全文获取类型
收费全文 | 579篇 |
免费 | 93篇 |
国内免费 | 128篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 251篇 |
地球物理 | 204篇 |
地质学 | 130篇 |
海洋学 | 104篇 |
天文学 | 34篇 |
综合类 | 18篇 |
自然地理 | 48篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 21篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 28篇 |
2018年 | 21篇 |
2017年 | 31篇 |
2016年 | 26篇 |
2015年 | 34篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 27篇 |
2011年 | 37篇 |
2010年 | 21篇 |
2009年 | 37篇 |
2008年 | 38篇 |
2007年 | 47篇 |
2006年 | 29篇 |
2005年 | 31篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 22篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有800条查询结果,搜索用时 31 毫秒
221.
本文归纳总结了在绝热、无耗散对称二维大气中定常广义地转流稳定性分析中的扰动方程组的基本特征,并将其概括为具有这类问题共同基本特征的统一形式的扰动方程组的定解问题。在此基础上,统一地证明了:1)由统一的扰动方程组所确定的定解问题的解是存在唯一的;2)基态的性质是由Λmin(G)的性质决定的:a.当Λmin(G)>0时,基态是稳定的;b.当Λmin(G)<0时,基态是不稳定的。3)基态的全局稳定性质可以通过局部稳定性分析来确定;4)合理的、充分简化的局部稳定性分析结论在局部分析中是严格有效的 相似文献
222.
青藏高原的抬升和夷平过程对气候与环境的影响 总被引:4,自引:0,他引:4
系统地讨论了高原隆起的早第三纪至现代青藏高原的7次抬升过程对气候和环境的影响,应用气象学理论分析了当时气候形成的原因,主要结论;(1)高原隆起前的干热气候是由于隆起全球地势平坦,致使大气热机效率很低之效;(2)渐新世初高原的水平尺度达到斜压大气地转适应的临界尺度,大气环流从南北两极“两涡对峙”突变成地球三极的“三涡鼎立”气候发生突变;(3)分析了2.5Ma时高原抬升到2000m这一重要临界高度后大 相似文献
223.
V. I. Kondaurov 《Pure and Applied Geophysics》1986,124(4-5):749-757
In this paper the processes of rock deformation are discussed, which are accompanied by an accumulation of defects or by continuous fracturing. The influence of fluids and of the electrical and magnetic fields is neglected. A model of fracturing, based on some energy consideration is introduced. 相似文献
224.
225.
In this paper, benefits from increasing cross-border cooperation under future CO2 commitments in the Nordic countries are examined and evaluated. Four cooperative strategies are analyzed and valued separately: cross-border electricity trade, cross-border emission-permit trade, the introduction of a trans-Nordic natural gas transmission grid, and, finally, utilization of all these three strategies simultaneously. The valuation is done under varying CO2 commitments and under three different scenarios for future energy demand and technological development. In conducting this analysis, the energy-systems model-generator MARKAL (MARKet ALlocation) was used to model the Nordic energy system. It is shown that all cooperative strategies do lower the abatement costs considerably, especially if the strategy including full cooperation is utilized. In this case, additional costs from meeting CO2 targets may be at least halved for commitments less than 10% reduction until 2050 based on emissions in 1995. No significant difference between low and high CO2 commitments could be observed in the size of the benefits from cooperation, expressed in billions (109) of Swedish crowns. Benefits from cooperation are generally larger for scenarios including relatively higher future energy demand. 相似文献
226.
R. Dobry A. Pecker G. Mavroeidis M. Zeghal B. Gohl D. Yang 《Soil Dynamics and Earthquake Engineering》2003,23(6):483-495
A global energy analysis is presented of three static unloading–reloading foundation lateral loading cycles, calculated using the nonlinear finite element (FE) program DYNAFLOW. This simulates seismic action on an offshore pier foundation in the Rion-Antirion Bridge in Greece, located in deep-sea water (65 m). A cyclic horizontal force is applied at a height of 30 m to a rigid raft 78 m in width placed on the surface of an idealized 2-layer soil profile consisting of a 3.5 m man-made gravel layer over soft deep natural clay, with elastic vertical steel inclusions reinforcing the soil. Results of the two-dimensional FE run are used for the energy analysis. It is verified that for the three cycles, the sum of energies associated with the external forces and moments, mostly dissipated through hysteresis loops, is about equal to the sum of the total internal energies dissipated or stored in the system. For the smaller loops almost all energy is dissipated in the soil, while for the largest loop about half of the energy is dissipated by horizontal sliding at the raft-soil interface. Global damping ratios obtained from the areas of the horizontal and rocking moment hysteresis loops are about double of those computed from the corresponding static backbone curves using the Masing criterion. 相似文献
227.
