全文获取类型
收费全文 | 99篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 11篇 |
地球物理 | 19篇 |
地质学 | 38篇 |
海洋学 | 13篇 |
天文学 | 19篇 |
综合类 | 3篇 |
自然地理 | 3篇 |
出版年
2019年 | 2篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 9篇 |
2002年 | 9篇 |
2001年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有107条查询结果,搜索用时 125 毫秒
71.
LIU Yanguang OLE Bjφrslev Nielsen ZHANG Deyu DU Dewen JAN Heinemeier WU Yonghua 《海洋学报(英文版)》2006,25(1):78-89
1 Introduction Volcanic activities have played an important role in the process of global climatic changes. Being good stratigraphic markers, widespread tephra layers in ma- rine sediments can provide reliable evidences for the regional paleoceanographic … 相似文献
72.
The Weibull distribution is commonly used to describe climatological wind-speed distributions in the atmospheric boundary layer. While vertical profiles of mean wind speed in the atmospheric boundary layer have received significant attention, the variation of the shape of the wind distribution with height is less understood. Previously we derived a probabilistic model based on similarity theory for calculating the effects of stability and planetary boundary-layer depth upon long-term mean wind profiles. However, some applications (e.g. wind energy estimation) require the Weibull shape parameter (k), as well as mean wind speed. Towards the aim of improving predictions of the Weibull- \(k\) profile, we develop expressions for the profile of long-term variance of wind speed, including a method extending our probabilistic wind-profile theory; together these two profiles lead to a profile of Weibull-shape parameter. Further, an alternate model for the vertical profile of Weibull shape parameter is made, improving upon a basis set forth by Wieringa (Boundary-Layer Meteorol, 1989, Vol. 47, 85–110), and connecting with a newly-corrected corollary of the perturbed geostrophic-drag theory of Troen and Petersen (European Wind Atlas, 1989, Risø National Laboratory, Roskilde). Comparing the models for Weibull-k profiles, a new interpretation and explanation is given for the vertical variation of the shape of wind-speed distributions. Results of the modelling are shown for a number of sites, with a discussion of the models’ efficacy and applicability. The latter includes a comparative evaluation of Wieringa-type empirical models and perturbed-geostrophic forms with regard to surface-layer behaviour, as well as for heights where climatological wind-speed variability is not dominated by surface effects. 相似文献
73.
Alfonso Aragón-Salamanca Bo Milvang-Jensen George Hau Inger Jørgensen Jens Hjorth 《Astrophysics and Space Science》2002,281(1-2):339-342
We are carrying out a programme to measure the evolution of the stellar and dynamical masses and M/L ratios for a sizeable sample of morphologically-classified disk galaxies in rich galaxy clusters at 0.2 < z < 0.9. Using FORS2 at the VLT we are obtaining rotation curves for the cluster spirals so that their Tully-Fisher relation
can be studied as a function of redshift and compared with that of field spirals. We already have rotation curves for ∼ 10
cluster spirals at z = 0.83, and 25 field spirals at lower redshifts and we plan to increase this sample by one order of magnitude. We present
here the first results of our study, and discuss the implications of our data in the context of current ideas and models of
galaxy formation and evolution.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
74.
Anja Strφmme 《极地研究(英文版)》2002,13(1)
1 TheincoherentscattertechniqueTheuseofincoherentscatterradarsasapowerfulground baseddiagnostictoolforstudyingthenear EarthspaceenvironmentbeganwiththefirsttheoreticalpredictionsbyGordon( 1 958) ,andthefirstobservationsbyBowles( 1 958)afewmonthslater .Thereares… 相似文献
75.
