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101.
Port Phillip Bay receives the industrial and domestic effluents from Melbourne and a recent survey revealed an accumulation of a variety of heavy metals in bottom sediments. These studies have now been extended to survey the accumulation in oysters and mussels, and in most areas in the Bay these bivalves are heavily contaminated with cadmium. Oysters accumulate more of this metal than mussels. 相似文献
102.
The concentrations of214Pb (half-life=26.4minutes) and22Rn (half-life=3.84days) have been measured in deep groundwaters of Gujarat, India. The results show that the abundance of214Pb in the water is only ~25% of that expected from its production through the radioactive decay of dissolved222Rn. This deficiency if modelled in terms of a first-order removal, yields a residence time of ~10 minutes for214Pb in these waters. The estimated residence time for214Pb is the shortest observed for any nuclide in natural water systems and suggests that reactive nuclides lead like could be removed from aqueous phases to adjoining solid surfaces on extremely short time scales. Results of laboratory experiments using the212Pb-224Ra pair are compatible with the observed fast removal of214Pb from groundwaters.Re-evaluation of234Th residence times in these waters using a model with a recoil flux of234Th into aqueous phase, the same as that of222Rn, yields values in the range of 23 to<176 minutes, very similar to that of214Pb. This “concordancy” in the residence times seems to suggest that the geochemical behaviour of234Th and214Pb in these waters is quite similar. 相似文献
103.
Kirsten M. Menking Roger Y. Anderson Nabil G. Shafike Kamran H. Syed Bruce D. Allen 《Quaternary Research》2004,62(3):174-288
Well-preserved shorelines in Estancia basin and a relatively simple hydrologic setting have prompted several inquiries into the basin's hydrologic balance for the purpose of estimating regional precipitation during the late Pleistocene. Estimates have ranged from 86% to 150% of modern, the disparity largely the result of assumptions about past temperatures. In this study, we use an array of models for surface-water runoff, groundwater flow, and lake energy balance to examine previously proposed scenarios for late Pleistocene climate. Constraints imposed by geologic evidence of past lake levels indicate that precipitation for the Last Glacial Maximum (LGM) may have doubled relative to modern values during brief episodes of colder and wetter climate and that annual runoff was as much as 15% of annual precipitation during these episodes. 相似文献
104.
An approach based on the behaviour of human genome is developed to efficiently provide a general framework for optimizing
the use of space technology in surveying networks design. The developed approach attempts to apply the successful self-organizing
principles based upon the biological evolution to artificial intelligence. It mimics the phenomena of natural selection observed
in nature to achieve its goals by continuously adopting a population of candidate solutions and improving its performance
over successive generations. The goal of adaptation is to find the best solution that optimizes the design of a surveying
network based on the use of satellite observations. This network can be defined as a set of stations, co-ordinated by a series
of sessions formed by placing receivers on the stations. The problem is to search for the best order for observing these sessions
to give the best observation schedule at minimum cost. The obtained results prove the effectiveness of the developed technique
in term of solution quality and computational efforts.
The Corresponding Author in formed me that his address is likely to change soon. Please contact me, leick@spatial.maine.edu
for the latest on this change. 相似文献
105.
Genotype and environment interaction effect on yield of cotton under naturally salt stress condition
Y. Ali Z. Aslam F. Hussain 《International Journal of Environmental Science and Technology》2005,2(2):169-173
Thirteen genotypes of cotton developed through hybridization and mutation breeding techniques were evaluated during two consecutives years 2002-03-04 on eight locations covering most of the area of Punjab province including Faisalabad, Toba Tek Singh and Jhang. The eight sets of experiments were conducted in the naturally highly saline sodic soils, EC ranges from 7.8–36.1 d/Sm, pH=8.1–8.8, SAR=10.1–40.5, Saturation percentage 31.3–40.8 and texture Sandy Clay loam and Clay loam. The seed yield data was collected at maturity and stability parameters were computed to know genotypic environment interaction and varietals performance. The combined analysis of variance showed highly significant variance in case of varieties, locations and varieties x environment (Lin) also showed highly significant differences. It means that genotypes exhibited different behavior in different locations/environments which is due to their different genetic make up. The behavior may be cross over (in which significant change in ranking order occurs from one environment to another) or cross over nature (in which case the ranking of genotypes remains constant across environments and the interaction is significant because of change in the magnitude of response) depending upon the ranking order of genotypes performance under different environments. In our study only S-12 behavior was of almost non cross over nature, while others had cross over type of interaction. Based on over all seed yield cotton variety NIAB-999 and CIM-707 produced highest seed yield cotton (3.2 t/ha, 3.17t/ha). The lowest seed yield cotton was noted in S-12 (1.86 t/ha). All the three parameters of stability i.e. overall mean seed yield cotton, regression coefficient and standard deviation to regression provided clear evidence that variety NIAB-999 and CIM-707 produced maximum stable yield compared to S-12. 相似文献
106.
