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41.
The atmospheric transmission window at 2.7 μm in Jupiter's atmosphere was observed at a spectral resolution of 0.1 cm?1 from the Kuiper Airborne Observatory. From analysis of the CH4 abundance (~80m-am) and the H2O abundance (<0.0125cm-am) it was determined that the penetration depth of solar flux at 2.7 μm is near the base of the NH3 cloud layer. The upper limit to H2O at 2.7 μm and other recent results suggest that photolytic reactions in Jupiter's lower troposphere may not be as significant as was previously thought. The search for H2S in Jupiter's atmosphere yielded an upper limit of ~0.1cm-am. The corresponding limit to the elemental abundance ratio [S]/[H] was ~1.7 × 10?8, about 10?3 times the solar value. Upon modeling the abundance and distribution of H2S in Jupiter's atmosphere it was concluded that, contrary to expectations, sulfur-bearing chromophores are not present in significant amounts in Jupiter's visible clouds. Rather, it appears that most of Jupiter's sulfur is locked up as NH4SH in a lower cloud layer. Alternatively, the global abundance of sulfur in Jupiter may be significantly depleted. 相似文献
42.
Manuel?KeithEmail author Karsten?M.?Haase Reiner?Klemd Daniel?J.?Smith Ulrich?Schwarz-Schampera Wolfgang?Bach 《Contributions to Mineralogy and Petrology》2018,173(5):40
Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L’Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu?>?2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe–Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal–porphyry deposits. 相似文献
43.
Vasileios?MavromatisEmail author Reiner?Botz Mark?Schmidt Volker?Liebetrau Christian?Hensen 《International Journal of Earth Sciences》2014,103(7):1831-1844
The surface sediments of two mud mounds (“Mound 11” and “Mound 12”) offshore southwest Costa Rica contain abundant authigenic carbonate concretions dominated by high-Mg calcite (14–20 mol-% MgCO3). Pore fluid geochemical profiles (sulfate, sulfide, methane, alkalinity, Ca and Mg) indicate recent carbonate precipitation within the zone of anaerobic oxidation of methane (AOM) at variable depths. The current location of the authigenic carbonate concretions is, however, not related to the present location of the AOM zone, suggesting mineral precipitation under past geochemical conditions as well as changes in the flow rates of upward migrating fluids. Stable oxygen and carbon isotope analysis of authigenic carbonate concretions yielded δ18Ocarbonate values ranging between 34.0 and 37.7 ‰ Vienna standard mean ocean water (VSMOW) and δ13Ccarbonate values from ?52.2 to ?14.2 ‰ Vienna Pee Dee belemnite (VPDB). Assuming that no temperature changes occurred during mineral formation, the authigenic carbonate concretions have been formed at in situ temperature of 4–5 °C. The δ18Ocarbonate values suggest mineral formation from seawater-derived pore fluid (δ18Oporefluid = 0 ‰ VSMOW) for Mound 12 carbonate concretions but also the presence of an emanating diagenetic fluid (δ18Oporefluid ≈5 ‰) in Mound 11. A positive correlation between δ13Ccarbonate and δ18Ocarbonate is observed, indicating the admixing of two different sources of dissolved carbon and oxygen in the sediments of the two mounds. The carbon of these sources are (1) marine bicarbonate (δ13Cporefluid ≈0 ‰) and (2) bicarbonate which formed during the AOM (δ13Cporefluid ≈?70 ‰). Furthermore, the δ18Oporefluid composition, with values up to +4.7 ‰ Vienna standard mean ocean water (VSMOW), is interpreted to be affected by the presence of emanating, freshened and boron-enriched fluids. Earlier, it has been shown that the origin of 18O-enriched fluids are deep diagenetic processes as it was indicated by the presence of methane with thermogenic signature (δ13CCH4 = ?38 ‰). A combination of present geochemical data with geophysical observations indicates that Mounds 11 and 12 represent a single fluid system interconnected by deep-seated fault(s). 相似文献
44.
本实验旨在研究稻田土壤中甲烷产生率对稻田CH_4排放的影响.观测结果表明:土壤各深度的甲烷产生率有很大的变化范围(1—4639ng·h~(-1)·g~(-1)d.w.).主要的甲烷产生区域是7—17cm深的土壤层,其中以13cm深的土壤层上的生成速率最大.土壤中甲烷产生率与稻田CH_4排放率在水稻生长的某些阶段有较好的相关性,但它的季节变化却不能与排放的季节变化完全耦合.在水稻生长期,土壤中甲烷产生率随时间而增大,并在8月份水稻收割前达到最大,其日平均值在38—767 ng·h~(-1)·g~(-1)d.w.间变动.稻田土壤中甲烷产生率也存在日变化,一般在下午达到最大值,但却没有发现它与土壤温度有明显的相关关系.在不同施肥及水稻品种的稻田土壤中也观测到不同的甲烷产生率.在土壤中产生的甲烷最多只有28.8%被排放到大气中,而其余多于71.2%的则被氧化在土壤中. 相似文献
45.
