全文获取类型
收费全文 | 958篇 |
免费 | 302篇 |
国内免费 | 1152篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 128篇 |
地球物理 | 172篇 |
地质学 | 1825篇 |
海洋学 | 99篇 |
天文学 | 4篇 |
综合类 | 145篇 |
自然地理 | 17篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 10篇 |
2015年 | 24篇 |
2014年 | 13篇 |
2013年 | 22篇 |
2012年 | 14篇 |
2011年 | 142篇 |
2010年 | 65篇 |
2009年 | 127篇 |
2008年 | 49篇 |
2007年 | 102篇 |
2006年 | 198篇 |
2005年 | 250篇 |
2004年 | 297篇 |
2003年 | 191篇 |
2002年 | 108篇 |
2001年 | 131篇 |
2000年 | 93篇 |
1999年 | 52篇 |
1998年 | 66篇 |
1997年 | 49篇 |
1996年 | 21篇 |
1995年 | 23篇 |
1994年 | 17篇 |
1993年 | 83篇 |
1992年 | 65篇 |
1991年 | 20篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1983年 | 2篇 |
1950年 | 8篇 |
1944年 | 2篇 |
1943年 | 6篇 |
1940年 | 8篇 |
1937年 | 12篇 |
1934年 | 9篇 |
1933年 | 11篇 |
1928年 | 8篇 |
1927年 | 6篇 |
1926年 | 2篇 |
1924年 | 5篇 |
排序方式: 共有2412条查询结果,搜索用时 15 毫秒
1.
广东河源盆地蛋化石 总被引:3,自引:0,他引:3
河源盆地沉积了白垩系-古近系,笔者将这套地层划分为3个岩石地层单位,新建仙塘组和东源组,沿用格岭组。在河源除发现恐龙骨骼、恐龙脚印、龟鳖化石外,于白垩系东源组中还产有大量蛋化石。该组蛋化石的分布,下部以圆形蛋为主,中-上部多见长形蛋。报道了三王坝村副圆形蛋(新种)Paraspheroolithus sanwangbacunensis Fang sp.nov.、风光村树枝蛋(新种)Dendroolithus fengguangcunensis Fang sp.nov.和瑶屯巨形蛋Macroolithus yaotunensis、长形长形蛋Elongatoolithus elongates。 相似文献
2.
现代抗震设计理论的发展过程 总被引:18,自引:0,他引:18
介绍了现代抗震设计理论的发展过程,基于性态的抗震设计理论的提出背景、发展情况及研究内容;详细介绍了基于性态的抗震设计理论的抗震设防方法;指出了基于性态的抗震设计理论与传统抗震设计理论的主要区别及特点。 相似文献
3.
4.
略阳煎茶岭铜镍硫化物矿床Re—Os同位素年龄及其地质意义 总被引:12,自引:0,他引:12
采用矿石Re-Os同位素方法对陕西省煎茶岭硫化镍矿床矿石进行了成矿年代学研究,获得了878士27 Ma(1σ)的等时线年龄,首次厘定了该矿床成矿时代为新元古代,成岩成矿基本同时.通过对878 Ma硫化镍矿石初始Re-Os同位素体系的γOs计算和Re/Os值分析表明,其yOs和Re/Os值变化范围大,深部条带状矿石的Re/Os值仅为0.05,yOs为-6.70;块状矿石的Re/Os值范围为4.24~24.43,γOs为-15.37~+280.65,说明成矿过程中有壳源物质的混染;两件样品的γOs为负值(-15.37,-6.70),可能指示其超镁铁质岩浆来源于Re亏损地幔.煎茶岭超基性岩体年龄及其镍矿石的Re-Os等时线年龄与扬子克拉通北缘火山岩浆活动时间相对应,它们是扬子克拉通西北缘晋宁期构造岩浆成矿作用的产物. 相似文献
5.
