全文获取类型
收费全文 | 527篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 18篇 |
地球物理 | 157篇 |
地质学 | 157篇 |
海洋学 | 56篇 |
天文学 | 120篇 |
自然地理 | 48篇 |
出版年
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 15篇 |
2019年 | 11篇 |
2018年 | 22篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 19篇 |
2014年 | 12篇 |
2013年 | 39篇 |
2012年 | 19篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 36篇 |
2008年 | 24篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 17篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有567条查询结果,搜索用时 839 毫秒
471.
J. M. Teal J. W. Farrington K. A. Burns J. J. Stegeman B. W. Tripp B. Woodin C. Phinney 《Marine pollution bulletin》1992,24(12):607-614
The barge Florida spilled No. 2 fuel oil into Buzzards Bay, Massachusetts on 29 September 1969. Sediments from five of the original stations were sampled in August 1989 and analysed for fuel oil hydrocarbons. Two subtidal and one intertidal marsh station showed no evidence of fuel oil. One subtidal mud core had traces of biodegraded fuel oil at 10–15 cm. One marsh core contained 10−6 g g−1 dry wt of weathered and biodegraded fuel oil aromatic hydrocarbons and cycloalkanes at 5–10 cm with lesser concentrations at 0–5 and 10–15 cm. Although present in trace concentrations, these hydrocarbons appear to be slightly inducing cytochrome P4501A in marsh fish (Fundulus heteroclitus). 相似文献
472.
473.
Bhaleka D. Persaud Krysha A. Dukacz Gopal C. Saha Amber Peterson Laleh Moradi Stephen O'Hearn Erin Clary Juliane Mai Michael Steeleworthy Jason J. Venkiteswaran Homa Kheyrollah Pour Brent B. Wolfe Sean K. Carey John W. Pomeroy Chris M. DeBeer James M. Waddington Philippe Van Cappellen Jimmy Lin 《水文研究》2021,35(11):e14385
Water science data are a valuable asset that both underpins the original research project and bolsters new research questions, particularly in view of the increasingly complex water issues facing Canada and the world. Whilst there is general support for making data more broadly accessible, and a number of water science journals and funding agencies have adopted policies that require researchers to share data in accordance with the findable, accessible, interoperable, reusable (FAIR) principles, there are still questions about effective management of data to protect their usefulness over time. Incorporating data management practices and standards at the outset of a water science research project will enable researchers to efficiently locate, analyse and use data throughout the project lifecycle, and will ensure the data maintain their value after the project has ended. Here, some common misconceptions about data management are highlighted, along with insights and practical advice to assist established and early career water science researchers as they integrate data management best practices and tools into their research. Freely available tools and training opportunities made available in Canada through Global Water Futures, The Gordon Foundation DataStream, the Digital Research Alliance of Canada Portage Network, Compute Canada, and university libraries, among others are compiled. These include webinars, training videos, and individual support for the water science community that together enable researchers to protect their data assets and meet the expectations of journals and funders. The perspectives shared here have been developed as part of the Global Water Futures programme's efforts to improve data management and promote the use of common data practices and standards in the context of water science in Canada. Ten best practices are proposed that may be broadly applicable to other disciplines in the natural sciences and can be adopted and adapted globally. 相似文献
474.
Matthew R. Hall Sacha J. Mooney Craig Sturrock Paolo Matelloni Sean P. Rigby 《Acta Geotechnica》2013,8(1):67-79
An experimental approach to the characterisation of the complex, multi-scale pore geometry in cement-stabilised soils is presented, in which the pore size distribution inclusively spans at least six orders of magnitude from ~3 nm up to >3 mm. These most likely result from the combined effects of granular inter-particle packing, clay/cement clothing and bridging effects, cement hydration and clay/cement pozzolanic reactions, and alteration of larger pore geometries as a result of solid mass mobilisation and transport following capillary wetting/drying regimes. Experimental data are presented and were obtained through a combination of X-ray computed tomography, mercury intrusion porosimetry and N2 physisorption supported by ‘wet mode’ environmental scanning electron microscopy. Data strongly suggest that macropore/capillary pore size distribution, mean pore size, sorptivity and transport coefficients are a function of particle size distribution (when compaction energy is constant). Mesopore size distribution, which dominates hygric sorption/desorption behaviour, occurs within the clay/cement matrix and also appears to be strongly influenced by the particle size distribution of the granular phase. All other factors being equal, manipulation of granular particle size distribution can be used to engineer the hygric (vapour) and capillary (liquid) potentials and also the fluid transport coefficients of these materials. 相似文献
475.
34S/32S ratios have been measured in a suite of samples from the stratabound, volcanogenic massive sulphide deposit at Woodlawn, N.S.W. 34S values for the sulphides vary as follows: in the ore horizon, pyrite +6.7 to +9.2%. (mean +8.1‰), sphalerite +5.2 to +8.6‰. (mean +6.9‰), chalcopyrite +6.4 to +7.0‰ (mean +6.7‰) and galena +2.8 to +5.5‰ (mean +4.4‰); in the vein mineralization, the host volcanics—pyrite +8.7 to +11.4%. (mean +9.8‰), sphalerite +7.8 to + 10.3‰ (mean +9.2‰), chalcopyrite; +8.8 to +10.1‰ (mean +9.2‰) and galena +6.9 to +7.2‰ (mean +7.1‰). Barite from the upper ore horizon levels has an isotopic composition of +30.0‰, consistent with its having originated from Silurian ocean sulphate. The general order of 34S enrichment in the sulphides is pyrite > chalcopyrite ~ sphalerite > galena. Isotopic fractionations in the systems galena/sphalerite/pyrite and chalcopyrite/pyrite indicate an equilibration temperature of 275–300°C. This temperature is considered to represent that of sulphide deposition. 相似文献
476.
