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排序方式: 共有190条查询结果,搜索用时 31 毫秒
101.
Yasaman Memarzadeh Kiani Seyed Hossein Hosseini Lavassani Afshin Meshkat-Dini 《地震工程与工程振动(英文版)》2021,20(3):659-670
This paper provides a general perspective of the seismic performance of a nature-inspired, honey-comb grid structural system, known as a hexagrid, under near-field ground motions. Seismic performance of this skeleton is then compared to that of a bundled-tube, as a conventional and efficient load-resisting system in order to provide a better perception of the seismic behavior of a hexagrid skeleton. Two 20-story buildings with bundled-tube and hexagrid skeleton were studied. Nonlinear behavior of the structures was investigated through 3-D finite element computer models and nonlinear time history analyses by subjecting the models to seven three-component records of scaled near-field ground motions. Distribution of peak inter story drift and corner beam-column joint rotations were calculated and compared. Results indicated that by replacing the exterior columns of the bundled-tube system with inclined beam-column elements of nature-inspired hexagons, lateral stiffness of the building increased and it would tolerate less deformations before global dynamic instability is reached. The presence of inclined columns in the hexagrid skeleton helped to concentrate local nonlinearities in ring beams rather than exterior columns. 相似文献
102.
Ali Akbar Shahsavari Kamal Khodaei Farhad Asadian Farhad Ahmadi Seyed Mohammad Zamanzadeh 《Environmental Earth Sciences》2012,65(1):231-239
Study area with an area of about 415 km2 is located from 31°40′ to 32°05′ northern latitudes and 48°45′ to 49°00′ eastern longitudes 85 km to the north-east of Ahwaz
city, in the north of Khuzestan province, and south west of Iran. The purpose of this study is: (1) the determination of the
pesticides concentration in the groundwater of the Shushtar plain (Mian-Ab) and (2) the assessment of geology, hydrogeology
and anthropogenic activities impacts the groundwater quality. Thirty-seven groundwater samples were taken from product wells
based on the standard methods. A simple and efficient automated method for extraction and preconcentration was used. In this
method, a pyrrole-based polymer was synthesized and applied as an efficient sorbent for micro-solid-phase extraction. After
extraction, analytes were desorbed in ethyl acetate and analyzed using gas chromatography–flame. The study area is surrounded
by Aghajari Formation dominated by silt and clay sediments and the Bakhtiari Formation dominated by sand and gravel. Existence
of these formations affects the aquifer sediments and the hydrogeological properties. In the study area, the sediments grade
from gravel and sand in the north and east into silt and clay to the south and west, respectively. The topsoil in the south
of the study area contains more clay sediments. In this study, the concentration of two common herbicides, i.e., 2,4-D and
clodinafop propargyl and two pesticides, i.e., permethrin and diazinon, in the groundwater of Mian-Ab aquifer was assessed.
Chemical analysis results showed that the 2,4-D residue in the groundwater has the highest concentration (15 ppm). About 50%
of the samples have concentration values more than the maximum contamination level based on EPA drinking standard. The pesticides
concentrations decrease from the north to the south of the study area. Pesticides influx to the groundwater in the south of
the area is prevented or diminished due to the specific geological situation and soil type. Distribution pattern of population
centers, which increase to the north of the study area, and the role of groundwater as the main source of drinking water are
two important issues that must be considered in management of pesticides use in the area. 相似文献
103.
Ocean Dynamics - Third-generation models employ a host of parameterization schemes to consider the input wind forcing and the wave energy dissipation under different physical settings and... 相似文献
104.
AbstractKnowledge of the relationship between rainfall intensity and kinetic energy and its variations in time and space is important for the prediction of erosion hazard. Kinetic energy and erosivity are also strongly controlled by raindrop size. However, studies on raindrop measurement and different practical techniques have been rarely documented. The current study therefore aimed to apply existing raindrop-size measurement techniques—the photographic, flour-pellet and stain methods, as well as an innovative flour-stain method—and to evaluate their applicability at several intensities in Mazandaran Province, Iran. The distribution of raindrop size obtained by the different methods was recorded and compared with those obtained through applying a high-speed imaging technique. All the analyses were made with the help of a SPSS software package. The results showed that the raindrop diameters ranged from 0.2 to 5.16 mm at different rainfall intensities. Statistical comparison of the methods using the Duncan test showed that the flour-pellet method presented similar results to the photographic technique; it was concluded that this can be used as a practical and inexpensive method to estimate a wide range of raindrop sizes.Editor Z.W. KundzewiczCitation Sadeghi, S.H., Abdollahi, Z., and Khaledi Darvishan, A., 2013. Experimental comparison of some techniques for estimating natural raindrop size distribution on the south coast of the Caspian Sea, Iran. Hydrological Sciences Journal, 58 (6), 1374–1382. 相似文献
105.
