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991.
P. A. Solotchin E. V. Sklyarov E. P. Solotchina Y. N. Markova 《Doklady Earth Sciences》2017,473(2):461-466
New research results are presented on the processes of carbonate sedimentation in shallow saline lakes of Western Transbaikalia by the example of the Holocene bottom sediments of Sul’fatnoe Lake (the Selenga Dauria). The techniques of X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, and isotope and elemental analyses were used. By means of decomposition the XRD profiles using the Pearson VII function, the carbonate phases were identified and their quantitative ratios were determined. The evolution of the lake basin caused by climate changes in the Holocene was reconstructed by comparing the carbonate record to the concentrations determined for the 18O and 13C stable isotopes and to lithological, geochemical, and palynological data in the dated sedimentary section. 相似文献
992.
Abstract— Glacial deposits at the margins of the ice cap of the northern island of the Novaya Zemlya archipelago, Russia, contain numerous spherules and rare scoriaceous particles thought to be extraterrestrial. The 1 Kyr old glacier has decreased in volume and coverage during the last 40 years, leaving the spherules contained in the ice at the margins of the glacier where they can be easily collected. The spherules are similar in their appearance, texture, and mineralogy to cosmic spherules found in deep‐sea sediments in Greenland and Antarctica. Silicate spherules have typical bar‐like textures (75%) or porphyritic textures (15%), while other spherules are glassy (7%). The spherules from Novaya Zemlya are altered only slightly. There are spherules consisting of iron oxides, metal cores with iron oxide rims, a continuous network of iron oxide dendrites in a glass matrix, and particles rich in chromite (3%). Some spherules contain metal droplets and relict forsterite and low‐Ca pyroxene. Silicate spherule compositions match compositions of other cosmic spherules. Both Nova Zemlya and other cosmic spherules are close to carbonaceous chondrite matrices in patterns of variations for Ca, Mg, Si, and Al, which might suggest that their predecessor was similar to carbonaceous chondrite matrices. Unmelted micrometeorites are generally depleted in Ca and Mg and enriched in Al relative to cosmic spherules. The depletion of the micrometeorites in Ca and Mg can be connected with their terrestrial alteration (Kurat et al. 1994), while the Al enrichment seems to be primary. 相似文献
993.
Theory for Reconstruction of an Unknown Number of Contaminant Sources using Probabilistic Inference 总被引:1,自引:0,他引:1
Eugene Yee 《Boundary-Layer Meteorology》2008,127(3):359-394
We address the inverse problem of source reconstruction for the difficult case of multiple sources when the number of sources
is unknown a priori. The problem is solved using a Bayesian probabilistic inferential framework in which Bayesian probability
theory is used to derive the posterior probability density function for the number of sources and for the parameters (e.g.,
location, emission rate, release time and duration) that characterize each source. A mapping (source–receptor relationship)
that relates a multiple source distribution to the concentration measurements made by an array of detectors is formulated
based on a forward-time Lagrangian stochastic model. A computationally efficient methodology for determination of the likelihood
function for the problem, based on an adjoint representation of the source–receptor relationship and realized in terms of
a backward-time Lagrangian stochastic model, is described. An efficient computational algorithm based on a parallel tempered
Metropolis-coupled reversible-jump Markov chain Monte Carlo (MCMC) method is formulated and implemented to draw samples from
the posterior probability density function of the source parameters. This methodology allows the MCMC method to initiate jumps
between the hypothesis spaces corresponding to different numbers of sources in the source distribution and, thereby, allows
a sample from the full joint posterior distribution of the number of sources and the parameters for each source to be obtained.
The proposed methodology for source reconstruction is tested using synthetic concentration data generated for cases involving
two and three unknown sources. 相似文献
994.
