全文获取类型
收费全文 | 180篇 |
免费 | 8篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 20篇 |
地球物理 | 42篇 |
地质学 | 69篇 |
海洋学 | 17篇 |
天文学 | 29篇 |
综合类 | 1篇 |
自然地理 | 21篇 |
出版年
2023年 | 2篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1977年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 15 毫秒
91.
Irina M. Artemieva 《Tectonophysics》2006,416(1-4):245
This paper reports a new 1° × 1° global thermal model for the continental lithosphere (TC1). Geotherms for continental terranes of different ages (> 3.6 Ga to present) constrained by reliable data on borehole heat flow measurements (Artemieva, I.M., Mooney, W.D. 2001. Thermal structure and evolution of Precambrian lithosphere: a global study. J. Geophys. Res 106, 16387–16414.), are statistically analyzed as a function of age and are used to estimate lithospheric temperatures in continental regions with no or low-quality heat flow data (ca. 60% of the continents). These data are supplemented by cratonic geotherms based on electromagnetic and xenolith data; the latter indicate the existence of Archean cratons with two characteristic thicknesses, ca. 200 and > 250 km. A map of tectono-thermal ages of lithospheric terranes complied for the continents on a 1° × 1° grid and combined with the statistical age relationship of continental geotherms (z = 0.04 t + 93.6, where z is lithospheric thermal thickness in km and t is age in Ma) formed the basis for a new global thermal model of the continental lithosphere (TC1). The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continental upper mantle, with the strongest lateral temperature variations (as large as 800 °C) in the shallow mantle. A map of the depth to a 550 °C isotherm (Curie isotherm for magnetite) in continental upper mantle is presented as a proxy to the thickness of the magnetic crust; the same map provides a rough estimate of elastic thickness of old (> 200 Ma) continental lithosphere, in which flexural rigidity is dominated by olivine rheology of the mantle.Statistical analysis of continental geotherms reveals that thick (> 250 km) lithosphere is restricted solely to young Archean terranes (3.0–2.6 Ga), while in old Archean cratons (3.6–3.0 Ga) lithospheric roots do not extend deeper than 200–220 km. It is proposed that the former were formed by tectonic stacking and underplating during paleocollision of continental nuclei; it is likely that such exceptionally thick lithospheric roots have a limited lateral extent and are restricted to paleoterrane boundaries. This conclusion is supported by an analysis of the growth rate of the lithosphere since the Archean, which does not reveal a peak in lithospheric volume at 2.7–2.6 Ga as expected from growth curves for juvenile crust.A pronounced peak in the rate of lithospheric growth (10–18 km3/year) at 2.1–1.7 Ga (as compared to 5–8 km3/year in the Archean) well correlates with a peak in the growth of juvenile crust and with a consequent global extraction of massif-type anorthosites. It is proposed that large-scale variations in lithospheric thickness at cratonic margins and at paleoterrane boundaries controlled anorogenic magmatism. In particular, mid-Proterozoic anorogenic magmatism at the cratonic margins was caused by edge-driven convection triggered by a fast growth of the lithospheric mantle at 2.1–1.7 Ga. Belts of anorogenic magmatism within cratonic interiors can be caused by a deflection of mantle heat by a locally thickened lithosphere at paleosutures and, thus, can be surface manifestations of exceptionally thick lithospheric roots. The present volume of continental lithosphere as estimated from the new global map of lithospheric thermal thickness is 27.8 (± 7.0) × 109 km3 (excluding submerged terranes with continental crust); preserved continental crust comprises ca. 7.7 × 109 km3. About 50% of the present continental lithosphere existed by 1.8 Ga. 相似文献
92.
Mikko Kaasalainen Petr Pravec Lenka Šarounová Jenni Virtanen Anders Erikson Josef ?urech Johan S.V. Lagerros Claes-Ingvar Lagerkvist John Davies Peter Kušnirák Vasilij G. Shevchenko Irina N. Belskaya 《Icarus》2004,167(1):178-196
We present new observations and models of the shapes and rotational states of the eight near-Earth Asteroids (1580) Betulia, (1627) Ivar, (1980) Tezcatlipoca, (2100) Ra-Shalom, (3199) Nefertiti, (3908) Nyx, (4957) Brucemurray, and (5587) 1990 SB. We also outline some of their solar phase curves, corrected to common reference geometry with the models. Some of the targets may feature sizable global nonconvexities, but the observable solar phase angles were not sufficiently high for confirming these. None is likely to have a very densely cratered surface. We discuss the role of the intermediate topographic scale range in photometry, and surmise that this scale range is less important than large or small scale lengths. 相似文献
93.
