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991.
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
992.
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
993.
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
994.
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
995.
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
996.
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
997.
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998.
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
999.
We have compared near-fault ground motions from TeraShake simulations of Mw7.7 earthquake scenarios on the southern San Andreas Fault with precariously balanced rock locations. The TeraShake scenarios
with different directions of rupture generate radically different ground motions to the northwest of the Los Angeles Basin,
primarily because of directivity effects, and thus provide constraints on the ground motion and rupture direction for the
latest (1690) large event on that section of the San Andreas Fault. Due to the large directional near-field ground motions
predicted by the simulations, we expect the precariously balanced rocks to be located primarily in the backward rupture direction
or near the epicenter. Preliminary results favor persistent nucleation at or slightly northwest of the San Gorgonia Pass fault
zone for large earthquakes on the southern San Andreas Fault. 相似文献
1000.
Influence of climate variation on seasonal precipitation in the Colorado River Basin 总被引:1,自引:1,他引:0
Tae-Woong Kim Chulsang Yoo Jae-Hyun Ahn 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(3):411-420
This study analyzed the influence of large-scale climate pattern on precipitation in the Colorado River Basin. Large-scale
climatic oscillations, like ENSO, PDO, NAO, and the global warming trend are associated with regional hydrologic variation.
Ten types of climate indices were gathered and analyzed to investigate their influence on seasonal precipitation variation
in the basin based on a linear correlation analysis and an influence index analysis. The influence index was developed in
this study to measure the effect of climate variation on the seasonal precipitation in the basin. The statistical evidence
achieved in this study confirms that the Colorado River Basin is subjected to the phase of climate variation. The strength
of the seasonal response of precipitation to the climate variation varies in different localities in the basin. The methods
of analysis used in this study were proposed in the hope that progress in understanding and modeling dynamic climatic systems
can result in developing a valuable long-term forecasting model for water resources management. 相似文献