全文获取类型
收费全文 | 1210篇 |
免费 | 274篇 |
国内免费 | 705篇 |
专业分类
测绘学 | 35篇 |
大气科学 | 10篇 |
地球物理 | 150篇 |
地质学 | 1306篇 |
海洋学 | 553篇 |
天文学 | 13篇 |
综合类 | 50篇 |
自然地理 | 72篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 50篇 |
2021年 | 54篇 |
2020年 | 88篇 |
2019年 | 80篇 |
2018年 | 69篇 |
2017年 | 52篇 |
2016年 | 91篇 |
2015年 | 84篇 |
2014年 | 92篇 |
2013年 | 116篇 |
2012年 | 98篇 |
2011年 | 127篇 |
2010年 | 93篇 |
2009年 | 108篇 |
2008年 | 109篇 |
2007年 | 103篇 |
2006年 | 137篇 |
2005年 | 93篇 |
2004年 | 107篇 |
2003年 | 75篇 |
2002年 | 64篇 |
2001年 | 36篇 |
2000年 | 42篇 |
1999年 | 44篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 15篇 |
1994年 | 23篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有2189条查询结果,搜索用时 31 毫秒
51.
Biological structures as a source of habitat heterogeneity and biodiversity on the deep ocean margins 总被引:1,自引:0,他引:1
Lene Buhl-Mortensen Ann Vanreusel rew J. Gooday Lisa A. Levin Imants G. Priede Pål Buhl-Mortensen Hendrik Gheerardyn Nicola J. King & Maarten Raes 《Marine Ecology》2010,31(1):21-50
Biological structures exert a major influence on species diversity at both local and regional scales on deep continental margins. Some organisms use other species as substrates for attachment, shelter, feeding or parasitism, but there may also be mutual benefits from the association. Here, we highlight the structural attributes and biotic effects of the habitats that corals, sea pens, sponges and xenophyophores offer other organisms. The environmental setting of the biological structures influences their species composition. The importance of benthic species as substrates seems to increase with depth as the complexity of the surrounding geological substrate and food supply decline. There are marked differences in the degree of mutualistic relationships between habitat-forming taxa. This is especially evident for scleractinian corals, which have high numbers of facultative associates (commensals) and few obligate associates (mutualists), and gorgonians, with their few commensals and many obligate associates. Size, flexibility and architectural complexity of the habitat-forming organism are positively related to species diversity for both sessile and mobile species. This is mainly evident for commensal species sharing a facultative relationship with their host. Habitat complexity is enhanced by the architecture of biological structures, as well as by biological interactions. Colony morphology has a great influence on feeding efficiency for suspension feeders. Suspension feeding, habitat-forming organisms modify the environment to optimize their food uptake. This environmental advantage is also passed on to associated filter-feeding species. These effects are poorly understood but represent key points for understanding ecosystems and biodiversity on continental margins. In this paper we explore the contributions of organisms and the biotic structures they create (rather than physical modifications) to habitat heterogeneity and diversity on the deep continental margins. 相似文献
52.
The Maldives was severely hit by massive coral bleaching and subsequent mortality in 1998. The results of reef monitoring in the following years have supported contrasting views about their recovery potential, partly because of the scarcity of information on the situation before 1998. Quantitative data on coral assemblages collected in 1993 in the Rasfari region (North Malé Atoll) may provide a base-line for the evaluation of the present status of the Maldivian reefs. Five years before the 1998 mortality, most coral communities appeared to be similar, in terms of both coral cover and growth-form composition, to those described in 1958 and 1964, notwithstanding increased human pressure and local events such as minor bleaching episodes in 1987 and crown-of-thorns starfish (COTS) attacks in 1989. Three lessons can be learnt from these results to help to understand the present situation, some ten years after the 1998 mass mortality. First, Maldivian reefs proved in the past to be capable of maintaining flourishing coral life despite various disturbances. Second, four years had been sufficient for complete reef recovery after a (minor) bleaching event. Third, recovery after both COTS attack and bleaching follows a predictable path suggesting that the presence of a three-dimensional community structure, which should reduce post settlement mortality of coral recruits, is essential for rapid coral recovery. As coral recruitment remains high and large tabular Acropora colonies are now reappearing, it is expected that Maldivian reefs should return to their original condition within the next few years. 相似文献
53.
2009年3月,采用水下照相及摄像方法,对海南昌江沿岸海域的石珊瑚物种多样性、分布及覆盖度进行了调查.结合历史资料,共发现石珊瑚10科15属28种和1未定种.其中鹿角珊瑚属(Acropora)、角蜂巢珊瑚属(Favites)、叶状珊瑚属(Lobophyllia)等为优势类群,常见分布珊瑚种类有角孔珊瑚(Gonioporasp.)、标准蜂巢珊瑚(Favia speciosa)、五边角蜂巢珊瑚(Favites pentagona)、多孔鹿角珊瑚(Acropora millepora)、十字牡丹珊瑚(Pavona decussata)、伞房叶状珊瑚(Lobophyllia corymbosa)等.石珊瑚主要分布于海尾镇三联村以南海域,覆盖率最高为12%.本次调查在海南昌江沿岸海域记录的珊瑚种类数多于以前的记录,但少于海南南岸的三亚鹿回头,也少于北部的广西涠洲岛、广东徐闻、香港等海域,随着调查次数的增加,预计会有更多的种类被发现.该海域是北部湾珊瑚幼虫交流的中间过渡区,对珊瑚礁的保护与恢复具有重要意义. 相似文献
54.
55.
56.
为了有效地消除重力异常畸变对海洋重力测量的影响,得到高精度的海洋重力测量值,本文在小波理论分析的基础上,将小波分析应用到消除海洋重力异常畸变中。基于信号的奇异性分析理论和小波软阈值处理方法,提出一种小波联合软阈值处理方法;根据重力异常状态方程,分别采用小波软阈值处理方法和小波联合软阈值处理方法对重力异常畸变数据进行了仿真对比实验,理论分析和仿真实验表明:采用小波软阈值处理方法和小波联合软阈值处理方法并选用通用阈值选择规则都能在一定程度上消除海洋重力异常畸变,但在相同背景条件下,小波联合软阈值处理方法的性能优于小波软阈值处理方法。 相似文献
57.
58.
59.
雷州半岛灯楼角珊瑚礁海区的浮游植物 总被引:8,自引:2,他引:8
雷州半岛西南岸的珊瑚礁,是唯一的中国大陆沿岸现代珊瑚礁。根据2004年8月的调查资料研究分析了雷州半岛灯楼角珊瑚礁海区浮游植物的种类组成、生态类群和数量分布等,以期为珊瑚礁生态系的研究提供基础资料。结果显示:浮游植物共有108种(含变种和变型),其中硅藻门34属85种、甲藻门10属21种、蓝藻门1属2种,浮游植物的种数分布由近岸往远岸递增;浮游植物大致划分为近岸低盐类群、近海广布类群和外海高温高盐类群等3个生态类群;优势种有中肋骨条藻Skeletonemacostatum、菱形海线藻Thalassionemanitzschioides、奇异菱形藻Nitzschiaparadoxa等8种;多样性指数和均匀度平均值分别为3.448和0.655,总体分布比较均匀;浮游植物细胞总量平均值为93×104cells/m3,其中硅藻类占绝对优势,浮游植物分布不均匀,密集于灯楼角南面的A断面。 相似文献
60.