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   520篇
  免费   5篇
  国内免费   3篇
林业   16篇
农学   1篇
  29篇
综合类   197篇
农作物   6篇
水产渔业   4篇
畜牧兽医   262篇
园艺   2篇
植物保护   11篇
  2013年   5篇
  2012年   19篇
  2011年   38篇
  2010年   4篇
  2009年   3篇
  2008年   23篇
  2007年   35篇
  2006年   21篇
  2005年   21篇
  2004年   29篇
  2003年   28篇
  2002年   33篇
  2001年   18篇
  2000年   24篇
  1999年   16篇
  1998年   5篇
  1997年   11篇
  1995年   3篇
  1994年   10篇
  1992年   7篇
  1991年   10篇
  1990年   11篇
  1989年   6篇
  1988年   4篇
  1986年   3篇
  1985年   7篇
  1984年   5篇
  1983年   8篇
  1982年   5篇
  1969年   6篇
  1968年   5篇
  1960年   3篇
  1958年   4篇
  1957年   6篇
  1956年   4篇
  1953年   3篇
  1951年   4篇
  1948年   5篇
  1947年   3篇
  1941年   2篇
  1940年   3篇
  1939年   4篇
  1935年   2篇
  1933年   3篇
  1931年   2篇
  1917年   4篇
  1912年   2篇
  1911年   2篇
  1910年   2篇
  1889年   2篇
排序方式: 共有528条查询结果,搜索用时 15 毫秒
461.
Four hundred and sixty-two pigs from 37 herds were examined at slaughter for the presence and extent of turbinate atrophy and pneumonia. Turbinate atrophy was scored by measuring the mm space between the turbinate bone and the floor of the nasal cavity on both sides of the nasal septum. The total percentage of pneumonic involvement for each lung was evaluated by scoring the percentage of each lobe that was consolidated.

There was a low, positive correlation between individual scores of turbinate atrophy and the associated percentage of lung involved with pneumonia (r = + 0.177; p < 0.001). There was a postive correlation between the herd mean turbinate atrophy score and the herd mean percentage pneumonia score (r = + 0.515; p = 0.001).

The age at slaughter was known for 95 pigs from four herds and was not significantly correlated with the mm of turbinate atrophy, or the percentage of pneumonia.

