全文获取类型
收费全文 | 1116篇 |
免费 | 129篇 |
国内免费 | 213篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 53篇 |
地球物理 | 196篇 |
地质学 | 685篇 |
海洋学 | 279篇 |
天文学 | 3篇 |
综合类 | 59篇 |
自然地理 | 173篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 36篇 |
2019年 | 41篇 |
2018年 | 30篇 |
2017年 | 53篇 |
2016年 | 46篇 |
2015年 | 38篇 |
2014年 | 83篇 |
2013年 | 93篇 |
2012年 | 94篇 |
2011年 | 74篇 |
2010年 | 49篇 |
2009年 | 79篇 |
2008年 | 81篇 |
2007年 | 57篇 |
2006年 | 66篇 |
2005年 | 49篇 |
2004年 | 41篇 |
2003年 | 55篇 |
2002年 | 50篇 |
2001年 | 35篇 |
2000年 | 36篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 29篇 |
1996年 | 23篇 |
1995年 | 29篇 |
1994年 | 29篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有1458条查询结果,搜索用时 437 毫秒
171.
Eastern Marmara region consists of three different morphotectonic units: Thrace–Kocaeli Peneplain (TKP) and Çamdağ–Akçakoca Highland (ÇAH) in the north, and Armutlu–Almacık Highland in the south of the North Anatolian Fault Zone (NAFZ). The geologic‐morphologic data and seismic profiles from the Sakarya River offshore indicate that the boundary between the TKP in the west and ÇAH in the east is a previously unrecognized major NNE–SSW‐trending strike‐slip fault zone with reverse component. The fault zone is a distinct morphotectonic corridor herein named the Adapazarı–Karasu corridor (AKC) that runs along the Sakarya River Valley and extends to its submarine canyon along the southern margin of the Black Sea in the north. It formed as a transfer fault zone between the TKP and ÇAH during the Late Miocene; the former has been experiencing extensional forces and the latter compressional forces since then. East–West‐trending segments of the NAFZ cuts the NE–SW‐trending AKC and their activity has resulted in the formation of a distinct fault‐bounded morphology, which is characterized by alternating E–W highlands and lowlands in the AKC. Furthermore, this activity has resulted in the downward motion of an ancient delta and submarine canyon of the Sakarya River in the northern block of the NAFZ below sea level so that the waters of the Black Sea invaded them. The NE–SW‐trending faults in the AKC were reactivated with the development of the NAFZ in the Late Pliocene, which then caused block motions and microseismic activities throughout the AKC. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
172.
173.
An intensive survey has been conducted of the distributions of some chemical properties (dissolved oxygen, nutrients and carbonate
properties) in the Kuroshio/Oyashio Interfrontal Zone. Many low-salinity water patches were found down to depths of 640 m.
Each chemical property also showed anomalies in these patches, but the degree of variation showed a low correlation with salinity.
This may be due to the high variability of biological processes in the surface waters where these patches are formed. Vertical
profiles of the chemical properties were also observed along the Kuroshio extension axis from 140.50°E to 146.75°E. The concentrations
of nutrients and total carbonate (TC) in the water having densities greater than σθ=26.60 can be regarded as being formed by the isopycnal mixing of the Kuroshio component water and Oyashio component water
and biological degradation within the density surfaces. This implies that the transport of chemical properties by the diapycnal
mixing is negligible in these density layers in the K/O zone. 相似文献
174.
辽西兰家沟钼矿区成矿构造、岩浆演化及成矿作用 总被引:7,自引:0,他引:7
根据兰家沟钼矿区控矿旋卷构造特征、燕山期花岗岩体的岩石化学特征、稀土元素特征和成矿元素含量,讨论了该矿区形成的地质构造条件和岩浆演化分异作用在钼矿床形成过程中的成矿作用和找矿前景。 相似文献
175.
176.
For first time, during 1991, seismic activity was recorded during an eruption at Colima volcano. We analyze these data to
obtain a stress pattern using a composite focal mechanism technique. From the analysis of regional seismicity, the Tamazula
Fault and the Armeria River appear as active features and the dip of the slab east of the Jalisco Block is approximately 12°.
Southwest of Colima volcano a vertical alignment of seismic events was observed. We estimate five different composite focal
mechanism solutions from our data set, which indicate a change of the stress field at the volcano after the 1991 eruption.
These solutions suggest that the stress field in the volcanic edifice was controlled by stresses related to the emplacement
of magma superimposed on the regional stress field. No evidence of active local faults in the volcanic edifice was found.
