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941.
Wet granular materials are three-dimensionally simulated by the discrete element method with water bridges incorporated between particles. The water bridges are simplified as toroidal shapes, and the matric suction is constantly maintained in the material. A comparison with experimental tests in the literature indicates that the toroidal shape approximation may be one of the best choices with high practicability and decent accuracy. Mechanical behaviours of wet granular materials are studied by triaxial tests. Effects of particle size distributions and void ratios are investigated systematically in this study. The hydraulic limit of the pendular state is also discussed. It gives the capillary cohesion function which is not only determined by the degree of saturation but also positively correlated to relative density and particle size polydispersity and inversely proportional to mean particle size. Furthermore, the capillary strengthening effect is also analysed microscopically in aid of the Stress–Force–Fabric relationship, mainly in fabric anisotropy, coordination number and stress transmission pattern, which revealed the micro-mechanisms of the additional effective stress induced by capillary effect. 相似文献
942.
Agapitus Ahamefule Amadi 《Geotechnical and Geological Engineering》2011,29(3):259-265
Long term competent performance of liner systems is a critical issue in the design and construction of waste repositories
due to adverse interactions associated with leachate generated by wastes. This study was conducted to verify the efficacy
of fly ash stabilization in enhancing compatibility between lateritic soil and municipal waste leachate. Applications investigated
include soil mixtures containing 0, 5, 10, 15, and 20% fly ash compacted at approximately 2% wet of optimum moisture content
with modified proctor energy. Baseline hydraulic conductivity was first established at every level of fly ash content by permeating
soil mixtures with tap water before permeation with leachate in a compaction mould permeameter using the falling head test
method. Results show that the trend in hydraulic conductivity of specimen containing 0% fly ash was characterized by a gradual
but erratic decrease which may suggests partial entry of the leachate cations into the double layer. Conversely, specimens
containing fly ash showed a general trend consisting of an initial drop in k (up to an order of magnitude) that was followed
by slight decrease sustained until k stabilized and later terminated. Above 10% fly ash content, the relatively high values
of k observed was not connected with the reactivity of the soil mixtures with leachate, rather it may be attributed to excessive
fly ash content that altered their textural and hydraulic properties. The result of this study is potentially significant
in the assessment of fly ash as a compatibility enhancing agent which can be admixed in barrier materials that are susceptible
to adverse reactions with the liquid to be contained. 相似文献
943.
944.
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946.
Natural Hazards - This study involved the systematic collation of historical data from local records, government records, etc., as well as disaster data compiled by contemporary researchers.... 相似文献
947.
948.
Drought is one of the major natural disasters causing huge agricultural losses annually. Regional agricultural drought risk
assessment has great significance for reducing regional disaster and agricultural drought losses. Based on the fuzzy characteristics
of agricultural drought risk, variable fuzzy sets model was used for comprehensively assessing agricultural drought risk of
Liaoning Province in China. A multi-layers and multi-indices assessment model was established according to variable fuzzy
sets theory, and agricultural drought risk of all 14 prefecture-level cities was respectively estimated in terms of dangerousness,
vulnerability, exposure and drought-resistibility. By calculating the combination weights of four drought risk factors, agricultural
drought risk grade of each city was obtained. Based on the assessment results, the spatial distribution maps of agricultural
drought risk were drawn. The results shows that eastern cities have lower drought dangerousness than western cities in Liaoning
Province totally. Most cities are located in low drought vulnerability region and high drought exposure region. Because of
frequent and severe drought since 2000, most cities are located in lower drought-resistibility region. Comprehensive agricultural
drought risk presents apparent spatial characteristics, escalating from the east to the west. Drought dangerousness is the
most important factor influencing comprehensive agricultural drought risk. Through the spatial distribution maps of drought
risk, decision makers could find out drought situation and make decisions on drought resistance conveniently. 相似文献
949.
Finite Element (FE) modeling under plane stress condition is used to analyze the fault type variation with depth along and around the San Andreas Fault (SAF) zone. In this simulation elastic rheology was used and was thought justifiable as the variation in depth from 0.5 km to 20 km was considered. Series of calculations were performed with the variation in domain properties. Three types of models were created based on simple geological map of California, namely, 1) single domain model considering whole California as one homogeneous domain, 2) three domains model including the North American plate, Pacific plate, and SAF zone as separate domains, and 3) Four domains model including the three above plus the Garlock Fault zone. Mohr-Coulomb failure criterion and Byerlee's law were used for the calculation of failure state. All the models were driven by displacement boundary condition imposing the fixed North American plate and Pacific plate motion along N34°W vector up to the northern terminus of SAF and N50°E vector motion for the subducting the Gorda and Juan de Fuca plates. Our simulated results revealed that as the depth increased, the fault types were generally normal, and at shallow depth greater strike slip and some thrust faults were formed. It is concluded that SAF may be terminated as normal fault at depth although the surface expression is clearly strike slip. 相似文献
950.
利用CODE GIM数据分析了2008年5月12日汶川地震和2010年4月14日青海玉树地震震前电离层TEC变化。以震前10天TEC中位数为基准,1.5倍标准差为误差限值,并考虑相应时期的太阳和地磁活动水平(Dst指数和Kp指数),对震前电离层异常的分布进行了分析。结果表明,两次地震震前几天内都有TEC异常出现。 相似文献