全文获取类型
收费全文 | 1831篇 |
免费 | 338篇 |
国内免费 | 570篇 |
专业分类
测绘学 | 51篇 |
大气科学 | 61篇 |
地球物理 | 349篇 |
地质学 | 1376篇 |
海洋学 | 556篇 |
天文学 | 10篇 |
综合类 | 68篇 |
自然地理 | 268篇 |
出版年
2024年 | 12篇 |
2023年 | 38篇 |
2022年 | 79篇 |
2021年 | 66篇 |
2020年 | 102篇 |
2019年 | 118篇 |
2018年 | 95篇 |
2017年 | 121篇 |
2016年 | 98篇 |
2015年 | 69篇 |
2014年 | 99篇 |
2013年 | 145篇 |
2012年 | 97篇 |
2011年 | 68篇 |
2010年 | 89篇 |
2009年 | 126篇 |
2008年 | 131篇 |
2007年 | 113篇 |
2006年 | 117篇 |
2005年 | 92篇 |
2004年 | 87篇 |
2003年 | 98篇 |
2002年 | 92篇 |
2001年 | 66篇 |
2000年 | 62篇 |
1999年 | 56篇 |
1998年 | 53篇 |
1997年 | 52篇 |
1996年 | 55篇 |
1995年 | 62篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有2739条查询结果,搜索用时 15 毫秒
101.
Submarine groundwater discharge revealed by aerial thermal infrared imagery: a case study on Jeju Island,Korea 下载免费PDF全文
Eunhee Lee Ki‐mook Kang Sung Pil Hyun Kil‐Yong Lee Heesung Yoon Seung Hee Kim Yongcheol Kim Zhen Xu Duk‐jin Kim Dong‐Chan Koh Kyoochul Ha 《水文研究》2016,30(19):3494-3506
Submarine groundwater discharge (SGD) is a global phenomenon that carries large volumes of groundwater and dissolved chemical species such as nutrient, metals, and organic compounds to coastal zones. We report the influence of SGD on the coastal waters of Jeju Island, Korea, using high‐resolution aerial thermal infrared (TIR) mapping techniques and field investigations. An aircraft‐based system was implemented using a cost‐effective TIR camera for aerial TIR mapping. Ground‐based calibrations and system integration with GPS/IMU (global positioning system/inertial measurement unit) were performed for the aerial systems. The aerial surveys showed distinct low‐temperature signatures of SGD along the coasts of Jeju Island, revealing large groundwater inputs from the coastal aquifers to the ocean. Multiple aerial surveys over a range of seasons and tidal stages revealed that SGD rates dynamically affect the sea surface temperature (SST) of the coastal zone. The in‐situ measurements supported that SGD has a substantial influence on the coastal water chemistry as well as SST. Our observations highlight the extent to which aerial‐based TIR mapping can serve as a powerful tool for studying SGD and other coastal processes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
102.
Xiaochun Liu Yi Chen Wei‐ Wang Mengmeng Xia Juan Hu Yibing Li Daogong Hu Biao Song 《Journal of Metamorphic Geology》2021,39(1):101-132
High‐P (HP) eclogite and associated garnet–omphacite granulite have recently been discovered in the Mulantou area, northeastern Hainan Island, South China. These rocks consist mainly of garnet, omphacite, hornblende, quartz and rutile/ilmenite, with or without zoisite and plagioclase. Textural relationships, mineral compositions and thermobarometric calculations demonstrate that the eclogite and garnet–omphacite granulite share the same three‐stage metamorphic evolution, with prograde, peak and retrograde P?T conditions of 620–680°C and 8.7–11.1 kbar, 820–860°C and 17.0–18.2 kbar, and 700–730°C and 7.1–8.5 kbar respectively. Sensitive high‐resolution ion microprobe U–Pb zircon dating, coupled with the identification of mineral inclusions in zircon, reveals the formation of mafic protoliths before 355 Ma, prograde metamorphism at c. 340–330 Ma, peak to retrograde metamorphism at c. 310–300 Ma, and subsequent pegmatite intrusion at 295 Ma. Trace element geochemistry shows that most of the rocks have a MORB affinity, with initial εNd values of +2.4 to +6.7. As with similar transitional eclogite–HP granulite facies rocks in the thickened root in the European Variscan orogen, the occurrence of relatively high P?T metamorphic rocks of oceanic origin in northeastern Hainan Island suggests Carboniferous oceanic subduction leading to collision of the Hainan continental block, or at least part of it, with the South China Block in the eastern Palaeo‐Tethyan tectonic domain. 相似文献
103.
