全文获取类型
收费全文 | 130篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 4篇 |
教育与普及 | 1篇 |
现状及发展 | 4篇 |
综合类 | 90篇 |
自然研究 | 38篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 32篇 |
2009年 | 8篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
排序方式: 共有138条查询结果,搜索用时 0 毫秒
81.
李红敬 《信阳师范学院学报(自然科学版)》2003,16(4):449-450,491
调查发现猫儿山保护区内有淡水鱼类共23种.隶属3目8科18属,从食性上分,植食性占34.8%,肉食性占21.7%.杂食性占43.5%;从栖息环境上分,上层占4.3%;中层占25.8%,下层占69.9%,其分布特性与其栖息环境是密切相关的. 相似文献
82.
《Journal of Natural History》2012,46(25-28):1585-1602
Re‐examination of the syntypes of Caridina gracilirostris De Man, 1892, shows that the type series is composed of three species. These three species are similar in the form of the rostrum, but can be differentiated easily by a combination of rostral formula and sexual appendages. To stabilize the taxonomic status of these species, a lectotype for C. gracilirostris is selected. A lectotype for Caridina appendiculata Jalihal and Shenoy, 1998, is also designated from among the remaining syntypes of C. gracilirostris. A new species, C. neglecta, is described. Caridina gracilirostris and C. gracilima Lanchester, 1901, are redescribed and figured, and C. appendiculata is transferred to the C. nilotica species group. A new species group is also recognized for C. gracilirostris, C. neglecta, C. gracilima, and a new species, C. longifrons. The C. gracilirostris species group is defined here as taxa possessing a rostrum with subapical teeth, fewer than 10 dorsal teeth, and without any postorbital teeth. 相似文献
83.
《Journal of Natural History》2012,46(21-22):1279-1298
A new genus of freshwater crab, Ghatiana, with two new species, Ghatiana aurantiaca and Ghatiana hyacintha, and a new species of Gubernatoriana Bott, 1970, are described from the Western Ghat Mountains in Maharashtra State, India. Ghatiana is most similar to Gubernatoriana by its wide, highly arched carapace and by the shape of the male abdomen. Nevertheless, the new genus can be distinguished from Gubernatoriana by the broadness of carapace, length of male abdomen, shape of sixth abdominal somite, length of telson and length of G1 terminal article. Ghatiana aurantiaca sp. nov. and G. hyacintha sp. nov. are distinguished by differences in body colour, carapace width, and G1 morphology, whereas Gubernatoriana triangulus sp. nov. is distinguished from two other known species [Gubernatoriana gubernatoris (Alcock, 1909) and Gubernatoriana pilosipes (Alcock, 1909)] by its triangular G1 subterminal segment and by its carapace morphology. Keys to the species of both the genera are provided.http://www.zoobank.org/urn:lsid:zoobank.org:pub:36BAA1EA-DC15-4B06-BA09-7BD26C63FF54 相似文献
84.
85.
王雪虹 《集美大学学报(自然科学版)》1996,(Z1)
介绍和分析了台湾省淡水最重要的特优种类──鳗鱼、罗氏沼虾、甲鱼、牛蛙的养殖概况和特优养殖存在问题及展望,提供给我国管理层和养殖者借鉴。使我国淡水特优产品养殖,减少弯路,避免盲目,朝健康稳定方向发展。 相似文献
86.
87.
我国淡水湖泊的水环境安全及其保障对策研究 总被引:4,自引:0,他引:4
依据2006年统计数据, 计算了我国十大主要淡水湖环湖区域的人口密度指数、人口集中度指数、城镇化指数和经济实力指数、经济集中度指数、工农业集中度指数。结果表明:环湖区域的人 口相对集中, 城镇化水平相对较高, 是所在省(市) 的农产品供应基地与增长极, 社会经济发展对湖泊水资源的依附性大。另一方面, 通过对文献资料的整理、统计, 发现我国淡水湖泊面积萎缩、污染加剧、富营养化问题突出, 湖滨带生态系统受损严重、生物多样性锐减, 水环境安全的形势极为严峻。基于此作者认为, 淡水湖泊的水环境安全关系到地方乃至全 国社会经济发展的大局, 我国须建立健全淡水湖泊水环境安全监测预警体系, 构建多元化的淡水湖泊生态环境问题防治控制体系, 并强化重点领域的技术支撑与工程示范。 相似文献
88.
89.
《Journal of Natural History》2012,46(21):2599-2614
One species of Trichodactylidae and four species of Pseudothelphusidae are present on continental islands in three areas of Central and South America. (1) Trinidad and Margarita Island have, in common with the Venezuelan mainland, the pseudothelphusid Eudaniela garmani (Rathbun, 1898); additionally, Trinidad shares with the mainland the trichodactylid Dilocarcinus dentatus (Randall, 1839). These disjunct distributions can be attributed to changes in sea level during the Quaternary, but the presence of the endemic pseudothelphusid Microthelphusa odaelkae (Bott, 1970) in Trinidad probably reflects an older connection with the continent. (2) A new species, Potamocarcinus roatensis, was found on Roatan Island, off the coast of Honduras. A cladistic analysis of the genus Potamocarcinus (H. Milne Edwards, 1853) revealed a close association of P. roatensis with P. magnus (Rathbun, 1896), a widely distributed Central American pseudothelphusid. Possibly both species originated in a pre-Quaternary vicariant event. (3) Another pseudothelphusid, Hypolobocera gorgonensis von Prahl, 1983, inhabits disjunct areas on Gorgona Island, off the Pacific coast of Colombia, and on the mainland of Ecuador, reflecting either a wider distribution before the last Holocene transgression or accidental dispersal through natural rafts. 相似文献
90.
《Journal of Natural History》2012,46(23):2083-2088
Freshwater medusae of the genus Limnocnida were found in a shallow lake in the floodplain of the Ayeyarwaddy River. The medusae are described and identified as a small form of L. indica. Single immature specimens were found in two other localities in Myanmar, within the Ayeyarwaddy catchment. These records are an eastward extension of the known range of Limnocnida, and indicate that it is probably widespread in the Ayeyarwaddy catchment. The associated phytoplankton and zooplankton are listed, and the zooplankters are compared to those found with Limnocnida in a floodplain lake of the River Sokoto in West Africa. In both situations there was a marked preponderance of rotifers and cyclopoid copepods. This indicates that Limnocnida influences the zooplankton in a manner similar to that found in various studies on the freshwater medusa Craspedacusta in Europe and North America. 相似文献