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   123篇
  免费   9篇
林业   7篇
农学   1篇
综合类   20篇
农作物   4篇
水产渔业   4篇
畜牧兽医   89篇
园艺   2篇
植物保护   5篇
  2023年   2篇
  2022年   1篇
  2020年   2篇
  2019年   2篇
  2018年   3篇
  2017年   4篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   10篇
  2012年   3篇
  2011年   1篇
  2010年   5篇
  2009年   6篇
  2008年   1篇
  2007年   7篇
  2006年   8篇
  2005年   5篇
  2003年   8篇
  2002年   2篇
  2001年   3篇
  2000年   1篇
  1999年   4篇
  1998年   4篇
  1997年   14篇
  1996年   2篇
  1995年   5篇
  1994年   4篇
  1993年   4篇
  1992年   7篇
  1991年   2篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1985年   1篇
  1971年   1篇
排序方式: 共有132条查询结果,搜索用时 15 毫秒
51.
The objectives of this study were to determine pharmacokinetics of intravenous (i.v.) ceftiofur in foals, to compare ultra-high performance liquid chromatography tandem mass spectometry (UPLC-MS/MS) and microbiologic assay for the measurement of ceftiofur concentrations, and to determine the minimum inhibitory concentration ( MIC ) of ceftiofur against common equine bacterial pathogens. In a cross-over design, ceftiofur sodium was administered i.v. to six foals (1–2 days-of-age and 4–5 weeks-of-age) at dosages of 5 and 10 mg/kg. Subsequently, five doses of ceftiofur were administered i.v. to six additional foals between 1 and 5 days of age at a dose of 5 mg/kg q 12 h. Concentrations of desfuroylceftiofur acetamide (DCA), the acetamide derivative of ceftiofur and desfuroylceftiofur-related metabolites were measured in plasma, synovial fluid, urine, and CSF by use of UPLC-MS/MS. A microbiologic assay was used to measure ceftiofur activity for a subset of plasma samples. Following i.v. administration of ceftiofur at a dose of 5 mg/kg to 1–2 day-old foals, DCA had a t ½ of 7.8 ± 0.1 h, a body clearance of 74.4 ± 8.4 mL/h/kg, and an apparent volume of distribution of 0.83 ± 0.09 L/kg. After multiple i.v. doses at 5 mg/kg, DCA concentrations in CSF were significantly lower than concurrent plasma concentrations. Ceftiofur activity using a microbiologic assay significantly underestimated plasma concentrations of DCA. The MIC of ceftiofur required to inhibit growth of 90% of isolates of Escherichia coli , Pasteurella spp, Klebsiella spp, and β-hemolytic streptococci was <0.5 μg/mL. Intravenous administration of ceftiofur sodium at the rate of 5 mg/kg every 12 h would provide sufficient coverage for the treatment of susceptible bacterial isolates.  相似文献   
52.
Objective To determine whether particular genotypes of Babesia bovis were common to field isolates obtained from cattle properties in Queensland where the B bovis vaccine had apparently failed.
Design A comparative study of polymerase chain reaction genotypes in different populations of B bovis .
Procedure Two polymerase chain reaction assays were applied to analyse DNA extracts of B bovis vaccine (K, T and Dixie strains) and 27 field isolates from 24 properties where disease outbreaks had occurred despite the use of the vaccine. To evaluate the stability of the genotypes identified, 11 of the field isolates were inoculated into experimental cattle that had either been previously vaccinated with T strain or not vaccinated.
Results No particular genotype of B bovis was responsible for the problems observed in previously vaccinated herds. None of the isolates had genotypes identical to the vaccine strains used. No geographic trends among the genotypes were observed. Isolates that originated from the same property also had different genotypes. Blood passage of the 11 field isolates in either previously vaccinated or nonvaccinated cattle did not alter the original genotype.
Conclusion No particular genotypes identified by the Bv80 and BvVA1 polymerase chain reaction assays could be associated with vaccine failures.  相似文献   
53.
