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   118篇
  免费   13篇
林业   15篇
基础科学   1篇
  17篇
综合类   8篇
农作物   7篇
水产渔业   21篇
畜牧兽医   58篇
园艺   1篇
植物保护   3篇
  2023年   3篇
  2022年   3篇
  2021年   5篇
  2020年   10篇
  2019年   14篇
  2018年   12篇
  2017年   6篇
  2016年   9篇
  2015年   5篇
  2014年   6篇
  2013年   8篇
  2012年   8篇
  2011年   8篇
  2010年   7篇
  2009年   3篇
  2008年   4篇
  2007年   4篇
  2006年   4篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1977年   1篇
排序方式: 共有131条查询结果,搜索用时 15 毫秒
31.
The aqueous extract of Hyptis suaveolens leaves was studied for their antinociceptive property in chemical and thermal models of nociception in mice. Oral administration of the aqueous extract (100, 200, and 400 mg/kg) dose-dependently reduced the number of writhings induced by acetic acid, decreased the licking activity of the early phase in formalin test and increased the reaction time in hot-plate test. The antinociceptive effect was significantly antagonized by naloxone (3 mg/kg; i.p.). Preliminary acute toxicity study showed that no animal death with doses up to 5 g/kg (p.o.).  相似文献   
32.
33.
This study aimed to describe the gross anatomy of the ventral rami of the thoracic spinal nerves in capuchin monkey (Sapajus apella) and compare with humans and other primate species. Eight specimens, prepared in 10% formalin solution and dissected following routine standard techniques, were used. The animals presented 13–14 pairs of thoracic spinal nerves emerging from the intervertebral foramen and divided into dorsal and ventral rami. The ventral rami of the first 12 or 13 pairs represented intercostal nerves and the latter referred to the subcostal nerve. The intercostal and subcostal nerves gave off muscular and cutaneous branches (lateral and ventral), which promote innervation of muscles and skin associated with the chest and abdominal wall. Atypical anatomy was verified for the 1st, 2nd and 7th to 13th intercostal nerves as well as for the subcostal nerve. The morphological characteristics were similar to those observed in humans and some non‐human primates, especially in the absence of collateral branches.  相似文献   
34.
There is little information regarding the nutritional requirements for dairy heifers, leading the majority of nutrient requirement systems to consider dairy heifers to be similar to beef heifers. Therefore, we evaluated the muscle protein metabolism and physical and chemical body composition of growing Holstein × Gyr heifers and estimated the energy and protein requirements. We performed a comparative slaughter experiment with 20 Holstein × Gyr heifers at an initial body weight of 218 ± 36.5 kg and an average age of 12 ± 1.0 months. Four heifers were designated as the reference group, and the 16 remaining heifers were fed ad libitum . The 16 heifers were distributed using a completely randomized design in a 2 × 2 factorial arrangement with two roughages (corn silage or sugarcane) and two concentrate levels (30 or 50%) for 112 days. Greater (p  <  0.05) values for fractional rates of muscle protein synthesis, degradation and accretion were observed for heifers that were fed 50% concentrate. The following equations were obtained to estimate the net energy for gain (NE g) and net protein for gain (NP g): NE g (Mcal/day) = 0.0685 × EBW 0.75 × EBWG 1.095 and NP g (g/day) = 203.8 × EBWG  ? 14.80 × RE , respectively, in which EBW is the empty body weight, EBWG is the empty body weight gain and RE is the retained energy. We concluded that increased rates of protein turnover are achieved when a greater quality diet is provided. In the future, these results can be used to calculate the nutritional requirements for growth of Holstein × Gyr heifers after equation validation rather than using the recommendations provided by other systems, which use values developed from beef heifers, to determine the nutritional requirements of dairy cattle.  相似文献   
35.
