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   101篇
  免费   2篇
农学   1篇
  7篇
综合类   10篇
畜牧兽医   83篇
植物保护   2篇
  2020年   1篇
  2018年   1篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   2篇
  2012年   7篇
  2011年   1篇
  2010年   2篇
  2009年   6篇
  2008年   1篇
  2007年   6篇
  2006年   4篇
  2005年   5篇
  2004年   6篇
  2003年   2篇
  2002年   4篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   9篇
  1997年   3篇
  1996年   2篇
  1995年   2篇
  1994年   5篇
  1993年   3篇
  1992年   2篇
  1990年   3篇
  1989年   2篇
  1988年   7篇
  1987年   4篇
  1986年   1篇
排序方式: 共有103条查询结果,搜索用时 390 毫秒
1.
The right and left lungs of 5 healthy Minipigs and of 13 healthy Landrace piglets were isolated, perfused at constant pressure and maintained in an isogravimetric state under zone III conditions (pulmonary venous pressure>alveolar pressure). By applying the double, arterial and venous, occlusion technique, the total blood flow resistance (R t) was partitioned into four components: arterial (R a), pre-(R a) and post-capillary (R v) and venous (R v). The capillary filtration coefficient (K f,c) was evaluated by measuring the weight gained by the lungs when the arterial and venous pressures were suddenly increased. In the youngest Landrace piglets (5 weeks old), there was an uncontrolled vasoconstriction which sometimes prevented perfusion of the lungs and induced a large increase inR t. These high values ofR t were decreased by tolazoline administration. The values ofR t recorded in older pigs (12–13 weeks old) were lower in Minipigs (33.66±3.77 cmH2O min L–1 per 100 g of lungs;n=5) than in Landrace piglets (55.20±6.18 cmH2O min L–1 per 100 g;n=5). This breed difference was due to the differences inR a andR v. The mean values ofK f,c were 0.193±0.015 and 0.202±0.029 ml min (cmH2O)–1 per 100 g of the lungs in Minipigs and Landrace piglets respectively. All these parameters were stable for the 3 hours following the equilibrium period. It was concluded that: (1) There is an age-related maturation of the control of the vasomotor tone in porcine lungs. (2) Pulmonary microvascular haemodynamics are influenced by the breed of the pigs. (3) There was no difference in theK f,c values between both the breeds. (4) A comparison of the values reported for dogs and rabbits with our data shows that the pre- and post-capillary resistances and, to a lesser extent, the arterial and venous resistances are relatively high in pigs.  相似文献   
2.
3.
This study vividly presents results from a seasonal particulate matter measurement campaign conducted at world’s largest ship-breaking yard i.e., Alang-Sosiya (Gujarat, India) at six locations and a reference station at Gopnath which is 30 km south of this ship-breaking yard. The collected suspended particulate matter (SPM) 24-h samples were critically analyzed for heavy metals (Pb, Cd, Co, Ni, Cr, Mn, Fe, Cu, Zn). The average concentration of SPM within the ship-breaking yard during the investigation was 287.5 ± 20.4 μg m?3 and at reference station it was 111.13 ± 5.81 μg m?3. These values are found to be in excess of the permitted national standards. The levels of heavy metals at Alang-Sosiya are very high as compared to US EPA and WHO guidelines. The mean concentrations of all metals are in the order: Fe >>Zn >Cu > Mn > Cd >Pb > Co >Ni >Cr. The results on enrichment factors (EF) suggest that most of the metals in the ship-breaking yard exhibit EF values of near or above 100 which must have been comprehensively affected by ship-breaking activities. Metal data was used to evaluate the role of spatial factors on their distribution characteristics. Thereafter, factor analysis was carried out to identify the main components liable for the variance of the data set.  相似文献   
4.
