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151.
Intracellular partitioning of trace metals is critical to metal tolerance in aquatic organisms and may also influence metal trophic transfer in ecosystems. In this study, we tested the relevance of metal (Cd, Cu, Pb, and Zn) intracellular partitioning in prey as an indicator of metal trophic availability to benthic forage fish, mummichogs (Fundulus heteroclitus), in chronically metal-polluted salt marshes in New York, USA. Two common prey of mummichogs in the study area, Palaemonetes pugio and Nereis acuminata, generally stored increasingly higher proportions of non-essential metals (particularly Pb) in insoluble (less trophically available) cellular components, as the whole body burdens increased. In contrast, intracellular partitioning of essential metals (Cu and Zn) in invertebrate prey varied relatively little among sites. Differential Cd and Pb intracellular partitioning patterns within P. pugio among sites were significantly associated with Cd and Pb whole body burdens in mummichogs, respectively (i.e., prey-driven bioreduction of metals), while bioaccumulation of Cu and Zn in mummichogs was similar among populations. The findings in this study suggest that metal intracellular partitioning within prey may be partially responsible for metal trophic availability to a predator in metal-polluted habitats, while there was also evidence that some predator-dependent processes may offset differential trophic availabilities from prey. 相似文献
152.
Southern California's marine areas are heavily contaminated with dichloro-diphenyl-trichloroethane (DDT) and polychlorinated-biphenyls (PCBs), and fish consumption advisories (FCAs) have been issued throughout the region. Between 2002 and 2003, the Montrose Angler Survey, a large-scale survey of subsistence anglers, was developed and implemented on site in Orange and Los Angeles counties. This survey was intended to assist natural resource trustees in the development of restoration programs that will address injuries to natural resources and restore lost economic services for anglers, but the data were never fully analyzed. The trustees have shown a clear preference for ecological restoration programs that may take years to improve fishing services. In contrast, this analysis, which includes a random-parameter fishing site choice model, demonstrates that simple, inexpensive programs such as better signage to warn of FCAs and transportation to clean sites have the potential to yield substantial benefits quickly. This paper also focuses on how different ethnic minority groups are affected by FCAs, and determines how best to communicate risk information and change fishing behavior through outreach programs. 相似文献
153.
Sabine K.J. Cochrane Stanislav G. Denisenko Paul E. Renaud Christopher S. Emblow William G. Ambrose Jr. Ingrid H. Ellingsen Jofrid Skarhamar 《Journal of Sea Research》2009,61(4):222-233
Benthic faunal assemblages were analysed from 47 stations in the central and southern parts of the Barents Sea, together with sedimentary and water column parameters, daily ice records and modelled integrated primary productivity. Sampling spanned areas influenced by Atlantic Water (AW) to those lying under Arctic Water (ArW), and included stations with mixed water masses. Ice cover suppressed water column productivity in the northern areas. Three main faunal groups were identified, based on similarity of numerical faunal composition. The northern and southern faunal groups were separated by the northernmost penetration of AW in the bottom water and the third group, the Hopen group, was influenced by modified bank water. Faunal abundances were significantly higher within the southern faunal group relative to the northern group, but the numbers of taxa present were similar. The particularly rich fauna of the Hopen group reflected sediment heterogeneity and tight pelagic–benthic coupling. These results suggest that a retreat and thinning of the ice cover in the Barents Sea likely will result in the northern parts of the Barents Sea becoming more Atlantic in character, with a higher productivity at the sea floor. 相似文献
154.
Geoffrey Blewitt William C. Hammond Corné Kreemer Hans-Peter Plag Seth Stein Emile Okal 《Journal of Geodesy》2009,83(3-4):335-343
We identify the key design aspects of a GPS-based system (and in the future, GNSS-based systems) that could contribute to real-time earthquake source determination and tsunami warning systems. Our approach is based on models of both transient and permanent displacement of GPS stations caused by large earthquakes, while considering the effect of GPS errors on inverted earthquake source parameters. Our main conclusions are that (1) the spatial pattern, magnitude, and timing of permanent displacement of GPS stations can be inverted for the earthquake source and so predict the 3D displacement field of the ocean bottom, thus providing the initial conditions for tsunami models, and (2) there are no inherently limiting factors arising from real-time orbit and positioning errors, provided sufficient near-field GPS stations are deployed. This signal could be readily exploited by GPS networks currently in place, and will be facilitated by the IGS Real-Time Project as it comes to fruition. 相似文献
155.
Seismic reflection profiling in the South San Clemente Basin and the southern portion of the San Diego Trough has revealed at least six sedimentary units exhibiting varying stages of deformation. Four of the units are interpreted to be marine turbidites supplied by adjacent submarine canyons. Sediments comprising the Descanso Plain and correlative material within the South San Clemente Basin are attributed to a southerly source (Banda Canyon), while the more recent Quaternary turbidites from Coronado Canyon filled the southern San Diego Trough and then spilled over into South San Clemente Basin. The relatively high but intermittent rates of sedimentation, together with shifting sources and areas of deposition, have resulted in sedimentary units that were emplaced in comparatively short episodes but which were subjected to relatively continuous tectonic activity. Consequently, the sedimentary layers of each unit appear uniformly affected by deformation which increases in successively older units. 相似文献
156.