It is necessary to understand the presence, movement, and persistence of contaminants in aquifers to develop adequate groundwater protection plans. Fractured bedrock aquifers with thin overburden cover are very sensitive to contamination, and little is known about transport processes from the ground surface to depth in this setting. This study was undertaken to investigate the potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs), which are flame retardants, in a natural fractured bedrock aquifer in Canada proven to be sensitive to contamination. PBDEs, which had not been previously measured in groundwater in detail, were detected in the study aquifer at concentrations greater than those observed in surface-water bodies. Potential sources include manure, septic tanks, and the atmosphere. From this scoping study, it is evident that additional surveys of PBDE concentrations in groundwater are warranted, especially in settings with high potential source concentrations coupled with sensitive aquifers. 相似文献
46.
Reiner Rummel 《Marine Geodesy》2013,36(3):219-220
Concern over the impact of change in sea level is of topical interest internationally, but for the small island states of the Caribbean, a significant increase would prove to be catastrophic. The potential problem is being addressed as part of the much larger issue of climate change, and just this year a regional Climate Change Centre was established in Belize. Means of adapting to accommodate change will be considered under the Mainstream Adaptation to Climate Change (MACC) project, but initially the threat needs to be quantified. While meteorological offices have been accumulating weather data in some parts of the region for many years, sea level data is more scarce. This work puts least squares methods to test by applying them to spectral analysis of intermittent data sets acquired over periods of 6 and 9 years at two locations in Trinidad. The resulting sea level models that include 13 periodic components, datum bias, trend and atmospheric pressure are validated using fundamental historical information and observations that form the subject of discussion among local professional surveyors. Results show that while sea level at a location in North Trinidad is rising at the rate of about 1 mm a year, the change at a Southern site is about four times this amount. Horizontal movement has been measured across a tectonic fault that parts the island, and it is now apparent that there may be some vertical motion on this or some other fault lines in the region. 相似文献
47.
Stefan Stoll Wolfgang Nikolaus Probst Reiner Eckmann Philipp Fischer 《Aquatic Sciences - Research Across Boundaries》2010,72(4):509-517
In a mesocosm experiment, the attachment of bream (Abramis brama) eggs to spawning substrata with and without periphytic biofilm coverage and their subsequent survival with and without low-intensity
wave exposure were investigated. Egg attachment was reduced by 73% on spawning substrata with a natural periphytic biofilm,
compared to clean substrata. Overall, this initial difference in egg numbers persisted until hatching. The difference in egg
numbers was even increased in the wave treatment, while it was reduced in the no-wave control treatment. Exposure to a low-intensity
wave regime affected egg development between the two biofilm treatments differently. Waves enhanced egg survival on substrata
without a biofilm but reduced the survival of eggs on substrata with biofilm coverage. In the treatment combining biofilm-covered
substrata and waves, no attached eggs survived until hatching. In all treatments, more than 75% of the eggs became detached
from the spawning substrata during the egg incubation period, and <1% of these detached eggs survived within the substratum
interstices. Hence, detached eggs contributed little to the reproductive success we observed. The implications of these results
on the spawning success of fish species that use freshly inundated spawning substrata in shallow waters are discussed. 相似文献
48.
Small tectonic slices of undeformed eclogites and ultrahigh-pressure granulites occur in three tectonic units of the Śnieżnik
Mts. (SW Poland). Ultrahigh-pressure granulite/eclogite transitions with peak metamorphic conditions between 21 and 28 kbar
at 800 to 1000 °C occur only in the Złote unit. Conventional U-Pb multigrain analyses of zircons from a mafic granulite provided
207Pb/206Pb ages between 360 to 369 Ma which are interpreted to approximate timing of original crystallisation from a melt. Diffusion
kinetics and the restricted availability of a fluid phase mainly controlled the conversion from granulite to eclogite, although
some bulk-chemical differences were also recognised. The ultrahigh-pressure granulites from the Złote unit exclusively contain
H2O-rich inclusions with variable salinities which distinguishes them from high-temperature (HT)-granulites world-wide. This is also in contrast to the fluid regime (H2O-N2-CO2) recognised in the lower-temperature eclogites (600–800 °C) from the closely associated Międzygórze and Śnieżnik units. The
variation in fluid composition between the lower-temperature eclogites and ultrahigh-pressure granulites on the one hand and
ultrahigh-pressure granulites and HT-granulites on the other hand probably indicates contrasting P-T-t paths as a result of different tectonic environments.
Received: 15 June 1998 / Accepted: 2 March 1999 相似文献
49.
Reiner Klemd Siegfried Matthes Martin Okrusch 《Contributions to Mineralogy and Petrology》1991,107(3):328-342
The mineral assemblages in the eclogites and meta-sediments of the Münchberg gneiss complex suggest minimum pressures of about 15 kbar, and temperatures of 600±30° C for the eclogite-facies metamorphism. Both rock types underwent a subsequent amphibolite-facies metamorphism at almost the same temperature range. In the Weissenstein borehole the eclogites and meta-sediments show an intimate interlayering on a centimetre scale. Contacts between the two rock types are often sharp and untectonized suggesting in-situ metamorphism of the eclogites. The following features indicate that the gneisses were subjected to eclogite-facies metamorphism:
- Phengite relics and phengite inclusions in garnet contain up to 3.45 Si per formula unit while amphibolite facies phengites have considerably lower Si-contents (3.0–3.25 p.f.u.).
- Omphacite relics occur in the form of Na-augite (6–9 mol% jadeite)-oligoclase symplectites.
- Garnets with up to 40 mol% of the pyrope component occur.
50.