全文获取类型
收费全文 | 137篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
地球物理 | 46篇 |
地质学 | 62篇 |
海洋学 | 7篇 |
天文学 | 21篇 |
综合类 | 3篇 |
自然地理 | 6篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2014年 | 2篇 |
2013年 | 9篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 13篇 |
2007年 | 7篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1963年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有145条查询结果,搜索用时 140 毫秒
81.
Conglomerates of the Kuma Group, central Shikoku, southwest Japan contain Sanbagawa schist clasts with a variety of metamorphic grades and lithologies. K–Ar and 40 Ar/39 Ar dating of phengite show all the pelitic schist clasts from low- to high-grade zones have similar phengite ages (82–84 Ma) that are significantly older than those from the in situ Sanbagawa sequence of central Shikoku. This is because the Kuma–Sanbagawa sequence was exhumed earlier than the in situ Asemi sequence with an exhumation process intermediate between those for the Kanto Mountains and the in situ Asemi sequences. 40 A/39 Ar plateau ages (103 and 117 Ma) of phengite in amphibolites indicate the timing of the early stage of the exhumation of the metamorphic pile, probably close to the peak metamorphic age. 相似文献
82.
河口地层独居石Th(U)-Pb年龄对长江贯通时限的约束 总被引:6,自引:0,他引:6
新生代长江水系调整、东西贯通时限是国内外学者共同关注的问题。长江发展演化的复杂性在近一个世纪的河流沉积地貌学研究中得到充分的认识,但在贯通时限问题上难以形成共识。河口地层中碎屑独居石的电子探针Th(U)-Pb年龄较好地限定长江东西贯通的时间在2.58MaBP前后。随着碎屑矿物微区分析技术的发展,锆石、独居石年代学和微区特征将成为研究流域演化、构造运动的主要手段。 相似文献
83.
Yoshinobu Aramaki Takushi Yokoyama Yoshihiro Okaue Akira Imai Koichiro Watanabe 《Resource Geology》2005,55(3):281-284
Abstract. Silica scales containing large amounts of smectite were recently found in the pipelines for geothermal water at a geothermal power plant. To elucidate the mechanism of smectite formation, seven silica scale samples were characterized by powder X-ray diffraction, chemical analysis and 27 A1 MAS NMR. Smectite was present in samples with MgO levels above 10 wt% and Al2 O3 levels below 10 wt%. In 27 A1 MAS NMR spectra, peaks assigned to both tetrahedrally and octahedrally coordinated aluminum (Al(4) and Al(6)) were observed for Mg-rich samples, whereas a peak due to Al(4) alone appeared in Mg-poor samples. From these observation and comparison between 27 A1 MAS NMR spectra for synthesized precipitates of Al2 O3 -SiO2 containing MgO and not containing MgO, it is concluded that magnesium plays an important role in the stabilization of Al(6), and results in the formation of smectite 相似文献
84.
Scientific visits to Lake Nyos in Northwestern Cameroon in the aftermath of the gas disaster that killed over 1,750 people in 1986 revealed the presence of a pyroclastic natural dam in the northern border of the lake. This dam is being affected by back erosion. Collapse of the dam could cause a flood that would affect inhabited areas over a 220?km distance. Timing of dam collapse has been hotly debated based on vastly different carbon-14 and potassium-argon formation ages. In previous work, we used uranium series disequilibria to suggest a formation age of >5,000?years. Detailed comparison of uranium series and trace element data for lavas of Lake Nyos and Mt. Cameroon, both belonging to the Cameroon Volcanic Line, suggests that Lake Nyos basalts erupted with an initial radium-226/thorium-230 ratio that is two times higher than lavas erupting on Mt. Cameroon today. This information is used to infer an age of 8,750?±?490?years, which we suggest is the formation age of the Lake Nyos dam. The erosion rate deduced from this age does not indicate that collapse of the dam from back erosion alone and the attendant potential flood disaster are as eminent and alarming as previously thought. However, other factors militate for action to secure the dam. Work is underway to reinforce it by engineering methods. 相似文献
85.
