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41.
We use unit records of the 2006 census to show that access to the Internet in the home varies geographically in New Zealand primarily as a result of demographic and socio‐economic differences among individuals. Of particular significance is the much lower rates of domestic access experienced by Māori and Pacific Island individuals even after controlling for differences in their age, gender, education, income, occupation and settlement type. While differences in Internet access by ethnicity has been noted before, it is the magnitude and persistence of this difference in New Zealand after controlling for correlated factors that renders this study unique. Our results have important implications in an education environment increasingly reliant on Web access, but they also raise questions about the extent of access to the Internet outside the home. 相似文献
42.
A method is presented to evaluate ground water residence time in a zero‐valent iron (ZVI) permeable reactive barrier (PRB) using radon‐222 (222Rn) as a radioactive tracer. Residence time is a useful indicator of PRB hydraulic performance, with application to estimating the volumetric rate of ground water flow through a PRB, identifying flow heterogeneity, and characterizing flow conditions over time as a PRB matures. The tracer method relies on monitoring the decay of naturally occurring aqueous 222Rn as ground water flows through a PRB. Application of the method at a PRB site near Monticello, Utah, shows that after 8 years of operation, residence times in the ZVI range from 80 to 486 h and correlate well with chemical parameters (pH, Ca, SO4, and Fe) that indicate the relative residence time. Residence times in this case study are determined directly from the first‐order decay equation because we show no significant emanation of 222Rn within the PRB and no measurable loss of 222Rn other than by radioactive decay. 相似文献
43.
Nicola Morrison 《GeoJournal》2000,51(4):339-349
This paper provides an overview of the current literature on why difficulties are being experienced in letting social housing within England. The first part of the paper focuses on whether the management of the social housing stock, and in particular the current allocation system, has contributed to the growing number of difficult to let (DTL) properties in the social sector. Drawing on findings from in-depth interviews with twenty local authorities, the paper provides evidence to support this argument and also highlights a number of initiatives which authorities have adopted to fill DTL properties. However, the paper argues that these initiatives are likely to have limited value in the long run in stemming the fall in demand for social housing, particularly in the North of England. The second part of the paper focuses on the changing aspirations of tenants and the way that social housing is in competition with alternative forms to housing provision, such as private rented housing. It concludes by advocating that an appropriate response to difficulties in letting social housing has to go beyond internal housing management initiatives. Instead a more strategic approach needs to be adopted which builds up an understanding of the operation of the local housing market and the complex interaction of neighbourhoods. 相似文献
44.
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46.
The Soft X-ray Telescope for the SOLAR-A mission 总被引:6,自引:0,他引:6
S. Tsuneta L. Acton M. Bruner J. Lemen W. Brown R. Caravalho R. Catura S. Freeland B. Jurcevich M. Morrison Y. Ogawara T. Hirayama J. Owens 《Solar physics》1991,136(1):37-67
The Soft X-ray Telescope (SXT) of the SOLAR-A mission is designed to produce X-ray movies of flares with excellent angular and time resolution as well as full-disk X-ray images for general studies. A selection of thin metal filters provide a measure of temperature discrimination and aid in obtaining the wide dynamic range required for solar observing. The co-aligned SXT aspect telescope will yield optical images for aspect reference, white-light flare and sunspot studies, and, possibly, helioseismology. This paper describes the capabilities and characteristics of the SXT for scientific observing.After the launch the name of SOLAR-A has been changed to YOHKOH. 相似文献
47.
