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71.
湖南省耕地资源态势与粮食安全研究   总被引:8,自引:0,他引:8  
文章分析了湖南省耕地面积对粮食生产贡献率随时间变化的特点,以及耕地退化对粮食生产的影响状况。研究表明,耕地资源数量和质量的变化对粮食生产构成持久的约束作用,耕地资源稀缺已成为制约粮食安全的瓶颈。为了实现粮食安全,应采用的根本措施在于保持耕地数量平衡,防治土地资源退化,加强全民粮食安全意识,建立复合高效农田生态经济系统,合理开发后备耕地资源等。  相似文献   
72.
1∶10 000地形图植被要素的采集和更新较为复杂,考虑国土部门现有的现势性较强的土地利用现状数据可以用来补充1∶10 000地形图中的植被信息,积极开展试验.本文作者利用广东省现有的土地利用现状数据,结合航空(卫星)正射影像图、1∶10 000矢量数据进行了充分试验,走出了一条植被更新的新路子,为省级基础地理信息数据库的完善和更新提供了一种新方法.  相似文献   
73.
This study investigates urbanization and its potential environmental consequences in Shanghai and Stockholm metropolitan areas over two decades. Changes in land use/land cover are estimated from support vector machine classifications of Landsat mosaics with grey-level co-occurrence matrix features. Landscape metrics are used to investigate changes in landscape composition and configuration and to draw preliminary conclusions about environmental impacts. Speed and magnitude of urbanization is calculated by urbanization indices and the resulting impacts on the environment are quantified by ecosystem services. Growth of urban areas and urban green spaces occurred at the expense of cropland in both regions. Alongside a decrease in natural land cover, urban areas increased by approximately 120% in Shanghai, nearly ten times as much as in Stockholm, where the most significant land cover change was a 12% urban expansion that mostly replaced agricultural areas. From the landscape metrics results, it appears that fragmentation in both study regions occurred mainly due to the growth of high density built-up areas in previously more natural/agricultural environments, while the expansion of low density built-up areas was for the most part in conjunction with pre-existing patches. Urban growth resulted in ecosystem service value losses of approximately 445 million US dollars in Shanghai, mostly due to the decrease in natural coastal wetlands while in Stockholm the value of ecosystem services changed very little. Total urban growth in Shanghai was 1768 km2 and 100 km2 in Stockholm. The developed methodology is considered a straight-forward low-cost globally applicable approach to quantitatively and qualitatively evaluate urban growth patterns that could help to address spatial, economic and ecological questions in urban and regional planning.  相似文献   
74.
为了从取样、测量到评估分析全流程提高土地砾化程度监测指标——地表砾石覆盖度的监测评估精度;以内蒙古高原西部的阿拉善盟和巴彦淖尔市为研究区;设计不同尺寸的样方;开展二次平均状态取样方法研究。采用地面测量法和测量盘法对比确定小样方中砾石覆盖度的最佳测量方法;通过大、小样方平均数和中位数的统计特征分析确定大样方及样地砾石覆盖度的最佳评估方式。同时;探讨了构建“仿生态学”的必要性和初步思路。结果表明:(1) 二次平均状态法通过缩减样方尺寸、增加样本数量的方式;使样本更具代表性;且样方尺寸的减小可使测量盘的尺寸随之缩减;有助于进一步提高地表砾石覆盖度测量精度。(2) 由小样方到大样方再到样地;数据的离散程度越来越小;右偏及尖峰型分布越来越明显;研究区砾化程度的总体特征越来越凸显;同时大样方及样地的砾石覆盖度、地表单位面积砾石质量相关性较高;说明基于二次平均状态取样的土地砾化程度监测结果具有较高的精确度和稳定性;可用于改进土地砾化程度监测流程及精度;并提高野外工作效率。  相似文献   
75.