228.
DAVID MERCER 《The Australian geographer》2003,34(1):91-121
Up until very recently--and in marked contrast to such countries as Spain, Denmark and Germany--Australia generated hardly any electricity from the wind. Driven largely by the mandatory targets embodied in the Renewable Energy (Electricity) Act 2000 (Commonwealth) this situation is now changing. Australia has several operational small- to medium-sized wind energy power stations in Western Australia, Victoria, New South Wales and Queensland. But--in the face of often strong local opposition--the Australian Wind Energy Association is keen to increase the number and scale of such projects. This paper outlines recent overseas developments in wind energy and then focuses on the environmental and planning dilemmas posed by this form of electricity production. Particular attention is focused on a highly controversial wind energy proposal in south-western Victoria, the Portland Wind Energy Project (PWEP). The argument presented is that wind is only one of a number of possible renewable energy options, that coastal landscapes are an 'endangered species', and that it is time for geographers to revisit methodologies concerned with evaluating landscape beauty and debating the place of landscape values within the ecologically sustainable development paradigm. 相似文献
229.
海-陆-气全球耦合模式能量收支的误差 总被引:4,自引:0,他引:4
通过分析GOALS模式两个版本GOALS 1.1和GOALS 2的能量收支 ,并与观测对比 ,结果表明 :模式模拟的地表净短波辐射通量在高纬地区偏低 ,而净长波辐射通量又偏高 ,导致极地表面温度偏低 ,感热通量在高纬地区为很高的负值。而在陆地上感热加热作用显著偏强 ,使地表有较大的向上净能量给大气 ,引起陆地上有些暖中心也偏强 ,这也解释了模式模拟地表面空气温度场的误差原因。海洋上潜热通量偏低 ,特别是在副热带洋面上偏少更明显。陆地上的欧亚和北美大陆大部分地区潜热通量仍偏低。这也是模式降水在大部分地区偏少的重要原因。两模式大气顶OLR偏低的模拟主要是在中低纬度 ,大气顶净短波辐射通量的模拟在中低纬度虽然与NCEP结果接近 ,但与地球辐射收支试验ERBE资料比较仍偏小较多 ,说明改进中低纬度云 辐射参数化方案对改进全球能量收支的模拟有重要意义。GOALS 2模式中诊断云方案模拟的云量除赤道地区外普遍偏小 ,尤以中纬度为甚 ,造成那里能量收支出现大的误差 ,这表明了更好的云参数化方案的引入是今后模式发展的重要任务之一 相似文献
230.
沙漠能源生态圈概念、内涵及发展模式 总被引:1,自引:1,他引:0
沙漠地区既是中国重要的能源基地,也是生态环境脆弱区和发展落后地区,如何在保护沙漠生态环境的前提下,充分开发利用沙漠丰富资源,同时又带动地区经济发展和改善民生?首先基于生态学、管理学、自然地理学、系统科学等相关理论,结合国内外沙漠能源开发及沙漠治理、生态修复等方面最新研究进展,运用能源互联网思维,构建了包涵沙漠治理、生态修复、脱贫攻坚、乡村振兴、能源建设、经济发展等要素的生态圈结构模型,提出一个合作共赢、基于沙漠能源、以电力为核心的沙漠能源生态圈概念;然后对沙漠能源生态圈内涵及特征进行解析,并从经济、社会、生态三方面对其效益进行阐述;最后,探讨了沙漠能源生态圈发展模式,并从能源、生态、经济、国情、战略五方面阐述了沙漠能源生态圈发展愿景。 相似文献