全文获取类型
收费全文 | 705篇 |
免费 | 23篇 |
国内免费 | 1篇 |
出版年
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 40篇 |
2009年 | 45篇 |
2008年 | 31篇 |
2007年 | 40篇 |
2006年 | 25篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 8篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1977年 | 6篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1969年 | 5篇 |
1959年 | 8篇 |
1958年 | 16篇 |
1957年 | 17篇 |
1956年 | 16篇 |
1955年 | 8篇 |
1954年 | 13篇 |
1953年 | 18篇 |
1952年 | 9篇 |
1951年 | 10篇 |
1950年 | 12篇 |
1948年 | 8篇 |
排序方式: 共有729条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga. 相似文献
25.
G. R. CAYLEY P. ETHERIDGE D. C. GRIFFITHS F. T. PHILLIPS B. J. PYE G. C. SCOTT 《The Annals of applied biology》1984,105(2):379-386
The collaborative trials described by Arnold et al., 1984a, b, c provided an extensive range of data on the performance of electrostatically charged rotary atomizers on a variety of crops, at different growth stages, using systemic and non-systemic pesticides. The purpose of this paper is to review the subject to date. 相似文献
26.
27.
28.
SCOTT A. HATCH 《Ibis》1990,132(4):515-524
I monitored the incubation schedules of Fulmars Fulmarus glacialis in an Alaskan colony by observing nests where the male and female were of different colour phases. Complete shifts of up to 16 days were recorded; the average shift in mid-incubation was 4–6 days. Mean shift length was inversely correlated with hatching success in 5 years, suggesting that Fulmars adjusted their foraging patterns to annual differences in food availability. Males assumed the larger share (55%) of incubation on average, and a larger share in years with lower hatching success. Serial correlation in the length of incubation shifts had two components—the influence of prior shift lengths on time spent foraging and individual variation. Failure of the male to relieve the female soon after laying resulted in a few breeding failures and egg losses were associated with exceptionally long shifts throughout incubation. 相似文献
29.
Root Cap Structure in Isoetes macrospora Dur 总被引:1,自引:0,他引:1
Root meristem cells of Isoetes macrosporausually have one plastidwhich is associated with the prominent nucleus, numerous ribosomesand mitochondria, and small vacuoles. During mitosis each plastidappears to replicate so that each daughter cell contains oneplastid. The cell walls of the meristem cells are traversedby numerous plasmodesmata. Central cells of the root cap lackdistally displaced plastids but have one or more amyloplastsassociated with the nucleus. These cells also contain largeprotein deposits. Peripheral root cap cells are characterizedby being vacuolated, and by possessing a few dictyosomes andprotein deposits. They appear to be sloughed infrequently. Isoetes macrospora Dur, root cap, protein bodies, ultrastructure 相似文献
30.