全文获取类型
收费全文 | 607篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
林业 | 84篇 |
农学 | 35篇 |
基础科学 | 3篇 |
83篇 | |
综合类 | 41篇 |
农作物 | 66篇 |
水产渔业 | 75篇 |
畜牧兽医 | 187篇 |
园艺 | 11篇 |
植物保护 | 48篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 23篇 |
2020年 | 30篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 23篇 |
2016年 | 25篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 50篇 |
2012年 | 41篇 |
2011年 | 35篇 |
2010年 | 30篇 |
2009年 | 18篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 18篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有633条查询结果,搜索用时 218 毫秒
81.
Mohamed S. Hassaan Eman Y. Mohammady Mohamed R. Soaudy Amina A. S. Abdel Rahman 《Aquaculture Nutrition》2019,25(4):841-853
A 3 × 2 factorial experiment was designed to evaluate the effect of different ratios of fish meal (FM): sunflower meal (SFM) with or without exogenous xylanase supplementation on growth, feed utilization, digestive enzymes activities, apparent digestibility, intestinal and liver morphology and chemical composition of Nile tilapia, Oreochromis niloticus. Three isonitrogenous (329.80 g/kg of crude protein) and isoenergetic (18.46 MJ/kg gross energy) experimental diets were formulated as SFM1 (FM:SFM = 2:1), SFM2 (FM:SFM = 1:1) and SFM3 (FM:SFM = 1:2) based on protein content. Each diet was supplemented with 0 or 0.5 g/kg of exogenous xylanase and was fed to triplicate groups of twelve fish (with initial weight, 1.31 ± 0.02 g) for 84 days. After 84 days of feeding period, the highest weight gain, specific growth rate, protein efficiency, protein productive value and the best feed conversion ratio were recorded in fish fed either SFM1 or SFM2 supplemented with exogenous xylanase. Whereas lowest growth performance was recorded in fish fed SFM2 and SFM3 un‐supplemented with xylanase. The highest activities of chymotrypsin, trypsin, lipase, amylase, alkaline phosphatase and cholecystokinin were observed in fish fed SFM1 and SFM2 diets supplemented with xylanase. The highest ADCs of dry matter, protein, lipid and digestible energy were recorded in fish fed SFM1 and SFM2 diets supplemented with exogenous xylanase. Supplementation of exogenous xylanase improved muscularis mucosa thickness, height of mucosal folds and enterocytes of intestinal fish. Addition of exogenous xylanase increased the calcium and phosphorus retention. Results of this study indicated that the addition of exogenous xylanase to diet containing high inclusion level of sunflower meal improved growth, digestive enzymes, nutrient digestibility, histological morphometric of liver and intestine and nutrient retention. 相似文献
82.
Md. Abu Hanif Ranjan Mitra Roy Md. Shafiqul Bari Polash Chandra Ray Md. Shoaibur Rahman Md. Faruq Hasan 《Small-Scale Forestry》2018,17(4):505-522
Agroforestry is one of the most sustainable land management systems practiced around the world due to the socioeconomic benefits that it brings to farmers. In Bangladesh, farmers practice agroforestry, applying indigenous knowledge. The present study was designed to identify the present status, management practices and its role in improving the livelihoods of farmers in northern Bangladesh. Data for the study were collected through quantitative and qualitative methods. A total of 29 tree and 38 agricultural crop species were planted by the102 farmers interviewed. Mangifera indica (relative prevalence 49%) is the most predominant species, followed by Eucalyptus camaldulensis (relative prevalence 35.4%). Farmers of northern Bangladesh plant trees in cropland for fruits (90%), fuel wood (87%) and timber production (79%). Fruit trees were planted with wider spacing while forest and fuel wood species were planted with narrower spacing. Farmer’s livelihoods improved enormously by practicing agroforestry as they have more access to food, fodder and fuel wood which is reflected by greater access to livelihood capitals (except social capital). However, farmers have experienced increased incidences of pests and diseases to the annual crops and trees. Agroforestry practices increases species diversity, ensure economic return and sustain farmer’s livelihoods. 相似文献
83.