Modeling nonhydrostatic atmospheric flow requires the solution of the vertical equation of motion and a prognostic or diagnostic equation for pressure. If the nonhydrostatic components of the flow are relatively small, they can be approximated and incorporated into a purely hydrostatic model, which usually is conceptually simpler and computationally more efficient. A method to do this for a linear model of local thermally-induced circulations is further developed and adapted to a non-linear numerical model of the neutral atmospheric boundary layer. A hydrostatic model and the quasi-nonhydrostatic version were used to simulate neutral flow over simple terrain features. One set of observations taken over a simple change in roughness and another set taken over a change in both roughness and terrain were simulated by both models to assess the capabilities of the quasi-nonhydrostatic technique.It is found that (as expected) the pressure deviation from the hydrostatic state is negligible for the roughness change, but it is an important aspect of neutral flow over terrain. Thus, for flow encountering a simple roughness change, the hydrostatic approximation is good, even for small horizontal scales. However, the quasi-nonhydrostatic model qualitatively produces the features in the observations for flow over a terrain change that the hydrostatic model cannot produce.Journal Paper No. J-12737 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2779. 相似文献
995.
GPS technology will face not one but two critical rollover dates over the next eight months. One is the millennium (Y2K) rollover.
The other is the GPS week 1024 rollover also known as the GPS End of the Week (EOW). Each rollover dat has the potential to
cause severe problems in GPS receivers and related software. This article expolres the reasons why these dates are a problem
and describes choices that must be made as to their solution. The paper also describes some verification methods that may
be used to test GPS receivers and software. ? 1999 John Wiley & Sons, Inc. 相似文献
996.
William Harbert Maxim Alexutin Sergei Sokolov Kirill Krylov Vladimir Grigoriev Alexander Heiphetz Robert Graham 《Tectonophysics》2001,340(3-4):215-231
The northernmost part of the Kamchatka Peninsula of northeastern Russia, located along the northwestern margin of the Bering Sea, consists of zones of complexly deformed accreted terranes. Progressing from the northwestern Bering Sea inland are the Olyutorskiy, Ukelayat, and Koryak superterranes, which were accreted to the Okhotsk–Chukotsk volcanic–plutonic belt (OChVB) during the Campanian–Maastrichtian (Koryak) to Middle Eocene (Olyutorskiy), respectively. To constrain the accretion paleolatitude of the Koryak superterrane, we paleomagnetically sampled a sedimentary series on the Mametchinskiy Peninsula. At the Mametchinskiy Peninsula, in the northeastern Penzhinskaya Guba (61.45° N, 163.75° E), a gently deformed, well-bedded section of fine-grained Lower to lower Upper Cretaceous turbidites, the Mametchinskaya and Tylakrylskaya Formations are exposed. These strata, which represent the lower part of the sedimentary cover of the terranes in this region and the forearc of OChVB, were sampled at 39 sites (three to seven samples per site). Within the Ainyn terrane, more than 1000 m of section of Cenomanian–Turonian age was sampled at a basal locality (sample groups I and II, sites 1–18, 19–29) and at an upper locality of Valanginian–Barremian age (sample group III, sites 30–39) along the western shore of the Peninsula. Thermal demagnetization and principal component analysis of the demagnetization data show lower-temperature (A) and higher-temperature (B) magnetic components. Although group III samples did not display a coherent A component, the A component of group I and II samples was observed as a single-polarity lower-unblocking temperature component generally removed by 100–400 °C. This component failed the fold test at the 95% confidence level. With respect to direction, the A component is similar to both the present-day field and axial–geocentric dipole directions expected at this site. The B component was observed during thermal demagnetization steps up to 580 °C and was always of downward-directed inclination. Coherence of bedding corrections within each section do not allow statistically meaningful fold tests within groups I, II or III. Assuming the B component represents a Cretaceous magnetization, two overall models are proposed. In the first model (preferred), with the highest clustering of directions (k-value=36.7, N (sites)=36), indicates significant poleward motion of the Ainyn terrane (observed paleolatitude λM1=61.0±6.5°; expected North America plate reference site paleolatitude λE=74.0±3.5°). In the second model, no significant poleward displacement is implied (λM2=72.0±9.6). 相似文献
997.
Mathematical Geosciences - This paper introduces a novel method using an adaptive functional basis for reduced order models based on proper orthogonal decomposition (POD). The method is intended to... 相似文献
998.
