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1.
2.
Using a modified extraction procedure, the effect of pH on the leaching of selected elements from Ca-rich (Type C) power plant fly ash was studied. Continuous additions of acetic acid were used to maintain pH values of fly ash slurries at 4.0, 6.0 and 8.0 for 24 h and an additional set was leached at its natural pH (average 11.8) value. Analyses for Se, As, Ca, Cd, Cr, Fe, Na and Pb showed that the highest concentrations occur in the leachate at pH 4.0 and decline with increasing pH. Concentrations of Cr and Fe increased slightly between neutral and high pH. Arsenic, Cd, Cr, Pb and Se concentrations exceeded the Environmental Protection Agency's toxicity criteria at pH 4.0. Selenium was above its toxicity level at pH values near 7 but the other elements were below their respective toxicity levels near neutral pH. Because recent studies show adverse effects of Se on aquatic life at far lower concentrations than the current Environmental Protection Agency's standard, high-Ca, power plant fly ashes represent a potentially hazardous pollutant to surface and subsurface waters. 相似文献
3.
In recent years, artificial establishment of Spartina alterniflora marshes has become a common method for mitigating impacts to salt marsh systems. The vegetative component of artificially established salt marshes has been examined in several studies, but relatively little is known about the other aspects of these systems. This study was undertaken to investigate the infaunal community of artificially established salt marshes. Infauna were sampled from pairs of artificially established (AE) salt marshes and nearby natural marshes at six sites along the North Carolina coast. The AE marshes ranged in age from 1 yr to 17 yr. Total infaunal density, density of dominant taxa, and community trophic structure (proportions of subsurface-deposit feeders, surface-deposit and suspension feeders, and carnivores) were compared between the two types of marsh to assess infaunal community development in AE marshes. Overall, the two marsh types had similar component organisms and proportions of trophic groups, but total density and densities within trophic groupings were lower in the AE marshes. Soil organic matter content of the natural marshes was nearly twice that of the AE marshes, and is a possible cause for the higher infaunal densities observed in the natural marshes, Using the same three criteria, comparisons of the natural and AE marshes at each of the six locations revealed varying degrees of similarity. Similarity of each AE marsh to its natural marsh control appeared to be influenced by differences in environmental factors between locations more than by AE marsh age. Functional infaunal habitat convergence of an AE marsh with a natural marsh somewhere within its biogeographical region is probable, but success in duplicating the infaunal community of a particular natural marsh is contingent upon the developmental age of the natural marsh and the presence and interaction, of site-specific factors. 相似文献
4.
Concentration data on 73 individual constituents in United States Geological Survey (USGS) Geochemical Exploration Reference Materials GXR-1 to GXR-6 have been collected from 131 journal articles and technical reports. These data are summarized as consensus (mean) values with uncertainties expressed as one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables. Recommended values are proposed based upon data criteria used by NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards or NBS). 相似文献
5.
Ernest S. GLADNEY Colleen E. BURNS Iwan Roelandts 《Geostandards and Geoanalytical Research》1985,9(1):35-68
Concentration data for as many as 72 constituents in the four Canadian Certified Reference Materials Project (CCRMP) soil samples have been collected from journal articles and technical reports published since these soil standards were issued in 1978. These data are summarized into mean +/- one standard deviation values and compared with available certification data from CCRMP. All literature data located or calculated are presented in the appendices. 相似文献
6.
Ernest S. GLADNEY David B. CURTIS Daniel R. PERRIN 《Geostandards and Geoanalytical Research》1984,8(1):43-46
Concentrations of boron in 35 silicate reference materials are measured by thermal neutron capture gamma-ray spectrometry. Results are compared for NBS, USGS, and CCRMP reference materials with values from the literature. The use of two prompt gamma facilities at Los Alamos are discussed. 相似文献
7.
John M. Jones Alan Davis Alan C. Cook Duncan G. Murchison Ernest Scott 《International Journal of Coal Geology》1984,3(4):315-331
Optical and chemical properties for hand-picked samples of vitrinite from a number of British coalfields are correlated and the correlations compared with previously published data. The form of the relationship found for the properties of British vitrinites is generally similar to that exhibited by a number of other sets of analyses, but some significant differences also exist in several of the correlations. For maximum reflectance as a function of carbon content, the present data indicate that at medium and low ranks, maximum reflectance is lower than the level suggested by most previous studies. The relationships of volatile-matter yield to reflectance and carbon content suggest that at low ranks, volatile-matter yield is strongly dependent upon the nature of the coalification history of the vitrinite. Furthermore, these correlations are likely to show provincialism, in that correlations which hold for one coalfield may not be representative of the relationship in other coalfields. Similarly, major differences in relationships involving bireflectance are associated with the tectonic setting at the time of effective coalification. The data presented here indicate that for low-rank coals at least, correlations between properties of vitrinites must take account of provincialism if they are to be sufficiently reliable to be useful. The measurement of a number of rank-sensitive variables can yield additional information about rank, as compared with the use of a single rank-sensitive variable. 相似文献
8.
Ernest S. GLADNEY Colleen E. BURNS Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1983,7(1):3-6
Elemental composition data on eight older (AGV-1, BCR-1, DTS-1, G-1, G-2, GSP-1, PCC-1 and W-1) and three newer (BIR-1, DNC-1 and W-2) USGS rock standards have been collected from institutional reports and journal articles from 1972–1981. This collection was combined with data from previous compilations and "consensus values" for up to 79 elements determined by comparing overall means, medians, and individual means based on analytical techniques. 相似文献
9.
A first-order one-way wave system has been created based on characteristic analysis of the acoustic wave system and optimization of the dispersion relation. We demonstrate that this system is equivalent to a third-order scalar partial-differential equation which, for a homogeneous medium, reduces to a form similar to the 45° paraxial wave equation. This system describes accurately waves propagating in a 2D heterogeneous medium at angles up to 75°. The one-way wave system representing downgoing waves is used for a modified reverse time migration method. As a wavefield extrapolator in migration, the downgoing wave system propagates the reflection events backwards to their reflectors without scattering at the discontinuities in the velocity model. Hence, images with amplitudes proportional to reflectivity can be obtained from this migration technique. We present examples of the application of the new migration method to synthetic seismic data where P-P reflections P-SV converted waves are present. Absorbing boundaries, useful in the generation of synthetic seismograms, have been constructed by using the one-way wave system. These boundaries absorb effectively waves impinging over a wide range of angles of incidence. 相似文献
10.