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:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   85篇
  免费   5篇
专业分类
林业   12篇
农学   7篇
  19篇
综合类   2篇
农作物   2篇
水产渔业   16篇
畜牧兽医   27篇
园艺   1篇
植物保护   4篇
出版年
  2023年   1篇
  2022年   6篇
  2021年   6篇
  2020年   7篇
  2018年   3篇
  2017年   7篇
  2016年   6篇
  2015年   2篇
  2014年   5篇
  2013年   4篇
  2012年   5篇
  2011年   8篇
  2010年   4篇
  2009年   2篇
  2008年   2篇
  2007年   7篇
  2006年   4篇
  2005年   2篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2001年   1篇
  1997年   1篇
  1907年   1篇
排序方式： 共有90条查询结果，搜索用时 15 毫秒
51.
Dietary supplementation (0, 10, 20, 40, 60, 80 g kg?1) of a nucleotide source (NuPro®) was evaluated on growth, nutrient utilization, haemato‐immunological responses and resistance to experimental infection of Nile tilapia. Fish (2.63 ± 0.63 g) were fed experimental diets to satiation three times a day for 75 days. Feed intake increased linearly with increasing levels of NuPro® promoting higher weight gain (P < 0.05). Survival, feed conversion and protein retention were not affected. Following the growth trial, fish were challenged with Aeromonas hydrophila by intraperitoneal injection. Survival and innate immune responses (phagocytosis and lysozyme activity) were not significantly affected. However, among the haematological variables, thrombocyte, leucocyte and monocyte counts increased linearly (P < 0.05). The indirect measurement of digestibility in juvenile Nile tilapia (122.32 ± 11 g) indicated a linear decrease in protein (1.41%), dry matter (5.72%) and energy (4.10%) digestibility coefficients as dietary supplementation increased (P < 0.05). NuPro® showed to be a beneficial additive to be supplemented in diets for juvenile Nile tilapia, providing 32.8% increase in feed intake and 28.8% in weight gain, as well as in thrombocyte, leucocyte and monocyte counts in blood, possibly indicating a more efficient defence response in the highest dietary supplementation levels tested.  相似文献   
52.
A 40-day trial was performed to evaluate the effect of short-term natural fresh food (FF) supplementation 20 days prior to ablation in Litopenaeus vannamei broodstock raised under biofloc conditions. Changes in biochemical composition and fatty acids profile were used as indicators of nutritional condition. Females that received FF supplementation (FLOC + FF) achieved better eggs production, spawned more promptly, and presented higher levels of HUFA in eggs as compared to those that did not received FF (FLOC). Proximate analysis of biofloc and microorganisms assessment showed a higher crude protein and lipid content in the FLOC + FF treatment (26.3 and 0.7 %) compared to FLOC treatment (18.4 and 0.3 %) and also demonstrated a higher concentration of filamentous cyanobacteria and nematodes. The better outcomes obtained in females that received short-term FF supplementation justified the FF use in L. vannamei broodstock.  相似文献   
53.
In a 210d experiment, the potential of biofloc technology (BFT) was evaluated for Farfantepenaeus duorarum. Water quality parameters, microorganisms profile and proximate analysis of biofloc were also assessed. BFT did not improve the growth performance in F. duorarum when compared to conventional clear-water water exchange system (final weight and survival of 13.3 g and 63.2 %; and 13.9 g and 81.4 %, respectively). Microorganism assessment suggested a higher presence of filamentous cyanobacteria followed by protozoa, nematodes and copepods. Proximate analysis of biofloc showed crude protein and crude lipid means levels of 25 and 0.6 %, respectively, and these values varied during the experiment. F. duorarum seemed to be susceptible to high stocking density and high levels of suspended solids (>15 mL L?1).  相似文献   
54.
  相似文献   
55.
Bacterium Edwardsiella ictaluri and parasite Ichthyophthirius multifiliis (Ich) are two common pathogens of cultured fish. The objective of this study was to evaluate the susceptibility of channel catfish Ictalurus punctatus to E. ictaluri and determine bacterial loads in different fish organs after parasitism by Ich. Fish received the following treatments: (1) infected by I. multifiliis at 5000 theronts/fish and exposed to E. ictaluri; (2) infected by I. multifiliis alone; (3) exposed to E. ictaluri alone; and (4) non-infected control. E. ictaluri in fish organs were quantified by quantitative real-time polymerase chain reaction and reported as genome equivalents per mg of tissue (GEs/mg). The results demonstrated that the Ich-parasitized catfish showed significantly (P<0.05) higher mortality (91.7%) when exposed to E. ictaluri than non-parasitized fish (10%). The bacterial loads in fish infected by 5000 theronts/fish ranged from 6497 to 163,898 GEs/mg which was between 40 and 2000 fold higher than non-parasitized fish (49-141 GEs/mg). Ich infection enhanced the susceptibility of channel catfish to bacterial invasion and increased fish mortality.  相似文献   
56.
A 2-year-old female mixed-breed cat weighing 2.7 kg presented with recurrent rectal prolapse. The following report describes its treatment by laparoscopic-assisted incisional colopexy using two portals. The procedure was effective and without trans- or postoperative complications. Recurrent prolapses did not recur in the 2 months of postoperative observation.  相似文献   
57.