It is generally believed that andesite–dacite–rhyolite suites and contemporary porphyry Cu deposits are related to subduction in active continental margin settings. However, it is still unclear which tectonic events result in the generation of porphyry Cu deposits and whether asthenospheric mantle material is involved in this process. Widespread andesitic–dacitic felsic intrusions associated with porphyry Cu deposits and rarer basalts have been identified in the Late Triassic southern Yidun arc (SYA) of eastern Tibet. However, few geochronological and geochemical data are available for these basalts, thereby hampering the development of geodynamic models for this magmatic event and the formation of related porphyry Cu deposits in the region. Here we present the first geochemical and SIMS (secondary ion mass spectrometry) zircon U–Pb data of Xiaxiaoliu basalts in the SYA. The age of the Late Triassic Xiaxiaoliu basalts (216.1 ± 2.8 Ma) is consistent with the timing of emplacement of voluminous porphyritic intrusions and the formation of Cu deposits within the SYA (peaking at 215–217 Ma). The Xiaxiaoliu basalts have E-MORB-like trace element patterns that are free of negative Nb–Ta anomalies, and have high 143Nd/144Nd(t) values, suggesting they were sourced from asthenospheric mantle without any arc-type influence. These observations, combined with the fact that some Late Triassic mineralized porphyritic intrusions within the SYA have adakitic affinities, suggest that the basalts and other igneous rocks and associated porphyry Cu deposits within the SYA were produced by tearing of a westward-dipping slab, triggering the upwelling of asthenospheric mantle material during subduction of the Garze–Litang Ocean crust. 相似文献
104.
中条山地区郭家沟基性-超基性岩体的岩石成因及地质意义 总被引:1,自引:0,他引:1
文章通过对中条山地区郭家沟基性-超基性岩体的岩石学、矿物学和岩石地球化学方面的分析研究,讨论了该岩体的形成时代、岩石成因、及其地质意义。郭家沟岩体侵入时代为元古代,可能与绛县群形成时代较为相近(2200Ma左右)。郭家沟岩体具有岩相分带现象,边缘相为辉长岩,向内渐变过渡为含长辉石岩、变余辉石岩(角闪石岩)等,在岩体的中心发育着磁铁透闪石岩;岩石中Mg O与其他主量元素线性相关,各类岩石地球化学特征较为相似,显示出岩石受分离结晶作用的影响,具有岩浆同源演化的趋势;岩石总体显示出低硅、低镁、高铁、高钛、高钙的特征,相对富集LREE和LILE,而亏损HREE和Nb、Ta、Zr、Y等高场强元素,轻重稀土分馏明显,具有较弱的Eu异常,V含量较高,具有阿拉斯加型侵入岩体和与火山弧相关的岩浆特征。从岩石组合及地球化学特征结合区域构造演化,认为岩体形成于大陆边缘弧的构造环境,从侧面也说明绛县群的形成环境应该是大陆边缘俯冲后的伸展环境,而非陆内裂谷。 相似文献
105.
I. D. Lindley 《Australian Journal of Earth Sciences》2016,63(6):731-754
Woodlark Island (Muyuw) is located in a tectonically complex region, one of the few places on Earth where continental breakup is occurring ahead of seafloor spreading. Rifting commenced in the late Miocene (8.8–6 Ma) and is associated with the westward-propagating Woodlark Basin Spreading Centre. The island comprises approximately 850 km2 of raised Pleistocene coral reef and associated sediments with a central, moderately elevated range underlain by the middle Miocene calc-alkaline to shoshonitic Okiduse Volcanic Group (new name). It provides an exposure of upper Cenozoic geology in close proximity to the spreading centre. The Okiduse Volcanic Group is host to most of the island's historical gold and silver production and recently defined mineral resources totalling 1.75 Moz gold. This study uses facies analysis of pyroclastic deposits to develop a detailed geological map of the Okiduse Volcanic Group, with a revision and reinterpretation of the unit. Facies associations suggest that two major volcanic centres erupted synchronously during the middle Miocene (14–12 Ma), referred to as the Watou Mountain Eruptive Centre (new name) and the Uvarakoi Caldera (new name). The mafic–intermediate Watou Mountain Eruptive Centre formed during frequent small eruptions of widely varying style. Strombolian, subplinian, vulcanian and dome-related explosive eruptions occurred, alternating with extrusion of block and ash flow deposits and lava domes. Pyroclastic deposits were rapidly reworked from the steep cone, and were redeposited in a series of coalescing aprons surrounding the volcano. The felsic Uvarakoi Caldera formed during a series of violent explosive eruptions by rapid removal of magma from the underlying chamber, followed by collapse. Plinian and possibly phreatoplinian eruptions, as a result of magma–water mixing in the surface environment, resulted in widely dispersed, highly fragmented tuff deposits. The caldera was modified by widespread erosion following eruptions, resulting in fluvial, laharic and slope-wash deposits. This study highlights lithological controls (porosity and permeability) by various units within the Okiduse Volcanic Group on ore deposition. 相似文献
106.
