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911.
《International Journal of Digital Earth》2013,6(9):1067-1082
ABSTRACTThe aim of this paper was to study reliable automated delineation possibilities of karst sinkholes using a LiDAR-based digital terrain model (DTM) with pixel-based classifications. We applied two approaches to extract sinkholes: (1) general linear modeling (GLM) with morphometric indices derived from DTM; (2) and a local minima-based delineation using only LiDAR DTM as the input layer. The outcome of the local minima was significantly different from the reference ones but found all the sinkholes without previous knowledge of the area. The GLM-based outcome did not differ statistically from the reference. Results showed that these approaches were ef?cient in detecting sinkholes based on LIDAR derivatives, and can be used for risk assessment and hazard preparedness in karst areas: GLM had an overall accuracy of 89.5% and local minima had an accuracy of 92.3%; both methods identified sinkholes but also had commission errors, identifying depressions as sinkholes. 相似文献
912.
The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential
(SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground
surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater
flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures
or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of
southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and
noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction
factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient
(R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation
for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data
revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is
coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as
evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove
the existence of concentrated groundwater recharge activity.
Received: 18 March 1998 · Accepted: 27 April 1998 相似文献
913.
济南南部山区是山东喀斯特洞穴发育地区之一,所统计的34个中,长度在50~500 m的较大洞穴有7个.从洞穴发育的基本特征看,较大的洞穴多呈单通道水平廊道状,洞内保留有许多典型的溶蚀小形态(如窝穴、波痕类),但洞内沉积物较为单一,主要是一些崩积物、残积物和渗流水造成的碎屑物,碳酸钙化学沉积物相对较少,溶洞多表现为一种单调的干洞特点.从成因上看:较大洞穴属于具有潜流成因的次生渗流带洞穴;较小洞穴有裂隙状的渗流带洞穴、差异风化成因的壁龛式洞穴等.这些洞穴具有较大的开发潜力. 相似文献
914.
A review of natural sinkhole phenomena in Italian plain areas 总被引:2,自引:0,他引:2
Italian sinkholes, which are mainly related to karst phenomena (i.e., solution sinkholes, collapse sinkholes, etc.), are widespread
along the Apennine ridge and in pedemontane areas where there are carbonatic bedrock outcrops. However, other collapses, which
seem unrelated to karst dissolution, have been identified in plain areas with a thick sedimentary cover over buried bedrock.
The main goal of this work is to study the geological, geomorphological, and structural setting of these areas to identify
the possible mechanism of the generation and evolution of these collapses. About 750 cases were identified by research based
on historical archives, specific geological literature, and information from local administrations. Geological, geomorphological,
and hydro-geochemical surveys were conducted in 300 cases, supported by literature, borehole, and seismic data. A few examples
were discarded because they could be ascribed to karst dissolution, volcanic origin (i.e., maar), or anthropogenic causes.
Field studies regarding the other 450 cases are in progress. These cases occur along the Tyrrhenian margin (Latium, Abruzzo,
Campania, Tuscany) in tectonic, coastal, and alluvial plains close to carbonate ridges. These plains are characterized by
the presence of pressurized aquifers in the buried bedrock, overlaid by unconsolidated sediments (i.e., clay, sands, pyroclastic
deposits, etc.). The majority of these collapses are aligned along regional master and seismogenetic faults. About 50% of
the studied cases host small lakes or ponds, often characterized by highly mineralized springs enriched with CO2 and H2S. The Periadriatic margin does not seem to be affected by these phenomena, and only a few cases have been found in Sicily,
Sardinia, and Liguria. The obtained scenarios suggests that this type of collapse could be related to upward erosion through
vertical conduits (i.e., deep faults) caused by deep piping processes whose erosive strength is increased by the presence
of acidic fluids. In order to distinguish these collapses from typical karst dissolution phenomena, they are defined as deep
piping sinkholes (DPS). 相似文献
915.
Rapid degradation of disturbed soil from a karst bauxite mine in Jamaica was recorded. Substantial macronutrient losses were
incurred during a short (1 month) or a long (12 months) storage of the replaced topsoils during frequent wet/dry changes.
The results suggested very high rates (>70% in the first year) of soil degradation from storage, alongside moderate rates
(30%) within the same storage dump. However, higher levels of soil organic matter (SOM) were indicated just below the surface,
compared with the surface horizons. It was unlikely that under a high leaching humid tropical rainfall regime, natural degradation
processes could have re-emplaced such material firmly intact in the 15–30 cm zone. It was therefore concluded that these SOM
anomalies were due to mechanical dilution of surface soil with subsoil material during overburden removal and emplacement
rather than from long storage. Increasing the soil organic content during storage could be one corrective approach. However,
it is far less costly to exercise greater care to apply more precise overburden removal and emplacement techniques initially,
than it is to correct the results of topsoil contamination with subsoil. Although this study was limited to one mine, in the
context of imminent large-scale mining expansion and current practices, further investigations are needed to accurately ascertain
the proportion of similar subsoil contamination in other bauxite-mined sites. 相似文献
916.
Presence of springs in karst terranes provides a unique opportunity to study the rather complex, multi-porosity, and multi-permeability
system. When springs are used to evaluate the integrity of storage facilities for hazardous materials or waste disposal facilities
constructed in karst areas, the spatial heterogeneity of karst aquifers makes intra-spring comparisons preferred statistical
tests. One of the commonly used statistical tests is water quality control procedure such as Shewhart-CUSUM control charts.
