全文获取类型
收费全文 | 118篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 6篇 |
地球物理 | 36篇 |
地质学 | 30篇 |
海洋学 | 16篇 |
天文学 | 18篇 |
自然地理 | 11篇 |
出版年
2020年 | 4篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有122条查询结果,搜索用时 109 毫秒
1.
Based on univariate correlation and coherence analyses and considering the physical basis of the relationships, a simple multiforced (multiple) statistical concept is used which correlates observational climatic time series simultaneously with volcanic, solar, ENSO, and the anthropogenic greenhouse gases forcing. This is appropriate to remove some natural climate noise in the observed data and to evaluate the components (signals) possibly due to the anthropogenic greenhouse gas forcing (CO2, or equivalent CO2 implying additional gases) during industrial time. In this paper, we apply this technique to 100 global box data time series 1890–1985, of the surface air temperature, using observed data from Hansen and Lebedeff. The results are presented in terms of latitudinal-seasonal and regional trends, where the observed trend patterns are compared with the hypothetical signals (statistical assessments) possibly due to anthropogenic greenhouse forcing. These latter signals can be amplified to enable a comparison with corresponding results from general circulation model (GCM) CO2 doubling experiments. These observed-statistical assessments lead to results which are, at least qualitatively and in respect to the zonal mean temperatures, very similar to some GCM experiments indicating the maximum CO2 doubling signals (statistical assessment > 12 K) in the arctic winter. However, these signals are moderate in the tropics and in the Southern Hemisphere (global average 2.8–4.4 K). As far as the industrial signals are concerned (observed period) these signals are somewhat larger (maximum 7 K, global average 0.5–0.9 K) than the observed trends (maximum 5 K, global average 0.5 K). Phase shifts of cause and effect may amplify these signals but are very uncertain.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute for Meteorology. Guest Editor for these papers is Dr. L. Dümenil 相似文献
2.
Joana F.M.F. Cardoso Denis Langlet Jos F. Loff Ana R. Martins Johannes IJ. Witte Paulo T. Santos Henk W. van der Veer 《Journal of Sea Research》2007,57(4):303-315
The Pacific oyster Crassostrea gigas was introduced in Europe for commercial purposes in the mid 1960s. It was initially thought that low winter temperatures would restrain this species' reproduction and settlement; however, its present distribution in areas where no introduction has taken place suggests that natural invasion and expansion has occurred. Along the European coast, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Whether C. gigas will continue to further expand through northern waters will depend on its physiological performance. In this study, the performance of wild oyster populations has been studied in terms of growth and reproduction at three stations: La Rochelle (France; 46°N), Yerseke (Oosterschelde estuary, The Netherlands, 51°N), and Texel (Wadden Sea estuary, The Netherlands, 53°N). The French population had the lowest somatic-shell mass ratio and an increase in maximum shell length, somatic and gonadal mass was observed from France to the Netherlands. In addition, mean oocyte diameter decreased significantly from south to north. The combination of increasing gonadal mass and decreasing oocyte volume suggests an increasing reproductive output in terms of egg numbers from France to The Netherlands. Differences in temperature between locations will at least be partly responsible for the observed patterns; however, other environmental factors (such as food availability, predation pressure, sediment type and/or seston concentration) cannot be excluded. Since smaller eggs (oocytes) are thought to have a longer development time, the environmental conditions along the Dutch coast may result in increased larval dispersal and possibly in further population expansion. 相似文献
3.
Joana F.M.F. Cardoso Johannes IJ. Witte Henk W. van der Veer 《Journal of Sea Research》2007,57(4):316-324
The bivalve Spisula subtruncata is usually abundant in shallow coastal waters along the Dutch coast. However, its biomass has been decreasing since 1995. In order to assess whether reproductive failure may be the cause of the observed decline over the last decades, the energy investment in reproduction of a population of S. subtruncata from central Dutch coastal waters was studied. The population studied consisted of individuals of up to four years old. Shell length reached maximum values of around 32 mm and individual total body, somatic and gonadal ash-free dry mass reached maximum values of about 278 mg AFDM, 252 mg AFDM and 76 mg AFDM, respectively. A clear seasonal cycle in somatic and gonadal mass was observed. Somatic and gonadal mass indices increased in early spring and reached maximum values during summer, followed by a decrease to minimum values at the beginning of the following year. Spawning was in June–July and settlement of spat seems to have occurred in July–August. Mean oocyte diameter was 57.43 ± 0.03 μm, corresponding to a volume of 98972 μm3. These results suggested that reproductive failure was not the cause of the current population decline. Most likely, unsuccessful settlement of spat and/or severe predation during the first months of life were responsible for the observed patterns. 相似文献
4.
