全文获取类型
收费全文 | 297篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 10篇 |
地球物理 | 98篇 |
地质学 | 91篇 |
海洋学 | 33篇 |
天文学 | 62篇 |
综合类 | 1篇 |
自然地理 | 24篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 13篇 |
2013年 | 20篇 |
2012年 | 9篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 16篇 |
2007年 | 16篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有321条查询结果,搜索用时 15 毫秒
211.
212.
Francesca Gherardi Laura Aquiloni Javier Diéguez-Uribeondo Elena Tricarico 《Aquatic Sciences - Research Across Boundaries》2011,73(2):185-200
Given that the impact exerted by non-indigenous crayfish species (NICS) is most often severe, can occur across many levels
of ecological organization, and results in the loss of native crayfish populations, the Convention on Biological Diversity
approach, as complemented by the European Strategy, is viewed as an excellent framework to be followed to prevent the introduction
of NICS and to alleviate or eliminate the damage they inflict. Much effort should be directed to minimize the risks of intentional
introductions, as in part done by the Council Regulation No. 708/07 in force in the European Union since 2009. However, this
and other regulations are not well harmonized, for instance, with those concerning both the aquarium trade and the harvest
of crayfish for human consumption. To make prevention more difficult, there are many records of illegal release of NICS into
the wild and of their accidental introduction as undetected contaminants in batches of regulated fish species. As a consequence,
it seems necessary that post-introduction mitigation and remediation protocols and processes, such as contingency plans, are
always in place to enable rapid detection and early response in order to minimize and, ideally, annul the threats posed by
NICS. The aim of this review paper is to offer a synthetic view of the different methods (mechanical removal, physical methods,
biological control, biocides, and autocidal methods) proposed and adopted until now to control NICS with a discussion of their
pitfalls and potentialities. A glimpse to the ongoing research in the matter will be also given. 相似文献
213.
The reliability of the first appearance datum of Globotruncana ventricosa as biozonal marker for the Campanian is discussed. The taxonomy and species concept of G. ventricosa and of Globotruncana tricarinata, that has been either regarded as junior synonym of Globotruncana linneiana or of G. ventricosa, are examined to avoid misidentifications, and one species is here formally described as new, Globotruncana neotricarinata nov. sp. The tropical and subtropical planktic foraminiferal assemblages from the Bottaccione section (Gubbio, Italy), from Deep Sea Drillig Project (DSDP) Site 146 (Caribbean Sea, central Atlantic Ocean), and from Ocean Drilling Program (ODP) Hole 1210B (Shatsky Rise, northwestern Pacific Ocean) are analyzed for the presence of biostratigraphic markers. Lowest and highest occurrence data have been checked in thin sections and washed residues in the Bottaccione section. The comparative biostratigraphic analysis of the planktic foraminiferal distribution highlights: 1) the absence of G. ventricosa at the stratigraphic level at which it is supposed to first occur in the Tethyan area, 2) the presence of transitional specimens resembling G. ventricosa and thus erroneously used to identify the base of the G. ventricosa Zone, 3) the presence of a good sequence of bioevents that appear to be promising for regional and global correlations such as the appearance of Globotruncanita atlantica, Contusotruncana plummerae and the disappearance of Hendersonites carinatus. The correlation potential of these bioevents has been verified across latitudes by studying the Campanian planktic foraminiferal assemblage in pelagic sediments drilled on coastal Tanzania (western Indian Ocean), and at the deep-sea ODP Hole 762C (Exmouth Plateau, western Indian Ocean), that were located at 30°S and 47°S in the Late Cretaceous, respectively. Besides the known diachronous first appearance of G. ventricosa in the Southern Ocean sites, results confirm the difficulty in using G. ventricosa as zonal marker in the tropical and subtropical areas, and the validity of the first appearance datum of C. plummerae for regional and global correlations. 相似文献
214.
Francesca Mietta Claire Chassagne Romaric Verney Johan C. Winterwerp 《Ocean Dynamics》2011,61(2-3):257-271
In this paper, we study a population balance equation (PBE) where flocs are distributed into classes according to their mass. Each class i contains i primary particles with mass m p and size L p. All differently sized flocs can aggregate, binary breakup into two equally sized flocs is used, and the floc??s fractal dimension is d 0?=?2, independently of their size. The collision efficiency is kept constant, and the collision frequency derived by Saffman and Turner (J Fluid Mech 1:16?C30, 1956) is used. For the breakup rate, the formulation by Winterwerp (J Hydraul Eng Res 36(3):309?C326, 1998), which accounts for the porosity of flocs, is used. We show that the mean floc size computed with the PBE varies with the shear rate as the Kolmogorov microscale, as observed both in laboratory and in situ. Moreover, the equilibrium mean floc size varies linearly with a global parameter P which is proportional to the ratio between the rates of aggregation and breakup. The ratio between the parameters of aggregation and breakup can therefore be estimated analytically from the observed equilibrium floc size. The parameter for aggregation can be calibrated from the temporal evolution of the mean floc size. We calibrate the PBE model using mixing jar flocculation experiments, see Mietta et al. (J Colloid Interface Sci 336(1):134?C141, 2009a, Ocean Dyn 59:751?C763, 2009b) for details. We show that this model can reproduce the experimental data fairly accurately. The collision efficiency ?? and the ratio between parameters for aggregation and breakup ?? and E are shown to decrease linearly with increasing absolute value of the ??-potential, both for mud and kaolinite suspensions. Suspensions at high pH and different dissolved salt type and concentration have been used. We show that the temporal evolution of the floc size distribution computed with this PBE is very similar to that computed with the PBE developed by Verney et al. (Cont Shelf Res, 2010) where classes are distributed following a geometrical series and mass conservation is statistically ensured. The same terms for aggregation and breakup are used in the two PBEs. Moreover, we argue, using both PBEs, that bimodal distributions become monomodal in a closed system with homogeneous sediment, even when a variable shear rate is applied. 相似文献
215.