Appropriate application of the water quality control procedure to intra-spring monitoring depends on whether the assumptions
can be justified about the aquifer that drains to the spring and the dataset collected at the spring. Violation of the assumptions
would render the statistical tests invalid, which may result in a failure of the groundwater monitoring program. In intra-spring
monitoring, it is the temporal variations of water quality at a karst spring need to be addressed, whereas the water quality
at the spring is closely associated with the characteristics of the aquifer. The example datasets presented in the paper indicate
that both false negative and false positive detections can occur if the temporal variation is not well characterized. 相似文献
917.
Groundwater sensitivity (Ray and O’dell in Environ Geol 22:345–352, 1993a) refers to the inherent ease with which groundwater can be contaminated based on hydrogeologic characteristics. We have developed
digital methods for identifying areas of varying groundwater sensitivity for a ten county area of south central Kentucky at
a scale of 1:100,000. The study area includes extensive limestone karst sinkhole plains, with groundwater extremely sensitive
to contamination. Digitally vectorized geologic quadrangles (DVGQs) were combined with elevation data to identify both hydrogeologic
groundwater sensitivity regions and zones of “high risk runoff” where contaminants could be transported in runoff from less
sensitive to higher sensitivity (particularly karst) areas. While future work will fine-tune these maps with additional layers
of data (soils for example) as digital data have become available, using DVGQs allows a relatively rapid assessment of groundwater
sensitivity for Kentucky at a more useful scale than previously available assessment methods, such as DRASTIC and DIVERSITY.
Geographic definitions: United States of America, Kentucky, Barren River Area Development District. 相似文献
918.
By sampling in the field and analyzing the soil samples in the laboratory in 1982 and 2005 the soil fertility data were obtained.
Through application of geo-statistics combined with GIS, the temporal–spatial variability of the pH, organic matter, total
nitrogen, total phosphorus and total potassium in soil of Xiaojiang watershed from 1982 to 2005 were analyzed. Results showed
that: (1) the pH value and total potassium in soil showed an increasing trend, but the organic matter, total nitrogen and
the total phosphorus in soil declined in the past 20 years in Xiaojiang watershed, (2) the parameters fitted by semivariogram
models for fertility indices changed significantly in the past 20 years and (3) the result estimated by ordinary Kriging indicated
the spatial pattern of the soil fertility indices changed significantly in the past 20 years. The soil pH increased in the
east and southeast, but decreased in the middle of the watershed. The organic content of the soil matter decreased in the
east, southeast and southwest, but increased in the northeast and middle of the watershed. The total nitrogen content of the
soil decreased in the east, but increased in the middle of watershed. The total phosphorus content of the soil decreased in
the whole watershed. The total potassium content of the soil increased in the southwest and southeast, but decreased in the
middle of the watershed and (4) the change of land use and soil management measures was the main driving force of variability
of soil properties. 相似文献
919.
The applicability of resistivity methods to ground water investigations is well recognized. As water-saturated rock formations
have a lower electrical resistivity than dry ones, an electrical resistivity survey should result in low resistivity anomalies. Normally, such anomalies are interpreted to indicate areas of potentially significant ground water flows. In karst areas,
however, interpretation may not be as straightforward: for example, large electrically conductive domains can represent water bearing zones, whose fluid-permeability may be poor; alternatively, fast flow conduits, which
may be unsaturated, occur as slender objects, and not as clear anomalous features. In order to deal with such extreme heterogeneities,
resistivity investigations require some specific adjustments. One example is the so-called “mise à la masse” method. In Romania,
it was used to trace the cold karst water inflows that detrimentally affected the commercial exploitation of a thermal spring,
Hercules at Baile Herculane. Conventional geoelectrical approaches––such as using resistivity highs to detect air-filled cave passages,
are proved to be less efficient in the considered karst investigations. 相似文献
920.
Juan Reynerio Fagundo-Castillo Joel José Carrillo-Rivera Iñaki Antigüedad-Auzmendi Patricia González-Hernández Roberto Peláez-Díaz Rebeca Hernández-Díaz Dámaso Cáceres-Govea José Ramón Hernández-Santana Margaret Suárez-Muñoz Clara Melián-Rodríguez Mónica Rodríguez-Piña 《Environmental Geology》2008,55(2):247-267
Flows of different hierarchy, which travel through limestone, schist, sandstone and ultra-basic rocks, with ages from the
Paleocene to the Jurassic, at Sierra del Rosario, Pinar del Río, Cuba, were characterized. The waters were sampled from 1984
until 2004 and the data were statistically processed by means of chemical equilibrium and physico-chemical models, under a
flow system view of interpretation. Results demonstrate that the physico-chemical properties of the water are controlled by
water–rock interaction resulting from residence time since rainwater infiltrate and the path it follows to the discharge zone
and the type of aquifer material the different groundwater flows are in contact with. Geochemical indices allow the definition
of the different types of flow (local, intermediate, regional) to be characterized, permitting a further definition of the
different flow systems and rock type involved, as well as its use for water supply and medical use. The main geochemical processes
which control the chemical composition acquisitions mode are: congruent dissolution of calcite, dolomite, and halite; incongruent
dissolution of plagioclase and microcline minerals; pyrite oxidation, sulphate reduction, and silica dissolution at the surface
or silica precipitation at deep saturation and circulation zones. 相似文献