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991.
A three-dimensional dam-reservoir system under seismic load is analysed. The dam is assumed to be rigid. The reservoir is an infinite channel with semi-circular cross-section. The exact analytical solution, based on the assumption of potential fluid motion is presented, as well as numerical results for selected parameters.The most significant parameters are: the direction and frequency content of the seismic input; the radiation damping at the reservoir bottom; and the compressibility of the fluid. The response of the system depends strongly on the direction of the input ground motion. This is shown by the transfer functions as well as by the pressure time histories due to two earthquakes with different frequency content. The energy absorption at the reservoir bottom is important. A simple plane-wave model shows, that even for a rock foundation, the amount of transmitted energy can reach up to 80%. For comparison the case without bottom absorption is also shown. Compressbility has to be included to capture the resonance effects. The exact analytical solution is also used to verify numerical results obtained by a new method that combines a finite element model with a rigorous radiation boundary for the infinite channel in the time domain. 相似文献
992.
用周期图分析法,总结北天山地震带自1889年以来强震活动的规律,推测下一次强震活动的时间。通过5次后验表明,所用的数学模型能较好地反映研究区域历史地震活动的规律。 相似文献
993.
Hydrogen sulfide dissolved in surface seawater is distributed into free forms which include the volatile neutral H2S and its conjugate anions, and also into a set of involatile metal complexes. Calculation of the sulfide fraction capable of supporting sea-air flux is sensitive to large uncertainties in complexation equilibrium relationships, both for the sulfides themselves, and for organic ligands competing with them to coordinate dissolved copper. Saturation can be achieved relative to the troposphere if metal interactions are minimized, or if strong sulfide binders are titrated. 相似文献
994.
Data collected by Magsat have been extensively used by Indian scientists in studies of the crust beneath India. Results obtained
by various workers have been summarized and the reasons for differences in findings have been discussed. It is concluded that
methods that work well for higher latitudes do not give the best estimates of crustal field and magnetization in equatorial
regions. A better estimate of the crustal component is obtained when the external current contribution is estimated using
the symmetry properties of associatedX and Z-fields. Inversion technique that provides stable crustal magnetization in midlatitudes, becomes unstable near the equator.
Why such an instability arises and how it can be circumvented are discussed. That the Peninsular shield, the Ganga basin and
the Himalayas are three different geotectonic blocks is clearly reflected in the magnetization distribution. A thick magnetic
crust under Aravalli, Singhbum and Dharwar suggest these areas to be comparatively stable. In general, seismic, gravity and
heat flow data agree characteristically well with the magnetization estimates. 相似文献
995.
本文应用同位素地质方法研究322矿田内花岗岩的年龄和成因、成矿热液和成矿物质来源等问题。研究表明,矿田内的成矿母岩为改造型花岗岩,其Rb-Sr同位素年龄为198.8Ma,成矿热液来自花岗岩结晶矿物颗粒间和裂隙中的溶液以及大气降水。成矿物质主要来自花岗岩,部分也来自岩体周围的寒武系地层。 相似文献
996.
矽卡岩矿床共生单科辉石—石榴石氧逸度计及主要金属矿化类型矽岩生成的氧逸度条件 总被引:1,自引:0,他引:1
基于我国主要类型矽卡岩矿床的研究,结合Ca-Fe-Si-C-O体系的实验成果,以共
生矿物固溶体热力学分析为手段,建立了共生单斜辉石一石榴石氧逸度计。对我国主要类型矽卡
岩的研究表明:不同金属矿化及不同产出条件的矽卡岩形成于不同的氧逸度环境,具有不同的氧
逸度变化趋势和温度一氧逸度效应。共生单斜辉石一石榴石矿物对是形成介质的良好氧逸度计、酸度计。它有助于判别矽卡岩的金属矿化类型。 相似文献
997.
998.
蒙脱石层间域的性质及其环境意义 总被引:28,自引:0,他引:28
蒙脱石矿物是土壤中比表面积大、分布很广的一种粘土矿物,也是土壤中主要的活性组分之一。蒙脱石层间域是一个特殊的化学反应场所。系统地评述了无机、有机阳离子、农药分子在蒙脱石层间域中的吸附、脱附、氧化还原、催化降解等反应机理,并指出它们的环境化学行为对环境的影响和意义。 相似文献
999.
The massive Zn-(Pb) sulfide ore body at Rampura-Agucha in Bhilwara district, Rajasthan, occurs within graphitic metapelites
surrounded by garnet-biotite-sillimanite gneiss containing concordant bodies of amphibolite. These rocks and the sulfide ores
have been studied to estimate the pressure, temperature and fluid composition associated with upper amphibolite facies metamorphism.
Geothermobarometric calculations involving garnet-biotite and garnet-hornblende pairs, as well as sphalerite-hexagonal pyrrhotite-pyrite
and garnet-plagioclase-sillimanite-quartz assemblages indicate that the most pervasive P-T condition during peak of regional
metamorphism was 650°C and 6 kb, and was attained between the first and second deformations in the region. Some temperature-pressure
estimates also cluster around 500°C–5.1 kb which probably represent retrograde cooling during unloading.
Consideration of devolatilization equilibria in the C-O-H-S system at the pervasive metamorphic conditions mentioned above
shows that the metamorphic fluid was H2O-rich (
) but also had a substantial component of
.
and
were the other important phases in the fluid. CO (XCO = 0.002) and
were the minor phases in the fluid. It is probable that a part of this aqueous fluid was consumed by re-/neocrystallization
of hydrous silicate phases like chlorite during the retrogressive metamorphic path, so that fluid entrapped in quartz below
450°C was rendered CO2-rich (Holleret al 1996). 相似文献
1000.