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991.
Mustafa Basaran Gunay Erpul A. Ugur Ozcan Pieter Bogman Wim M. Cornelis Donald Gabriels 《Environmental Earth Sciences》2010,61(7):1375-1384
There are various types of the windblown sediment traps developed for wind tunnel and field studies. One of the main supports
expected from these traps is in measuring surface dust concentrations to appropriately derive flux equations. The measurement
performance and accuracy of a trap is very important and depends strictly upon the physical characteristics and the behaviors
of dust grains with air flows. This paper presents the measurement results of static pressure distribution (SPD) of wind flow
around Vaseline-coated slide (VCS) catchers with an aim of finding out whether or not particle trapping efficiency (η) of
the VCS is related to the SPD. The SPD was evaluated by a wind reduction coefficient (R
c) in a series of wind tunnel experiments with different VCS settings which have different attachment configurations on a pole.
Three VCS configurations were considered: a configuration on a circular plastic pole (CPP) and two configurations on wooden
square poles (WSP1 and WSP2, respectively). Thus, the primary contribution of this work was to experimentally analyze the effect of the different attachment
configurations on the SPD, and the secondary objective was to determine the effect of the SPD on the η. It was shown that
spatial correlation and spatial pattern of the R
c were different in the surrounding area of each configuration, and ANOVA and DUNCAN tests indicated that η(s) of WSP1, WSP2, and CPP were different at the significant level of P ≤ 0.05 with the mean of 0.94 ± 0.09, 0.63 ± 0.14, and 1.13 ± 0.07, respectively. Additionally, the amount of PM20, PM40, PM60, PM80, and PM100 trapped by the configurations of WSP1, WSP2, and CPP considerably varied depending upon the particular aerodynamic circumstances associated with every configuration. 相似文献
992.
Guoqiang Wang Jingshan Yu S. Shrestha H. Ishidaira K. Takeuchi 《Environmental Earth Sciences》2010,61(4):787-797
A grid-based erosion model is developed by integrating the distributed hydrological model, BTOPMC, with the modified USLE
to estimate soil erosion and sediment outflow during single storms. The possible sheet, rill, channel erosion types, and sediment
transport processes are considered within each grid under the model structure. Instead of representing the sheet erosion and
rill erosion separately, the classic USLE method is modified to simulate the lumped sheet–rill erosion during storms. In the
modification, the runoff ratio and a relevant correction coefficient are brought into the R-factor which improves the model’s applicability in predicting erosion during single storms. Instead of representing a grid
with a unique erosion type, a channel component is assumed to exist in each grid, and its width varies with the upstream contributing
area of the grid. This assumption avoids the problems that are caused by the difference between the channel widths in the
upstream area and the downstream area if the grid is simply recognized as a channel grid. It also enables the model to be
applicable in simulating soil erosion and sediment outflow from a large catchment. Through a case study in the Lushi catchment,
China, the results show an overall satisfactory accuracy for the selected events. Moreover, by analyzing the spatial distribution
of soil erosion or deposition, the erosion-prone areas are identified for the prioritization purpose. 相似文献
993.
In this study subsidence due to groundwater withdrawal was investigated. Kerman Province in Iran is struggling with land subsidence
problem due to extensive groundwater withdrawal mainly for farming. The rate and type of groundwater withdrawal has very important
impact on settlement rate. In this research, effective parameters on land subsidence caused by groundwater withdrawal were
determined by laboratory tests. Sampling had done up to depth of 300 m mainly with remolded specimens from Shams-abad, Nouq
plain in Kerman province. Similar to the field preconsolidation pressure was applied on specimens in the laboratory. Rate
of applied stress on prepared specimens was similar to effect of oscillation of groundwater level. In order to model the actual
soil behavior in the laboratory, one-dimensional consolidation device (odometer) was adopted for testing. In these tests,
the effect of loading caused by seasonal oscillation of groundwater table is considered by means of cyclic loading in the
testing which has great effect on rate of settlements. The results of tests show that when the water table level periodically
increases and decreases the amount of settlement decrease, comparing with the case when the groundwater table drop to a constant
level. In order to predict the further effects of groundwater level oscillation and actual field condition on land subsidence,
a finite element model based on Biots’ three-dimensional consolidation theory was developed. After calibration of finite element
model with laboratory tests, this model was used for prediction the effect of groundwater level oscillation on actual field
conditions. 相似文献
994.
This paper reports the results of petrographic and geochemical studies of the Miocene-Pleistocene volcanic rocks that accompanied
the formation of the deep-water basins of the Sea of Japan and Sea of Okhotsk. The geochemical types of these rocks, their
geodynamic settings, and their derivation from different magmatic sources were determined. The marginal-sea basaltoids of
the Sea of Japan are derivatives of fluid-enriched mantle (EMI), while the volcanics of the Kurile basin were generated from
mantle enriched in continental crust (EMII). In spite of the different conditions of their genesis, they share some common
geochemical features, in particular, their calc-alkaline signatures. These traces of the influence of sialic crust on magma
generation confirm the development of the basins of both these seas on continental basement. 相似文献
995.
