全文获取类型
收费全文 | 294篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 37篇 |
地球物理 | 46篇 |
地质学 | 143篇 |
海洋学 | 34篇 |
天文学 | 4篇 |
自然地理 | 48篇 |
出版年
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 15篇 |
2013年 | 23篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 24篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
1950年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 15 毫秒
111.
A new radiospectrograph at Culgoora 总被引:1,自引:0,他引:1
N. P. Prestage R. G. Luckhurst B. R. Paterson C. S. Bevins C. G. Yuile 《Solar physics》1994,150(1-2):393-396
IPS Radio and Space Services (IPS) commissioned a new radiospectrograph for solar observations in May 1992. The instrument
operates over a frequency range from 18 MHz to 1.8 GHz and samples every three seconds. Digital data acquisition permits a
variety of analysis procedures that were not previously possible. The operation of the new instrument is briefly described
and some example radiospectrograms are presented. 相似文献
112.
113.
Alexander?W.?MiddletonEmail author I.?Tongu??Uysal Suzanne?D.?Golding Hans-Jürgen?F?rster Charlotte?M.?Allen Yeuxing?Feng Dieter?Rhede Vicki?J.?Marshall Jaco?van?Zyl 《Contributions to Mineralogy and Petrology》2014,168(3):1058
The Warburton Basin of central Australia has experienced a complex tectonic and fluid-flow history, resulting in the formation of various authigenic minerals. Geochemical and geochronological analyses were undertaken on vein carbonates from core samples of clastic sediments. Results were then integrated with zircon U–Pb dating and uraninite U–Th–total Pb dating from the underlying granite. Stable and radiogenic isotopes (δ18O, Sr and εNd), as well as trace element data of carbonate veins indicate that >200 °C basinal fluids of evolved meteoric origin circulated through the Warburton Basin. Almost coincidental ages of these carbonates (Sm–Nd; 432 ± 12 Ma) with primary zircon (421 ± 3.8 Ma) and uraninite (407 ± 16 Ma) ages from the granitic intrusion point towards a substantial period of active tectonism and an elevated thermal regime during the mid Silurian. We hypothesise that such a thermal regime may have resulted from extensional tectonism and concomitant magmatic activity following regional orogenesis. This study shows that the combined application of geochemical and geochronological analyses of both primary and secondary species may constrain the timing of tectonomagmatic events and associated fluid flow in intraplate sedimentary basins. Furthermore, this work suggests that the Sm–Nd-isotopic system is surprisingly robust and can record geologically meaningful age data from hydrothermal mineral species. 相似文献
114.
Wiltse Brendan Mushet Graham R. Paterson Andrew M. Cumming Brian F. 《Journal of Paleolimnology》2022,67(3):273-287
Journal of Paleolimnology - Increased relative abundances and accumulation rates of the small, centric diatom Discostella have been recorded in numerous paleolimnological investigations of north... 相似文献
115.
116.
Matthew Cole BISHOP Frederic MOYNIER Charlotte WEINSTEIN Jean‐Gabriel FRABOULET Kun WANG Julien FORIEL 《Meteoritics & planetary science》2012,47(2):268-276
Abstract– High‐precision Cu isotopic compositions have been measured for the metal phase of 29 iron meteorites from various groups and for four terrestrial standards. The data are reported as the δ65Cu permil deviation of the 65Cu/63Cu ratio relative to the NIST SRM 976 standard. Terrestrial mantle rocks have a very narrow range of variations and scatter around zero. In contrast, iron meteorites show δ65Cu approximately 2.3‰ variations. Different groups of iron meteorites have distinct δ65Cu values. Nonmagmatic IAB‐IIICD iron meteorites have similar δ65Cu (0.03 ± 0.08 and 0.12 ± 0.10, respectively), close to terrestrial values (approximately 0). The other group of nonmagmatic irons, IIE, is isotopically distinct (?0.69 ± 0.15). IVB is the iron meteorite group with the strongest elemental depletion in Cu and samples in this group are enriched in the lighter isotope (δ65Cu down to ?2.26‰). Evaporation should have produced an enrichment in 65Cu over 63Cu (δ65Cu >0) and can therefore be ruled out as a mechanism for volatile loss in IVB meteorites. In silicate‐bearing iron meteorites, Δ17O correlates with δ65Cu. This correlation between nonmass‐dependent and mass‐dependent parameters suggests that the Cu isotopic composition of iron meteorites has not been modified by planetary differentiation to a large extent. Therefore, Cu isotopic ratios can be used to confirm genetic links. Cu isotopes thus confirm genetic relationships between groups of iron meteorites (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites). Several genetic connections between iron meteorites groups are confirmed by Cu isotopes, (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites). 相似文献
117.
Bruno Malaizé Elsa Jullien Amandine Tisserand Charlotte Skonieczny E. Francis Grousset Frédérique Eynaud Catherine Kissel Jérôme Bonnin Svenja Karstens Philippe Martinez Aloys Bory Vivianne Bout-Roumazeilles Thibaut Caley Xavier Crosta Karine Charlier Linda Rossignol José-Abel Flores Ralph Schneider 《Quaternary Research》2012,77(1):182-191
A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~ 1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0–0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ18O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass δ13C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ13C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ13C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ18O and δ13C values of deep waters. 相似文献
118.