Broadening the genetic base of the C genome of Brassica napus canola by use of B. oleracea is important. In this study, the prospect of developing B. napus canola lines from B. napus?×?B. oleracea var. alboglabra, botrytis, italica and capitata crosses and the effect of backcrossing the F1’s to B. napus were investigated. The efficiency of the production of the F1’s varied depending on the B. oleracea variant used in the cross. Fertility of the F1 plants was low—produced, on average, about 0.7 F2 seeds per self-pollination and similar number of BC1 seeds on backcrossing to B. napus. The F3 population showed greater fertility than the BC1F2; however, this difference diminished with the advancement of generation. The advanced generation populations, whether derived from F2 or BC1, showed similar fertility and produced similar size silique with similar number of seeds per silique. Progeny of all F1’s and BC1’s stabilized into B. napus, although B. oleracea plant was expected, especially in the progeny of F1 (ACC) owing to elimination of the A chromosomes during meiosis. Segregation distortion for erucic acid alleles occurred in both F2 and BC1 resulting significantly fewer zero-erucic plants than expected; however, plants with?≤?15% erucic acid frequently yielded zero-erucic progeny. No consistent correlation between parent and progeny generation was found for seed glucosinolate content; however, selection for this trait was effective and B. napus canola lines were obtained from all crosses. Silique length showed positive correlation with seed set; the advanced generation populations, whether derived from F2 or BC1, were similar for these traits. SSR marker analysis showed that genetically diverse canola lines can be developed by using different variants of B. oleracea in B. napus?×?B. oleracea interspecific crosses. 相似文献
84.
【目的】 研究乙烯与1-MCP处理在7℃冷藏条件下对伯谢克辛甜瓜采后生理品质的影响,为甜瓜采后贮藏保鲜提供理论依据。【方法】 以伯谢克辛甜瓜为原料,分别采用500 mg/L的乙烯和2 μL/L 1-MCP对甜瓜进行处理,每隔24 h测定甜瓜果实硬度、呼吸强度、细胞膜渗透率、可溶性固形物、可溶性糖、还原糖、VC、可滴定酸等品质指标。【结果】 与CK相比,1-MCP可以明显降低甜瓜果实呼吸强度、细胞膜渗透率,保持甜瓜果实硬度,抑制可溶性固形物、还原糖、总糖、可滴定酸、VC含量下降,乙烯处理降低果实硬度,促进果实中可溶性固形物、糖、酸含量和VC含量的下降。【结论】 伯谢克辛甜瓜为乙烯敏感性果实,1-MCP处理能够抑制甜瓜采后呼吸作用,减缓甜瓜果实营养物质的流失,较好的保持甜瓜品质,乙烯处理提高了甜瓜的呼吸强度和细胞膜透性,降低果实硬度,加速了果实采后品质劣变及软化衰老进程。 相似文献
85.
M. Azizur Rahman 《Marine drugs》2016,14(9)
In recent years, the medicinal potential of marine organisms has attracted increasing attention. This is due to their immense diversity and adaptation to unique ecological niches that has led to vast physiological and biochemical diversification. Among these organisms, marine calcifiers are an abundant source of novel proteins and chemical entities that can be used for drug discovery. Studies of the skeletal organic matrix proteins of marine calcifiers have focused on biomedical applications such as the identification of growth inducing proteins that can be used for bone regeneration, for example, 2/4 bone morphogenic proteins (BMP). Although a few reports on the functions of proteins derived from marine calcifiers can be found in the literature, marine calcifiers themselves remain an untapped source of proteins for the development of innovative pharmaceuticals. Following an overview of the current knowledge of skeletal organic matrix proteins from marine calcifiers, this review will focus on various aspects of marine skeletal protein research including sources, biosynthesis, structures, and possible strategies for chemical or physical modification. Special attention will be given to potential medical applications and recent discoveries of skeletal proteins and polysaccharides with biologically appealing characteristics. In addition, I will introduce an effective protocol for sample preparation and protein purification that includes isolation technology for biopolymers (of both soluble and insoluble organic matrices) from coralline algae. These algae are a widespread but poorly studied group of shallow marine calcifiers that have great potential for marine drug discovery. 相似文献
86.