  相似文献   
462.
463.
Hood ME  Shew HD 《Phytopathology》1997,87(12):1214-1219
ABSTRACT The ability of Thielaviopsis basicola to survive saprophytically in soil was investigated using root tissue from susceptible hosts as organic substrates. Inoculum densities were lower in soils amended with root tissue than in nonamended controls after 2 and 4 weeks of incubation. The greatest decrease occurred in soils containing the highest concentration of root tissue or in soils in which root tissue included the soluble components of the living root. Reproduction by T. basicola also was examined in axenic media containing either killed root pieces or various carbohydrates as the sole carbohydrate source. T. basicola utilized killed root tissue as a carbohydrate source in axenic media, particularly in cultures in which root tissue included the soluble components. Enzymatic activities of T. basicola, however, did not result in maceration of the root tissue. T. basicola utilized sucrose and cellobiose, but did not utilize structural carbohydrates such as cellulose, hemicellulose, or pectin. Based on the absence of significant saprophytic ability, T. basicola should be classified ecologically as an obligate parasite.  相似文献   
464.
The effect of metrizamide myelography on 90-minute postmyelographic cerebrospinal fluid (CSF) samples was evaluated in a paired crossover study in 16 normal dogs. Each dog received a routine cervical myelogram (nonwithdrawal myelography) and a myelogram followed by contrast medium removal via aspiration from the subarachnoid space (withdrawal myelogram). Following nonwithdrawal myelography, the CSF was characterized by mild inflammation with a mixed pleocytosis and increased protein concentration. Compared with the nonwithdrawal CSF samples, the postmyelographic CSF of the withdrawal dogs had a more severe inflammatory response with significant increases (p < 0.05) in absolute numbers of neutrophils, monocytoid cells, eosinophils, lymphocytes, and protein concentration. The withdrawal procedure may have contributed an additional mechanical effect on the leptomeninges producing the more severe inflammatory response in the withdrawal dogs. Although seizure data are not reported here, postmyelographic seizures were more frequent following non-withdrawal myelography as compared with withdrawal myelography (p < 0.05), suggesting a decrease in metrizamide-induced neurotoxicity for the withdrawal dogs.  相似文献   
465.
我们在试验猪场的实际工作体会、调查以及阅读文献,对猪场生产中的几个细节进行了思考并提出几点建议,希望与各位同仁探讨。1仔猪超前免疫为了防止仔猪以后发生猪瘟,在仔猪出生后,尚未吃奶之前,可按常规剂量接种猪瘟兔化弱毒疫苗,2h后再让仔猪自由吃奶,即仔猪超前免疫。超免技术在我国多地研究和应用已有一二十年的历史,对其效果的认识和评价不一,有的认为对仔猪起到了很好的保护效果,有的也发现应用超免技术后仔猪免疫保护力下降甚至免疫失败,且分歧有不断增大的趋势。根据实际应用的体会,我们认为超免技术有充分的理论根据,值得肯定和应用…  相似文献   
466.
OBJECTIVE: To evaluate an occlusion technique for the internal carotid artery of horses using an intravascular, detachable, self-sealing, latex balloon distally and ligatures proximally. STUDY DESIGN: Experimental study. ANIMALS: Six healthy adult horses. METHODS: In each horse, the left internal carotid artery was occluded by placement of an intravascular, detachable, self-sealing, latex balloon distally and two ligatures proximally. Radiographs were taken on days 2, 5, 10, and 30 after surgery to evaluate balloon inflation and position. Endoscopic examination of the left guttural pouch was performed 10 days after surgery to evaluate the integrity of the internal carotid artery and surrounding tissues. At 30 days, the left and right, common, internal, and external carotid arteries were examined grossly and then processed for histologic evaluation. RESULTS: Immediate and long-term occlusion of the left internal carotid artery was achieved in all horses. The surgical procedure was technically straightforward and no intraoperative or postoperative complications were encountered. The balloons remained inflated and in their original position throughout the study. Maturing to mature, organized thrombi were present in the left internal carotid artery in all horses at 30 days. The cerebral arterial circle and common carotid artery were patent at their junctions with the internal carotid artery in all horses. CONCLUSIONS: Use of an intravascular, detachable, self-sealing, latex balloon distally and ligatures proximally is an effective technique for occluding the internal carotid artery of horses. CLINICAL RELEVANCE: This technique may be useful for prevention of fatal hemorrhage in horses with lesions of the internal carotid artery.  相似文献   
467.
OBJECTIVE: To determine long-term prognosis for horses with laminitis treated by deep digital flexor (DDF) tenotomy and to identify factors affecting success of the surgical procedure. DESIGN: Retrospective study. ANIMALS: 35 horses with laminitis treated by DDF tenotomy between 1988 and 1997. PROCEDURE: Information was obtained from individual medical records and follow-up telephone interviews with owners and referring veterinarians. Cumulative proportions of horses that survived 6 months and 2 years after tenotomy were determined. Effect of Obel grade of lameness on 6-month and 2-year survival and effect of distal phalangeal rotation on survival and future performance were evaluated by chi 2 analysis. Body weights of horses that survived > or = 2 years were compared with those of horses that survived < 2 years by ANOVA. RESULTS: 27 of the 35 (77%) horses survived > or = 6 months, and 19 of 32 (59%) survived > 2 years. Obel grade of lameness and body weight at time of surgery had no effect on 6-month or 2-year survival. Degree of distal phalangeal rotation had no effect on 2-year survival or the ability of horses to be used for light riding. Twenty-two of the 30 (73%) owners interviewed indicated they would have the procedure repeated on their horses given similar circumstances. CLINICAL IMPLICATIONS: DDF tenotomy is a viable alternative for horses with laminitis refractory to conventional medical treatment. In some instances, the procedure may be effective in returning horses to light athletic use.  相似文献   
468.
469.
470.
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