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951.
Zhou Chenglong Yang Fan Huo Wen Pan Honglin Meng Lu Mamtimin Ali Li Huoqing Yang Xinghua 《Theoretical and Applied Climatology》2020,140(3):1071-1080
Theoretical and Applied Climatology - Air density strongly constrains the characteristics of an airflow and the resulting flow of sand and therefore, it should not be neglected in sand transport... 相似文献
952.
Statistical Relationship Between UVB(280-320nm) and Broadband Solar Radiation(295-2800nm) at a Subtropical Location(Qena,Egypt)
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The present study quantifies the relationship between ultraviolet-B(UVB) and broadband solar radiation(G) at Qena,Egypt.Data from 10-year hourly integrated totals for both UVB and G on a horizontal surface were used to determine the best fit between the two radiation types.On the basis of the correlation of determination(r2),a second-order polynomial was determined to provide the best fit.For the purpose of developing an empirical model to estimate UVB,all of the cases of UVB and G from a nine-year study from 2001 to 2009 were introduced.Monthly and seasonal empirical models,as well as a general expression,were established for UVB as a function of G.The values of r2 ranged from 0.90 to 0.97.By using a new dataset of G,the estimated and the corresponding measured values of UVB were determined to be in good agreement whereby the values of r2 between the two ranged from 0.91 to 0.98.In addition,the significance and performance of the regression forms were evaluated with the aid of several statistical analysis procedures.The values of the index of modeling(d) and coefficient of modeling efficiency(ME) were close to one.Moreover,the values of RMSE,mean bias error(MBE),and mean absolute error(MAE) were lower than the experimental errors.On the basis of this analysis,it has been determined that the suggested regression forms can be used to estimate UVB when it difficult to obtain measurements or when measurements are available only for limited periods at the studied region. 相似文献
953.
利用克拉玛依-瓜达尔友好城市气象站2018年1月1日至2019年12月31日逐日及逐小时气温、气压、降水、相对湿度、水汽压、风向风速观测资料,对瓜达尔港的气象要素特征进行分析。结果表明:1)瓜达尔港属热带沙漠气候,年平均气温为26.9 ℃,最热月为5—7月,最冷月为1月。瓜达尔港气温年较差、日较差分别为12.5 ℃和6.5 ℃,各季节间气温差异较小。其极端高温达42.7 ℃,极端低温为11.9 ℃。2)瓜达尔港年平均气压为1 009.1 hPa,气压最大值出现在12月和1月,最小值出现在7月,季节差异明显。3)瓜达尔港受制于副热带高压,常年干旱少雨,降水年季之间分布不均,差异明显。2018年年降水量为0.3 mm,集中于冬季;2019年年降水量为67.6 mm,主要集中于秋冬两季。相对湿度和水汽压年均值分别是67.3%和24.3 hPa。4)瓜达尔港年平均风速为2.4 m·s-1,白天风速大于夜晚风速。四季中春季风速偏大,夏季、秋季次之,冬季偏小。风向季节性变化明显,盛行风向除东北风外,还包括西南风。出现频率最高的是2级风,其次是1级风和3级风,6级以上大风出现频率为0。 相似文献
954.
Shafiee Ali Kamalian Mohsen Jafari Mohammad Kazem Hamzehloo Hossein 《Natural Hazards》2011,59(1):481-505
An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area
is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake
Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This paper presents the
steps followed by IIEES in ground motion microzonation. IIEES performs both probabilistic and deterministic seismic hazard
analysis. IIEES uses his own fault map for seismotectonic studies and develops modulus and damping curves for the soils in
the study area. The experience of ground motion microzonation shows that in almost all cases, the estimated 475-year peak
ground acceleration (PGA) values are higher than the PGA proposed by the Iranian seismic code. Although ground motion microzonation
in Iran has some shortcomings, IIEES is making new improvement. This includes development in deterministic seismic hazard
analysis, two-dimensional and three-dimensional modelling of basin and topographical effects, using microtremor measurements
to find shear-wave velocity profiles in high-density urban areas and providing maps for spectral acceleration in the study
area. 相似文献
955.
Arif Ali Baig Moghal Puvvadi V. Sivapullaiah 《Geotechnical and Geological Engineering》2011,29(5):665-673
This paper presents the effects of addition of lime and lime along with gypsum on the compressibility behavior of two class
F fly ashes. Since the fly ashes develop strength and exhibit lower compression, consolidation testing with conventional duration
of load increment may not be appropriate. Hence, an attempt has been made to assess the minimum duration of load increment
necessary to study the compressibility characteristics of such materials. Thus compressibility behavior of fly ashes with
additives has been studied using conventional consolidation test with different durations of load increments varying from
30 min to 48 h. The results obtained indicated that 30 min of duration of load increment can be used to assess the compressibility
behavior of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained
with the duration of load increment of 30 min but gradually reduces with higher durations of load increment. It has also been
observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and gradual thereafter. The compressibility
of lime treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction
in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of
embankments and for structural fills, particularly reducing the time required in between laying of each lift. 相似文献
956.
S. M. Ali Zomorodian Mohammad Jamali Moghadam 《Geotechnical and Geological Engineering》2011,29(4):637-644
Cracks in filter can develop as a result of earthquake deformations or post-construction settlement and in some cases cracks
extended through both the core and filter. Hence, a test apparatus has been developed to investigate filter performance in
the case of filter and core material cracking in the embankment dams. The apparatus allows testing of incomplete cylindrical
test specimens of 10 cm diameter and height of 20 cm. If the filters work well and successfully, crack filling occur, also
the flow rate decrease, and the head water pressure increase to the range of early pressure. In the failed filters case, the
flow rate do not decrease and remain high, also a very low head water pressure take place. In this research, variations of
pressure, fines contents of filter soils, compaction time, PI of the base material and amount of eroded materials was evaluated.
