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171.
Brazilian semi‐arid regions are characterized by water scarcity, vulnerability to desertification, and climate variability. The investigation of hydrological processes in this region is of major interest not only for water planning strategies but also to address the possible impact of future climate and land‐use changes on water resources. A hydrological distributed catchment‐scale model (DiCaSM) has been applied to simulate hydrological processes in a small representative catchment of the Brazilian northeast semi‐arid region, and also to investigate the impact of climate and land‐use changes, as well as changes associated with biofuel/energy crops production. The catchment is part of the Brazilian network for semi‐arid hydrology, established by the Brazilian Federal Government. Estimating and modelling streamflow (STF) and recharge in semi‐arid areas is a challenging task, mainly because of limitation in in situ measurements, and also due to the local nature of some processes. Direct recharge measurements are very difficult in semi‐arid catchments and contain a high level of uncertainty. The latter is usually addressed by short‐ and long‐time‐scale calibration and validation at catchment scale, as well as by examining the model sensitivity to the physical parameters responsible for the recharge. The DiCaSM model was run from 2000 to 2008, and streamflow was successfully simulated, with a Nash–Sutcliffe (NS) efficiency coefficient of 0·73, and R2 of 0·79. On the basis of a range of climate change scenarios for the region, the DiCaSM model forecasted a reduction by 35%, 68%, and 77%, in groundwater recharge (GWR), and by 34%, 65%, and 72%, in streamflow, for the time spans 2010–2039, 2040–2069, and 2070–2099, respectively, could take place for a dry future climate scenario. These reductions would produce severe impact on water availability in the region. Introducing castor beans to the catchment would increase the GWR and streamflow, mainly if the caatinga areas would be converted into castor beans production. Changing an area of 1000 ha from caatinga to castor beans would increase the GWR by 46% and streamflow by 3%. If the same area of pasture is converted into castor beans, there would be an increase in GWR and streamflow by 24% and 5%, respectively. Such results are expected to contribute towards environmental policies for north‐east Brazil (NEB), and to biofuel production perspectives in the region. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
172.
An ensemble of stochastic daily rainfall projections has been generated for 30 stations across south‐eastern Australia using the downscaling nonhomogeneous hidden Markov model, which was driven by atmospheric predictors from four climate models for three IPCC emissions scenarios (A1B, A2, and B1) and for two periods (2046–2065 and 2081–2100). The results indicate that the annual rainfall is projected to decrease for both periods for all scenarios and climate models, with the exception of a few scenarios of no statistically significant changes. However, there is a seasonal difference: two downscaled GCMs consistently project a decline of summer rainfall, and two an increase. In contrast, all four downscaled GCMs show a decrease of winter rainfall. Because winter rainfall accounts for two‐thirds of the annual rainfall and produces the majority of streamflow for this region, this decrease in winter rainfall would cause additional water availability concerns in the southern Murray–Darling basin, given that water shortage is already a critical problem in the region. In addition, the annual maximum daily rainfall is projected to intensify in the future, particularly by the end of the 21st century; the maximum length of consecutive dry days is projected to increase, and correspondingly, the maximum length of consecutive wet days is projected to decrease. These changes in daily sequencing, combined with fewer events of reduced amount, could lead to drier catchment soil profiles and further reduce runoff potential and, hence, also have streamflow and water availability implications. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
173.
Three satellite-tracked drifting buoys released in the south equatorial current in the Indian Ocean followed the path of the
current moving westward approximately zonally in the vicinity of 10 S latitude. On nearing the east coast of Africa two buoys
moved north and the third moved south. Over the open sea regime the buoys moved with a speed of approximately 30 cm/s at an
angle of about 35° to the left of the wind. The overall tendencies seen in the buoy drift are similar to those observed elsewhere
in the world oceans. 相似文献
174.
广东地区河流阶地和冲积扇沉积物中砂岩砾石风化晕随时间增厚。风化晕生长速度呈指数衰减,并拟合于下列公式:T 1485D4.13这里T=时间,以年表示,D=沉积物表部约50块砾石风化晕厚度的加权平均值,以毫米表示。利用风化晕厚度确定出广东地区河流第一和第二级阶地分别为1000—13300年和8600—26500年,肇庆盆地北部山前地带第Ⅰ和第Ⅱ级冲积扇分别为51500年和24400年。同时,在构造地貌变形分析的基础上,估算出本区三条主要北东向断裂带在晚更新世—中全新世的垂直断层作用速度为0.6—1.6毫米/年,中全新世甚或晚更新世晚期以来的活动速度极小 相似文献
175.
176.
目前普遍认为我国南方上、下二叠统之间存在一平行不整合,并以此代表东吴运动。本文从江西乐平组垂向与横向岩性、岩相变化的资料出发,提出不主张使用“东吴运动”这一专名。所谓“东吴运动”实际上是一次升降运动,规模很有限。时间从茅口期开始一直延续至龙潭期末,大约占有1500万年之久,其中包括了三次次一级的升降。乐平组及其各亚组均有明显的穿时现象。上下二叠统之间总体说来为连续沉积,并不存在平行不整合。 相似文献
177.
赣西南下奥陶统樟木曲组笔石带的修正和补充 总被引:2,自引:0,他引:2
本文在对笔石作系统研究的基础上,对樟木曲组的笔石带进行了补充和修正。由原来的9个笔石带划分为11个笔石带,厘定了各笔石带的范围和笔石群的总体面貌,并逐带与国内外进行了对比。文内还涉及到宁国阶的顶界、上下两层下垂时笔石以及关于肿笔石与心笔石混生的问题。 相似文献
178.
近年来,在江西中西部黄龙组底部发现了Pseudostaffella,由此涉及到了黄龙组底部的地层时代及对比问题。根据匕高石坎尾剖面上类化石的分布和动物群性质,江西黄龙组底部与Eostaffella、Schubertella共生的Pseudostaffella和贵州、湖南Pseudostaffella带组合面貌相差甚远。江西中西部至今不存在确切的Pseudostaffella带。 相似文献
179.
180.
本文分析了广东山区工业发展的有利条件与存在问题,提出山区工业发展要采取超常规,跳跃式发展战略,立足本地优势资源,发展资源型工业,重点发展以生物资源为原料的工业,把资源优势转变为经济优势,同时根据市场需求发展市场型工业,尤其高新技术工业;既要立足理现有工业,加速改造挖潜,促其上水平、上规模、出效益、又要选准项目,大胆投入,发展有造血功能的骨干企业并调整和优化工业结构。 相似文献