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11.
A general infiltration model proposed by Singh and Yu (1990) was calibrated and validated using a split sampling approach for 191 sets of infiltration data observed in the states of Minnesota and Georgia in the USA. Of the five model parameters, fc (the final infiltration rate), So (the available storage space) and exponent ‘n’ were found to be more predictable than the other two parameters: m (exponent) and a (proportionality factor). A critical examination of the general model revealed that it is related to the Soil Conservation Service (1956) curve number (SCS‐CN) method and its parameter So is equivalent to the potential maximum retention of the SCS‐CN method and is, in turn, found to be a function of soil sorptivity and hydraulic conductivity. The general model was found to describe infiltration rate with time varying curve number. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
12.
This study investigated the effect of urbanization on runoff from the On-Cheon Stream watershed in Pusan, Korea. This watershed has been experiencing considerable urbanization since the 1960s. There are two gauging stations in the watershed. For one of the stations there are recent flow data and for the other flow data were observed in the past. A linear reservoir model was chosen and runoff was analysed for several flood events. The linear reservoir model has been found to generate flood hydrographs accurately for both gauging stations, and its applicability to the study area has also been established. Using two methods of computing effective rainfall or rainfall excess (ϕ-index and constant percentage method), the results of runoff analyses were investigated. The ϕ-index method yielded better results than the constant percentage method. A comparison of hydrographs observed in the past with the simulation results at the Ie-Sup bridge site revealed that the peak discharge increased and the mean lag time of the study area decreased owing to urbanization over the past two decades. It is also possible to evaluate the effect of urbanization quantitatively. © 1998 John Wiley & Sons, Ltd. 相似文献
13.
A simple model describing the transformation of effective rainfall to direct runoff through the overland flow mechanism is presented. The model is based on the classical representation of a watershed by a combination of planes and channels. The dynamics of overland flow in each plane is simulated by the non-linear kinematic wave, but the outflow from a given plane is concentrated in the middle of the corresponding drainage channel. The water routing in the channels is carried out by a piece-wise linearized formulation in space of the kinematic wave approximation. Using synthetic events on 10 watersheds, the model was tested by comparing it with results obtained by applying the non-linear kinematic wave to all the elements of the watershed. The model was found to be adequate, even in a form that simplifies the geometric features of the planes through an averaging procedure based on the Horton–Strahler ordering scheme of the watershed. © 1998 John Wiley & Sons, Ltd. 相似文献
14.
Hysteresis represents a loop in a rating curve and is a phenomenon which closely resembles that occurring in stress–strain curves used for studying the elastic properties of solid substances in engineering mechanics. Earlier hysteresis‐based studies used for defining floodwave propagation in open channels have qualitatively shown that hysteresis is an index of energy loss during floodwave propagation. Using the concept of elasticity, this paper introduces a new term called flow strain (defined as the ratio of change in discharge to the initial discharge) for investigating hysteresis. The usefulness of this new term is evaluated with use of four dam‐break studies. The study reveals that:
- 1 flow strain is a function of three wave speeds, Seddon speed, Lagrange speed, and elastic speed;
- 2 a single linear reservoir concept frequently used in flood routing is a specific variant of the Seddon speed formula;
- 3 the non‐linear storage–discharge relationship, widely used in overland flow modelling, is a variant of the kinematic wave representation;
- 4 the discharge ordinates on the recession part of a hydrograph follow a simple first‐order autoregressive form;
- 5 the hysteresis, phase difference and logarithmic decrement all define attenuation and are indices of energy loss during floodwave propagation.
15.
Ionospheric scintillation observations of VHF radio signals from FLEETSAT satellite (73°E longitude) at Bhopal from January
1990 to December 1990 have been used to study the characteristic variations of scintillation activity. It is found that scintillation
occurrence is essentially a night-time phenomenon and day-time scintillations are very rare. Annual average nocturnal variation
of percentage occurrence of scintillations shows maximum at around 2100–2200 hours LT. Seasonally, scintillations are most
prominent during equinoxes and least during summer. Geomagnetic disturbances tend to decrease the occurrence of scintillations
in the pre-midnight period. 相似文献
16.
