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71.
This study analysed buffaloes from north‐east India and compared their nuclear and mitochondrial DNA variations with buffaloes of mainland India, China, Mediterranean and South‐East Asia. Microsatellite genotypes of 338 buffaloes including 210 from six north‐east Indian buffalo populations and three mainland Indian breeds were analysed to evaluate their genetic structure and evolutionary relationships. Phylogenetic analysis and multidimensional scaling plot of pairwise FST revealed the clustering of all swamp‐type buffaloes of north‐east India with Lower Assamese (significantly hybrid type) buffaloes in one plane and all the mainland river buffaloes in another plane while the upper Assamese buffaloes being distinct from both these clusters. Analysis of mtDNA D‐loop region of 530‐bp length was performed on 345 sequences belonging to 23 buffalo populations from various geographical regions to establish the phylogeography of Indian water buffalo. The swamp buffaloes of north‐east India clustered with both the lineages of Chinese swamp buffalo. Multidimensional scaling display of pairwise FST derived from mitochondrial DNA data showed clustering of upper Assamese, Chilika and Mediterranean buffaloes distinctly from all the other Indian buffalo populations. Median‐joining network analysis further confirmed the distinctness and ancestral nature of these buffaloes. The study revealed north‐east region of India forming part of the wider hybrid zone of water buffalo that may probably extend from north‐east India to South‐East Asia.  相似文献   
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The amount of water used by any crop largely depends on the extent to which the soil water depletion from the root zone is being recharged by appropriate depth of irrigation. To test this hypothesis a field study was carried out in November–March of 2002–2003 and 2003–2004 on a sandy loam (Aeric haplaquept) to quantify the effect of depth of irrigation applied through micro-sprinklers on onion (Allium cepa L.) bulb yield (BY) and water use patterns. Seven irrigation treatments consisted of six amounts of sprinkler applied water relative to compensate crop (Kc) and pan (Kp) coefficient-based predicted evapotranspiration loss from crop field (ETp) (i) 160% of ETp (1.6ETp); (ii) 1.4ETp; (iii) 1.2ETp; (iv) 1.0ETp; (v) 0.8ETp; (vi) 0.6ETp; (vii) 40 mm of surface applied water whenever cumulative pan evaporation equals to 33 mm. Water use efficiency (WUE), net evapotranspiration efficiency (WUEET) and irrigation water use efficiency (WUEI) were computed. Marginal water use efficiency (MWUE) and elasticity of water productivity (EWP) of onion were calculated using the relationship between BY and measured actual evapotranspiration (ETc). Yield increased with increasing sprinkler-applied water from 0.6 to 1.4ETp. Relative to the yield obtained at 0.6ETp, yield at 1.0ETp increased by 23–25% while at 1.4ETp it was only 3–9% greater than that at 1.0ETp. In contrast, yield at 1.6ETp was 9–12% less than that at 1.4ETp. Maximum WUE (7.21 kg m−3) and WUEET (13.87 kg m−3) were obtained under 1.0ETp. However, the highest WUEI (3.83 kg m−3) was obtained with 1.2ETp. The ETc associated with the highest WUE was 20% less than that required to obtain the highest yields. This study confirmed that critical levels of ETc needed to obtain maximum BYs, or WUE, could be obtained more precisely from the knowledge of MWUE and EWP.  相似文献   
75.
Fusarium equiseti is prevalent in ginseng soil, straw mulch and in ginseng root tissues and is the cause of a root surface discolouration on ginseng grown in British Columbia. Population levels of the fungus in ginseng fields ranged from 3.8 × 103 cfu g−1 soil to 1.4 × 104 cfu g−1 soil and were highest at 0–5 cm soil depths compared to 10–15 cm. Soil population levels were negatively correlated with S content in soil and positively correlated with Zn levels. Barley or wheat straw added to soil significantly increased population levels under laboratory conditions. Mycelial growth in culture was highest at 26–30°C and at pH 7.2–7.8. Samples of flowers and berries, and harvested seed, contained DNA of F. equiseti detected using a Fusarium-specific DNA array and the fungus was isolated from these tissues on agar medium. A high degree of genetic variation in the EF-1 alpha gene sequence was present among 52 isolates of F. equiseti which originated from ginseng fields. At least seven clades were identified. Inoculum dispersal from straw mulch used in ginseng gardens can result in seed contamination by the fungus. In addition, fungal growth near the soil surface under warm summer conditions can result in infection and crown discolouration of ginseng roots.  相似文献   
76.
