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排序方式: 共有139条查询结果,搜索用时 281 毫秒
41.
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
42.
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
43.
The drivers of Chinese CO2 emissions from 1980 to 2030 总被引:4,自引:0,他引:4
Dabo Guan Klaus Hubacek Christopher L. Weber Glen P. Peters David M. Reiner 《Global Environmental Change》2008,18(4):626
China's energy consumption doubled within the first 25 years of economic reforms initiated at the end of the 1970s, and doubled again in the past 5 years. It has resulted of a threefold CO2 emissions increase since early of 1980s. China's heavy reliance on coal will make it the largest emitter of CO2 in the world. By combining structural decomposition and input–output analysis we seek to assess the driving forces of China's CO2 emissions from 1980 to 2030. In our reference scenario, production-related CO2 emissions will increase another three times by 2030. Household consumption, capital investment and growth in exports will largely drive the increase in CO2 emissions. Efficiency gains will be partially offset the projected increases in consumption, but our scenarios show that this will not be sufficient if China's consumption patterns converge to current US levels. Relying on efficiency improvements alone will not stabilize China's future emissions. Our scenarios show that even extremely optimistic assumptions of widespread installation of carbon dioxide capture and storage will only slow the increase in CO2 emissions. 相似文献
44.
Reiner GOGUEL 《Geostandards and Geoanalytical Research》1983,7(2):341-344
Cadmium signals obtained by direct aspiration of highly concentrated solutions of rocks and other geochemical samples are swamped by strong matrix background signals. Mainly because of iron interference, the deuterium source or other continua are not satisfactory for background correction. In order to isolate atomic absorption by cadmium the total signal and the background signal have to be measured precisely. Sequential measurements in the double beam mode with electrodeless discharge lamps of cadmium and arsenic at 228.80 and 228.81 nm produced a set of uninterfered data for cadmium within marginally useful detection limits of (0.10 ppm in granite, 0.16 ppm Cd in limestone). Simple extraction of the sample powders with nitric acid dissolves only part of the sample matrix but most of the cadmium. In this way higher relative and absolute cadmium concentrations in solution and better detection limits are obtained (e.g. 0.02 ppm Cd in granite). This approach allows cadmium in geosamples at levels below 0.3 ppm to be determined more accurately than via hydrofluoric acid dissolution. 相似文献
45.
The Larafella Au-prospect (Burkina Faso) lies within dacitic rocks of the Palaeoproterozoic Birimian greenstone belts. Gold mineralization is intimately associated with zones of cataclastic deformation. Whilst the lode-vein mineralization is closely associated with CO2-rich fluid inclusions, the barren quartz veins are characterized by H2O ± salt-bearing inclusions. Geochemical studies on the immediate wall-rock of the quartz veins have shown an increase of As in zones of gold enrichment, while alteration overprints such as carbonatization and chloritization cannot be correlated unequivocally with Au-mineralization. Consequently, fluid inclusion studies of quartz veins and As-anomalies constitute important exploration tools for mesothermal gold mineralization, since Au-rich zones can be distinguished from Au-depleted zones. 相似文献
46.
Mobilization of Ti-Nb-Ta during subduction: Evidence from rutile-bearing dehydration segregations and veins hosted in eclogite, Tianshan, NW China 总被引:15,自引:0,他引:15
Field evidence from the western Tianshan subduction complex in northwestern China indicates that the high field strength elements Ti, Nb, and Ta were mobilized and thereby fractionated from Zr and Hf during the dehydration process that transformed blueschist into eclogite. Both a segregation with a depletion halo, thought to represent initial mobilization during dehydration, and a transport vein, indicative of the long distance transport were investigated. In each case, centimeter-sized rutile grains grew as needle-like crystals in the segregation and as prismatic crystals in the vein. Within the host rock of the segregation, the Ti contents of garnet and omphacite, the modal abundances of rutile and titanite and the bulk rock Ti, Nb, and Ta contents decrease towards the segregation. These observations are consistent with transport of Ti, Nb, and Ta from the host rock into the segregation. Textural and geochemical data for the eclogite-facies vein minerals indicate that Ti-Nb-Ta-rich fluids were transported over long-distances (at minimum meter-scale) during fracture-controlled fluid flow. Complex forming ligands (e.g., Na-Si-Al polymers and F−) may have enhanced the solubility of Ti, Nb, and Ta in the fluid. Changes in fluid composition (e.g., XCO2) may both precipitate rutile and fractionate Ti, Nb, and Ta from LILE and REE. 相似文献
47.
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.
48.
49.
Richard A. Feely Christopher L. Sabine Reiner Schlitzer John L. Bullister Sabine Mecking Dana Greeley 《Journal of Oceanography》2004,60(1):45-52
As a part of the JGOFS synthesis and modeling project, researchers have been working to synthesize the WOCE/JGOFS/DOE/NOAA
global CO2 survey data to better understand carbon cycling processes in the oceans. Working with international investigators we have
compiled a Pacific Ocean data set with over 35,000 unique samples analyzed for at least two carbon species, oxygen, nutrients,
chlorofluorocarbon (CFC) tracers, and hydrographic parameters. We use these data here to estimate in-situ oxygen utilization
rates (OUR) and organic carbon remineralization rates within the upper water column of the Pacific Ocean. OURs are derived
from the observed apparent oxygen utilization (AOU) and the water age estimates based on CFCs in the upper water and natural
radiocarbon in deep waters. The rates are generally highest just below the euphotic zone and decrease with depth to values
that are much lower and nearly constant in water deeper than 1200 m. OURs ranged from about 0.02–10 μmol kg−1yr−1 in the upper water masses from about 100–1000 m, and averaged = 0.10 μmol kg−1yr−1 in deep waters below 1200 m. The OUR data can be used to directly estimate organic carbon remineralization rates using the
C:O Redfield ratio given in Anderson and Sarmiento (1994). When these rates are integrated we obtain an estimate of 5.3 ±
1 Pg C yr−1 for the remineralization of organic carbon in the upper water column of the Pacific Ocean.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.