首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   36篇
  免费   1篇
林业   4篇
农学   1篇
  8篇
综合类   1篇
农作物   4篇
水产渔业   4篇
畜牧兽医   10篇
植物保护   5篇
  2020年   1篇
  2019年   4篇
  2018年   4篇
  2017年   5篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   3篇
  2012年   6篇
  2010年   1篇
  2009年   1篇
  2007年   2篇
  2000年   2篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1977年   1篇
排序方式: 共有37条查询结果,搜索用时 15 毫秒
11.
Kisspeptins, a family of neuropeptide encoded by the Kiss1 gene, have emerged as crucial regulator of fertility and reproduction by regulating the hypothalamic–pituitary–gonadal axis. The present study was aimed to identify and associate SNPs in the KISS1 gene with reproductive traits in cattle of Indian origin. DNA samples collected from 300 individual cows of three Indian dairy breeds (Gir, Kankrej and Frieswal) of cattle were used in the study. The SNPs of KISS1 gene were identified with PCR-RFLP and sequence analysis using two sets of primer pairs. A total of 5 SNPs were identified in the targeted region of which, two were selected for screening the population and association studies. The analysis revealed that genotypes of rs442633552G>A and rs42022871C>T had a significant association with dry period. The SNP rs42022871C>T also established significant role in milk production traits, and selection of TT-genotyped animals will improve the reproduction and production potential of the animals.  相似文献   
12.
An experiment in seed morphology and seed germination techniques of Albizia procera was carried out in the nursery of the Forestry and Wood Technology Discipline,Khulna University,Bangladesh in order to discover the source variation in seeds and pre-sowing treatment effects on seed germination.Mature seeds of A.procera were collected from healthy trees in home garden plantations from five different districts in Bangladesh and treated with four pre-sowing treatments,i.e.,control,immersion in cold water (4°C for 24 h)and immersion in hot water(80°C for 10 min and 100°C for 1 min).The average length,width and thickness of seeds were calculated as 0.502±0.485,0.420±0.060 and 0.191±0.118 cm,respectively.Germination was conducted in poly-bags with a mixture of topsoil and cow dung in a ratio of 3:1.The results revealed that pre-sowing treatments affected the rate of germination of seeds,which significantly increased the germination percentages of seeds in hot water treatments compared with those in control (60.60%)and the cold water treatment(4°C for 24 h,63.53%).The highest germination success was 82.07%in the treatment of immersion in hot water(80°C)for 10 min,followed by 79.00%in immersion in hot water(100°C)for 1 min.Germination started 4 to 6 days after seed sowing and completed in a period of 22 to 25 days in all treatments.ANOVAs showed statistically significant differences(p0.05)in seed germination starting dates,closing dates,germination percentages and rates of germination among treatments,but no significant differences in seed germination starting dates,closing dates,germination period,germination percentages and rates of germination among the seed sources.The study also revealed that the interaction between seed source variation and treatment effect significantly differed in seed germination starting dates,closing dates,germination percentages and rates of germination. The hot water(100°C for 1 min)treatment is recommended for seed germination of A.procera in rural Bangladesh.  相似文献   
13.
The saturated and near‐saturated hydraulic conductivity of soils, ku, is a sensitive indicator of soil structure and a key parameter for solute transport and soil aeration. In this contribution, we present and numerically investigate a double‐disk method to determine ku in the laboratory by steady‐state percolation at different suction steps. Tension infiltration of water takes place at the top of a soil column through a porous disk with a smaller diameter than the soil sample. This leaves part of the soil surface open and ensures a proper soil ventilation. Drainage takes place at the base through a porous disk with the full diameter of the soil column at exactly the same tension as applied to the top boundary. Since the infiltration area is less than the percolation area, the water flow diverges and the equality of steady flow rate and hydraulic conductivity, which characterizes the standard unit‐gradient experiment, is no longer valid. To develop a general relationship between observed steady flow rate and unsaturated hydraulic conductivity, the experiment was simulated with the Richards‐equation solver HYDRUS 2D/3D, for twelve different soil classes. We found for tensions in the range 1 cm < 10 cm, an infiltration disk diameter of 4.5 cm diameter and a sample diameter of 8 cm diameter that the flux rate at any given tension was about 0.7 times the respective hydraulic conductivity, with an error of less than 10%.  相似文献   
14.