Platinum-group minerals (PGM) in primary ores and placers are compared in order to substantiate prospecting guides for layered
and differentiated intrusions containing sulfide Cu-Ni ores with platinum-group elements (PGE). It is shown that supergene
placer mineral assemblages bear information on primary sources and their probable economic value. The mineralogical and geochemical
data on the large Siberian intrusions that host Cu-Ni and low-sulfide PGM deposits (Noril’sk 1, Kingash, Chinei, and Yoko-Dovyren)
are used to elaborate mineralogical prospecting guides based on the comparative study of PGM assemblages in primary ore, heavy
concentrate halos, and hillside sediments. The mechanism of PGM redistribution under supergene conditions is exemplified in
the Chinei deposit. The placer mineral assemblage with prevalence of Pt-Fe alloys, atokite-rustenburgite, sperrylite, and
multicomponent Pd-Sn-Cu-Pb compounds can be used as a prospecting guide for Noril’sk-type primary PGM ore and related economic
placers. The paolovite-sperrylite or sperrylite PGM assemblage in heavy concentrate halos indicates occurrence of Cu-Ni ore
in the prospecting area. Sperrylite with isomorphic admixture of Ir and Os typical of the Kingash pluton could be a orospecting
guide for Ni-bearing mafic-ultramafic intrusions. 相似文献
996.
By the example of the Orlovka massif of Li-F granites in Eastern Transbaikalia, the major- and trace-element (Li, Be, B, Ta,
Nb, W, REE, Y, Zr, and Hf) compositions of the parental melt and the character of its variations during the formation of the
differentiated rock series were quantitatively estimated for the first time on the basis of electron and ion microprobe analysis
and Raman spectroscopy of rehomogenized glasses of melt inclusions in quartz. It was shown that the composition of the Orlovka
melt corresponded to a strongly evolved alumina-saturated granitoid magma (A/CNK = 1.12–1.55) rich in normative albite, poor
in normative quartz, and similar to ongonite melts. This magma was strongly enriched in water (up to 9.9 ± 1.1 wt %) and fluorine
(up to 2.8 wt %). Most importantly, this massif provided the first evidence for high B2O3 contents in melts (up to 2.09 wt %). The highest contents of trace elements were observed in the melt from pegmatoid bodies
in the amazonite granites of the border zone: up to 5077 ppm Li, 6397 ppm Rb, 313 ppm Cs, 62 ppm Ta, 116 ppm Nb, and 62 ppm
W. Compared with the daughter rock, the Orlovka melt was depleted at all stages of formation in SiO2 (by up to 6 wt %), Na2O (by up to 2.5 wt %), and, to a smaller extent, in Ti, Fe, Mg, Sr, and Ba, but was enriched in Mn, Rb, F, B, and H2O. 相似文献
997.
Mechanism and geochemical implications of the Late Holocene organic carbon burial event: an example from the southwest coast of India 总被引:1,自引:0,他引:1
B. Ajaykumar Mahesh Mohan M. S. Shylesh Chandran K. K. Jayasooryan K. S. Unni A. P. Thomas 《Environmental Earth Sciences》2010,59(7):1409-1416
Carbonaceous clay found in the palaeo-deposits of Meenachil River basin was analysed for the total organic carbon, nitrogen
and textural characters. Radiocarbon dating of this clay formation and the embedded carbonized wood fragments was also done.
The values obtained for the organic carbon, nitrogen and C/N ratio of the carbonaceous clay exhibited a very remarkable range,
suggestive of different environmental conditions of formation. It is evident from the present study that since the lignin
and cellulose are the dominant components of terrestrial higher plants, allochthonous and submerged organic matter have high
C/N ratio. The radio carbon dating of the sediment and wood samples suggested that the palaeo-deposits of Meenachil River
basin were formed as result of many transgrassive–regressive episodes, which had started even before the formation of Vembanad
Lake. The formation of carbonaceous clay, as found sandwiched in palaeo-deposits, was due to the global eustatic sea-level
fluctuations and tectonism. 相似文献
998.
B. Scott P. G. Ranjtih S. K. Choi Manoj Khandelwal 《Environmental Earth Sciences》2010,60(5):1007-1019
About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal
mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including
their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered
regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors
and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed
and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher
recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are
the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate. 相似文献
999.
The aim of this paper is to present earthquake loss estimations for a portion of downtown Ottawa, Canada, using the HAZUS-MH
(Hazards United States Multi-Hazard) software tool. The assessment is performed for a scenario earthquake of moment magnitude
6.5, at an epicentral distance of 15 km, occurring during business hours. A level 2 HAZUS-MH analysis was performed where
the building inventory, microzonation studies, and site-specific ground motion hazard maps (2% exceedence probability in 50 years)
were all improved based on local information. All collected data were assembled into a set of standard geodatabases that are
compatible with the HAZUS-MH software using a GIS-specific procedure. The results indicate that the greatest losses are expected
in unreinforced masonry buildings and commercial buildings. Sensitivity studies show that soil classes, the vulnerability
of schools, and the spatial scale of loss estimations are also important factors to take into account. 相似文献
1000.