P.S. Ray P.C. Crane N.E. Kassim R.F. Bradley W.C. Erickson 《Planetary and Space Science》2004,52(15):1351-1355
We are developing and testing active baluns and electrically short dipoles for possible use as the primary wide band receiving elements in the low-frequency array (LOFAR) for long wavelength radio astronomy. Several dipoles of various designs and dimensions have been built and tested. Their useful range occurs when the dipole arms are approximately to one wavelength long and the feedpoint is less than wavelength above ground. An eight-element NRL LOFAR test array (NLTA) interferometer has been built and fringes have been observed from the brightest celestial sources in the frequency range from 10 to 50 MHz. The antenna temperatures vary from about 10% to 100% of the average brightness temperature of the galactic background. With these parameters it is easy to make the amplifier noise levels low enough that final system temperature is dominated by the galactic background. 相似文献
114.
S. Le Pape M. Koenig T. Vinci E. Martinolli D. Hicks A. Mackinnon P. Patel M. Borghesi L. Romagnani T. Boehly 《Astrophysics and Space Science》2005,298(1-2):313-316
We performed an experiment using high-energy protons to characterize in situ the spatial and temporal evolution of a laser-driven shock propagating through a low-Z material. Radiography of the shock
propagating through the low-Z transparent material (Lexan, quartz, diamond) enabled estimation of density under compression.
In order to discriminate the influence of the shocked matter on the protons trajectory, a Monte-Carlo simulation was developed.
This code describes the protons trajectory through the matter, calculating the scattering angle and the loss of energy. 相似文献
115.
M. A. Hicks 《国际地质力学数值与分析法杂志》1995,19(1):1-27
The principal features involved in the implementation of the double-hardening constitutive law Monot1 into a general purpose computer algorithm called MONICA2,3 are described. These include details of general program structure and of steps taken to overcome problems such as computer storage, computer run-time, algorithm stability and problems associated with the stress–strain singularity which exists at the intersection of the two yield surfaces. 相似文献
116.
Hazard analysis of seismic submarine slope instability 总被引:1,自引:0,他引:1
Rafael Rodríguez-Ochoa Farrokh Nadim José M. Cepeda Michael A. Hicks Zhongqiang Liu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(3):128-147
To assess the risk associated with a submarine landslide, one must estimate the probability of slope failure and its consequences. This paper proposes a procedure to estimate the probability of earthquake-induced submarine slope failure (hazard) based on probabilistic seismic hazard analyses, ground response analyses and advanced laboratory tests. The outcomes from these analyses are treated in a probabilistic framework, with analytical simulations using mathematical techniques such as the first-order reliability method, Monte Carlo simulation and Bayesian updating. Fragility curves of slope failure during the earthquake (co-seismic) and after the earthquake (post-seismic) were developed in this study, and were shown to provide a clear and well-organized procedure to estimate the annual failure probability of a submarine slope under earthquake loading. 相似文献
117.
Brent B. Wolfe Tammy L. Karst‐Riddoch Roland I. Hall Thomas W. D. Edwards Michael C. English Roger Palmini Suzanne McGowan Peter R. Leavitt Sheila R. Vardy 《水文研究》2007,21(2):151-168
We used stable isotopes (δ18O and δ2H) and water chemistry to characterize the water balance and hydrolimnological relationships of 57 shallow aquatic basins in the Peace‐Athabasca Delta (PAD), northern Alberta, Canada, based on sampling at the end of the 2000 thaw season. Evaporation‐to‐inflow ratios (E/I) were estimated using an isotope mass‐balance model tailored to accommodate basin‐specific input water compositions, which provided an effective, first‐order, quantitative framework for identifying water balances and associated limnological characteristics spanning three main, previously identified drainage types. Open‐drainage basins (E/I < 0·4; n = 5), characterized by low alkalinity, low concentrations of nitrogen, dissolved organic carbon (DOC) and ions, and high minerogenic turbidity, include large, shallow basins that dominate the interior of the PAD and experience frequent or continuous river channel connection. Closed‐drainage basins (E/I ≥ 1·0; n = 16), in contrast, possess high alkalinity and high concentrations of nitrogen, DOC, and ions, and low minerogenic turbidity, and are located primarily in the relict and infrequently flooded landscape of the northern Peace sector of the delta. Several basins fall into the restricted‐drainage category (0·4 # E/I < 1·0; n = 26) with intermediate water chemistries and are predominant in the southern Athabasca sector, which is subject to active fluviodeltaic processes, including intermittent flooding from riverbank overflow. Integration of isotopic and limnological data also revealed evidence for a new fourth drainage type, mainly located near the large open‐drainage lakes that occupy the central portion of the delta but within the Athabasca sector (n = 10). These basins were very shallow (<50 cm deep) at the time of sampling and isotopically depleted, corresponding to E/I characteristic of restricted‐ and open‐drainage conditions. However, they are limnologically similar to closed‐drainage basins except for higher conductivity and higher concentrations of Ca2+ and Na+, and lower concentrations of SiO2 and chlorophyll c. These distinct features are due to the overriding influence of recent summer rainfall on the basin water balance and chemistry. The close relationships evident between water balances and limnological conditions suggest that past and future changes in hydrology are likely to be coupled with marked alterations in water chemistry and, hence, the ecology of aquatic environments in the PAD. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
118.
Sheila M. Palmer Brian I. Wellington Chris E. Johnson Charles T. Driscoll 《水文研究》2005,19(9):1751-1769
Concentrations of both aluminium (Al) and dissolved organic carbon (DOC) in stream waters are likely to be regulated by factors that influence water flowpaths and residence times, and by the nature of the soil horizons through which waters flow. In order to investigate landscape‐scale spatial patterns in streamwater Al and DOC, we sampled seven streams draining the Hubbard Brook valley in central New Hampshire. We observed considerable variation in stream chemistry both within and between headwater watersheds. Across the valley, concentrations of total monomeric aluminium (Alm) ranged from below detection limits (<0·7 µmol l−1) to 22·3 µmol l−1. In general, concentrations of Alm decreased as pH increased downslope. There was a strong relationship between organic monomeric aluminium (Alo) and DOC concentrations (R2 = 0·92). We observed the highest Alm concentrations in: (i) a watershed characterized by a steep narrow drainage basin and shallow soils and (ii) a watershed characterized by exceptionally deep forest floor soils and high concentrations of DOC. Forest floor depth and drainage area together explained much of the variation in ln Alm (R2 = 0·79; N = 45) and ln DOC (R2 = 0·87; N = 45). Linear regression models were moderately successful in predicting ln Alm and ln DOC in streams that were not included in model building. However, when back‐transformed, predicted DOC concentrations were as much as 72% adrift from observed DOC concentrations and Alm concentrations were up to 51% off. This geographic approach to modelling Al and DOC is useful for general prediction, but for more detailed predictions, process‐level biogeochemical models are required. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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