R. A. Duncan P. G. Quilty J. Barling J. M. Fox 《Australian Journal of Earth Sciences》2016,63(1):81-89
We report 40Ar–39Ar laser step-heating age determinations on 15 stratigraphically controlled lava flows and intrusive rocks from Heard Island, Central Kerguelen Plateau (Indian Ocean). The island history began with uplift of pelagic limestone intruded by 22 Ma gabbro sills. Subaerial and wave erosion levelled the early island, producing an unconformity onto which pillow lavas, tuffaceous sediments and shallow-water, fossiliferous marine siltstone (Drygalski Formation) were deposited, beginning in late Miocene time. Two volcanic systems then formed in the late Quaternary. Big Ben dominates the larger southeast part of the island, while Mount Dixon occupies the northwest Laurens Peninsula. Feeder dykes and the early lava flows in both systems are 400–200 ka. Lava flows with evolved compositions (trachytes, trachyandesites) erupted 100–20 ka. Well-preserved parasitic cones exposed at low elevations are 15–10 ka and younger. Mawson Peak, near the summit of Big Ben, has erupted lava flows as recently as 2007. Heard Island, and nearby active McDonald Island, are subaerial features of a larger Neogene volcanic region of Central Kerguelen Plateau that includes several large sea knolls and recently identified submarine fields of small cones. This broadly distributed volcanic activity is linked to incubation of plume material at the base of the nearly stationary overlying Central Kerguelen Plateau. 相似文献
107.
108.
长江中下游庐枞火山岩盆地南侧钾质侵入岩带的成因 总被引:1,自引:0,他引:1
庐枞火山岩盆地南侧的钾质侵入岩带由正长岩-石英正长岩-正长花岗岩组成,以石英正长岩为主。它们的形成时间介于123"130 Ma之间,峰值约为126 Ma,其中正长岩和石英正长岩的形成时间稍早,而正长花岗岩的形成时间略晚。整个钾质侵入岩带的侵位时间晚于庐枞盆地内的橄榄玄粗质火山作用约4"7 Ma,也是长江中下游地区除最东段的宁镇地区外中生代最晚的岩浆活动产物之一。地球化学上,该钾质侵入岩带以高钾、富碱、富集Rb、Th、U、K等强不相容元素和轻稀土元素、亏损高场强元素Nb、Ta和Ti为特征。它们的母岩浆主要是由富集型上地幔部分熔融形成的,从正长岩经石英正长岩到正长花岗岩的演化主要受矿物的分离结晶作用控制,地壳物质同化所起的影响不大。但与同样来自富集型上地幔部分熔融的庐枞盆地内火山杂岩的母岩浆相比,前者的母岩浆来源深度可能更大些或其中包含了更多来自软流圈地幔的组分。两者的演化路径也完全不同,钾质侵入岩带的母岩浆除经历过高压下的分离结晶作用外,晚期在低压下还经历过长石为主,可能还有黑云母的分离结晶,甚至上地壳物质一定程度的混染作用;而盆地内火山杂岩的母岩浆低压下矿物的分离结晶作用及上地壳物质的混染都不明显。庐枞盆地南缘的富钾侵入岩与盆地内的火山杂岩一样,地球化学上都具有明显的大陆弧的特征,暗示它们的岩浆源区可能形成于俯冲带环境,意味着扬子地块北缘先前(推测为古元古代晚期)曾发生过俯冲作用,上地幔的交代富集可能就与这次的俯冲作用有关。 相似文献
109.
