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The generalized Pareto distribution has received much popularity as models for extreme events in hydrological sciences. In this note, the important problem of the sum of two independent generalized Pareto random variables is considered. Exact analytical expressions for the probability distribution of the sum are derived and a detailed application to drought data from Nebraska is provided. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
374.
Marcelo Samuel Berman 《Astrophysics and Space Science》2007,312(3-4):275-278
We discuss astronomical and astrophysical evidence, which we relate to the principle of zero-total energy of the Universe,
that imply several relations among the mass M, the radius R and the angular momentum L of a “large” sphere representing a Machian Universe. By calculating the angular speed, we find a peculiar centripetal acceleration
for the Universe. This is an ubiquituous property that relates one observer to any observable. It turns out that this is exactly
the anomalous acceleration observed on the Pioneers spaceships. We have thus shown that this anomaly is to be considered a
property of the Machian Universe. We discuss several possible arguments against our proposal. 相似文献
375.
The goals and objectives of ‘climate stabilization’ feature heavily in contemporary environmental policy and in this paper we trace the factors that have contributed to the rise of this concept and the scientific ideas behind it. In particular, we explore how the stabilization-based discourse has become dominant through developments in climate science, environmental economics and policymaking. That this discourse is tethered to contemporary policy proposals is unsurprising; but that it has remained relatively free of critical scrutiny can be associated with fears of unsettling often-tenuous political processes taking place at multiple scales. Nonetheless, we posit that the fundamental premises behind stabilization targets are badly matched to the actual problem of the intergenerational management of climate change, scientifically and politically, and destined to fail. By extension, we argue that policy proposals for climate stabilization are problematic, infeasible, and hence impede more productive policy action on climate change. There are gains associated with an expansion and reconsideration of the range of possible policy framings of the problem, which are likely to help us to more capably and dynamically achieve goals of decarbonizing and modernizing the energy system, as well as diminishing anthropogenic contributions to climate change. 相似文献
376.
John Callahan Frank Hearn Stephen Heron Dennis Schumaker Samuel Swanson 《Journal of Geochemical Exploration》1978,10(1):53-61
A soil geochemical survey for Ni plus magnetic and radiometric surveys were used to outline a small dunite body on Rich Mountain, North Carolina. The dunite body is poorly exposed and is enclosed by garnet-bearing amphibolite of the Ashe Formation. Of the geophysical techniques used, the magnetic survey gives a better definition of the known extent of the body than the radiometric survey. However, the 400-ppm Ni contour from the soil program appears to best define the dunite and suggests that it extends farther to the north and east than was indicated from geologic mapping. Though HF digestion yields higher Ni values than HNO3 + HCl digestion, the patterns are the same. The Mn content of the soil at the Rich Mountain locality probably could also be used to outline the dunite body. 相似文献
377.
Helsen Samuel van Lipzig Nicole P. M. Demuzere Matthias Vanden Broucke Sam Caluwaerts Steven De Cruz Lesley De Troch Rozemien Hamdi Rafiq Termonia Piet Van Schaeybroeck Bert Wouters Hendrik 《Climate Dynamics》2020,54(3):1267-1280
Climate Dynamics - Convection-permitting models (CPMs) have been proven successful in simulating extreme precipitation statistics. However, when such models are used to study climate change,... 相似文献
378.
Samuel D. Crossley Richard D. Ash Jessica M. Sunshine Catherine M. Corrigan Timothy J. McCoy 《Meteoritics & planetary science》2023,58(3):383-404
Models of planetary core formation beginning with melting of Fe,Ni metal and troilite are not readily applicable to oxidized and sulfur-rich chondrites containing only trace quantities of metal. Cores formed in these bodies must be dominated by sulfides. Siderophile trace elements used to model metallic core formation could be used to model oxidized, sulfide-dominated core formation and identify related meteorites if their trace element systematics can be quantified. Insufficient information exists regarding the behavior of these core-forming elements among sulfides during metamorphism prior to anatexis. Major, minor, and trace element concentrations of sulfides are reported in this study for petrologic type 3–6 R chondrite materials. Sulfide-dominated core-forming components in such oxidized chondrites (ƒO2 ≥ iron-wüstite) follow metamorphic evolutionary pathways that are distinct from reduced, metal-bearing counterparts. Most siderophile trace elements partition into pentlandite at approximately 10× chondritic abundances, but Pt, W, Mo, Ga, and Ge are depleted by 1–2 orders of magnitude relative to siderophile elements with similar volatilities. The distribution of siderophile elements is further altered during hydrothermal alteration as pyrrhotite oxidizes to form magnetite. Oxidized, sulfide-dominated core formation differs from metallic core formation models both physically and geochemically. Incongruent melting of pentlandite at 865°C generates melts capable of migrating along solid silicate grains, which can segregate to form a Ni,S-rich core at lower temperatures compared to reduced differentiated parent bodies and with distinct siderophile interelement proportions. 相似文献
379.
M. K. Azer M. D. Samuel K. A. Ali H. A. Gahlan R. J. Stern M. Ren H. E. Moussa 《Mineralogy and Petrology》2013,107(5):829-848
The Wadi Allaqi ophiolite along the Egyptian-Sudanese border defines the southernmost ophiolitic assemblage and suture zone in the Eastern Desert. Ophiolite assemblages comprise nappes composed mainly of mafic and ultramafic rocks that were tectonically emplaced and replaced by serpentine and carbonates along shear zones probably due to CO2-metasomatism. Serpentinites, altered slices of the upper mantle, represent a distinctive lithology of dismembered ophiolites of the western YOSHGAH suture. Microscopically, they are composed of more than 90 % serpentine minerals with minor opaque minerals, carbonate, brucite and talc. The mineral chemistry and whole-rock chemical data reported here indicate that the serpentinized peridotites formed as highly-depleted mantle residues. They show compositions consistent with formation in a suprasubduction zone environment. They are depleted in Al2O3 and CaO similar to those in fore-arc peridotites. Also, high Cr# (Cr/ (Cr+Al)) in the relict chrome spinels (average ~0.72) indicates that these are residual after extensive partial melting, similar to spinels in modern fore-arc peridotites. Therefore, the studied serpentinites represent fragments of an oceanic lithosphere that formed in a fore-arc environment, which belongs to an ophiolitic mantle sequence formed in a suprasubduction zone. 相似文献
380.
Marcelo Samuel Berman 《Astrophysics and Space Science》2011,336(2):327-329
We consider a General Relativistic RW’s metric, with variable speed of light, and find a field of Universal acceleration,
numerically coincident with the value of the Pioneers anomalous one. This deceleration may decrease with time, as we calculated.
This is relevant to understand the Physics that may be involved in the Cosmological approach to the Pioneers anomaly. 相似文献