The development of the nematode Procamallanus saccobranchi Karve, 1952, a parasite in the stomach of the fish Heteropneustes fossilis (Bloch), was studied in Mesocyclops crassus (Fischer) and Mesocyclops leuckarti (Claus). After being ingested by the copepods the nematode first-stage larvae penetrated into the haemocoel of the intermediate host; there they moulted twice (on days 3 and 5 p.i. at 28-30 degrees C) attaining the third, infective stage. The definitive host H. fossilis acquired infection by feeding on copepods harbouring infective-stage larvae; in the stomach of this definitive host, the larvae were observed to undergo two more moults. The third moult occurred on day 13 p.i. and the fourth moult on day 38 p.i. and day 66 p.i. in "male" and "female" larvae, respectively. The larval stages, including the moulting forms are described and illustrated.  相似文献   
15.
A study was undertaken to evaluate the nutritional response of organically grown diets in buffaloes on nutrients utilization and nutrient efficiency for milk production. For this, ten milch Murrah buffaloes of average body weight (490.72?±?6.65 kg), milk yield (8.13?±?0.33 kg), and lactation stage (85?±?5.28 days) were distributed in inorganic (InDg) and organic dietary groups (OrDg) with five animals in each. Buffaloes of InDg and OgDg were fed sorghum hay–berseem fodder-concentrate mixture-based diets grown inorganically and organically, respectively. After 60 days of feeding, a digestion cum metabolism trial was conducted to assess feed intake, nutrient utilization, and N balance, while milk yield and composition were recorded fortnightly. DM, CP, digestible crude protein (DCP), and metabolizable energy (ME) intake (g/Kg w0.75) were similar in animals of InDg and OrDg. NDF, ADF, and hemicellulose digestibility were (P?<?0.05) higher in animals on OrDg (59.20, 51.55, and 62.67) than InDg diet (54.57, 43.72, and 56.61 %), respectively. Urinary n loss (g/day) was (P?<?0.05) lower in OrDg (67.23) than in InDg (83.55); however, milk N was comparable in animals of both dietary groups (47.36 vs 45.82 g/day). Nitrogen balance was higher in animals of OrDg (39.72) than in InDg (28.08). DCP, TDN, and ME values of both diets were similar. No effect of diet was observed on milk yield and its composition; however, increased lactation length decreased milk yield. Buffaloes on both diets had similar efficiency and conversion ratio of nutrients for milk production. Results revealed that diets (organically vs. inorganically grown) have no effect on milk yield and its composition; however, buffaloes on organic diet have higher fiber digestibility and low urinary N loss which did not affect the dietary nutrients efficiency and conversion ratio for milk production.  相似文献   
16.
An ecosystem model was constructed for the northern Bay of Bengal (nBoB) using Ecopath (version 6.4.4). The model covered an area of 18,500 km2. There were 32 functional groups in the model including the non-living group, detritus. Trophic levels (TLs) for individual groups ranged from 1.0 to 4.22. Ecotrophic efficiency for most of the small pelagic fishes was found to be greater than 0.7. For hilsa it was 0.853, indicating high exploitation of this fish within the system. The nBoB was estimated to be a low ascendancy area (~?19.2%) with a system overhead of 80.8%, which indicates system stability and a certain maturity. The total system throughput and the total primary production/total respiration estimated for the study area indicate that nBoB is a maturing ecosystem. The mean TL of the catch for the study area was 3.115. The results indicate that the nBoB system is still in a developing stage. The low mean TL of the catch indicates fishing practices targeting fish of lower TLs in the system. In the long run, this may cause fishing down the food web, which will eventually lead to declining catches. These results indicate that present fishing practices are unsustainable for the nBoB ecosystem.  相似文献   
17.
