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231.
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Zhiguo Rao Haichun Guo Jiantao Cao Fuxi Shi Guodong Jia Yunxia Li Fahu Chen 《第四纪科学杂志》2020,35(8):1036-1045
Recent results indicate contrasting Holocene moisture histories at different elevations in arid central Asia (ACA). However, relatively little is known about Holocene temperature changes at different elevations. Here we report an independently dated peat brGDGTs-based MBT'5ME record from the Narenxia peatland (NRX) in the southern Altai Mountains. The record suggests a long-term warming trend since ~7.7 cal. kyr bp , with a warmer stage during ~7–5.5 cal. kyr bp , a cold stage during ~5.5–4 cal. kyr bp , and a warming trend over the last ~4 kyr. The long-term warming trend indicated by the NRX MBT'5ME record is largely consistent with Holocene temperature records from nearby sites covering an altitudinal range of ~1700–4100 m above sea level. This consistent long-term warming trend at different elevations differs from the long-term Holocene drying/wetting trends at high/low elevations of the Altai Mountains. We propose that the warming trend and consequent permafrost thawing at high elevations could have resulted in increased meltwater runoff, which would have contributed to the long-term wetting trend at low elevations. Our findings potentially provide an improved understanding of regional climate change and associated water resource availability, with implications for their possible future status. 相似文献
233.
黑河上游祁连山区土壤可培养细菌群落生境的垂直分异特征 总被引:4,自引:4,他引:0
利用PYGV、 R2A、 NB和Czapek 4种培养基, 研究了不同海拔下黑河上游祁连山区土壤细菌群落结构的变化规律.结果表明: 可培养细菌数量为4.6×106~37.0×106CFU·g-1, 随海拔升高明显减少; 基于16S rRNA基因序列分析共发现了7个门、 19个属、 26种细菌, 其中Agreia pratensis, Mucilaginibacter ximonensis, 嗜冷冷杆菌(Cryobacterium psychrophilum)和氧化节杆菌(Arthrobacter oxydans)四种细菌是优势种; 嗜冷冷杆菌的相对丰度在高海拔地区明显增加, Agreia pratensis的相对丰度随海拔升高而降低; 细菌的多样性随海拔升高呈现出先升高后降低的趋势. 冗余分析(RDA)显示, 可培养细菌数量与海拔呈显著负相关, 细菌的多样性与植被指数和土壤理化性质均存在明显的相关关系, 说明可培养细菌数量主要受海拔的影响, 而植被和土壤理化性质是影响细菌群落多样性的主要因素. 相似文献
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Luca Carturan Giovanni A. Baldassi Aldino Bondesan Simone Calligaro Alberto Carton Federico Cazorzi Giancarlo Dalla Fontana Roberto Francese Alberto Guarnieri Nicola Milan Daniele Moro Paolo Tarolli 《Geografiska Annaler: Series A, Physical Geography》2013,95(1):79-96
Smaller glaciers (<0.5 km2) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the Italian Alps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the European Alps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods. 相似文献
236.
Quantifying changes of effective springshed area and net recharge through recession analysis of spring flow 下载免费PDF全文
The average flow of Silver Springs, one of the largest magnitude springs in Central Florida, declined 32% from 2000 to 2012. The average groundwater head in the springshed declined 0.14 m, and the spring pool altitude increased 0.24 m during the same period. This paper presents a novel explanation of the spring flow recession curve for Silver Springs using the Torricelli model, which uses the groundwater head at a sentinel well, the spring pool altitude and the net recharge to groundwater. The effective springshed area and net recharge (defined as recharge minus groundwater pumping and evapotranspiration) were estimated based on the observed recession slopes for spring flow, groundwater head and spring pool altitude. The results indicate that the effective springshed area continuously declined since 1989 and the net recharge declined since the 1970s with a significant drop in 2002. Subsequent to 2002, the net recharge increased modestly but not to the levels prior to the 1990s. The reduction in net recharge was caused by changes in hydroclimatic conditions including precipitation and air temperature, along with groundwater withdrawals, which contributed to the declined spring flow. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
237.
根据区域自动气象站质量控制方法,结合广西区域自动站分布特点和业务需要,对温度、气压、风要素的质量控制参数进行高度订正,经过比较,通过高度差订正后,各要素的质量控制参数更具有代表性。 相似文献
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广西区域自动气象站建站的时间最长不到7年,大部分站点分布在不同高度的丘陵,因资料时间序列短,利用本站资料直接统计气候界限值,无法真实代表本站的气候界限值范围.为此,引入高度差订正来解决这个问题.先选取与之临近的国家气象站点作为参考站,统计出参考站点的气候界限值,再根据气温、气压、风速随高度变化的相关规律,对参考站的气候界限值进行高度订正,得出区域自动气象站点的气候界限值,经过比较,通过高度差订正后,各要素的气候界限值更具有代表性和可用性.该方法的统计值已在广西区域自动气象站实时数据质量控制系统中使用,取得很好的效果. 相似文献
240.
目前国内大多数无人机航测系统所采用的单相机平面精度可达到要求,但高程精度无法满足大比例尺测图要求。本文主要介绍一种无人机载双拼组合宽角相机低空航测系统,其组成结构、双拼组合宽角数码相机原理、数据处理软件,以及利用该系统进行大比例尺测图的生产流程。它与单相机系统的最大不同点是,通过双拼组合扩大了成像系统的旁向视场角,使得在等同航高条件下,航带影像地面覆盖宽度增加一倍,从而达到提高效率的目的。 相似文献