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381.
Spatial and temporal variation of diverse inter‐tidal algal assemblages in Southwest O‘ahu 下载免费PDF全文
Spatial and temporal variation in tropical inter‐tidal communities is poorly known, making predictions about the effects of climate change and other anthropogenic disturbances difficult. Along Southwest O‘ahu, Hawai'i, local residents are concerned about the environmental effects of coastal development and the perceived loss of targeted algal species, which are collected for human consumption. To describe the coastal benthic community and better understand the processes that form and maintain it, the abundance and composition of macroalgae were sampled in the region's inter‐tidal zone from 2006 to 2015. Sixty‐six macroalgal species and two broad algal assemblages were identified that corresponded to substrate topography and sand influence at a similar tidal elevation. Along flat carbonate benches with a sand beach, Phaeophyceae and Rhodophytes occurred in almost equal proportions, while shores with slightly more topographic relief and angular substrate were dominated by Rhodophytes. Foliose or turf algal forms were most common. Surveys captured the local invasion of an alga, Avrainvillea sp. and significant declines in abundant macroalgae in 2015 after a period of unseasonably warm, calm water. Temporal changes in algal assemblages were related to maximum water temperature and wave height but not precipitation. Thus, algal assemblages appear to be structured by local beach morphology as they interact with sand and wave activity and episodically by unusual weather events. However, manipulation and continuous monitoring of the algal assemblages coupled to sensing of the localized environment is necessary to confirm factors related to assembly maintenance and recent species shifts. 相似文献
382.
The Australian SKA Pathfinder (ASKAP) is a new radio-telescope being built in Western Australia. One of the key surveys for
which it is being built is EMU (Evolutionary Map of the Universe), which will make a deep (∼10 μJy/bm rms) radio continuum survey covering the entire sky as far North as +30°. EMU may be compared to the NRAO VLA Sky Survey
(NVSS), except that it will have about 45 times the sensitivity, and five times the resolution. EMU will also have much better
sensitivity to diffuse emission than previous large surveys, and is expected to produce a large catalogue of relics, tailed
galaxies, and halos, and will increase the number of known clusters by a significant factor. Here we describe the EMU project
and its impact on the astrophysics of clusters. 相似文献
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Abstract. The 1984 Ohio Supreme Court ruling on Cline v. American Aggregates changed Ohio's ground-water law from an 1861 ruling based on the English Rule of absolute ownership to a doctrine of reasonable use which recognizes that landowners have the privilege to use the water beneath their land but can be held liable to others if their use of ground water causes others unreasonable harm. The Ohio Supreme Court did not define unreasonable harm in the Cline case. As a result, unreasonable harm is being established through case law, the first such case being the relitigation of Cline v. American Aggregates.
Depositions and expert testimony presented during the Cline cases, which represent a group of 56 landowners in a single lawsuit, showed the diverse ways in which the quantity and quality of ground water used for domestic-water supplies were affected by operation of a dewatering system at an aggregate mine. The testimony highlighted the complex interaction between regional hydrodynamics, variations in local hydrogeologic settings, well-construction methods, spatial variations in infiltration and recharge, and vertical leakage with the effects of the regional decline in water levels produced by the dewatering system. 相似文献
Depositions and expert testimony presented during the Cline cases, which represent a group of 56 landowners in a single lawsuit, showed the diverse ways in which the quantity and quality of ground water used for domestic-water supplies were affected by operation of a dewatering system at an aggregate mine. The testimony highlighted the complex interaction between regional hydrodynamics, variations in local hydrogeologic settings, well-construction methods, spatial variations in infiltration and recharge, and vertical leakage with the effects of the regional decline in water levels produced by the dewatering system. 相似文献
387.