Distinguishing magmatic from subsolidus epidote: laser probe oxygen isotope compositions 总被引:1,自引:0,他引:1
Epidote occurs in four textural varieties in the Mount Lowe intrusion of southern California: euhedra, anhedra, intergrowths
and cross-cutting veins. Of these, conspicuous elongate euhedra, which range up to 3 cm in length, meet most of the established
textural criteria for magmatic epidote. Equant anhedral grains, which are ˜5 mm in diameter, are texturally ambiguous although
rare allanite cores are suggestive of a magmatic origin. Epidote intergrowths with hornblende and biotite also meet certain
textural criteria for crystallization from a magma, notably, euhedral faces against biotite. Finally, late-stage veins of
epidote cross-cut all phases in the rock and are likely subsolidus. Oxygen isotopic compositions of these four textural varieties
of epidote determined using the laser probe indicate that the use of textural criteria alone in establishing epidote parageneses
can be misleading. Intracrystalline δ18O variations in the euhedra document both magmatic and subsolidus compositions. Oxygen isotope compositions are bimodal averaging
5.36 ± 0.13‰ (n = 11) and 4.66 ± 0.23‰ (n = 21). These data combined with plagioclase and zircon δ18O values are interpreted to indicate that magmatic oxygen isotopic compositions have been preserved where epidote δ18O is greater than 5‰. Significant portions of each euhedral crystal have been affected by subsolidus exchange and are characterized
by epidote δ18O values less than 5‰. Intracrystalline δ18O values of epidote anhedra range from 4.50 to 6.08‰ and thus also document both magmatic and subsolidus compositions. Subsolidus
exchange is volumetrically less significant in the anhedra than in the euhedra. Values of δ18O for intergrowths and late-stage cross-cutting veins of epidote average 3.81 ± 0.22‰ and document clearly subsolidus growth.
The data confirm that in the Mount Lowe intrusion, large euhedra of epidote are magmatic in origin, consistent with textural
evidence. The data also indicate that equant anhedra of epidote are also magmatic in origin and thus the absence of good crystal
faces does not necessarily indicate subsolidus growth. The subsolidus origin of intergrowths of epidote with euhedral faces
against biotite indicates that well developed crystal faces do not require growth from a magma. Finally, the subsolidus origin
of the vein epidote is consistent with textural evidence. The increased resolution available with laser-based oxygen isotope
measurements offers an important test for documenting whether epidote is of magmatic or subsolidus origin. Given the barometric
significance of magmatic epidote, oxygen isotope compositions can be used to aid in the interpretation of epidote-bearing
plutons.
Received: 9 April 1996 / Accepted: 3 August 1996 相似文献
48.
Kosovichev A. G. Schou J. Scherrer P. H. Bogart R. S. Bush R. I. Hoeksema J. T. Aloise J. Bacon L. Burnette A. De Forest C. Giles P. M. Leibrand K. Nigam R. Rubin M. Scott K. Williams S. D. Basu Sarbani Christensen-dalsgaard J. DÄppen W. Duvall T. L. Howe R. Thompson M. J. Gough D. O. Sekii T. Toomre J. Tarbell T. D. Title A. M. Mathur D. Morrison M. Saba J. L. R. Wolfson C. J. Zayer I. Milford P. N. 《Solar physics》1997,170(1):43-61
The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the main component of which is Gaussian-weighted binning, has been optimized to reduce the negative influence of spatial aliasing of the high-degree oscillation modes. The data processing is completed in a data analysis pipeline at the SOI Stanford Support Center to determine the mean multiplet frequencies and splitting coefficients. The initial results show that the noise in the medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. This is important for inferring the Sun's internal structure and rotation. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. The results also confirm the previous finding by the GONG (Gough et al., 1996) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer. This layer is likely to be the place where the solar dynamo operates. In order to understand how the Sun works, it is extremely important to observe the evolution of this transition layer throughout the 11-year activity cycle. 相似文献
49.
L V Morrison P Gibbs L Helmer C Fabricius O Einicke Y Réquième M Rapaport 《Astrophysics and Space Science》1991,177(1-2):31-34
Analyses of FK5 stars observed in 1986 with the Carlsberg Automatic Meridian Circle on La Palma and the automatic meridian circle at Bordeaux Observatory produce evidence of systematic errors in the FK5 reaching 0
.
1 in size. 相似文献
50.
Christina L. Tague Shirley A. Papuga Cynthia Gerlein-Safdi Salli Dymond Ryan R. Morrison Elizabeth W. Boyer Diego Riveros-Iregui Elizabeth Agee Bhavna Arora Yannis G. Dialynas Amy Hansen Stefan Krause Sylvain Kuppel Steven P Loheide II Stanislaus J. Schymanski Samuel C Zipper 《水文研究》2020,34(7):1665-1673