Incentive design is among the decisive factors behind active community participation and long-term sustainability of participatory forest management. Especially in case of mangroves, where multiple interests apply, it requires a careful integration of several ecological, economic and institutional factors. The primary objective of this paper is to understand the basis of incentive design and make a comprehensive inquiry into the existing incentive mechanism of participatory mangrove management in Indian Sundarbans. The qualitative and in-depth assessment was derived against a conceptual framework that contains three main determinants: (1) resources availability, (2) control mechanism, and (3) perception of end-users. The study deploys the results of various participatory exercises such as structured interviews with forest officials, focus group discussions with 10 Joint Forest Management Committees and semi-structured interviews with 119 mangrove users. In general, we observed an over-cautious, hierarchical and safety-margin-based incentive design with distinct bifurcation of communities over the adequacy and effectiveness of derived benefits. Although, the incentives are diverse and align well with the overall conservation of mangroves, they are considered to be insufficient by nearly half of the mangrove users. The main issues that were observed to hinder effective community participation can be summarized as (1) serious restrictions on access to economically exploitable mangrove products, (2) passive involvement of vulnerable occupational groups, and (3) lack of trust and conflicting interests between the officials and the communities. Although the existing preventive management of mangroves can be justified considering the magnanimity of the Indian Sundarbans, it can severely impair community participation and emerge as a clear threat to future sustainability. To secure greater participation of the communities, we propose small scale, innovative developmental incentives to supplement traditional forest-resource-based incentives.  相似文献   
18.
Tropical Animal Health and Production - The low potency of genetic immunization has to date impeded development of commercial vaccines against major infectious diseases. The aim of this study was...  相似文献   
19.
The kinetics of meiosis and spermiogenesis in Ascaris lumbricoides in vitro was studied by keeping 12 mature males in nutrient medium. The spermatocytes were made radioactive by supplementing the medium with 3H-thymidine for 2 h, following which they were transferred to fresh medium without 3H-TdR. The nematodes were then killed for preparing histological and squash preparations of the testis. An analysis of the migration of "hot" spermatocytes till the formation of mature spermatozoa, in Kodak AR-10 autoradiograms, suggested that the duration of meiosis and spermiogenesis was a little more than 5.5 and 7.6 days, respectively. The total duration of these two events was about 13.1 days when radioactive spermatozoa were detected for the first time.  相似文献   
20.
Nanoparticles (NPs) are emerging as a new type of contaminant in water and wastewater. The fate of titanium dioxide nanoparticles (TiO2NPs) in a granular activated carbon (GAC) adsorber and their impact on the removal of trichloroethylene (TCE) was investigated. Key parameters governing the TiO2NP?CGAC interaction such as specific surface area (SSA), zeta potential, and the TiO2NP particle size distribution (PSD) were determined. The impact of TiO2NPs on TCE adsorption on GAC was tested by conducting TCE adsorption isotherm, kinetic, and column breakthrough studies in the presence and absence of TiO2NPs. SSA and pore size distribution of the virgin and spent GAC were obtained. The fate and transport of the TiO2NPs in the GAC fixed bed and their impact on TCE adsorption were found to be a function of their zeta potential, concentration, PSD, and the nature of their aggregation. The TiO2NPs under investigation are not stable in water and rapidly form larger aggregates. Due to the fast adsorption kinetics of TCE, the isotherm and kinetic studies found no effect from TiO2NPs. However, TiO2NPs attached to GAC and led to a reduction in the amount of TCE adsorbed during the breakthrough experiments suggesting a preloading pore blockage phenomenon. The analysis of the used GAC confirmed the pore blockage and SSA reduction.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号