全文获取类型
收费全文 | 963篇 |
免费 | 202篇 |
国内免费 | 218篇 |
专业分类
测绘学 | 64篇 |
大气科学 | 163篇 |
地球物理 | 248篇 |
地质学 | 460篇 |
海洋学 | 187篇 |
天文学 | 9篇 |
综合类 | 91篇 |
自然地理 | 161篇 |
出版年
2024年 | 16篇 |
2023年 | 21篇 |
2022年 | 47篇 |
2021年 | 76篇 |
2020年 | 66篇 |
2019年 | 80篇 |
2018年 | 71篇 |
2017年 | 69篇 |
2016年 | 77篇 |
2015年 | 69篇 |
2014年 | 77篇 |
2013年 | 54篇 |
2012年 | 62篇 |
2011年 | 51篇 |
2010年 | 47篇 |
2009年 | 51篇 |
2008年 | 55篇 |
2007年 | 47篇 |
2006年 | 29篇 |
2005年 | 31篇 |
2004年 | 19篇 |
2003年 | 21篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 19篇 |
1999年 | 25篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 31篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有1383条查询结果,搜索用时 15 毫秒
851.
梳理1992—2018年中亚五国碳排放变化过程,运用碳排放库兹涅茨曲线模拟人均碳排放与人均国内生产总值(GDP)的关系,基于中亚五国人均GDP、工业增加值、研发投入、自华进口中间品和资本品的技术溢出存量等指标,构建面板数据固定效应模型以探究碳排放影响机制。结果表明:(1) 中亚五国碳排放先降后升,各国碳排放的变化率波动较大,其中哈萨克斯坦碳排放占中亚五国碳排放比重最大。(2) 就人均碳排放与人均GDP拟合的碳排放库兹涅茨曲线关系而言,哈萨克斯坦和土库曼斯坦表现为倒N型,乌兹别克斯坦、塔吉克斯坦、吉尔吉斯斯坦和中亚五国表现为N型。(3) 中亚五国自华进口额呈现较快的增长趋势,其中自华进口的中间品和资本品合计约占自华进口总额的3.920%~10.976%,中亚五国整体及各国中间品技术溢出存量均明显大于资本品技术溢出存量。(4) 在影响中亚五国碳排放的诸多因素中,人均GDP和工业增加值占GDP比重的回归系数显著为正,人均GDP、工业增加值占GDP比重每上升1%,碳排放分别增加0.337%和0.343%,研发投入、交互项LnZJit×LnSit(中间品技术溢出存量的自然对数×工业增加值占GDP比重的自然对数)的回归系数显著为负,研发投入每增加1%,碳排放可减少约0.432%,在降低因工业增加值占GDP比重上升导致的碳排放方面,中间品技术溢出存量的影响极小。 相似文献
852.
Liu Shaofeng Li Sitian Zhuang Xinguo Jiao Yangquan Lu ZongshengChina University of Geosciences Wuhan 《《地质学报》英文版》1996,70(3):233-245
Characteristics of deformation in the thrust belt and sequence stratigraphic framework in the foreland basin, structural features of the basin margin, and the episodic thrusting are studied in this paper by combining the eastern Qilian thrust belt and the Late Triassic foreland basin on the southwestern margin of Ordos. On this basis, a geological model and a mechanical model of coupling mechanism were established for the pair of thrust belt and foreland basin, and the subsidence and deposition process of the foreland basin were simulated on given parameters. 相似文献
853.
854.
855.
A shortage of water has limited the socio-economic development of the Heihe River Basin in northwestern China and has led to many ecological and economic problems. Only the development and application of integration tools can effectively represent the functionality of the watershed and aid in strategic decision making. In the framework of SME, modular and hierarchical model building can simplify the research work. According to the main ideas and key processes commonly used in distributed hydrological models, and combined with the spatial characteristics of the mountainous region of the Heihe River Basin, a unit hydrological model was developed using stella, which was an icon-based software package specifically designed for dynamic systems modeling, and an algorithm for spatial distribution in SME was introduced. This paper describes only the model structure and basic equations, whereas in the next paper, model calibration results using the data measured at meteorological stations, together with land use data and soil data, will be further introduced. 相似文献
856.
