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David Washington Daniel Rodriguez Vincent Ogunro 《Geotechnical and Geological Engineering》2011,29(1):13-17
The monitoring operation of an older impoundment (such as dams and waste barrier materials) during the service life of the
structure cannot be overemphasized. Since older infrastructures seem to be more susceptible to piping and seepage failure,
their construction design should be analyzed and monitored at places where a potential problem could occur. Once an impoundment
is constructed without adequate filters layers and foundation treatments, then the prevention of piping or seepage may require
an effective approach to constructing a cut-off wall to prevent eventual failure. In order to identify and understand theses
failure modes, it is important to identify the physical parameters of the impoundment system, such as the zones of various
soil gradations, the compaction of these zones, the hydraulic conductivity, the compatibility of the soil formations within
and beneath the core or liner, as well as the cohesive and dispersive properties of soils at various location within the structure.
Once these parameters are known and quantified, an adequate assessment of the structure’s susceptibility to piping or contaminant
transport can be established. This type of an analysis will enable the proper design of a cut-off wall and predetermine the
effectiveness of its long-term performance. The Vermont Waterbury Dam (built in 1938) is example of seepage related problem
that implemented a cut-off wall design to prevent piping paths from undermining the structure. In this case, some forensic
sampling had to be performed and the parameters of the soils as just mentioned were key factors in determining the wall design.
In this paper, the Waterbury dam rehabilitation is investigated as case studies, in order to better understand how older designs
and poor construction of impoundments can lead to piping condition in dams as well as failures in waste barrier systems. The
Secant Cut-off wall (constructed at Waterbury Dam) is mentioned as a corrective measure taken for this dam and there is a
brief discussion as to how this construction rehabilitation technique can be applied to waste barrier impoundments. 相似文献
4.
Javier Tomasella Laura S. Borma José A. Marengo Daniel A. Rodriguez Luz A. Cuartas Carlos A. Nobre Maria C. R. Prado 《水文研究》2011,25(8):1228-1242
Severe hydrological droughts in the Amazon have generally been associated with strong El Niño events. More than 100 years of stage record at Manaus harbour confirms that minimum water levels generally coincide with intense warming in the tropical Pacific sea waters. During 2005, however, the Amazon experienced a severe drought which was not associated with an El Niño event. Unless what usually occurs during strong El Niño events, when negative rainfall anomalies usually affect central and eastern Amazon drainage basin; rainfall deficiencies in the drought of 2005 were spatially constrained to the west and southwest of the basin. In spite of this, discharge stations at the main‐stem recorded minimum water levels as low as those observed during the basin‐wide 1996–1997 El Niño‐related drought. The analysis of river discharges along the main‐stem and major tributaries during the drought of 2004–2005 revealed that the recession on major tributaries began almost simultaneously. This was not the case in the 1996–1997 drought, when above‐normal contribution of some tributaries for a short period during high water was crucial to partially counterbalance high discharge deficits of the other tributaries. Since time‐lagged contributions of major tributaries are fundamental to damp the extremes in the main‐stem, an almost coincident recession in almost all tributaries caused a rapid decrease in water discharges during the 2005 event. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
William A. Watkins Mary Ann Daher Joseph E. George David Rodriguez 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1889-1901
A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones. 相似文献
6.
Patrick Berrebi Pascal Rodriguez Jean-Antoine Tomasini Ghislaine Cattaneo-Berrebi Alain J. Crivelli 《Estuarine, Coastal and Shelf Science》2005,65(4):708-716
The presence and the distribution of two cryptic sedentary gobies, Pomatoschistus microps and Pomatoschistus marmoratus, were investigated in several lagoons stretching along the Golfe du Lion, southern France Mediterranean coast, and Corsica. Pomatoschistus microps is the only sedentary Pomatoschistus species in two shallow lagoons with large variations of salinity and temperature. In contrast, P. marmoratus, another sedentary species, can be found preferentially in a deep salty lagoon with small salinity variations. Both species occur sympatrically in the Rhone Delta and hybridise, producing fertile offspring. Using allozymes, competition, linked to fitness, is invoked to explain the distribution pattern of these sibling species. 相似文献
7.
We use perturbation theory in the strong-field regime to study the inspiral-to-plunge transition of a test particle into a Kerr black hole. We found a smooth transition, without burst, and with lower energy and angular momentum radiated in gravitational waves with respect to previous treatments in the literature. Besides their theoretical interest, our results are relevant for the waveform templates of binary black hole mergers used for gravitational waves detection which are constructed on the basis of a inspiral-to-plunge transition with a high energetic burst. 相似文献
8.
Bulletin of Earthquake Engineering - In past decades, multistory housing buildings have been constructed in high-seismic-risk regions in Latin America using thin reinforced concrete (RC) walls as... 相似文献
9.
F. Rodriguez Monreal H.J. Villar R. Baudino D. Delpino S. Zencich 《Marine and Petroleum Geology》2009
In the Altiplanicie del Payún area (Neuquen Basin, Argentina), immature source rock sections intruded by up to 600 m thick Tertiary laccoliths show full spectrum maturity aureoles over hundreds of meters from the contacts. Commercial oil accumulations (20–33°API) and oil shows are located along the entire column, both in sandstone/carbonate and fractured igneous reservoirs. A challenging numerical model that included the emplacement of the intrusive bodies, with extreme temperature ranges and unusually short calculation time steps, has been done with the aim to better understand hydrocarbon generation and migration processes related to these thermal anomalies. 相似文献
10.
Temporal and cross-shelf distribution of ichthyoplankton in the central Cantabrian Sea 总被引:1,自引:0,他引:1
Environmental variables have been measured and sampling for ichthyoplankton has been conducted monthly, since April 2001, at three stations, located at the inner (1), middle (2) and outer (3) shelf of the central Cantabrian Sea. This paper presents the results of the study of the ichthyoplankton collected from July 2001 to June 2004. Fish larvae from 99 species, belonging to 37 families, were identified. Families with higher number of species were Gadidae, Sparidae and Labridae. The larval fish assemblage was dominated by pelagic fish species, with Sardina pilchardus, as the most abundant. There was a pronounced spring peak in larval abundance, dominated by S. pilchardus. A smaller peak, dominated by S. pilchardus and Micromesistius poutassou, was recorded in late winter at Stns 2 and 3. This pattern was evident for the three-year study. Results also indicate that this study was limited to the coastal larval fish assemblage inhabiting the central Cantabrian Sea shelf. This assemblage was temporally structured into other three assemblages: winter, late winter–spring and summer–autumn. Temperature was apparently a key factor in larval fish assemblage succession. In a scenario of global warming, this study constitutes a basis to evaluating the ongoing changes in the pelagic coastal ecosystem of the central Cantabrian Sea. 相似文献