Tea is an evergreen shrub, and tea bushes (plants) are periodically pruned at 3-year intervals. This practice generates tons of pruning litters (leaves and stems) in tea gardens. In spite of availability, the hard nature and slow decomposition rate limit the use of pruning litters as soil amendments. In this study, an attempt was made to cycle pruning litters in shredded form to evaluate their effect on young tea plants under greenhouse condition. It was observed that shredded prunings were decomposed in soil within study duration and enhanced nitrate-N content in the soil. The study revealed that different parameters like plant height, biomass weight, and N uptake were enhanced due to the application of suitable combinations of pruning litter and urea in the soil. Based on this study, it could be concluded that application of shredded prunings had potential to replace up to 15% of recommended urea during tea cultivation.  相似文献   
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Modern research on the insecticidal effects of inert dusts as a stored-grain protectant and for plant protection purposes began in the 1920s. The main advantage of inert dusts is their low-mammalian toxicity. One group of inert dusts used for pest control is diatomaceous earth (DE). DE has been tested as a whole and evaluated as a Group 3 carcinogen by the International Agency for Research on Cancer (IARC). A Group 3 listing indicates that DE is not classifiable as to its carcinogenicity to humans, since definitive conclusions cannot be drawn from the research conducted to date. DE is a form of naturally occurring amorphous silica that can kill insects by ab/adsorbing the lipids such as waxes and triglycerides of the outer cuticle layer by direct contact. When the thin, waterproof layer is lost, the insect looses water and dies. Desiccation follows Ficks law of diffusion into the surrounding atmosphere. In addition to its desiccant action the theory that DE works abrasively to rupture insect cuticles has been proposed. To evaluate the abrasive effects of DE we have tested 27 inert dusts with different surface properties. Materials were compared based on the time needed to kill 50% (LT50) of Sitophilus granarius weevils in laboratory experiments. Substances with hydrophilic and/or hydrophobe properties were significantly more effective against S.?granarius than substances which are mainly abrasive. There is a strong correlation between LT50 and weight loss (=?water loss) of insects (p?=?0.014). Particle size played only a secondary role (p?=?0.077). Commercial DE formulations and activated charcoal (Carbopal MB4) were the most effective hydrophilic substances tested. The most abrasive substances were corundum and silica sand with small particle sizes. It is concluded, that those materials were effective because of a good coverage of the insects outer cuticle and existing shear stress. All results presented are discussed in context of the insecticidal mode of action of inert dusts and possible registration of silica based formulations as biocide.  相似文献   
79.
基于POE的动力学建模与快速非奇异终端滑模控制   总被引:1,自引:0,他引:1  
结合旋量指数积形式(POE)和凯恩方程的优点,提出了一种具有明显几何意义的高效动力学建模方法,并以此为基础提出机器人系统的快速非奇异终端滑模控制算法。凯恩方程中的偏速度选择为基于旋量理论描述的合适的物体雅可比矩阵,并以此定义其他动力学模型参数表达方式,且在"钱江一号"串联机器人上进行建模实例验证。基于该动力学模型,为了改善传统滑模控制的有限时间收敛特性,保证全局控制非奇异性,提出了一种快速全局非奇异终端滑模控制,通过构造带状态高次项的滑模面函数,得到全局非奇异控制,并保证系统从任意状态到达滑模面的时间和在滑模上到达平衡点的时间均为有限且快速收敛,通过李雅普诺夫函数证明了其稳定性,并结合对比实验,验证了该方法在机器人系统中的鲁棒性和有效性。  相似文献   
80.
Genetic Resources and Crop Evolution - Rapeseed-mustard is one of the most important oilseed crops and providing a major source of edible oil in the world besides having other economic importance...  相似文献   
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