Lippia sidoides Cham. (Verbenaceae) is used in the folk medicine as topical antiseptic in skin and mucous membranes and its therapeutic effect is attributed to the thymol presence. The objective of this work was to verify the chemical composition and antibiotic modifying activity of the essential oil extracted from the leaves of L. sidoides and its major component thymol. The essential oil was obtained by hydrodistillation and analyzed by GC/MS. The synergistic activity was evaluated using gaseous contact method. The essential oil was obtained (yield of 1.06%) and the GC/MS analysis identified the main constituents: thymol (84.9%) and p-cymene (5.33%). The antibiotic modifying activity was verified using the minimal inhibitory dose method and gaseous contact. It verified the interference of essential oil and thymol against all tested aminoglycosides. There were no statistical differences between the activity of the essential oil and thymol against Pseudomonas aeruginosa, indicating this to be the responsible composition for such activity. However, the oil was shown more effective when compared to the thymol against Staphylococcus aureus. The essential oil of L. sidoides and its major component thymol influence the activity of aminoglycosides and may be used as adjuvant in antibiotic therapy against respiratory tract bacterial pathogens.  相似文献   
36.
Sporotrichosis is a mycosis caused by Sporothrix schenckii. The most affected animal is the cat; it has played an important role in the zoonotic transmission of this disease, especially in Rio de Janeiro, Brazil, since 1998. In order to evaluate the treatment of feline sporotrichosis with potassium iodide, an observational cohort was conducted in 48 cats with sporotrichosis at Instituto de Pesquisa Clínica Evandro Chagas, Fiocruz. All cats received potassium iodide capsules, 2.5 mg/kg to 20 mg/kg q24h. The cure rate was 47.9%, treatment failure was 37.5%, treatment abandonment was 10.4% and death was 4.2%. Clinical adverse effects were observed in 52.1% of the cases. Thirteen cats had a mild increase in hepatic transaminase levels during the treatment, six of them presented clinical signs suggestive of hepatotoxicity. Compared to previous studies with itraconazole and iodide in saturated solution, potassium iodide capsules are an alternative for feline sporotrichosis treatment.  相似文献   
37.
The Portuguese island of Selvagem Grande (Great Salvage) in Macaronesia is an important seabird breeding station in the eastern Atlantic. Significant populations of Cory's shearwater Calonectris diomedea (Scopoli, 1769), Bulwer's petrel Bulweria bulweria (Jardine & Selby, 1828) and little shearwater Puffinus assimilis baroli (Bonaparte, 1857) are present, and white-faced storm-petrel Pelagodroma marina (Latham, 1790) and Madeiran storm-petrel Oceanodroma castro (Harcourt, 1851) populations are of global significance. Selvagem Grande also provides diverse habitats for an extensive flora, including 11 endemic species. The 270-ha island was also inhabited by two alien invasive mammals: the European rabbit Oryctolagus cuniculus (Linnaeus, 1758) and the house mouse Mus musculus (Linnaeus, 1758). Both are known to have had adverse impacts on breeding seabirds and island vegetation. In 2002, the Natural Park of Madeira conducted a program using brodifacoum bait formulations aimed at rabbit and mouse eradication. Approximately 17 000 individual baiting points were established on a 12.5 × 12.5 m grid. Baits were also applied by hand “seeding” on steep slopes and cliffs where bait stations could not be placed. Rabbits were removed after a month. However, mice persisted for considerably longer and strategic bait applications against them continued for a further six months. Subsequent assessments by trapping, bait takes and systematic observation of signs over three years, has confirmed the removal of both alien invasive species. This paper presents information on these operations, on measures adopted to mitigate adverse impacts of the eradication program on important vertebrate non-target species, including Berthelot's pipit Anthus berthelotii Bolle, 1862 and a species of gecko Tarentola bischoffi Joger, 1984 and on the initial response of the island's ecosystem to the eradication of rabbits and mice.  相似文献   
38.
