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311.
内蒙古新地沟金矿床为一典型绿岩型金矿。利用显微镜、扫描电子显微镜观察到自然金602粒。研究表明,金的赋存形式主要有包体金、裂隙金、粒间金和连生金。载金矿物以黄铁矿、石英为主,所占比例达到95%;其次是钾长石、绢云母、菱铁矿、褐铁矿、黝铜矿、方铅矿、闪锌矿等。自然金的粒度主要以显微极微粒金(0.2~5μm)、显微细粒金(10~20μm)、显微中粒金(20~50μm)、显微微粒金(5~10μm)为主,分别占32.23%、26.91%、20.6%、16.11%;手标本及显微镜下也能观察到显微粗粒金(50~100μm)和巨粒金(100~200μm),虽然其含量仅占4.15%,但其面积可达33.97%,对于矿石品位和储量来说十分重要。电子探针和物相分析显示,矿石中金主要以独立矿物存在,包括大量的自然金和少量的银金矿;通过计算表明金的平均成色为803,金矿物的成色和特征反映金矿形成条件为中温和中等深度。 相似文献
312.
A. Chandrasekar 《Journal of Earth System Science》2002,111(4):437-451
A linear model of the response of a stratified atmosphere to isolated heat sources in spherical coordinates is used to study
the maintenance of the mean position of the mid tropospheric ridge and its displacement. It is well known that the performance
of the southwest Indian monsoon is related to the latitudinal position of the April 500 hPa ridge along 75‡E. It was demonstrated
that an anomalous cooling associated with the increased snow cover in Eurasia can result in moderate southward displacement
of the mid-tropospheric ridge. The results of this study indicate that the vertically integrated cooling rate (strength of
heat sink) has more effect on the southward displacement of the ridge when the sink is closer to the ridge. 相似文献
313.
Sherif Kharbish 《Physics and Chemistry of Minerals》2007,34(8):551-558
A Raman spectroscopic study of Fe-rich sphalerite (Zn1 − x
Fe
x
S) has been carried out for six samples with 0.10 ≤ x ≤ 0.24. Both the intensities and frequencies of the TO and LO modes of sphalerite are approximately independent of Fe concentration.
However, the substitution of Zn by Fe results in five additional bands with frequencies between the TO (271 cm−1) and LO (350 cm−1) modes. Three of these bands are attributed to resonance modes (i.e. Y
1, Y
2 and Y
3 modes). The fourth band (B mode) is assigned to a breathing mode of the nearest-neighbor sulfur atoms around the Fe atoms.
The band at 337 cm−1 is attributed to the presence of Fe3+. The excellent correlations between the normalized intensities of these five different modes and x
Fe
show that these modes depend on Fe-content. Another extra mode at 287 cm−1 is assigned to the presence of Cd in sphalerite. 相似文献
314.
锦屏I级水电站坝址区雾化边坡稳定性分析 总被引:5,自引:0,他引:5
详细介绍了锦屏水电站坝址区岸坡的地质结构特征和变形破坏模式,以雾化雨诱发边坡失稳的机理为基础,结合泄洪雾化区的雾化量级、范围,采用定性和定量方法重点分析了位于雾化区范围内边坡的稳定性状况,按岸坡稳定程度将雾化区分为6个区,提出了雾化区边坡可能的失稳模式.结果表明,两大规模变形破裂体所在的D、E区边坡在水库泄洪雾化的条件下稳定性较差且对工程施工的危害大.针对各区雨雾边坡的失稳模式和稳定性状况提出了相应的工程处理措施,为工程设计和施工提供了科学依据. 相似文献
315.
316.
