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   378篇
  免费   13篇
林业   5篇
农学   10篇
基础科学   1篇
  23篇
综合类   55篇
农作物   20篇
水产渔业   3篇
畜牧兽医   254篇
园艺   1篇
植物保护   19篇
  2021年   3篇
  2020年   3篇
  2017年   5篇
  2016年   10篇
  2014年   7篇
  2013年   11篇
  2012年   15篇
  2011年   16篇
  2010年   9篇
  2009年   3篇
  2008年   12篇
  2007年   13篇
  2006年   12篇
  2005年   12篇
  2004年   17篇
  2003年   11篇
  2002年   5篇
  2001年   6篇
  2000年   5篇
  1999年   7篇
  1998年   9篇
  1997年   4篇
  1996年   7篇
  1995年   4篇
  1994年   5篇
  1993年   4篇
  1992年   4篇
  1991年   15篇
  1990年   6篇
  1989年   6篇
  1988年   9篇
  1986年   6篇
  1985年   3篇
  1984年   4篇
  1983年   5篇
  1980年   4篇
  1978年   6篇
  1977年   9篇
  1975年   6篇
  1974年   7篇
  1973年   3篇
  1971年   4篇
  1970年   8篇
  1968年   3篇
  1967年   6篇
  1966年   7篇
  1965年   3篇
  1955年   3篇
  1930年   2篇
  1890年   2篇
排序方式: 共有391条查询结果,搜索用时 250 毫秒
81.
Summary The growth and feed conversion of rabbits fed either grass silage or whole grains and supplementary pelleted concentrate of cassava/cottonseed diets were investigated. Poor quality grass silage (pH 4.9) was almost completely rejected by young rabbits initially fed either 17.8 g or 35.5 g DM/day of a supplementary concentrate. Rabbits on the lower level of concentrate provision lost 0.35 g liveweight per day. Rabbits initially weighing 1.77 kg fed complete pelleted diets containing 667 g/kg maize or 667 g/kg sorghum showed improved daily liveweight gains (22.6 g) over rabbits fed whole grains and pelleted supplements (19.4 g) in an experiment lasting 40 days. In a second experiment there were no significant effects of pelleting or type of cereal on liveweight gain or feed conversion ratio. Pelleting significantly improved crude protein digestibility of diets whilst maize diets were superior in DM, organic matter and crude protein digestibilities. The inclusion of cottonseed meal containing 700 mg/kg free gossypol in diets at levels of 150 and 300 g/kg did not affect growth rate or feed conversion in rabbits weighing 0.92 kg initially. These diets contained up to 364 g/kg cassava suggesting that this ingredient can be used in rabbit diets as an energy source in replacement for whole grains.
Incorporacion De Ensilaje De Pasto, Granos Enteros De Cereales, Yuca Y Torta De Algodon En Dietas De Conejos Mantenidos En Ambientes Tropicales Simulados
Resumen Se investigó, el crecimiento y la conversión de alimentos de conejos alimentados con uno u otro de los siguientes productos: ensilaje de pasto, granos enteros de cereales, concentrado peletizado, o yuca/torta de algodón. El ensilaje de pasto de calidad baja (PH 4.9), fue rechazado casi totalmente por los conejos jovenes inicialmente, alimentados con 17.8 g. o 35.5 g. MS/día de un concentrado suplementario. Los conejos que estaban bajo una dieta más baja de concentrados, perdieron 0.35 g. de peso vivo por día. Los conejos que inicialmente pesaban 1.77 kg, los cuales fueron alimentados con dietas completamente peletizadas, que contenían 667 g/kg maíz o 667 g/de sorgo, ganaron 22.6 g. de peso vivo/día en comparación a conejos cuya alimentación consistió en gramos enteros y suplementos peletizados (19.4 g), en un experimento que duró 40 días. En un segundo experimento, no hubo efectos significativos del peletizado, o tipo de cereal, o ganancia de peso vivo, o tasa de conversión alimentaria. El peletizado en general, mejoró significativamente la digestibilidad de la proteína cruda de las dietas, mientras que las dietas de maíz fueron superiores en digestibilidad de la MS, materia orgánica y proteína cruda. La inclusión en dietas de torta de algodón con 700 mg/kg de gosipol libre, a niveles de 150 y 300 g/kg, no afectó la tasa de crecimiento o la conversión alimenticia en conejos que pesaron 0.92 kg inicialmente. Estas dietas contenían hasta 364 g/kg de yuca, sugiriendo que este ingrediente puede usarse en dietas para conejos, como fuente de energía y en reemplazo de granos enteros.

