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51.
Martin Cohen Jessica M. Chapman Rachel M. Deacon † Robert J. Sault Quentin A. Parker Anne J. Green 《Monthly notices of the Royal Astronomical Society》2006,369(1):189-196
We present radio observations of the unique, recently formed, planetary nebula (PN) associated with a very long-period OH/IR variable star V1018 Sco that is unequivocally still in its asymptotic giant branch phase. Two regions within the optical nebula are clearly detected in non-thermal radio continuum emission, with radio spectral indices comparable to those seen in colliding-wind Wolf–Rayet binaries. We suggest that these represent shocked interactions between the hot, fast stellar wind and the cold nebular shell that represents the PN's slow wind moving away from the central star. This same interface produces both synchrotron radio continuum and the optical PN emission. The fast wind is neither spherical in geometry nor aligned with any obvious optical or radio axis. We also report the detection of transient H2 O maser emission in this nebula. 相似文献
52.
Pirin Erdodu Ofer Lahav John P. Huchra † Matthew Colless Roc M. Cutri Emilio Falco † Teddy George Thomas Jarrett D. Heath Jones Lucas M. Macri Jeff Mader Nathalie Martimbeau Michael A. Pahre Quentin A. Parker Anaïs Rassat Will Saunders 《Monthly notices of the Royal Astronomical Society》2006,373(1):45-64
53.
Jinyuan Yan Bin Chen Selva Vennila Raju Budhiram K. Godwal Alastair A. MacDowell Jason Knight Hongwei Ma Quentin Williams 《Physics and Chemistry of Minerals》2012,39(4):269-275
The high-pressure behavior of HgO-montroydite was investigated up to 36.5 GPa using angle-dispersive X-ray diffraction. The
tetragonal phase of this material (HgO-II), a distortion of the NaCl structure, transforms into the cubic NaCl structure (HgO-III)
above ~31.5 GPa. The transformation of mercury oxide from the orthorhombic Pnma (HgO-I) structure to a tetragonal I4/mmm structure
(HgO-II) is confirmed to occur at 13.5 ± 1.5 GPa. Neither of the high-pressure phases, HgO-II nor HgO-III, is quenchable in
pressure. The derived isothermal bulk modulus of HgO-II and its pressure derivative strongly depend on the assumed zero-pressure
volume of this phase, but our elasticity results on HgO-II nevertheless lie significantly closer to theoretical calculations
than prior experimental results, and the measured pressure of the phase transformation to the NaCl structure is also in agreement
with recent theoretical results. The general accord with theory supports the existence of significant relativistic effects
on the high-pressure phase transitions of HgO. 相似文献
54.
55.
K.-E. Quentin 《洁净——土壤、空气、水》1988,16(4):385-396
Altogether 10… 20 kg/ha·a N from precipitation are introduced into the soil. The fertilization of the agriculturally used area increased from 50 to 120 kg/ha·a N between 1950 and 1982. The nitrogen concentration is theoretically increased by 0.4 mg/l due to infiltration of surface water and wastewaters. The data prove agriculture to the main source of the nitrate load of groundwater, especially in regions with predominantly intensive agricultural use there is delivered drinking water with nitrate concentrations of more than 50 mg/l. The fixing of the limit value for drinking water at 50 mg/l nitrate (value recommended by the EC: 25 mg/l) is justified by new findings. Since the technology of nitrate elimination from water is very expensive, mainly the preventing of too high nitrate concentrations should be aimed at by agricultural measures of ground-water protection. 相似文献
56.
