全文获取类型
收费全文 | 84篇 |
免费 | 13篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 1篇 |
地球物理 | 33篇 |
地质学 | 35篇 |
海洋学 | 12篇 |
天文学 | 19篇 |
综合类 | 1篇 |
自然地理 | 3篇 |
出版年
2024年 | 1篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有105条查询结果,搜索用时 437 毫秒
101.
Age gap between the intrusion of gneissose granitoids and regional high‐temperature metamorphism in the Ryoke belt (Mikawa area), central Japan
下载免费PDF全文
![点击此处可从《Island Arc》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kota Takatsuka Tetsuo Kawakami Etienne Skrzypek Shuhei Sakata Hideyuki Obayashi Takafumi Hirata 《Island Arc》2018,27(1)
The relationships between the intrusion of gneissose granitoids and the attainment of regional high‐T conditions recorded in metamorphic rocks from the Ryoke belt of the Mikawa area, central Japan, are explored. Seven gneissose granitoid samples (tonalite, granodiorite, granite) were collected from three distinct plutonic bodies that are mapped as the so‐called “Older Ryoke granitoids.” Based on bulk‐rock compositions and U–Pb zircon ages obtained by laser ablation inductively coupled plasma mass spectrometry, the analyzed granitoids can be separated into two groups. Gneissose granitoids from the northern part of the area give weighted mean 206Pb/238U ages of 99 ±1 Ma (two samples) and 95 ±1 Ma (one sample), whereas those from the southern part yield 81 ±1 Ma (two samples) and 78–77 ±1 Ma (two samples). Regional comparisons allow correlation of the northern granitoids (99–95 Ma) with the Kiyosaki granodiorite, and mostly with the Kamihara tonalite found to the east. The southern granitoids are tentatively renamed as “78–75 Ma (Hbl)?Bt granite” and “81–75 Ma Hbl?Bt tonalite” (Hbl, hornblende; Bt, biotite). and seem to be broadly coeval members of the same magmatic suite. With respect to available age data, no gneissose granitoid from the Mikawa area shows a U–Pb zircon age which matches that of high‐T metamorphism (ca 87 Ma). The southern gneissose granitoids (81–75 Ma), although they occur in the highest‐grade metamorphic zone, do not seem to represent the heat source which produced the metamorphic field gradient with a low dP/dT slope. 相似文献
102.
The Japanese archipelago underwent two arc–arc collisions during the Neogene. Southwest Honshu arc collided with the Izu‐Bonin‐Mariana arc and the northeast Honshu arc collided with the Chishima arc. The complicated geological structure of the South Fossa Magna region has been attributed to the collision between the Izu‐Bonin‐Mariana arc and the southwest Honshu arc. Understanding the geotectonic evolution of this tectonically active region is crucial for delineating the Neogene tectonics of the Japanese archipelago. Many intrusive granitoids occur around the Kofu basin, in the South Fossa Magna region. Although the igneous ages of these granitoids have been mainly estimated through biotite and hornblende K–Ar dating, here, we perform U–Pb dating of zircon to determine the igneous ages more precisely. In most cases, the secondary post‐magmatic overprint on the zircon U–Pb system was minor. Based on our results, we identify four groups of U–Pb ages: ca 15.5 Ma, ca 13 Ma, ca 10.5 Ma, and ca 4 Ma. The Tsuburai pluton belongs to the first group, and its age suggests that the granite formation within the Izu‐Bonin‐Mariana arc dates back to at least 15.5 Ma. The granitoids of the second group intruded into the boundary between the Honshu arc and the ancient Izu‐Bonin‐Mariana arc, suggesting that the arc–arc collision started by ca 13 Ma. As in the case of the Kaikomagatake pluton, the Chino pluton likely corresponds to a granodiorite formed in a rear‐arc setting in parallel with the other granodiorites of the third group. The U–Pb age of the Kogarasu pluton, which belongs to the fourth group, is the same as those of the Tanzawa tonalitic plutons. This might support a syncollisional rapid granitic magma formation in the South Fossa Magna region. 相似文献
103.
