全文获取类型
收费全文 | 190篇 |
免费 | 12篇 |
专业分类
林业 | 19篇 |
农学 | 6篇 |
15篇 | |
综合类 | 33篇 |
农作物 | 19篇 |
水产渔业 | 17篇 |
畜牧兽医 | 79篇 |
园艺 | 4篇 |
植物保护 | 10篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1921年 | 2篇 |
1916年 | 2篇 |
1912年 | 2篇 |
排序方式: 共有202条查询结果,搜索用时 17 毫秒
1.
Bill Slee 《Small-Scale Forestry》2006,5(1):1-17
The nature of private forestry in the UK as an economic activity is changing, with increasing ‘public good’ demands being
placed on forest owners, with or without compensation from government. Although the motives for owning woodland are weakly
researched, it is evident that amenity and recreational interests rather than formal productive economic activity are a major
force in influencing woodland purchase and may well be a dominant force in woodland management over many parts of the UK.
Recent research suggests a need for recognition of the high value of the public goods and, in particular, recognition of their
high levels of spatial variability, whilst recognising that the public good — private good dualism is an oversimplification
of the actual situation. New policy instruments are currently being implemented in various parts of the UK by devolved governments,
and their capacity to both remediate market failure and address the needs of forest owners is considered. Their voluntary
character and the preferences of forest owners may seriously constrain the optimal delivery of public goods. Further, existing
policy instruments may be seen as insufficiently geographically targeted to areas where the greatest social benefits could
be anticipated from policy-induced improvements in public good values. 相似文献
2.
3.
We undertook a mark–recapture study of three pool‐dwelling balitoroid loaches and a nonmigratory goby in a Hong Kong hillstream, which extended over a 35‐week period. The target species were Pseudogastromyzon myersi and Liniparhomaloptera disparis (Balitoridae), Schistura fasciolata (Nemacheilidae) and Rhinogobius duospilus (Gobiidae). Recapture rates of tagged individuals were high (58% overall), especially for the abundant R. duospilus (70% of 412 tagged) and P. myersi (57% of 762 tagged). At the end of the study, most recaptured individuals (78% of gobies, 62% of P. myersi, 42% of L. disparis and 67% of S. fasciolata) were within the pools where they had been released. Of those that had moved elsewhere, maximum displacements ranged from 46 m (R. duospilus) to 101 m (P. myersi), giving rise to a strongly leptokurtic distribution of movement distances. Mean displacements after 35 weeks ranged from only 2.9 m (R. duospilus) to 10.0 m (L. disparis). The sedentary behaviour of these species was more marked than most other small benthic fishes, although our study excluded the breeding period and wet season when high flows might have stimulated movement. Among the mobile P. myersi individuals, most travelled upstream, whereas mobile gobies tended to move downstream. Juveniles of P. myersi and R. duospilus, as well as large adult P. myersi, were especially sedentary, while mobile adult P. myersi that travelled further showed smaller growth increments. The highly sedentary habits of all four fishes suggest that they may exert persistent local top‐down control of benthic communities within pools in Hong Kong streams. 相似文献
4.
Conservation organizations in the northeastern United States (US) recommend forest clearcutting to create shrubland habitat, which is required by many wildlife species with declining populations. The planning of habitat management programs is hampered by a lack of information on the current extent of shrubland habitat and the current rate of forest clearcutting that creates shrubland habitat. We addressed these information gaps by using a combination of automated and manual approaches to determine the extent and spatial configuration of shrubland habitat and recent forest clearcuts. We focused on the state of Rhode Island because (a) it is representative of the northeastern US in terms of the prevalence of private ownership of forests, and the ongoing decline in the populations of many shrubland wildlife species; (b) federal, state and private conservation groups are actively promoting clearcuts to create shrubland habitat; (c) many state-wide GIS databases are available; and (d) the spatial extent of the state made our results both generalizable and politically relevant. Our fine-scale mapping allowed a detailed analysis of shrubland distribution in conjunction with other available GIS layers that facilitates identification of priority areas for habitat management. We found that the extent of upland shrubland in non-coastal areas is decreasing by at least 1.5% annually. Considering the lack of consensus about conservation targets for the amount of shrubland, we propose that conservation organizations attempt to stabilize rather than expand the extent of shrubland habitat. This approach would provide an opportunity to assess whether the current extent of shrubland is sufficient to maintain reduced but stable wildlife populations that require this habitat. We propose a coordinated forest management program with targets for increased forest management on conservation lands. We found that the average patch size of shrubland created by recent clearcuts is large enough for most shrubland bird species, but too small for the New England cottontail (Sylvilagus transitionalis), which has been proposed for threatened and endangered status. 相似文献
5.
