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131.
Natural Hazards - Using daily precipitation data from 25 meteorological stations for a period of 1961–2014, spatiotemporal features of wet spells and droughts and related impacts on... 相似文献
132.
Yu Zhou Qiang Zhang Vijay P. Singh Mingzhong Xiao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(3):665-677
Correlation associations have been detected using Pearson’s r which aims to analyze linear correlation between two variables. It should be noted here that associations between hydro-meteorological variables are usually nonlinear. In this sense, the classical correlation analysis method cannot truly reflect the inherent associations between variables characterized by nonlinear associations. In this case, a new algorithm has been proposed by using the ideas of local correlation, detrended cross-correlation analysis and multifractals, and this novel algorithm is called as the general detrended correlation analysis. The newly-proposed algorithm was evaluated for the validity with numerically-generated time series and the real world hydrological series. The results indicate that the newly-proposed algorithm can well reflect the nonlinear and non stationary associations between two hydrological series when compared to the classical relation detection method such as the Pearson correlation analysis method, and it is particularly the case under the condition that hydrological abrupt changes of the hydrological processes occur where the classical association analysis is not appropriate. 相似文献
133.
Riverbank filtration (RBF) is a proven treatment step in a multi-barrier method of drinking-water supply at many sites. RBF wells induce a large amount of river water to infiltrate the river base and travel towards the wells, giving the opportunity for mixing of infiltrated surface water and groundwater. Assessment of raw water quality plays an important role in planning and operating a RBF well field. In this context, the determination of the catchment area (and land uses within the catchment) and the ratio of bank filtrate (BF) to raw groundwater (GW) are two prior steps. Transient model simulations were performed in order to study the hydraulic conditions at the RBF well field at Grind near Düsseldorf, Germany. The BF/GW ratio was determined to be 75/25. The flood events in winter, in particular, showed the BF/GW ratio to have high variation. Transient path lines in the well field were used for delineation of the catchment area. 相似文献
134.
135.
Vijay S. Tripathi 《Geochimica et cosmochimica acta》1979,43(12):1989-1990
The necessity of considering protonation and complexation of weak acid ligands, for proper interpretation of their effect on solution equilibria, has been demonstrated. The solubility of uraninite in presence of σF = 2 ppm has been recalculated to be 0.88 ppb at pH 2. 相似文献
136.
Vijay P. Singh 《Journal of Hydrology》1976,30(3):247-255
An analytical treatment is developed for the step error of some finite-difference schemes that are frequently used to solve the kinematic wave equations. It is shown that for convergent and stable schemes, the production of step error of one scheme may not be the same as that of another. This distinction must be considered in choosing between the schemes. Knowledge of step error is a useful parameter to estimate apriori the step length to be used in a given scheme. 相似文献
137.
Various characteristics of anomalous nighttime enhancement in ionospheric electron content (IEC) at Lunping (14.08°N geomagnetic), a station near the crest of the equatorial anomaly, have been presented by considering the IEC data for the 21st solar cycle. Out of a total of 1053 enhancements, 354 occur in pre-midnight and 699 occur in post-midnight hours, which indicates an overall dominance of post-midnight events at Lunping. The occurrence is more frequent during summer, less during the equinox and least during winter months. All the characteristics of the enhancements have seasonal dependencies and they reach their maximum values during summer months. The occurrence of the pre-midnight events show positive and post-midnight events show negative correlation with solar activity. The results have been discussed and compared with those at low-latitude stations in India and Hawaii and at the mid-latitude station, Tokyo. 相似文献
138.
139.
Extremes of stream flow and precipitation are commonly modeled by heavytailed distributions. While scrutinizing annual flow
maxima or the peaks over threshold, the largest sample elements are quite often suspected to be low quality data, outliers
or values corresponding to much longer return periods than the observation period. Since the interest is primarily in the
estimation of the right tail (in the case of floods or heavy rainfalls), sensitivity of upper quantiles to largest elements
of a series constitutes a problem of special concern. This study investigated the sensitivity problem using the log-Gumbel
distribution by generating samples of different sizes (n) and different values of the coefficient of variation by Monte Carlo experiments. Parameters of the log-Gumbel distribution
were estimated by the probability weighted moments (PWMs) method, method of moments (MOMs) and maximum likelihood method (MLM),
both for complete samples and the samples deprived of their largest elements. In the latter case, the distribution censored
by the non-exceedance probability threshold, F
T
, was considered. Using F
T
instead of the censored threshold T creates possibility of controlling estimator property. The effect of the F
T
value on the performance of the quantile estimates was then examined. It is shown that right censoring of data need not reduce
an accuracy of large quantile estimates if the method of PWMs or MOMs is employed. Moreover allowing bias of estimates one
can get the gain in variance and in mean square error of large quantiles even if ML method is used. 相似文献
140.
Mohammad Ethteram Sayed-Farhad Mousavi Hojat Karami Saeed Farzin Ravinesh Deo Faridah Binti Othman Kwok-wing Chau Saeed Sarkamaryan Vijay P. Singh Ahmed El-Shafie 《Environmental Earth Sciences》2018,77(13):510
Optimizing reservoir operation rule is considered as a complex engineering problem which requires an efficient algorithm to solve. During the past decade, several optimization algorithms have been applied to solve complex engineering problems, which water resource decision-makers can employ to optimize reservoir operation. This study investigates one of the new optimization algorithms, namely, Bat Algorithm (BA). The BA is incorporated with different rule curves, including first-, second-, and third-order rule curves. Two case studies, Aydoughmoush dam and Karoun 4 dam in Iran, are considered to evaluate the performance of the algorithm. The main purpose of the Aydoughmoush dam is to supply water for irrigation. Hence, the objective function for the optimization model is to minimize irrigation deficit. On the other hand, Karoun 4 dam is designed for hydropower generation. Three different evaluation indices, namely, reliability, resilience, and vulnerability were considered to examine the performance of the algorithm. Results showed that the bat algorithm with third-order rule curve converged to the minimum objective function for both case studies and achieved the highest values of reliability index and resiliency index and the lowest value of the vulnerability index. Hence, the bat algorithm with third-order rule curve can be considered as an appropriate optimization model for reservoir operation. 相似文献