全文获取类型
收费全文 | 137篇 |
免费 | 2篇 |
国内免费 | 3篇 |
专业分类
大气科学 | 13篇 |
地球物理 | 52篇 |
地质学 | 42篇 |
海洋学 | 12篇 |
天文学 | 18篇 |
自然地理 | 5篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 93 毫秒
61.
Lamé modulus (λ) and shear modulus (μ) are among the most important,intrinsic,elastic constants of rocks.Using λ and μ could be much more advantageous than using P- and S-wave velocities (Vp and Vs).He... 相似文献
62.
H. Holweger 《Solar physics》1972,25(1):14-29
An abundance analysis of the solar calcium spectrum is carried out using 46 lines with known f-values in the visible and near infrared spectral region. Resonance, forbidden and autoionizing lines are included. The solar abundance of calcium resulting from the 25 weaker, nearly damping-independent lines only is log Ca=6.36±0.07, on the scale log H = 12. The great variety of transitions involved in the solar calcium spectrum, ranging from 0 eV lines of CaI to 7.5 eV lines of CaII and including autoionizing lines, are in reasonable agreement (Figure 1b). Therefore notable non-LTE effects on their equivalent widths can be excluded.Together with the sodium abundance log
Na = 6.30 determined earlier, the solar abundance ratio Ca/Na = 1.15 is obtained with an accuracy of 10%. Comparison with meteorites (carbonaceous chondrites I) shows that solar and meteoritic ratio agree within these limits.The line broadening by collisions with hydrogen atoms is determined empirically from a comparison of weak and strong Fraunhofer lines of CaI and CaII, thereby using the solar atmosphere as an absorption tube of comparatively well-known physical state. The damping half-widths H turn out to be larger than predicted from pure van der Waals interaction, the average enhancement factor being 3.0 for CaI and 1.7 for CaII, independent of term properties to a first approximation. Regardless of the reason for this enhancement — inaccurate van der Waals theory or predominance of repulsive interaction these results can be used in the spectroscopy of other stars. 相似文献
63.
64.
Comparison of gravity current mixing parameterizations and calibration using a high-resolution 3D nonhydrostatic spectral element model 总被引:1,自引:3,他引:1
Yeon S. Chang Xiaobiao Xu Tamay M.
zgkmen Eric P. Chassignet Hartmut Peters Paul F. Fischer 《Ocean Modelling》2005,10(3-4):342-368
In light of the pressing need for development and testing of reliable parameterizations of gravity current entrainment in ocean general circulation models, two existing entrainment parameterization schemes, K-profile parameterization (KPP) and one based on Turner’s work (TP), are compared using idealized experiments of dense water flow over a constant-slope wedge using the HYbrid Coordinate Ocean Model (HYCOM). It is found that the gravity current entrainment resulting from KPP and TP differ significantly from one another. Parameters of KPP and TP are then calibrated using results from the high-order nonhydrostatic spectral element model Nek5000. It is shown that a very good agreement can be reached between the HYCOM simulations with KPP and TP, even though these schemes are quite different from each other. 相似文献
65.
Herbert Kroll Hartmut Schlenz Michael W. Phillips 《Physics and Chemistry of Minerals》1994,21(8):555-560
The excess Gibbs free energy due to non-convergent ordering is described by a Landau expansion in which configurational and non-configurational entropy contributions are separated:
相似文献
66.
Hartmut Beurlen Marcelo R. R. Da Silva Rainer Thomas Dwight R. Soares Patrick Olivier 《Mineralium Deposita》2008,43(2):207-228
The Borborema Pegmatitic Province (BPP), northeastern Brazil, is historically important for tantalum mining and also famous
for top-quality specimens of exotic Nb–Ta oxides and, more recently, for the production of gem quality, turquoise blue, ‘Paraíba
Elbaite.’ With more than 750 registered mineralized rare-element granitic pegmatites, the BPP extends over an area of about
75 by 150 km in the eastern part of the Neoproterozoic Seridó Belt. The Late Cambrian pegmatites are mostly hosted by a sequence
of Neoproterozoic cordierite–sillimanite biotite schists of the Seridó Formation and quartzites and metaconglomerates of the
Equador Formation. The trace-element ratios in feldspar and micas allow to classify most pegmatites as belonging to the beryl–columbite
phosphate subtype. Electron microprobe analyses (EMPA) of columbite, tapiolite, niobian–tantalian rutile, ixiolite and wodginite
group minerals from 28 pegmatites in the BPP are used to evaluate the effectiveness of Nb–Ta oxide chemistry as a possible
exploration tool, to trace the degree of pegmatite fractionation and to classify the pegmatites. The columbite group mineral
composition allows to establish a compositional trend from manganoan ferrocolumbite to manganocolumbite and on to manganotantalite.
This trend is typical of complex spodumene- and/or lepidolite-subtype pegmatites. It clearly contrasts with another trend,
from ferrocolumbite through ferrotantalite to ferrowodginite and ferrotapiolite compositions, typical of pegmatites of the
beryl–columbite phosphate subtype. Large scatter and anomalous trends in zoned crystals partially overlap and conceal the
two main evolution patterns. This indicates that a large representative data set of heavy mineral concentrate samples, collected
systematically along cross-sections, would be necessary to predict the metallogenetic potential of individual pegmatites.
Other mineral species, e.g. garnets and/or tourmaline, with a more regular distribution than Nb–Ta oxides, would be more appropriate
and less expensive for routine exploration purposes. The currently available Nb–Ta oxide chemistry data suggest the potential
for highly fractionated Ta–Li–Cs pegmatites in the BPP, so far undiscovered, and encourages further, more detailed research. 相似文献
67.
We present a model that may explain deep crustal earthquakes observed, in particular, in several areas of highly reflective (laminated) lower continental crust. We combine observations from earthquake seismology, crustal reflection seismics and tectonic-rheological concepts. The study concentrates on parts of the northern Alpine foreland where many earthquakes occur inside the laminated lower crust, which is generally considered to be warm and weak. Thin mafic/ultramafic, sill-like intrusions and invisible dykes are assumed to form a corset-like network with high strength. This model can explain the observed strong and multiple reflections and the occurrence of rupture inside a stable structure within a weak lower crust. Tectonic stress transfer (from the Alpine collision zone or/and the Upper Rhine Graben) and its release may follow classical friction concepts. In addition, the heterogeneity of the laminated lower crust may also favour various viscous instabilities. 相似文献
68.
69.
David Storz Hartmut Schulz Joanna J. Waniek Detlef E. Schulz-Bull Michal Kučera 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):107-124
Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic. 相似文献
70.
We comment briefly on a recent paper by Fuhrmann which claims that about half of the sample of halo stars in the solar neighbourhood presented by Fuchs and Jahreiß [A&A 329 (1998) 81] are actually thick disc stars. By referring to star counts in the CADIS survey we argue that this is rather unlikely. 相似文献
|