J. Ignacio Martínez Christoph Mayr Yusuke Yokoyama Maria I. Velez Richard W. Battarbee 《Journal of Paleolimnology》2013,49(2):287-300
The stratigraphic, geochemical, and organic matter study of the late Holocene San Nicolás succession of the Cauca paleolake (Santa Fé–Sopetrán pull-apart basin) in the middle Cauca Valley, northern Colombia, suggests that it was deposited in a ria lake environment, at sedimentary accumulation rates in excess of 600 cm ky?1 between ~3500 and ~500 yr BP. Laminated deposition occurred, first under igapo (black-water), and then under varzea (white-water) conditions. The transition occurred ca. 3000 yr BP, a time of major change in El Niño/Southern Oscillation (ENSO) behavior in the Cariaco Basin, thus reflecting the southern migration of the intertropical convergence zone and intensified rain upstream the Cauca Valley. A second, but less conspicuous change occurred ca. 2000 yr BP, which apparently corresponds to the intensified and/or more frequent ENSO activity in the Galapagos Islands. Our contribution describes, for the first time, a ria lake sedimentary succession from the northern Andes and demonstrates the high potential of these hitherto undervalued deposits for the reconstruction of the paleohydrological history of the northern Andes. 相似文献
86.
Atsunori Nakamura Yusuke Yokoyama Hideaki Maemoku Hiroshi Yagi Makoto Okamura Hiromi Matsuoka Nao Miyake Toshiki Osada Hirofumi Teramura Danda Pani Adhikari Vishnu Dangol Yosuke Miyairi Stephen Obrochta Hiroyuki Matsuzaki 《第四纪科学杂志》2012,27(2):125-128
The Himalayas are a key location for understanding centennial‐ to millennial‐scale variations in the Asian monsoon, yet few studies of the late Holocene have been conducted in this sensitive area. Direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records, while terrestrial reconstructions (e.g. lake levels and spleothems) focus on precipitation. Here, we present the first evidence of terrestrial summer monsoon wind strength changes from Lake Rara, western Nepal, based on Mn/Ti ratios, a proxy for lake stratification. These data indicate a link between the Arabian Sea and the Himalayas, suggesting that centennial‐ to millennial‐scale changes in wind strength occurred synchronously. Distinct similarity is also observed between Lake Rara and the southern part of China, which may support previous suggestions that the southern part of China is influenced by Indian summer monsoon. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
87.
Polymerizations of organic monomers including amino acids, nucleotides and monosaccharides are essential processes for chemical evolution of life. Since these reactions proceed with “dehydration” reactions, they are possibly promoted if combined with thermodynamically favorable “hydration” reactions of minerals and salts. To test the possibility, we conducted heating experiments of the simplest amino acid “glycine (Gly)” mixed with four simple anhydrous salts (MgSO4, SrCl2, BaCl2 and Li2SO4) at 140 °C up to 20 days. Gly polymerization was strongly promoted by mixing with the salts in the order of MgSO4 > SrCl2 > BaCl2 > Li2SO4. Up to 6-mer of Gly polymers were synthesized in the Gly-MgSO4 mixture, and a total yield of Gly polymers attained about 7% of the initial amount of Gly by the 20 days heating. The total yield was about 200 times larger than that from the heating of Gly alone. XRD measurements of the Gly-MgSO4 mixture revealed the generation of MgSO4 monohydrate during Gly polymerization. These observations indicate that Gly polymerization was promoted by the salt hydrations through the hydration-dehydration interactions. Based on the observations, we tried to find a relationship between thermodynamic characteristics of the interactions and the promotion effects of each salt on Gly polymerization. It was found that the salts having lower hydration ΔrG0 (easier to hydrate) promote Gly polymerization more strongly. The relationship was used to estimate promotion effects of simple oxide minerals on Gly polymerization. The estimations were consistent with previous observations about the effects of these minerals on Gly polymerization. The fact suggests that the hydration-dehydration interactions between amino acids and minerals are an important mechanism for amino acids’ polymerizations on minerals. 相似文献
88.