Numerical simulations of dilatational waves in an elastic porous medium containing two immiscible viscous compressible fluids indicate that three types of wave occur, but the modes of dilatory motion corresponding to the three waves remain uncharacterized as functions of relative saturation. In the present paper, we address this problem by deriving normal coordinates for the three dilatational waves based on the general poroelasticity equations of Lo et al. 2005 [13]. The normal coordinates provide a theoretical foundation with which to characterize the motional modes in terms of six connecting coefficients that depend in a well defined way on inertial drag, viscous drag, and elasticity properties. Using numerical calculations of the connecting coefficients in the seismic frequency range for an unconsolidated sand containing water and air as a representative example relevant to hydrologic applications, we confirm that the dilatational wave whose speed is greatest corresponds to the motional mode in which the solid framework and the two pore fluids always move in phase, regardless of water saturation, in agreement with the classic Biot theory of the fast compressional wave in a water-saturated porous medium. For the wave which propagates second fastest, we show, apparently for the first time, that the solid framework moves in phase with water, but out of phase with air [Mode (III)], if the water saturation is below about 0.8, whereas the solid framework moves out of phase with both pore fluids [Mode (IV)] above this water saturation. The transition from Mode (III) to Mode (IV) corresponds to that between the capillarity-dominated region of the water retention curve and the region reflecting air-entry conditions near full water saturation. The second of the two modes corresponds exactly to the slow compressional wave in classic Biot theory, whereas the first mode is possible only in a two-fluid system undergoing capillary pressure fluctuations. For the wave which has the smallest speed, the dilatational mode is dominated by the motions of the two pore fluids, which are always out of phase, a result that is consistent with the proposition that this wave is caused by capillary pressure fluctuations. 相似文献
317.
Current flood protection policies in the Netherlands are based on design water levels. This concept does not allow for a proper evaluation of costs and benefits of flood protection. Hence, research is being carried out on the introduction of a flood risk approach, which looks into both the probability of flooding and the consequences of flooding. This research is being carried out within the framework of a major project called the Floris project (FLOod RISk in the Netherlands). To assess the probability of flooding the Floris project distinguishes different failure modes for dikes and structures within the dike ring. Based on a probabilistic analysis of both loads and resistance the probability of failure is determined for each failure mode. Subsequently the probabilities of failure for different failure modes and dike sections are integrated into an estimate of the probability of flooding of the dike ring as a whole. In addition the Floris project looks into the different consequences of flooding, specifically the economic damages and the number of casualties to be expected in case of flooding of a particular dike ring. The paper describes the approach in the Floris project to assess the flood risk of dike rings in the Netherlands. One of the characteristics of the Floris project is the explicit attention to different types of uncertainties in assessing the probability of flooding. The paper discusses the different starting-points adopted and presents an outline on how the Floris project will deal with uncertainties in the analysis of weak spots in a dike ring as well as in the cost benefit analysis of flood alleviation measures. 相似文献
318.
319.
建筑物或构筑物基础临近边坡置放的情况在实际工程中十分普遍,但目前对于临近边坡基础的地基承载力及破坏模式尚缺乏深入研究。采用不连续布局优化(DLO)极限分析法建立数值模型,分析边坡几何尺寸、土体参数和基础位置对临坡条形基础的极限承载力和边坡破坏模式的影响,并对国内外现行规范推荐的计算方法进行评价。结果表明:极限承载力随边坡高度和边坡倾斜角的增大而减小,当坡高超过临界高度后,极限承载力将不受其影响;极限承载力随土体黏聚力和内摩擦角的增大而提高,滑动面随黏聚力的增大而变浅,随内摩擦角的增大而变深;极限承载力随基础与坡肩相对距离的增大而提高,当基础置放位置超过某临界距离后极限承载力不受边坡影响。在土体强度高、坡角较大时,《建筑地基基础设计规范》规定的临坡基础最小置放距离偏于危险,设计时仍需考虑边坡对承载力的减损作用;在土体强度较低、坡角较小时,规范规定值偏于保守。美国AASHTO规范对边坡地基极限承载力的取值在砂土边坡时较为可靠,但其仅适用于坡面破坏模式的情况;饱和黏土边坡的承载力曲线有悖于理论解,对临界距离的规定同样存在低估。 相似文献
320.