全文获取类型
收费全文 | 616篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
林业 | 76篇 |
农学 | 22篇 |
基础科学 | 5篇 |
108篇 | |
综合类 | 72篇 |
农作物 | 22篇 |
水产渔业 | 59篇 |
畜牧兽医 | 235篇 |
园艺 | 11篇 |
植物保护 | 38篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 20篇 |
2013年 | 26篇 |
2012年 | 31篇 |
2011年 | 52篇 |
2010年 | 34篇 |
2009年 | 25篇 |
2008年 | 50篇 |
2007年 | 42篇 |
2006年 | 31篇 |
2005年 | 45篇 |
2004年 | 41篇 |
2003年 | 41篇 |
2002年 | 34篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 1篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有648条查询结果,搜索用时 437 毫秒
111.
112.
The government of Kenya encourages aquaculture development by offering credit facilities through the government agricultural
finance institution, Agriculture Finance Corporation. Nevertheless, the level of credit use in fish farming is very low. Access
to credit is among several factors that affect farmers’ decision of whether to use particular technology or services. The
study examined factors that affected the decision of fish farmers in Kenya to utilize credit facilities in fish production
using a probit model. The analysis suggests that farmers in the Western province will have a 19% more probability of using
credit facilities for their fish farming operations than farmers from the other provinces such as the Rift Valley, Central,
and the Eastern province. The effect of tilapia sales on the probability of credit use by fish farmers is more than three
times that of catfish sales. Total pond acreage owned by fish farmers had a positive effect on credit use but the effect was
very small and negligible. The level of fish farmers’ use of credit facilities is very low, and there is probably the need
to educate farmers on credit use and for the government agricultural lending agency and other commercial agricultural lenders
to invest in this enterprise. Kenyan lending institutions have financed traditional agricultural enterprises, and with the
growing production of farmed fish, more research is needed to document the aquaculture business model to assist in assessing
the profitability potential in aquaculture. 相似文献
113.
Bo-Rong Peng Kuei-Hung Lai Gene-Hsiang Lee Steve Sheng-Fa Yu Chang-Yih Duh Jui-Hsin Su Li-Guo Zheng Tsong-Long Hwang Ping-Jyun Sung 《Marine drugs》2021,19(10)
Sponge-derived scalaranes are remarkable sesterterpenoids previously found to exhibit profound inhibitory effects against neutrophilic inflammation. In our current work, we constructed the metabolomic profile of marine sponge Lendenfeldia sp. for the first time using a tandem mass spectrometry (MS/MS) molecular networking approach. The results highlighted the rich chemical diversity of these scalaranes, motivating us to conduct further research to discover novel scalaranes targeting neutrophilic inflammation. MS- and NMR-assisted isolation and elucidation led to the discovery of seven new homoscalaranes, lendenfeldaranes K–Q (1–7), characterized by methylation at C-24, together with five known derivatives, lendenfeldarane B (8), 25-nor-24-methyl-12,24-dioxoscalar-16-en-22-oic acid (9), 24-methyl-12,24,25-trioxoscalar-16-en-22-oic acid (10), felixin B (11), and 23-hydroxy-20-methyldeoxoscalarin (12). Scalaranes 1–4 and 6–12 were assayed against superoxide anion generation and elastase release, which represented the neutrophilic inflammatory responses of respiratory burst and degranulation, respectively. The results indicated that 1–3 and 6–12 exhibited potential anti-inflammatory activities (IC50 for superoxide anion scavenging: 0.87~6.57 μM; IC50 for elastase release: 1.12~6.97 μM). 相似文献
114.
A. Rowhani Steve Daubert K. Arnold M. Al Rwahnih V. Klaassen D. Golino J. K. Uyemoto 《European journal of plant pathology / European Foundation for Plant Pathology》2018,151(4):919-925
An interactive relationship between vitiviruses and grapevine leafroll viruses was characterized in grapevine. Grapevine viruses A and B (GVA and GVB) were found more frequently in the presence of co-infecting Grapevine leafroll associated viruses (GLRaV-1, ?2 or ?3) than in their absence. The titers of the vitiviruses in co-infection with leafroll viruses were found to be higher than were their titers in the absence of leafroll virus infection. The occurrence of vitivirus-associated stem-pitting symptoms was correlated with leafroll virus co-infection. Specific pairing associations on the species level were found between different viti- and leafroll virus species: GVB was associated preferentially with GLRaV-2; GVA was associated preferentially with GLRaV-1 and GLRaV-3. In contrast to the increase in vitivirus titer seen with leafroll virus co-infection, the incidence and titer of grapevine leafroll virus appeared to be unaltered by vitivirus co-infection. The potential for a synergistic enhancement of grapevine disease in co-infected vines is discussed. 相似文献
115.
116.
Salty stories,fresh spaces: Lessons for aquatic protected areas from marine and freshwater experiences 下载免费PDF全文
Erin K. Loury Shaara M. Ainsley Shannon D. Bower Ratana Chuenpagdee Tracy Farrell Amanda G. Guthrie Sokrith Heng Zau Lunn Abdullah Al Mamun Rodrigo Oyanedel Steve Rocliffe Suvaluck Satumanatpan Steven J. Cooke 《水产资源保护:海洋与淡水生态系统》2018,28(2):485-500
117.
118.
119.
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