Kuhnlein H Erasmus B Creed-Kanashiro H Englberger L Okeke C Turner N Allen L Bhattacharjee L 《Public health nutrition》2006,9(8):1013-1019
This is a short report of a 'safari' held in conjunction with the International Congress of Nutrition in September 2005, in Futululu, St. Lucia, South Africa. Participants were several members of the International Union of Nutritional Sciences Task Force on Indigenous Peoples' Food Systems and Nutrition, other interested scientists and members of the Kwa Zulu indigenous community. The paper describes the rationale for and contributions towards understanding what might be successful interventions that would resonate among indigenous communities in many areas of the world. A summary of possible evaluation strategies of such interventions is also given. 相似文献
6.
Sarah A. Bekessy Brendan A. Wintle Ascelin Gordon Julian C. Fox Ryan Chisholm Bill Brown Tracey Regan Nick Mooney Steve M. Read Mark A. Burgman 《Biological conservation》2009,142(11):2438-2448
The wedge-tailed eagle is Australia’s largest bird of prey and one of the largest eagles in the world. Aquila audax fleayi is an endemic Tasmanian subspecies isolated for 10,000 years from the nominate subspecies on the Australian mainland. The Tasmanian wedge-tailed eagle is classified nationally and at a State level as endangered due to its small number of breeding pairs, low breeding success and high rate of mortality from unnatural causes. The subspecies experiences mortality throughout its range from shooting, poisoning, trapping, road accidents, electrocutions and collisions with wind turbines, aircraft, fences and overhead wires, which we term ‘un-natural mortality’. A portion of the subspecies’ range is managed for timber production, which can lead to disturbance of nest sites and the loss of nest trees. We use a model of the eagle population from the Bass District in northeast Tasmania to explore the relative importance of different sources of mortality and nesting habitat loss, and the potential for mitigating impacts associated with unnatural mortality, disturbance, nesting habitat loss and human access to forests. We create a habitat map including suitable nest sites and link it to a dynamic landscape population model based on life history traits and disturbance responses. Using the program RAMAS-Landscape, we model alternative forest management scenarios, ranging from no timber harvesting and a natural wildfire regime, to scenarios prescribing native forest harvesting and regeneration and different levels of conversion of native forest to plantation under the same natural wildfire regime. The results indicate that the Tasmanian wedge-tailed eagle is sensitive to unnatural mortality, plantation establishment and native forest harvesting. The predicted decline over the next 160 years (65%) will most likely be driven largely by loss of current and potential future nest sites associated with harvesting activities, exacerbated by unnatural mortality in the wider landscape. Interventions that minimise unnatural mortality, reduce nest disturbance, and retain breeding habitat and nest sites may improve the prospects for the subspecies in the Bass District. If nest disturbance and unnatural mortality continue at the rates modelled here, the species appears to face a high risk of declining substantially in the region. 相似文献
7.
Wrieden WL Anderson AS Longbottom PJ Valentine K Stead M Caraher M Lang T Gray B Dowler E 《Public health nutrition》2007,10(2):203-211
OBJECTIVE: To evaluate the feasibility of undertaking a food skills intervention study in areas of social deprivation aimed at altering cooking confidence, food preparation methods and dietary choices. DESIGN: A standardised skills programme was implemented in community-based settings. Pre- (T1) and post-intervention (T2) and 6-month follow-up (T3) measures (7-day diaries and self-administered questionnaires) were undertaken in intervention and comparison groups. SETTING: Eight urban communities in Scotland. SUBJECTS: One hundred and thirteen adults living in areas of social deprivation. RESULTS: It was clear that many subjects led fragmented lives and found commitment to intervention classes problematic. Sixty-three subjects completed the final (T3) assessments. The response to each component varied due to inability to attend sessions, illness, study requirements, employment, moving out of the area, change in circumstances, loss of interest and loss of postal questionnaires. At baseline, reported consumption of fruit and vegetables was low (mean frequency 8.1 +/- 4.78 times per week). Fruit intake increased significantly (P < 0.05) between T1 and T2 in the intervention group (1.7 +/- 2.36 to 2.7 +/- 3.28 times per week) only. Between T1 and T3, there was a significant increase (P < 0.05) in intervention subjects who reported confidence in following a recipe (67-90%,). CONCLUSIONS: This exploratory trial shows that a food skills intervention is likely to have a small but positive effect on food choice and confidence in food preparation. A full-scale randomised controlled trial in this hard-to-reach group would require a range of flexible approaches rather than a fully defined intervention, and presents challenges for trial design. 相似文献
8.
9.
加拿大安达略省家禽生产者对死禽处理通常有以下几种方法:选择经认证的死畜禽处理公司,坑埋,焚烧,堆肥.本文描述了使用堆肥法成功堆肥家禽屠体的一些关键因素. 堆肥是一个狭长的可被生物降解的有机物质堆,有很大的表面积以便氧气良好地渗透.堆肥通过需氧微生物分解生物有机物质制成一个稳定的、类似土壤的物质,称为腐殖质.为了刺激微生物快速降解,有必要给这些生长增殖的微生物提供最理想的环境. 相似文献
10.