The responses of Spartina alterniflora above- and belowground biomass to various combinations of N, P, and Fe were documented in a 1-year field experiment in a
Louisiana salt marsh. Five levels of N additions to 0.25 m2 plots resulted in 18% to 138% more live aboveground biomass compared to the control plots and higher stem densities, but
had no effect on the amount of live belowground biomass (roots and rhizomes; R&R). There was no change in the aboveground
biomass when P or Fe was added as part of a factorial experiment of +P, +N, and +Fe additions, but there was a 40% to 60%
decrease in the live belowground biomass, which reduced the average R&R:S ratio by 50%. The addition of various combinations
of nutrients had a significant affect on the belowground biomass indicating that the addition of P, not N, eased the need
for root foraging activity. The end-of-the-growing-season N:P molar ratios in the live above- and belowground tissues of the
control plot was 16.4 and 32.7, respectively. The relative size of the belowground standing stocks of N and P was higher than
in the aboveground live tissues, but shifted downwards to about half that in fertilized plots. We conclude that the aboveground
biomass was directly related to N availability, but not P, and that the accumulation of belowground biomass was not limited
by N. We suggest that the reduction in belowground biomass with increased P availability, and the lower absolute and relative
belowground standing stocks of P as plant tissue N:P ratios increased, is related to competition with soil microbes for P.
One implication for wetland management and restoration is that eutrophication may be detrimental to long-term salt marsh maintenance
and development, especially in organic-rich wetland soils. 相似文献
999.
Breanyn T. MacInnes Tatiana K. Pinegina Joanne Bourgeois Nadezhda G. Razhigaeva Victor M. Kaistrenko Ekaterina A. Kravchunovskaya 《Pure and Applied Geophysics》2009,166(1-2):9-36
The near-field expression of the tsunami produced by the 15 November 2006 Kuril earthquake (Mw 8.1–8.4) in the middle Kuril Islands, Russia, including runup of up to 20 m, remained unknown until we conducted a post-tsunami survey in the summer of 2007. Because the earthquake occurred between summer field expeditions in 2006 and 2007, we have observations, topographic profiles, and photographs from three months before and nine months after the tsunami. We thoroughly surveyed portions of the islands of Simushir and Matua, and also did surveys on parts of Ketoi, Yankicha, Ryponkicha, and Rasshua. Tsunami runup in the near-field of the middle Kuril Islands, over a distance of about 200 km, averaged 10 m over 130 locations surveyed and was typically between 5 and 15 m. Local topography strongly affected inundation and somewhat affected runup. Higher runup generally occurred along steep, protruding headlands, whereas longer inundation distances occurred on lower, flatter coastal plains. Sediment transport was ubiquitous where sediment was available—deposit grain size was typically sand, but ranged from mud to large boulders. Wherever there were sandy beaches, a more or less continuous sand sheet was present on the coastal plain. Erosion was extensive, often more extensive than deposition in both space and volume, especially in areas with runup of more than 10 m. The tsunami eroded the beach landward, stripped vegetation, created scours and trim lines, cut through ridges, and plucked rocks out of the coastal plain. 相似文献
1000.
Acoustic Emissions Monitoring during Inelastic Deformation of Porous Sandstone: Comparison of Three Modes of Deformation 总被引:4,自引:0,他引:4
Jerome Fortin Sergei Stanchits Georg Dresen Yves Gueguen 《Pure and Applied Geophysics》2009,166(5-7):823-841
In some reservoirs, large deformations can occur during oil or gas production because of the effective stress change. For very porous rocks, these production operations can be sufficient to cause inelastic deformation and irreversible damage. Rock formations can undergo deformation by different mechanisms, including dilatancy or pore collapse. In the laboratory, it has been shown that the inelastic deformation and failure mode of porous rocks are pressure sensitive. Indeed, when subjected to an overall compressive loading, a porous rock may fail by shear localization, compaction localization, or by cataclastic compaction. Acoustic emission (AE) records provide important information to understand the failure mode of rocks: the spatial evolution of damage as well as the source mechanisms can be followed using this technique. In this paper, we present three different laboratory axisymmetric compression experiments, performed on Bleurswiller sandstone, which enable us to compare the acoustic emission signature of these three modes of deformation. Our data show that compaction localization and cataclastic compaction are characterized by similar acoustic signatures (in terms of AE sources characteristics and evolution of AE number), in comparison to the acoustic signature from shear localization. This implies similar micromechanisms involved during compaction bands formation and cataclastic compaction. 相似文献