The Discovery of Phlogopite Exsolution Lamellae in Garnets of Eclogite Inclusions, Liaoning Province
Zhou Xiuzhong Institute of Mineral Deposits Chinese Academy of Geological Sciences Beijing Liu Xinzhu 《《地质学报》英文版》1997,71(1):33-42
In No. 50 kimberlite pipe of Fuxian County, Liaoning Province, an eclogite inclusion(nodule), which is extremely rare in kimberlites, was discovered and phlogopite exsolutionlamellae were found in garnets of the inclusion. Microscopic, TEM and energy spectral observa-tions and studies confirmed that these lamellae are phlogopite. They are colourless and acicularin section, generally 0.5-5μm in width and 10-100μm in length. Nevertheless, fine lamellae,0.05-0.1μm wide and 1-2μm long, are also well developed. Along [111] of the garnet, three setsof phlogopite lamellae show oriented arrangement approximately at angles of 60°-70°, indi-cating that these lamellae might be the product of exsolution from garnet as a result ofpressure-release when eclogite ascended from the relatively deep level to the relatively shallowlevel of the mantle. Tiny acicular exsolution minerals (or inclusions) are commonly found ingarnet and pyroxene in eclogite inclusions of kimberlites all over the world and it has been re-ported that the identified exsolution minerals include pyroxene and rutile. This is the first timethat phlogopite exsolution lamillae were found in eclogite inclusions in the world. 相似文献
6.
Mineralization Ages of the Jiapigou Gold Deposits,Jilin 总被引:1,自引:0,他引:1
Li Junjian Shen Baofeng Mao Debao Li Shuangbao Zhou Huifang Cheng Yuming Tianjin Institute of Geology Mineral Resources Chinese Academy of Geological Sciences Tianjin Nonferrous Metal Geological Exploration Bureau Changchun Jilin 《《地质学报》英文版》1997,71(2):180-188
The Jiapigou gold deposits are typical vein type deposits associated withArchaean greenstone belts in China. According to the crosscutting relationships between dykesand auriferous veins, single hydrothermal zircon U-Pb dating and quartz K-Ar,~(40)Ar-~(39)Ar andRb-Sr datings, the main mineralization stage of the Jiapigou deposit has been determined to be2469-2475 Ma, while mineralization superimposition on the gold deposit occurred in1800-2000 Ma and 130-272 Ma. They form a mineralization framework of one oldermetallogenic epoch (Late Archaean-Early Proterozoic) and one younger metallogenic epoch(Mesozoic) of gold deposits in Archaean greenstone belts in China. 相似文献
7.
鄂尔多斯盆地的西北部、东北部和南部三个区域现今大地热流平均值分别为56.3、67.3和65.3mW/m^2,对应的生态环境格局也有明显的差异。研究表明,大地热流每增加4~5mW/m^2可使年均地表温度升高约l℃,使最低月均地表温度升高2。C以上。鄂尔多斯盆地东北部的平均大地热流比西北部高出11mW/m^2,东北部年均地表温度可能比西北部高出2~3℃,其最低月均地表温度可能比西北部高出4~6℃。西北部的大地热流平均值已经低于维持地表生态系统延续所需大地热流的临界值(57mW/m^2),其自然生态系统整体上已经处于脆弱境地;东北部和南部的大地热流均大于57mW/m^2,自然生态系统均尚较稳健。东北部的沙漠化可能是风沙侵入的结果,其生态应该是可以恢复的。整个西北部作为一个整体看,72万年以前大地热流就已衰减到临界值以下,区域生态系统渐趋脆弱,开始整体上向荒漠化演变。 相似文献
8.
