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991.
992.
The contamination of marine sediments by five antifouling agents was analysed to examine the changes in the coasts of Korea which were caused by the use of alternative antifouling agents. The average concentrations of chlorothalonil, dichlofluanid, Irgarol 1051 and SEA-NINE(TM) 211 were 10.4, 0.2, 54.5 and 19.2 ng/g, respectively. TCMTB was below detection limits in all sampling sites. In terms of average concentrations, Irgarol 1051 and SEA-NINE(TM) 211 accounted for 87.4% of the total marine sediments contamination; these two substances have been used in Korea at higher rates than other antifouling agents. Irgarol 1051 and SEA-NINE(TM) 211 were also represented by the same factor in the factor analysis, possibly because they are used exclusively as antifouling agents and not as herbicides in Korea. Chlorothalonil and dichlofluanid, found as the second and third factor, respectively, were considered to be affected by not only antifoulants, but also other pollution sources such as pesticides. Thus, the management of Irgarol 1051 and SEA-NINE(TM) 211 and the management of chlorothalonil and dichlofluanid were separately conducted. 相似文献
993.
National-scale assessment of landslide susceptibility to rank the vulnerability to failure of rock-cut slopes along expressways in Korea 总被引:1,自引:1,他引:1
Jangwon Suh Yosoon Choi Tae-Dal Roh Hyi-Jun Lee Hyeong-Dong Park 《Environmental Earth Sciences》2011,63(3):619-632
The objective of this study is to perform a preliminary national-scale assessment of the landslide susceptibility of rock-cut slopes along expressways in Korea. A geographic information system (GIS) database was compiled based on data from topographical and geological maps, and rock-cut slope data, including the locations of past landslides. Seven factors (i.e., slope height, slope length, slope gradient, upper slope gradient, lithology, distance from nearest fault, and dip direction of slope) were extracted from the GIS database to assess the relationship between each factor and landslide events. Weight of evidence (WOE), analytic hierarchy process (AHP), and fuzzy logic methods, as well as hybrid methods, were used to establish the rating of classes for each factor, weightings for the factors, and to combine multiple factor layers into landslide-susceptibility maps. A comparison of the results obtained using several different methods, based on the area under curve technique, revealed that the WOE method showed the highest accuracy of 74%. The annual cost of traffic congestion resulting from slope failures was evaluated to identify those rock-cut slopes where detailed investigations and landslide warning systems are required. 相似文献
994.
995.
Hydrochemistry of urban groundwater in Seoul, South Korea: effects of land-use and pollutant recharge 总被引:1,自引:0,他引:1
Byoung-Young Choi Seong-Taek Yun Soon-Young Yu Pyeong-Koo Lee Seong-Sook Park Gi-Tak Chae Bernhard Mayer 《Environmental Geology》2005,48(8):979-990
The ionic and isotopic compositions (δD, δ18O, and 3H) of urban groundwaters have been monitored in Seoul to examine the water quality in relation to land-use. High tritium contents
(6.1–12.0 TU) and the absence of spatial/seasonal change of O–H isotope data indicate that groundwaters are well mixed within
aquifers with recently recharged waters of high contamination susceptibility. Statistical analyses show a spatial variation
of major ions in relation to land-use type. The major ion concentrations tend to increase with anthropogenic contamination,
due to the local pollutants recharge. The TDS concentration appears to be a useful contamination indicator, as it generally
increases by the order of forested green zone (average 151 mg/l), agricultural area, residential area, traffic area, and industrialized
area (average 585 mg/l). With the increased anthropogenic contamination, the groundwater chemistry changes from a Ca–HCO3 type toward a Ca–Cl(+NO3) type. The source and behavior of major ions are discussed and the hydrochemical backgrounds are proposed as the basis of
a groundwater management plan. 相似文献
996.
This paper presents the results of a physical model study of the performance of landfill clay cover liners subjected to extended freezing periods. Three proposed designs for a prototype cover liner were evaluated with a primary objective being the determination of frost penetration resulting from the sub-freezing temperatures imposed as an upper boundary condition to the model. The ultimate performance of the three liner designs were compared on the basis of frost penetration, leakage through the liner, and frost heave. The observed depth of frost penetration was compared to that predicted using a simplified analytical solution of the thermodynamic problem, in addition to measured field behavior.
The laboratory experiment utilizes a 1.8 m2 tank, of ca 2.1 m depth. The tank is loaded with clay to the specifications required for landfill liners. Three different landfill cover liner designs were modeled in the experimental tank. The performance of the three designs, as measured by a variety of observations, were compared. Frost heave was measured for each design and was found to vary between 3.8 and 4.3 cm. The results indicate the depth of frost penetration was similar for all designs tested (29.2–31.7 cm), although the design which included a soil drainage layer had superior leakage performance. 相似文献
997.
