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91.
G. L. Withbroe A. K. Dupree L. Goldberg M. C. E. Huber R. W. Noyes W. H. Parkinson E. M. Reeves 《Solar physics》1971,21(2):272-280
We have analyzed daily Mgx 625 spectroheliograms acquired by the Harvard College Observatory experiment on OSO-6 for a 28-day period centered on 7 March, 1970, the date of a well-observed total solar eclipse. These data are used to construct maps of the variation across the solar disk of the electron density at the base of the corona. The correspondence of high and low density regions with regions of enhanced and reduced emission in white light and Mgx pictures made during or near the time of the eclipse are described. 相似文献
92.
Tore Prestvik Steven Goldberg Haraldur Karlsson Karl Grnvold 《Earth and Planetary Science Letters》2001,190(3-4):211-220
The currently active off-rift central volcano Öræfajökull in south-east Iceland sits unconformably on much older (10–12 Ma) and eroded crust. The composition of recent volcanics ranges from basalt to rhyolite, but the series is more sodic alkaline than the common rift zone tholeiitic suites. In this study we present Sr, Nd, Pb and O isotopic data for a suite of Öræfajökull samples. The complete suite shows typical mantle values for oxygen isotopes. The 87Sr/86Sr ratios (average of 15 SAMPLES=0.703702) of the modern Öræfajökull rocks (basalts as well as rhyolites) are much higher than observed so far for any other Icelandic rocks. The 143Nd/144Nd ratios (average=0.512947; n=15) are lower than for rift rocks, but similar to rocks of the off-rift Snæfellsnes volcanic zone. Furthermore, the Öræfajökull rocks are enriched in the 207Pb/204Pb and 208Pb/204Pb isotope ratios compared to Icelandic rift basalts. The enriched nature of the suite indicates that Öræfajökull samples a source component that has characteristics common with EM2 type mantle. Furthermore, it is concluded that the silicic rocks of Öræfajökull formed by fractional crystallization from mafic melts rather than by partial melting of older crust. 相似文献
93.
As part of a study investigating the naturally-occurring fractures in mafic rocks, two holes were drilled 450 m apart through
the Palisades dolerite sill in New York. Well-2 is 229 m deep and Well-3 was drilled to 305 m, both penetrating through the
sill and into the underlying Triassic sediments of the Newark Basin. Both holes were logged with downhole geophysical tools,
including the BHTV, which acoustically images fractures intersecting the well. Understanding the fracture pattern, density,
and porosity in the sill is essential for identifying possible zones of active fluid flow and high permeability. Using the
BHTV logs, 96 and 203 fractures were digitally mapped within the sill in Well-2 and Well-3, respectively. Most fractures appear
to dip steeply (76-78°). There is a shift in fracture orientation, however, and these fractures may or may not be continuous
over the short lateral distance between Well-2 and Well-3. The lithology of the sill as identified by drill chips is nevertheless
continuous between the holes. Both intersect a 7 m thick olivine-rich layer about 15 m above the bottom of the sill.
Several fractures identified in Well-2 have large apparent aperture (>6cm) which correspond to high porosity zones (6-14%)
observed in the logs. Resistivity logs were used to compute porosity using Archie's law and match well with the neutron porosity
log in Well-2. We use the relationship between porosity and fracture aperture within the sill at Well-2 to infer the porosity
in Well-3. High-porosity, large-aperture zones, including the target olivine layer, are identified in both holes. Changes
in the temperature gradient log indicate active fluid flow in the sill, although flow appears to be most active in the sediments.
Direct field measurements of bulk permeability, hydrologic modeling of fluid flow and calibration of fracture and log porosity
will be undertaken in the future. 相似文献
94.
95.
Ofer Lahav Noah Brosch Evgeny Goldberg George K. T. Hau Renée C. Kraan-Korteweg & Andy J. Loan 《Monthly notices of the Royal Astronomical Society》1998,299(1):24-30
Motivated by recent discoveries of nearby galaxies in the Zone of Avoidance (ZOA), we conducted a pilot study of galaxy candidates at low galactic latitude, near galactic longitude l ∼ 135°, where the Supergalactic plane is crossed by the Galactic plane. We observed with the 1-m Wise Observatory in the l band 17 of the 'promising' candidates identified by visual examination of Palomar red plates by Hau et al. A few candidates were also observed in R or B bands, or had spectroscopic observations performed at the Isaac Newton Telescope and at the Wise Observatory. Our study suggests that there are probably 10 galaxies in this sample. We also identify a probable planetary nebula. The final confirmation of the nature of these sources must await the availability of full spectroscopic information. The success rate of ∼ 50 per cent in identifying galaxies at galactic latitude | b | < 5° indicates that the ZOA is a promising region to discover new galaxies. 相似文献
96.
