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91.
极低屈服点软钢阻尼器恢复力模型的研究 总被引:3,自引:0,他引:3
本文通过试验和理论分析探讨极低屈服点软钢阻尼器的恢复力特性。随着塑性变形的发展将恢复力模型中的骨架曲线进行平移,其卸载曲线用Ramberg—Osgood函数来描述,由此得到的恢复力模型定义为骨架平移模型,将其应用于描述极低屈服点软钢阻尼器的恢复力特性、为了验证该馍型的有效性并确定合理的参数,对安装极低屈服点软钢阻尼器的3层钢框架结构进行了拟动力试验.同时用该骨架平移模型模拟极低屈服点软钢阻尼器的恢复力特性进行了大量的弹塑性地震反应分析,通过取用不同平移系数时的数值计算结果与拟动力试验结果的比较,发现平移系数为0.6左右时,该模型具有较高的精度。 相似文献
92.
Coral Sr/Ca and Mg/Ca records in Con Dao Island off the Mekong Delta: Assessment of their potential for monitoring ENSO and East Asian monsoon 总被引:2,自引:0,他引:2
Takehiro Mitsuguchi Phong X. Dang Hiroyuki Kitagawa Tetsuo Uchida Yasuyuki Shibata 《Global and Planetary Change》2008,63(4):341-352
The climate of the South China Sea (SCS) is dominated by the East Asian monsoon (EAM) and can be related to the El Niño-Southern Oscillation (ENSO) owing to the interaction between ENSO and the EAM. An annually-banded coral (Porites sp.) collected from Con Dao Island in the southern SCS was measured for Sr/Ca and Mg/Ca ratios at near-monthly resolution through the annual bands of AD 1948–1999. This island is only ~ 90 km from the Mekong Delta coast and thus significantly influenced by riverine discharge, suggesting relatively severe environmental stress on corals. The Sr/Ca time series shows a clear annual cyclicity chiefly modulated by sea-surface temperature (SST), whereas the Mg/Ca time series exhibits an indistinct annual cyclicity, indicating that the previously-proposed coral Mg/Ca thermometry is greatly disturbed. An instrumental SST record in Con Dao Island (since 1980) has been compared with the Sr/Ca time series to calibrate a Sr/Ca thermometer. The Sr/Ca vs. SST comparison shows that the Sr/Ca thermometer is sometimes disturbed by some factor and that almost all of the disturbances occur around the annual-maximum SST in the warm/wet season. The Sr/Ca data around the annual-minimum SST in the cool/dry season is almost free from the disturbance and thus useful as a SST proxy. The disturbances of the Sr/Ca and Mg/Ca thermometers may be ascribed to the Mekong River discharge and its accompanying phenomena (i.e., large freshwater input, suspended-sediment loads, intense phytoplankton blooms, etc.), which are likely to disturb coral physiological processes. Applying the Sr/Ca thermometer to the whole Sr/Ca time series provides a SST reconstruction from 1948 through 1999. Reconstructed annual-minimum SSTs show a clear quasi-biennial oscillation significantly correlated with ENSO, indicating that the annual-minimum SST in the southern SCS tends to be higher (lower) in El Niño (La Niña) phases. This is compatible with previous observations that the East Asian winter monsoon is weakened (strengthened) in El Niño (La Niña) phases. The reconstructed SST record suggests a warming of 1.0 °C for the latter half of the 20th century. The Sr/Ca and Mg/Ca time series exhibit similar decadal-to-bidecadal variations, which do not seem to be primarily due to SST variability but rather due to some other factor possibly related to disturbance or fluctuation of coral physiological processes. Although both of our Sr/Ca and Mg/Ca data are affected, to a greater or lesser extent, by some non-temperature factor, a part of the Sr/Ca data provides a useful SST proxy and suggests that coral-based SST reconstruction in the southern SCS may be an effective means for monitoring the EAM and ENSO. 相似文献
93.
Mahnoosh Biglari Claudio Mancuso Anna d’Onofrio Mohammad Kazem Jafari Ali Shafiee 《Computers and Geotechnics》2011
Existing models for predicting the small strain behaviour of unsaturated soil are not capable of predicting the initial shear stiffness during suction reduction under normally consolidated conditions. This problem has been addressed in the present study by combining an existing elastoplastic model and recent experimental data to provide a new model for the initial shear stiffness. The model, which is similar to that typically adopted for saturated soils, uses the average skeleton stress and an additional function of the degree of saturation. This new model not only captures the behaviour of the new experimental results, but it also describes a unique relationship between saturated and unsaturated soils. 相似文献
94.