Dane Quinn Brett Gladman Phil Nicholson Richard Rand 《Celestial Mechanics and Dynamical Astronomy》1997,67(2):111-130
We study the rotational evolution under tidal torques of axisymmetric natural satellites in inclined, precessing orbits. In
the spin- and orbit-averaged equations of motion, we find that a global limit cycle exists for parameter values near the stability
limit of Cassini state
. The limit cycle involves an alternation between states of near-synchronous spin at low obliquity, and strongly subsynchronous
spin at an obliquity near 90°. This dynamical feature is characterized as a relaxation oscillation, arising as the system
slowly traverses two saddle-node bifurcations in a reduced system. This slow timescale is controlled by ε, the nondimensional
tidal dissipation rate. Unfortunately, a straightforward expansion of the governing equations for small ε is shown to be insufficient
for understanding the underlying structure of the system. Rather, the dynamical equations of motion possess a singular term,
multiplied by ε, which vanishes in the unperturbed system. We thus provide a demonstration that a dissipatively perturbed
conservative system can behave qualitatively differently from the unperturbed system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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D.?H.?PhillipsEmail author A.?O.?Thomas K.?Forde K.?Dickson S.?Plant G.?Norris B.?Bone R.?M.?Kalin 《Environmental Geology》2007,52(6):1117-1131
Volatile organic compound (VOC) contamination of subsurface geological material and groundwater was discovered on the Nortel
Monkstown industrial site, Belfast, Northern Ireland. The objectives of this study were to (1) investigate the characteristics
of the geological material and its influences on contaminated groundwater flow across the site using borehole logs and hydrological
evaluations, and (2) identify the contaminants and examine their distribution in the subsurface geological material and groundwater
using chemical analysis. This report focuses on the eastern car park (ECP) which was a former storage area associated with
trichloroethene (TCE) degreasing operations. This is where the greatest amount of volatile organic compounds (VOCs), particularly
TCE, were detected. The study site is on a complex deposit of clayey glacial till with discontinuous coarser grained lenses,
mainly silts, sands and gravel, which occur at 0.45–7.82 m below ground level (bgl). The lenses overall form an elongated
formation that acts as a small unconfined shallow aquifer. There is a continuous low permeable stiff clayey till layer beneath
the lenses that performs as an aquitard to the groundwater. Highest concentrations of VOCs, mainly TCE, in the geological
material and groundwater are in these coarser lenses at ∼4.5–7 m bgl. Highest TCE measurements at 390,000 μg L−1 for groundwater and at 39,000 μg kg−1 at 5.7 m for geological material were in borehole GA19 in the coarse lens zone. It is assumed that TCE gained entrance to
the subsurface near this borehole where the clayey till was thin to absent above coarse lenses which provided little retardation
to the vertical migration of this dense non-aqueous phase liquid (DNAPL) into the groundwater. However, TCE is present in
low concentrations in the geological material overlying the coarse lens zone. Additionally, VOCs appear to be associated with
poorly drained layers and in peat <3.0 m bgl in the ECP. Some indication of natural attenuation as VOCs degradation products
vinyl chloride (VC) and dichloromethane (DCM) also occur on the site. 相似文献
390.
Thomas B. McCord Paul Hayne Jean-Philippe Combe Jason W. Barnes Stéphane Le Mouélic Bonnie J. Buratti Philip Nicholson Robert Nelson the Cassini VIMS Team 《Icarus》2008,194(1):212-242
The surface composition of Titan is of great importance for understanding both the internal evolution of Titan and its atmosphere. The Visual and Infrared Mapping Spectrometer (VIMS) investigation on Cassini is observing Titan from 0.35 to 5.11 μm with spatial resolution down to a few kilometers during each flyby of the spacecraft as it orbits Saturn. Our search for spectral diversity using seven methane transmission windows in the near infrared suggests that spectrally distinct units exist on the surface of Titan and that most of the surface can be modeled using only a few distinct spectral units: water frost, CO2 frost, atmospheric scattering, and an unknown material bright at 2 μm. A dark, spectrally neutral material is also implied. Use of an atmospheric scattering component with spectral mixing analysis may provide a method for partially removing atmospheric effects. In some locations, atmospheric scattering accounts for the majority of the signal. There are also small regions with unusual spectra that may be due to low signal and high noise and/or may be exotic materials of interest. Further, we searched within the methane windows for spectral features associated with Titan's surface. Only the 5-μm and, to a lesser extent, the 2-μm window provide a reasonable opportunity for this, as the shorter-wavelength windows are too narrow and the 2.8-μm window is cluttered with an unknown atmospheric constituent. We find evidence for only one spectral feature: near 4.92 μm for the 5-μm bright Tui Regio region. CO2 frost with grains smaller than about 10 μm is the best candidate we have found so far to explain this absorption as well as the feature's spectral contrast between the 2.7- and the 2.8-μm atmosphere subwindows. This suggested CO2 identification is supported by the presence of an endmember in the spectral mixture analysis that is consistent with CO2 frost with large grain sizes. We find no other absorption features that are statistically significant, including those reported earlier by others. These results are consistent with but greatly extend our early analysis that treated only the Ta data set [McCord, T.B., et al., 2006a. Planet. Space Sci. 54, 1524-1539]. In the spectral feature search process, we explored in detail the noise characteristics of the VIMS data within the 5-μm window, which has generally very low signal (4-20 DN), due to the measurement conditions and low illumination levels. We find noise of nearly Gaussian statistics except for some erratic darks and noise spikes, and the data set seems generally well behaved. We present examples of our attempt to improve on the standard VIMS pipeline data calibration. 相似文献