全文获取类型
收费全文 | 358篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
林业 | 80篇 |
农学 | 8篇 |
基础科学 | 2篇 |
55篇 | |
综合类 | 66篇 |
农作物 | 16篇 |
水产渔业 | 24篇 |
畜牧兽医 | 98篇 |
园艺 | 5篇 |
植物保护 | 20篇 |
出版年
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 30篇 |
2012年 | 14篇 |
2011年 | 25篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 18篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 22篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 2篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1967年 | 3篇 |
1961年 | 3篇 |
1957年 | 2篇 |
1955年 | 1篇 |
1941年 | 1篇 |
1940年 | 1篇 |
1924年 | 3篇 |
1891年 | 1篇 |
排序方式: 共有374条查询结果,搜索用时 11 毫秒
1.
2.
3.
Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry 下载免费PDF全文
Kyeong‐Jun Lee Samad Rahimnejad Madison S Powell Frederick T Barrows Scott Smiley Peter J Bechtel Ronald W Hardy 《Aquaculture Research》2015,46(7):1590-1596
Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds. 相似文献
4.
5.
Frederick R. Gehlbach 《Biological conservation》1975,8(2):79-88
Texas experience suggests that amateur naturalists will be heavily involved in preliminary ecological surveys of natural areas, hence a simple key for identification of community-types is presented. Line intercept transects are suggested for amateur use in providing standardised quantitative data on the physiognomy of natural areas. A scheme for the evaluation of each area utilises the weighted values of climax condition, educational suitability, species significance, community representation, and human impact through multiplicative scoring to give a natural area score. With the weighted values-multiplicative scoring scheme, natural areas are clearly distinguished in priority for acquisition. 相似文献
6.
7.
8.
Giardia infections in domestic cattle has come under increasing scrutiny owing to the potential contamination of surface and ground waters through manure distribution on fields and pasture runoff. The objective of the study was to determine the prevalence and genotypes of Giardia duodenalis in beef calves in major beef cow calf farms in Alberta, Canada. Fecal samples were collected from beef calves aged 2-10 weeks at nine farms in Alberta. Samples were examined for the presence of G. duodenalis cysts by immunofluorescent staining. Giardia cysts were found in 168 of the 495 fecal samples examined, with prevalence ranging from 7 to 60% among farms. Genotypic analysis of positive isolates utilizing PCR and sequencing of a 292 bp fragment of the 16S-rRNA locus, revealed the hoofed livestock genotype in 41 of the 42 isolates. One isolate was identical to the Assemblage A genotype. The results of this study demonstrate that beef calves in this area are primarily infected with the livestock genotype which is thought to be specific to artiodactyl hosts and non-infective to humans. This suggests that the Giardia carried by beef cattle may be a minimal zoonotic threat. 相似文献
9.
10.
James A. Kenar Frederick C. Felker Girma Biresaw Todd L. Kurth 《Industrial Crops and Products》2009,29(1):45-52
Aqueous dispersions of starch–soybean oil (SBO) and starch–jojoba oil (JO) composites, prepared by excess steam jet cooking, form effective dry film lubricants when applied as thick coatings to metal surfaces by a doctor blade. This application method necessitates long drying times, is wasteful, requires the addition of sucrose to promote composite adhesion to the metal surface, and restricts the substrate geometry to planar surfaces. These issues represent important barriers to the commercialization of this aqueous biobased dry film lubricant technology. We now report an air-assisted spray method that uses readily available spray equipment to apply aqueous starch–oil composite dispersions as thin coatings (0.15–2.0 mg/cm2) to metal surfaces quickly and efficiently. Aqueous dispersions of waxy maize starch–oil composites containing either SBO, JO or hexadecane (HD), having 0.020–31.7 wt% oil relative to starch, were applied by air-assisted spraying and could be dried to the touch in approximately 30 s. Additionally, sucrose was found unnecessary for adhesion of the sprayed coatings. Tribological ball-on-flat testing of metal specimens spray coated with starch–SBO, –JO, and –HD composites showed the thin films of starch–SBO and –JO performed better at reducing the coefficient of friction (COF) than the starch–hexadecane composites. A low COF ranging between 0.027 and 0.044 was obtained for the starch–SBO and –JO composites containing 4–5 wt% oil relative to starch. Above 4–5 wt% oil loadings, no further COF reductions were realized. Further results revealed that micrometer-sized oil droplets embedded within the dried starch matrix of the composite film are delivered “on demand”. It appears that when pressure is applied to the dry film lubricant, the starch matrix ruptures and releases the entrained oil to the friction surface. 相似文献