Irina V. Petrovskaya 《Celestial Mechanics and Dynamical Astronomy》1992,54(1-3):267-269
The evolution of the velocity distribution function of a group of zero mass bodies in the gravitational field of a stellar cluster or a galactic disk is considered. We use the model of a purely discontinuous random process. 相似文献
94.
Ionospheric electron density observed by FORMOSAT-3/COSMIC over the European region and validated by ionosonde data 总被引:4,自引:0,他引:4
Andrzej Krankowski Irina Zakharenkova Anna Krypiak-Gregorczyk Irk I. Shagimuratov Pawel Wielgosz 《Journal of Geodesy》2011,85(12):949-964
This research is motivated by the recent IGS Ionosphere Working Group recommendation issued at the IGS 2010 Workshop held
in Newcastle, UK. This recommendation encourages studies on the evaluation of the application of COSMIC radio occultation
profiles for additional IGS global ionosphere map (GIM) validation. This is because the reliability of GIMs is crucial to
many geodetic applications. On the other hand, radio occultation using GPS signals has been proven to be a promising technique
to retrieve accurate profiles of the ionospheric electron density with high vertical resolution on a global scale. However,
systematic validation work is still needed before using this powerful technique for sounding the ionosphere on a routine basis.
In this paper, we analyze the properties of the ionospheric electron density profiling retrieved from COSMIC radio occultation
measurements. A comparison of radio occultation data with ground-based measurements indicates that COSMIC profiles are usually
in good agreement with ionosonde profiles, both in the F2 layer peak electron density and the bottom side of the profiles.
For this comparison, ionograms recorded by European ionospheric stations (DIAS network) in 2008 were used. 相似文献
95.
A gridded monthly precipitable water (PW) data for 1979?C2007 from the NCEP/NCAR reanalysis are used to investigate summertime interannual PW variability over Europe and its relation to the key climate parameters in the region. During summer season the first EOF mode of PW, explaining 27?C41% of its total variance, demonstrates significant month-to-month changes in its structure, thus, implying its essential non-stationarity. The second EOF mode of PW is also non-stationary during the summer season. In contrast to precipitation, both leading modes of PW are not associated with the North Atlantic Oscillation (NAO), as well as with other regional teleconnections, suggesting relatively minor role of the atmospheric dynamics in atmospheric moisture variability over Europe during summer season. Analysis of links between leading EOF modes of regional PW and air temperature (AT) has revealed a strong link between PW and AT over Europe, persisting during entire summer season. Locally, these links imply that positive (negative) AT anomalies result in enhanced (decreased) PW over particular region. Revealed links between leading modes of PW and AT highlight important role of thermodynamics in summertime PW variability over Europe. Detected relatively weak and unstable links between leading modes of PW and precipitation over Europe were somewhat expected since in contrast to atmospheric moisture, regional precipitation variability is largely driven by the atmospheric dynamics (particularly, the NAO). 相似文献
96.
Using Mg Isotopes to Trace Cyanobacterially Mediated Magnesium Carbonate Precipitation in Alkaline Lakes 总被引:1,自引:0,他引:1
Liudmila S. Shirokova Vasileios Mavromatis Irina A. Bundeleva Oleg S. Pokrovsky Pascale B��n��zeth Emmanuelle G��rard Christopher R. Pearce Eric H. Oelkers 《Aquatic Geochemistry》2013,19(1):1-24
This study assesses the potential use of Mg isotopes to trace Mg carbonate precipitation in natural waters. Salda Lake (SW Turkey) was chosen for this study because it is one of the few modern environments where hydrous Mg carbonates are the dominant precipitating minerals. Stromatolites, consisting mainly of hydromagnesite, are abundant in this lake. The Mg isotope composition of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments were measured. Because Salda Lake is located in a closed basin, mass balance requires that the Mg isotopic offset between Lake Salda water and precipitated hydromagnesite be comparable to the corresponding offset between Salda Lake and its water inputs. This is consistent with observations; a ??26Mg offset of 0.8?C1.4??? is observed between Salda Lake water and it is the incoming streams and groundwaters, and precipitated hydromagnesite has a ??26Mg 0.9?C1.1??? more negative than its corresponding fluid phase. This isotopic offset also matches closely that measured in the laboratory during both biotic and abiotic hydrous Mg carbonate precipitation by cyanobacteria (Mavromatis, V., Pearce, C., Shirokova, L. S., Bundeleva, I. A., Pokrovsky, O. S., Benezeth, P. and Oelkers, E.H.: Magnesium isotope fractionation during inorganic and cyanobacteria-induced hydrous magnesium carbonate precipitation, Geochim. Cosmochim. Acta, 2012a. 76, 161?C174). Batch reactor experiments performed in the presence of Salda Lake cyanobacteria and stromatolites resulted in the precipitation of dypingite (Mg5(CO3)4(OH)2·5(H2O)) and hydromagnesite (Mg5(CO3)4(OH)2·4H2O) with morphological features similar to those of natural samples. Concurrent abiotic control experiments did not exhibit carbonate precipitation demonstrating the critical role of cyanobacteria in the precipitation process. 相似文献
97.
