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991.
Trevor Page Nick A. Chappell Keith J. Beven Barry Hankin Ann Kretzschmar 《水文研究》2020,34(24):4740-4754
There is increased interest in the potential of tree planting to help mitigate flooding using nature-based solutions or natural flood management. However, many publications based upon catchment studies conclude that, as flood magnitude increases, benefit from forest cover declines and is insignificant for extreme flood events. These conclusions conflict with estimates of evaporation loss from forest plot observations of gross rainfall, through fall and stem flow. This study explores data from existing studies to assess the magnitudes of evaporation and attempts to identify the meteorological conditions under which they would be supported. This is achieved using rainfall event data collated from publications and data archives from studies undertaken in temperate environments around the world. The meteorological conditions required to drive the observed evaporation losses are explored theoretically using the Penman–Monteith equation. The results of this theoretical analysis are compared with the prevailing meteorological conditions during large and extreme rainfall events in mountainous regions of the United Kingdom to assess the likely significance of wet canopy evaporation loss. The collated dataset showed that event Ewc losses between approximately 2 and 38% of gross rainfall (1.5 to 39.4 mm day−1) have been observed during large rainfall events (up to 118 mm day−1) and that there are few data for extreme events (>150 mm day−1). Event data greater than 150 mm (reported separately) included similarly high percentage evaporation losses. Theoretical estimates of wet-canopy evaporation indicated that, to reproduce the losses towards the high end of these observations, relative humidity and the aerodynamic resistance for vapour transport needed to be lower than approximately 97.5% and 0.5 to 2 s m−1 respectively. Surface meteorological data during large and extreme rainfall events in the United Kingdom suggest that conditions favourable for high wet-canopy evaporation are not uncommon and indicate that significant evaporation losses during large and extreme events are possible but not for all events and not at all locations. Thus the disparity with the results from catchment studies remains. 相似文献
992.
Life cycle of intraseasonal oscillation of summer SST in the western South China Sea 总被引:1,自引:0,他引:1
Intraseasonal oscillation (ISO, times-cales of 30~90 d) of summer sea surface temperature (SST) in the western South China Sea is studied using harmonic and empirical orthogonal function analyses of microwave observations by the tropical rainfall measuring mission satellite. Each summer from May to September, two or three ISO events occur off South Vietnam, with a typical period of approximately 50 d. The life cycle of these events from the initiation to decay of SST anomalies is described. 相似文献
993.
The Fingerdjupet Subbasin in the southwestern Barents Sea sits in a key tectonic location between deep rifts in the west and more stable platform areas in the east. Its evolution is characterized by extensional reactivation of N-S and NNE-SSW faults with an older history of Late Permian and likely Carboniferous activity superimposed on Caledonian fabrics. Reactivations in the listric NNE-SSW Terningen Fault Complex accommodated a semi-regional rollover structure where the Fingerdjupet Subbasin developed in the hangingwall. In parallel, the Randi Fault Set developed from outer-arc extension and collapse of the rollover anticline.N-S to NNE-SSW faults and the presence of other fault trends indicate changes in the stress regime relating to tectonic activity in the North Atlantic and Arctic regions. A latest Triassic to Middle Jurassic extensional faulting event with E-W striking faults is linked to activity in the Hammerfest Basin. Cessation of extensional tectonics before the Late Jurassic in the Fingerdjupet Subbasin, however, suggests rifting became localized to the Hammerfest Basin. The Late Jurassic was a period of tectonic quiescence in the Fingerdjupet Subbasin before latest Jurassic to Hauterivian extensional faulting, which reactivated N-S and NNE-SSW faults. Barremian SE-prograding clinoforms filled the relief generated during this event before reaching the Bjarmeland Platform. High-angle NW-prograding clinoforms on the western Bjarmeland Platform are linked to Early Barremian uplift of the Loppa High. The Terningen Fault Complex and Randi Fault Set were again reactivated in the Aptian along with other major fault complexes in the SW Barents Sea, leading to subaerial exposure of local highs. This activity ceased by early Albian. Post-upper Albian strata were removed by late Cenozoic uplift and erosion, but later tectonic activity has both reactivated E-W and N-S/NNE-SSW faults and also established a NW-SE trend. 相似文献
994.
周爱华 《中国天文和天体物理学报》1994,(3)
本文根据1980年2月至1989年11月期间SMM卫星的硬X射线(HXR)暴观测和GOES卫星的行星际质子积分流量观测,证认出48个共同样品,统计发现HXR暴的寿命Td(s)、峰值记数率Fx(c/s)和爆发期间发射的总光子数c的对数值,与行星际质子积分流量(被归一到耀斑本地)值Fp的对数值之间,均具有特别显著的线性关系,其中以logFp与logC的线性关系为最好,其拟合方程是logFp(>10MeV)=一0.604+0.538logC,相关系数r为0.70,相对标准误差为0.28.文中对质子积分流量的预测精度也作了讨论,并给出了置信区间。 相似文献
995.