87.
By using Particle-Induced X-ray Emission (PIXE) technique, the effect of arsenic (As) on the mineral contents and translocation in the xylem of rice (Oryza sativa L. cv. ‘Akihikari’) was studied. The results suggest that exogenous As increased the concentrations of phosphorus (P), calcium (Ca) magnesium (Mg), sulfur (S), and manganese (Mn) in xylem, while the concentrations of potassium (K) remained unchanged. The highest concentration of As to the rice roots did not have any clear effect on the translocation of P, Ca, S, and chlorine (Cl) in the xylem, indicating that the increasing concentrations of the minerals may be due to a condensation effect, resulting from the repression of water movement in xylem by As-toxicity. Among the metal micronutrients, As decreased the concentrations and translocations of iron (Fe), zinc (Zn), and copper (Cu). 相似文献
88.
89.
Omidvar Farhadian Rahman Kharamannia Nasrollah Mahboobi Soofiani Eisa Ebrahimi Dorche 《Aquaculture Research》2014,45(7):1212-1223
Three different live diets, Eucyclops serrulatus, Ceriodaphnia quadrangula and equal combination of E. serrulatus copepodid and C. quadrangula, were offered to angelfish (Pterophyllum scalare) larvae viz 1‐week, 2‐week and 3‐week old at prey densities of 2, 5 and 10 individuals mL?1. Results showed that 1‐week‐old P. scalare larvae consumed E. serrulatus copepodid at a rate of 31.3–56.7 ind. h?1, C. quadrangula at 8.0–12.0 ind. h?1, and mixture of E. serrulatus and C. quadrangula at 20.7–40.7 ind. h?1. For 2‐week‐ and 3‐week‐old larvae, consumption rate increased accordingly. The electivity indices (E) of P. scalare (1‐week‐old larvae) for E. serrulatus copepodid were +0.18, +0.23 and +0.22 at prey densities of 2, 5 and 10 ind. mL?1 respectively. Tendency towards E. serrulatus copepodid consumption reduced by aging P. scalare as indicated by the E values for 2‐ and 3‐week‐old larvae. However, growth and survival of P. scalare larvae was greatest when fed on combination of copepod E. serrulatus and C. quadrangula. 相似文献
90.
Sajid Ali Marc Leconte Hidayatur Rahman Muhammad Shahab Saqib Pierre Gladieux Jérôme Enjalbert Claude de Vallavieille-Pope 《European journal of plant pathology / European Foundation for Plant Pathology》2014,140(2):275-290
Information on the pathogen virulence profile and diversity across locations is crucial for host germplasm improvement and deployment. The rapid acquisition of virulence to host resistance by the wheat yellow/stripe rust pathogen (Puccinia striiformis f.sp. tritici: PST), makes it crucial to know about its virulence and pathotype diversity. Recent studies have shown the plausible centre of origin of the pathogen in the Himalayan region, with Pakistan being the most ancestral to all other worldwide populations. To assess the status of virulence and pathotype diversity in the Himalayan region of Pakistan, a set of 127 PST infected wheat samples from eight locations were collected, multiplied and pathotyped using a set of 36 differential lines from the world set, European and Chinese sets, and 9 Avocet Yr isolines. Virulence (Vr) was recorded to 18 out of 24 tested yellow rust resistance (Yr) genes, while a total of 53 pathotypes were detected out of 127 isolates tested. Virulence was found to the resistance genes rarely deployed in Pakistan (Vr8) or even worldwide level (Vr5), while virulence to Vilmorin 23 (Yr3+) was absent in Pakistan, which is common in Europe. None of the pathotypes was dominant across all locations, however, no clear spatial structuring was observed for the studied locations. Our results suggested a high virulence and pathotype diversity in line with the previously proposed potential role of sexual recombination in the temporal maintenance of PST in the Himalayan region of Pakistan. This information should be useful in host resistance gene improvement and deployment. 相似文献