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201.
202.
Margaret Armstrong 《Mathematical Geology》1981,13(4):321-329
The washability characteristics of coal are dependent on two basic relations: the ash assay vs. relative density curve, and the distribution by weight of the relative densities of coal particles. Armstrong and Whitmore (1980) demonstrated that the ash content and the yield of coal floating at a particular density can be predicted with reasonable accuracy using a simple inverse proportionality relation for the ash assay vs. density curve and a lognormal model for the distribution. In this paper, geostatistical techniques are used in conjunction with the two models to predict the washability characteristics of coal in situ. 相似文献
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Andrea Donnellan John Rundle Geoffrey Fox Dennis McLeod Lisa Grant Terry Tullis Marlon Pierce Jay Parker Greg Lyzenga Robert Granat Margaret Glasscoe 《Pure and Applied Geophysics》2006,163(11-12):2263-2279
We are developing simulation and analysis tools in order to develop a solid Earth Science framework for understanding and studying active tectonic and earthquake processes. The goal of QuakeSim and its extension, the Solid Earth Research Virtual Observatory (SERVO), is to study the physics of earthquakes using state-of-the-art modeling, data manipulation, and pattern recognition technologies. We are developing clearly defined accessible data formats and code protocols as inputs to simulations, which are adapted to high-performance computers. The solid Earth system is extremely complex and nonlinear, resulting in computationally intensive problems with millions of unknowns. With these tools it will be possible to construct the more complex models and simulations necessary to develop hazard assessment systems critical for reducing future losses from major earthquakes. We are using Web (Grid) service technology to demonstrate the assimilation of multiple distributed data sources (a typical data grid problem) into a major parallel high-performance computing earthquake forecasting code. Such a linkage of Geoinformatics with Geocomplexity demonstrates the value of the Solid Earth Research Virtual Observatory (SERVO) Grid concept, and advances Grid technology by building the first real-time large-scale data assimilation grid. 相似文献
206.
Joel S. Steward Robert W. Virnstein Margaret A. Lasi Lori J. Morris Janice D. Miller Lauren M. Hall Wendy A. Tweedale 《Estuaries and Coasts》2006,29(6):954-965
Between August 14 and September 26, 2004, four tropical weather systems (Charley, Frances, Ivan, and Jeanne) affected the
central Indian River Lagoon (IRL). The central IRL received a prodigious amount of rainfall for the 2 mo, between 72 and 83
cm, which is a once-in-50-yr rainfall event. High stream discharges were generated that, combined with wind-suspended sediments,
significantly reduced salinities and water transparency. In September, salinities among central IRL segments dropped from
30 psu or more to ≤15 psu, color increased from a low of 10 pcu to ≥100 pcu, and turbidity increased from ≤3 NTU up to 14
NTU. Evidence of the hurricanes' physical effects on seagrasses (burial, no scour) was limited to just one of the more than
25 sites inspected. Within 2 to 3 mo following the hurricane period, most parameters related to water transparency returned
to or showed improvement over their prehurricane (February–July 2004) levels. Unseasonably low salinities (<20 psu) and moderately
high color (>20 pcu) were observed through spring 2005, largely attributable to a relatively long residence time and a wetter-than-average
spring season in 2005. By the end of the study period (July 2006), the central IRL generally showed a continuation of two
opposite seagrass trends—an increase in depthlimit coverage but a decline in coverage density—that began before 2004. Also,
within a limited reach of the central IRL, there was a temporary shift in species composition in summer 2005 (Ruppia maritima increased asHalodule wrightü decreased). It is likely that the persistently low salinities (not color) in 2004–2005 affected the species composition and
coverage density. This study reveals that seagrasses are resilient to the acute effects of hurricanes and underscores the
need to reduce chronic, an thropogenic effects on seagrasses. 相似文献
207.
Effects of mesoscale physical processes on thin zooplankton layers at four sites along the west coast of the U.S. 总被引:1,自引:0,他引:1
Olivia M. Cheriton Margaret A. McManus D. V. Holliday Charles F. Greenlaw Percy L. Donaghay Tim J. Cowles 《Estuaries and Coasts》2007,30(4):575-590
Within the coastal marine environment, populations of phytoplankton, zooplankton, bacteria, viruses, and aggregations of marine
snow are frequently concentrated beneath the surface in discrete, vertically thin layers. Thin layers range in vertical dimension
from a few centimeters to three meters, and have been observed to extend horizontally for kilometers. They appear in the water
column episodically and can persist for days. We present some of the results of an investigation of four coastal sites along
the west coast of the United States to assess frequency of occurrence of thin layers of zooplankton. Our study sites included
coastal sites near East Sound, Washington; Cape Perpetua, Oregon; Monterey Bay, California; and Santa Barbara, California.
At each site, we collected several, weeks-long time series of hydrography, current velocity, and acoustic backscatter due
to mesozooplankton. Our results show that thin layers were common features at all four sites. Across all study sites, a change
in the predominant physical regime, usually precipitated by a change in the wind pattern, corresponded with an absence of
thin Zooplankton layers. In order to make a first-order prediction about when thin layers have the possibility of occurring
in a coastal environment, we found it useful to examine regional wind and circulation patterns and to determine how they affect
stratification in each local environment. 相似文献
208.
Margaret E Marker 《The Geographical journal》2003,169(1):32-42
The Knysna Basin, a southern Cape catchment, drains into the Knysna estuary. The landscape characteristics are the product of a long geomorphic evolution resulting in high sensitivity to change. Consideration of the geomorphology is followed by examples of impacts on the estuary and adjacent areas. The need for sustainability in the context of development is argued. The paper is a southern African contribution to the landscape sensitivity issue. 相似文献
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The relationship between uniaxial compressive strength and degradation was investigated for selected rock types, by using regression analyses to determine whether degradation was a useful predictor of compressive strength. In addition, the effects of aggregate particle size, number of hammer blows during the degradation test, engineering index properties, petrographic characteristics, and water saturation on the compressive strength-degradation relationship were evaluated. The results show that strong inverse relationships exist between compressive strength and degradation (measured on a 9.5-4.75-mm size aggregate) for sandstones and igneous/metamorphic rocks, but that no significant relationship exists for limestones/dolomites. The results also indicate a strong positive correlation between degradation and L.A. abrasion loss and can be used to establish a limit of allowable degradation for practical applications. Engineering index properties do not significantly affect the relationship between compressive strength and degradation but petrographic characteristics are important in explaining the strength and degradation behavior of the rocks studied. Water saturation decreases compressive strength and increases degradation to varying degrees. 相似文献