Hong-Fei Zhang Randall Parrish Li Zhang Wang-Chun Xu Hong-Lin Yuan Shan Gao Quentin G. Crowley 《Lithos》2007,97(3-4):323-335
The Songpan–Garze fold belt covers a huge triangular area (> 200,000 km2), confined by the South China (Yangtze), North China and Tibetan Plateau continental blocks. In the Songpan–Garze fold belt, Triassic adakitic granitoids have been identified. However, whether there are Triassic A-type granites is unclear. Here, we report our first finding of an A-type granite (Nianbaoyeche), which occurs in the central part of the Songpan–Garze fold belt. The Nianbaoyeche granite ( 820 km2) is characterized by arfvedsonite in its mineral assemblage. Using both LA-ICPMS and TIMS U–Pb zircon dating methods, we obtain a magma crystallization age of 211 ± 1 Ma, which is slightly younger than Triassic adakitic granitoids (216–221 Ma) in the Songpan–Garze fold belt. The Nianbaoyeche granite is enriched in Si, K, Na, Rb, REE, HFSE (Nb, Ta, Zr, Hf), with elevated FeOtot/(FeOtot + MgO) and Ga/Al ratios, but is depleted in Al, Mg, Ca, Ba and Sr. The REE compositions show moderately fractionated patterns with (La/Yb)N = 2.67–7.54 and Eu/Eu = 0.09–0.34. These geochemical characteristics indicate that the Nianbaoyeche granite has an A-type affinity. Geochemical data and U–Pb zircon age, combined with regional studies, show that the Nianbaoyeche granite formed in a post-collisional tectonic setting. Sr–Nd isotopic data for the granite exhibit ISr = 0.7090–0.7123 and εNd(t) = − 2.72 to − 4.26 with TDM = 1.15–1.51 Ga, suggesting that the magma has a dominantly crustal source, though a minor contribution from the mantle cannot be ruled out. Melting to produce an A-type granite may have resulted from Triassic lithospheric delamination after Triassic crustal thickening of the Songpan–Garze fold belt due to convergence between the Yangtze, North China and North Tibet continental blocks. The lithospheric delamination model also helps to explain the Triassic adakitic magma generation in the Songpan–Garze belt. We conclude that association of A-type granite and adakitic granitoids in post-collisional environment could be a useful indicator of lithospheric delamination. 相似文献
57.
58.
This paper responds to the challenge of how and when to adapt marine capture fisheries to climate change by (1) providing a set of fisheries policy options to climate change; (2) developing a risk and vulnerability assessment and management decision-making framework for adaptation; and (3) describing the possible strategies and tactics for ex ante and ex post climate adaptation in the marine environment. Its contributions include (1) a discussion of how management objectives and instruments influence resilience and adaptation; (2) a decision-making process to assess vulnerabilities to climate change and to manage adaptation responses; (3) an inter-temporal framework to assist decision-makers on when to adapt; (4) a risk and simulation approach to confront the uncertainties of the possible losses due to climate change and the net benefits of adaptation; (5) an explanation of how adaptive co-management can promote flexible adaptation responses and also strengthen adaptation capacity; and (6) a selection of possible ‘win–win’ management actions. 相似文献
59.
Christian Vollmer Jan Leitner Demie Kepaptsoglou Quentin M. Ramasse Henner Busemann Peter Hoppe 《Meteoritics & planetary science》2020,55(6):1293-1319
Organic matter (OM) was widespread in the early solar nebula and might have played an important role for the delivery of prebiotic molecules to the early Earth. We investigated the textures, isotopic compositions, and functional chemistries of organic grains in the Renazzo carbonaceous chondrite by combined high spatial resolution techniques (electron microscopy–secondary ion mass spectrometry). Morphologies are complex on a submicrometer scale, and some organics exhibit a distinct texture with alternating layers of OM and minerals. These layered organics are also characterized by heterogeneous 15N isotopic abundances. Functional chemistry investigations of five focused ion beam‐extracted lamellae by electron energy loss spectroscopy reveal a chemical complexity on a nanometer scale. Grains show absorption at the C‐K edge at 285, 286.6, 287, and 288.6 eV due to polyaromatic hydrocarbons, different carbon‐oxygen, and aliphatic bonding environments with varying intensity. The nitrogen K‐edge functional chemistry of three grains is shown to be highly complex, and we see indications of amine (C‐NHx) or amide (CO‐NR2) chemistry as well as possible N‐heterocycles and nitro groups. We also performed low‐loss vibrational spectroscopy with high energy resolution and identified possible D‐ and G‐bands known from Raman spectroscopy and/or absorption from C=C and C‐O stretch modes known from infrared spectroscopy at around 0.17 and 0.2 eV energy loss. The observation of multiglobular layered organic aggregates, heterogeneous 15N‐anomalous compositions, and indication of NHx‐(amine) functional chemistry lends support to recent ideas that 15N‐enriched ammonia (NH3) was a powerful agent to synthesize more complex organics in aqueous asteroidal environments. 相似文献
60.
Abate Essi Jean Marcel Marcel Jean Diab Diab Ahmad Yene Atangana Joseph Quentin Abossolo Angue Monique Mvondo Ondoa Joseph 《Natural Resources Research》2020,29(1):473-497
Natural Resources Research - The north-central Cameroon is located at the northern edge of Archean Congo–Sao Francisco craton and at the east of the West African craton. This area includes... 相似文献