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961.
962.
963.
Hongjoon Shin Taesoon Kim Sooyoung Kim Jun-Haeng Heo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(2):183-197
In this study, the parameter estimations for the 3-parameter generalized logistic (GL) distribution are presented based on
the methods of moments (MOM), maximum likelihood (ML), and probability weighted moments (PWM). The asymptotic variances of
the MOM, ML, and PWM quantile estimators for the GL distribution are expressed as functions of the sample size, return period,
and parameters. A Monte Carlo simulation was performed to verify the derived expressions for variances and covariances between
parameters and to evaluate the applicability of the derived asymptotic variances of quantiles for the MOM, ML and PWM methods.
The simulation results generally show good agreement with the analytical results estimated from the asymptotic variances of
parameters and quantiles when the shape parameter (β) of the GL distribution is between −0.10 and 0.10 for the MOM method and between −0.25 and 0.45 for the ML and PWM methods,
respectively. In addition, the actual sample variances and the root mean square error (RMSE) of asymptotic variances of quantiles
for various sample sizes, return periods, and shape parameters were presented. In order to evaluate the applicability of the
estimation methods to real data and to compare the values of estimated parameter, quantiles, and confidence intervals based
on each parameter estimation method, the GL distribution was fitted to the 24-h annual maximum rainfall data at Pohang, Korea. 相似文献
964.
Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia 总被引:1,自引:0,他引:1
Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive
exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water,
and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact.
An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes
and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes
of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line.
This explained the most visible processes taking place during the displacement. 相似文献
965.
Let {Z(s):s∈D⊆ℝ
d
} be a zero mean stationary random field observed at a finite number of locations. Lahiri (Sankhya Ser. A 65:356–388, 2003) proved spatial central limit theorems (CLT) for ∑
i=1
n
Z(s
i
) assuming a ‘nearly infill domain sampling’. Applications of his results depended on the underlying spatial sampling region
and the design in a complicated fashion. The main objective of this paper is to provide CLTs that could be applied easily
in practice. We present two main results assuming a ‘nearly infill domain sampling’ defined mainly in terms of dependence.
Theorem 1 establishes a CLT for ∑
i=1
n
Z(s
i
) and Theorem 2 is obtained mainly for applications to density estimates. We report on a simulation study for illustrating
a way of applying our results in practice. 相似文献
966.
Ch. U. Kim V. I. Mikhailov R. S. Sen Ye. P. Semenova 《Russian Journal of Pacific Geology》2009,3(5):412-423
A catalogue of aftershocks of the 2007 Nevelsk earthquake (M
w = 6.2) was prepared on the basis of the data from the local network of digital seismic stations established on the southern
part of Sakhalin Island. The parameters of the aftershock hypocenters were determined using the method of the seismic wave
travel time inversion. The errors in the determination of the coordinates of the seismic events were analyzed. The particularities
of the spatiotemporal distribution of the aftershocks in the source zone of the earthquake were established. It was shown
that a strong aftershock was a subsource earthquake with its own source zone. This explains the disagreement between the energetic
characteristics and the size of the aftershock zone of the Nevelsk earthquake. 相似文献
967.
Freshwater–saline water interactions were evaluated in a coastal region influenced by external forces including tidal fluctuations and seasonal rainfall variations. Five different coastal zones were considered on Jeju Island, South Korea, and electrical conductivity (EC) profiles from the monitoring wells were examined to identify the configuration of the freshwater–saline water interface. There appeared to be discrepancies among EC profiles measured at different points in time. To analyze the dynamic behavior of freshwater–saline water interactions, groundwater level measurements and multi-depth EC and temperature probes were used to obtain time-series data; the data showed that water level, EC and temperature were influenced by both tidal fluctuations and heavy rainfall. The effects of oceanic tide on EC and temperature differed with depth due to hydraulic properties of geologic formations. A spectral filter was used to eliminate the effects of tidal forces and provide information on the influence of heavy rainfall on water level, EC and temperature. Heavy rainfall events caused different patterns and degrees of variation in EC and temperature with depth. The time-series data of EC and temperature in the subsurface at various depths enable greater understanding of the interaction processes between fresh and saline water. 相似文献
968.
Dinoflagellate Cysts in Coastal Sediments as Indicators of Eutrophication: A Case of Gwangyang Bay,South Sea of Korea 总被引:1,自引:0,他引:1
Diatom densities in the surface water and dinoflagellate cysts in bottom sediments of Gwangyang Bay were studied to determine
changes in the phytoplankton community structure in response to anthropogenic eutrophication and to assess the use of dinoflagellate
cysts as indicators of coastal eutrophication. Our results show that, in nutrient-enriched environments, diatoms are particularly
benefited from the nutrients supplied and, as a consequence, heterotrophic dinoflagellates that feed on the diatoms can be
more abundant than autotrophic dinoflagellates. In short-core sediment records, a marked shift in autotrophic–heterotrophic
dinoflagellate cyst compositions occurred at a depth of approximately 9–10 cm corresponding to the timing of the 1970s industrialization
around Gwangyang Bay. This tentatively indicates that diatom and dinoflagellate communities here have undergone a considerable
change mainly due to increased nutrient loadings from both domestic sewage effluent and industrial pollution. Our study suggests
a possible potential use of dinoflagellate cysts in providing retrospective information on the long-term effects of coastal
eutrophication. 相似文献
969.
Yoko Furukawa Janet L Watkins Jinwook Kim Kenneth J Curry Richard H Bennett 《Geochemical transactions》2009,10(1):2-11
Background
The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu). 相似文献970.
Chulsang Yoo Ungtae Kim Kyoungjun Kim Keewook Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(2):143-157
In this study an equation for estimating the error involved in the areal average rain rate considering the inter-station correlation
was derived and applied for two cases: the first compared two storm events with different inter-station correlations, and
the second evaluated the seasonal variation of estimation error of monthly rainfall. Similar cases, but without considering
the rainfall seasonality, were also investigated for the comparison. This study was applied to the Geum River Basin with 28
rain gauge measurements, each having more than 30 years of rainfall data. A summary of the application results follows: (1)
When considering the inter-station correlation, the estimation error involved in the areal average rain rate became significantly
decreased proportional to the inter-station correlation. (2) The estimation error of monthly areal average rainfall showed
strong seasonality with high ones during the wet season and lower ones during the dry season. (3) The estimation error was
well proportional to the areal average rain rate as well as to its standard deviation. The ratio of estimation error to the
areal average rain rate itself was estimated to be about 0.1 for the case of assuming no inter-station correlations, but decreased
to 0.06 for the case of considering the inter-station correlations between measurements. (4) The relation between the standard
deviation of areal average rain rate and the estimation error became much stronger than that between the areal average rain
rate itself and the estimation error. The ratio of estimation error to the standard deviations of rain rate amount was estimated
to be about 0.2 for the case of assuming no inter-station correlations, but decreased to 0.1 for the case of considering the
inter-station correlations. This relation was found to be valid for any case of accumulation time such as in daily, monthly,
or annual rainfall data. 相似文献