The analgesic, bleeding, and renal effects of dogs pre‐medicated with etodolac with and without butorphanol were evaluated. Twenty‐four 1‐year‐old healthy dogs, weighing 19 ± 3 kg (mean ± SD) were randomly assigned to four treatment groups (n = 6): control (C), etodolac (E), butorphanol (B), and etodolac with butorphanol (EB). Etodolac (12–14 mg kg?1 PO) was given 1 hour before propofol induction and isoflurane maintenance anesthesia. Butorphanol (0.4 mg kg?1 IV) was given immediately following endotracheal intubation. Control dogs received only propofol (8 mg kg?1 to effect) and isoflurane anesthesia. All dogs were mechanically ventilated to maintain Pe ′CO2 between 35 and 45 mm Hg (4.7–6.0 kPa). Lactated Ringer's solution was given at 10 mL kg?1 hour?1 during anesthesia. Plasma cortisol concentrations were assessed 1 day prior to surgery (baseline), immediately prior to anesthesia induction, and every 30 minutes until 5 hours following extubation, and 1 day after surgery. Total duration of anesthesia was 50 minutes and total surgery duration was 30 minutes. Isoflurane concentration area under the curve (AUC) over time during the anesthesia was compared among treatment groups. Buccal mucosal bleeding time (BMBT) was assessed 1 day before E administration and during surgery. Urine GGT to urine creatinine ratio, BUN, and plasma creatinine were taken daily from 1 day before to 3 days after surgery. Behavioral pain scores (numerical rating scale) were assessed by two observers blinded to the treatment during the 5‐hour recovery period at 30 minute intervals until 3 hours, and again at 5 hours after extubation. All data were analyzed using anova . Multiple comparisons were performed if the anova was significant. Alpha value was set at 0.05. Plasma cortisol concentrations significantly increased from time of extubation in all the treatment groups. They did not return to the baseline until 5, 2.5, 1.5, and 1.5 hours after extubation in the C, B, E, and EB groups, respectively. Isoflurane AUC was not significantly different among treatment groups. Dogs treated with EB had significantly less behavioral pain than all other groups throughout the 5‐hour recovery period. No significant difference was found between treatment groups or within treatment groups over time in BMBT, or any renal variables. This study demonstrated that (i) pre‐operative administration of E provides profound analgesia during the post‐operative period without renal or bleeding side‐effects in dogs undergoing OHE; and (ii) a combination of butorphanol–etodolac provides the best analgesic effect during the post‐operative period based on the behavioral pain score.  相似文献   
54.
55.
56.
Crystalline Ropes of Metallic Carbon Nanotubes   总被引:7,自引:0,他引:7  
Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.  相似文献   
57.
Acepromazine, a phenothiazine tranquilizer, causes hypotension in standing horses ( Parry et al. 1982 ). However, a retrospective study ( Taylor & Young 1993 ) showed that acepromazine pre‐anesthetic medication did not affect arterial blood pressure (MAP) in anaesthetized horses. This study examined the effects of acepromazine on MAP during romifidine–ketamine–halothane anaesthesia in horses anaesthetized for various surgical procedures. Forty‐four horses were allocated by block randomization to groups A and B. Group A received acepromazine 0.05 mg kg?1 IM 30 minutes before induction of anaesthesia, group B did not. All horses received romifidine 0.1 mg kg?1 IV 5 minutes before anaesthesia was induced with diazepam 0.05 mg kg?1 and 2.2 mg kg?1 ketamine IV. The horses' trachea were intubated and horses breathed 50% oxygen and 50% nitrous oxide plus halothane (concentration adjusted as required clinically) from a circle breathing system. Nitrous oxide was discontinued after 10 minutes and analgesics, flunixin 1.1 mg kg?1 and either morphine 0.1 mg kg?1 or butorphanol 0.05 mg kg?1 (matched for horses undergoing the same procedure) administered IV. The facial or dorsal metatarsal artery was catheterized for direct measurement of MAP (every 10 min) and withdrawal of blood for gas analysis (every 30 min). The electrocardiogram (ECG) was monitored continuously with a 10 seconds printout obtained every 10 minutes. Intermittent positive pressure ventilation (IPPV) was instigated if PaCO2 exceeded 9.3 kPa (70 mm Hg). Dobutamine was infused (1.0–5.0 kg?1minute?1) if MAP < 58 mm Hg and was continued until MAP > 70 mm Hg. Mean age, weight and duration of anaesthesia were compared between the groups using a t‐test for independent samples. Gender distribution and numbers of horses requiring IPPV or dobutamine were compared between groups using a chi‐squared test (with Yates correction). To compare MAP over time, the area under the curve (MAPAUC) was calculated and compared between groups using a t‐test. Horses receiving dobutamine were excluded from MAPAUC and MAP comparisons. The ECG printouts were examined for arrhythmias. There were no significant differences between groups (p > 0.05). Group A contained three stallions, 10 geldings and nine mares, aged 6.3 years (range 0.75–18). Group B comprised eight stallions, 11 geldings and three mares aged 7.3(1–16) years. Duration of anaesthesia was group A 97 (50–140) minutes, group B 99 (50–160) minutes. Eight horses in group A and three in group B required IPPV. Nine horses in group A and four in group B received dobutamine. Mean arterial pressure ranged from 60 to 128 mm Hg in group A and 58–96 mm Hg in group B. Mean MAPAUC was 5941 mm Hg minute?1 in group A, in B 6000 mm Hg minute?1. Atrial pre‐mature complexes were recorded from one horse in group B. No other arrhythmias were detected. Although MAP was lower in the acepromazine group, this appeared unlikely to cause a clinical problem. The incidence of arrhythmias was too low to determine the influence of acepromazine in this study.  相似文献   
58.
