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451.
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水库所在地属水土流失严重区,河流产水量少,产沙量大,拦河建库蓄水,泥沙问题成为工程设计及运行须认真对待的问题。本文分析了红石峁河的来沙特性,采取了相应地、较为合理地排沙减淤方式与方法,提出了适于工程实际的排沙方案;也为水库管理运行提供了依据。 相似文献
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《Geomechanics and Geoengineering》2013,8(2):109-115
Experience has shown that to obtain pre-failure deformability of geomaterials in laboratory element tests, it is imperative to make local strain measurements. For torsional shear tests, the local measurement is complicated by coupling of the axial, radial, and rotational movement experienced by the soil specimen during shear. The rotational displacement must be isolated from other modes of movement for the interpretation of test results. Existing techniques designed for torsional shear tests under general stress conditions can be complicated and difficult to use. A simplified scheme using two pairs of linear variable displacement transducers (LVDTs) is proposed for local rotational deformation measurement, specifically for cyclic torsional shear tests under constant normal stress conditions. The subtraction of readings within an LVDT pair nullifies displacements at the measurement point caused by axial and radial movement or bulging of the specimen. The same subtraction accumulates and thus isolates LVDT readings caused by rotational movement. The error associated with the simplified set-up is expected to be <0.125%. A series of hollow cylinder torsional shear tests have been performed to verify the effectiveness of the new measurement scheme. The results are repeatable and consistent with well-documented test data. 相似文献
456.
This study presents promising variants of genetic programming (GP),namely linear genetic programming (LGP) and multi expression programming (MEP) to evaluate the liquefaction resistance of sandy soils.... 相似文献
457.
淮安地震台沙层应力仪器观测数据变化的特征分析 总被引:1,自引:0,他引:1
用小波变换和傅里叶变换的分析方法对2009年5月至2012年6月淮安沙层应力数据进行频谱分析.发现:淮安台沙层仪器所记录数据中含有多个频率成份,其中低频信号频率以1.157 4×10-5 Hz附近信号最强,在2.314 8×10-5 Hz附近次之,高频信号频率在0.25~0.45 Hz之间.低频信号反映在日、月等引潮力的作用下固体地球产生的周期性潮汐变化的地壳形变特征;高频信号更多的反映地壳应力变化特征.淮安沙层应力观测数值变化不仅与其他沙层应力台站有相同变化形态和一致的年变规律,还与地震活动有较好的对应关系.沙层应力数据变化能反映大地震从孕育到发生的完整过程,一般具有上升、平稳、下降、回升发震等几个阶段. 相似文献
458.
M. S. Öncel 《Environmental Geology》2008,53(8):1767-1775
Dry lakes, degraded sandy grasslands, abandoned farmland and mobile dunes which are widely distributed throughout the arid
areas of northern China have been investigated in this work. Gain-size distribution of the surface sediments of Manas lake
in Junggar basin, Juyan lake in the Alxa plateau, Zhuye lake in Minqin basin and most deserts (such as Mu Us desert, Otindag
desert, Horqin desert and Hulun Buir desert) in China have been analyzed. The results show clay with particle sized <10 μm
on the surface sediments of dry lakebed and sandy grassland developed from dry lakebed, respectively, account for >60% and
∼50% of the total mass. Since the tiny particles on the surface of abandoned farmland are blown away easily and rapidly, the
content of clay particles in Minqin basin is <14%. The grain-size distribution of mobile dunes in northern China mainly consists
of particles >63 μm and few particles <10 μm. Consequently, although sand/dust storms originate primarily in the western deserts,
the gobi areas of the Alxa plateau, the north and east of Hexi Corridor and in central Mongolia, the widely distributed dry
lakebeds, sandy grasslands and abandoned farmland adjacent to the deserts also contribute to aeolian dusts. Hence, the material
sources for sand dust storm in East Asia include inland deserts, but also dry lakes, sandy grasslands and abandoned farmland,
which are widely distributed throughout the arid inlands of northern China. 相似文献
459.
M. Rama Rao A. Sreerama Rao R. Dayakara Babu 《Geotechnical and Geological Engineering》2008,26(2):189-197
Expansive clays swell and shrink seasonally when subjected to changes in the moisture regime causing substantial distress
to the structures built in them. Techniques like sand cushion and cohesive non-swelling soil (CNS) layer have been tried to
arrest heave and consequent damages to structures. Sand cushion has been proved to be counter-productive. Studies have indicated
that even though CNS layer was effective initially, it became less effective after the first cycle of swelling and shrinkage.
Research carried out by the authors, using cement-stabilized fly ash as a cushioning material, has shown that it was quite
effective in arresting heave. Fly ash cushion, stabilized with 10% cement with thickness equal to that of the expansive soil
bed reduces heave by about 75% in the first instance. With subsequent swell-shrink cycles, the performance further improves,
unlike in the case of a black cotton soil provided with a CNS cushion. At the end of fourth cycle of swelling, the reduction
in the amount of heave is as high as 99.1%. 相似文献
460.