全文获取类型
收费全文 | 1040篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 41篇 |
大气科学 | 88篇 |
地球物理 | 221篇 |
地质学 | 347篇 |
海洋学 | 77篇 |
天文学 | 159篇 |
综合类 | 15篇 |
自然地理 | 113篇 |
出版年
2024年 | 4篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 35篇 |
2017年 | 21篇 |
2016年 | 33篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 75篇 |
2012年 | 38篇 |
2011年 | 45篇 |
2010年 | 41篇 |
2009年 | 64篇 |
2008年 | 66篇 |
2007年 | 50篇 |
2006年 | 38篇 |
2005年 | 35篇 |
2004年 | 32篇 |
2003年 | 39篇 |
2002年 | 31篇 |
2001年 | 27篇 |
2000年 | 13篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有1061条查询结果,搜索用时 31 毫秒
11.
In recent years, newspaper research has been streamlined by digitisation and online hosting by PapersPast. This paper tests the reliability and credibility of reporting of extreme weather and climatic events through PapersPast to determine if newspaper research of past climate can be further streamlined. Searches were conducted through four early‐20th‐century Auckland newspapers, where counts of articles returned by key‐word searches for particular periods were compared against periods of known extremes. We find that blind searches have only limited potential in identifying extreme weather and climatic events and that they are no substitute for thorough analyses of documentary sources. 相似文献
12.
13.
Scott Pezanowski Alan M MacEachren Alexander Savelyev Anthony C Robinson 《制图学和地理信息科学》2018,45(5):420-437
SensePlace3 (SP3) is a geovisual analytics framework and web application that supports overview + detail analysis of social media, focusing on extracting meaningful information from the Twitterverse. SP3 leverages social media related to crisis events. It differs from most existing systems by enabling an analyst to obtain place-relevant information from tweets that have implicit as well as explicit geography. Specifically, SP3 includes not just the ability to utilize the explicit geography of geolocated tweets but also analyze implicit geography by recognizing and geolocating references in both tweet text, which indicates locations tweeted about, and in Twitter profiles, which indicates locations affiliated with users. Key features of SP3 reported here include flexible search and filtering capabilities to support information foraging; an ingest, processing, and indexing pipeline that produces near real-time access for big streaming data; and a novel strategy for implementing a web-based multi-view visual interface with dynamic linking of entities across views. The SP3 system architecture was designed to support crisis management applications, but its design flexibility makes it easily adaptable to other domains. We also report on a user study that provided input to SP3 interface design and suggests next steps for effective spatiotemporal analytics using social media sources. 相似文献
14.
Maria da Glria M. Garcia Mrio C. Campos Neto Anthony E. Fallick 《Journal of South American Earth Sciences》2003,15(8):871-883
Oxygen isotope studies were carried out across units of a Neoproterozoic nappe system, south of São Francisco Craton. A temperature decrease toward the base of the system is found, consistent with a previously recognized inverted metamorphic pattern. The tectonic contact of the basal unit and the reworked southern São Francisco craton show a steep temperature gradient, suggesting that low temperature thrusting acted as the dominant tectonic process. The contrasts between the δ18O values of the Três Pontas-Varginha and Carmo da Cachoeira nappes and the differences among the samples and minerals are consistent with the preservation of sedimentary isotopic composition during metamorphism. The small differences in the δ18O values between the undeformed and the deformed calc-silicate samples (1.6‰) suggest that the δ18O value of mylonitization fluids was close to that which equilibrated with the metamorphic assemblage. The distinct δ18O values of metapelitic and calc-silicate samples and the great temperature difference from one type to the other indicate that no large-scale fluid interaction processes occurred during metamorphism. Oxygen isotopic estimations of both Três Pontas-Varginha undeformed rocks and Carmo da Cachoeira unaltered equivalents indicate δ18O values of up to 18‰. Comparison between these values and those from the ‘basement’ orthogneisses (8.3–8.5‰) indicates the latter are not sources for the metapelites. 相似文献
15.
16.
André C. Colonese Giovanni Zanchetta Elisabeth Dotsika Russell N. Drysdale Anthony E. Fallick Renata Grifoni Cremonesi Giuseppe Manganelli 《第四纪科学杂志》2010,25(8):1347-1359
This paper compares stable isotope (δ18O and δ13C) records of early–middle Holocene land snail shells from the archaeological deposits of Grotta di Latronico 3 (LTR3; southern Italy) with modern shell isotopic data. No substantial interspecific variability was observed in shell δ18O (δ18Os) of modern specimens (Pomatias elegans, Cornu aspersum, Eobania vermiculata, Helix ligata and Marmorana fuscolabiata). In contrast, interspecific shell δ13C (δ13Cs) variability was significant, probably due to different feeding behaviour among species. The δ18Os values of living land snails suggest that species hibernate for a long period during colder months, so that the signal of 18O‐depleted winter rainfall in their δ18Os is lost. This suggests that δ18Os and δ13Cs values of Pomatias elegans from this archaeological succession provide valuable clues for seasonal (spring–autumn) climatic conditions during the early–middle Holocene. The δ18Os values of fossil specimens are significantly lower than in modern shells and in agreement with other palaeoclimatic records, suggesting a substantial increase of precipitation and/or persistent changes in air mass source trajectories over this region between ca. 8.8 cal ka BP and 6.2–6.7 ka ago. The δ13Cs trend suggests a transition from a slightly 13C‐enriched to a 13C‐depleted diet between early and middle Holocene compared to present conditions. We postulate that this δ13Cs trend might reflect changes in the C3 vegetation community, potentially combined with other environmental factors such as regional moisture increase and the progressive decrease of atmospheric CO2 concentration. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
作为一种土地利用活动,传统农林复合系统已经经历了成百上千年的历史,并且依然发挥着重要的作用在世界上,特别是热带和亚热带地区。在全球变化和粮食安全等危机的时代背景下,传统农林复合系统受到越来越多政府和非政府组织的重视,因为传统农林复合系统具有重要的经济、生态和社会文化效益。这与全球重要农业文化遗产要求的特征也相一致,目前为止,已经有5个国家4个典型的传统农林复合系统被列为全球重要农业文化遗产。这些传统农林复合系统具有丰富的农业生物多样性,多重的生态系统服务功能,重要的社会文化价值,无论在区域还是全球水平上。目前传统农林复合系统面临一些威胁和挑战,如人口迁移、市场冲击、气候变化等,但是只要政府和非政府组织、社区、农民之间采取多种方式紧密合作,在未来的全球土地利用活动中,传统农林复合系统必将得到有效保护和推广。 相似文献
18.
19.
Sarah Church Peter Ade James Bock Melanie Bowden John Carlstrom Ken Ganga Walter Gear James Hinderks Wayne Hu Brian Keating John Kovac Andrew Lange Eric Leitch Olivier Mallie Simon Melhuish Anthony Murphy Ben Rusholme Creidhe OSullivan Lucio Piccirillo Clem Pryke Andy Taylor Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083
QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓmax2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005. 相似文献
20.