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   105467篇
  免费   6341篇
  国内免费   634篇
林业   4179篇
农学   3225篇
基础科学   835篇
  13605篇
综合类   19279篇
农作物   3976篇
水产渔业   5155篇
畜牧兽医   54275篇
园艺   1426篇
植物保护   6487篇
  2021年   928篇
  2020年   1021篇
  2019年   1233篇
  2018年   1798篇
  2017年   2116篇
  2016年   1874篇
  2015年   1685篇
  2014年   1976篇
  2013年   3921篇
  2012年   3727篇
  2011年   4441篇
  2010年   2949篇
  2009年   2817篇
  2008年   4047篇
  2007年   3853篇
  2006年   3436篇
  2005年   3282篇
  2004年   2925篇
  2003年   3014篇
  2002年   2769篇
  2001年   3177篇
  2000年   3217篇
  1999年   2487篇
  1998年   1039篇
  1997年   965篇
  1995年   975篇
  1992年   1901篇
  1991年   2164篇
  1990年   2012篇
  1989年   1940篇
  1988年   1805篇
  1987年   1876篇
  1986年   1879篇
  1985年   1729篇
  1984年   1480篇
  1983年   1253篇
  1982年   890篇
  1979年   1387篇
  1978年   1096篇
  1977年   931篇
  1976年   968篇
  1975年   1019篇
  1974年   1284篇
  1973年   1240篇
  1972年   1199篇
  1971年   1094篇
  1970年   1039篇
  1969年   1050篇
  1967年   999篇
  1966年   936篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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   
42.
Hege  Kippenes  DVM  Patrick R.  Gavin  DVM  PhD  Susan L.  Kraft  DVM  PhD  Ronald D.  Sande  DVM  MS  PhD  Russell L.  Tucker  DVM 《Veterinary radiology & ultrasound》2001,42(2):130-133
The pituitary gland was measured from transverse magnetic resonance T1-weighted images after Gadolinium administration in 96 dogs weighing from 13 to 45 kg. The measurements were done by hand with calipers. The mean (+/- standard deviation) pituitary gland height was 5.1 mm (+/-0.9 mm). The mean width was 6.4 mm (+/- 1.1 mm). The correlation coefficient between pituitary and brain measurements, between pituitary measurement and body weight, and brain measurements and body weight was 0.0 to 0.3. A hyperintense region was present on T1-weighted images in the center of the pituitary gland in 64% of the dogs. At necropsy the pituitary glands were grossly and histologically normal. No pituitary gland measurements were performed at necropsy.  相似文献   
43.
Star catalogues     
  相似文献   
44.
45.
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   
46.
47.
In addition to the well-defined phenolic estrogens in human pregnancy urine there appears to be another estrogenic substance which is a neutral non-ketonic compound.  相似文献   
48.
49.
50.
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