Xingxing Kuang Xin Luo Jiu Jimmy Jiao Sihai Liang Xiaolang Zhang Hailong Li Junguo Liu 《水文研究》2019,33(13):1835-1850
Characterization of stable isotope compositions (δ2H and δ18O) of surface water and groundwater in a catchment is critical for refining moisture sources and establishing modern isotope–elevation relationships for paleoelevation reconstructions. There is no consensus on the moisture sources of precipitation in the Yellow River source region during summer season. This study presents δ2H and δ18O data from 111 water samples collected from tributaries, mainstream, lakes, and groundwater across the Yellow River source region during summertime. Measured δ18O values of the tributaries range from ?13.5‰ to ?5.8‰ with an average of ?11.0‰. Measured δ18O values of the groundwater samples range from ?12.7‰ to ?10.5‰ with an average of ?11.9‰. The δ18O data of tributary waters display a northward increase of 1.66‰ per degree latitude. The δ18O data and d‐excess values imply that moisture sources of the Yellow River source region during summertime are mainly from the mixing of the Indian Summer Monsoon and the Westerlies, local water recycling, and subcloud evaporation. Analysis of tributary δ18O data from the Yellow River source region and streamwater and precipitation δ18O data from its surrounding areas leads to a best‐fit second‐order polynomial relationship between δ18O and elevation over a 4,600 m elevation range. A δ18O elevation gradient of ?1.6‰/km is also established using these data, and the gradient is in consistence with the δ18O elevation gradient of north and eastern plateau. Such relationships can be used for paleoelevation reconstructions in the Yellow River source region. 相似文献
857.
QIN Gan ZHANG Ping-yu JIAO Bin 《中国地理科学(英文版)》2006,16(2):154-159
1 INTRODUCTION Urban agglomeration researches originated from the concern about the city cluster in the developed areas of western countries. The modern researches have been extended to the specific areas. HALL (2001) summa- rized the generality and difference of urban metropoli- tans in Europe, and analyzed the spatial structure of dif- ferent areas. NAUDE and KRUGELL (2003) analyzed the spatial development of urban agglomeration in South Africa, and thought that the size of the p… 相似文献
858.
Wang Y.Jiao Y. 《大地构造与成矿学》2015,(1):139-152
The early Jurassic Dashipo-Heishantuo batholith in Beijing, which consists of the Dashipo hornblende-biotite syenite and Heishantuo granite, exposed in the western Yanshan orogenic belt, eastern North China Craton. The Dashipo syenite is magnesian potassic intermediate rock enriched in large ion lithophile elements such as Rb, Ba, Sr, Pb and LREE, and relatively depleted in high field strength elements such as Nb, Ta, U, Th, Zr, Hf as well as P and Ti, with εNd(t) values from -12.1 to -12.2 and ISr values of 0.70506-0.70464. The Heishantuo granite is magnesian peraluminous high K calc-alkaline, with an enrichment of large ion lithophile elements and radioactive elements such as Rb, Ba, Th, U and Pb, and a depletion of HREE and high field strength elements such as Nb, Ta, Zr and Hf as well as Sr, P and Ti, with εNd(t) values from -15.5 to -18.0 and ISr values of 0.70516-0.70593. The magma of the Dashipo syenite is produced by fractional crystallization of mantle-derived K-rich mafic magma under high pressure. The partial melting of the lower crust, which was heated and metasomatised by the mantle-derived magma, produced granitic magma that intruded into the unconsolidated Dashipo syenite to form the concentric batholith. The petrology and geochemistry of the Dashipo hornblende-biotite syenite indicate that the water weakening was important for the lithospheric destruction within the interior part of the North China Craton. Meanwhile, the partial melting related to the double-diffusion of energy and chemical composition between mantle-derived magma and crustal rocks was an important mechanism for the Mesozoic calc-alkaline felsic magmatism occurred in the interior of the North China Craton. ©, 2015, Science Press. All right reserved. 相似文献
859.
860.
海洋声场环境研究需要对不同深度的海洋声学环境要素进行同步测量,而感应耦合数据传输技术可实现多个单通道水声测量仪之间的同步采集和记录。文中阐述了感应耦合数据传输技术的特点及其在海洋声学环境同步测量中的应用,介绍了一种利用感应耦合数据传输技术实现数据同步测量的声学浮标系统,详细描述了系统的方案设计、结构组成及感应耦合部分的关键技术。实验水池测试表明,该系统工作稳定可靠,数据同步性好,具有良好的应用前景。 相似文献