The Paleo‐Kuril Arc in the eastern Hokkaido region of Japan, the westernmost part of the Kuril Arc in the northwestern Pacific region, shows a tectonic bent structure. This has been interpreted, using paleomagnetic data, to be the result of block rotations in the Paleo‐Kuril Arc. To understand the timing and origin of this tectonic bent structure in the Paleo‐Kuril arc‐trench system, paleomagnetic surveys and U–Pb radiometric dating were conducted in the Paleogene Urahoro Group, which is distributed in the Shiranuka‐hill region, eastern Hokkaido. The U–Pb radiometric dating indicated that the Urahoro Group was deposited at approximately 39 Ma. Paleomagnetic analysis of the Urahoro Group suggested that the Shiranuka‐hill region experienced a 28° clockwise rotation with respect to East Asia. The degree of clockwise rotation implied from the Urahoro Group is smaller than that of the underlying Lower Eocene Nemuro Group (62°) but larger than that of the overlying Onbetsu Group (?9°). It is thus suggested that the Shiranuka‐hill region experienced a clockwise rotation of approximately 34° between the deposition of the Nemuro and Urahoro Groups (50–39 Ma), and a 38° clockwise rotation between the deposition of the Urahoro and Onbetsu Groups (39–34 Ma). The origin of the curved tectonic belt of the Paleo‐Kuril Arc was previously explained by the opening of the Kuril Basin after 34 Ma. The age constraint for the rotational motion of the Shiranuka‐hill region in this study contradicts this hypothesis. Consequently, it is suggested that the process of arc–arc collision induced the bent structure of the western Paleo‐Kuril Arc. 相似文献
104.
Shizuo Tsunogai Shuichi Watanabe Makio Honda Takafumi Aramaki 《Journal of Oceanography》1995,51(5):519-536
The importance of the North Pacific Intermediate Water as a sink for the anthropogenic carbon dioxide has been examined by mapping chemical and radiochemical properties at two isopycnal surfaces of of 26.6 ad 27.2 obtained in 1970's. Its radiocarbon contents in 1980's were determined for comparison. The isopleths of depth and salinity at the two isopycnal surfaces obviously show that the intermediate layer of the entire mid-latitudes of the North Pacific is occupied by a similar water mass. The distributions of dissolved oxygen contents and Si/N ratios in the intermediate water indicate its source in the northwestern North Pacific and its sink in the eastern Pacific. The 14C values clearly designate the intrusion of the artificial radiocarbon of mostly 1960's origin into the upper intermediate water of the western North Pacific having its maximum in the subarctic zone of 40–45°N and 160–180°E in 1973. The maximum region for tritium is much broader extending to the north. These suggest that the subboreal region is active in the gas exchange and/or the warm water residing for a long time at the surface and flowing into the region across the subarctic front sinks quickly in winter. At the lower isopycnal surface, the increase 14C value for 14±4 years was around 27, which is smaller than that expected from the total carbonate increase, indicating an active isopycnal mixing. 相似文献
105.
The retinal structure and visual acuity in Japanese flounderParalichthys olivaceus at different stages of development were examined by light microscopy. The resolving power of the retina, the visual axis
and the best visual field were estimated based on the distribution of cone cells in the retina. The visual system of the larvae
appears poorly developed at hatching. The larvae with total length (TL) of less than 10 mm, have single cones only and the
eyes were well pigmented. At 10–11 mm TL, most single cones fused to form double cones, with the single and double cones forming
a mosaic pattern. From larvae to early juvenile the retina stretches, the cones increase in diameter and rods increase in
number. Based on the highest density of the cones in the ventro-temporal region, the visual axis was orientated upforward.
The resolving power of the retina in 40–530 mm TL Japanese flounder was found to range from 25.1 to 11.5 min. The results
indicated continual improvements in the visual system of the growing fish towards higher resolving power, visual acuity and
sensitivity.
Project 39970578 supported by the NSFC, and also supported by the Ministry of Education Foundation for University Key Teachers. 相似文献