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   291篇
  免费   3篇
  国内免费   2篇
林业   3篇
农学   2篇
  24篇
综合类   33篇
农作物   28篇
水产渔业   23篇
畜牧兽医   141篇
园艺   1篇
植物保护   41篇
  2018年   3篇
  2013年   3篇
  2011年   2篇
  2010年   5篇
  2009年   6篇
  2008年   2篇
  2007年   5篇
  2006年   6篇
  2003年   2篇
  2002年   2篇
  2001年   2篇
  1998年   3篇
  1997年   5篇
  1996年   4篇
  1995年   5篇
  1994年   6篇
  1993年   3篇
  1992年   6篇
  1991年   9篇
  1990年   5篇
  1989年   8篇
  1988年   6篇
  1987年   6篇
  1986年   12篇
  1985年   13篇
  1984年   5篇
  1983年   5篇
  1982年   9篇
  1981年   15篇
  1980年   8篇
  1979年   10篇
  1978年   6篇
  1977年   4篇
  1976年   5篇
  1975年   6篇
  1973年   4篇
  1972年   3篇
  1970年   4篇
  1968年   3篇
  1963年   4篇
  1959年   3篇
  1958年   9篇
  1957年   9篇
  1956年   5篇
  1955年   6篇
  1954年   7篇
  1953年   9篇
  1950年   4篇
  1948年   3篇
  1946年   2篇
排序方式: 共有296条查询结果,搜索用时 15 毫秒
21.
22.
Groups of chicks were infected with a virulent strain of Mycoplasma gallisepticum (MG) and treated with either danofloxacin or tylosin while one infected group was left untreated and a further group was uninfected and untreated. Control of
clinical signs and mortality was better with danofloxacin than tylosin and there
was significantly (P <0.05)greater weight gain with danofloxacin at 21 days
after infection. However ht necropsy the prevalence of lesions of the airsac walls
was similar in both groups. MG was recovered from fewer live chicks for the first
week following treatment with danofloxacin, but at 2 weeks and at necropsy, at
the termination of the experiment, it was recovered from a similar proportion of
birds in both treated groups. This was reflected also in the serological results at
the end of the trial.  相似文献   
23.
Objective- This study was designed to evaluate right-sided percutaneous endoscopic gastrostomy (PEG) as a method for creation of a permanent gastropexy.
Study Design- Percutaneous endoscopic gastrostomy adhesions were evaluated by gross examination and by mechanical testing and the results were compared with those obtained by conventional incisional gastropexy.
Animals or Sample Population- Fourteen mixed-breed dogs.
Methods- Incisional gastropexies were performed on the dogs of group one (N = 7) and PEG tubes were placed in the dogs of group 2 (N = 7). All skin sutures (group 1) and PEG tubes (group 2) were removed on day 14. The animals were maintained for an additional 44 days before euthanasia and immediate necropsy. Gastropexy adhesions were evaluated and collected for biomechanical evaluation using a materials testing machine.
Results- The duration of the procedure for group 2 was less (32.86 min ±7.65) than for group 1 (56.29 min ±8.28). The number of complications was not significantly different between group 1 and group 2 ( P =.103). Gastroperitoneal adhesions were present in 7 of 7 dogs in group 1 and 4 of 7 dogs in group 2. The adhesion lengths and widths were significantly larger in dogs in group 1 compared with those in group 2. The adhesions present in group 1 dogs sustained significantly greater tensile loads to failure (61.98 ±14.65 N), compared with the adhesions present in group 2 dogs (22.31 ±26.87 N).
Conclusions- Right-sided PEG inconsistently formed a weak gastropexy and the procedure was associated with a trend toward greater morbidity than incisional gastropexy.
Clinical Relevance- Right-sided PEG is not recommended as a means of prophylactic gastropexy.  相似文献   
24.
25.
目的 :观察抗抑郁治疗对不稳定型心绞痛伴抑郁患者近期预后的影响。方法 :将 68例不稳定型心绞痛伴抑郁的患者随机分为抗抑郁治疗组和对照组各 34例 ,治疗组在常规药物治疗基础上予心理治疗及加服抗抑郁药氟西汀 (百忧解 ) 2 0 mg/d,顿服 ,疗程为 1 2周。结果 :治疗组与对照组比较 ,心肌缺血明显改善 (P<0 .0 1 ) ,心绞痛复发率及发生急性心肌梗死比例低 (P<0 .0 5)。结论 :抗抑郁治疗能明显改善不稳定型心绞痛伴抑郁患者的近期预后。  相似文献   
26.
JONES ME 《Science (New York, N.Y.)》1963,140(3574):1373-1379
  相似文献   
27.
28.
The sensitivity of low‐field magnetic resonance (MR) T2* images for predicting the presence of meniscal lesions was determined in 12 dogs with naturally‐occurring cranial cruciate ligament rupture and three control dogs, using histopathology as the reference standard. Previously published grading systems were used to grade the severity of meniscal lesions on MR images, gross inspection and histopathology. Focal areas of increased signal intensity were detected in 11/12 symptomatic dogs and 3/3 control dogs. Lesions mimicking meniscal tears (pseudotears) were identified at junctions between meniscal margins and adjacent connective tissue in control dogs and dogs with naturally occurring disease. Histopathologic lesions were present in all menisci of both symptomatic and control dogs, including the menisci from two affected dogs that appeared grossly normal but were removed and submitted based on MR imaging findings. Histopathologic lesions identified included hyaline cartilage metaplasia and changes in the amount of ground substance and cellularity. The sensitivity of MR imaging for detecting the presence of meniscal histopathologic lesions was 90% in symptomatic dogs and 91% in control dogs. However, agreement between severity scores for the different tests was poor. Low‐field MR imaging is a sensitive test for predicting the presence but not severity of meniscal histopathologic lesions in dogs with naturally‐occurring cranial cruciate ligament rupture. Findings also supported previous studies indicating that histopathologic lesions can be present in dogs with grossly normal menisci. An improved grading system for comparing MR images and histopathologic severity of meniscal lesions in dogs is needed.  相似文献   
29.
30.
Organic matter extracted with 9 : 1 formic acid : acetylacetone from twenty-five soils of widely varying organic content and precipitated with excess di-isopropyl ether was hydrolysed with 6N HC1. The relationships between the proportions of acid-soluble N, acid-insoluble N, amino-N, and ammonium-N thus produced, and the properties of the original soil were examined. The distribution of N in acid hydrolysates was similar to that reported in the literature for material isolated by neutral and alkaline extractants. The relatively large proportion of N released as ammonium-N from organic matter obtained from soils of high pH and low C : N ratio may derive from organically fixed ammonia. The low levels of amino-N in organic matter extracted by formic acid from soils of high clay content imply the existence of clay-amino complexes that resist extraction although formation of such complexes during extraction cannot be ruled out.  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