全文获取类型
收费全文 | 967篇 |
免费 | 27篇 |
专业分类
林业 | 74篇 |
农学 | 39篇 |
基础科学 | 3篇 |
122篇 | |
综合类 | 292篇 |
农作物 | 30篇 |
水产渔业 | 66篇 |
畜牧兽医 | 315篇 |
园艺 | 27篇 |
植物保护 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 34篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 12篇 |
2014年 | 30篇 |
2013年 | 50篇 |
2012年 | 46篇 |
2011年 | 68篇 |
2010年 | 46篇 |
2009年 | 36篇 |
2008年 | 77篇 |
2007年 | 67篇 |
2006年 | 88篇 |
2005年 | 68篇 |
2004年 | 64篇 |
2003年 | 63篇 |
2002年 | 55篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1961年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有994条查询结果,搜索用时 15 毫秒
931.
<正>通常认为,添加含有高活性木聚糖酶的一类酶制剂仅仅会在小麦为主的日粮中起作用。然而,艾威生物化学(Aveve Biochem)发现,在玉米为主的日粮里面,添加同时含有高活性的木聚糖酶和β-葡聚 相似文献
932.
Wolschrijn CF Gruys E van der Wiel CW Weijs WA 《Veterinary journal (London, England : 1997)》2008,176(3):333-337
The aim of the study was to establish the location of cartilage canals in the medial coronoid process (MCP) of the ulna of young Golden Retrievers, a breed that is predisposed to fractures of the medial coronoid process (FMCP). To determine whether the presence of cartilage canals could be associated with the predilection site of FMCP, the right elbows of nine young Golden Retrievers (aged 4, 6, 8, 10, 13, 16, 18, 22 and 24 weeks) were dissected and, with no prior decalcification, the formaldehyde-fixed MCPs were embedded in methylmethacrylate. The entire MCPs were serially sectioned in the frontal plane from cranial to caudal and the sections (5 microm) were routinely stained. Between the ages of 5 and 10 weeks, three main cartilage canals were visible--medial, central and lateral. All originated from the periosteum of the distal parts of the MCP and ended proximally under the articular cartilage. Branches of the main canals were seen more cranially and caudally. At the age of 13 weeks, the central canal was absent, and the remaining canals showed a smaller diameter. From 16 weeks onwards, no cartilage canals were seen. No direct relationship could be established between the predilection site of FMCP (lateral part of the MCP) and the presence/absence of cartilage canals, since both medial and lateral canals disappeared at the same age. Further research is needed to elucidate the pathogenesis of FMCP. 相似文献
933.
934.
Effect of cross‐match on packed cell volume after transfusion of packed red blood cells in transfusion‐naïve anemic cats 下载免费PDF全文
935.
936.
Staffan Berg Janine Schweier Franka Brüchert Marcus Lindner Erik Valinger 《Scandinavian Journal of Forest Research》2014,29(5):485-498
The forest sector is important for the German Federal State of Baden-Württemberg (BW) and the Västerbotten (VB) County in Sweden. Their forestry wood chains (FWCs) are of similar magnitude and supply forest industries. This study provides a regional comparison of the performance of FWCs from roundwood harvesting, including hauling, to mill gate concerning the factors that impact sustainability and assess different sustainability indicators for alternative supply chains, in particular fully mechanized chains in comparison to motor-manual operations. The harvest volumes are similar but operational conditions differ. Analysis of sustainability indicators demonstrated that the total costs for roundwood to industry are similar. Higher harvesting costs in BW are compensated for by lower transport costs to the mills. Employment per unit is higher in BW because of the high share of labour in felling. Due to smaller machinery and shorter transport distances in BW, energy use and greenhouse gas emissions per unit are lower than in VB. Areas for improvement are the technologies for logging in BW and the logistics of timber transport in VB. 相似文献
937.