Seyed Ali Jozi Maryam Sohrabi Balsini Arman Jamshidi 《Journal of the Indian Society of Remote Sensing》2013,41(3):577-585
Protected areas are established to conserve unique features and biodiversity of the nature. Accordingly, wherever has one of the natural, ecological and/or cultural values it should be considered a protected area. Kave-Deh No-hunting Area is located on extremely east of Tehran Province in an area of 94,961 ha. Due to rich and diverse land cover, distinctive wildlife species, and unique monuments the area was selected as a case study to examine the possibility of its promotion to the protected area using Spatial Multi Criteria Evaluation (SMCE) Method. For this purpose, the relevant criteria were identified by Delphi method. After finalization of the most important criteria by Delphi panelists, the map layers were prepared at the scale of 1:100000, in the environment of GIS Software. Afterwards, the map layers were divided into factors and constraints of which factors were standardized by S-shaped membership functions of fuzzy logic. The dimensionless factor maps were weighted using Analytical Hierarchy Process (AHP) Method in the environment of Expert Choice Software. Subsequently, a mathematical equation was extracted to conduct the land suitability analysis. The Weighted Linear Combination (WLC) Method was applied to overlay the map layers and obtain the final ‘nature conservation’ land use map. The final land suitability map showed that 34,687 ha of whole study area (equal to 37 %) have the potentiality for promotion to the protected area. 相似文献
106.
The aim of present study was to improve compost quality as well as to achieve an optimum C/N ratio in compost, reduction in heavy metal content and increased water‐holding capacity of composting piles in arid areas. Four windrow compost piles were prepared by mixing sawdust at various dosages with municipal solid waste (MSW). The sawdust was mixed with MSW at 0% (MSW0), 16% (MSW16), 32% (MSW32), and 70% (MSW70) on dry weight basis. The compost piles were monitored daily by recording the temperature, while, weekly measurement was done on C/N ratio, moisture, pH, and electrical conductivity (EC). The addition of 16% sawdust increased the initial C/N to the optimum level and decreased N loss during the composting process. The MSW16 and MSW32 exhibited better temperature dynamics and their composting period seemed to be shorter than that of MSW0 and MSW70. Moreover, addition of sawdust caused lowering of moisture loss from the composting piles. Sawdust admixtures also produced lowering of pH and EC values and led to lower heavy metal content in final products. The quality of the final compost makes it possible to propose the use of this experimental procedure for building up a novel mass reduction of the initial composted waste mixtures. 相似文献
107.
108.
对完整岩石力学机制的研究有助于更好地理解与屈服有关的应力-应变关系。屈服准则研究方法包括基于实验数据分析和基于微观力学的研究。屈服数学理论的研究目标是对应力和应变关系的理论描述和对弹塑性界限的识别。本文主要研究完整岩石在不同尺度上的屈服。从Weibull理论可知,岩石强度随尺度增大而减少,这已经通过单轴压缩强度(UCS)的Hoek-Brown方程得到证实。然而,围压能改变岩石强度及屈服。因此,本文利用直径为50mm和96mm的圆柱形砂岩样品在不同围压作用下的压缩实验来研究不同尺度下的岩石屈服,从实验中提取不同尺度下的屈服初始点并描述屈服面,最终给出简单数学形式的屈服准则。 相似文献
109.
Effects of non-rigid muddy bed on the wave climate at the Hendijan coast along the northwestern part of the Persian Gulf have been examined through field measurements and numerical wave transformation modeling. The field survey included measurements of wave characteristics at an offshore and a nearshore station, and mud sampling to obtain the thickness of the fluid mud layer and its rheological properties. Comparisons of wave spectra at the two stations show energy dissipation along the wave trajectory with higher dissipation in the wave period band around 6?s, because depending on the site a given frequency band tends to be more effective in wave–mud interaction. Dissipation induced by the non-rigid bed is introduced into the REF/DIF wave transformation model through the application of viscoelastic constitutive equations for fluid mud. Numerical outputs of the nearshore wave height, for which the viscoelastic parameters included in the model were obtained independently from oscillatory frequency-sweep tests, are found to be comparable with measured values at the nearshore station. This implies that the model is useful for estimating the design wave conditions in the study area. 相似文献
110.
Negin Kananizadeh Taghi Ebadi Seyed Alireza Khoshniat Seyed Ehsan Mousavirizi 《洁净——土壤、空气、水》2011,39(7):605-611
This study evaluates the effect of nanoclay on permeability, swelling, compressive strength, and cation exchange capacity of a compacted Kahrizak landfill clay liner. The results show that 4% nanoclay significantly reduces permeability (3 × 10?9 to 7.74 × 10?11 cm/s in neutral, 3.66 × 10?9 to 7.9 × 10?10 cm/s in acidic, and 3.25 × 10?9 to 5.24 × 10?10 cm/s in alkaline condition), and increases compressive strength (by 36.28%) and the percentage of swelling (from 16.67 to 41.82, 23.33 to 45.45, and 15 to 38.18 at pH 7, 4.8, and 9, respectively) compare to raw clay samples. Moreover, the results of cation exchange capacity tests show that adding 4% nanoclay to the Kahrizak clay, permeated with landfill leachate, helps the sample maintain its mono‐valent ions between layers and remains dispersed. The results of SEM and XRD analyses show that by adding nanoclay, nanoclay clusters are formed in the sample; as a result, the interlayer spacing decreases which makes it remain dispersed. XRF analyses also demonstrate that by adding nanoclay to the mixture, the permeability and therefore, the amount of heavy metals which can penetrate into it decreases. The results justify the construction of clay barriers with nanoclay in order to prevent leachate penetration, and consequently reduce the operation costs. 相似文献