全文获取类型
收费全文 | 3541篇 |
免费 | 467篇 |
国内免费 | 770篇 |
专业分类
测绘学 | 78篇 |
大气科学 | 269篇 |
地球物理 | 523篇 |
地质学 | 2252篇 |
海洋学 | 664篇 |
天文学 | 20篇 |
综合类 | 233篇 |
自然地理 | 739篇 |
出版年
2024年 | 18篇 |
2023年 | 71篇 |
2022年 | 93篇 |
2021年 | 109篇 |
2020年 | 119篇 |
2019年 | 155篇 |
2018年 | 164篇 |
2017年 | 177篇 |
2016年 | 207篇 |
2015年 | 142篇 |
2014年 | 194篇 |
2013年 | 487篇 |
2012年 | 198篇 |
2011年 | 195篇 |
2010年 | 197篇 |
2009年 | 222篇 |
2008年 | 208篇 |
2007年 | 220篇 |
2006年 | 215篇 |
2005年 | 188篇 |
2004年 | 153篇 |
2003年 | 116篇 |
2002年 | 130篇 |
2001年 | 101篇 |
2000年 | 105篇 |
1999年 | 81篇 |
1998年 | 72篇 |
1997年 | 48篇 |
1996年 | 49篇 |
1995年 | 60篇 |
1994年 | 55篇 |
1993年 | 37篇 |
1992年 | 28篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有4778条查询结果,搜索用时 37 毫秒
191.
Determining the main controlling factors of earthquake-triggered geohazards is a prerequisite for studying earthquake geohazards and post-disaster emergency response. By studying these factors, the geomorphic and geological factors controlling the nature, condition, and distribution of earthquake-induced geohazards can be analyzed. Such insights facilitate earthquake disaster prediction and emergency response planning.The authors combined field investigations and spatial data analysis to examine... 相似文献
192.
青岛市崂山区地质灾害气象预报预警 总被引:9,自引:0,他引:9
本文基于地质灾害递进分析理论与方法,进行了崂山区地质灾害气象预报预警探讨。崂山区地质灾害及隐患点发育的类型主要是滑坡、崩塌和泥石流。据调查,区内地质灾害及隐患点83处,其中已发生灾害17处,新的灾害隐患66处。崂山区地质灾害基础因子主要是地形坡度、地质构造、地面高程、岩体、植被、水系和坡形,诱发因:于主要是大气降水、人类工程活动和地震。大气降水是变化频繁的敏感因子。通过分析崂山区日降水量、持续累计降水量与地质环境条件、地质灾害发生频率、发生时间的关系,结合国内其他地区的分析结论,初步选定崂山区地质灾害预报预警降水量临界值,在此基础上建立了崂山区地质灾害预报预警信息系统,并以图形和表格两种形式在网上对外发布成功。通过回访调查,预报基本准确,服务效果明显,在很大程度上减轻和避免了灾害损失,有效地保护了人民生命财产的安全,促进了经济、社会的持续、稳定、健康发展。 相似文献
193.
A global positioning system and ground penetrating radar surveys is used to produce digital elevation models of the surface and bed of Brewster Glacier. These are used to derive maps of subglacial hydraulic potential and drainage system structure using three different assumptions about the subglacial water pressure (Pw): (i) Pw = ice overburden; (ii) Pw = half ice overburden; (iii) Pw = atmospheric. Additionally, 16 dye‐tracing experiments at 12 locations were performed through a summer melt season. Dye return curve shape, together with calculations of transit velocity, dispersivity and storage, are used to infer the likely morphology of the subglacial drainage system. Taken together, the data indicate that the glacier is underlain by a channelised but hydraulically inefficient drainage system in the early summer in which water pressures are close to ice overburden. By mid‐summer, water pressures are closer to half‐ice overburden and the channelised drainage system is more hydraulically efficient. Surface streams that enter the glacier close to the location of major subglacial drainage pathways are routed quickly to the channels and then to the glacier snout. Streams that enter the glacier further away from the drainage pathways are routed slowly to the channels and then to the snout because they first flow through a distributed drainage system. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
194.
