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141.
This paper summarizes the governing equations as implemented in the MIN3P multicomponent flow and reactive transport code (Mayer et al., Water Resour Res 38:1174, 2002) and introduces the equations in discretized form. Linearization and solution methods are presented including adaptive time stepping and update modification schemes. Code-specific details for the implementation of the GdR MoMaS benchmark simulations (Carrayrou et al., Comput Geosci, 2009) are presented. The standard version of the MIN3P code was used to solve the Easy, Medium, and Hard Test Cases, in one and two spatial dimensions, for both advection- and diffusion-dominated conditions. An analysis of the sensitivity of the solution in relation to spatial and temporal discretization parameters is provided for the Easy Test Case, selected results are presented for the Medium and Hard Test Cases, and the performance of the code as a function of discretization parameters is evaluated for all test cases. 相似文献
142.
Ulrich Wieczorek 《International Journal of Earth Sciences》2010,99(1):201-205
The deviation of the insolation on the earth’s surface from the past to the present and the present to the future for cloudless
days is calculated in intervals of 1,000 years from 100000 years before present (BP) to 100000 years after present (AP), its
basis being Milankovic’s theory. But the result are not the well-known Milankovic-curves, which are calculated for different
latitudes and in which the x-axis represents years and the y-axis represents the insolation difference to present during the North-summer half-year. The calculations are made for each
day of the selected years from the South Pole to the North Pole. Thus, two temporal dimensions are represented, that of a
year and that of a day, furthermore the spatial dimension “latitude” and the dimension “energy” (insolation deviation). The
performance of modern PCs allows the results of the calculations to be presented by a graphical animation. A determined deviation
pattern of the insolation is obtained for each year. δ18O data, the mean global temperature and the additional ice volume on the continents are added to the graphic representations
of those patterns for the period from 100000 years BP to the present. During that period insolation deviation patterns can
be recognised which correlate with cool climates or climates getting cooler, and others which correlate with relatively warm
climates or climates getting warmer. Correlations between the patterns are calculated and groups of similar patterns can be
composed which can be associated in most cases with specific climatic conditions or specific climatic change. Comparison of
patterns between 100000 years and present BP with patterns between present and 100000 years AP can help to estimate climatic
change during the 100000 years ahead. 相似文献
143.
A new method to reconstruct aquatic palaeoenvironments is presented. It is based on a non-metrical ‘fish environment reconstruction
index’ (FERI), calculated for the total fish community recorded at an archaeological site. As an example, a FERI is generated
for the Baltic Sea using the ecological requirements of northern European fish species. The present study evaluates the proposed
method by using fish bone assemblages from a region (the middle Holocene Baltic Sea coast) with well-studied hydrographic
history. The bones originate from consecutive human riparian and coastal settlements of hunter-gatherers. The results obtained
for the parameters salinity and sediment structure correlate well with geological knowledge. The new method shows a successive
change from freshwater to brackish and finally to nearly marine conditions before, during, and towards the end of the marine
transgression that created the present Baltic Sea. Additionally, a shift in the sediment structure from muddy to sandy/rocky
conditions is recognisable. 相似文献
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148.
As evidenced by catastrophic cadmium and mercury poisonings in japan, heavy metals belong to the most toxic environmental pollutants. Through the investigation of sediments, the extent, distribution and provenance of heavy metal contamination in rivers and lakes can be determined and traced. Eight heavy metals from the clay fraction of sediments from major rivers within the Federal Republic of Germany were determined by means of atomic adsorption spectrometry. Heavy metals especially known for their high toxicity are enriched most: mercury, lead and zinc by a factor of 10; cadmium by a factor of 50, as compared with the natural background of these elements. A mobilisation of heavy metals from the suspended load and from the sediments, as to be observed in rivers approaching the marine enviromment, could endanger marine organisms, thus negatively influencing the acquatic food chain. With a further increase of heavy metal pollution, a threat to the drinking water supplied by rivers and lakes cannot be excluded. 相似文献
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150.
The structural phase transition in titanite is correlated with a strong temperature dependence of Raman scattering cross sections and, to a somewhat lesser extent, with shifts of the phonon frequencies. Their quantitative temperature evolution in the low-symmetry phase (P21/a) is compatible with a nearly 2D Ising behaviour with β≈0.12 and T c = 497 K. At temperatures above 860 K, the phonon signals agree with A 2/a symmetry but not in the temperature interval between 497 K and 860 K. In this temperature range new structural states give rise to additional phonon signals. A model based on mobile APBs between slabs of P21/a material, first proposed by van Heurck et al. (1991), is in qualitative agreement with our experimental observations. 相似文献