A. B. Bhattacharya S. K. Kar M. K. Chatterjee R. Bhattacharya 《Annales Geophysicae》1998,16(2):183-188
The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Currently at: Department of Physics, Serampore College, Serampore, 712 201 West Bengal 相似文献
996.
L. Delobbe 《Boundary-Layer Meteorology》1998,89(1):75-107
Marine stratocumulus observations show a large variability in cloud droplet number concentration (CDNC) related to variability in aerosol concentration. Changes in CDNC modify the cloud reflectivity, but also affect cloud water content, cloud lifetime, and cloudiness, through changes in precipitation. In mesoscale models and general circulation models (GCMs), precipitation mechanisms are parameterized. Here we examine how the precipitation parameterization can affect the simulated cloud. Simulations are carried out with the one-dimensional version of the hydrostatic primitive equation model MAR (Modéle Atmosphérique Régional) developed at the Université catholique de Louvain. It includes a E- turbulence closure, a wide-band formulation of the radiative transfer, and a parameterized microphysics including prognostic equations for water vapour, cloud droplets and rain drops concentrations. In a first step, the model is used to simulate a horizontally homogeneous stratocumulus deck observed during the Atlantic Stratocumulus Transition Experiment (ASTEX) on the night of 12–13 June 1992. The observations show that the model is able to realistically reproduce the vertical structure of the cloud-topped boundary layer. In a second step, several precipitation parameterizations commonly used in mesoscale models and GCMs are tested. It is found that most parameterizations tend to overestimate the precipitation, which results in an underestimation of the vertically integrated liquid water content. Afterwards, using those parameterizations that are sensitive to CDNC, several simulations are performed to estimate the effect of CDNC variations on the simulated cloud. Based upon the simulation results, we argue that currently used parameterizations do not enable assessment of such a sensitivity. 相似文献
997.
用1980~1992年ECMWF的850hPa和200hPa资料设计了南亚季风和东亚季风指数,发现南海夏季风的暴发和撤退具有较大的年际差异,南海北部和南部夏季风的暴发和撤退时间也不一致.相关试验表明,南亚季风指数与中国大陆春、夏降水的相关分布型类似于东亚季风指数与降水的相关分布型,且相关系数略高.东亚冬季风指数以南海地区区域平均的850hPa经向风速或纬向风速为好.夏季风指数以南海地区或亚洲区域平均的850hPa和200hPa的纬向风速差最佳. 相似文献
998.
ENSO与宁夏夏季降水关系的分析 总被引:6,自引:0,他引:6
文中计算了太平洋地区各月海温距平与宁夏6、7、8月降水指数的相关,发现各月的高相关区在时间和空间上有所不同,分析了9次ENSO当年和次年宁夏各月降水变化的总体特征,发现宁夏夏季降水ENSO当年偏少,偏少程度占年偏少的65%~79%;ENSO次年偏多,偏多程度占年的59.2%~87.9%。对宁夏夏季降水和NINO指数的谱分析发现,宁夏6月降水没有明显周期,7月降水存在15年和3年左右的周期,8月降水只有3年周期,NINO指数存在3.75年左右的周期。对凝聚谱和位相谱值的分析结果表明,赤道东太平洋地区海温变化超前宁夏夏季降水变化1.67年,这就为宁夏的夏季降水长期预报提供了依据。 相似文献
999.
Interannual variability in western US precipitation 总被引:6,自引:0,他引:6
Low-frequency (interannual or longer period) climatic variability is of interest, because of its significance for the understanding and prediction of protracted climatic anomalies. Since precipitation is one of the key variables driving various hydrologic processes, it is useful to examine precipitation records to better understand long-term climate dynamics. Here, we use the multi-taper method of spectral analysis to analyze the monthly precipitation time series (both occurrence and amount) at a few stations along a meridional transect from Priest River, ID to Tucson, AZ. We also examine spectral coherence between monthly precipitation and widely used atmospheric indices, such as the central Northern Pacific (CNP) and southern oscillation index (SOI). This analysis reveals statistically significant ‘signals' in the time series in the 5–7 and 2–3 year bands. These interannual signals are consistent with those related to El-Niño southern oscillation (ENSO) and quasi-biennial variability identified by others. 相似文献
1000.
François Baudin Nicolas Fiet Rodolfo Coccioni Simone Galeotti 《Cretaceous Research》1998,19(6):701-714
The Selli Level is a marker-bed in the Umbria-Marche Apennines that represents the regional sedimentary expression of the Lower Aptain Oceanic Anoxic Event 1a. This one to three-metre-thick interval shows a remarkable uniformity on a regional scale, with a green to grey marly lower part overlain by black shales. Bulk geochemical studies and an examination of palynofacies were carried out on three sections in order to characterise the distribution and nature of the organic matter in the Selli Level which has been poorly known hitherto. The organic content is medium (0.5 to 2.9% TOC) in the basal part and higher (4.5% on average, and up to 18% TOC) in the black shales. Pyrolysis and palynological data indicate that the organic matter is mainly of marine origin. The geochemical characteristics of the Selli Level are compared to other, more or less organic-rich marker-beds in the Cretaceous succession of the Umbria-Marche Apennines.