全文获取类型
收费全文 | 1943篇 |
免费 | 99篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 144篇 |
地球物理 | 613篇 |
地质学 | 693篇 |
海洋学 | 140篇 |
天文学 | 288篇 |
综合类 | 17篇 |
自然地理 | 121篇 |
出版年
2024年 | 7篇 |
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 41篇 |
2020年 | 48篇 |
2019年 | 26篇 |
2018年 | 89篇 |
2017年 | 78篇 |
2016年 | 157篇 |
2015年 | 105篇 |
2014年 | 122篇 |
2013年 | 125篇 |
2012年 | 81篇 |
2011年 | 120篇 |
2010年 | 94篇 |
2009年 | 116篇 |
2008年 | 100篇 |
2007年 | 49篇 |
2006年 | 67篇 |
2005年 | 45篇 |
2004年 | 49篇 |
2003年 | 48篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 32篇 |
1999年 | 31篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1979年 | 4篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1952年 | 5篇 |
1951年 | 4篇 |
1950年 | 4篇 |
1948年 | 8篇 |
1939年 | 6篇 |
排序方式: 共有2052条查询结果,搜索用时 15 毫秒
961.
Implementation of the European water framework directive from the Basque country (northern Spain): a methodological approach 总被引:3,自引:0,他引:3
Borja A Franco J Valencia V Bald J Muxika I Belzunce MJ Solaun O 《Marine pollution bulletin》2004,48(3-4):209-218
The European Water Framework Directive provides a challenge in the development of new and accurate methodologies. It addresses assessment of Ecological Quality Status within European rivers, lakes, groundwaters, estuaries and coasts. Although this directive is simple and flexible in its concept, it is necessary to develop an approach based upon scientific knowledge; however, at the same time it should be as simple as possible, in order to achieve both requirements and comparability of results throughout European waters. This contribution presents the first methodological approach to the problem, as used for estuaries and coasts of the Basque Country (northern Spain), in: selecting typologies and reference conditions; determining biological quality and ecological status; and identifying some problems in implementing the WFD. As such, the present paper could serve as the basis for a discussion document for other regions and countries, throughout Europe. 相似文献
962.
Mario A. Salgado-Gálvez Daniela Zuloaga Sebastian Henao Gabriel A. Bernal Omar-Darío Cardona 《Natural Hazards》2018,93(1):5-24
A methodology for the development of fully probabilistic seismic risk assessments on water and sewage networks is presented in this paper together with a case study for the system of Manizales, Colombia. These kinds of assessments require the development of probabilistic seismic hazard analysis, the consideration of local site effects, when relevant, the assembly of databases to identify and characterize the exposed elements and the development and assignment of vulnerability models for each type of component. For the case of Manizales, a high-resolution exposure database has been developed (element by element, segment by segment) based on the information and data provided by the owner and operator of the network, Aguas de Manizales. Losses due to earthquakes are obtained after convoluting the hazard and vulnerability inputs in a fully probabilistic manner, using the state-of-the-art methodologies incorporated in the CAPRA risk assessment module. Several risk metrics such as the loss exceedance curve, the loss exceedance probabilities for different time frames and the average annual loss are obtained for the system as a whole as well as disaggregated by component. In addition, repair rates for the pipelines were also calculated. The risk results obtained in this study have been useful for the company in designing and implementing expansion and maintenance plans that explicitly account for seismic risk mitigation issues, as well as to explore and negotiate financial protection alternatives by means of risk transfer and retention schemes, thus becoming a valuable input in the continuous development of good disaster risk management practices in this city. 相似文献
963.
964.
Mario Bossolasco 《Pure and Applied Geophysics》1943,5(1-2):11-36
Riassunto Si riferisce sul rilevamento geomagnetico dell'isola di Stromboli, eseguito nel 1940 (marzo-maggio) con 218 stazioni, nelle quali vennero determinate, mediante misure relative, le componenti verticale ed orizzontale del campo terrestre. I risultati ottenuti per la distribuzione di questi elementi (e di quelli subordinatiI edF) sono stati rappresentati graficamente nelle cartine allegate; essi rivelano l'esistenza di anomalie particolarmente intense, talune con valori di Z e di H maggiori di 5000 , le cui caratteristiche vengono discusse in funzione delle condizioni geologiche locali e cioè sopratutto dell'attività relativamente recente del vulcano.
con quattro tavole f.t. 相似文献
Zusammenfassung Die Arbeit bezieht sich auf die geomagnetische Aufnahme, welche im Jahre 1940 (März–Mai) auf der Insel Stromboli mit 218 Stationen durchgeführt wurde. Damit wurden mittels relativen Messungen die vertikale und horizontale Komponenten des Erdfeldes bestimmt. Die für die Verteilung dieser Elemente (und der abzuleitenden GrössenI undF) erreichten Ergebnisse sind in untenstehenden Karten dargestellt. Es zeigt sich u.a das Vorhandensein von äusserst starken Anomalien, die z.B. Z- und H-Werte über 5000 zeigen, deren Eigentümlichkeiten in Funktion der geologischen örtlichen Bedingungen, d.h. in erster Linie der vergangenen und relativ rezenten Tätigkeit des Vulkans, besprochen werden.
con quattro tavole f.t. 相似文献
965.
