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   283871篇
  免费   16475篇
  国内免费   657篇
林业   24175篇
农学   14198篇
基础科学   3009篇
  45299篇
综合类   30249篇
农作物   17260篇
水产渔业   17748篇
畜牧兽医   117869篇
园艺   6383篇
植物保护   24813篇
  2020年   2938篇
  2019年   3710篇
  2018年   4366篇
  2017年   4757篇
  2016年   5070篇
  2015年   4501篇
  2014年   5861篇
  2013年   16433篇
  2012年   7349篇
  2011年   9575篇
  2010年   7899篇
  2009年   8360篇
  2008年   8939篇
  2007年   8016篇
  2006年   8395篇
  2005年   7556篇
  2004年   7374篇
  2003年   7157篇
  2002年   6455篇
  2001年   7657篇
  2000年   7364篇
  1999年   6549篇
  1998年   4304篇
  1997年   4355篇
  1996年   4072篇
  1995年   4649篇
  1994年   4096篇
  1993年   3770篇
  1992年   5226篇
  1991年   5326篇
  1990年   5156篇
  1989年   4979篇
  1988年   4431篇
  1987年   4408篇
  1986年   4395篇
  1985年   4620篇
  1984年   4123篇
  1983年   3821篇
  1982年   3063篇
  1981年   2947篇
  1980年   2911篇
  1979年   3615篇
  1978年   3213篇
  1977年   2920篇
  1976年   2777篇
  1975年   2718篇
  1974年   2891篇
  1973年   2893篇
  1972年   2582篇
  1971年   2575篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
152.
Two serological tests (indirect immunofluorescence and enzyme-linked immunosorbent assay) were developed for the detection of fetal antibody to Chlamydia psittaci. Fetal blood and thoracic fluid from 126 field cases of suspected ovine chlamydial abortion were examined using both tests. Placenta and fetal tissues (lung, liver, and kidney) from the same animals were also examined by the following conventional diagnostic methods: isolation in McCoy cells, detection of chlamydial lipopolysaccharide (LPS), modified Ziehl-Nielsen staining, and direct fluorescent antibody staining of chlamydia in frozen cryostat sections. Seventy cases were positive by fetal serology, and of these, 68 were also positive by isolation and/or LPS detection. The remaining 56 cases had negative fetal serology, and of these, 39 were positive by isolation and/or LPS detection. Results indicate that fetal serology, although less sensitive than either isolation in McCoy cells or detection of chlamydial LPS antigen, may be of particular use when placenta is not available.  相似文献   
153.
Subgroup-specific peptide-based enzyme-linked immunosorbent assays from the G-protein of the ovine and bovine respiratory syncytial virus (RSV), respectively, were used to determine the prevalence of the ovine and bovine subgroup strains of RSV infections in cattle. A total of 1,102 bovine serum samples were obtained from 6 diagnostic laboratories located in the northwestern and the southeastern USA and were tested for antibody to either the bovine or ovine subgroups of RSV. Antibody to viruses from each subgroup was present in samples from each region and all states tested. The Southeast had a higher prevalence of the bovine subgroup strains (69.5%). Then did the Northwest (40.9%). The prevalence of the ovine strain was similar for the two regions (16.7% in the southeast, 14.9% in the northwest). The overall prevalence was 56.6% for the bovine strain and 15.9% for the ovine strain. These results suggest members of the ovine subgroup of RSV circulate in the cattle population but with less frequency than those viruses of the bovine subgroup.  相似文献   
154.
155.
    
Ohne Zusammenfassung  相似文献   
156.
157.
Ohne Zusammenfassung  相似文献   
158.
Ohne Zusammenfassung  相似文献   
159.
160.
The medical records of 38 horses with puncture wounds of the navicular bursa were reviewed. Only 12 horses had a satisfactory outcome (breeding or riding). Of the remaining 26 horses, 19 were euthanized, five were sold due to persistent severe lameness, one died, and one was lost to long-term follow-up. Different combinations of conservative management prior to surgical debridement and drainage of the navicular bursa were unsuccessful in resolving the condition. Horses that were treated surgically within 1 week of the injury and had a hind leg affected had the best chance of a satisfactory outcome. Additional wound debridement was necessary in 15 horses after initial surgical treatment. The most common complications encountered were navicular bone osteomyelitis and sepsis of the deep digital flexor tendon. Thirteen of 14 horses that had rupture of the deep digital flexor tendon and subluxation of the distal interphalangeal joint had an unsatisfactory outcome. One mare subsequently developed ankylosis of the distal interphalangeal joint and was a useful brood mare. Two horses that had biaxial palmar digital neurectomy because of persistent lameness were later euthanized because of navicular bone fracture and rupture of the deep digital flexor tendon. Results from limited numbers of bacterial cultures and antibiotic sensitivities suggest that penicillin and an aminoglycoside antibiotic should be used as initial antibiotic therapy. Immediate surgical debridement and appropriate antibiotic treatment are recommended as the minimum therapy for penetrating wounds of the navicular bursa in horses.  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