Anders Roos Mikael Lindström Lena Heuts Nippe Hylander Erik Lind Christian Nielsen 《Scandinavian Journal of Forest Research》2014,29(4):394-401
The purpose of this study is to understand the innovation diffusion of new wood-based materials, “from lab to market,” to identify the success factors and barriers to market introduction, and to reveal important factors for the success of commercialization. Examples are given from target markets in the furniture, appliance, and automotive sectors. This study is based on three qualitative interview studies in Sweden from 2010 to 2012. The analysis showed that the diffusion process of a new bio-based material normally takes up to 10 years or even more. There are only a few companies along the supply chain whose specialized function is finding new materials. However, the automotive industry regularly monitors the development of new materials. Industrial customers of materials generally obtain information about biobased materials from suppliers, exhibitions, conferences, professional contacts, industry magazines, digital media, customers, and partners in development projects. Different industry sectors apply specific material requirements. Regulations regarding safety issues have a high priority, and the interviewees believed that environmental considerations will increase with time. If the materials are equal in other quality dimensions, environmental performance may cast the deciding vote. Recommendations for a faster diffusion cover the right mix of competences, financing, regulations, creativity, and support from the leadership. 相似文献
938.
This study seeks to contribute to a more complete understanding of how urban form influences biodiversity by investigating the effects of green area distribution and that of built form. We investigated breeding bird diversity in three types of housing development with approximately the same amount of tree cover. No significant differences in terms of bird communities were found between housing types in any of the survey periods. However, detached housing, especially with interspersed trees, had more neotropical insectivores and higher overall diversity of insectivores. Based on our results and theory we suggest a complementary approach to managing biodiversity in urban landscapes – instead of maximising the value and quality of individual patches efforts could go into enhancing over-all landscape quality at the neighbourhood scale by splitting up part of the green infrastructure. The relatively small differences in bird communities also suggest that different stakeholder groups may be engaged in management. 相似文献
939.
Marcus Hedblom Erik Heyman Henrik Antonsson Bengt Gunnarsson 《Urban Forestry & Urban Greening》2014,13(3):469-474
Increased losses of green areas in cities reduce people's experience of flora and fauna. Earlier studies have shown that biodiversity has benefits for urban inhabitants but the influence of animal sounds on people's experience of green space is poorly known. A sample of young urban people (N = 227) rated their reactions – positive or negative – to three bird song combinations: House Sparrow (Passer domesticus), Willow Warbler (Phylloscopus trochilus), 7 spp. i.e. Willow Warbler, Chaffinch (Fringilla coelebs), Blue Tit (Cyanistes caeruleus), Great Tit (Parus major), European Robin (Erithacus rubecula), Common Blackbird (Turdus merula), Great Spotted Woodpecker (Dendrocopos major), three urban settings (residential areas with varying amount of greenery) and nine combinations of song and setting. Bird song was generally considered positive and singing by several species was more highly rated than singing by a single species. On average, urban settings combined with bird song were more highly appreciated than the settings alone and even more so where there was singing by several species rather than just one. We conclude that our data support the idea that bird song contributes to positive values associated with urban green space. Urban planners should consider preserving a variety of habitats in cities for hosting a diversity of birds and thereby boost conservation of songbird diversity and recreational experiences for urban people. 相似文献
940.
Einar Ringø Sigmund Sperstad Reidar Myklebust Terry M Mayhew Agnar Mjelde Webjørn Melle & Rolf Erik Olsen 《Aquaculture Research》2006,37(16):1644-1653
Atlantic salmon (Salmo salar L.) were fed fishmeal protein for 46 days, and 500 g kg−1 of fishmeal protein substituted with meal from Northern krill (Meganyctiphanes norvegica). No differences were observed in weight gain, length gain, feed conversion or specific growth rate between the groups that could be attributed to dietary manipulation. The adherent microbiota in the hindgut of the two rearing groups were further investigated. By substituting fishmeal with krillmeal, the total viable counts of aerobic and facultative aerobic bacteria colonizing the hindgut of Atlantic salmon increased from 8.5 × 104 to 2.2 × 106. Furthermore, dietary krillmeal affected the adherent hindgut microbiota. The Gram‐positive bacteria Carnobacteria piscicola, Microbacterium oxydans, Microbacterium luteolum and Staphylococcus equorum spp. linens and the Gram‐negatives Psychrobacter spp. and Psychrobacter glacincola were not isolated from hindgut of fish fed the krill diet. On the other hand, Pseudomonas fulgida, Pseudomonas reactans and Stenotrophomonas maltophila were not isolated from the control group fed fishmeal. Acinetobacter lwoffi, which is not normally found in the fish gut, was isolated from both feeding groups. Transmission electron microscopy showed bacteria‐like profiles between the hindgut microvilli in both feeding groups indicating autochthonous microbiota. When fish were fed the krill diet, hindgut enterocytes were replete with numerous irregular vacuoles. These vacuoles were not observed in fish fed the fishmeal protein. 相似文献