Potential Effects of Global Warming on Waterfowl Populations Breeding in the Northern Great Plains 总被引:4,自引:0,他引:4
Lisa G. Sorenson Richard Goldberg Terry L. Root Michael G. Anderson 《Climatic change》1998,40(2):343-369
The Prairie Pothole Region (PPR) of the Northern Great Plains is the most important breeding area for waterfowl in North America. Historically, the size of breeding duck populations in the PPR has been highly correlated with spring wetland conditions. We show that one indicator of climate conditions, the Palmer Drought Severity Index (PDSI), is strongly correlated with annual counts (from 1955 to 1996) of both May ponds (R2 = 0.72, p < 0.0001) and breeding duck populations (R2 = 0.69, p < 0.0001) in the Northcentral U.S., suggesting the utility of PDSI as an index for climatic factors important to wetlands and ducks. We then use this relationship to project future pond and duck numbers based on PDSI values generated from sensitivity analyses and two general circulation model (GCM) scenarios. We investigate the sensitivity of PDSI to fixed changes in temperature of 0°C, +1.5°C, +2.5°C, and +4.0°C in combination with fixed changes in precipitation of -10%, +0%, +7%, and +15%, changes spanning the range of typically-projected values for this region from human-induced climatic change. Most (11 of 12) increased temperature scenarios tested result in increased drought (due to greater evapotranspiration under warmer temperatures) and declining numbers of both wetlands and ducks. Assuming a doubling of CO2 by 2060, both the equilibrium and transient GCM scenarios we use suggest a major increase in drought conditions. Under these scenarios, Northcentral U.S. breeding duck populations would fluctuate around means of 2.1 or 2.7 million ducks based on the two GCMs, respectively, instead of the present long-term mean of 5.0 million. May pond numbers would fluctuate around means of 0.6 or 0.8 million ponds instead of the present mean of 1.3 million. The results suggest that the ecologically and economically important PPR could be significantly damaged by climate changes typically projected. We make several recommendations for policy and research to help mitigate potential effects. 相似文献
97.
Sergey Alexandrovich Gorbarenko Evgenia L’vovich Goldberg Michaele Kashgarian Tat’yana Alekseevna Velivetskaya Sergey Petrovich Zakharkov Vladimir Stepanovich Pechnikov Alexandr Anatol’evich Bosin Olga Yur’evna Psheneva Elena Diamilevna Ivanova 《Journal of Oceanography》2007,63(4):609-623
The paper presents the records of several paleoproductivity proxies (PP) (biogenic opal and Ba (Si_bio, Ba_bio), organic carbon
(C_org) and carbonate Ca_carb, chlorin and benthic foraminifera abundance (BFA)) in sediments of the Okhotsk Sea for the last
80 kyr with a resolution of ∼100–300 years. The sediment age model was based on the AMS 14C data, records of benthic foraminifera δ18O, paleointensity of the Earth’s geomagnetic field and magnetic susceptibility. PP values demonstrate series of severe prolonged
productivity drops in the Okhotsk Sea followed by a sharp increase during the last glaciation. On the basis of quantitative
estimations of the paleoproductivity in the Okhotsk Sea during the cold MIS 2 and warm Holocene (Gorbarenko and Goldberg,
2005), it is suggested that the millennium scale relationship in productivity-climate changes of this basin was similar: an
increase in the sea’s productivity was related with regional climate warming and vice-versa. The PP records of productivity/climate
oscillations in the Okhotsk Sea during MIS 2–4 occurred contemporaneously with the North Atlantic cold Heinrich events (HE)
and Greenland Dansgaard-Oyeshger interstadial (DOI). Observed successions of prolonged climate cooling events followed by
rapid, abrupt warming are similar to climate and environmental oscillations in the N. Atlantic and Greenland, that confirms
the millennium-scale climate changes synchronicities in the Northern Hemisphere including the far NW Pacific, the hydrology
and climate conditions of which are close to those of the Okhotsk Sea. Synchronism of the N. Hemisphere severe cooling (including
the Okhotsk Sea) with the Antarctic warming suggests that mechanisms of the “seesaw” effect (Blunier and Brook, 2001) in the
low latitude heat redistribution between high latitudes of both hemispheres were more complicated than direct NADW formation
forcing and encompasses the global atmospheric reorganization. Within the PP used a closer connection in the Okhotsk Sea millennium
oscillations was observed for the C_org, BFA and chlorin; Ba_bio increases more closely to DOI. Si_bio variability does not
show any evident correlation with productivity changes. 相似文献
98.
Bivalve shells offer several advantages over tissues for the monitoring of heavy metal pollutants in the marine environment. They are easier to handle and to store. The problem of whether to depurate the animals before analyses is avoided. The shells appear to be more sensitive to environmental heavy metals levels over the long term than do the soft parts. Of the substances examined (Cd, Cu, Zn, Pb, Ag, Ni, 238Pu and 239 + 240Pu) only Pb and Pu displayed a strong covariance between soft tissue and shell concentrations. There were strong correlations between metals in the shell but not in the soft tissues in general. The byssal threads, because of their enrichment of transuranic elements and of their ease in handling, may be useful in monitoring these metals. A very weak discharge of 238Pu to marine waters adjacent to a nuclear reactor was detected in the byssal threads of mussels. 相似文献
99.
J. L. Sericano T. L. Wade T. J. Jackson J. M. Brooks B. W. Tripp J. W. Farrington L. D. Mee J. W. Readmann J. -P. Villeneuve E. D. Goldberg 《Marine pollution bulletin》1995,31(4-12)
The National Status & Trends (NS&T, 1986–1993) and the International Mussel Watch (IMW, 1991–1992) programmes provide a good coverage of a broad range of environmental conditions along the North, Central and South American coasts. Total concentrations of DDTs, chlordane-related compounds, PCBs and PAHs present fairly homogeneous distributions along the northern Gulf of Mexico coast, with very few sites showing extremely high or low concentrations. In contrast, a larger variability in the geographical distribution of some of these organic contaminants was observed for IMW sites. For example, high concentrations of DDT and its metabolites, DDD and DDE, were generally found in tropical and subtropical areas as compared to more temperate zones of South America. ‘Industrial’ contaminants, such as PCBs and PAHs, have similar distributions with the highest concentrations encountered generally along the southern South Atlantic coast. An overall comparison of the concentrations of these organic contaminants measured at NS&T and IMW sites indicates that contamination is significantly higher along the northern coast of the Gulf of Mexico. 相似文献
100.