Incorporation d'Ensilage d'Herbe, De Grains Entiers De Cereales, De Farines De Manioc Et De Graine De Coton Dans La Ration De Lapins Places Dans Un Environnement Tropical Simule
Résumé On a examiné la croissance et l'indice de consommation de lapins nourris soit d'ensilage d'herbe ou de grains complets et, en supplément d'un concentré en pellets ou de rations de manioc/graine de coton. L'ensilage d'herbe de pauvre qualité (pH 4,9) est presqu'entièrement rejeté par les jeunes lapins recevant initialement un supplément concentré à 17,8 g ou 35,5 g DM/jour. Les lapins soumis au plus faible niveau de concentré perdent 0,35 g de poids corporel par jour. Dans une expérience durant 40 jours, les lapins pesant initialement 1,77 kg recevant une ration entièrement en pellets contenant 667 g/kg de maïs ou 667 g/kg de sorgho accusent un gain de poids journalier (22,6 g) par rapport à des lapins recevant des grains entiers et un supplément en pellets (19,4 g). Dans une seconde expérience, ni la pelletisation, ni le type de céréale n'ont eu d'effet significatif sur le gain de poids journalier ou l'indice de consommation. La pelletisation améliore de manière significative la digestibilité de la protéïne brute des rations alors que les rations de maïs sont supérieures en DM, matière organique et digestibilité en protéïne brute. L'incorporation dans la ration de farine de graine de coton contenant 700 mg/kg de gossypol libre au taux de 150 et de 300 g/kg n'affecte pas la croissance ni l'indice de consommation chez des lapins pesant initialement 0,92 kg. Ces rations contiennet jusqu'à 364 g/kg de manioc, ce qui permet de suggérer l'utilisation de cet ingrédient dans la nourriture des lapins en tant que source d'énergie en remplacement des grains entiers.
  相似文献   
82.
The objectives of this study were to determine effects of cyfluthrin and pyrethrin spray products, used in combination with cyfluthrin topical and ear tag applications, on bull reproductive parameters over 18 weeks. Angus or Angus x Simmental bulls were randomly assigned to one of three treatment groups: (i) no exposure to pyrethrins/cyfluthrin (CONT; n = 10), (ii) cyfluthrin ear tag and topical applications (ET; n = 10), or (iii) cyfluthrin ear tag, topical, premise spray and pyrethrin fog spray applications (ET+S; n = 8). Bull body weight was measured every 3 week, and body condition score and scrotal circumference were recorded on weeks 0, 9 and 18. Semen and serum were collected every 3 weeks for sperm evaluation and testosterone measurement, respectively. There was a treatment × week interaction (p < 0.01) for sperm with primary defects; bulls in CONT group had a greater (p = 0.01) percentage of sperm with primary defects than bulls treated with insecticides at week 18. Overall and progressive sperm motility, normal sperm morphology, secondary sperm defects and serum testosterone concentrations changed (p < 0.01) over time in all bulls; however, treatment did not affect (p ≥ 0.13) any of these parameters. There were also no treatment effects (p ≥ 0.08) on bull body weight, body condition score or scrotal circumference. The use of pyrethrin‐ and cyfluthrin‐based insecticides, regardless of application, did not negatively affect reproductive parameters in beef bulls when administered over 18 weeks.  相似文献   
83.
84.
85.
1. The effects of lighting pattern on production to 399 d in caged, female, meat‐strain chickens was investigated. Energy intake was controlled from 56 to 399 d.

2. Four different rearing treatments with a subsequent constant 16‐h photoperiod during laying were used.

3. A 15‐h rearing photoperiod resulted in delayed sexual maturity, increased mature body weight and decreases in both total egg numbers and the proportion of smaller eggs, compared with a 6‐h photoperiod.

4. Continuous light to 56 d, although associated with a high incidence of subsequent blindness, resulted in satisfactory egg production.

5. Abrupt reduction in the photoperiod from 15 to 6 h for the 112 to 167 d period resulted in unsatisfactory subsequent performance, especially when the day‐length was only slowly increased to 16 h during laying.

6. In the two laying treatments, in which the photoperiod was increased gradually from 6 to 16 h during the 168 to 238‐d period, a decrease in the number of smaller eggs occurred, compared with the treatments in which a single abrupt increase in photoperiod was used.  相似文献   

86.
87.
88.
89.
Serology has been used to diagnose retrospectively types C and D outbreaks of botulism in cattle in Australia and this study has investigated whether the approach would be applicable in England and Wales. Three hundred sera from routine surveillance submissions in England and Wales were used as a negative control population. Some stored sera were available from a small number of clinical cases of botulism and 125 samples were collected from cohort groups of clinical cases in four new outbreaks of botulism. Three of these outbreaks were identified as being caused by type D Clostridium botulinum toxin. Sera were tested by antibody ELISA in laboratories in Australia and Germany. There was no increase in the proportion of animals seropositive to type C or D antibody in the botulism-associated cattle. The proportion of samples which were seropositive to type D antibodies was <2% in both the negative control and outbreak populations. It was concluded that single time serology is unlikely to be helpful for retrospective diagnosis of outbreaks of type D botulism in England and Wales.  相似文献   
90.
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