This paper reviews the processes of tree uprooting, examines the classification of pit and mound microtopography and assesses the effects of tree uprooting on soil mixing and genesis. The processes by which soil-horizon clasts are mixed as they slump off the root plate, and the ultimate patterns of soil horizonation within mounds, are primary foci of the paper. Longevity of treethrow mounds can exceed 2000 years, making these landforms more lasting features than is often assumed. Because of their great longevity, the pits and mounds formed by uprooting have lasting effects on soil morphology. Soils of these microsites often classify in different soil orders or suborders than do adjacent, less disturbed soils. The importance of tree uprooting to mass movement processes is examined. In some areas uprooting may be the primary mass wasting mechanism. Nonetheless, estimates of the amount of sediment moved and the net distance of transport vary greatly and may in some cases be overestimated. [Key words: pedoturbation, microtopography, pit/mound topography, mass wasting, geomorphology.] 相似文献
477.
Thomas P. Sparn Gary Rottman Thomas N. Woods Brian D. Boyle Richard Kohnert Sean Ryan Randall Davis Robert Fulton William Ochs 《Solar physics》2005,230(1-2):71-89
The Solar Radiation and Climate Experiment, SORCE, is a satellite carrying four scientific instruments that measure the total
solar irradiance and the spectral irradiance from the ultraviolet to the infrared. The instruments were all developed by the
Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder. The spacecraft carrying and accommodating
the instruments was developed by Orbital Sciences Corporation in Dulles, Virginia. It is three-axis stabilized with a control
system to point the instruments at the Sun, as well as the stars for calibration. SORCE was successfully launched from the
Kennedy Space Center in Florida on 25 January 2003 aboard a Pegasus XL rocket. The anticipated lifetime is 5 years, with a
goal of 6 years. SORCE is operated from the Mission Operations Center at LASP where all data are collected, processed, and
distributed. This paper describes the SORCE spacecraft, integration and test, mission operations, and ground data system. 相似文献
478.
Sean Matt † Ralph E. Pudritz † 《Monthly notices of the Royal Astronomical Society》2005,356(1):167-182
479.
Evidence for high temperature and 18O‐enriched fluids in the Arab‐D of the Ghawar Field,Saudi Arabia 下载免费PDF全文
Peter K. Swart Dave L. Cantrell Monica M. Arienzo Sean T. Murray 《Sedimentology》2016,63(6):1739-1752
Using the clumped isotope method, the temperature of dolomite and calcite formation and the oxygen isotopic composition (δ18Ow) of the diagenetic fluids have been determined in a core taken from the Arab‐D of the Ghawar field, the largest oil reservoir in the world. These analyses show that while the dolomites and limestones throughout the major zones of the reservoir recrystallized at temperatures between ca 80°C and 100°C, the carbonates near the top of the reservoir formed at significantly lower temperatures (20 to 30°C). Although the δ18O values of the diagenetic fluids show large variations ranging from ca <0‰ to ca +8‰, the variations exhibit consistent downhole changes, with the highest values being associated with the portion of the reservoir with the highest permeability and porosity. Within the limestones, dolomites and dolomites associated with the zone of high permeability, there are statistically significant different trends between the δ18Ow values and recrystallization temperature. These relationships have different intercepts suggesting that fluids with varying δ18Ow values were involved in the formation of dolomite and limestone compared to the formation of dolomite associated with the zone of high permeability. These new data obtained using the clumped isotope technique show how dolomitization and recrystallization by deep‐seated brines with elevated δ18Ow values influence the δ18O values of carbonates, possibly leading to erroneous interpretations unless temperatures can be adequately constrained. 相似文献
480.
Sean G. Deen M. Jim Hendry S. Lee Barbour Soumya Das Joseph Essilfie-Dughan 《Chemie der Erde / Geochemistry》2022,82(1):125863
The mechanisms of abiotic sequestration of Se(VI) and Se(IV) on a sample of coal waste rock collected from the Elk Valley, Canada and on three pure mineral species (i.e., siderite, pyrite, and sphalerite) present in coal waste rock were assessed using sterile batch testing under water-saturated, anoxic conditions. Only siderite removed measurable Se(VI) from the test solutions with ~90% removal after 100 d attributed to initial adsorption to the siderite surface as Se(VI) and subsequent reduction to Se(IV) and Se(0). In contrast to Se(VI), all samples removed Se(IV) from the aqueous solutions. The rate of Se(IV) removal was pyrite > siderite > waste rock > sphalerite. The waste rock sample removed Se(IV) from solution in two stages: up to ~40% of the aqueous Se(IV) was rapidly removed (by day 1) followed by slower removal of Se(IV) with up to ~97% removal after 99 d. Se(IV) removal is attributed to the adsorption of Se(IV) and subsequent reduction to Se(0) onto the siderite and pyrite phases of the waste rock. The initial (1 d) removal of Se(IV) by waste rock was characterized using a distribution coefficient (Kd) of 15.5 L/kg. Longer-term Se(IV) removal was fitted with zero and first order removal rates. The removal of Se(IV) by sphalerite was minor and deemed to have a minimal effect on Se sequestration in the waste rock. Desorption tests on waste rock showed that the fraction of sequestered Se susceptible to desorption decreased with time as adsorbed Se(IV) was reduced to insoluble Se(0). These findings show that abiotic Se sequestration can occur in saturated, anoxic zones in coal waste rock dumps. 相似文献