全文获取类型
收费全文 | 917篇 |
免费 | 64篇 |
国内免费 | 109篇 |
出版年
2024年 | 4篇 |
2023年 | 29篇 |
2022年 | 53篇 |
2021年 | 26篇 |
2020年 | 35篇 |
2019年 | 42篇 |
2018年 | 29篇 |
2017年 | 32篇 |
2016年 | 50篇 |
2015年 | 70篇 |
2014年 | 101篇 |
2013年 | 131篇 |
2012年 | 63篇 |
2011年 | 79篇 |
2010年 | 34篇 |
2009年 | 19篇 |
2008年 | 31篇 |
2007年 | 33篇 |
2006年 | 22篇 |
2005年 | 18篇 |
2004年 | 20篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 29篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有1090条查询结果,搜索用时 15 毫秒
201.
202.
Ki Wan Nam Christine A. Maggs Lynne McIvor Michael J. Stanhope 《Journal of phycology》2000,36(4):759-772
Two species of Osmundea Stackhouse (Rhodomelaceae, Rhodophyta) that occur in Atlantic Europe have been confused under the names Osmundea ramosissima (Oeder) Athanasiadis and Osmundea truncata (Kützing) Nam et Maggs, regarded until now as a synonym of O. ramosissima. An epitype from its type locality (Stavanger, Norway) is selected for Osmundea ramosissima Athanasiadis, recognized here as a valid name for Fucus ramosissimus Oeder, nom. illeg. Details of vegetative and reproductive morphology of O. ramosissima are reported, based on material from France, the British Isles, and Helgoland. Osmundea ramosissima resembles other species of Osmundea in its vegetative axial segments with two pericentral cells and one trichoblast, spermatangial development from apical and epidermal cells (filament type), the formation of five pericentral cells in the procarp‐bearing segment of the female trichoblast, and tetrasporangial production from random epidermal cells. Among the species of Osmundea, O. ramosissima is most similar to O. truncata. Both species have discoid holdfasts, secondary pit connections between epidermal cells, and cup‐shaped spermatangial pits. They differ in that: (a) O. ramosissima lacks lenticular wall thickenings and refractive needle‐like inclusions in medullary cells, both of which are present in O. truncata; (b) O. ramosissima has branched spermatangial filaments that terminate in a cluster of several cells, whereas in O. truncata the unbranched spermatangial filaments have a single large terminal sterile cell; and (c) cystocarps of O. ramosissima lack protuberant ostioles but ostioles are remarkably protuberant in O. truncata. Phylogenetic analyses of rbcL sequences of Laurencia obtusa (Hudson) Lamouroux and all five Atlantic European species of Osmundea, including the type species, strongly support the generic status of Osmundea. Osmundea ramosissima and O. truncata are closely related (5.2% sequence divergence) and form a well‐supported clade sister to a clade consisting of O. pinnatifida (Hudson) Stackhouse, O. osmunda Stackhouse and O. hybrida (A. P. de Candolle) Nam. The formation of secondary pit connections between epidermal cells is a synapomorphy for the O. ramosissima+O. truncata clade. The close relationship between species with cup‐shaped spermatangial pits (Osmundea hybrida) and urn‐shaped pits (Osmundea pinnatifida and Osmundea osmunda) shows that spermatangial pit shape is not an important phylogenetic character. Parsimony analysis of a morphological data set also supports the genus Osmundea but conflicts with the molecular trees in infrageneric relationships, placing O. hybrida basal within the Osmundea clade and grouping O. osmunda and O. pinnatifida but not O. truncata and O. ramosissima. A key to Osmundea species is presented. 相似文献
203.
T. Moura I. Figueiredo† P. BordaloMachado† C. Almeida† L. S. Gordo‡ 《Journal of fish biology》2005,67(3):742-751
A new chimaerid species closely related to Hydrolagus pallidus is described from 13 specimens captured on the Portuguese continental slope (north‐east Atlantic) by commercial longliners at depths of c . 1600 m. The new species is large‐bodied with a rose to light brown body colouration. Hydrolagus lusitanicus n.sp. presents a combination of external morphological characters that allow it to be clearly differentiated from its congeners, in particular, the ratios of pectoral fin length: pectoral fin width and pelvic fin length: pelvic fin width; in having a serrated posterior edge of the dorsal spine; a high number of ridges in the dental plates. Additionally in males, there are differences on the shape and number of hooks in the frontal tenacula, on the number of spines in the prepelvic tenacula and on the length of the pectoral fin margin. 相似文献
204.
