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31.
Essaïeb Hamdi Najla Bouden Romdhane Jean du Mouza Jean Michel Le Cleac’h 《Geotechnical and Geological Engineering》2008,26(2):133-146
The theoretical explosive energy used in blasting is a common issue in many recent research works (Spathis 1999; Sanchidrian 2003). It is currently admitted that the theoretical available energy of the explosives is split into several parts during a blast:
seismic, kinetic, backbreaks, heave, heat and fragmentation energies. Concerning this last one, the energy devoted to the
breakage and to the creation of blocks within the muckpile can be separated from the microcracking energy which is devoted
to developing new and/or extending existing micro cracks within the blocks (Hamdi et al. 2001; López et al. 2002). In order to investigate these two types of energy, a first and important task is to precisely study the main parameters
characterising the two constitutive elements of the rock mass (rock matrix and discontinuity system). This should provide
useful guidelines for the choice of the blasting parameters (type of explosive, blasting pattern, etc.), in order to finally
control the comminution process. Within the frame of the EU LESS FINES research project, devoted to the control of fines production,
the methodology was developed in order to: (1) characterize the in situ rock mass, by evaluating the density, anisotropy,
interconnectivity and fractal dimension of the discontinuity system and (2) evaluate fragmentation (both micro and macro)
energy spent during the blasting operation. The methodology was applied to three production blasts performed in the Klinthagen
quarry (Sweden) allowing to estimate the part of the fragmentation energy devoted to the formation of muck pile blocks on
one side and to the muckpile blocks microcracking on the other side. 相似文献
32.
Pirin Erdodu Ofer Lahav Saleem Zaroubi George Efstathiou Steve Moody John A. Peacock Matthew Colless Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(3):939-960
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34.
长江三角洲泥质潮坪沉积间断的定量分析 总被引:19,自引:0,他引:19
现场观测获得了长江口开敞型泥质潮坪不同时间尺度的沉积速率及层偶保存率。每天观测结果表明,单个层偶的保存率约为46.6%。随着观测时间间隔的增大保存率迅速减小,大小潮周期内层偶保存率降为9.2%,季节性观测层偶保存率为3.7%。现代长江三角洲建造一个完整的潮坪沉积层序约需96a。百年尺度潮坪层序层偶的保存率仅为0.74%,99.26%的潮汐周期由于侵蚀或无沉积而没有纹层保存下来,形成间断。因此,沉积间断占潮坪层序的比例应为99.26%。沉积速率和沉积时间之间存在对数线性负相关,拟合直线的斜率为-0.39,由此推导出潮坪层序的完整性计算公式为C=(t^*/t)^ 0.39。虽然对泥质潮坪沉积中沉积间断的估计有很大的不确定性,但它是从现代沉积过程观测中得到的,可以帮助我们更深入地认识古代潮坪沉积的特征及其成因,并突出沉积间断在潮坪沉积层序中的重要性。 相似文献
35.
H. Lammer A. Hanslmeier J. Schneider I. K. Stateva M. Barthelemy A. Belu D. Bisikalo M. Bonavita V. Eybl V. Coudé du Foresto M. Fridlund R. Dvorak S. Eggl J. -M. Grießmeier M. Güdel E. Günther W. Hausleitner M. Holmström E. Kallio M. L. Khodachenko A. A. Konovalenko S. Krauss L. V. Ksanfomality Yu. N. Kulikov K. Kyslyakova M. Leitzinger R. Liseau E. Lohinger P. Odert E. Palle A. Reiners I. Ribas H. O. Rucker N. Sarda J. Seckbach V. I. Shematovich A. Sozzetti A. Tavrov M. Xiang-Grüß 《Solar System Research》2010,44(4):290-310
After the discovery of more than 400 planets beyond our Solar System, the characterization of exoplanets as well as their host stars can be considered as one of the fastest growing fields in space science during the past decade. The characterization of exoplanets can only be carried out in a well coordinated interdisciplinary way which connects planetary science, solar/stellar physics and astrophysics. We present a status report on the characterization of exoplanets and their host stars by reviewing the relevant space- and ground-based projects. One finds that the previous strategy changed from space mission concepts which were designed to search, find and characterize Earth-like rocky exoplanets to: A statistical study of planetary objects in order to get information about their abundance, an identification of potential target and finally its analysis. Spectral analysis of exoplanets is mandatory, particularly to identify bio-signatures on Earth-like planets. Direct characterization of exoplanets should be done by spectroscopy, both in the visible and in the infrared spectral range. The way leading to the direct detection and characterization of exoplanets is then paved by several questions, either concerning the pre-required science or the associated observational strategy. 相似文献
36.
P. Erdodu J. P. Huchra O. Lahav M. Colless R. M. Cutri E. Falco T. George T. Jarrett D. H. Jones C. S. Kochanek L. Macri J. Mader N. Martimbeau M. Pahre Q. Parker A. Rassat W. Saunders 《Monthly notices of the Royal Astronomical Society》2006,368(4):1515-1526
We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than K s = 11.25 and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to 12°± 7° at around 50 h −1 Mpc , but then increases at larger distances, reaching 21°± 8° at around 130 h −1 Mpc . Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to 14°± 7° away from the CMB velocity dipole. In both cases, the dipole seemingly converges by 60 h −1 Mpc . Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters Ω0.6 m / b L = 0.40 ± 0.09 . 相似文献
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38.
Biomonitoring of estuarine pollution is the subject of active research, and benthic foraminifera are an attractive group to use for these purposes due to their ubiquitous presence in saline water and wide diversity. Here, we describe a case study of biomonitoring using benthic foraminifera in the French Mediterranean lagoon, Bages-Sigean lagoon. In this case, the major pollutants of interest are heavy metals in the sediment, particularly contaminated by Cu and Cd derived from industrial and agricultural sources. The foraminiferal assemblages of the Bages-Sigean lagoon are typical of normal paralic environments, but unusually almost completely lack agglutinated forms. The density of benthic foraminifera was shown to be more influenced by the sediment characteristics rather than heavy metal pollution. However, the relative abundance of Quinqueloculina bicostata was shown to increase in the most polluted areas and we propose that this taxon may be used as an indicator of heavy metal pollution. 相似文献
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40.
Alex L. du Toit 《International Journal of Earth Sciences》1938,30(1-2):138-147
Summary The Atlantic-Arctic Basin is antipodal to the Pacific. Powerful evidence is cited to indicate its development through Continental Drift, as suggested byPickering in 1907. Initiated from the Mesozoic Tethys and progressively enlarged during the Tertiary, its outlines were essentially determined by tensional-rifting oriented mainly N.E and N.W within a zone extending more than half round the circumference of the Earth, from the Antarctic to Alaska. During the Alpine diastrophism fold-linkages, that functioned as land bridges, were pushed up across the Ocean between the West Indies and Eurafrica and subsequently destroyed by the continued westerly drift of the Americas. Crustal stretching was accompanied by widespread volcanicity. The Mid-Atlantic Rise is recent and has an Isostatic basis. The Atlantic-Arctic stretch-basin is largely bordered by Fault-Line Coasts and by downwarped shores that show the marginal, entrenched, terrestially-evolved drainages known as Submarine Canyons. 相似文献