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81.
Mm-wave spectra of HDO in the Venus mesosphere (65-100 km) were obtained over the period March 1998 to June 2004. Each spectrum is a measurement of the hemispheric-average H2O vapor mixing ratio in the Venus mesosphere. Observations were conducted for wide ranges of Venus solar elongations (46° W to 47° E), and fractional disk illuminations (f=0% to 99%), yielding water vapor abundances on 17 dates and over a full range of local solar time (LST) at the sub-Earth point on Venus. Our mesopheric H2O values are more numerous and far more precise than the earliest mm-derived H2O measurements [Encrenaz, Th., Lellouch, E., Paubert, G., Gulkis, S., 1991. First detection of HDO in the atmosphere of Venus at radio wavelengths: An estimate of the H2O vertical distribution. Astron. Astrophys. 246, L63-L66; Encrenaz, Th., Lellouch, E., Cernicharo, J., Paubert, G., Gulkis, S., Spilker, T., 1995. The thermal profile and water abundance in the Venus mesosphere from H2O and HDO millimeter observations. Icarus 117, 162-172], allowing an analysis of variability that was previously impossible. Measured 65-100 km H2O ranged from 0.0±0.06 to 3.5±0.3 ppmv, with significantly different variability than found in previous infrared (lower altitude, cloudtop) studies. Strong global variability on a 1-2 month timescale is clear and unambiguous. A limited number of excellent s/n measurements tentatively indicate the 1-2 month variability manifests most rapidly as change in the lower mesosphere, and more slowly as change in the upper mesosphere. Neither long term (1998-2004) nor diurnal variability in 65-100 km H2O is evident. While six-year and/or diurnal variabilities are not ruled out, they are weaker than the 1-2 month timescale variation. These conclusions are supported by initial (2004) sub-mm measurements. 相似文献
82.
Groundwater-dependent, spring-fed ecosystems of the Cuatrociénegas Basin, Coahuila, Mexico, host >70 endemic species. These
desert springs occur primarily aligned along the base of an anticline that bisects the Cuatrociénegas Basin, but the hydrogeologic
controls of the springs are poorly understood. The hypothesis that spring locations are controlled by subsurface geology,
such as buried anticlines or faulting, versus stratigraphic controls is tested by evaluating: (1) regional structural styles;
(2) fracture models of analogous structures; (3) hydrogeologic data; and (4) geophysical surveys. Jurassic and Cretaceous
siliciclastic and carbonate rocks deposited on the Coahuila Block west of the Cuatrociénegas Basin have dips <10° and lack
faults because of a structurally rigid granodiorite basement. To the east of the Coahuila Block and around the Cuatrociénegas
Basin, the Coahuila Folded Belt has anticlines associated with basement-involved faults, 10–25° backlimb dips, and forelimb
dips up to vertical or slightly overturned. Springs in the western sub-basin that represent 85% of total basin discharge are
located on zones of highest anticipated fracture density predicted by fracture models of analogous anticlines. Spring waters
reveal elevated temperature (32–35°C) and low tritium (<1 tritium unit). Gravimetry and time-domain electromagnetic surveys
correspond with a best-fit Cuatrociénegas Basin hydrogeologic model of fractures associated with reverse faulting controlling
spring locations in the western Cuatrociénegas Basin. Springs in the eastern sub-basin are located where ephemeral streams
have eroded through confining beds along the base of alluvial fans and lack faulting. Regional variations in structural style
are an important control on the location of springs in the Cuatrociénegas Basin. 相似文献
83.
Janne Holopainen Chris Flynn Alexander Knebe Stuart P. Gill Brad K. Gibson 《Monthly notices of the Royal Astronomical Society》2006,368(3):1209-1222
Using eight dark matter haloes extracted from fully self-consistent cosmological N -body simulations, we perform microlensing experiments. A hypothetical observer is placed at a distance of 8.5 kpc from the centre of the halo measuring optical depths, event durations and event rates towards the direction of the Large Magellanic Cloud. We simulate 1600 microlensing experiments for each halo. Assuming that the whole halo consists of massive astronomical compact halo objects (MACHOs), f = 1.0 , and a single MACHO mass is m M = 1.0 M⊙ , the simulations yield mean values of τ= 4.7+5.0 −2.2 × 10−7 and Γ= 1.6+1.3 −0.6 × 10−6 events star−1 yr−1 . We find that triaxiality and substructure can have major effects on the measured values so that τ and Γ values of up to three times the mean can be found. If we fit our values of τ and Γ to the MACHO collaboration observations, we find f = 0.23+0.15 −0.13 and m M = 0.44+0.24 −0.16 . Five out of the eight haloes under investigation produce f and m M values mainly concentrated within these bounds. 相似文献
84.