Peng K. Hong Hiroko Miyahara Yusuke Yokoyama Yukihiro Takahashi Mitsuteru Sato 《Journal of Atmospheric and Solar》2011,73(5-6):587-591
We examined the effect of the 11-year solar cycle and quasi-biennial oscillation (QBO) on the ~27-day solar rotational period detected in tropical convective cloud activity. We analyzed the data of outgoing longwave radiation (OLR) for AD1979–2004, dividing into four different cases by the combination of high and low solar activities in terms of the 11-year variation, and easterly and westerly stratospheric winds associated with QBO. As a result, ~27-day variation has been most significantly detected in high solar activity period around the Indo-Pacific Warm Pool. Based on correlation analysis, we find that solar rotation signal can explain 10–20% of OLR variability around the tropical warm pool region during the high solar activity period. The spatial distribution has been, however, apparently different according to the phases of QBO. It is suggested that the 11-year solar cycle and stratospheric QBO have a possibility to cause large-scale oceanic dipole phenomena. 相似文献
89.
Tetsuo Kawakami Isao Yamaguchi Akira Miyake Tomoyuki Shibata Kenshi Maki Takaomi D. Yokoyama Takafumi Hirata 《Contributions to Mineralogy and Petrology》2013,165(3):575-591
Behavior of zircon at the schist/migmatite transition is investigated. Syn-metamorphic overgrowth is rare in zircon in schists, whereas zircon in migmatites has rims with low Th/U that give 90.3 ± 2.2 Ma U–Pb concordia age. Between inherited core and the metamorphic rim, a thin, dark-CL annulus containing melt inclusion is commonly developed, suggesting that it formed contemporaneous with the rim in the presence of melt. In diatexites, the annulus is further truncated by the brighter-CL overgrowth, suggesting the resorption and regrowth of the zircon after near-peak metamorphism. Part of the zircon rim crystallized during the solidification of the melt in migmatites. Preservation of angular-shaped inherited core of 5–10 μm in zircon included in garnet suggests that zircon of this size did not experience resorption but developed overgrowths during near-peak metamorphism. The Ostwald ripening process consuming zircon less than 5–10 μm is required to form new overgrowths. Curved crystal size distribution pattern for fine-grained zircons in a diatexite sample may indicate the contribution of this process. Zircon less than 20 μm is confirmed to be an important sink of Zr in metatexites, and ca. 35-μm zircon without detrital core are common in diatexites, supporting new nucleation of zircon in migmatites. In the Ryoke metamorphic belt at the Aoyama area, monazite from migmatites records the prograde growth age of 96.5 ± 1.9 Ma. Using the difference of growth timing of monazite and zircon, the duration of metamorphism higher than the amphibolite facies grade is estimated to be ca. 6 Myr. 相似文献
90.
The eddy covariance and energy balance method was employed to determine evapotranspiration (LE) over a wet temperate C3–C4 co‐existing grassland in Japan. After sensible heat flux (H) was estimated via the eddy covariance technique, LE was calculated as the residual of the energy budget with calibration against the direct measurements of LE by a lysimeter. Daily mean LE varied from 0·8 to 10·5 MJ d−1, with a peak at 16·5 MJ d−1 in late July to early August. Day‐to‐day and seasonal variability in LE was affected appreciably by net radiation (Rn), atmospheric vapour pressure deficit (VPD), canopy surface conductance (gc) and leaf area index (LAI). Before the canopy closure, LE responded to LAI in a linear manner. However, LE decreased with increasing LAI later in summer. Daytime variation in the decoupling coefficient (Ω) demonstrates that the canopy decoupled from the atmosphere in the morning and LE was primarily driven by the available energy, while in the afternoon the canopy partially coupled to the atmosphere so that LE was sensitive to VPD and gc. Throughout the whole measurement period, Ω was generally larger than 0·5, suggesting that the available energy contributes more to LE than VPD. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献