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991.
992.
993.
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
994.
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
995.
Physicochemical characteristics relevant to the adsorption of MTBE and Cd on three types of clay minerals were investigated.
The characteristics were examined through batch adsorption tests conducted under various experimental conditions such as adsorption
time, ratio of solution-to soil, concentration of solutes, concentration of organic matters, pH, and zeta potential. The adsorption
efficiency of MTBE or Cd on three types of clays decreased in response to an increase of the ratio of solution-to-soil; nevertheless,
the adsorbed amounts inversely increased. MTBE was adsorbed on clays in an increasing order of vermiculite, bentonite, and
CTAB-bentonite. However, Cd was adsorbed in a different order of bentonite, vermiculite, and CTAB-bentonite. The adsorption
of MTBE was well fitted with the Freundlich model, whereas the Cd was more closely suited to a Langmuir equation. By adding
humic acids of 1 and 5%, MTBE was significantly adsorbed on bentonite and vermiculite, respectively, but beyond that, its
adsorption was diminished. In comparison, the adsorption on CTAB-bentonite was increased in proportion to the humic acids
addition. Likewise, the addition of humic acids acted to increase the adsorption of Cd regardless of the types of adsorbent,
where up to 90% of Cd was removed at pH 10. Further increase of pH declined the degree of zeta potential, while increasing
Cd concentration also lowered the zeta potential, which consequently contributes in enhancing the adsorption efficiency of
Cd on clays. 相似文献
996.
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
997.
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
998.
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
999.
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
1000.
Yoko Furukawa Janet L Watkins Jinwook Kim Kenneth J Curry Richard H Bennett 《Geochemical transactions》2009,10(1):2-11