Drainage-weighing lysimeters allowed monitoring of water balance components of non-bearing olive (Olea europaea cv Barnea) trees over a 3-month period including short-term events of controlled but severe water stress. The objective of the study was to evaluate a variety of soil and plant-based water status and drought stress monitoring methods on the basis of tree-scale evapotranspiration (ET). As the trees entered into and recovered from water stress, meteorological data, actual ET (ETa), soil water content and changes in leaf turgor pressure were continuously monitored. Additionally, midday measurements of stem water potential, stomatal conductance, canopy temperature, and quantum yield of PSII photochemistry were conducted. Diurnal (dawn to dusk) measurements of all the above were made hourly on days of maximum stress. Shoot elongation rate was measured for periods of stress and recovery. Quantum yield of PSII photochemistry, stomatal conductance, and stem water potential all successfully indicated reductions in whole-tree water consumption beginning at moderate stress levels. These measured parameters fully recovered to the levels of non-stressed trees soon after water application was renewed. Shoot elongation was reduced 25-30% for the 10-day period during and following drought and recovered thereafter to levels of non-stressed trees. Whole-tree ETa was reduced by as much as 20% even following full recovery of the leaf level parameters, suggesting reduced canopy size and growth due to the stress period. Non-destructive, continuous (turgor pressure) and remotely sensed (canopy temperature) methods showed promising potential for monitoring effects of water stress, in spite of technological and data interpretation challenges requiring further attention.  相似文献   
39.
This study was conducted to evaluate the immunostimulating activity and growth promoting of diets supplemented with different rations of soluble and insoluble linseed fibre to Rhamdia quelen under hypoxia‐induced acute stress. For this reason, soluble and insoluble fractions of linseed fibre were concentrated separately and combined into four ratios (1:0.5; 1:1; 1:2 and 1:4), which were added to the diets of silver catfish (6.43 ± 0.12 g) and evaluated in a biological assay, along with a control diet (without addition of linseed fibre). After being fed the experimental diets for 45 days, specimens of silver catfish were submitted to hypoxia‐induced acute stress. They were kept out of water for 60 s. Immediately afterwards, blood and cutaneous mucus were collected for subsequent determination of immunological indicators and stress. After stress, the fish were weighed and measured for performance parameter calculation. The experimental design was completely randomized with five treatments and four replications. The data underwent analysis of variance and the means were compared by Tukey's test (p < .05). The fish fed diets containing the 1:2 and 1:4 soluble:insoluble fibre ratios, showed higher total protein content, globulin, plasma alkaline phosphatase activity, and performance in addition to higher mucoprotein content in the cutaneous mucus of the fish. Regardless of their ratio in the diet, linseed fibre provided higher plasma levels of total immunoglobulins and reduction in cortisol levels. The 1:1, 1:2 and 1:4 diets led to higher levels of total immunoglobulins and alkaline phosphatase activity in cutaneous mucus. The results indicate that linseed fibre has a stress‐ reduction, immunostimulant and a growth promoter effect on silver catfish. The 1:2 or 1:4 soluble: insoluble fibre ratios provided greater stimulation of the target immunological indicators and performance.  相似文献   
40.
Beef cattle (24) with an average initial body weight of 417?±?54 kg were assigned in a 2?×?2 factorial design with six repetitions. The factors studied were two levels of CP: 11 (low CP) or 13 % (high CP) in the initial feedlot phase (days 1–36) and in the final phase (days 37–72). After 36 days, half of the bulls fed with each level of CP were selected to reverse the CP level. No interaction was observed (P?>?0.05) between the level of protein in the initial and final phases on the intake of the nutrients evaluated. There was no effect (P?>?0.05) of the protein levels in the initial and final phases on intake of dry matter, organic matter, CP, non-fiber carbohydrates, and total digestible nutrients. No differences were observed among treatments (P?>?0.05) for average daily gain (X = 1.99 kg/day) and carcass traits. We conclude that it is possible to feed Holstein-Zebu crossed bulls with an average daily gain of approximately 2 kg using a fixed level of 11 % CP during the entire feedlot period, and this diet is economically viable and environmentally sound.  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