Abstract  Data on the genetic characteristics of the rhodanian shad, Alosa fallax rhodanensis Roule, using three Mediterranean populations (rivers Rhône, Aude and Hérault) and seven protein markers are presented. Allelic frequency distribution, and absolute and relative genetic diversity show a genetically homogeneous structure in the Mediterranean populations. Results when compared with allis ( Alosa alosa Linné) and twaite ( Alosa fallax fallax Lacépède) shad Atlantic populations confirm that the Rhodanian shad belongs to the Alosa fallax Roule species. Furthermore, genetic characteristics of the twaite shad Mediterranean group were quite different from Atlantic populations but remained close to the most southern Atlantic population in the Oued Sebou (Morocco). These findings suggest that Rhodanian shad should be considered a well identified homogeneous group within Alosa fallax rather than a subspecies because of the low genetic distance and some relatively different biological characteristics between the Atlantic and Mediterranean twaite shad groups.  相似文献   
59.
ABSTRACT

Aims: To examine the relationship between liveweight (LWT) at 12 months as a proportion of LWT at 21 months of age (LWT(12/21)%) and first lactation and cumulative 3-year milk production in dairy heifers in New Zealand.

Methods: Liveweight and milk production records were obtained for dairy heifers born from June to December (spring-calving season) between 2006–2007 and 2013–2014 dairy seasons; production records included first lactation (n?=?140,113) and cumulative 3-year (n?=?67,833) milksolids and energy-corrected milk (ECM) yields. Heifers were classified into five breed groups; Holstein-Friesian, Holstein-Friesian crossbred, Jersey, Jersey crossbred and Holstein-Friesian-Jersey crossbred. Within each breed group heifers were categorised into quintiles based on 21-month LWT. The LWT(12/21)% was calculated for each animal. Relationships between LWT(12/21)% and milk production within each breed group and LWT category were estimated using linear mixed effects models including the linear and quadratic effects of LWT(12/21)%.

Results: The relationship between LWT(12/21)% and milk production was predominantly curvilinear, with lower milk production at lesser LWT(12/21)% compared with greater LWT(12/21)%. For all breed groups and most LWT categories, heifers that were 55 or 65% LWT(12/21)% produced greater ECM and milksolids yields compared with heifers that were 45% LWT(12/21)%. Holstein-Friesian, Holstein-Friesian crossbred and Holstein-Friesian-Jersey crossbred heifers that were 65% LWT(12/21)% produced greater cumulative 3-year ECM and milksolids yields compared with heifers of the same breed group that were 45% LWT(12/21)%

Conclusions and clinical relevance: Heifers that were a greater proportion of their 21-month LWT at 12 months of age produced more first lactation and cumulative 3-year milk yields than heifers that were a lesser proportion of their 21-month LWT at 12 months of age. These results indicate that increased growth in early life of New Zealand dairy heifers is beneficial to future milk production.  相似文献   
60.
Objective— To determine outcome after medical or surgical treatment of postpartum mares with confirmed or presumptive uterine tears. Study Design— Case series. Methods— Postpartum mares were included if foaling had occurred within 7 days and uterine tear was confirmed surgically or, in medically treated mares, by palpation or presumed based on peritonitis. Information (age, breed; physical examination, laboratory and abdominocentesis findings; treatment, survival rates, length of hospital stay, treatments costs, and breeding performance after discharge) was obtained from the medical records (1990–2007). The influence of variables was compared between medical and surgical treatment, and between survivors and nonsurvivors. Results— For 49 mares, survival was 75%, with no significant difference between medical (11/15; 73%) or surgical (26/34; 76%) treatment. Admission variables, treatment cost, duration of hospital stay, and likelihood of foaling after discharge were not significantly different between treatment groups. Nonsurvivors were significantly more likely to have gastric reflux, higher heart rate, anion gap, lower total CO2, and leukocyte count, compared with survivors. Tears were significantly (P=.018) more likely to occur in the right uterine horn than in other parts of the uterus. Conclusions— Uterine tears occur more commonly in the uterine horns, more so the right horn, and survival is similar with surgical or medical treatment of uterine tears in postpartum mares. Clinical Relevance— Medical treatment may be a reasonable alternative to surgical treatment for uterine tears, although the severity of tear that can resolve with medical treatment is unknown, and medical therapy can be as expensive as surgical treatment.  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