随着城市化进程的加速,济南城市轨道交通近年来发展迅速,地铁成为济南未来交通主要建设方向之一。作为泉城,岩溶是济南泉水补给、径流的重要通道,在济南地区普遍发育,但同时岩溶问题也是地铁施工的难点,因此,查明地铁线路下岩溶的发育程度至关重要。与南方岩溶的“大尺寸”相比,济南地区的岩溶尺寸要小得多,且多成蜂窝状、裂隙状,在空间上也无明显规律可循,这对物探工作的分辨率就提出了较高的要求。该次研究区域是地铁2号线任家庄站到腊山站沿刘长山路区间段。经初步探查,该区间段存在多处岩溶且线路地处闹区,车流量大,管线复杂。为了研究该区岩溶发育情况,该次采用电磁波CT技术对区内岩溶进行了探测,通过对区域内地质介质电磁波吸收系数差异的研究,结合钻探资料进行对比,推断出岩溶区吸收系数的取值区间;最后对推断的岩溶区进行钻探取样,验证了物探与钻探的吻合程度。该方法在岩溶勘察中取得了良好的效果,为济南地铁设计及施工提供可靠的依据。 相似文献
195.
196.
197.
Preliminary study on PAH degradation by bacteria from contaminated sediments in Xiamen Western Sea,Fujian, China 总被引:1,自引:0,他引:1
In order to estimate the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) compounds, bacterial strains were isolated from marine sediments in three heavily contaminated sites (Yuandang Lake, Dongdu Port and Aquacultural zones in Maluan Bay) in Xiamen Western Sea. The results show three bacterial strains, which used pyrene as the sole carbon source, were identified as strains of Aureobacterium sp.,Arthrobacter sp., Rhodococcus sp. The PAH-degrading bacteria isolated had a strong ability to degrade phenanhrene, fluoranthene and pyrene at different degradation rates. The highest degradation rate was observed when three PAH compounds were mixed with an individual strain in the medium. The three PAHs were degraded after one week with a degradation rate of 89.94 % for phenanthrene and 93.4 % for both of fluoranthene and pyrene.In addition, after 25 days of incubation, the degradation rate was 99.98 % for phenanthrene and 99.97 % for both of fluoranthene and pyrene. Optical density was measured to estimate bacterial growth during the degradation of PAHs. Highest levels of bacterial growth were observed with a three PAH mixture in the culture, suggesting that the concentration of PAHs influenced bacterial growth and the highest levels of degradation for most series were detected after one week of incubation. 相似文献
198.
FANG Mingqiang Ocean Remote Sensing Institute Ocean University of China Qingdao P.R.China 《中国海洋大学学报(英文版)》2005,4(2)
By using monthly historical sea surface temperature (SST) data for the years from 1950 to 2000, the Western Pacific Warm Pool (WPWP) climatology and anomalies are studied in this paper. The analysis of WPWP centroid (WPWPC) movement anomalies and the Nino-3 region SST anomalies( SSTA) seems to reveal a close, linear relation between the zonal WPWPC and Nino-3 region SSTA, which suggests that a 9' anomaly of the zonal displacement from the climatological position of the WPWPC corresponds to about a 1 ℃ anomaly in the Nino-3 region area-mean SST. This study connects the WPWPC zonal displacement with the Nino-3 SSTA, and it may be helpful in better understanding the fact that the WPWP eastward extension is conducive to the Nino-3 region SST increase during an El Nino-Southern Oscillation (ENSO) event. 相似文献
199.
200.
Decades of commercial planting and other anthropogenic processes are posing a threat to the riparian landscapes of the Cauvery river basin, which supports a high floral diversity. Despite this, the habitats in the upstream sections of the River Cauvery are still intact, as they are located in sacred groves. To understand the dynamism of riparian forests exposed to anthropogenic pressures, the upstream stretch of Cauvery extending from Kushalanagara to Talacauvery (~102 km) was categorized into two landscapes: agro ecosystem and sacred (i.e. preserved). The tree species were sampled using belt transects at 5 km intervals and the regeneration status of endemic species assessed using quadrats. A total of 128 species belonging to 47 families, and representing 1,590 individuals, was observed. Amongst them, 65% of unique species were exclusive to sacred landscapes. A rarefaction plot confirmed higher species richness for the sacred compared to the agro ecosystem landscapes, and diversity indices with more evenness in distribution were evident in sacred landscapes. A significant loss of endemic tree species in the agro ecosystem landscapes was found. Overall, this study demonstrates that an intense biotic pressure in terms of plantations and other anthropogenic activities have altered the species composition of the riparian zone in non-sacred areas. A permanent policy implication is required for the conservation of riparian buffers to avoid further ecosystem degradation and loss of biodiversity. 相似文献