全文获取类型
收费全文 | 840篇 |
免费 | 39篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 69篇 |
地球物理 | 207篇 |
地质学 | 304篇 |
海洋学 | 98篇 |
天文学 | 103篇 |
综合类 | 3篇 |
自然地理 | 81篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 21篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 38篇 |
2014年 | 39篇 |
2013年 | 36篇 |
2012年 | 40篇 |
2011年 | 52篇 |
2010年 | 62篇 |
2009年 | 61篇 |
2008年 | 37篇 |
2007年 | 45篇 |
2006年 | 38篇 |
2005年 | 40篇 |
2004年 | 38篇 |
2003年 | 25篇 |
2002年 | 21篇 |
2001年 | 12篇 |
2000年 | 19篇 |
1999年 | 10篇 |
1998年 | 20篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1969年 | 2篇 |
1965年 | 2篇 |
1963年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有888条查询结果,搜索用时 15 毫秒
881.
Gasoline range hydrocarbons (C5–C12) are usually associated with petroleum generation, yet few surface geochemical surveys have attempted to evaluate the gasoline range hydrocarbons in near-surface marine sediments. This is due to the difficulty in capturing and analyzing this volatile range of hydrocarbons with minimum loss and evaporative fractionation. In this study, a Headspace Solid Phase Microextraction (HSPME) method was developed and evaluated for the purpose of capturing the gasoline range of hydrocarbons within unconsolidated sediment using a solventless protocol. 相似文献
882.
Catherine Christenson David J. Hart Michael Cardiff Susan Richmond Dante Fratta 《Ground water》2022,60(3):426-433
Communication of hydrologic data to the public can be improved by connecting data to the places they represent. In our example of data communication, we coupled hydrologic data with simultaneously collected video as both a scientific and public engagement tool. This note presents a method for collecting spatially and temporally dense datasets of water-quality and geophysical data on small streams and lakes, and for displaying the data in a user-friendly format using commercially available software. With this method, multiple instruments are mounted on a canoe and a controlled survey float is carried out to collect data. The data stream is georeferenced and logged using an Arduino microcontroller to provide detailed information about spatial variability. We employed these continuous data-collection methods at small streams and lakes across Wisconsin, USA. Comparison of stream-float sensor data to lab reported data, data collected by alternative sensors, and previously collected data in our study areas indicates that the low-cost temperature, electrical conductivity, pH, and dissolved oxygen sensors performed well. GoPro cameras recorded video throughout the duration of data collection. Our established water-quality and geophysical data collection methods are inexpensive, fast, and reliable, which qualify them as excellent tools for fine-scale spatial understanding of stream and lake habitats' health. Data-rich video connects point measurements of water properties to the appearance of the native environment. This method helps improve our understanding of groundwater and surface water interactions in complex hydrogeologic systems, enhance communication amongst stakeholders, and provide context when monitoring and managing sensitive habitats. 相似文献
883.
Guillaume Martelet Nicole Debéglia Catherine Truffert 《Comptes Rendus Geoscience》2002,334(7):449-454
For regional and national study purposes, there is a high need for updating the terrain corrections (TC) in the French gravity database. We have recomputed the TC for all the French gravity stations from 50 m out to a distance of 167 km. We compute the TC with a flat-top-prism algorithm and three DEM with grid spacing of 50, 250 and 1000 m, used in the zones 53 m/3 km, 3 km/10 km et 10 km/167 km, respectively. Analysing the DEM/station Δz and comparing our results to the ones previously obtained in the Alps area, we estimate the accuracy of our TC to be better than 1 mGal. To cite this article: G. Martelet et al., C. R. Geoscience 334 (2002) 449–454. 相似文献
884.
The First Stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic Shishugou Formation of Xinjiang, China 总被引:1,自引:0,他引:1 下载免费PDF全文
JIA Chengkai Catherine A. FOSTER XU Xing James M. CLARK 《《地质学报》英文版》2007,81(3):351-356
A new stegosaur species, Jiangjunosaurus junggarensis, gen. et sp. nov., is erected based on a specimen collected from the Upper Jurassic upper section of the Shishugou Formation in the Junggar Basin, Xinjiang, China. It represents the first stegosaur from the Jurassic of Xinjiang and increases the diversity of the dinosaur fauna in the Shishugou Formation. The new genus is characterized by symmetrical and proportionally wide tooth crowns, a sub-rectangular axial neural spine seen in lateral view, and large openings on the lateral surfaces of the cervical centra. A preliminary character analysis suggests that this new taxon is more derived than the Middle Jurassic stegosaur Huayangosaurus but more primitive than most other known stegosaur species. 相似文献
885.