B.S. Sukhija D.V. Reddy P. Nagabhushanam Syed Hussain V.Y. Giri 《Hydrogeology Journal》1996,4(2):70-88
In order to mine lignite from the Neyveli opencast mines, about 200 km south of Madras, India, the Neyveli aquifer has been undergoing depressurisation continuously for almost three decades. To gain insight into the aquifer hydrodynamics, environmental-isotope and chloride measurements on selected groundwater samples were initiated two decades ago, and detailed studies were undertaken during 1985–91. This article demonstrates the effect of large-scale groundwater withdrawals on the hydrologic regime and the effects on environmental chloride and isotopic distributions. A feature common to both the radiocarbon and chloride data of 1991 is their marked variation in a small area between the recharge zone and the mine area where pumping is concentrated. Furthermore, an excellent correlation exists between the temporal increase in the apparent radiocarbon ages of groundwater sampled in 1991 and 1985 and the corresponding lowering of potentiometric levels. Isochlors based on 1991 and 1985 data also indicate a changed hydrologic regime. In certain areas, heavy withdrawals have resulted in increased groundwater salinity. 相似文献
107.
The mechanism of222Rn release into fracture fluids by direct alpha-recoil, lattice and grain boundary/micro-crack diffusion is discussed. Experimental measurements of222Rn release into surrounding air and water phases have been made for crystalline rock specimens with well defined surface areas. The222Rn flux from an infinite plane surface and hence the effective diffusion length of222Rn in the rock matrix has been estimated.The222Rn flux from plane crystalline rock surfaces has been used in conjunction with a simple hydrological model of the reservoir to calculate the222Rn content of the return fluids of a geothermal doublet circulation system. For given production rate and piezometric difference between the injection and production wells, the222Rn content of the return fluid is dependent upon the distribution of flow path lengths and fracture apertures in the reservoir. Matching of the calculated and experimental222Rn contents of the return fluids has been used to select appropriate parameters for the reservoir model and hence to estimate the extent of the heat-transfer surface. The model estimates the fracture width of the flow paths, total swept surface area and fracture volume within the reservoir. 相似文献
108.
The rare earth element patterns of the gneisses of Bastar and Bundelkhand are marked by LREE enrichment and HREE depletion
with or without Eu anomaly. The spidergram patterns for the gneisses are characterized by marked enrichment in LILE with negative
anomalies for Ba, P and Ti. The geochemical characteristics exhibited by the gneisses are generally interpreted as melts generated
by partial melting of a subducting slab. The style of subduction was flat subduction, which was most common in the Archean.
The rare earth patterns and the multi-element diagrams with marked enrichment in LILE and negative anomalies for Ba, P and
Ti of the granitoids of both the cratons indicate interaction between slab derived melts and the mantle wedge. The subduction
angle was high in the Proterozoic. Considering the age of emplacement of the gneisses and granitoids that differs by ∼ 1 Ga,
it can be assumed that these are linked to two independent subduction events: one during Archaean (flat subduction) that generated
the precursor melts for the gneisses and the other during the Proterozoic (high angle subduction) that produced the melts
for the granitoids. The high values of Mg #, Ni, Cr, Sr and low values of SiO2 in the granitoids of Bastar and Bundelkhand cratons compared to the gneisses of both the cratons indicate melt-mantle interaction
in the generation of the granitoids. The low values of Mg#, Ni, Cr, Sr and high values of SiO2 in the gneisses in turn overrules such melt-mantle interaction. 相似文献
109.
Study of groundwater recharge processes is vital for quantification of total natural recharge to the aquifers. One of the
recharge processes demonstrated earlier by tracer experiments in the unsaturated zone is that of piston flow movement of soil
moisture. Based on this recharge process, environmental tritium, chloride and injected tritium studies have been carried out
extensively in various geological environs of India. The purpose of this paper is to evaluate the validity of the piston flow
concept in different geological environs viz. consolidated fractured and weathered granites, semi-consolidated sandstones
and unconsolidated alluvial tracts, and quantify the contribution from this process as well as that from the preferential
flow mechanism using different tracers. Analysis of tracer data demonstrates that the preferential flow recharge process contributes
very significantly (an average of 75% of total recharge) in the case of fractured granites and is important (an average of
33% of total recharge) for semi-consolidated sandstones, whereas the preferential flow recharge component is minimal in unconsolidated
alluvial tracts (piston flow model is applicable). These findings necessitate re-evaluation of the total natural recharge
potential of the above mentioned geological environs in view of the significant preferential flow recharge that is evidenced
and estimated.
Electronic Publication 相似文献
110.
Communicating human health risks associated with disinfection by-products in drinking water supplies: a fuzzy-based approach 总被引:1,自引:2,他引:1
Rehan Sadiq Manuel J. Rodriguez Syed A. Imran Homayoun Najjaran 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):341-353
Chlorine used for the disinfection of water supplies can react with naturally occurring organic compounds and form potentially
harmful disinfection by-products (DBPs). A risk index for two regulated groups of chlorinated DBPs—trihalomethanes (THMs)
and haloacetic acids (HAAs), using fuzzy C-means (FCM) clustering algorithm and fuzzy rule-based modeling is proposed for risk communication. The proposed index evaluates
the cancer and non-cancer risks individually for THMs and HAAs using the FCM algorithm. Subsequently, two different fuzzy
rule-bases were used to evaluate the overall risk-index based on cancer and non-cancer risks. The overall risk-index will
provide drinking water utilities with an effective communication tool for communicating aggregated water quality compliance.
Simulated DBP occurrence data obtained from the City of Quebec, Canada, is used to demonstrate the application of this methodology. 相似文献