Results showed that prime flow rate increased as hydraulic gradient increased, but decreased in a little time and reach to
a stable value. Filter with 15% of non-plastic fine content, had ability to slump to fill the crack, but its coefficient of
permeability decreased significantly, hence, cannot be used as a filter in embankment dams. 相似文献
957.
Jonathan C. Aitchison Xiaoping Xia Alan T. Baxter Jason R. Ali 《Gondwana Research》2011,20(4):691-709
Age-dating of detrital zircons from 22 samples collected along, and adjacent to, the Yarlung-Tsangpo suture zone, southern Tibet provides distinctive age-spectra that characterize important tectonostratigraphic units. Comparisons with data from Nepal, northern India and the Lhasa and Qiangtang terranes of central Tibet constrain possible sources of sediment, and the history of tectonic interactions.Sedimentary rocks in the Cretaceous–Paleogene Xigaze terrane exhibit strong Mesozoic detrital zircon peaks (120 and 170 Ma) together with considerable older inheritance in conglomeratic units. This forearc basin succession developed in association with a continental volcanic arc hinterland in response to Neotethyan subduction under the southern edge of the Eurasia. Conspicuous sediment/source hinterland mismatches suggest that plate convergence along this continental margin was oblique during the Late Cretaceous. The forearc region may have been translated > 500 km dextrally from an original location nearer to Myanmar.Tethyan Himalayan sediments on the other side of the Yarlung-Tsangpo suture zone reveal similar older inheritance and although Cretaceous sediments formed 1000s of km and across at least one plate boundary from those in the Xigaze terrane they too contain an appreciable mid-Early Cretaceous (123 Ma) component. In this case it is attributed to volcanism associated with Gondwana breakup.Sedimentary overlap assemblages reveal interactions between colliding terranes. Paleocene Liuqu conglomerates contain a cryptic record of Late Jurassic and Cretaceous rock units that appear to have foundered during a Paleocene collision event prior the main India–Asia collision. Detrital zircons as young as 37 Ma from the upper Oligocene post-collisional Gangrinboche conglomerates indicate that subduction-related convergent margin magmatism continued through until at least Middle and probably Late Eocene along the southern margin of Eurasia (Lhasa terrane).Although the ages of detrital zircons in some units appear compatible with more than one potential source with care other geological relationships can be used to further constrain some linkages and eliminate others. The results document various ocean closure and collision events and when combined with other geological information this new dataset permits a more refined understanding of the time–space evolution of the Cenozoic India–Asia collision system. 相似文献
958.
A metamorphic core complex model is proposed for Khoshoumi Mountain uranium mineralization located in the Bafq–Saghand metallogenic zone of central Iran. Uranium mineralization occurred in the Chapedoni metamorphic complex. Detailed structural analysis of the complex leads to the interpretation that the mineralization is spatially concentrated in a low angle shear zone of mylonitized migmatite, the lower ductile part of the Chapedoni metamorphic complex. The shear zone that has top to the NE sense of shear in the northeastern and southeastern parts of the mountain and top to the WNW sense of shear in the southwestern part is a detachment zone to the Chapedoni Metamorphic Core Complex (CMCC). The Eocene granite is the plutonic core to the CMCC. The shear zone is cut by several NE‐trending left‐lateral strike‐slip faults. This later faulting is interpreted to account for the significant enrichment of uranium in the southern part of the mountain. The bimodal distribution of radiometric data gathered from exploratory drill holes in this part of the mountain constrains this interpretation. That is, the lower value is from the shear zone across the area but the higher value is from the places that the shear zone is cut by the transverse faults. 相似文献
959.
4He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4?C6 times on each sample, and indicate a bulk 4He diffusion coefficient of 3.5?±?1.3?×?10?C8 cm2?s?C1 at 21°C, compared to previously published diffusion coefficients of 1.2?×?10?C18 cm2?s?C1 (21°C) to 3.0?×?10?C15 cm2?s?C1 (150°C) in the sands and clays. Correcting the diffusion coefficient of 4Hewater for matrix porosity (??3%) and tortuosity (??6?C13) produces effective diffusion coefficients of 1?×?10?C8 cm2?s?C1 (21°C) and 1?×?10?C7 (120°C), effectively isolating pore fluid 4He from the 4He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8?±?0.4% (SD, n?=?4) and mudstones 3.1?±?0.8% (SD, n?=?4). 相似文献
960.
Based on the spherical cavity expansion (SCE) problem, Cudmani and Osinov (Can Geotech J 38:622–638, 2001), Osinov and Cudmani
(Int J Numer Anal Method Geomech 25:473–495, 2001) developed a semi-empirical method of interpretation of CPT for coarse-grained
soils (sand, gravel) using a hypoplastic constitutive model. Using a material-independent shape factor, the cone penetration
resistance was related to the limit pressure required to expand a spherical cavity. The shape factor was observed to be a
function of the soil state only, in particular the pressure-dependent relative density. This paper presents an analogous interpretation
technique for CPT in fine-grained soils using the shape factor concept, Cavity Expansion approach, and a hypoplastic constitutive
model. Relations for the shape factor and the limit pressure have been proposed based on the parameters affecting these quantities.
A validation of the proposed interpretation technique with experimental results has also been performed. 相似文献