Slavomír Nehyba Daniel Nývlt Uwe Schkade Gerald Kirchner Eva Franců 《Journal of Paleolimnology》2011,45(1):41-55
Facies analysis, magnetic susceptibility, and analysis of grain size, TOC content and isotopes (137Cs, 210Pb, 226Ra, 228Ra, and 238U concentrations) were used to determine the history of the modern deposits of the Brno reservoir. The sedimentary succession
can be subdivided into two main units. The lower unit is formed predominantly by medium- to coarse-grained silty sands and
is interpreted as a fluvial succession deposited before the Svratka River was dammed. The upper unit consists of brownish
planar laminated silts and rarely of clayey or sandy silts and is interpreted as a product of the reservoir deposition. The
concentrations of 238U reflect the history of uranium mining in the upper part of the Svratka River catchment. As a consequence, 210Pb radionuclide concentrations cannot be used for establishing a sediment chronology. Concentrations of 137Cs show two marked peaks, the upper of which is attributed to the Chernobyl reactor accident in 1986, and the lower one is
attributed to the maximum rate of atomic weapons testing in 1963. From these peaks, mean depositional rates of 3.2 cm year−1 for the time period of 1986–2007 and of 3.4 cm year−1 between 1963 and 1986 are calculated. Based on the known age of the reservoir, which was constructed in 1939, we can also
calculate mean depositional rate for the time period of 1939–1963, which is 3.1 cm year−1. 相似文献
886.
887.
Rodrigo Rier Juan Domingo Delgado Myriam Rodrguez scar Monterroso Eva Ramos 《海洋学报(英文版)》2012,31(1):98-105
This study contributes with the first data on physical and taxonomical structure of macrofaunal assemblages of ma¨erl beds from the Canary Islands. Ma¨erl beds and Cymodocea nodosa meadows of the Canary Islands are considered biodiversity hot-spots in terms of taxonomic and functional biodiversity with a broad geographical and depth ranges. The authors have studied the structure of the macrofaunal assemblages on different habitat types (Cymodocea, Caulerpa, sabellid field, garden eel and ma¨erl beds). Samples were taken at a range of depths between 14 and 46 m. Correlations were performed among abiotic variables (granulometry, organic matter, nitrogen and phosphates) and the most abundant taxa. Similarity analysis was performed to explore the patchiness of seabeds at a local scale. Significant differences were found in macrofaunal assemblages among seabed types, with highest abundances and lowest biodiversity in sabellid fields, where the sabellid Bispira viola dominated. The polychaetes Aponuphis bilineata and Chone filicauda and the mollusc Turritella brochii were the most abundant taxa on ma¨erl beds. The mosaic of granulometric conditions would explain the associated macroinfaunal community structure and contribute to the creation of diversity on these relatively well preserved seabeds at a local scale. 相似文献
888.
Philipp Garbe Amr Abd El-Raouf Ashraf Es-Senussi Eva Lange-Athinodorou Julia Meister 《Geoarchaeology》2024,39(1):17-34
In ancient Egypt, lakes, canals, and other water bodies were an essential part of the sacred landscape in which temples were embedded. In recent years, geoarchaeological research at the site of the Temple of Bastet at Bubastis in the southeastern Nile Delta has proven the existence of two water canals surrounding the temple. It has now been investigated whether these canals were connected to the Temple of Pepi I (2300–2250 B.C.E.), located approximately 100 m to the west of the Temple of Bastet. To explore the Holocene landscape genesis of the Temple of Pepi I, 15 drillings and six geoelectrical profile lines were performed in the surroundings of the temple in spring 2022. The results show loamy to clayey sediments in deeper sections of all drillings with a maximum thickness of 1.70 m, indicating a marshy or swampy depositional environment. Based on the recovered sediment sequences and archaeological remains in the vicinity of the Temple of Pepi I, the marshy or swampy area existed before the Fourth Dynasty. During the Old Kingdom (ca. 2850–2180 B.C.E.), the former marshland either dried up through natural processes or was intentionally drained and filled with sediments for subsequent use for occupation. Regarding the original research question, there is as yet no evidence for a direct connection to the canals of the Temple of Bastet. 相似文献