During processing of the historic Comstock Ore, Virginia City, NV, an estimated 5.5 × 109 g of metallic mercury (Hg) were released into the Carson River Drainage Basin. The Bessels Mill site is one of at least 75 locations where Hg was used to amalgamate the gold and silver from the ore. Although the mill is no longer standing, Hg contaminated tailings attest to its past location. Mercury concentrations in samples of tailings from the Bessels Mill site are as high as 1570 μg/g. Mercury concentrations vary spatially over the site. Total Hg concentrations in air measured directly over the site are well above regional background levels (1 to 7.1 ng/m3). The highest average atmospheric Hg concentration measured at the site was 240 ng/m3 for October 1993. The estimated range of Hg flux to the atmosphere from the site was 37 to 500 ng/m2 hr. Atmospheric Hg concentrations varied seasonally, diurnally and spatially. Atmospheric Hg concentrations varied as a function of Hg concentration, soil and air temperature, wind speed and surface morphology.  相似文献   
5.
Five healthy Friesian calves and five double-muscled Belgian White and Blue calves were studied, using a 99m Technetium (99mTc) aerosol inhalation combined with a 99mTc macroaggregate injection and collimated scintillation counters. The inhalation-to-perfusion ratio (I/P) was calculated for both left and right sides of the thorax at four sites situated at three different levels in the auscultatory area on the same vertical axis and at a more anterior site just behind the scapulohumeral joint.I/P was higher in the left than in the right hemithorax. In both breeds, a vertical and a horizontal gradient were observed. I/P was higher in the lower and in the more cranial zones of the lungs. However the vertical gradient was more pronounced in Friesian calves while the horizontal one was greater in Belgian White and Blue animals.It was concluded that the factors affecting the topographical distribution of pulmonary ventilation and perfusion seem to be different in calves as compared to other species.  相似文献   
6.
The objective of this study was to describe a standardised and non-invasive method for exhaled breath condensate (EBC) collection in cats and to test whether determination of hydrogen peroxide (H(2)O(2)) in EBC might be used as marker of lower airway inflammation. The technique of barometric whole body plethysmography for cats was combined with a system to condense the effluent air from the plethysmograph, allowing simultaneous EBC collection and respiratory pattern measurement. H(2)O(2) was determined spectrophotometrically. Eighteen experimental cats were used to investigate the impact on EBC volume and EBC H(2)O(2) of plethysmograph ventilation rate, collection duration, sample stability, within-day and day-to-day variability. After determination of a standardised EBC collection procedure, correlation analyses between EBC H(2)O(2) and bronchoalveolar lavage (BAL) cytology of healthy and allergen-challenged Ascaris suum (AS)-sensitised cats were performed. A significant and positive correlation between EBC H(2)O(2) and bronchoalveolar lavage (BAL) neutrophil% was found in healthy cats (P < 0.001, r = 0.55), whereas in AS-sensitised cats, correlation with BAL eosinophil% was significant (P < 0.005, r = 0.61). H(2)O(2) was increased after an allergen challenge in AS-sensitised cats (n = 6, 0.56+/-0.12 versus 1.08+/-0.35 micromol/L, P < 0.05). This study proposes a non-invasive, well tolerated and repeatable method of EBC collection for cats and suggests that EBC H(2)O(2) might be used as non-invasive biomarker for monitoring lower airway inflammation.  相似文献   
7.
Field monitoring and scenario-based modelling were used to assess exposure of small ditches in the UK to the herbicide sulfosulfuron following transport via field drains. A site in central England on a high pH, clay soil was treated with sulfosulfuron, and concentrations were monitored in the single drain outfall and in the receiving ditch 1 km downstream. Drainflow in the nine months following application totalled 283 mm. Pesticide lost in the first 12.5 mm of flow was 99% of the total loading to drains (0.5% of applied). Significant dilution was observed in the receiving ditch and quantifiable residues were only detected in one sample (0.06 microg litre(-1)). The MACRO model was evaluated against the field data with minimal calibration. The parameterisation over-estimated the importance of macropore flow at the site. As a consequence, the maximum concentration in drainflow (2.3 microg litre(-1)) and the total loading to drains (0.76 g) were over-estimated by factors of 2.4 and 5, respectively. MACRO was then used to simulate long-term fate of the herbicide for each of 20 environmental scenarios. Resulting estimates for concentrations of sulfosulfuron in a receiving ditch were weighted according to the prevalence of each scenario to produce a probability distribution of daily exposure.  相似文献   
8.