Mauro Dolce Francesca Pacor Roberto Paolucci 《Bulletin of Earthquake Engineering》2011,9(6):1717-1721
The Special Issue of the Bulletin of Earthquake Engineering devoted to the new Italian strong motion database ITACA (ITalian
ACelerometric Archive) is introduced in this foreword. An overview of the papers published in this issue is presented, providing
an idea of the number of problems encountered in the compilation of a database as rich of information as ITACA, of the solutions
adopted and of the possible research and practical applications. Most of the contents, though specifically addressed to ITACA
and to its accelerograms, can be usefully thought of as an exemplification of approaches and methods that can be used for,
and extended to, similar databases in other countries. 相似文献
216.
Francesca Micheletti Annamaria Fornelli Giuseppe Piccarreta Massimo Tiepolo 《International Journal of Earth Sciences》2011,100(1):139-155
The paper deals with the U–Pb data of zircon separated from three samples representative of mylonitic leucogranites, trondhjemites
and pegmatites occurring along the Alpine tectonic zone between the Castagna and Sila Units in northern Calabria. These mylonites
are associated to Variscan granitic-granodioritic biotite-rich augen gneisses derived from Neo-Proterozoic-Early Cambrian
protoliths. Apparent ages ranging from Early Cambrian to post-Variscan have been obtained. Th, U and rare earth elements have
been determined in two zircon domains of mylonitic leucogranite and trondhjemite giving different ages in order to get information
relative to their geological significance. The pegmatite preserves intrusive contact with the augen gneisses and with the
other mylonites; it turns out to be emplaced at 290–300 Ma, like the Variscan plutonites of the Castagna Unit. The deformation
masks the original contacts of the mylonitic leucogranite and trondhjemite with the biotite-rich augen gneisses. The age-group
averaging 540 Ma is interpreted as indicative of the emplacement of the protoliths and it coincides with the age previously
determined for the emplacement of the protoliths of the biotite-rich augen gneisses. Zircon from the mylonitic pegmatite includes
domains showing concordant and discordant ages younger than 290 Ma, thus reflecting various degrees of partial resetting and
Pb-loss caused by post-Variscan events. Zircon from the mylonitic leucogranite and trondhjemite includes apparent ages between
300 and 280 Ma as well as ages younger than 250 Ma. Perturbation of U–Pb system by Alpine shearing appears evident; however,
possibile effects caused by thermal input and hydrothermal fluid infiltration from the Variscan plutonites cannot be excluded. 相似文献
217.
218.
Composition of the L5 Mars Trojans: Neighbors, not siblings 总被引:1,自引:1,他引:0
Andrew S. Rivkin David E. Trilling Cristina A. Thomas Francesca DeMeo Timothy B. Spahr Richard P. Binzel 《Icarus》2007,192(2):434-441
Mars is the only terrestrial planet known to have Trojan (co-orbiting) asteroids, with a confirmed population of at least 4 objects. The origin of these objects is not known; while several have orbits that are stable on Solar System timescales, work by Rivkin et al. [Rivkin, A.S., Binzel, R.P., Howell, E.S., Bus, S.J., Grier, J.A., 2003. Icarus 165, 349–354] showed they have compositions that suggest separate origins from one another. We have obtained infrared (0.8–2.5 μm) spectroscopy of the two largest L5 Mars Trojans, and confirm and extend the results of Rivkin et al. We suggest that the differentiated angrite meteorites are good spectral analogs for 5261 Eureka, the largest Mars Trojan. Meteorite analogs for 101429 1998 VF31 are more varied and include primitive achondrites and mesosiderites. 相似文献
219.
Nives Grasso Andrea Maria Lingua Maria Angela Musci Francesca Noardo Marco Piras 《Natural Hazards》2018,90(2):623-637
Every year, there are almost 50,000 forest fires in Europe (127/day), which have burned an area equal to more than 450,000 ha. An effective management of forest fires is therefore fundamental in order to reduce the number of the fires and, especially, the related burned areas, preserving the environment and saving human lives. However, some problems still exist in the structure of information and in the harmonization of data and fire management procedures among different European countries. Pursuing the same interoperability aims, the European Union has invested in the development of the INSPIRE Directive (Infrastructure for Spatial Information in Europe) to support environmental policies. Furthermore, the EU (European Union) is currently working on developing ad hoc infrastructures for the safe management of forests and fires. Moving from this premises and following an analysis of the state of the art of information systems for forest fire-fighting, in the light of the end-user requirements, the paper presents the INSPIRE—compliant design of a geographical information system, implemented using open-source platforms. 相似文献
220.
Gerardo Herrera Rosa María Mateos Juan Carlos García-Davalillo Gilles Grandjean Eleftheria Poyiadji Raluca Maftei Tatiana-Constantina Filipciuc Mateja Jemec Auflič Jernej Jež Laszlo Podolszki Alessandro Trigila Carla Iadanza Hugo Raetzo Arben Kociu Maria Przyłucka Marcin Kułak Michael Sheehy Xavier M. Pellicer Charise McKeown Graham Ryan Veronika Kopačková Michaela Frei Dirk Kuhn Reginald L. Hermanns Niki Koulermou Colby A. Smith Mats Engdahl Pere Buxó Marta Gonzalez Claire Dashwood Helen Reeves Francesca Cigna Pavel Liščák Peter Pauditš Vidas Mikulėnas Vedad Demir Margus Raha Lídia Quental Cvjetko Sandić Balazs Fusi Odd Are Jensen 《Landslides》2018,15(2):359-379
Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km2 landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm2 (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization. 相似文献