《Chemie der Erde / Geochemistry》2016,76(4):567-578
Kajan subvolcanic rocks in the Urumieh–Dokhtar magmatic arc (UDMA), Central Iran, form a Late Miocene-Pliocene shallow-level intrusion. These subvolcanics correspond to a variety of intermediate and felsic rocks, comprising quartz diorite, quartz monzodiorite, tonalite and granite. These lithologies are medium-K calc-alkaline, with SiO2 (wt.%) varying from 52% (wt.%) to 75 (wt.%). The major element chemical data also show that MgO, CaO, TiO2, P2O5, MnO, Al2O3 and Fe2O3 define linear trends with negative slopes against SiO2, whilst Na2O and K2O are positively correlated with silica. Contents of incompatible trace elements (e.g. Ba, Rb, Nb, La and Zr) become higher with increasing SiO2, whereas Sr shows an opposite behaviour. Chondrite-normalized multi-element patterns show enrichment in LILE relative to HFSE and troughs in Nb, P and Ti. These observations are typical of subduction related magmas that formed in an active continental margin. The Kajan rocks show a strong affinity with calc-alkaline arc magmas, confirmed by REE fractionation (LaN/YbN = 4.5–6.4) with moderate HREE fractionation (SmN/YbN = 1.08–1.57). The negative Eu anomaly (Eu/Eu* <1), the low to moderate Sr content (< 400 ppm) and the Dy/Yb values reflect plagioclase and hornblende (+- clinopyroxene) fractionation from a calc-alkaline melt Whole–rock Sr and Nd isotope analyses show that the 87Sr/86Sr initial ratios vary from 0.704432 to 0.705989, and the 143Nd/144Nd initial ratios go from 0.512722 to 0.512813. All the studied samples have similar Sr-Nd isotopes, indicating an origin from a similar source, with granite samples that has more radiogenic Sr and low radiogenic Nd isotopes, suggesting a minor interaction with upper crust during magma ascent. The Kajan subvolcanic rocks plot within the depleted mantle quadrant of the conventional Sr-Nd isotope diagram, a compositional region corresponding to mantle-derived igneous rocks. 相似文献
110.
早古生代古亚洲洋俯冲记录:来自东天山卡拉塔格高镁安山岩的年代学、地球化学证据 总被引:9,自引:4,他引:5
吐哈盆地南缘荒草坡群大柳沟组火山岩出露于大草滩断裂以北的彩霞山、土屋铜矿北和卡拉塔格地区。该组火山岩主要为基性、中酸性熔岩及火山碎屑岩组合。LA-ICP MS锆石U-Pb分析获得安山岩和英安岩的年龄分别为434.8±3.8Ma和438.4±4.9Ma,表明大柳沟组火山岩形成于早志留世。安山岩Si O2含量为54.35%~60.70%;Al2O3含量为11.8%~16.3%,Mg O含量为4.94%~8.27%,Ti O2含量为0.38%~0.52%,Na2O和K2O的含量分别为0.50%~3.83%和0.08%~1.26%,铝饱和指数(A/CNK)为0.77~1.37,低ΣREE(43×10-6~70×10-6),为具有亏损源区特征的高镁安山岩。英安岩较安山岩Si O2含量高(63.74%~75.35%),具有相似的Al2O3(12.3%~16.0%%)和Ti O2(0.32%~0.52%)含量;Na2O和K2O含量分别为2.01%~5.53%和0.16%~2.19%,ΣREE含量较安山岩略高(61×10-6~84×10-6),铝饱和指数(A/CNK)为0.77~5.74。安山岩和英安岩均轻重稀土分异明显,具有中等的Eu负异常;富集大离子亲石元素(LILE),亏损高场强元素(HFSE),具有明显的Nb-Ta-Ti负异常。相似的岩石地球化学特征表明安山岩和英安岩可能为同源岩浆,英安岩是安山质岩浆经过角闪石等矿物结晶分异作用形成的,安山岩的母岩岩浆很可能来自亏损大洋岩石圈地幔。基于该组岩石组合、地球化学特征和区域地质资料,推测研究区高镁安山岩可能形成于洋内弧环境,这表明东天山吐哈盆地南缘卡拉塔格地区在早古生代已经存在古亚洲洋的俯冲。 相似文献