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91.
Wilhelm Schottler 《International Journal of Earth Sciences》1931,22(3-4):161-168
Ohne Zusammenfassung 相似文献
92.
San.-Rat Dr. Wilhelm Pfannkuch 《International Journal of Earth Sciences》1913,4(5-6):311-318
Ohne Zusammenfassung 相似文献
93.
E. J. Wilhelm 《The Professional geographer》1968,20(2):123-125
94.
Wilhelm Salomon 《International Journal of Earth Sciences》1916,6(7-8):398-404
Ohne Zusammenfassung 相似文献
95.
96.
97.
Alik Ismail-Zadeh Helmut Wilhelm Yuri Volozh 《International Journal of Earth Sciences》2008,97(5):1029-1043
The Astrakhan Arch region contains one of the largest sub-salt structures of the Pricaspian basin, where perspectives for
hydrocarbon generation and accumulation in the Devonian to Carboniferous deposits are considered to be high. The paper addresses
the problem of structural and geothermal evolution of the region deformed by salt movements. Initially, we developed a model
of the regional structural evolution along a geological profile using the volume-balancing and back-stripping methods and
geological constraints on the sedimentation, erosion, and paleo-water depths. Then we developed geothermal models (along the
study profile) associated with the regional structural evolution. The models were constrained by the temperatures measured
in four deep boreholes along the profile. We show that the present temperatures and heat flux are influenced by the presence
of salt diapirs. Since the Early Carboniferous and till Middle Permian times, the temperatures predicted by the models vary
significantly due to the regional transgression and the presence of seawater. The temperature of Devonian–Carboniferous carbonates
increases since the Late Permian (time of post-salt deposition) and attains its maximum values in the SW-part of the profile.
If the model assumptions concerning the constant vertical and zero lateral heat fluxes are valid, we can conclude that hydrocarbons
are most likely to be generated in the SW-part of the region for the post-Early Permian time. 相似文献
98.
Cyanobacteria are ubiquitous in marine waters. These prokaryotic cells are of particular interest in areas of the ocean where the availability of iron may be limiting for cell growth since these organisms commonly excrete iron-specific organic ligands (siderophores) in response to low levels of iron. It is generally considered that the production of siderophores provides a competitive advantage over the competing microorganisms that do not produce these ligands.In order to ascertain the influence of iron availability on the physiology of picoplanktonic cyanobacteria we performed a series of experiments on the coastal coccoid cyanobacterium, Synechococcus sp. PCC 7002. Physiological responses were examined in cells grown in a continuous cuture system with influx media containing a range of iron concentrations (from 4.2 × 10−5 to 5.1 × 10−9 M FeCl3). Steady-state growth rates, combined with growth data from batch cultures demonstrated a non-linear response between iron availability and cell proliferation: cell yields were considerably higher in the lowest-iron chemostats than predicted based on the yields in the higher-iron chemostats. The higher yields during low-iron growth corresponded with the production of the extracellular siderophores and the induction of the specific iron-siderophore membrane transport proteins. A comparison of iron transport and carbon acquisition rates between the low-iron grown cells and the high-iron grown cells indicates that under low-iron growth conditions, iron and carbon acquisition meets the growth demands of the cells, whereas growth at higher iron levels enabled excessive (luxury) carbon acquisition and storage. We conclude that cyanobacteria are efficiently adapted to grow in low-iron environments (providing sufficient light for photosynthesis is available) and the luxury-uptake of carbon may serve as the source material for the extracellular ligands released by these cells. Since the release of siderophores was at iron levels in excess of the levels that induce the siderophore-mediated transport of iron, cyanobacteria growing in an environment with varying levels of iron may contribute substantial amounts of their stored carbon reserves into the DOC as iron-specific ligands. 相似文献
99.