利用空白区域骨架线网眼匹配多源面状居民地 总被引:1,自引:1,他引:0
多源大比例尺城市地图中,同名居民地数据间往往存在较大几何位置偏差,从而增加了居民地匹配的难度和不确定性。针对这一问题,本文提出了一种利用空白区域骨架线网眼进行居民地匹配的新方法。首先,提取空白区域骨架线,并建立空白区域骨架线网眼和居民地之间的一一映射关系,将居民地匹配转换为骨架线网眼匹配;然后,根据骨架线网眼之间的相接拓扑关系构建对偶图,计算对偶图中每个节点的各项中心性指标,并利用极化变换和层次分析法建立骨架线网眼匹配模型,获取骨架线网眼匹配结果;最后,将骨架线网眼匹配结果按照映射关系进行传递,从而得到居民地匹配结果。将居民地匹配转换为空白区域骨架线网眼匹配,并对骨架线网眼进行对偶图构建和极化变换,为匹配增加拓扑约束和相对位置约束,从而弥补几何位置的较大偏差对匹配造成的影响。对比试验及分析表明本方法能够有效解决大比例尺城市地图中几何位置偏差较大的面状居民地的匹配问题。 相似文献
95.
为在DEM简化过程中充分保留地形骨架信息,提出一种基于ANUDEM与山脊抬升的DEM简化方法。利用ANUDEM插值法获得顾及水文要素的DEM简化表面,并对简化DEM实施山脊抬升,从而得到顾及地形骨架的简化表面。实验表明,在简化DEM中实施山脊抬升能够更大程度地增强简化表面山体结构的保留程度,且随着地形简化程度的降低,山脊抬升法的作用也逐渐增大。 相似文献
96.
97.
石珊瑚骨骼对重建古海洋古气候环境,评估珊瑚礁对未来气候变化、海洋酸化的响应和反馈,辨识现存造礁石珊瑚种属及其演化途径有着十分重要的作用和意义。为了更好地认知造礁石珊瑚骨骼特征,在三亚海域采集了常见的造礁石珊瑚——鹿角杯形珊瑚Pocillopora damicornis,通过扫描电镜(结合EDS能谱仪)、红外分光显微镜分析其碳酸钙骨骼结构和成分的特征,结果表明鹿角杯形珊瑚骨骼主要成分为文石,少数骨骼样品的空腔中发育有极少量方解石矿物。虽然鹿角杯形珊瑚骨骼宏观架构和中观架构在群体间和单体间存在诸多差异,但不同形态的骨骼样品具有基本相同的发育模式和基础结构单元。同时,发现鹿角杯形珊瑚骨骼内部空腔存在有次生文石沉积发育现象,同时常伴生着水镁石矿物的发育,而且这与骨骼中的钻孔穴居动物有很大关联。 相似文献
98.
Astronomical instruments currently provide a large amount of data. Nowadays, a large part of these data are image frames obtained with receivers of increasing size. The scan of large astronomical plates using fast microdensitometers gives image frames of over 30000×30000 pixels. More and more often, images are transmitted over a network in order to control the observations, to process the data, and to examine or to fill a data bank. The time taken for archiving, the cost of communication, the available memory given by magnetic tapes, and the limited bandwidth of transmission lines are reasons which lead us to examine the data compression of astronomical images.The astronomical image has the characteristic of being a set of astronomical sources in the sky background whose values are not zero. We are, in fact, only interested in the astronomical sources. Once a suitable detection is made, we generally want a compression without any distorsion. In this paper, we present a method which can be adapted for this purpose. It is based on morphological skeleton transformations. The experimental results show that it can give us an efficient compression. Moreover, the flexibility of choosing a structure element adapted to different images and the simplicity of implementation are other advantages of this method. Because of these characteristics, different compression applications may be treated. 相似文献
99.
倾斜地层地震液化和滑移的有限元分析 总被引:1,自引:0,他引:1
应用饱和多孔介质动力学分析倾斜地层的土壤动力线性反应、液化和液化滑移问题,地下水位上的地层简化为单相介质层,饱和夹砂层看作是两相介质,水是可压缩的,采用双曲线非线性本构关系,考虑了砂土的剪胀性、刚度退化、滞回特性和土水相对运动等因素。基于土力学模型,建立了适用于分析非自由场地液化的动力方程组,基于是否考虑发生渗流问题,同时建立了两种离散形式:一种是以土骨架位移和水位移为未知量的矩阵方程,另一种是以土骨架位移、水位移和孔隙水压力为未知量的矩阵方程,初步分析了适用于多孔介质波动模拟的离散模型的人工边界问题,形成的方法将有助于问题的解决。 相似文献
100.
HUANGPeizhi Poh-ChinLai 《地球空间信息科学学报》2002,5(2):68-73
The geometric and physical analysis methods are conventional methods for the derivation of skeleton lines in the fields of cartography,digital photogrammetry,and related areas.this paper proposes a stepwise approach that uses the physical analysis method in the first stage and the geometric analysis method in the subsequent stage.The physical analysis method analyses the terrain globally to obtain a rough set of skeleton lines for a terrain surface.The rough skeleton lines help to structure the ordering of feature points by the geometric analysis method. 相似文献