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排序方式: 共有908条查询结果,搜索用时 17 毫秒
71.
气候变化及其对农作物生产潜力的影响   总被引:6,自引:0,他引:6  
利用国家气象中心整编的1951—1990年全国160站年、月平均气温和总降水量,的资料序列,计算和分析了我国近40年的气候变化,讨论了我国气候变化的区域性和季节性差异;计算了各站的年作物光温生产潜力,探讨了气象变化对农业生产的影响。  相似文献   
72.
ABSTRACT

For evaluating the progresses towards achieving the Sustainable Development Goals (SDGs), a global indicator framework was developed by the UN Inter-Agency and Expert Group on Sustainable Development Goals Indicators. In this paper, we propose an improved methodology and a set of workflows for calculating SDGs indicators. The main improvements consist of using moderate and high spatial resolution satellite data and state-of-the-art deep learning methodology for land cover classification and for assessing land productivity. Within the European Network for Observing our Changing Planet (ERA-PLANET), three SDGs indicators are calculated. In this research, harmonized Landsat and Sentinel-2 data are analyzed and used for land productivity analysis and yield assessment, as well as Landsat 8, Sentinel-2 and Sentinel-1 time series are utilized for crop mapping. We calculate for the whole territory of Ukraine SDG indicators: 15.1.1 – ‘Forest area as proportion of total land area’; 15.3.1 – ‘Proportion of land that is degraded over total land area’; and 2.4.1 – ‘Proportion of agricultural area under productive and sustainable agriculture’. Workflows for calculating these indicators were implemented in a Virtual Laboratory Platform. We conclude that newly available high-resolution remote sensing products can significantly improve our capacity to assess several SDGs indicators through dedicated workflows.  相似文献   
73.
ABSTRACT

The overarching goal of this study was to perform a comprehensive meta-analysis of irrigated agricultural Crop Water Productivity (CWP) of the world’s three leading crops: wheat, corn, and rice based on three decades of remote sensing and non-remote sensing-based studies. Overall, CWP data from 148 crop growing study sites (60 wheat, 43 corn, and 45 rice) spread across the world were gathered from published articles spanning 31 different countries. There was overwhelming evidence of a significant increase in CWP with an increase in latitude for predominately northern hemisphere datasets. For example, corn grown in latitude 40–50° had much higher mean CWP (2.45?kg/m³) compared to mean CWP of corn grown in other latitudes such as 30–40° (1.67?kg/m³) or 20–30° (0.94?kg/m³). The same trend existed for wheat and rice as well. For soils, none of the CWP values, for any of the three crops, were statistically different. However, mean CWP in higher latitudes for the same soil was significantly higher than the mean CWP for the same soil in lower latitudes. This applied for all three crops studied. For wheat, the global CWP categories were low (≤0.75?kg/m³), medium (>0.75 to <1.10?kg/m³), and high CWP (≥1.10?kg/m³). For corn the global CWP categories were low (≤1.25?kg/m³), medium (>1.25 to ≤1.75?kg/m³), and high (>1.75?kg/m³). For rice the global CWP categories were low (≤0.70?kg/m³), medium (>0.70 to ≤1.25?kg/m³), and high (>1.25?kg/m³). USA and China are the only two countries that have consistently high CWP for wheat, corn, and rice. Australia and India have medium CWP for wheat and rice. India’s corn, however, has low CWP. Egypt, Turkey, Netherlands, Mexico, and Israel have high CWP for wheat. Romania, Argentina, and Hungary have high CWP for corn, and Philippines has high CWP for rice. All other countries have either low or medium CWP for all three crops. Based on data in this study, the highest consumers of water for crop production also have the most potential for water savings. These countries are USA, India, and China for wheat; USA, China, and Brazil for corn; India, China, and Pakistan for rice. For example, even just a 10% increase in CWP of wheat grown in India can save 6974 billion liters of water. This is equivalent to creating 6974 lakes each of 100?m³ in volume that leads to many benefits such as acting as ‘water banks’ for lean season, recreation, and numerous ecological services. This study establishes the volume of water that can be saved for each crop in each country when there is an increase in CWP by 10%, 20%, and 30%.  相似文献   
74.
