全文获取类型
收费全文 | 1742篇 |
免费 | 141篇 |
国内免费 | 323篇 |
专业分类
测绘学 | 42篇 |
大气科学 | 26篇 |
地球物理 | 337篇 |
地质学 | 187篇 |
海洋学 | 859篇 |
综合类 | 103篇 |
自然地理 | 652篇 |
出版年
2024年 | 11篇 |
2023年 | 47篇 |
2022年 | 104篇 |
2021年 | 116篇 |
2020年 | 109篇 |
2019年 | 107篇 |
2018年 | 86篇 |
2017年 | 107篇 |
2016年 | 91篇 |
2015年 | 96篇 |
2014年 | 118篇 |
2013年 | 124篇 |
2012年 | 100篇 |
2011年 | 109篇 |
2010年 | 84篇 |
2009年 | 78篇 |
2008年 | 83篇 |
2007年 | 85篇 |
2006年 | 75篇 |
2005年 | 71篇 |
2004年 | 51篇 |
2003年 | 49篇 |
2002年 | 34篇 |
2001年 | 33篇 |
2000年 | 33篇 |
1999年 | 35篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 1篇 |
排序方式: 共有2206条查询结果,搜索用时 406 毫秒
901.
人为干扰对岩礁潮间带无脊椎动物群落结构的影响 总被引:1,自引:0,他引:1
对烟台海域 6个岩礁潮间带生态学统的无脊椎动物群落的研究发现 ,东方小藤壶( Chthamallus challengeri )为第一优势种。其主要优势种——密鳞牡蛎 ( Ostrea denselamellosa )、短滨螺 ( Littorina brevicula)、紫贻贝 ( Mytilus edulis)和常见种——笠贝 ( Patelloida spp.)、红条毛腹石鳖( Acanthochiton rubrolineatus)、沙参 ( Nereisspp.)、海葵 ( Anthopleura midori )在群落中的优势地位和功能有明显的区别 ,尽管 6个岩礁潮间带群落的区系成分相近。对基于 RIV、RB和 RD的优势度曲线研究发现 ,基于 RIV和 RB的优势度曲线更适合于表示和描述受人为干扰和污染的潮间带无脊椎动物群落的结构和多样性变化。研究发现 ,6个潮间带的无脊椎动物群落皆受到不同程度的干扰 ,而养马岛和芝罘岛所受的干扰最轻。 6个岩礁潮间带的群落多样性序列依次为 :芝罘岛、养马岛、石沟屯、烟台山、玉岱山、月老湾。不同岩礁潮间带群落的种类组成和结构差异主要由来自采集和旅游者的干扰 ,养殖和生活污水造成的海水富营养化所致 相似文献
902.
Abstract. Along the vertical cliff of Romito (Leghorn, Italy) 97 polychaete species were found from 0 to 6 m depth. Three depth related communities could be identified by trends in structural parameters (abundance, number of species, and diversity), by changes in species composition, and by the distribution of ecological and trophic groups. Such a zonation is consistent with the principal models proposed for the Méditerranean and seems mainly related to algal conditioning of the substrate. 相似文献
903.
EcologicalstudyonOstracodainthecentralSouthChinaSea¥ChenRuixiangandLinJinhong(ThirdInstituteofOceanograply,StateOceanicAdmini... 相似文献
904.
Abstract. The polychaete fauna of the subtidal in the médiolittoral and the infralittoral hard bottom zones of the Balearic Islands at depths from 0 to 40m contained 220 species. Five different polychaete communities could be identified by changes in abundance, species richness, species composition, diversity, and trophic structure. In the very clear waters of these islands the infralittoral zone extends to a depth of 40 m and allows us to investigate whether former proposed models of polychaete distribution can be extended to this particular situation. 相似文献
905.
Abstract. Distribution patterns of epiphytic hydroids of seagrass ( Posidonia occanica and Cymodocea nodosa ) beds were studied in the 'Stagnone', a moderately hypcrhaline lagoon in Sicily. The role of water movement in determining the spatial and temporal zonation of epiphytic hydroids and their morpho-physiological variations is evaluated. Remarks on systematics arc also included. 相似文献
906.
