全文获取类型
收费全文 | 1054篇 |
免费 | 28篇 |
国内免费 | 24篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 84篇 |
地球物理 | 240篇 |
地质学 | 254篇 |
海洋学 | 222篇 |
天文学 | 183篇 |
综合类 | 12篇 |
自然地理 | 92篇 |
出版年
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 16篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 23篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 36篇 |
2013年 | 76篇 |
2012年 | 42篇 |
2011年 | 46篇 |
2010年 | 53篇 |
2009年 | 46篇 |
2008年 | 48篇 |
2007年 | 49篇 |
2006年 | 39篇 |
2005年 | 30篇 |
2004年 | 27篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 21篇 |
2000年 | 29篇 |
1999年 | 25篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 17篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1915年 | 6篇 |
1907年 | 7篇 |
排序方式: 共有1106条查询结果,搜索用时 31 毫秒
51.
52.
53.
54.
55.
56.
Jong-Hyeob Kim Seung Hyeon Kim Young Kyun Kim Kun-Seop Lee 《Ocean Science Journal》2016,51(4):635-645
Seagrasses require a large amount of nutrient assimilation to support high levels of production, and thus nutrient limitation for growth often occurs in seagrass habitats. Seagrasses can take up nutrients from both the water column and sediments. However, since seagrasses inhabiting in the intertidal zones are exposed to the air during low tide, the intertidal species may exhibit significantly different carbon (C) and nitrogen (N) dynamics compared to the subtidal species. To examine C and N dynamics of the intertidal seagrass, Zostera japonica, C and N content and stable isotope ratios of above- and below-ground tissues were measured monthly at the three intertidal zones in Koje Bay on the southern coast of Korea. The C and N content and stable isotope (δ13C and δ15N) ratios of seagrass tissues exhibited significant seasonal variations. Both leaf and rhizome C content were not significantly correlated with productivity. Leaf δ13C values usually exhibited negative correlations with leaf productivity. These results of tissue C content and δ13C values suggest that photosynthesis of Z. japonica in the study site was not limited by inorganic C supply, and sufficient inorganic C was provided from the atmosphere. The tissue N content usually exhibited negative correlations with leaf productivity except at the upper intertidal zone, suggesting that Z. japonica growth was probably limited by N availability during high growing season. In the upper intertidal zone, no correlations between leaf productivity and tissue elemental content and stable isotope ratios were observed due to the severely suppressed growth caused by strong desiccation stress. 相似文献
57.
Kyoung-nam Jo Kyung Sik Woo Hyoun Soo Lim Hai Cheng R. Lawrence Edwards Yongjin Wang Xiuyang Jiang Ryeon Kim Jae Il Lee Ho Il Yoon Kyu-Cheul Yoo 《Quaternary Science Reviews》2011,30(9-10):1218-1231
Textural and stable isotopic records from the absolute-dated stalagmite of the Daeya Cave (DY-1) provide new insights into the climatic evolution of the Korean Peninsula during the Holocene and Eemian climatic optima. The stalagmite yielded ages of 8572 ± 227 to 5907 ± 158 and 1,23,456 ± 535 to 1,19,837 ± 1089 years, which coincide with the Holocene and Eemian climatic optima, respectively. The stalagmite’s δ13C record closely resembles previously reported Chinese speleothem δ18O data. Thus it can be suggested that textural and geochemical results of the DY-1 reflect East Asian monsoon intensity, which is forced by summer insolation patterns in the northern hemisphere. Lighter carbon isotopic compositions, well-developed fibrous calcite crystals, and their relatively faster growth rate in the stalagmite sample are interpreted to reflect the warmest and wettest climate conditions of the Holocene and Eemian interglacials. Both climatic optima took place when insolation was decreasing from its maximum level, temperature in Greenland was highest, and sea level approached its maximum level. These climatic optima also coincide with decreasing Antarctic temperatures. Compared the DY-1 data to other proxies, it is suggested that the Holocene and Eemian climatic optima developed through a balance among boreal insolation, monsoon intensity, and sea level (also continental ice volume), which are the main climatic forcing factors in the northern hemisphere. These trends also follow the bi-polar seesaw mechanism as previously described. 相似文献
58.
Marie Ekström Natasha Kuruppu Robert L. Wilby Hayley J. Fowler Francis H.S. Chiew Suraje Dessai William J. Young 《Global Environmental Change》2013,23(1):115-129
Previous climate risk assessments provide important methodological insights into how to derive tractable research questions and the appropriate use of data under uncertainty, as well as identifying steps that benefit from stakeholder involvement. Here we propose the use of a framework for the systematic and objective exploration of climate risk assessments. The matrix facilitates a breakdown of information about aim and context, main results, methodological choices, stakeholder involvement, sources and characteristics of uncertainties and overall weaknesses. We then apply the matrix to three risk assessments in the water sector to explore some methodological strengths and weaknesses of approaches strongly linked to climate model outputs (top-down) versus those that originate from local knowledge of climate exposures (bottom-up), and demonstrate that closer integration with social and physical sciences is more likely to yield robust climate risk assessments. 相似文献
59.
Abstract Thermal convection in a vertically-mounted, rotating annulus of a particular design proposed by Davies and Walin (1977) is investigated. The annulus used in the present study differs from the conventional type in some important aspects: the sidewalls are finitely conducting, and the thermal conductance of the sidewalls is height-dependent. The theoretical model due to Davies and Walin is briefly recounted. The present study aims to verify the theoretical model; we have acquired numerical solutions to the governing Navier-Stokes equations. The numerical results are supportive of the theoretical contentions. The near-linear dependence of the isothermal slope on the parameter D, which is a function of Ω and ΔT, is corroborated within reasonable limits. New data on the vertical and radial structures of the meridional and azimuthal flows are presented. The numerical results also confirm that the shape of the sidewall thickness has a substantial influence on the meridional flow patterns. In the bulk of the interior flow field, the dominant azimuthal flow field and the temperature field are linked by the thermal wind relation. 相似文献
60.
Basalt at Sassafras was erupted in the Middle Eocene. The K‐Ar ages average 45.3 ± 4.9 Ma on whole rock and 48.4 ± 1.9 Ma on plagioclase. The basalt is not limited to a plateau capping, but extends 150 m down into adjacent valleys. Comparison with nearby Eocene basalts shows that there was in excess of 250 m of local relief in the central Shoalhaven valley by the Early Tertiary. The basalts were extruded at high elevation, and denudation of the coastal margin of the upland was already well advanced. Post‐basaltic denudation has been very slow, and the Early Tertiary landscape is well preserved. 相似文献