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81.
William J. Kimmerer James H. Cowan Lee W. Miller Kenneth A. Rose 《Estuaries and Coasts》2001,24(4):557-575
Estuarine fish populations are exposed to a variety of environmental conditions that cause both short-term variability and
long-term trends in abundance. We analyzed an extensive data set for striped bass (Morone saxatilis) in the San Francisco Estuary to refine our understanding of how environmental variability influences recruitment. We examined
the effects of environmental variability during early life stages on subsequent recruitment (age 3 yr), and the degree to
which conditions in early life may have contributed to a long-term decline in abundance of adult striped bass in the San Francisco
Estuary. Survival from egg to young-of-the-year varied strongly with freshwater flow; this effect apparently occurred within
the first week or two of life, a time period that encompasses transport of eggs and larvae from the rivers to rearing areas
and the onset of feeding. The rate of freshwater flow to pumping facilities that export freshwater from the system had small
or sporadic effects on survival during the first month or two of life. Although many young striped bass between ages 2 and
8 mo were entrained in export pumping facilities, the resulting high mortality was unrelated to total mortality rates determined
from field data on young striped bass. This lack of effect was apparently due to strong density-dependent mortality occurring
between ages 1 mo and 3 yr (Kimmerer et al. 2000). The available data do not support previously suggested relationships between
recruitment and freshwater flow during early life, or between gross estimates of pesticide input and survival of early life
stages. We used a simple life-cycle model to show that various combined factors could have led to a decline in adult abundance,
particularly a large and increasing adult mortality, but that events early in life probably did not contribute substantially
to the decline. These results demonstrate that several decades of monitoring data from numerous life stages are needed to
distinguish among alternative hypotheses about environmental influences on populations of estuarine fish. 相似文献
82.
Steven Pawson Ulrike Langematz Arnold Meyer Peter Strauch Silke Leder Klaus Rose 《Climate Dynamics》1991,5(3):161-174
Mean fields from a perpetual January simulation of a GCM extending from the surface to 0.01 hPa (near 80 km) are compared to observations. The zonal mean temperature and wind fields correspond quite well with reality; the low stratosphere, especially in the polar night, is too cold, but warmer than in the original version of the model, with an upper boundary at 25 hPa. Mean fields at standard levels show that the major features of the troposphere are represented by the model, but rather over emphasised; the stratospheric winter polar vortex is too strong, too cold, and too barotropic; it resembles an `undisturbed' January rather than the climatology. Differences in the stationary eddy activity between the extended and orginal versions of the model are noted, and used to explain some differences between the two simulations.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute für Meteorology. Guest Editor for these papers is Dr. L. Dümenil 相似文献
83.
Stratigraphy of the Toba Tuffs and the evolution of the Toba Caldera Complex,Sumatra, Indonesia 总被引:3,自引:0,他引:3
During the past 1.2 m.y., a magma chamber of batholithic proportions has developed under the 100 by 30 km Toba Caldera Complex. Four separate eruptions have occurred from vents within the present collapse structure, which formed from eruption of the 2800 km3 Youngest Toba Tuff (YTT) at 74 ka. Eruption of the three older Toba Tuffs alternated from calderas situated in northern and southern portions of the present caldera. The northern caldera apparently developed upon a large andesitic stratovolcano. The calderas associated with the three older tuffs are obscured by caldera collapse and resurgence resulting from eruption of the YTT. Samosir Island and the Uluan Block are two sides of a single resurgent dome that has resurged since eruption of the YTT. Samosir Island is composed of thick YTT caldera fill, whereas the Uluan Block consists mainly of the Oldest Toba Tuff (OTT). In the past 74000 years lava domes have been extruded on Samosir Island and along the caldera's western ring fracture. This part of the ring fracture is the site of the only current activity at Toba: updoming and fumarolic activity. The Toba eruptions document the growth of the laterally continuous magma body which eventually erupted the YTT. Repose periods between the four Toba Tuffs range between 0.34 and 0.43 m.y. and give insights into pluton emplacement and magmatic evolution at Toba. 相似文献
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The ongoing encroachment of urban land into natural landscapes has resulted in the degradation of ecosystems throughout Europe. Understanding why the share of urban land has increased is important for managing urban growth and maintaining ecosystem services. We estimate a model of landscape change that integrates geospatial and socioeconomic data in a spatial autoregressive model to explain the variance in urban growth observed in Germany between 2000 and 2006. In doing so, we test several determinants of urbanization identified by theoretical frameworks from landscape ecology and economics, including landscape pattern and transit infrastructure. The results show that despite planning guidelines and policies to promote dense development, urban growth has been extensive. Regions with a high degree of fragmented land and the prevalence of environmental amenities are characterized by particularly strong growth, pointing to challenges in crafting landscape policies that balance economic development with environmental conservation. 相似文献
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