Jurassic Ferrar rocks in Victoria Land (Antarctica) occur predominantly as basaltic or andesitic flows and sills. Both show
characteristic petrographical and chemical variations, which can be related to in-situ differentiation processes. Such characteristics
have been investigated at one flow (“Colonnade flow”) and one sill (“Thumb Point sill”) in the Prince Albert Mountains (Central
Victoria Land) based on a statistical grain size analysis and the application of the crystal size distribution theory. A third
magma body (“HiTi-unit”), which in previous literature was described as a flow, does not show clear similarities to either
the flow or sill. Sill and flow are in-situ differentiated with accumulation of silicic residual melt in the latest cooled
parts. For the flow this part is located in the lower half and for the sill in the upper third of their thickness. Thumb Point
sill additionally shows an accumulation zone of olivine in the lower third. The position of the residual melt accumulation
zone is an indicator for an origin as flow or sill. The HiTi-unit, by contrast, exhibits, only moderate petrographical and
chemical variations. Growth and nucleation rates have been determined using, with some modifications, the CSD theory introduced
by Marsh (1988). Growth rates of plagioclase for the flow vary from 10−11 to 10−10 cm/s and are comparable with literature values for basaltic lava lakes on Hawaii. Nucleation rates vary from 10−4 to 10−3 cm−3s−1, which are generally smaller than for Hawaiian basalts. Growth and nucleation rates for the sill cover a large range from
10−13 to 10−11 cm/s and 10−9 to 10−3 cm−3s−1, respectively. Systematic variations of these parameters with vertical position were obtained for the sill with its extensive
differentiation history. Nucleation and growth rates are dependant on the mode of cooling. Nevertheless, small but significant
differences between the flow and sill exist. Growth and nucleation rates of HiTi-unit (10−12 to 10−11 cm/s and 10−6 to 10−5 cm−3s−1) are intermediate between the flow and sill and thus do not allow a distinction of emplacement mode.
Received: 6 December 1995 / Accepted: 3 May 1996 相似文献
100.
Partial fusion of basic granulites at 5 to 15 kbar: implications for the origin of TTG magmas 总被引:24,自引:0,他引:24
Partial fusion experiments with basic granulites (S6, S37) believed to represent the lower crust beneath the Eifel region
(Germany) were performed at pressures from 5 to 15 kbar. Water-undersaturated experiments were carried out in the presence
of 1 wt% H2O plus 2.44 or 0.81 wt% CO2 equivalent to mole fractions of H2O/(H2O + CO2) of 0.5 and 0.75, respectively, of the volatile components added. At temperatures from 850 to 1100 °C the weight proportions
of melt range from 7 to 30 %. Melt compositions change from trondhjemitic over tonalitic to dioritic with increasing degree
of partial melting. Crystalline residua are plagioclase/pyroxene dominated at 5 kbar to garnet/pyroxene dominated at 15␣kbar.
Dehydration melting was studied in granulite S35 similar in composition to S6. The magmatic precursors of the granulite xenoliths
used in this study had geochemical characteristics of cumulate gabbro (metagabbro S37) and evolved melts (metabasalts S6,
S35), respectively. Melts from granulite S37 match the major element compositions of natural trondhjemites and tonalites.
At 5 kbar, their Al2O3 is relatively low, similar to tonalites from ophiolites. At 15 kbar, Al2O3 in the melts is high due to the near absence of plagioclase in the crystalline residua. The Al2O3 concentrations in 15 kbar melts from S6 (˜20 wt%) are higher than in natural tonalites. Depth constraints on the formation
of tonalitic magmas in the continental crust are provided by REE (rare earth element) patterns of the synthetic melts calculated
from the known REE abundances in metagabbro S37 and metabasalt S6 assuming batch melting and using partition coefficients
from the literature. The REE patterns of tonalites from active continental margins and Archean trondhjemite-tonalite-granodiorite␣associations
low in REE with LaN (chondrite normalised) from 10 to 30 and YbN from 1 to 2 are reproduced at pressures of 10 and 12.5 kbar from metagabbro S37 which displays a slightly L(light)REE enriched
pattern with LaN = 8 and YbN = 3. Natural tonalites with LaN from 30 to 100 require a source richer in REE than granulite S37. At 15 kbar, H(heavy)REEN in melts from granulite S37 are depressed below the level observed in natural tonalites due to the high proportion of garnet
(>30 wt%) in the residue. Melts from metabasalt S6 (enriched in REE with LaN = 38 and YbN = 16) do not match the REE characteristics of natural tonalites under any conditions.
Received: 1 July 1994 / Accepted: 11 September 1996 相似文献