Star formation in cooling flows is usually found to have an initial mass function deficient in massive stars, but the center
of the cooling flow in Hydra A has been shown to contain a significant number of early type stars. Here we use UV-spectra
obtained with the IUE satellite together with ground based data to constrain the nature of this young population. The data
is compatible with a burst of star formation with a Salpeter-like initial mass function, a burst age of about 4 107 yr, and
a total mass ≈ 108 M⊙.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
Bente Aa. Lomstein Bo B. Jørgensen Jutta Niggemann 《Geochimica et cosmochimica acta》2006,70(12):2970-2989
The spatial distribution of total hydrolysable amino acids (THAA) and amino acid enantiomers (d- and l-forms) was investigated in sediments underlying two contrasting Chilean upwelling regions: at ∼23 °S off Antofagasta and at ∼36 °S off Concepción. The contribution of amino acids to total organic carbon (%TAAC: 7-14%) and total nitrogen (%TAAN: 23-38%) in surface sediments decreased with increasing water depth (from 126 to 1350 m) indicating that organic matter becomes increasingly decomposed in surface sediments at greater water depth. Changes in the ratio between the protein amino acid aspartate and its non-protein degradation product β-alanine confirmed this observation. Furthermore, estimates of THAA mineralization showed that sedimentary amino acid reactivity decreased with both increasing water depth as well as progressive degradation status of the organic matter that was incorporated into the sediment. Reactivity of organic matter in the sediment was also assessed using the Degradation Index (DI) developed by [Dauwe, B., Middelburg, J.J., 1998. Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments. Limnol. Oceanogr.43, pp. 782-798.]. Off Concepción, DI was successfully applied to examine the degradation status of sedimentary organic matter at different water depths. However, unexpected results were obtained at the Antofagasta stations as DI increased with sediment depth, suggesting more degraded organic matter at the surface than deeper in the cores. The contribution of peptidoglycan amino acids to THAA was estimated from the concentrations of d-aspartate, d-glutamic acid, d-serine, and d-alanine. Peptidoglycan amino acids accounted for >18% of THAA in all investigated samples. In surface sediments peptidoglycan amino acids accounted for a progressively larger fraction of THAA at increasing water depths (up to >26%). Further, the contribution of peptidoglycan amino acids to THAA increased with increased sediment depth and age (up to 288-year-old) reaching up to 59%. Independent estimates based on d-amino acid concentrations in selected laboratory strains, bacterial counts and the sedimentary concentrations of d-amino acids indicate that a large fraction of the measured d-amino acids (>47 to >97%) originated from cell wall residues rather than from enumerated cells. 相似文献
77.
Brenda Matthews Edwin Bergin Antonio Crapsi Michiel Hogerheijde Jes Jørgensen Dan Marrone Ramprasand Rao 《Astrophysics and Space Science》2008,313(1-3):65-68
We present our most recent results from an ongoing study of the Class 0 source Barnard 1c in Perseus. This source is of particular
interest because it exhibits evidence of strong alignment of grains all the way to the core’s centre, which is contrary to
all other low-mass protostellar cores observed to date. Our goal is to clarify the source of poor alignment in other sources
by identifying the source of strong alignment in B1c. A central cavity has been identified in N2H+ emission; its anticorrelation with C18O emission suggests that heating in the centre has released CO from grain mantles, in turn destroying N2H+. We present sensitivity-limited, high spatial resolution polarimetry data from the SubMillimeter Array and discuss the potential
implications of these data. 相似文献
78.
Submillimeter observations with ALMA will be the essential next step in our understanding of how stars and planets form. Key
projects range from detailed imaging of the collapse of pre-stellar cores and measuring the accretion rate of matter onto
deeply embedded protostars, to unravelling the chemistry and dynamics of high-mass star-forming clusters and high-spatial
resolution studies of protoplanetary disks down to the 1 AU scale. 相似文献
79.
Anaerobic oxidation of methane and sulfate reduction along the Chilean continental margin 总被引:3,自引:0,他引:3
Tina Treude Jutta Niggemann Paul Wintersteller Antje Boetius Bo Barker Jørgensen 《Geochimica et cosmochimica acta》2005,69(11):2767-2779
Anaerobic oxidation of methane (AOM) and sulfate reduction (SR) were investigated in sediments of the Chilean upwelling region at three stations between 800 and 3000 m water depth. Major goals of this study were to quantify and evaluate rates of AOM and SR in a coastal marine upwelling system with high organic input, to analyze the impact of AOM on the methane budget, and to determine the contribution of AOM to SR within the sulfate-methane transition zone (SMT). Furthermore, we investigated the formation of authigenic carbonates correlated with AOM. We determined the vertical distribution of AOM and SR activity, methane, sulfate, sulfide, pH, total chlorins, and a variety of other geochemical parameters. Depth-integrated rates of AOM within the SMT were between 7 and 1124 mmol m−2 a−1, effectively removing methane below the sediment-water interface. Single measurements revealed AOM peaks of 2 to 51 nmol cm−3 d−1, with highest rates at the shallowest station (800 m). The methane turnover was higher than in other diffusive systems of similar ocean depth. This higher turnover was most likely due to elevated organic matter input in this upwelling region offering significant amounts of substrates for methanogenesis. SR within the SMT was mostly fuelled by methane. AOM led to the formation of isotopically light DIC (δ13C: −24.6‰ VPDB) and of distinct layers of authigenic carbonates (δ13C: −14.6‰ VPDB). 相似文献
80.