全文获取类型
收费全文 | 527篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 55篇 |
地球物理 | 101篇 |
地质学 | 241篇 |
海洋学 | 26篇 |
天文学 | 91篇 |
综合类 | 5篇 |
自然地理 | 31篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 17篇 |
2014年 | 18篇 |
2013年 | 32篇 |
2012年 | 19篇 |
2011年 | 37篇 |
2010年 | 36篇 |
2009年 | 41篇 |
2008年 | 27篇 |
2007年 | 34篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1959年 | 1篇 |
1914年 | 2篇 |
1912年 | 1篇 |
排序方式: 共有558条查询结果,搜索用时 15 毫秒
471.
Jesus S.M. Porter M.B. Stephan Y. Demoulin X. Rodriguez O.C. Coelho E.M.M.F. 《Oceanic Engineering, IEEE Journal of》2000,25(3):337-346
The method presented in this paper assumes that the received signal is a linear combination of delayed and attenuated uncorrelated replicas of the source emitted waveform. The set of delays and attenuations, together with the channel environmental conditions, provide sufficient information for determining the source location. If the transmission channel is assumed known, the source location can be estimated by matching the data with the acoustic field predicted by the model conditioned on the estimated delay set. This paper presents alternative techniques that do not directly attempt to estimate time delays from the data but, instead, estimate the subspace spanned by the delayed source signal paths. Source Localization is then done using a family of measures of the distance between that subspace and the subspace spanned by the replicas provided by the model. Results obtained on the INTIMATE'96 data set, in a shallow-water acoustic channel off the coast of Portugal, show that a sound source emitting a 300-800-Hz LFM sweep could effectively be localized in range or depth over an entire day 相似文献
472.
How are granite magmas transported from their source regions in the deep crust, through 10–40 km of overlying solid rock and emplaced close to the Earth's surface? What are the mechanical processes that allow this to take place and how long does it all take? These problems have challenged and preoccupied geologists since the days of Hutton. In the ensuing 200 years or so, a range of ideas from the plausible to the eccentric have been put forward to explain the granite phenomenon. As a result of developments in our understanding of the physical behaviour of granitic magmas and their host rocks over the last decade, we are now in a position to begin to offer some more informed and realistic models of the processes involved. 相似文献
473.
Concepts of several experimental configurations for the investigation of magnetized jets and their interaction with magnetized
environments are presented. In the planned experiments, the plasma jets will be created by laser ablation of shaped targets,
while magnetic and electric fields with the required configurations will be produced independently by a pulsed power generator.
In particular, the recently coupled Terawatt laser Tomcat and Terawatt pulsed power generator Zebra will be used for experiments. 相似文献
474.
475.
476.
Charles E. Tilburg Shaun M. Gill Stephan I. Zeeman Amy E. Carlson Timothy W. Arienti Jessica A. Eickhorst Philip O. Yund 《Estuaries and Coasts》2011,34(4):785-799
Interest in the coastal dynamics of river plumes has mainly focused on large rivers, but plumes from the more numerous smaller
rivers have important local consequences and may, in aggregate, be significant contributors to coastal circulation. We studied
the dynamics of the plume from the Saco River in Saco Bay, Gulf of Maine, over a 3-year period. The transport and salinity
in the region are governed by river discharge, tides, winds, and interaction with the Western Maine Coastal Current. The dynamics
of the flow field vary with location within the plume and discharge. The far-field dynamics of the Saco River plume are dominated
by inertial processes (hence qualifying it as a small-scale river plume), during times of low discharge, with low salinity
water present both up and downstream of the river mouth, but are dominated by rotational processes during times of high discharge
(thus qualifying it as a large-scale river plume), with buoyant water primarily advected downshelf. Near-field dynamics are
governed by weak, subcritical flow during low discharge but strongly inertial, supercritical flow during high discharge. Offshore
movement of the plume is not governed by Ekman dynamics but is instead a result of discharge, wind-induced vertical mixing,
and the geography of the coastline and adjacent islands. 相似文献
477.