Several parameters have been proposed in the literature for the evaluation of seismic damage. However, in most cases the correlation between results obtained using these parameters and observed damage in structures has not been satisfactory. A parameter for measuring seismic damage previously proposed by the first author is used in this study to analyse a set of 15 accelerograms recorded in 11 earthquakes experienced in different countries. Results using this parameter are compared to global building damage observed during these earthquakes. The use of the parameter proposed here yields results which are consistent with building damage observed in the earthquakes studied. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
966.
967.
M. Sánchez Goñi I. Cacho J. Turon J. Guiot F. Sierro J. Peypouquet J. Grimalt N. Shackleton 《Climate Dynamics》2002,19(1):95-105
Land-sea climatic proxies have been obtained from the Last Glacial section of IMAGES core MD95-2043 (western Mediterranean Sea). Vegetation and alkenone derived SST curves indicate rapid (~150 years) and synchronous terrestrial and marine climatic changes, paralleling the Dansgaard-Oeschger (D-O) climatic variability over Greenland. This frequency of climate change can be related to shifts between the two modes of operation of the North Atlantic Oscillation (NAO). Transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during Heinrich events (HEs) in comparison with other D-O stadials. The development and persistence of both Scandinavian and Atlantic Mobile Polar Highs over southwestern Europe may explain the extreme cooling (~10 °C) and dryness (400 mm) during Heinrich events 5 and 4 in the Mediterranean region. Comparison of the results of core MD95-2043 with similar climatic data from IMAGES core MD95-2042, located off Portugal, indicates that thermal and precipitation gradients occurred between the Mediterranean and the Atlantic sides of Iberia within HEs. HEs 4 and 5 are associated with more humid conditions in the Atlantic (by 200 mm) than in the Mediterranean site, as is the case at the present time. This comparison also illustrates the different behaviour of these areas during the D-O stadials. In contrast with the Mediterranean site, the Atlantic site shows similar precipitation and temperature drops for all the D-O stadials, including those related to the HEs. Here we propose the operation of different Mobile Polar Highs (MPH) as the driving mechanism for this difference in behaviour between the Atlantic and Mediterranean sides of Iberia. HEs are related to a stronger influence of the Scandinavian MPH, forcing a severe aridification and cooling of the full Iberian Peninsula. The Atlantic MPH may have been dominant during the other stadials, which would preferentially affect Southwestern Iberia. 相似文献
968.
To quantify the interplay between scalar sources and sinks (Sc) and net ecosystem exchange (NEE), “forward” and “inverse” approaches have been proposed. The canonical form of forward approaches is a one-dimensional ecophysiological-radiative transfer scheme coupled to turbulent transport theory. In contrast, inverse approaches strictly rely on turbulent transport theory and mean scalar concentration as their primary input to infer Sc and NEE. While the formulation of both approaches have evolved over the past decade, no systematic comparison between them was undertaken for the same data set, and over a wide range of atmospheric conditions. Our objective is to compare the predicted Sc and NEE from these two approaches with eddy-covariance measurements. The results show that the forward method outperformed all three inverse methods for unstable and neutral conditions on short time scales (30 min) but yielded comparable results at longer time scales. Poor agreement was obtained under stable conditions for all models. Hence, for modeling event-based flux variations, forward models are preferred. Since the forward method requires detailed knowledge of ecophysiological, drag, radiative transfer and other canopy attributes, all of which are difficult to obtain on a routine basis, a symbiotic use of forward and inverse approaches is most advantageous. 相似文献
969.
Guillermo Booth-Rea José Miguel Azañón Vı́ctor Garcı́a-Dueñas Romain Augier 《Comptes Rendus Geoscience》2003,335(9):751-761
The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the Palomares area have permitted us to define the geometry and location of sedimentary depocentres related with the PFZ. These data show an eastward displacement between the Upper Tortonian to Messinian and the Pliocene–Quaternary sedimentary depocentres, towards the presently active Arteal fault, which bounds the western mountain front of Sierra Almagrera, showing that deformation along this fault zone has migrated towards the east, from the Palomares segment, with its main activity during the Upper Tortonian and Messinian, towards the Arteal fault, active during the Pliocene and Quaternary. To cite this article: G. Booth-Rea et al., C. R. Geoscience 335 (2003). 相似文献
970.
Alberto Carramiñana 《Astrophysics and Space Science》2007,309(1-4):527-530
The understanding of the high energy γ-ray sky requires a coordinated multi-wavelength strategy. The Large Millimeter Telescope will be the largest and most sensitive
single dish antenna operating between 0.8 mm and 3 mm in the foreseeable future. Its first light instrumentation and capabilities
are well suited for studies of dust, dense molecular gas and the synchrotron emission from relativistic electrons. The Large
Millimeter Telescope, due to enter commissioning and first light science phase in 2007, will be able to complement GLAST observations and help disentangling the nature of the new and old unidentified gamma-ray sources.
Work sponsored by CONACyT grant SEP-2003-C02-42611. 相似文献