Abstract The paper presents a GIS model for mapping soils in the semi arid region of Israel. The model is based on a priori knowledge of the soil generating factors in the study area, namely (1) the parent‐material (lithology) which determines the origin of the soil; and (2) the relief (including the drainage patents) which is responsible for erosion, deposition, and leaching processes along the catena. A special attempt was made to represent soil belts in small subwatersheds with different parent‐material. The width of these belts can be varied as a function of the local relief. We believe that GIS techniques, in contrast to conventional survey and mapping methods, have the potential to overcome the manpower and fiscal restrictions which limit monitoring of large areas and areas which are for different reasons difficult to access. However, systematically generalizing a spatial model for a large area may introduce some errors, either due to local variations which were not taken into account, or regional variations. 相似文献
98.
Dmitri V. Alexandrov Irina A. Bashkirtseva Alexey P. Malygin Lev B. Ryashko 《Pure and Applied Geophysics》2013,170(12):2273-2282
The influence of stochastic fluctuations in the atmosphere and in the ocean caused by different occasional phenomena (noises) on dynamic processes of sea ice growth with a mushy layer is studied. It is shown that atmospheric temperature variances substantially increase the sea ice thickness, whereas dispersion variations of turbulent flows in the ocean to a great extent decrease the ice content produced by false bottom evolution. 相似文献
99.
The spectroscopic observations of comet C/2009 R1 (McNaught) were carried out with the 2 m Zeiss-RCC Telescope of Pik Terskol Observatory operated by the International Center for Astronomical and Medico-Ecological Research (Ukraine, Russia). The Multi Mode Cassegrain spectrometer was used to obtain spectra of moderate spectral resolving power with a wavelength coverage from 4140 to 5240 Å. The spectrum is characterized by the extremely low continuum level and strong molecular features. 192 emission lines of C2, CN, CH, NH2, CO+, and CH+ have been identified by the comparison of the observed and theoretical spectra of the molecules. The ratios of the gas production rates of Q(C2)/Q(CN)=1.32, Q(CH)/Q(CN)=0.49, and Q(NH2)/Q(CN)=0.81 were derived using a Haser model. 相似文献
100.
Fernando Unrein Inés O’Farrell Irina Izaguirre Rodrigo Sinistro María dos Santos Afonso Guillermo Tell 《Aquatic Sciences - Research Across Boundaries》2010,72(2):179-190
Phosphorus has been traditionally regarded as the controlling nutrient for phytoplankton growth, however, N-limitation is
likely to occur in several environments. For example, nitrogen is considered the main nutrient limiting phytoplankton in floodplain
lakes of the Paraná River basin. However, N2-fixing heterocystous cyanobacteria (N2-cyano) are usually absent in these water bodies. The low pH values frequently found may limit the development of these algae.
We hypothesise that long-term lake isolation allows conspicuous phytoplankton growth during summer, resulting in high photosynthetic
rates and pH. This scenario combined with low DIN (dissolved inorganic nitrogen) would favour the development of N2-cyano. Phytoplankton composition was studied during 16 months in a vegetated and isolated floodplain lake in the Paraná basin.
Additionally, pH was artificially increased in in situ mesocosms to test effects on phytoplankton structure. Lake phytoplankton
was dominated by flagellates (cryptophytes and euglenophytes) and small coccoid algae (chlorophytes and colonial cyanobacteria).
Algal biomass was highest during warm periods. Although pH increased up to 8.8 during the second summer period, N2-cyano remained rare, most likely because of the high DIN concentration recorded. The alkalophilic diatom Cyclotella meneghiniana dominated and was positively correlated with pH. Conversely, PO4= concentrations in the mesocosm experiment were high and DIN remained relatively low. pH enhancement in the treated mesocosms
(avg. pH = 8.2) promoted the development of N2-cyano (Anabaena spp.) and C. meneghiniana, which after 1 month of incubation accounted together for 50% of the biomass in contrast to less than 1.6% in control containers.
Our results support the hypothesis that during the warm season and under low DIN concentration, high pH favours N2-cyano growth in these lakes. We provide new evidence supporting the idea that even under optimal nutrient conditions, N2-cyano do not thrive unless other requirements are satisfied. 相似文献