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331.
Marine trace fossils were investigated in a 102-m cored section that covers −14.379 to −14.142 Ma (Middle Miocene). Long-term climate trends are perfectly reflected by changing trace fossil communities of the upper bathyal (−200 to −300 m). The community structure is expressed in abundance of taxa based on probabilities of time concordance between the deposition of the sediment and the time, when the traces were produced. Changes in community structure precisely parallel the increasing δ13 C isotopes during the Middle Miocene climate transition and perfectly mirror oscillations in solar insolation in both amplitudes and phase. Furthermore, the density stratification of the seawater caused by wind-induced currents is reflected in trace fossil communities. Additionally, the dependence of ichnotaxa abundance from threshold values in the sedimentation rate could be demonstrated. 相似文献
332.
Doug W. Johnson Simon Osborne Robert Wood Karsten Suhre Randy Johnson Steven Businger Patricia K. Quinn Alfred Wiedensohler Philip A. Durkee Lynn M. Russell Meinrat O. Andreae Colin O'Dowd Kevin J. Noone Brian Bandy J. Rudolph Spyros Rapsomanikis 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):290-320
333.
Structure and State of Stress of the Chilean Subduction Zone from Terrestrial and Satellite-Derived Gravity and Gravity Gradient Data 总被引:1,自引:1,他引:0
B. D. Gutknecht H.-J. Götze T. Jahr G. Jentzsch R. Mahatsente St. Zeumann 《Surveys in Geophysics》2014,35(6):1417-1440
It is well known that the quality of gravity modelling of the Earth’s lithosphere is heavily dependent on the limited number of available terrestrial gravity data. More recently, however, interest has grown within the geoscientific community to utilise the homogeneously measured satellite gravity and gravity gradient data for lithospheric scale modelling. Here, we present an interdisciplinary approach to determine the state of stress and rate of deformation in the Central Andean subduction system. We employed gravity data from terrestrial, satellite-based and combined sources using multiple methods to constrain stress, strain and gravitational potential energy (GPE). Well-constrained 3D density models, which were partly optimised using the combined regional gravity model IMOSAGA01C (Hosse et al. in Surv Geophys, 2014, this issue), were used as bases for the computation of stress anomalies on the top of the subducting oceanic Nazca plate and GPE relative to the base of the lithosphere. The geometries and physical parameters of the 3D density models were used for the computation of stresses and uplift rates in the dynamic modelling. The stress distributions, as derived from the static and dynamic modelling, reveal distinct positive anomalies of up to 80 MPa along the coastal Jurassic batholith belt. The anomalies correlate well with major seismicity in the shallow parts of the subduction system. Moreover, the pattern of stress distributions in the Andean convergent zone varies both along the north–south and west–east directions, suggesting that the continental fore-arc is highly segmented. Estimates of GPE show that the high Central Andes might be in a state of horizontal deviatoric tension. Models of gravity gradients from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission were used to compute Bouguer-like gradient anomalies at 8 km above sea level. The analysis suggests that data from GOCE add significant value to the interpretation of lithospheric structures, given that the appropriate topographic correction is applied. 相似文献
334.
335.
336.
The radiative damping of trapped gravity waves in an optically thin atmosphere is studied for a stratified Boussinesq fluid. The character of the atmospheric eigenmodes depends on the distribution of the Brunt-Väisälä frequency N and the radiative relaxation time . The calculations for simple layer models show that if N is large over some finite fraction of the trapping region, then modes of long lifetime can exist. In order to suppress gravity waves entirely, it is necessary that N < 1 over the entire trapping region. Qualitative application of the results to the solar atmosphere leads to the conclusion that gravity wave eigenmodes of the solar atmosphere, although damped, are by no means eliminated by radiative effects. 相似文献
337.
338.
Alfred Grund 《Mineralogy and Petrology》1955,5(3):227-230
Zusammenfassung BeSO4 kristallisiert im BPO4-Typ, der sich von der Cristobalitstruktur herleitet. a=4·49 A, c=6·90 A, c/a=1·536. Die Atomabstände sind: S–O=1·50 A, Be–O=1·56 A. 相似文献
339.
K. F.?TiampoEmail author J.?Fernández G.?Jentzsch M.?Charco J. B.?Rundle 《Pure and Applied Geophysics》2004,161(7):1433-1452
In this paper, we detail the combination of the genetic algorithm (GA) inversion technique with the elastic-gravitational model originally developed by Rundle and subsequently refined by Fernández and others. A sensitivity analysis is performed for the joint inversion of deformation and gravity to each of the model parameters, illustrating the importance of proper identification of both the strengths and limitations of any source model inversion, and this technique in particular. There is a practical comparison of the theoretical results with the inversion of geodetic data observed at the Mayon volcano in the Philippines, where there are gravity changes without significant deformation, after the 1993 eruption. 相似文献
340.
Marianna?PastuszakEmail author Klaus?Nagel Alfred?Grelowski Volker?Mohrholz Mariusz?Zalewski 《Estuaries and Coasts》2003,26(5):1238-1254
The Pomeranian Bay is a coastal region fed by the Oder River, one of the seven largest Baltic rivers, whose waters flow through
a large and complex estuarine system before entering the bay. Nutrients (NO3
−, NO2
−, NH4
+, Ntot, PO4
3−, Ptot, DSi), chlorophylla concentrations, oxygen content, salinity, and temperature were measured in the Pomeranian Bay in nine seasonally distributed
cruises during 1993–1997. Strong spatial and temporal patterns were observed and they were governed by: the seasonally variable
riverine water-nutrient discharges, the seasonally variable uptake of nutrients and their cycling in the river estuary and
the Bay, the character of water exchange between the Pomeranian Bay and the Szczecin Lagoon, and the water flow patterns in
the Bay that are dominated by wind-driven circulation. Easterly winds resulted in water and nutrient transport along the German
coastline, while westerly winds confined the nutrient rich riverine waters to the Polish coast and transported them eastward
beyond the study area. Two water masses, coastal and open, characterized by different chemical and physical parameters and
chla content were found in the Bay independently of the season. The role of the Oder estuary in nutrient transformation, as well
as the role of temperature in transformation processes is stressed in the paper. The DIN:DIP:DSi ratio indicated that phosphorus
most probably played a limiting role in phytoplankton production in the Bay in spring, while nitrogen did the same in summer.
During the spring bloom, predominated by diatoms, the DSi:DIN ratio dropped to 0.1 in the coastal waters and to 0.6 in the
open bay waters, pointing to silicon limitation of diatom growth, similar to what is being observed in other Baltic regions. 相似文献