Graham Ryder Douglas B. Stoeser Ursula B. Marvin Janice F. Bower John A. Wood 《Earth, Moon, and Planets》1975,14(3-4):327-357
Boulder 1, Station 2, Apollo 17 is a stratified boulder containing dark clasts and dark-rimmed light clasts set in a light-gray friable matrix. The gray to black clasts (GCBx and BCBx) are multigenerational, competent, high-grade metamorphic, and partially melted breccias. They contain a diverse suite of lithic clasts which are mainly ANT varieties, but include granites, basaltic-textured olivine basalts, troctolitic and spinel troctolitic basalts, and unusual lithologies such as KREEP norite, ilmenite (KREEP) microgabbro, and the Civet Cat norite, which is believed to be a plutonic differentiate. The GCBxs and BCBxs are variable in composition, averaging a moderately KREEPy olivine norite. The matrix consists of mineral fragments derived from the observed lithologies plus variable amounts of a component, unobserved as a clast-type, that approximates a KREEP basalt in composition, as well as mineral fragments of unknown derivation. The high-temperature GCBxs cooled substantially before their incorporation into the friable matrix of Boulder 1. The light friable matrix (LFBx) is texturally distinct from the competent breccia clasts and, apart from the abundant ANT clasts, contains clasts of a KREEPy basalt that is not observed in the competent breccias. The LFBx lacks such lithologies as the granites and the Civet Cat norite observed in the competent breccias and in detail is a distinct chemical as well as textural entity. We interpret the LFBx matrix as Serenitatis ejecta deposited in the South Massif, and the GCBx clasts as remnants of an ejecta blanket produced by an earlier impact. The source terrain for the Serenitatis impact consisted of the competent breccias, crustal ANT lithologies, and the KREEPy basalts, attesting to substantial lunar activity prior to the impact. The age of the older breccias suggests that the Serenitatis event is younger than 4.01±0.03 b.y. 相似文献
5.
YU Jie Ursula Pietrzak Jim Peterson 《地球空间信息科学学报》2005,8(4):257-261
In that orcharding in early-to-mid twentieth century southeastern Australia involved use of certain heavy metal and As compounds in regular pest-control spray procedures, some interest attaches to the possibility that these landparcels are underlain by soils with above-background Cu, Pb and As levels. Interpreta- tion of Land-cover changes allowed land parcels previously occupied by orchards to be identified in the 1950s through time-series air-photos. A comparison of soil analysis results referring to soil samples from control sites, and from land parcels formerly occupied by orchardists, shows that contamination (above-background) levels of cations in the pesticides can be found in the top 6 cm of former orchard soils. It is clear that digital spatial data handling and culturally-informed air photo interpretation has a place in soil contamination studies, land-use planning (with particular reference to re-development) and in administration of public health. 相似文献
6.
7.
8.
Ursula Werner Anna Blazejak Paul Bird Gabriele Eickert Raphaela Schoon Raeid M.M. Abed Andrew Bissett Dirk de Beer 《Estuarine, Coastal and Shelf Science》2008,76(4):876-888
We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O2 m−2 h−1 and was strongly correlated with Chl a content, which lay between 31 and 84 mg m−2. An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca2+ m−2 h−1). The sediments of at least three stations were net calcifying. Sedimentary N2-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N2 m−2 h−1 and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N2-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling. 相似文献
9.
Joana F.M.F. Cardoso Johannes IJ. Witte Henk W. van der Veer 《Estuarine, Coastal and Shelf Science》2009
Cerastoderma edule and Mya arenaria are two common bivalve species in European waters. Longevity and maximum size are much greater in the latter species. Because comparison of species life-history strategies states that a long life span (i.e. high annual survival) generally goes with lower fecundity, we hypothesise that reproductive output would be lower in M. arenaria than in C. edule. In the present paper, we studied the reproductive strategies of these two species in an intertidal and a subtidal area of the western Dutch Wadden Sea, by following seasonal changes in absolute and relative weights of somatic and gonadal tissues in these bivalves. Starting of spawning was similar in the two species, around May, except for intertidal M. arenaria, which initiated spawning in August. Individual energy investment in reproduction was similar for the two species but, unlike M. arenaria, C. edule spawned completely, releasing all energy of gonadal mass in the form of gametes. Mya arenaria used the gonad not only for reproduction but also for storage. In the intertidal area, we found a trade-off between longevity and reproduction, i.e. maximum reproductive output (expressed as a proportion of body mass) was higher in C. edule than in M. arenaria. However, since body size is larger and life span longer in M. arenaria than in C. edule, mean lifetime reproductive output per individual must be higher in the first than in the latter. Based on the differences in reproductive strategies of these two species, we hypothesise that the negative effects of warming climate on bivalve population dynamics in the Wadden Sea will be stronger in C. edule than in M. arenaria. 相似文献
10.