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51.
Krahn MM Hanson MB Baird RW Boyer RH Burrows DG Emmons CK Ford JK Jones LL Noren DP Ross PS Schorr GS Collier TK 《Marine pollution bulletin》2007,54(12):1903-1911
“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter. 相似文献
52.
Some major challenges for geophysicists and structural geologists using three-dimensional boundary element method codes (3D-BEM)
are: (1) reducing the amount of memory required to solve large and dense systems and (2) incorporation of inequality constraints
such as traction inequality constraints (TIC) and displacement inequality constraints (DIC). The latter serves two purposes.
First, for example, inequality constraints can be used to simulate frictional slip (using TIC). Second, these constraints
can prevent element interpenetration while allowing opening mode (using DIC). We have developed a method that simultaneously
incorporates both types of functionality of the inequality constraints. We show that the use of an appropriate iterative solver
not only avoids the allocation of significant memory for solving the system (allowing very large model computation and simplifying
parallelization on multi-core processors), but also admits interesting features such as natural incorporation of TICs and
DICs. Compared to other techniques of contact management (e.g., Lagrange multipliers, penalty method, or complementarity problem),
this new simple methodology, which does not use any incremental trial-and-error procedures, brings more flexibility, while
making the system more stable and less subject to round-off errors without any computational overhead. We provide validations
and comparisons of the inequality constraints implementation using 2D analytical and numerical solutions. 相似文献
53.
L. C. Radke P. W. Ford I. T. Webster I. Atkinson G. Douglas K. Oubelkheir J. Li B. Robson B. Brooke 《Aquatic Geochemistry》2010,16(1):1-29
The Fitzroy River delivers large amounts of nutrients and fine sediments to Keppel Bay (contiguous with the Great Barrier
Reef Lagoon) during intermittent flow events. This study explores sources, forms and transformations of nutrients in Keppel
Bay, and develops a functional process zonation that integrates seabed geochemistry and water column nutrient characteristics
which are controlled by suspended sediment. The water column and seabed properties were investigated over two dry seasons,
with supplementary core incubations taken to measure carbon decomposition rates and nutrient fluxes. Keppel Bay can be divided
into three zones, the: zone of maximum resuspension (ZMR); coastal transitional zone (CTZ); and blue water zone (BWZ). Mineralisation
of predominantly terrestrial organic matter occurs in the ZMR where nutrient uptake by phytoplankton is light limited. The
CTZ and BWZ had higher light penetration and phytoplankton growth was likely limited by N and P, respectively. The identified
zones conform to the bathymetry and hydrodynamic characteristics of the bay, allowing for the development of an integrated
conceptual model accounting for the benthic and pelagic biogeochemical processes. Recognition of these different zones shows
that considerable variation in benthic and water column properties is possible within a small system with the bathymetric
and hydrodynamic characteristics of the fluidized bed reactor. 相似文献
54.
Understanding of the human dimensions of climate change (HDCC) in glaciated mountain regions is limited by a deficit in systematically collated information on where, to what stressors, by whom, at what scale, and with what effect adaptation is occurring. This paper presents a systematic literature review of the recent English language peer-reviewed scholarship on adaptation in glaciated mountain regions. 4050 potentially relevant articles were examined, with 36 included for full review. Results indicate that scholarly investigation into adaptation in glaciated mountains is presently limited to only 40 % of countries with alpine glaciation. Seventy-four discrete adaptation initiatives were identified, with most occurring in Peru (28 %), Nepal (22 %) and India (17 %). Many documented adaptations were initiated in response to intersecting stressors related to cryospheric change and socio-economic development; were autonomous and initiated in reaction to experienced climatic stimuli; and were carried out at the individual, family, or community scale. The study contributes to an emerging literature tracking on-the-ground adaptation processes and outcomes, and identifies a need to raise the profile of human adaptation in glaciated mountain regions within the HDCC scholarship. A research agenda for addressing key knowledge gaps and questions is developed, providing a framework for future investigation. 相似文献
55.
Michele Kaufman 《Astrophysics and Space Science》1976,40(2):369-384
Absorption by gas and dust in circumstellar Hii regions within primeval galaxies could seriously depress the far-ultraviolet continuum radiation emitted by primeval galaxies. This effect might account for the failure of Partridge (1974) and Davis and Wilkinson (1974) to detect the redshifted radiation from primeval galaxies at optical and near-infrared wavelengths. A primeval galaxy becomes very bright only during the final stages of contraction. Provided that dust can form by the time the primeval galaxy reaches peak luminosity, a significant fraction of the stellar far-ultraviolet radiation is converted into far-infrared. Thus an appropriate spectral region to search for the redshifted integrated background from primeval galaxies lies between 350 , where the 2.7 K microwave background radiation becomes important, and 150 , where other extragalactic discrete sources, such as nearby galactic nuclei, may contribute. The expected IR flux is calculated with Kaufman's (1975) model for the star formation rate in the contracting galaxy. Letz
p be the redshift andT
g the grain temperature when the primeval galaxy becomes very bright. Unlessz
p10 orT
g is fairly high, the intensity of the far-infrared radiation from primeval galaxies would be dominated by the high frequency tail of the 2.7 K microwave background. On the other hand, if dust is unimportant, we determine the spectral energy distribution of a primeval galaxy emitted in the range 912 Å to 2050 Å; we find that the luminosities are not very sensitive to the dependence of effective temperatures on metal abundance. 相似文献
56.
57.
Trevor D. Ford 《Geology Today》1999,15(6):230-234
58.
Julien Léger Raphaël Pik Bouchaïb Tibari Sébastien Ternois Mary Ford Chantal Peiffert Julien Mercadier 《Geostandards and Geoanalytical Research》2023,47(2):219-242
The in situ (U-Th-Sm)/He and U/Pb laser-ablation double-dating procedure is a valuable method that can provide a large dataset relatively efficiently in contrast with conventional bulk helium thermochronometry. In this study, we evaluate the potential age error associated with the double ablation procedure and report the in situ (U-Th-Sm)/He double-ablation dating of 249 zircons from the Fish Canyon Tuff locality. With LA-ICP-MS pseudo-depth profiling and 3D numerical modelling, we show that the concentric double-ablation procedure in minerals with U-Th-Sm zoning can generate a significant (U-Th-Sm)/He age error (positive or negative), resulting in over-scattering and/or an offset of the mean age. Pseudo-depth profiling is insufficient to predict the individual age error, partly because of the superimposed ablations. To evaluate the consequence of this inherent bias, we confront a synthetic age distribution to the error expected for U-Th-Sm zoned zircons analysed with double-ablation (U-Th-Sm)/He thermochronometry. As expected, a strong age bias causes the spreading of peak ages, downgrading the original signal. Yet, the throughput of the ablation-based method can allow intra- and inter-sample peak age identification and comparison, and the coupling of (U-Th-Sm)/He and U/Pb ages extends our ability to deconvolute a multimodal age spectrum. 相似文献
59.
Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain) 总被引:1,自引:1,他引:0
60.