全文获取类型
收费全文 | 300篇 |
免费 | 8篇 |
国内免费 | 10篇 |
专业分类
丛书文集 | 18篇 |
教育与普及 | 2篇 |
现状及发展 | 1篇 |
综合类 | 255篇 |
自然研究 | 42篇 |
出版年
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 44篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 18篇 |
2008年 | 7篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有318条查询结果,搜索用时 15 毫秒
11.
《Journal of Natural History》2012,46(11-12):651-667
We characterised the mite fauna associated with a subtidal population of Laminaria ochroleuca in the Cantabrian Sea during a 4-year study. We found 2780 individuals belonging to 35 species. The mite assemblage comprised both north Atlantic and Mediterranean species, as usually reported from the Lusitanian region. The most abundant and diverse subfamily was Copidognathinae, followed by Halacarinae and Lohmannellinae. The greatest abundance of mites was detected on kelp holdfasts, not only strictly phytal mites were found but also interstitial mites or those associated with other macrofauna. Such a distribution could be explained by the high diversity and heterogeneity of microhabitats provided by holdfasts. Mite abundance fluctuated during the 4 years of the study. However, the lowest abundance was detected during the last year of sampling. During that year, the studied algal population suffered a severe decay leaving only degenerating holdfasts attached to the substrate, which could explain the decrease in mite numbers. 相似文献
12.
《Journal of Natural History》2012,46(29-30):1805-1834
Three new species of the genus Pacificabathynella Schminke and Noodt, 1988 are described from groundwater aquifers in glaciated North America (Montana, USA). This is the first time that this genus, known previously only from the state of California, has been documented in Montana. Pacificabathynella and Paradoxibathynella Serban, 2000 are the only genera that show sexual dimorphism in thoracopod VI. Pacificabathynella kalispellensis sp. nov. has several unique features: the setal formula of the antenna (0/2+exop/3/12/6/8/5); the setal formula of the maxilla (7/4/7/6); the presence of an epipod on thoracopod II; tufts of setulae and abundant setae on the basipod and endopod of thoracopods I to V; the epipod of thoracopod VIII female three times longer than the basipod; three smooth setae on the exopod of the female thoracopod VIII; eight spines on the endopod of the uropod and the endopod longer than the sympod, whereas the opposite is typical. Pacificabathynella stanfordi sp. nov. has several unique features: only five setae on the exopod of thoracopods II to VII, while six setae are common in the genus; only six setae on the second segment of the first pleopod; five spines on the endopod and seven setae on the exopod of the uropod. Pacificabathynella ruthae sp. nov. is the largest species and has several unique features: antennule equal in size to the antenna, whereas in the rest of the species of the genus the antenna is larger; the projection of the inner lobe of the male thoracopod VIII is bidentate and there are six spines on the endopod and nine setae on the exopod of the uropod. The three new species have slight differences in the pars molaris of the mandible and in thoracopod VIII of males, and there are other minor differences between the females and the species Pacificabathynella sequoiae. The new taxa, together with the new genus Montanabathynella described separately, represent a 30% increase in North American taxa. Considering the glaciated landscape and the fragmented nature of alluvial aquifer habitat, we believe that there is a profound lack of critical knowledge of the biogeography and biodiversity of syncarids in North America. 相似文献
13.
《Journal of Natural History》2012,46(3):631-637
A new genus and species of the family Parabathynellidae, Sabahbathynella wongi, is described. It has been discovered in the interstitial of coarse sand filling the spaces between big stones of the bank along a stream in Sabah on Borneo. The new genus of the family Parabathynellidae exhibits some unusual features which make it impossible to assess its phylogenetic position. There are some convergencies with the genus Thermobathynella. 相似文献
14.
《Journal of Natural History》2012,46(5-6):309-321
Montanabathynella salish gen. nov. sp. nov., of the family Parabathynellidae, from Montana, USA, is described. The new species displays several exclusive characters: distal endite of the maxillule with nine claws and a very large and distinctive male thoracopod 8 with four lobes in the basal penial region and a long recurved exopod without setation. It also presents a unique combination of characters: antennule seven‐segmented; antenna six‐segmented; labrum with 18 teeth; exopod of thoracopods three‐ to six‐segmented, endopod with one dorsal seta on the first and second segments and epipod only present on thoracopods 4 to 7; pleopods absent; endopod of thoracopod 8 male with two setae and exopod without setae; female thoracopod 8 having two segments, first segment with two groups of denticles and the second one with three long barbed setae; 15 spines on sympod, four spines and spinous process on endopod and 12 setae on exopod of uropod. 相似文献
15.
16.
《Journal of Natural History》2012,46(5):1177-1193
Seventeen species of Psocoptera are recorded from Bermuda, increasing the known number from three. Four new species are described: Echmepteryx atlantica n. sp., Caecilius bermudensis n. sp., Indiopsocus hilburni n. sp., and I. nebulosus n. sp. The latter two species appear to be closely related and two alternative hypotheses are proposed for their origin. Ectopsocus spilotus Thornton and Wong is recorded outside the central Pacific area for the first time. The species are assigned to four categories according to probable duration of time on Bermuda and probable source of original invaders: (1) endemics (four species); (2) species with wide distributions in the tropics and subtropics, not restricted to islands and sea coasts (four species); (3) species largely restricted to sea coasts and islands, not necessarily tropical (three species); (4) species widely distributed in southeastern United States, not restricted to the sea coast or the subtropical region (five species). 相似文献
17.
《Journal of Natural History》2012,46(33-34):2131-2144
We recorded species abundance and richness of oribatid mites along 16 plots established in semi-deciduous forest fragments in Amazonia. The results were compared with a published dataset consisting of an inventory carried out in 38 plots in the surrounding savanna. Totals of 143 and 91 species were recorded in the forest fragments and savanna, respectively. Sørensen similarity index between both environments was 0.44. Ordination of sites according to oribatid mite species composition showed a clear separation between forest fragments and savanna. Rostrozetes ovulum, Archegozetes longisetosus and Eohypochthonius (Eohypochthonius) becki were abundant and frequent in the forest fragments but exceedingly rare in the savanna. Neoppia (Neoppia) schauenbergi, Pseudoppia sp. C, Microppia sp. A and Cosmochthonius sp. A were limited to the savanna. This study also represents an early step toward knowing which groups of species are exclusive to one or another vegetation type or are sensitive to their inherent environmental conditions. 相似文献
18.
冶勒水电站水库对陆生脊椎动物的影响 总被引:1,自引:1,他引:1
余志伟 《西华师范大学学报(哲学社会科学版)》1990,11(2):130-136
本文对冶勒乡进行了陆生脊椎动物调查,有两栖类12种,爬行类6种,鸟类149种,兽类52种.按其分类及资源类型、区系组成、分布特点,结合自然条件、水库形态、库容、运行特点等,分析了水库修建期间及蓄水后对陆生脊椎动物的影响,预测其演变趋势,并提出相应的对策. 相似文献
19.
20.