We propose a model for the eruptive process that involves tilting of the volcanic edifice.
Received: 15 October 1995 / Accepted: 26 October 1998 相似文献
177.
Internal morphology, habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps) 总被引:52,自引:2,他引:50
Gerhard Vavra Rolf Schmid Dieter Gebauer 《Contributions to Mineralogy and Petrology》1999,134(4):380-404
Several types of growth morphologies and alteration mechanisms of zircon crystals in the high-grade metamorphic Ivrea Zone
(IZ) are distinguished and attributed to magmatic, metamorphic and fluid-related events. Anatexis of pelitic metasediments
in the IZ produced prograde zircon overgrowths on detrital cores in the restites and new crystallization of magmatic zircons
in the associated leucosomes. The primary morphology and Th-U chemistry of the zircon overgrowth in the restites show a systematic
variation apparently corresponding to the metamorphic grade: prismatic (prism-blocked) low-Th/U types in the upper amphibolite
facies, stubby (fir-tree zoned) medium-Th/U types in the transitional facies and isometric (roundly zoned) high-Th/U types
in the granulite facies. The primary crystallization ages of prograde zircons in the restites and magmatic zircons in the
leucosomes cannot be resolved from each other, indicating that anatexis in large parts of the IZ was a single and short lived
event at 299 ± 5 Ma (95% c. l.). Identical U/Pb ages of magmatic zircons from a metagabbro (293 ± 6 Ma) and a metaperidotite
(300 ± 6 Ma) from the Mafic Formation confirm the genetic context of magmatic underplating and granulite facies anatexis in
the IZ. The U-Pb age of 299 ± 5 Ma from prograde zircon overgrowths in the metasediments also shows that high-grade metamorphic
(anatectic) conditions in the IZ did not start earlier than 20 Ma after the Variscan amphibolite facies metamorphism in the
adjacent Strona–Ceneri Zone (SCZ). This makes it clear that the SCZ cannot represent the middle to upper crustal continuation
of the IZ. Most parts of zircon crystals that have grown during the granulite facies metamorphism became affected by alteration
and Pb-loss. Two types of alteration and Pb-loss mechanisms can be distinguished by cathodoluminescence imaging: zoning-controlled
alteration (ZCA) and surface-controlled alteration (SCA). The ZCA is attributed to thermal and/or decompression pulses during
extensional unroofing in the Permian, at or earlier than 249 ± 7 Ma. The SCA is attributed to the ingression of fluids at
210 ± 12 Ma, related to hydrothermal activity during the breakup of the Pangaea supercontinent in the Upper Triassic/Lower
Jurassic.
Received: 7 July 1998 / Accepted: 4 November 1998 相似文献
178.
中国大地构造格局和主要地球物理场分布十分吻合,一些主要地球物场的演化促使若干金属元素成矿,地幔热柱,幔隆和幔坳转换带,莫霍斜坡带,俯冲带等和成矿区关系密切。 相似文献
179.
Synthesis of Environmental Impacts of Deep Seabed Mining 总被引:1,自引:0,他引:1
180.
《地震研究进展(英文)》2023,3(1):100198
We present a detailed catalog of 13 671 earthquakes in the Eastern Tennessee Seismic Zone (ETSZ) that spans January 1, 2005 to July 31, 2020. We apply a matched filter detection technique on over 15 years of continuous data, resulting in arguably the most complete catalog of seismicity in the ETSZ yet. The magnitudes of newly detected events are determined by computing the amplitude ratio between the detections and templates using a principal component fit. We also compute the b-value for the new catalog and comparatively relocate a subset of newly detected events using XCORLOC and hypoDD, which shows a more defined structure at depth. We find the greatest concentration along and to the east of the New York-Alabama Lineament, as defined by the magnetic anomaly, supporting the argument that this feature likely is related to the generation of seismicity in the ETSZ. We examine seismicity in the vicinity of the Watts Bar Reservoir, which is located about 5 ?km from the epicenter of the MW 4.4 December 12, 2018 Decatur, Tennessee earthquake, and find possible evidence for reservoir modulated seismicity in this region. We also examine seismicity in the entire ETSZ to search for a correlation between shallow earthquakes and seasonal hydrologic changes. Our results show limited evidence for hydrologically-driven shallow seismicity due to seasonal groundwater levels in the ETSZ, which contradicts previous studies hypothesizing that most intraplate earthquakes are associated with the dynamics of hydrologic cycles. 相似文献