Coral microatolls were examined from North Andaman and Little Andaman to understand the relative sea level change due to vertical
tectonic deformation above the subduction interface. The highest level of survival of coral microatoll before the 26 December,
2004 earthquake at eastern coast of North Andaman has been determined by Global Ocean Tide Model. The present position of
recently dead flat top microatoll with preserved internal structure at the eastern coast of North Andaman mainland indicates
31.21 cm uplift due to the 26 December, 2004 earthquake. Comparatively old cup shaped microatoll at the eastern fringe of
North Andaman group of islands and highly bioeroded fossil microatolls at the intertidal zone of Little Andaman bear the signature
of permanent vertical deformation in the past. 相似文献
17.
SPI-based evaluation of drought events in Xinjiang, China 总被引:4,自引:1,他引:4
Daily precipitation data for 1957?C2009 from 53 stations in the Xinjiang, China, are analyzed, based on the Standardized Precipitation Index (SPI) with the aim to investigate spatio-temporal patterns of droughts. The Mann?CKendall trend test is used to detect the trends in the SPI values of monthly drought series, drought severity and drought duration. The frequencies of moderate, severe and extreme droughts are higher in the North Xinjiang, while mild droughts occur more often in the South Xinjiang. A decreasing frequency of droughts in the North Xinjiang is found in winter, but a drying tendency is detected in the western parts of the North Xinjiang during spring, summer and autumn, which may be harmful for agriculture. The South Xinjiang seems to be getting wetter in summer, while the south parts of the South Xinjiang seem to be getting drier in spring. The middle of the East Xinjiang is identified to be in a slightly dry tendency. The drought severity is decreasing and drought duration is getting shorter in the North Xinjiang, while both of them increase in the southern parts of the South Xinjiang. In addition, droughts in the middle parts of the East Xinjiang are intensifying. 相似文献
18.
Qiang Zhang Vijay P. Singh Xiaohong Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(4):569-579
Using updated hydrological datasets from three stations, including Cuntan, Yichang and Hankou, covering the period of January
1992–December 2008, the influence of Three Gorges Dam (TGD) on streamflow and sediment load of the Yangtze River was investigated.
Results indicated that TGD did not seem to exert a significant influence on streamflow occurring at three stations and changes
in streamflow can be mainly attributed to streamflows of tributaries. However, a sharp decrease in the sediment load after
the impoundment of TGD was observed. Clear water after the impoundment caused erosion of riverbed and resulted in more sediment
at the Hankou station than at the Yichang station. No distinct changes in the annual and monthly maximum sediment loads were
observed before and after the impoundment. Therefore, annual and monthly maximum sediment load changes should be subjected
mainly to river hydraulics. This study has practical relevance for understanding the influence of large hydraulic structures
on the hydrological processes of large rivers. 相似文献
19.
This article describes the impact of satellite altimeter data on the simulations of sea level variability (SLV) by a nonlinear reduced gravity model of the entire Indian Ocean. The model has been forced by 6-hourly analyzed wind stress data containing SSM/I observations and has been able to produce realistic circulation features. However, SLV values observed by Topex/Poseidon altimeter do not fit these simulations because of imperfect initial data. Hence an attempt has been made to initialize the model using altimeter data. The initialized model-generated SLVvalues have been compared with SLV derived by altimeter for monsoon as well as nonmonsoon months of 1996. Experimental runs have been performed for 10 days, 20 days, and one month. It has been found that the initialized model results on the final day of these experiments are in very good agreement with altimeter data of the same day. It is thus possible, in principle, to hindcast and forecast sea level variations in the time scale of 10 days to one month with the availability of good quality wind data for forcing the model and altimeter observations of sea level for initializing it. 相似文献
20.
This article describes the impact of satellite altimeter data on the simulations of sea level variability (SLV) by a nonlinear reduced gravity model of the entire Indian Ocean. The model has been forced by 6-hourly analyzed wind stress data containing SSM/I observations and has been able to produce realistic circulation features. However, SLV values observed by Topex/Poseidon altimeter do not fit these simulations because of imperfect initial data. Hence an attempt has been made to initialize the model using altimeter data. The initialized model-generated SLVvalues have been compared with SLV derived by altimeter for monsoon as well as nonmonsoon months of 1996. Experimental runs have been performed for 10 days, 20 days, and one month. It has been found that the initialized model results on the final day of these experiments are in very good agreement with altimeter data of the same day. It is thus possible, in principle, to hindcast and forecast sea level variations in the time scale of 10 days to one month with the availability of good quality wind data for forcing the model and altimeter observations of sea level for initializing it. 相似文献