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   213篇
  免费   20篇
  国内免费   2篇
林业   13篇
农学   13篇
基础科学   1篇
  22篇
综合类   19篇
农作物   8篇
水产渔业   9篇
畜牧兽医   130篇
园艺   5篇
植物保护   15篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   8篇
  2016年   10篇
  2015年   7篇
  2014年   6篇
  2013年   7篇
  2012年   18篇
  2011年   24篇
  2010年   3篇
  2009年   10篇
  2008年   14篇
  2007年   11篇
  2006年   16篇
  2005年   15篇
  2004年   8篇
  2003年   8篇
  2002年   12篇
  2001年   6篇
  2000年   4篇
  1999年   3篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1988年   2篇
  1985年   3篇
  1979年   1篇
  1966年   1篇
  1965年   2篇
  1945年   2篇
  1942年   2篇
  1939年   2篇
排序方式: 共有235条查询结果,搜索用时 125 毫秒
61.
Computed tomography (CT) was performed on 36 dogs with nasal aspergillosis to assess whether this imaging technique can be used to predict the success of a noninvasive intranasal infusion of enilconazole. A CT score based on the severity of the disease was given to each dog, prior to treatment, by dividing the nasal cavities and frontal sinuses into 8 anatomical regions. After therapy, the dogs were classified into 2 response groups (success group: dogs cured after 1 treatment; failure group: dogs needing more than 1 treatment or with treatment failure). No significant relationship on the logistic scale was found between the CT score and the response to treatment. High sensitivity (treatment failures correctly predicted) and specificity (treatment successes correctly predicted) could not be obtained at the same time, whatever the cut-off value chosen. The results of this study suggest that CT cannot predict the therapeutic success of nasal aspergillosis in dogs treated with a 1-hour infusion of enilconazole. However, dogs with a low score seem to be good candidates to respond after 1 treatment.  相似文献   
62.
63.
VERTEBRAL HEART SIZE RANGES SPECIFIC FOR WHIPPETS   总被引:2,自引:0,他引:2  
To assess the influence of breed, breeding lines, and training on heart size, the vertebral heart size (VHS) was evaluated on left-to-right lateral, right-to-left lateral, dorsoventral, and ventrodorsal thoracic radiographs from 44 whippets free from cardiac and pulmonary disease. In lateral views, the VHS was 11.0 +/- 0.5 vertebrae (mean +/- SD) on right-to-left lateral and 11.3 +/- 0.5 vertebrae on left-to-right lateral radiographs, being larger than the 9.7 +/- 0.5 vertebrae proposed by Buchanan (P<0.0001). The VHS on left-to-right lateral views was larger than on right-to-left lateral views (P<0.0001). The VHS was 10.5 +/- 0.6 vertebrae on dorsoventral radiographs and 11.1 +/- 0.6 vertebrae on ventrodorsal radiographs. Both values were larger than the 10.2 +/- 1.5 vertebrae (dorsoventral) (P<0.0082) or 10.2 +/- 0.8 vertebrae (ventrodorsal) (P<0.0001) proposed by Buchanan. In addition, the VHS on ventrodorsal views was larger than on dorsoventral views (P<0.0001). Dogs out of racing pedigree lines had a significantly larger VHS than those out of show pedigree lines, and trained dogs had a significantly larger VHS than nontrained dogs. Because most trained dogs came out of racing pedigree lines, and all nontrained dogs came out of show pedigree lines, however, it is difficult to determine whether the higher VHS for trained dogs is due to genetic influences or training, or both. In conclusion, it is important to take into account the breed and the radiographic view when evaluating heart size in thoracic radiographs of whippets to avoid overinterpretation of cardiac enlargement in these dogs.  相似文献   
64.
OBJECTIVE: To compare gastric emptying time, small-intestinal transit time (SITT), and orocecal transit time (OCTT) of radiopaque markers in dogs varying in age and body size and to determine whether fecal variables (ie, consistency and moisture content) are related to gastrointestinal tract transit times in dogs. ANIMALS: 24 eight-week-old female puppies, including 6 Miniature Poodles, 6 Standard Schnauzers, 6 Giant Schnauzers, and 6 Great Danes. PROCEDURE: Gastrointestinal tract transit time experiments were performed at 12, 22, 36, and 60 weeks of age. Dogs were fed 30 small radiopaque markers mixed with a meal. Abdominal radiographs were taken. The time at which 50% of the markers had left the stomach (T50) and the time at which the first marker reached the colon were calculated. Fecal moisture content and scoring on the basis of fecal consistency were recorded during the same periods. RESULTS: Puppies had a shorter mean T50 than adults, and mean OCTT decreased significantly only during growth of large-breed dogs. However mean fecal moisture content significantly increased with age, except in Giant Schnauzers. No effect of body size on T50 was found regardless of age, and no difference was observed between OCTT of small- and large-breed adult dogs. The effect of age on the mean SITT was not significant for any breed. However, a strong positive correlation was recorded between body size and fecal moisture content (r2 = 0.77) or fecal scores (r2 = 0.69) in adult dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Age affects T50 in small- and large-breed dogs and OCTT in large-breed dogs. However, body size does not affect T50 or OCTT. A relationship does not exist between gastrointestinal tract transit time and fecal variables in healthy dogs.  相似文献   
65.