    
Surface uplift occurs as a result of tectonic uplift related to crustal deformation and isostatic compensation due to surface erosion. To determine and quantify the key controlling factors responsible for surface uplift in the south-eastern Tibetan Plateau, we calculated isostatic compensation using topographic data along five wide-angle seismic profiles across the Chuandian Block, Indochina Block, and South China Plate, and examined the correlations between tectonic uplift and each crustal layer thickness. The average isostatic compensation caused by surface erosion is 340–480 m, which is approximately 13–26% of the total surface uplift. The geodynamic implications in relation to the Global Positioning System, focal mechanisms (P axes), seismic anisotropy (Pms splitting), and low-velocity zones were also investigated. The low-velocity zones with long-distance southward extension seemed to be significantly reduced, and were divided into two branches by resistance from the inner zone of the Emeishan large igneous province (ELIP) when it is extending into the southern Chuandian Block. The lower crustal thickening related to low-velocity zones reconstructed a partial crustal structure of the ELIP, and contributed at least 53–62% of the total surface uplift at the western branch, and almost 46–65% at the eastern branch. With the limitations imposed by the rigidity of the South China Plate and Indochina Block, the south-eastern motion of the upper-middle crust was strongly decoupled with southward lower crustal flow, as revealed by the unmatched pattern between P axes and Pms splitting. The south-eastward motion of southern Chuandian Block resulted in upper-crustal folding in the W–E direction, upper-crustal thrusting in the N–S direction, and contributed approximately 9–28% of the total surface uplift in some locations. We emphasize the indispensability of upper-crustal shortening in the frontal zone of the south-eastern Tibetan Plateau and introduce the transitional characteristics of the southern Chuandian Block, from typical lower crustal flow to coupled crustal brittle shortening.  相似文献   
76.
在二元土地所有制下,中国城市市区的建设用地、农村和城市郊区依法征收后新增的建设用地,属于国家所有;城市市区以外以及法律规定由国家所有土地以外的农民宅基地和其他建设用地,属于农民集体所有。文登市金岭山庄被位于城区的经济强村西楼兼并后,土地资源得以高效利用,加速了城市化进程,成为城乡统筹发展的典范。  相似文献   
77.
78.
    
Reforestation of cleared land has the potential to reduce groundwater recharge, salt mobilization and streamflow. Stream salinity change is the net result of changes in stream salt load and streamflow. The net effect of these changes varies spatially as a function of climate, terrain and land cover. Successful natural resource management requires methods to map the spatial variability of reforestation impacts. We investigated salinity data from 2000 bores and streamflow and salinity measurements from 27 catchments in the Goulburn–Broken region in southeast Australia to assess the main factors determining stream salinity and opportunities for management through reforestation. For groundwater systems of similar geology, relationships were found between average annual rainfall and groundwater salinity and between groundwater salinity and low‐flow salinity. Despite its simplicity, we found that the steady‐state component of a simple conceptual coupled water–salt mass balance model (BC2C) adequately explained the spatial variation in streamflow and salinity. The model results suggest the efficiency of afforestation to reduce stream salinity could be increased by more than an order of magnitude through spatial planning. However, appreciable reductions in stream salinity in large rivers through land cover change alone would still require reforestation on an unprecedented scale. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
79.
通过LI-8100土壤碳通量测定仪对中亚热带山区不同土地利用方式土壤呼吸进行测定与分析.结果表明,不同土地利用方式土壤温度变化趋势较为一致,峰值出现在16:00,但坡耕地均出现在14:00;不同土地利用方式土壤呼吸速率昼夜变化趋势大致呈单峰变化,呼吸速率在12:00—16:00之间达到一天的最大值,而在6:00达到最小值,但杉木林与木荷林土壤呼吸速率在夏季呈现出不规则的多峰变化,不同季节呼吸速率最大值出现的时间不同;杉木林与木荷林不同季节的土壤呼吸速率的目变化幅度较小,果园的最大;土壤呼吸速率的均值大小顺序为:经济林〉木荷林〉坡耕地〉杉木林〉果园,但不同土地利用方式间土壤呼吸速率差异不显著(P〉0.05).不同土地利用方式土壤呼吸Q10值的季节变化中,杉木、木荷2种人工林用地冬季Q10值最大,最小值分别出现在夏季与秋季,而坡耕地、经济林与果园3种土地利用方式以春季的Q10值最大,秋季最小;Q10值随土壤碳质量的降低而增大.  相似文献   
80.
基于GIS的黄河三角洲盐碱地改良分区   总被引:41,自引:0,他引:41  
黄河三角洲盐碱地面积超过总面积的70%,而盐碱地改良分区是因地制宜,综合治理盐域地的前提,通过综合运用地理信息系统的各种空间数据分析功能,将黄河三角洲土地盐碱化现状分为:非盐碱地,轻度盐碱地,中度盐碱地,重度盐碱地,滩涂5个区,并结合地下水长期观测资料,进行成因分析,建立了黄河三角洲盐碱地改良分区模型,立足土地盐碱化的现状,充分考虑地下水埋深和矿化度,把黄河三角洲盐碱地按改良难易程度分为:易改良区,较难改良区,难改良区,近期不宜作改良区,并针对不同的盐碱地改良区提出了相应的土壤改良对策。  相似文献   
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