Purpose

Brazilian soils that present extremely hard sub-superficial horizons when dry and friable when humid are similar to the Australian and South African hardsetting horizons whose hardness can be mainly related to low crystallinity. Studies involving refinement by the Rietveld method with X-ray diffraction (RM-XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and their relation have not been carried out in hardsetting horizon soils. Thus, the objective of this study is to obtain information about the kaolinite in the hardsetting horizon of a Yellow Argisol clay fraction, taking into consideration the results of isomorphic substitution, crystallite average size, and microstrains, relating them to particle image analysis regarding their morphology and size.

Materials and methods

Soil samples were collected in the hardsetting horizon of a Yellow Argisol in the Coastal Tablelands region, which covers the whole Brazilian Northeast coast and part of the Southeast region. The sample was powdered, sieved, and submitted to dispersion and physical fractioning process by sedimentation. The clay fraction was analyzed by RM-XRD, AFM, and SEM techniques.

Results and discussion

The RM-XRD provided improvement of indices with isomorphic substitutions in the goethite [Fe0.70Al0.30O(OH)], kaolinite [Al1.44Fe0.56Si2O5(OH)4], and halloysite [Al1.42Fe0.58Si2O5(OH)4]; 29 nm crystallite average size; 5 × 10?3 microstrain; and 49.5% kaolinite. AFM analyses indicated particle average size from 80 to 250 nm and average height from 60 to 80 nm. By relating this data, it was possible to estimate that the particles under analysis are kaolinite composed of 3 to 9 crystallites and stacking of 88 to 112 layers.

Conclusions

The process, analyses, and comparisons such as crystallographic and morphologic information about the kaolinite mineral particles contribute to the comprehension of the hardsetting horizon soil nature as well as other soils that present minerals with a high degree of isomorphic substitution.
  相似文献   
58.
  相似文献   
59.
Aiming to evaluate the efficacy of the treatment of canine visceral leishmaniasis, to verify the occurrence of a possible disease relapse, and to search for the presence of the parasites after the end of the treatment, seven dogs naturally infected by Leishmania (Leishmania) chagasi were used. The dogs were subjected to a treatment with 75 mg/kg meglumine antimoniate subcutaneously every 12 h for 21 days, and followed-up for a period of 6 months. During the whole experimental period the animals wore deltamethrin collars and were kept in a screened kennel to avoid reinfection. Lymph node and bone marrow aspiration biopsy was carried out to search for the parasite at seven moments: before the treatment, 30, 60, 90, 120, 150 and 180 days after the start of the treatment. After the end of the experiment all dogs were humanely euthanized. Then, spleen and liver "imprints" and in vitro cultures were carried out to search for amastigote forms of the parasite. During the treatment all animals presented remission of symptoms. However, two dogs were observed to present new symptoms in the course of the experiment. At the end of the experiment, the presence of amastigote forms of the parasite was evidenced in five of the seven dogs. This enabled us to conclude that the treatment promoted clinical cure but did not eliminate the parasites completely.  相似文献   
60.
Rhizoctonia solani AG-1 IA causes leaf blight on soybean and rice. Despite the fact that R. solani AG-1 IA is a major pathogen affecting soybean and rice in Brazil and elsewhere in the world, little information is available on its genetic diversity and evolution. This study was an attempt to reveal the origin, and the patterns of movement and amplification of epidemiologically significant genotypes of R. solani AG-1 IA from soybean and rice in Brazil. For inferring intraspecific evolution of R. solani AG-1 IA sampled from soybean and rice, networks of ITS-5.8S rDNA sequencing haplotypes were built using the statistical parsimony algorithm from Clement et al. (2000) Molecular Ecology 9: 1657–1660. Higher haplotype diversity (Nei M 1987, Molecular Evolutionary Genetics Columbia University Press, New york: 512p.) was observed for the Brazilian soybean sample of R. solani AG-1 IA (0.827) in comparison with the rest of the world sample (0.431). Within the south-central American clade (3-2), four haplotypes of R. solani AG-1 IA from Mato Grosso, one from Tocantins, one from Maranhão, and one from Cuba occupied the tips of the network, indicating recent origin. The putative ancestral haplotypes had probably originated either from Mato Grosso or Maranhão States. While 16 distinct haplotypes were found in a sample of 32 soybean isolates of the pathogen, the entire rice sample (n=20) was represented by a single haplotype (haplotype 5), with a worldwide distribution. The results from nested-cladistic analysis indicated restricted gene flow with isolation by distance (or restricted dispersal by distance in nonsexual species) for the south-central American clade (3-2), mainly composed by soybean haplotypes.  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