大庆深部致密砂砾岩含气储层产能预测   总被引:4,自引:0,他引:4  
气层产能预测是气藏工程研究中用于指导气井以及气田合理生产的重要工作和任务,它在气田整体评价和高效开发进程中具有很强的预见性和主动性。讨论了大庆深部致密砂砾岩含气储层的产能与测井响应之间的关系,探讨了根据测井资料应用人工神经网络技术预测含气储层产能的方法。利用已知气井测试结果和测井资料作为网络的训练样本。根据网络学习训练结果,输入储集层的测井资料等静态参数,可预测该储集层的产能。根据这种关系采用神经网络技术实现了测井对产能的预测评价,从而为大庆深部致密砂砾岩含气储层的开发提供了一定的依据。  相似文献   
75.
耕地粮食生产潜力及人口承载力研究——以长清县为例   总被引:11,自引:1,他引:10  
以长清县为例 ,利用 GIS技术和遥感数据 ,按照“机制法”原理计算耕地资源粮食生产潜力。重点是因地制宜、科学确定并计算土壤有效系数和社会有效系数 ,从而得到耕地生产潜力和社会生产潜力像元分布数据。在此基础上 ,进行粮食增产潜力计算 ,并预测未来人口数量发展趋势 ,探讨未来的人口承载力问题。结果表明 :该县粮食增产潜力巨大 ,但是粮食问题仍不容乐观。  相似文献   
76.
发展我国知识经济 ,必须以邓小平“科学技术是第一生产力”思想为理论基石 ,符合社会主义市场经济特征的激励知识创新活动的“经济组织”为基本前提。在此基础上 ,构建起符合我国国情的由相互联系、制约和影响的九大要素为基本框架的知识创新机制 ,是当前社会经济环境条件下的最优制度安排。  相似文献   
77.
δ18 O and δ13C of G.sacculifer have been measured in five cores from the northern Indian Ocean. In addition, high resolution analysis (1 to 2 cm) was performed on one core (SK-20-185) for both δ18O and gd13C in five species of planktonic foraminifera. CaCO3 variation was measured in two cores. The results, presented here, show that
–  • the summer monsoon was weaker during 18 ka and was stronger during 9 ka, relative to modern conditions;
–  • δ13C variations are consistent with independent evidence that shows that during the last glacial maximum (LGM; 18 ka) the upwelling was reduced while during 9 ka it was vigorous;
–  • calculation of CaCO3 flux shows that the LGM was characterized by low biogenic productivity in the Arabian Sea while during the Holocene productivity increased by ∼65%, as a direct consequence of the changes in upwelling. Similar changes (of lesser magnitude) are also seen in the equatorial Indian Ocean. The amount of terrigenous input into the Arabian Sea doubled during LGM possibly due to the higher erosion rate along the west coast.
–  • δ18O values indicate that the Arabian Sea was saltier by 1 to 2%o during LGM. The northern part was dominated by evaporation while in the equatorial part there was an increased precipitation.
  相似文献   
78.
区域资源定量评价中面金属量法的应用   总被引:1,自引:0,他引:1  
地球化学方法被普遍应用于矿产资源评价,但多数方法都只是基于地球化学数据本身而进行的,较少考虑除成矿物质来源之外的诸如构造、地层等地质环境的影响。文章运用面金属量法,在充分研究地质因素的基础上,确定了预测单元及地球化学背景值,在一定程度上屏蔽了虚假资源量,对东天山地区铜的资源量进行了定量评价。预测认为,东天山地区铜的资源潜力巨大。  相似文献   
79.
A multi-equation spatial econometric model is used to explain variations across EU regions in manufacturing productivity growth based on recent theoretical developments in urban economics and economic geography. The paper shows that temporal and spatial parameter homogeneity is an unrealistic assumption, contrary to what is typically assumed in the literature. Constraints are imposed on parameters across time periods and between core and peripheral regions of the EU, with the significant loss of fit providing overwhelming evidence of parameter heterogeneity, although the final model does highlight increasing returns to scale, which is a central feature of contemporary theory.   相似文献   
80.
论我国河流水环境容量空间分异与工业生产力的宏观布局   总被引:7,自引:2,他引:5  
鲍全盛  姜文来 《地理科学》1998,18(3):205-212
在分析我国各地区经济发展与河流水环境容量资源之间矛盾关系及其成因的基础上,揭示了水环境容量与生产力宏观布局之间的关系,并探讨了根据河流水环境容量条件进行生产力宏观布局与调整产业结构的策略。水环境容量是影响生产力宏观布局的重要因素之一,在工业生产力布局时,如果能充分考虑水环境容量资源的承载力,则能够以最小的经济代价,换取最佳的环境效益,使经济与环境得以持续、协调发展,促进区域经济增长。  相似文献   
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