全文获取类型
收费全文 | 612篇 |
免费 | 43篇 |
国内免费 | 1篇 |
专业分类
林业 | 35篇 |
农学 | 7篇 |
基础科学 | 3篇 |
60篇 | |
综合类 | 118篇 |
农作物 | 24篇 |
水产渔业 | 43篇 |
畜牧兽医 | 313篇 |
园艺 | 22篇 |
植物保护 | 31篇 |
出版年
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 22篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 22篇 |
2012年 | 32篇 |
2011年 | 33篇 |
2010年 | 21篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 7篇 |
1966年 | 4篇 |
1928年 | 3篇 |
排序方式: 共有656条查询结果,搜索用时 31 毫秒
51.
Bat activity on riparian zones and upper slopes in Australian timber production forests and the effectiveness of riparian buffers 总被引:1,自引:0,他引:1
Unlogged buffers are used to ameliorate impacts to riparian areas in timber production forests. One function of these buffers is to protect the biodiversity of riparian areas. We measured bat activity in buffered streams with ultrasonic detectors across four different stream orders in logged, regrowth and mature forests (60 sites). Bat activity, foraging rates and species richness were similar in buffered streams surrounded by logged, regrowth and mature forests, suggesting that riparian areas effectively provide habitat for foraging and commuting bats in selectively logged forests. Vespadelus pumilus was the only species that responded to logging history, with decreased activity in mature forests. We found higher activity on larger rather than smaller order streams, a pattern also not affected by logging history. Bat activity along paired forest trail flyways on upper slopes (60 sites) was measured simultaneously with riparian flyway activity (for a total of 120 sites) to determine the importance of riparian areas relative to other available flyways. Activity was higher on upper slopes than on small streams, but similar to levels on larger streams. Total foraging activity was similar between riparian zones and upper slopes. Upper slopes contained higher species diversity, with Chalinolobus gouldii, Miniopterus schreibersii, Mormopterus norfolkensis, Scotorepens sp., Vespadelus pumilus and, to a lesser extent, Vespadelus darlingtoni detected more often than along streams. Other species (Rhinolophus megaphyllus, Nyctophilus spp. and Miniopterus australis) were not affected by topography. Estimates of total vegetation cover and, in particular, rainforest cover, were negatively associated with bat activity, highlighting the need for management of forest ‘clutter’ in regrowth forests for a suite of bat species. Streams and forest trails provide areas of lower clutter, which assist in maintaining high species diversity in regrowth forests. Our results support the use of riparian buffers, and point to the need for greater recognition of tracks on upper slopes as important habitat. 相似文献
52.
53.
Bradley D 《Science (New York, N.Y.)》2003,300(5628):2022-2023
54.
Isolation of a cDNA from the virus responsible for enterically transmitted non-A, non-B hepatitis 总被引:59,自引:0,他引:59
G R Reyes M A Purdy J P Kim K C Luk L M Young K E Fry D W Bradley 《Science (New York, N.Y.)》1990,247(4948):1335-1339
Major epidemic outbreaks of viral hepatitis in underdeveloped countries result from a type of non-A, non-B hepatitis distinct from the parenterally transmitted form. The viral agent responsible for this form of epidemic, or enterically transmitted non-A, non-B hepatitis (ET-NANBH), has been serially transmitted in cynomolgus macaques (cynos) and has resulted in typical elevation in liver enzymes and the detection of characteristic virus-like particles (VLPs) in both feces and bile. Infectious bile was used for the construction of recombinant complementary DNA libraries. One clone, ET1.1, was exogenous to uninfected human and cyno genomic liver DNA, as well as to genomic DNA from infected cyno liver. ET1.1 did however, hybridize to an approximately 7.6-kilobase RNA species present only in infected cyno liver. The translated nucleic acid sequence of a portion of ET1.1 had a consensus amino acid motif consistent with an RNA-directed RNA polymerase; this enzyme is present in all positive strand RNA viruses. Furthermore, ET1.1 specifically identified similar sequences in complementary DNA prepared from infected human fecal samples collected from five geographically distinct ET-NANBH outbreaks. Therefore, ET1.1 represents a portion of the genome of the principal viral agent, to be named hepatitis E virus, which is responsible for epidemic outbreaks of ET-NANBH. 相似文献
55.
Taylor FW Diner DJ Elson LS McCleese DJ Martonchik JV Delderfield J Bradley SP Schofield JT Gille JC Coffey MT 《Science (New York, N.Y.)》1979,205(4401):65-67
Further results from the Venus orbiter radiometric temperature experiment (VORTEX) on the Pioneer orbiter are presented. These are used to characterize the three-dimensional temperature field, the cloud structure, and the dynamics of the 60-to 130-kilometer altitude region of the Venus atmosphere. One of the new discoveries is a "dipole" structure at high latitudes, with two hot spots rotating around the pole, surrounded by banks of cold cloud. 相似文献
56.
Outeiro TF Kontopoulos E Altmann SM Kufareva I Strathearn KE Amore AM Volk CB Maxwell MM Rochet JC McLean PJ Young AB Abagyan R Feany MB Hyman BT Kazantsev AG 《Science (New York, N.Y.)》2007,317(5837):516-519
The sirtuins are members of the histone deacetylase family of proteins that participate in a variety of cellular functions and play a role in aging. We identified a potent inhibitor of sirtuin 2 (SIRT2) and found that inhibition of SIRT2 rescued alpha-synuclein toxicity and modified inclusion morphology in a cellular model of Parkinson's disease. Genetic inhibition of SIRT2 via small interfering RNA similarly rescued alpha-synuclein toxicity. Furthermore, the inhibitors protected against dopaminergic cell death both in vitro and in a Drosophila model of Parkinson's disease. The results suggest a link between neurodegeneration and aging. 相似文献
57.
Bradley HC 《Science (New York, N.Y.)》1904,19(474):196-197
58.
59.
60.