OBJECTIVE: To evaluate energy expenditure (EE) in dogs by estimating rate of CO2 production (rCO2). ANIMALS: 15 Beagles. PROCEDURE: Food was withheld for 24 hours, and all dogs received an IV infusion of 13C sodium bicarbonate for 8 hours. Breath samples were collected before infusion and at 30-minute intervals from 4 to 8 hours, and 13C enrichment in breath CO2 was measured, using gas chromatography-isotopic ratio mass spectrometry. Food was withheld from 6 dogs, and rCO2 and O2 consumption were measured, using a conventional indirect calorimeter. The CO2 production and O2 consumption were measured by use of indirect calorimetry in 6 other fed dogs that were injected with 2H2O and H2(18)O. Blood samples were collected before tracer injection, 4 hours later, and on days 4, 7, and 11. Deuterium and 18O enrichments in plasma water were determined. RESULTS: Mean rCO2 measured by indirect calorimetry was 516 +/- 34 and 410 +/- 16 micromol/kg(0.75)/min in 6 fed and 6 food-deprived dogs, respectively. The rCO2 calculated from 13C-bicarbonate dilution was 482 +/- 30 micromol/kg(0.75)/min. Mean rCO2 determined by use of the double-labeled water method was 1,036 +/- 46 mmol/kg(0.75)/d. Mean energy expenditure calculated from rCO2 determined by infusion of 13C bicarbonate, indirect calorimetry in fed and food-deprived dogs, and infusion of double-labeled water was 386 +/- 39, 379 +/- 25, 338 +/- 14, and 552 +/- 25 kJ/kg(0.75)/d, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Energy expenditure calculated by indirect calorimetry in unfed dogs can be considered representative of basal metabolic rate.  相似文献   
66.
The relationships between the herd-somatic-cell count (SCC) pattern on a test day and the incidence of clinical mastitis in the subsequent period were studied by collecting health data and monthly records from 2 years (1995-1997) from 121 farms located in the west of France. A total of 980 herd-periods (from one test day to the following one) were analyzed. The outcome variable was the incidence density of clinical mastitis (ICM) within the herd-period. The herd-SCC pattern on a test day was described by cross-combining the proportions of cows with low SCC (<50,000 cells/ml) or with high SCC (>250,000 cells/ml). The relationship between herd-SCC pattern and subsequent ICM was assessed using a generalized linear mixed model. A sensitivity analysis evaluated the effect of different proportions of cows with low SCC on significance and magnitude of the relationship. Risk of clinical mastitis was expressed as a risk ratio (RR) in comparison to a moderate herd-SCC level (with low proportions of cows with low or high SCC).Median ICM was 0.38 cases per 365 cow-days at risk (first and third quartiles: 0 and 0.88). In the situations where few cows (<15%) had SCC>250,000 cells/ml, ICM was higher (RR>1.31) when the proportion of cows with low SCC exceeded 50% than in the reference situation. Risk ratios increased as the proportion of cows with low SCC increased from 40 to 60%. In the situations where the proportion of cows with SCC>250,000 cells/ml exceeded 15%, ICM was higher compared to the reference situation (whatever the proportion of low SCC). Risk ratios were also higher when the proportion of cows with low SCC were >40-60%, compared to the pattern with the proportion of cows with low SCC below 40%. Herd situations with a high proportion of cows with low SCC appeared to be at increased risk of clinical mastitis.  相似文献   
67.
Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.  相似文献   
68.
Spinal tumoral calcinosis is reported in a Berner sennenhund puppy. The condition was manifested clinically as a non-ambulatory tetraparesis associated with neck pain. On survey radiographs there was a focal calcified mass at the atlantoaxial articulation. Computed tomography and computed tomographic myelography gave additional information on the extent of the mass and on the degree of spinal cord compression. The mass was removed surgically and the dog made a complete recovery.  相似文献   
69.
70.