The Mohr–Coulomb (M–C) failure criterion is one of the most widely used failure criteria in rock mechanics, although it has a number of shortcomings such as neglecting the nonlinear strength observed in rock or the effect of the intermediate principal stress σ 2. Other failure criteria have been proposed to effectively include in the predictions of failure the non-linear response of rock to confinement or the effects of the intermediate principal stress. The M–C criterion is still widely used, and it is arguably the criterion most used in practice. For example, stability evaluations of shallow rock structures such as slopes and foundations are routinely carried out by estimating a friction angle and a cohesion of the rock mass. To include the dependency of cohesion and friction angle on stresses, efforts are being made to estimate equivalent values of the M–C parameters for the range of stresses applicable to a particular design. The paper suggests a new and convenient approach to find the equivalent friction angle and cohesion from any failure criterion that can be expressed in terms of the Nayak and Zienkiewicz’s stress invariants. To demonstrate the capabilities and application of the methodology, the new approach is applied to two failure criteria: the Hoek–Brown (H–B) criterion and the Hoek–Brown and Willam–Warnke (HB–WW) criterion, 2-D and 3-D failure criteria, respectively. Results from the new method, in terms of equivalent friction and cohesion for the H–B criterion, are exactly the same as the results obtained from Balmer’s theory, which confirms the validity of the new method. The predicted equivalent friction and cohesion for the HB–WW criterion show a dependency on σ 2, which does not occur for a 2-D failure criterion. 相似文献
998.
Chia-Chang Lin Li-Ting Lee Ling-Jung Hsu 《International Journal of Environmental Science and Technology》2014,11(3):831-838
This investigation evaluates the effectiveness of UV-365 nm/S2O8 2? process in degrading polyvinyl alcohol in aqueous solutions. The effects of pH, Na2S2O8 dosage, and temperature on the degradation efficiency of polyvinyl alcohol were studied. Under acidic conditions, the degradation efficiency of polyvinyl alcohol exceeded that under alkaline conditions. Additionally, a higher Na2S2O8 dosage and a higher temperature were associated with a higher degradation efficiency of polyvinyl alcohol. The degradation rates of polyvinyl alcohol followed a pseudo-first-order kinetic model. Moreover, the observed degradation rate coefficient increased from 0.0078 to 0.4081 min?1 when the temperature was increased from 10 to 55 °C. Also, the activation energy estimated using the observed degradation rate coefficients and the Arrhenius equation was 64 kJ/mol. At UV-365 nm, pH 3, an Na2S2O8 dosage of 0.06 g/L, a temperature of 55 °C, and an initial polyvinyl alcohol concentration of 20 mg/L, around 100 % of polyvinyl alcohol was degraded, indicating that UV-365 nm/S2O8 2? process has great potential in degrading polyvinyl alcohol in aqueous solutions. 相似文献
999.
Chen Chien-Yuan Chen Lien-Kuang Yu Fan-Chieh Lin Sheng-Chi Lin Yu-Ching Lee Chou-Lung Wang Yu-Ting Cheung Kei-Wai 《Natural Hazards》2008,47(2):245-261
Typhoon Haitang caused landfall on Taiwan during 15–21 July, 2005 and brought 2,279 mm of maximum cumulative rain with a maximum
intensity of 176 mm/h. The torrential rain was mainly distributed from the central mountain range to southern Taiwan and triggered
222 slopeland-related hazards. Among the hazard events, there were 17 debris flows, 157 cases of traffic cut-off, three large-magnitude
deep-seated landslides, and 10 villages isolated in the off-track mountainous areas. The debris flows initiated in southern
Taiwan were associated with torrential rain, short channel length (<2 km), and small basin area (<3 km2), and were speculated to be induced by flash flood. These flash flood-induced debris flows have a higher rainfall intensity-duration
threshold for initiation than in other areas. The deep-seated landslides, isolated villages due to traffic cut-off in off-track
mountain areas, and recurrent hazards in areas affected by the ML 7.6 Chi-Chi earthquake in 1999 are characteristics of slopeland hazards in Taiwan in recent years. One of the most urgently
needed mitigation strategies in response to slopeland hazards is the plan for enhancing self-rescue disaster resistance in
off-track mountainous villages in Taiwan. 相似文献
1000.
Landslide susceptibility mapping in the Damrei Romel area, Cambodia using frequency ratio and logistic regression models 总被引:24,自引:0,他引:24
This study applied, tested and compared a probability model, a frequency ratio and statistical model, a logistic regression to Damre Romel area, Cambodia, using a geographic information system. For landslide susceptibility mapping, landslide locations were identified in the study area from interpretation of aerial photographs and field surveys, and a spatial database was constructed from topographic maps, geology and land cover. The factors that influence landslide occurrence, such as slope, aspect, curvature and distance from drainage were calculated from the topographic database. Lithology and distance from lineament were extracted and calculated from the geology database. Land cover was classified from Landsat TM satellite imagery. The relationship between the factors and the landslides was calculated using frequency ratio and logistic regression models. The relationships, frequency ratio and logistic regression coefficient were overlaid to make landslide susceptibility map. Then the landslide susceptibility map was compared with known landslide locations and tested. As the result, the frequency ratio model (86.97%) and the logistic regression (86.37%) had high and similar prediction accuracy. The landslide susceptibility map can be used to reduce hazards associated with landslides and to land cover planning. 相似文献