Adam Jeziorski Andrew M. Paterson Norman D. Yan John P. Smol 《Journal of Paleolimnology》2008,39(3):421-425
Despite reductions in atmospheric sulphur emissions and the resulting decline in acidic deposition, many lakes on the Canadian
Shield that have experienced acidification are either recovering at a rate slower than expected or not recovering at all.
This lack of recovery is believed to be partly the consequence of the depletion of exchangeable base cations (principally
calcium, Ca) from watershed soils. Although the implications of reduced Ca availability for biological communities remain
poorly understood, the effects on crustacean zooplankton populations may be severe, as Ca is the primary structural component
of the crustacean zooplankton exoskeleton. Because the daphniid resting egg is protected by a modified portion of the exoskeleton
(ephippia) and because these ephippia are well preserved in lake sediments, we investigated whether inter-specific differences
in Ca content are recoverable from Daphnia ephippia. However, using two methods, we did not find a recoverable Ca signal in the ephippia, indicating that future efforts
should be focused upon sedimentary taxonomic assemblage differences, not differences in ephippial Ca levels. 相似文献
119.
B. D. Paterson P. T. Spanoghe G. W. Davidson W. Hosking S. Nottingham J. Jussila 《新西兰海洋与淡水研究杂志》2013,47(5):1129-1143
Instances of morbidity amongst rock lobsters (Panulirus cygnus) arriving at factories in Western Australia (WA) have been attributed to stress during post‐harvest handling. This study used discriminant analysis to determine whether physiological correlates of stress following a period of simulated post‐harvest handling had any validity as predictors of future rejection or morbidity of western rock lobsters. Groups of 230 western rock lobsters were stored for 6 h in five environments (submerged/flowing sea water, submerged/recirculating sea water, humid air, flowing seawater spray, and recirculated seawater spray). The experiment was conducted in late spring (ambient sea water 22°C), and repeated again in early autumn (ambient sea water 26°C). After 6 h treatment, each lobster was graded for acceptability for live export, numbered, and its haemolymph was sampled. The samples were analysed for a number of physiological and health status parameters. The lobsters were then stored for a week in tanks in the live lobster factory to record mortality. The mortality of lobsters in the factory was associated with earlier deviations in haemolymph parameters as they emerged from the storage treatments. Discriminant analysis (DA) of the haemolymph assays enabled the fate of 80–90% of the lobsters to be correctly categorised within each experiment. However, functions derived from one experiment were less accurate at predicting mortality when applied to the other experiments. One of the reasons for this was the higher mortality and the more severe patho‐physiological changes observed in lobsters stored in humid air or sprays at the higher temperature. The analysis identified lactate accumulation during emersion and associated physiological and haemocyte‐related effects as a major correlate of mortality. Reducing these deviations, for example by submerged transport, is expected to ensure high levels of survival. None of the indicators tested predicted mortality with total accuracy. The simplest and most accurate means of comparing emersed treatments was to count the mortality afterwards. 相似文献
120.
Physical behaviour of Cretaceous calcareous nannofossil ooze: Insight from flume studies of disaggregated chalk 下载免费PDF全文
Toms Buls Kresten Anderskouv Patrick L. Friend Charlotte E. L. Thompson Lars Stemmerik 《Sedimentology》2017,64(2):478-507
Geomorphic features such as drifts, sediment waves and channels have been documented in the Upper Cretaceous of north‐west Europe. These features are interpreted to result from bottom currents and have been used to refine chalk depositional models and quantify palaeocirculation patterns. Chalk was first deposited as calcareous nannofossil ooze and geomorphic features are the result of sediment reworking after deposition. There is limited knowledge on the processes that govern nannofossil ooze mobility, thus forcing uncertainty onto numerical models based on sedimentological observations. This article provides an extensive view of the erosional and depositional behaviour of calcareous nannofossil ooze based on experimental work using annular flumes. A fundamental observation of this study is the significant decrease of nannofossil ooze mobility with decreasing bed porosity. Erosion characteristics, labelled as erosion types, vary with total bed porosity (φ) and applied shear stress (τ0). High‐porosity ooze (φ >80%) is characterized by constant erosion rates (Em). At φ <77%, however, erosion characteristics showed greater variance. Surface erosion was typically followed by transitional erosion (with asymptotically decreasing Em), and stages of erosion with constant, and exponential erosion rates. The estimated erosion thresholds (τc) vary from ca 0·05 to 0·08 Pa for the onset of surface erosion and up to ca 0·19 Pa for the onset of constant erosion (φ of 60 to 85%). Variability of deposition thresholds (τcd) from ca 0·04 to 0·13 Pa reflects the influence of variable suspended sediment concentration and τ0 on settling particle size due to the identified potential for chalk ooze aggregation and flocculation. Additionally, deposition thresholds seem to be affected by the size of eroded aggregates whose size correlates with bed porosity. Lastly, slow sediment transport without resuspension occurred in high‐porosity ooze as surface creep, forming low‐relief sedimentary features resembling ripples. This process represents a previously undescribed mode of fine‐grained nannofossil ooze transport. 相似文献