Résumé Dans cette étude, l'auteur passe successivement en revue l'origine et l'introduction aux Antilles françaises duDigitaria decumbens Stent ditpangola, native d'Afrique du Sud, importée de PortoRico en Mars 1949 à la Guadeloupe à la Station d'Amélioration des Plantes du Centre de Recherches Agronomiques des Antilles, sur le Domaine de Duclos, à Petit-Bourg (Guadeloupe), puis de là à la Martinique, à Marie-Galante, etc ...Les conditions écologiques et l'intérêt fourrager sont ensuite examinés dans le cadre des Antilles françaises. Le comportement de cette plante à l'égard du facteur micro-climatique est indiqué avec quelques détails: température comprise entre 20 et 30 degrés Centigrades (68 à 86 °F), avec une moyenne de 25° C (77 °F); précipitations annuelles de 1000 mm. à 4000 mm, avec une biologie optimale de 2500 mm sur 140 jours, une altitude de 0 à 500 m (optimale à 120 m). L'insolation, fonction des heures de lever et de coucher du soleil est prise en considération.L'adaptation à l'égard du facteur édaphique est précisée: amplitude large vis-à-vis de la composition chimique, la structure physique et la constitution biologique du milieu: plante euryonique (PH de 4,3 à 8,6).Les conditions sociologiques et agronomiques des pâtures à pangola: association en mélange fourrager avec une ou plusieurs Légumineuses, fertilisation avec N,P,K, et Ca, formes à apporter et doses; quotientCa/P; carences, conditions de propagation, aptitude à la colonisation et la repousse sous la dent du bétail, comportement sanitaire, sont ensuite définis, permettant de conclure à l'intérêt exceptionnel de cette Graminée si difficile à suppléer éventuellement aux Antilles françaises.
Summary The author reports on origin and introduction ofDigitaria decumbens Stent var.pangola on the French Antilles. This plant is growing in South Africa, and was imported from Porto-Rico via Guadeloupe (Station for Plant Breeding) to Martinique in March 1949. Ecological conditions and qualification as forage plant in the area of the French Antilles have been studied. The reaction of these plants to microclimatic conditions is shown by the following statements: Required temperature between 20 to 30 °C (68 – 86° F), yearly precipitations 1000 to 4000 mm — with a biological optimum of 2 500 mm during a period of 140 days — at a height of 0 to 500 m (optimal at 120 m). Insolation in correspondence with sunrise and sunset has also been considered.The edaphical conditions for the plant were precised. The wide range of the chemical conditions of the soil, the physical structure, and the biological properties of the environment apply to an euryonical plant (pH of 4,3 to 8,6).The following sociological and agricultural properties of thepangola are to ascertain:The socialization in forage mixtures with one or more leguminous plants; kind and amount of fertilization with N,P,K, and Ca; the quotient Ca/P; deficiences, propagation; adaptation to cultivation and recovery of growth after grazing by cattle. This will allow a conclusion on the suitability of this graminee as forage plant on the French Antilles.

Zusammenfassung Der Autor berichtet über Ursprung und Einführung vonDigitaria decumbens Stent var.pangola auf den französischen Antillen. Diese Pflanze ist in Süd-Afrika beheimatet, wurde im März 1949 von Porto-Rico über Guadeloupe (Station für Pflanzenzüchtung) nach Martinique eingeführt. Ökologische Voraussetzungen und Eignung als Futterpflanze im Bereich der französischen Antillen wurden geprüft. Das Verhalten dieser Pflanze gegenüber mikroklimatischen Bedingungen wird durch folgende Angaben belegt: Erwünschte Temperaturen zwischen 20 bis 30 °C (68 – 86 °F), jährliche Niederschläge 1.000 bis 4.000 mm — mit einem biologischen Optimum von 2.500 mm während einer Zeit von 140 Tagen — bei einer Höhenlage von 0 bis 500 m (optimal bei 120 m). Sonneneinstrahlung in Abhängigkeit von Sonnenaufgang und Sonnenuntergang wurde ebenfalls in die Betrachtung einbezogen.Die edaphischen Bedingungen für die Pflanze wurden präzisiert. Die weite Spanne hinsichtlich der chemischen Bodenbeschaffenheit, der physikalischen Struktur und der biologischen Eigenschaften des Milieus deutet auf eine euryonische Pflanze (pH von 4,3 bis 8,6) hin.Folgende soziologischen und landwirtschaftlichen Kriterien der Pangola-Weide sind zu ermitteln:Vergesellschaftung im Futtergemisch mit einer oder mehreren Leguminosen; Art und Menge der zu verabfolgenden Düngung mit N,P,K und Ca; der Quotient Ca/P; Mangelerscheinungen, Vermehrung, Anpassung an Kultivierung und an Nachwachsen als Folge von Verbiß nach Beweidung durch Großvieh, sanitäres Verhalten. Dadurch soll ein Schluß über die Eignung dieser Graminee als Futterpflanze auf den französischen Antillen gezogen werden.


Congrès International de la Recherche Agronomique.Surinam. Nov.–Déc. 1963.  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