Matt Rovero Diana Cutt Rachel Griffiths Urszula Filipowicz Katherine Mishkin Brad White Sandra Goodrow Richard T. Wilkin 《Ground Water Monitoring & Remediation》2021,41(4):62-75
Published literature for reported sorption coefficients (Kd) of eight anionic per- and polyfluoroalkyl substances (PFAS) in soil was reviewed. Kd values spanned three to five log units indicating that no single value would be appropriate for use in estimating PFAS impacts to groundwater using existing soil-water partition equations. Regression analysis was used to determine if the soil or solution parameters might be used to predict Kd values. None of the 15 experimental parameters collected could individually explain variability in reported Kd values. Significant associations between Kd and soil calcium and sodium content were found for many of the selected PFAS, suggesting that soil cation content may be critical to PFAS sorption, as previously noted in sources like Higgins and Luthy (2006), while organic carbon content was significant only at elevated levels (>5%). Unexplained discrepancies between the results from studies where PFAS were introduced to soil and desorbed in the laboratory and those that used material from PFAS-impacted sites suggest that laboratory experiments may be overlooking some aspects critical to PFAS sorption. Future studies would benefit from the development and use of standardized analytical methods to improve data quality and the establishment of soil parameters appropriate for collection to produce more complete data sets for predictive analysis. 相似文献
85.
To integrate lessons from the U.S. Department of Agriculture (USDA), National Institute of Food and Agriculture–Conservation Effects Assessment Project (NIFA CEAP) program, key informant (KI) interviews were conducted in all 13 project areas. The purpose of these interviews was to supplement technical information about watersheds, their contaminants, modeling, economics, and key findings. We interviewed a wide range of people to develop a systematic look at individual project results, synthesize meanings, and derive principles useful in guiding future watershed management. Findings revealed common themes, which tended to align with KI categories, regardless of location. For instance, farmers and ranchers often understood water quality problems as well as federal and state personnel and university employees do. Conservation adoption by farmers was related to perceived need, cost, and convenience of the practice, as well as practice specifics and individual situations. Possible implications of these findings are advanced. 相似文献
86.
Weighted linear combination is a multi-criteria decision analysis technique that can be used by decision-makers to select an optimal location from a collection of alternative locations. Its local form takes into account the range of attribute values within a user-defined neighbourhood in accordance with the range-sensitivity principle. This research explores locally weighted linear combination in a vector-based geographic information system. A custom application in ArcGIS 10 allows the user to select a neighbourhood definition from a standard set including contiguity, distance, and k-nearest neighbours, for which local weights are generated. A case study on vulnerability to heat-related illness in Toronto is used to illustrate the technique. The impact of local weighting on the heat vulnerability index is examined using visual analysis of the spatial patterns of heat vulnerability under the global and local approaches, as well as the sensitivity of the local approach to the selected neighbourhood definition. A trade-off analysis of the local weights is also presented. The combination of socio-demographic and environmental determinants in a locally weighted index results in patterns of heat vulnerability that could support targeted hot weather response at a micro-geographic level within urban neighbourhoods. 相似文献
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Brad M. Angel Stuart L. Simpson Chad V. Jarolimek Rob Jung Jorina Waworuntu Grant Batterham 《Marine pollution bulletin》2013
The Batu Hijau copper–gold mine on the island of Sumbawa, Indonesia operates a deep-sea tailings placement (DSTP) facility to dispose of the tailings within the offshore Senunu Canyon. The concentrations of trace metals in tailings, waters, and sediments from locations in the vicinity of the DSTP were determined during surveys in 2004 and 2009. In coastal and deep seawater samples from Alas Strait and the South Coast of Sumbawa, the dissolved concentrations of Ag, As, Cd, Cr, Hg, Pb and Zn were in the sub μg/L range. Dissolved copper concentrations ranged from 0.05 to 0.65 μg/L for all depths at these sites. Dissolved copper concentrations were the highest in the bottom-water from within the tailings plume inside Senunu Canyon, with up to 6.5 μg Cu/L measured in close proximity to the tailings discharge. In general, the concentrations of dissolved and particulate metals were similar in 2004 and 2009. 相似文献