478.
The adsorption of two model siderophores, desferrioxamine B (DFOB) and aerobactin, to lepidocrocite (γ-FeOOH) was investigated by attenuated total reflection infrared spectroscopy (ATR-FTIR). The adsorption of DFOB was investigated between pH 4.0 and 10.6. The spectra of adsorbed DFOB indicated that two to three hydroxamic acid groups of adsorbed DFOB were deprotonated in the pH range 4.0-8.2. Deprotonation of hydroxamic acid groups of adsorbed DFOB at pH values well below the first acid dissociation constant of solution DFOB species (pKa = 8.3) and well below the point of zero charge of lepidocrocite (pHPZC = 7.4) suggested that the surface speciation at the lower end of this pH range (pH 4) is dominated by a surface DFOB species with inner-sphere coordination of two to three hydroxamic acids groups to the surface. Maximum adsorption of DFOB occurred at approximately pH 8.6, close to the first pKa value of the hydroxamic acid groups, and decreased at lower and higher pH values.The spectra of adsorbed aerobactin in the pH range 3-9 indicated at least three different surface species. Due to the small spectral contributions of the hydroxamic acid groups of aerobactin, the interactions of these functional groups with the surface could not be resolved. At high pH, the spectral similarity of adsorbed aerobactin with free aerobactin deprotonated at the carboxylic acid groups indicated outer-sphere complexation of the carboxylate groups. With decreasing pH, a significant peak shift of the asymmetric carboxylate stretch vibration was observed. This finding suggested that the (lateral) carboxylic acid groups are coordinated to the surface either as inner-sphere complexes or as outer-sphere complexes that are strongly stabilized at the surface by hydrogen bonding at low pH. 相似文献
479.
The postcollisional, Mesozoic, C-type or high-K adakitic intrusions (K-adakites) of China lack either temporal or spatial association with subduction and have K2O/Na2O around unity. Otherwise, their geochemistry is very similar to ordinary adakites. New experimental data, geological observations and theoretical considerations lead us to suggest that these K-adakites were high-T (> 1050 and probably > 1075 °C), rather hydrous magmas ( 6 wt.% H2O) produced by fluid-absent partial melting of metatonalites, meta-andesites, or possibly potassic metabasalts at pressures exceeding 2 GPa. Their peculiar chemistry is a consequence of both the elevated K2O/Na2O in the protolith and the very high pressure of partial melting. The most likely tectonic setting is one of extreme crustal thickening followed by delamination of the eclogitic keel and partial melting of this continental crustal material at mantle depths, with high mantle heat flow, during orogenic collapse. 相似文献
480.
Dirk Frei Axel Liebscher Gerhard Franz Bernd Wunder Stephan Klemme Jon Blundy 《Contributions to Mineralogy and Petrology》2009,157(4):473-490
We determined experimentally the Nernst distribution coefficient between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230°C up to 3.2 GPa/1,535°C in a piston cylinder apparatus.
Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and
ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb,
Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic
at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18–20 mol%. The rare earth elements show a continuous, significant increase in
compatibility with decreasing ionic radius from D
Laopx−melt ∼ 0.0008 to D
Luopx−melt ∼ 0.15. For the high-field-strength elements compatibility increases from D
Thopx−melt ∼ 0.001 through D
Nbopx−melt ∼ 0.0015, D
Uopx−melt ∼ 0.002, D
Taopx−melt ∼ 0.005, D
Zropx−melt ∼ 0.02 and D
Hfopx−melt ∼ 0.04 to D
Tiopx−melt ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D
0M1, D
0M2, r
0M1, r
0M2, E
0M1, and E
0M2 for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline
distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene;
for the divalent cations D
i
M2−M1 varies by three orders of magnitude between D
CoM2−M1 = 0.00098–0.00919 and D
BaM2−M1 = 2.3–28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on
M2; D
LaM2−M1 reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our
new comprehensive data set can be used for polybaric-polythermal melting models along the Earth’s mantle solidus.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献