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91.
92.
Christian Lehr Philipp Rauneker Marcus Fahle Tobias L. Hohenbrink Steven Böttcher Marco Natkhin Björn Thomas Ralf Dannowski Bernd Schwien Gunnar Lischeid 《水文研究》2017,31(3):750-752
Physical models are a well‐established tool in education to strengthen hydrological understanding. They facilitate the straightforward visualization of hydrological processes and allow the communication of hydrological concepts, research and questions of general interest to the public. In order to visualize the water cycle in a landscape of postglacial sediments, in particular the subsurface part, a physical model was constructed. In two videos, (1) a detailed construction manual and (2) visualization examples of hydrological concepts and processes are presented. With our contribution, we like to encourage professionals in the field of hydrology to share methods and tools of knowledge transfer and communication of hydrological concepts. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
93.
Victor L. Vinograd Julian D. Gale Björn Winkler 《Physics and Chemistry of Minerals》2007,34(10):713-725
Static lattice energy calculations (SLEC), based on empirical interatomic potentials, have been performed for a set of 800
different structures in a 2 × 2 × 4 supercell of C2/c diopside with compositions between diopside and jadeite, and with different states of order of the exchangeable Na/Ca and
Mg/Al cations. Excess static energies of these structures have been cluster expanded in a basis set of 37 pair-interaction
parameters. These parameters have been used to constrain Monte Carlo simulations of temperature-dependent properties in the
range of 273–2,023 K and to calculate a temperature–composition phase diagram. The simulations predict the order–disorder
transition in omphacite at 1,150 ± 20°C in good agreement with the experimental data of Carpenter (Mineral Petrol 78:433–440,
1981). The stronger ordering of Mg/Al within the M1 site than of Ca/Na in the M2 site is attributed to the shorter M1–M1 nearest-neighbor
distance, and, consequently, the stronger ordering force. The comparison of the simulated relationship between the order parameters
corresponding to M1 and M2 sites with the X-ray refinement data on natural omphacites (Boffa Ballaran et al. in Am Mineral
83:419–433, 1998) suggests that the cation ordering becomes kinetically ineffective at about 600°C. 相似文献
94.
During slightly unstable but still very close to neutral conditions new results from two previous investigations have shown
a significant increase of sensible and latent heat fluxes over the sea. The vertical heat transport during these conditions
is dominated by detached eddies originating at the top of the boundary layer, bringing relatively cold and dry air to the
surface. This effect can be described in numerical models by either enhanced heat transfer coefficients for sensible and latent
heat (Stanton and Dalton numbers respectively) or with an additional roughness length, added to the original roughness lengths
for heat and humidity. Such new expressions are developed using turbulence measurements from the Baltic Sea valid for wind
speeds up to 14 m s−1. The effect of including the increased heat fluxes is investigated using two different numerical models: a regional three-dimensional
climate model covering northern Europe, and a process-oriented ocean model for the Baltic Sea. During periods of several days,
the latent heat flux can be increased by as much as 100 W m−2. The increase in sensible heat flux is significantly smaller since the process is only of importance in the very near-neutral
regime where the sensible heat flux is very small. The long-term average effect over the Baltic Sea is of the order of several
W m−2. 相似文献
95.
Björn Bonnevier 《Astrophysics and Space Science》1981,79(2):509-513
In the big-bang hypothesis the metagalaxy (or Universe) is considered to have expanded from a state of extremely high density. The observations of distant galaxies are usually interpreted with this picture in mind. As pointed out by Alfvén it is important to see, if these observations do really require the hypothesis of an early extremely high density. It is found that with present available information, it is not possible to conclude that the density has been higher than implied by the Schwarzschild limit. 相似文献
96.
635 samples of suspended particulate matter (SPM), collected in the St. Lawrence river and estuary during periods of high and low river flow from a series of individual and anchor stations on a transect traversing the turbidity maximum zone, as well as two sediment box cores, were analyzed for Al, Si, Ca, Mg, Fe and Mn.An abrupt change in elemental composition occurs when traversing the front at the landward edge of the turbidity maximum. As the SPM concentration increases across the front from 20–200 mg l?1, the Ca/Al and Mg/Al ratios of the SPM increase and the Si/Al, Fe/Al and Mn/Al ratios decrease. The almost 50% decrease of the Mn/Al ratio is not related to changes in salinity. Within the turbidity maximum the tidal-averaged Si/Al, Ca/Al, Mg/Al and Fe/Al ratios of the SPM do not differ significantly from the landward to the seaward end of the turbidity zone, but on one tidal station the ratios of Si, Ca and Fe to Al are significantly lower at high river flow than at low flow. The Mn/Al ratio is insensitive to the extreme variations of either salinity (0.6–30‰) or SPM concentrations (10–480 mg l?1) within the turbidity zone. A tendency for higher Mn/Al ratios to be associated with near-bottom SPM, observed in the center of the turbidity zone during the low river flow period, is well developed in the lower reaches of the zone.Diagenetic mobilization within the rare fine-grained bottom sediments of the turbidity maximum is responsible for changes in Mn and Fe content of particulate matter, and early settling of coarse-grained components and size sorting within the zone are responsible for other compositional changes. Local sources, desorption and precipitation are apparently of secondary importance. The depletion of both Mn and Fe in the SPM and sediment of the upper estuary implies a net seaward escape of diagenetically mobilized metal. 相似文献
97.
98.
Spatial and temporal variation in particle size and particulate organic matter content in suspended particulate matter from peatland‐dominated catchments in Finland 下载免费PDF全文
Properties of suspended particulate matter play a vital role in transport processes, but information from boreal lowland river systems with high organic loads is limited. This study analysed data from 2 years of sampling at 30 locations in Finland (204 samples in total) using suspended particulate matter samplers to determine effective and absolute particle size and organic fractions. Mean d50 value was 22 and 49 µm for absolute and effective particle size, respectively. The organic fraction content ranged from 2.1% to 36% (mean 9.6%), highlighting the importance of particle organic matter for suspended particulate matter flux in the region. The results indicated that the suspended particulate matter particle size distribution and load in the study region is dominated by composite particles. There were considerable spatial and temporal variations in transport of organic fractions, effective particle size and degree of aggregation (range 1.5–93%). Headwaters and, in particular, late summer and spring flood conditions with flow peaks produced the largest composite particles, whereas agriculture‐dominated sites produced smaller but more tightly compacted particles. Organic plant fibres appeared to play a vital role in floc formation in peat‐covered catchments, whereas in agriculture‐dominated catchments, land use‐derived aggregates dominated the composition. This study provides empirical evidence of the importance of effective particle size measurement in understanding the dynamics of suspended particulate matters in boreal lowland river systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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100.