Late Paleozoic Fluid Systems and Their Ore-forming Effects in the Yuebei Basin, Northern Guangdong, China 总被引:1,自引:0,他引:1
DENG Jun YANG Liqiang SUN Zhongshi WANG Jianping WANG Qingfei CHENG Xueming ZHOU Yinghua State Key Laboratory of Geological Processes Mineral Resources China University of Geosciences Beijing Key Laboratory of Lithosphere Tectonics Lithoprobing Technology of the Ministry of Education China University of Geosciences Beijing School of Earth Sciences Jilin University Chuangchun Jilin 《《地质学报》英文版》2005,79(5):673-687
Based on detailed and systematic researches of the geology of ore deposits, fluid inclusions and isotope geochemistry etc., and regarding the Late Paleozoic fluid system of the Yuebei Basin as an integrated object in this paper, we have revealed the temporo-spatial evolution law of the basin's fluid system and discussed its ore-forming effects by simulating and analyzing the distribution of ore-forming elements, the fluid thermodynamics and dynamics of evolution processes of this basin. The results show that Late Paleozoic ore-forming fluid systems of the Yuebei Basin include four basic types as follows. (1) The sea floor volcanic-exhalation system developed during the rapid basin slip-extension stage in the Mid-Late Devonian, which affected the Dabaoshan region. It thus formed the Dabaoshan-type Cu-Pb-Zn-Fe sea floor volcanic-exhalation sedimentary deposits. (2) The compaction fluid system developed during the stable spreading and thermal subsidence-compression stage of the basin in the Mid-Late Devonian. The range of its effects extended all over the whole basin. It resulted in filling-metasomatic deposits, such as the Hongyan-type pyrite deposits and pyrite sheet within the Fankou-type Cu-Pb-Zn-S deposits. (3) The hot water circulation system of sea floor developed during the stage of basin uplifting and micro-aulacogen from the late Late Carboniferous to Middle Carboniferous. The range of its effects covered the Fankou region. It thus formed MVT deposits, such as the main orebody of the Fankou-type Pb-Zn-S deposits. (4) The gravity fluid system developed during the stage of fold uplifting and the basin closed from Middle Triassic to Jurassic, forming groundwater hydrothermal deposits, e.g. the veinlet Pb-Zn-calcite orebodies of the Fankou-type Pb-Zn- S deposits. Migration and concentration of the ore-forming fluids were constrained by the state of temporo-spatial distribution of its fluid potential. Growth faults not only converged the fluids and drove them to move upwards, but also the fluids often crossed the faults to the edges of the basin at the bottom of these faults and the lithologic interfaces, and even migrated to the basin's edges from top to bottom along the faults, which may be one of the basic reasons for the stratabound deposits to cluster mainly along the contemporaneous faults on the inner border of the basin. The superposed mineralization resulting from the multi-stage activity of contemporaneous faults and ore-forming fluid systems in the basin may be one of the key factors for forming superlarge ore deposits. 相似文献
9.
Tectonic Evolution of the Himalayan Collision Belt 总被引:5,自引:0,他引:5
Cui Junwen Institute of Geology Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》1997,71(2):133-143
This paper discusses the tectonic divisions of the Himalayan collision belt anddeals with the tectonic evolution of the collision belt in the context of crustal accretion in thefront of the collision belt, deep diapirism and thermal-uplift extension and deep material flow-ing of the lithosphere-backflowing. Finally it proposes a model of the tectonic evolution-progressive intracontinental deformation model-of the Himalayan belt. 相似文献
10.
近10余年来,特别是2000年召开第三届地层会议后,中国年代地层研究得到很快发展。首先,在全国地层委员会主持下,经各断代工作组专家们的共同努力,编制完成了《中国区域年代地层(地质年代)表》,系统建立了从震旦系至第四系中共102个阶(其中包括52个陆相地层区的阶)和新建3个系级单位。从2001年开始,在中国地质调查局的大力支持下,由全国地层委员会主持,组织全国知名地质科研院所、高校和部分地质调查院的专家,围绕中国区域年代地层表,开展了系统的建阶研究。5年来,共涉及45个阶,9个界线层型和2个新建系及2个统级单位的研究,取得重要进展。先后已有4个全球界线层型(GSSPs)被国际地质科学联合会批准建立在中国,还有3~4个全球界线层型正待国际地质学科学联合会批准建立在中国,另有3~4个界线层型剖面有望争取成为全球的界线层型。其他研究所涉及到的阶、系、统等单位,也有明显进展,成熟度明显提高,为《中国区域年代地层(地质年代)表》的广泛应用奠定了重要基础。 相似文献