Complete dynamic oxygen equilibrium curves (OEC) on dogs and cats whole blood were measured at 33, 37 and 41 degrees C. OEC were also run at three partial carbon dioxide pressures (20, 40 and 80 mmHg) as well as at five pH levels (7.2, 7.3, 7.4, 7.5 and 7.6). 2,3- diphosphoglycerate (DPG) concentrations were determined. Results were compared to those previously published in humans, using the same experimental method [Comp. Biochem. Physiol. 106 (1993) 687]. In standard conditions (pH 7.4, pCO2 40 mmHg and temperature 37 degrees C), the partial oxygen pressure at half-saturation of haemoglobin (p50) was 30.0+/-1.3 mmHg for dogs and 34.1+/-1.8 mmHg for cats. Cat's OEC was thus rightshifted compared to dog's OEC, itself rightshifted compared to human OEC. 2,3-DPG concentrations were higher in dogs than in men until they were very low in cats. Contrary to that observed in human medicine, no significant correlation was identified between standard p50 and canine 2,3-DPG values. Influence of pH, pCO2 and temperature on the OEC was saturation dependent. In dogs, Delta log p50/Delta pH was equal to -0.370, Delta log p50/Delta log pCO2 was 0.093 and Delta log p50/Delta T was 0.020. In cats, Delta log p50/Delta pH was equal to -0.405, Delta log p50/Delta log pCO2 was 0.080 and Delta log p50/Delta T was 0.016. Practically, temperature and pH variations exert a lesser influence in domestic carnivores than in humans, effect of pCO2 being similar in both.  相似文献   
9.
Three groups of five pigs were inoculated intratracheally with Escherichia coli lipopolysaccharides, and 24 hours later with 10 x 10(9) colony-forming units of a non-toxigenic strain of Pasteurella multocida type A; a fourth group was left uninoculated as controls. The three inoculated groups received either no treatment (positive controls), or were treated with 3 mg/kg ceftiofur intramuscularly once a day for five consecutive days, either alone or combined with 2 mg/kg flunixin intramuscularly once a day for three consecutive days. The sustained coughing and hyperthermia recorded in the positive controls disappeared after two days and three days of treatments, respectively, in the treated animals, and the reductions in daily weight gain and changes in breathing pattern observed in the controls were not observed in the treated animals. There were no significant differences between the pigs treated with ceftiofur alone or ceftiofur combined with flunixin. In the positive controls, the number of inflammatory cells in samples of bronchoalveolar lavage fluid continued to increase up to 15 days after inoculation, whereas in the treated animals there were similar increases at six days but the numbers had decreased to baseline levels after 15 days. Similarly, in the treated animals the volume of the lung lesions was significantly less than in the control animals, but the inclusion of flunixin in the treatment regimen had no significant additional effect.  相似文献   
10.
The objective of this study was to establish a reference base for respiratory variables (respiratory rate [R(R)], inspiratory and expiratory time [T(i) and T(e)], peak inspiratory and expiratory pseudoflow [PIF and PEF], tidal volume [V(T)], minute ventilation [V(E)] and enhanced pause [Penh]) of healthy cats by use of barometric whole body plethysmography (BWBP). Eighteen healthy European cats (10 male, 8 female) were studied from the age of 3 to 13 months in order to assess growth- and gender-related changes of BWBP variables. Chest radiographs and bronchoalveolar lavage cytology were performed to confirm pulmonary health status. Diurnal changes were investigated every 2 h over a period of 24 h when the cats were adult. V(T), V(E), PIF and PEF significantly increased during somatic growth and were higher in males than in females, whereas R(R), T(i), T(e), T(e)/T(i) ratio, PEF/PIF ratio and Penh remained unchanged and were not affected by gender. When measured over 24 h, Penh, T(e) and T(i) were significantly increased in the early morning hours (04:00 h), whereas R(R), PIF and PEF were decreased at that time. This study provides reference values of BWBP variables for healthy male and female cats and indicates when circadian changes might be observed.  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