William P Dillon 《Marine Geology》1974,16(3):121-143
The structure of the continental shelf off southern Morocco was studied by means of 2,100 km of seismic reflection profiles, magnetic and bathymetric surveys, and dredge samples. The research area lies off four geologic divisions adjacent to the coast: the Atlas Mountains; the Souss Trough; the Anti-Atlas Mountains; and the Aaiun Basin. The continental shelf, along with the western Atlas Mountains, the western Souss Trough, and the entire Aaiun Basin, has subsided along a normal fault-flexure system. This system runs along the shore at the Anti-Atlas Mountains, and cuts off this cratonic block from the shelf subsidence. The shelf is narrow and characterized by out-building off the Anti-Atlas range, whereas it is broader and characterized by upbuilding to the north and south. Deposition was essentially continuous at least from Early Cretaceous through Eocene time. Published work suggests that the last cycle of sedimentation began during Permian rifting. After Eocene time, most sediments carried to the shelf must have bypassed it and gone to construct the slope and rise or to the deep sea. Tertiary orogenies caused extensive folding of Mesozoic and early Tertiary deposits off the Atlas Mountains. 相似文献
157.
158.
William Blumen 《地球物理与天体物理流体动力学》2013,107(1-3):89-104
Abstract Adiabatic, two-dimensional, steady-state finite-amplitude, hydrostatic gravity waves produced by flow over a ridge are considered. Nonlinear self advection steepens the wave until the streamlines attain a vertical slope at a critical height zc. The height zc , where this occurs, depends on the ridge crest height and adiabatic expansion of the atmosphere. Dissipation is introduced in order to balance nonlinear self advection, and to maintain a marginal state above zc. The approach is to assume that the wave is inviscid except in a thin layer, small compared to a vertical wavelength, where dissipation cannot be neglected. The solutions in each region are matched to obtain a continuous solution for the streamline displacement δ. Solutions are presented for different values of the nondimensional dissipation parameter β. Eddy viscosity coefficients and the thickness of the dissipative layer are expressed as functions of β, and their magnitudes are compared to other theoretical evaluations and to values inferred from radar measurements of the stratosphere. The Fourier spectrum of the solution for z ≫ zc is shown to decay exponentially at large vertical wave numbers n. In comparison, a spectral decay law n ?-8/3 characterizes the marginal state of the wave at z = zc . 相似文献
159.
Marie Ekström Natasha Kuruppu Robert L. Wilby Hayley J. Fowler Francis H.S. Chiew Suraje Dessai William J. Young 《Global Environmental Change》2013,23(1):115-129
Previous climate risk assessments provide important methodological insights into how to derive tractable research questions and the appropriate use of data under uncertainty, as well as identifying steps that benefit from stakeholder involvement. Here we propose the use of a framework for the systematic and objective exploration of climate risk assessments. The matrix facilitates a breakdown of information about aim and context, main results, methodological choices, stakeholder involvement, sources and characteristics of uncertainties and overall weaknesses. We then apply the matrix to three risk assessments in the water sector to explore some methodological strengths and weaknesses of approaches strongly linked to climate model outputs (top-down) versus those that originate from local knowledge of climate exposures (bottom-up), and demonstrate that closer integration with social and physical sciences is more likely to yield robust climate risk assessments. 相似文献
160.
William K. Dewar 《地球物理与天体物理流体动力学》2013,107(1-4):53-85
Abstract The term ‘‘solitary wave'’ is usually used to denote a steadily propagating permanent form solution of a nonlinear wave equation, with the permanency arising from a balance between steepening and dispersive tendencies. It is known that large-scale thermal anomalies in the ocean are subject to a steepening mechanism driven by the beta effect, while at the smaller deformation scale, such phenomena are highly dispersive. It is shown here that the evolution of a physical system subject to both effects is governed by the ‘‘frontal semi-geostrophic equation'’ (FSGE), which is valid for large amplitude thermocline disturbances. Solitary wave solutions of the FSGE (here named planetons) are calculated and their properties are described with a view towards examining the behavior of finite amplitude solitary waves. In contrast, most known solitary wave solutions belong to weakly nonlinear wave equations (e.g., the Korteweg—deVries (KdV) equation). The FSGE is shown to reduce to the KdV equation at small amplitudes. Classical sech2 solitons thus represent a limiting class of solutions to the FSGE. The primary new effect on planetons at finite amplitudes is nonlinear dispersion. It is argued that due to this effect the propagation rates of finite amplitude planetons differ significantly from the ‘‘weak planeton'', or KdV, dispersion relation. Planeton structure is found to be simple and reminiscent of KdV solitons. Numerical evidence is presented which suggests that collisions between finite amplitude solitary waves are weakly inelastic, indicating the loss of true soliton behavior of the FSGE at moderate amplitudes. Lastly, the sensitivity of solitary waves to the existence of a nontrivial far field is demonstrated and the role of this analysis in the interpretation of lab experiments and the evolution of the thermocline is discussed. 相似文献