全文获取类型
收费全文 | 6291篇 |
免费 | 130篇 |
国内免费 | 201篇 |
专业分类
系统科学 | 131篇 |
丛书文集 | 164篇 |
教育与普及 | 69篇 |
理论与方法论 | 86篇 |
现状及发展 | 28篇 |
综合类 | 5642篇 |
自然研究 | 502篇 |
出版年
2024年 | 18篇 |
2023年 | 29篇 |
2022年 | 57篇 |
2021年 | 66篇 |
2020年 | 73篇 |
2019年 | 73篇 |
2018年 | 65篇 |
2017年 | 93篇 |
2016年 | 80篇 |
2015年 | 148篇 |
2014年 | 322篇 |
2013年 | 224篇 |
2012年 | 743篇 |
2011年 | 431篇 |
2010年 | 360篇 |
2009年 | 366篇 |
2008年 | 372篇 |
2007年 | 564篇 |
2006年 | 416篇 |
2005年 | 335篇 |
2004年 | 266篇 |
2003年 | 268篇 |
2002年 | 238篇 |
2001年 | 198篇 |
2000年 | 149篇 |
1999年 | 100篇 |
1998年 | 75篇 |
1997年 | 93篇 |
1996年 | 56篇 |
1995年 | 58篇 |
1994年 | 57篇 |
1993年 | 63篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 22篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有6622条查询结果,搜索用时 15 毫秒
71.
《Journal of Natural History》2012,46(37-38):2391-2423
The present study raises the number of Ampelisca species recorded from the Brazilian coast from 18 to 21. The amphipod fauna of the Brazilian northeast coast is hardly known compared to that of the southeast coast. In this study, we describe three new species from the northeast coast: Ampelisca pseudobicarinata sp. nov., Ampelisca rocasensis sp. nov. and Ampelisca cristianae sp. nov, recorded previously as Ampelisca aff. lobata (Serejo et al. 2000). We also report a new record of Ampelisca burkei Barnard and Thomas, 1989. From the southeast coast a new species Ampelisca angraensis sp. nov. is described. An obscure species, Ampelisca soleata, which is very similar to Ampelisca brevisimulata, is herein redescribed and a neotype is designated. An updated key with all species of Ampelisca recorded from the Brazilian coast and comments on geographic distribution are given. 相似文献
72.
《Journal of Natural History》2012,46(21-22):1447-1475
73.
《Journal of Natural History》2012,46(21-22):1229-1256
74.
75.
《Journal of Natural History》2012,46(33-34):2097-2104
A new eyeless species, Oodinotrechus liyoubangi n. sp, is described from northern Guangxi. All specimens of this interesting species were collected in three limestone caves in Mulun National Nature Reserve of northern Guangxi, southern China. It is the second species for the genus Oodinotrechus Uéno, 1998, distinguished from the type species O. kishimotoi Uéno, 1998 by its visible scutellum and pronotal structure. Several additional diagnostic characters for the genus and a geographical distribution map for both known species are also provided.http://zoobank.org/urn:lsid:zoobank.org:pub:F82E3C03-0A15-4410-B674-BC8EB95607CE 相似文献
76.
《Journal of Natural History》2012,46(33-34):2123-2131
ABSTRACTA new whitefly species, Pealius satakshiae Dubey, found infesting Quercus leucotrichophora A. Camus (Fagaceae) in the Chail Wildlife Sanctuary, Himachal Pradesh, India, is described. Puparia of the new species differ from described Pealius species in being larger in size, having a differentiated cephalus, rhachisform abdomen and reduced abdominal segment VII, and lacking the first abdominal setae. Puparial characteristics for the genus Pealius Quaintance and Baker in relation to new species are discussed. Camera lucida drawings, images of habitus and holotype, and scanning electron microscope photomicrographs are provided.http://www.zoobank.org/lsid:zoobank.org:pub:9712A865-4DD6-457B-84B0-1C7873316DE4 相似文献
77.
《Journal of Natural History》2012,46(37-38):2237-2253
Four nominal species of the genus Horatia Bourguignat, 1887 were described by Russian authors from Caucasian caves (H. borutzkii Shadin, 1932, H. birsteini Starobogatov, 1962, H. ljovushkini Starobogatov, 1962 and H. sokolovi Starobogatov, 1962). Hitherto all the species were known from type series (presented by empty shells) only. Examination of newly obtained samples from the caves of South Caucasus has shown that the four species actually do not belong to the genus Horatia due to obvious differences in the morphology of the copulatory organs between H. klecakiana Bourguignat, 1887 (the type species of this genus) and the Caucasian snails. Moreover, statistical analysis of conchological variation has revealed that the species H. birsteini, H. ljovushkini, and H. sokolovi are conspecific. Two genera are described: Pontohoratia (includes P. birsteini and P. smyri sp. nov.) and Motsametia (with the single species M. borutzkii comb. nov.). The two genera can be distinguished on the basis of the structure of their copulatory organs. The distribution and ecology of the Caucasian Horatia-like mollusks are briefly outlined.http://zoobank.org/urn:lsid:zoobank.org:pub:4EDFB2AE-CB1D-4113-8CC7-3A1BBB46D838 相似文献
78.
《Journal of Natural History》2012,46(6):731-774
Continuing examination of colonial ascidians in museum collections is revealing further diversity in the family Didemnidae, which abounds in the tropical Indo-West Pacific and around the Australian continent (Kott, 2001). From the present work, it is apparent that much remains to be learnt about this fauna. Of the 45 species discussed in this paper, 16 are new. Larvae are described for the first time for Polysyncraton pedunculatum Kott, 2001 and P. rica Kott, 2001. Amongst the synonymy established in this paper Didemnoides tropicum Sluiter, 1909 is found to be a junior synonym of Lissoclinum patella (Gottschaldt, 1898) and Trididemnum vermiforme Kott, 2001 a junior synonym of T. nobile Kott, 2001. Didemnum nekozita Tokioka, 1967 is found to be a valid species distinct from Polysyncraton cuculliferum (Sluiter, 1909). Prolific replication rates, rapid colony growth, flexibility in growth form and a viviparous habit result in convergence tending to small zooid size, and similar large, increasingly complex colonies found in this family contribute to species diversity around the whole of the Australian continent. 相似文献
79.
《Journal of Natural History》2012,46(35-36):2243-2245
ABSTRACTThe present study describes two new genera, six new species and three new records from the Sea of Marmara. The new genus Marmara gen. nov. belonging to the family Sagartiidae is mainly characterized by having conspicuous muscular belts along the column and the absence of suckers and tenaculi on the body wall. The genus Charisactis gen. nov. belonging to the family Condylanthidae is mainly characterized by having an atypical mesentery arrangement, single siphonoglyph and homotrichs in tentacles. The other species newly described from the Sea of Marmara belong to the families Diadumenidae (one species from deep waters), Halcampoididae (one species from shallow waters), Edwardsiidae (one species from shallow waters) and Epizoanthidae (one species from deep waters). Three species, namely Epizoanthus arenaceus (family Epizoanthidae), Rolandia coralloides (family Clavulariidae) and Virgularia sp. (family Virgulariidae) are reported for the first time from the Sea of Marmara. The external and internal anatomical features as well as cnidom structures of the species are presented and discussed with the closely related species. http://www.zoobank.org/urn:lsid:zoobank.org:pub:51DA9869-D786-4A8A-8C1F-62DC1BB67923 相似文献
80.