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排序方式: 共有288条查询结果,搜索用时 31 毫秒
91.
新疆地震活动分期及活动特征的分析 总被引:1,自引:0,他引:1
本文应用公元1600年以来新疆及边邻地区6级以上强震资料,详细讨论了1882年后本区经历的地震活跃强震活动情况。指出了期中地震能量积累、大释放、剩余释放三阶段各自不同的特点;给出了划分活动期的统计模式;讨论了强震轮回的持续时间、关系、强度及存在的韵律现象;估算了本地震活跃期的大致约束时间;并对未来强震活动的发展趋势作了初步的分析。这些结果可为研究新疆地震活动性及地震形势的估计与预测问题提供线索。 相似文献
92.
讨论了地震屏护区的分类和机理,并以研究程度较高的华南地区为例,详细论述了有关问题。指出在特定的条件下,利用相邻地区(带)的地震活动规律,可预报被屏护区的地震活动趋势。而正确划分地震被屏护区,对重大工程建设和大、中城市的发展规划始终具有现实意义。 相似文献
93.
本文利用1900年以来Ms≥4.7地震目录,系统分析了南黄海及沿岸地区与晋冀内蒙交界地区中强地震此起彼伏,遥相呼应的同步涨落现象,利用这一现象,可能对这2地区未来二三年内地震活动趋势预测提供一个方面的证据,本文给出了预测方案,报道了应用实例,并就有关问题进行了讨论。 相似文献
94.
95.
青海强震等间距特征研究及未来强震趋势预测 总被引:5,自引:0,他引:5
利用塑性力学和地震力学以及前人的研究结果,提出了一种新的地震等间距特征机理的解释方法,认为地夺等间距特征的成因是中、下地壳的滑移网同上部地壳的相互作用。其动力源为环太平洋地震带和欧亚地震带的联合作用。利用青海强震分布的等间跨特征对未来可能发生强震的地点进行趋势预测。 相似文献
96.
张家口地震台gPhone连续重力观测仪潮汐因子自2016年6月出现持续下降的趋势变化,累计变化量达到7×10-3。分析重力残差曲线,异常出现时同期残差数据未出现同步变化;将去零漂前后潮汐因子的变化情况进行对比分析,发现潮汐因子变化趋势一致,排除仪器调零影响;针对新建楼房可能引起的重力变化,建立了重力正演模型,计算结果显示,新建楼房的荷载变化仅能引起0.31微伽的重力变化,表明新建楼房对重力观测的影响较弱。综合分析认为,此次出现的重力潮汐因子下降趋势异常可能为前兆异常,需加强跟踪分析。 相似文献
97.
Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises. 相似文献
98.
Separating effects of climate change (ΔQc) and human activity (ΔQh) on stream discharge at the watershed scale is needed for developing adaptive measures to climate change. However, information is scarce in existing literature regarding whether such separating is feasible and whether reliable results can be produced. The objectives of this overview were to: (1) compare currently-used methods; (2) assess assumptions and issues of the methods; and (3) present a generic framework that overcomes possible issues. Based on the overview of fifteen recent representative studies, two methods can be used to estimate absolute magnitudes of ΔQc and ΔQh, while another method can be used to distinguish relative magnitudes of ΔQc versus ΔQh only. Because the methods’ fundamental assumptions about baseline versus altered period, water storage change and deep groundwater loss, precipitation-runoff relationship, hysteresis influence of human activity, and record of time series can seldom be satisfied for many watersheds, it is more realistic and practical to distinguish relative effects than to estimate absolute magnitudes of ΔQc and ΔQh. Moreover, a generic framework was presented for gauged watersheds with negligible groundwater loss, aiming to avoid misuse of the methods in practice. 相似文献
99.
R. Gutiérrez R. Gutiérrez-Sánchez A. Nafidi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(1):57-66
In this study, we propose a methodology to analyse the gradual secular trends present in the time evolution of certain endogenous
variables, which are of particular interest in environmental research. This methodology is based on modelling such variables
by nonhomogeneous stochastic diffusion processes, the trend functions of which may be made to depend on other, exogenous,
variables, which are controllable and which affect and model, in turn, the possible irregularities of such trends. The methodology
is applied to analyse the evolution of the emission of CO2 in Spain, and it is shown that the evolution of the Spanish GDP affects the trend component. These circumstances are considered
in the context of Spain’s non-compliance with the Kyoto protocol on controlling the emission of greenhouse gases. 相似文献
100.
对流层大气氧化性研究进展 总被引:2,自引:0,他引:2
对流层大气氧化性是对流层大气自我清洁能力的一个重要指标,对流层中大多数痕量气体都是通过氧化过程清除的.回顾近半个世纪以来对流层大气氧化性的研究历史,对流层大气氧化性的研究无论是从测量技术还是模式研究方面都已取得了一定的进展.工业革命以来,由于人类活动的影响,CO、NOx和碳氢化合物等大气污染物排放增多,使得全球对流层大气OH浓度呈下降趋势,未来对流层大气氧化性的变化很大程度上也取决于这些气体的排放情况.利用全球三维大气化学传输模式MOZART研究中国地区对流层大气OH自由基的分布和变化趋势表明,与全球OH自由基变化趋势不同,近10年来中国东部地区OH自由基浓度趋于增加.未来对流层大气氧化性研究的关键问题仍是OH自由基测量技术的提高问题,OH自由基观测结果是完善对流层光化学机制和改进大气化学模式的先决条件. 相似文献