长江口中肋骨条藻赤潮发生全过程调查报告
──浮游植物群落结构及细胞形态研究
总被引:6,自引:0,他引:6于1990年6月在长江口赤潮多发区定点观测到一次中肋骨条藻赤潮发生的全过程,对中肋骨条藻赤潮发生过程中浮游植物群落结构的变动及细胞形态的变化进行研究。结果表明,(1)中肋骨条藻赤潮发生前,水体中甲藻数量多于硅藻;赤潮发生后,中肋骨条藻增殖,逐渐成为主要优势种,硅藻在数量上超过了甲藻;浮游植物种类丰度指数的大小能较好地反映赤潮发生的各个阶段。(2)赤潮发生过程中,中肋骨条藻细胞增殖率次序为:发展阶段>维持阶段>起始阶段。(3)在赤潮发生的维持阶段后期和消亡阶段,有5%-7.8%的中肋骨条藻形成休眠孢子,一个中肋骨条藻细胞仅形成一个休眠孢子,且同一个中肋骨条藻群体链上的所有细胞形成休眠孢子是同步的。 相似文献
907.
908.
Amanda E. Valois Juliet R. Milne Mark W. Heath Rob J. Davies-Colley Emily Martin Rebecca Stott 《新西兰海洋与淡水研究杂志》2020,54(2):200-217
ABSTRACT Water is an important component of many recreational opportunities and New Zealand invests significant resources in recreational water quality (RWQ) monitoring to assess risks to public health. However, monitoring primarily focuses on microbiological hazards and RWQ is considerably broader than this. The goal of this study was to take a comprehensive approach to evaluating RWQ while exploring the potential for greater public involvement in monitoring. A popular river swimming site was co-monitored weekly by volunteers and a council field officer. The attributes monitored–water temperature, visual clarity, benthic cyanobacteria and filamentous periphyton cover, E. coli and rubbish–were identified from a volunteer workshop. There was good concordance between volunteer and council data suggesting that volunteer measurements can be considered reliable. This highlights the potential for volunteers, with professional support, including training and quality assurance, to extend council RWQ surveillance to additional monitoring sites while improving public engagement on water management. 相似文献
909.
910.
Effects of Soft Corals on Scleractinian Coral Recruitment. II: Allelopathy, Spat Survivorship and Reef Community Structure 总被引:1,自引:0,他引:1
Abstract. Two field experiments were performed on the Great Barrier Reef, Australia, at Orpheus Island and Lizard Island, respectively, to investigate the effects of allelopathic soft corals on survivorship and community structure of scleractinian coral spat. Ceramic tiles were placed around the allelopathic soft corals Sinularia flexibilis (Quoy & Gaimard 1833) and Sarcophyton glaucum (Quoy & Gaimard 1833), and controls. One control consisted of settlement plates surrounding a scleractinian coral (non‐allelopathic planktivore); another control had no adult soft or scleractinian coral present. The experimental soft corals affected the recruitment of various taxonomic groups of coral spat differentially, as evidenced by the diversity of coral spat settling in treatments and controls. At Orpheus Island (O.I., n = 1038 spat) and Lizard Island (L.I., n = 7032 spat), there were significant differences between recruitment success of the two dominant coral taxa, Pocilloporidae (O.I., 61.4 %; L.I., 20.5 %) and Acroporidae (O.I., 33.7 %; L.I., 53 %). Settlement plates exposed to Sinularia flexibilis at either site had the lowest proportion of acroporid recruits. Diversity indices (Shannon‐Wiener Indices) varied significantly between treatments at both Orpheus and Lizard Islands. This appears to be due to selective inhibition of acroporid spat by Sinularia flexibilis at both sites. Growth of coral spat was higher on settlement plates in the presence of Sarcophyton at Lizard Island. Settlement of most associated epibiota was generally inhibited under these conditions. Coral spat survivorship was highest in the presence of Sinularia at Orpheus Island; at Lizard Island, this was the case with the Sarcophyton treatment. Higher survivorship, and in some cases growth, of coral spat near soft corals was apparently due to reduced competition for space between spat and associated epibiota. This hypothesis is supported by the results of a sister experiment where a coating of Sinularia flexibilis extract on settlement tiles significantly decreased fouling by sessile epibiota. Soft corals have an allelopathic effect on recruitment and early development of scleractinian corals and, consequently, on early coral reef community succession. 相似文献