205.
基于“源-汇”理论的流域非点源污染控制景观格局调控框架——以厦门市马銮湾流域为例 总被引:2,自引:0,他引:2
基于“源-汇”理论对景观格局进行调控与优化是一种较为经济、有效的流域非点源污染控制新方法,目前尚处在探索阶段.在景观生态学及相关理论与前人已有研究的基础上,以流域整体为对象,从2个层次构建基于“源-汇”理论的流域非点源污染控制景观格局调控框架: 1)流域层次:在分析流域“源-汇”景观合理的基本组合与空间布局方式的基础上,建立了流域景观格局整体调控与优化方法;2)景观斑块类型层次:将关键“源”景观作为重点调控与优化对象,建立了包含景观单位面积污染负荷、景观坡度、起传输作用的狭长“源”景观、临河“源”景观单位岸线长度污染负荷等4项关键“源”景观识别准则,并遵循镶嵌“汇”景观、局部增补带型“汇”景观、提高原有“汇”景观消纳污染物的能力等3项调控与优化原则,针对农村地区与城区不同的关键“源”景观类型,制定了9类调控与优化方法.最后将该框架应用到厦门市马銮湾流域,基于GIS平台及研究区遥感图像与数字高程模型,制定了马銮湾流域景观格局整体调控与优化模式及3个片区关键“源”景观调控与优化方案. 相似文献
207.
A new species of Docosia Winnertz from Central Europe,with DNA barcoding based on four gene markers (Diptera,Mycetophilidae) 总被引:1,自引:0,他引:1
A new species of Docosia Winnertz, Docosia
dentata
sp. n., is described and illustrated, based on a single male specimen collected in Muránska planina National Park in Central Slovakia. DNA sequences (COI, COII, CytB, and ITS2) are included and compared for 13 species of Docosia. There was found only little congruence between the molecular results and previous scarce data about interspecific relationships based on morphology. The COI and CytB gene markers showed the highest interspecific gene distances while ITS2 showed the lowest ones. An updated key to the 23 Central European species of Docosia is also presented. 相似文献
208.
Stephen D. Cairns 《ZooKeys》2016,(562):1-48
The transversely-dividing flabellids consist of five genera (Truncatoflabellum, Placotrochides, Blastotrochus, Placotrochus, and Falcatoflabellum) and 45 species. A dichotomous key is provided for these five genera as well as the species of the genus Truncatoflabellum and Placotrochides, the other three genera being monotypic. A tabular key is also provided for the 38 species of Truncatoflabellum. Two new combinations are suggested (Truncatoflabellum
gambierense and Truncatoflabellum
sphenodeum) and two new species are described (Truncatoflabellum
duncani and Truncatoflabellum
mozambiquensis). All but one species are illustrated and accompanied by their known distribution and a guide to the pertinent literature for the species. New records of 19 of the 45 species are listed. The transversely-dividing flabellids range from the Middle Eocene to the Recent at depths of 2–3010 m, and constitute 60% of the 65 known extant species of transversely-dividing Scleractinia. 相似文献
209.
210.
sandflyDST: a dynamic web‐based decision support tool for the morphological identification of sandflies present in Anatolia and mainland Europe,and user study 下载免费PDF全文
G. KARAKÜLAH M. KARAKUŞ A. SUNER S. DEMİR S. K. ARSERİM S. TÖZ Y. ÖZBEL 《Medical and veterinary entomology》2016,30(3):321-329
Species identification of sandflies is mainly performed according to morphological characters using classical written identification keys. This study introduces a new web‐based decision support tool (sandflyDST) for guiding the morphological identification of sandfly species present in Anatolia and mainland Europe and classified in the Phlebotomus and Sergentomyia genera (both: Diptera: Psychodidae). The current version of the tool consists of 111 questions and 36 drawings obtained from classical written keys, and 107 photographs for the quick and easy identification of 26 species of the genus Phlebotomus and four species of the genus Sergentomyia. The tool guides users through a decision tree using yes/no questions about the morphological characters of the specimen. The tool was applied by 30 individuals, who then completed study questionnaires. The results of subsequent analyses indicated that the usability () and users' level of appreciation (86.6%) of the tool were quite high; almost all of the participants considered recommending the tool to others. The tool may also be useful in training new entomologists and maintaining their level of expertise. This is a dynamic tool and can be improved or upgraded according to feedback. The tool is now available online at http://parasitology.ege.edu.tr/sandflyDST/index.php . 相似文献