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   145723篇
  免费   8125篇
  国内免费   674篇
林业   6346篇
农学   4445篇
基础科学   1037篇
  16421篇
综合类   29471篇
农作物   5577篇
水产渔业   6625篇
畜牧兽医   73991篇
园艺   1878篇
植物保护   8731篇
  2019年   1326篇
  2018年   1991篇
  2017年   2247篇
  2016年   2005篇
  2015年   1914篇
  2014年   2188篇
  2013年   5083篇
  2012年   4142篇
  2011年   5030篇
  2010年   3373篇
  2009年   3197篇
  2008年   4686篇
  2007年   4578篇
  2006年   4178篇
  2005年   4006篇
  2004年   3693篇
  2003年   3809篇
  2002年   3550篇
  2001年   4231篇
  2000年   4344篇
  1999年   3459篇
  1998年   1374篇
  1997年   1293篇
  1995年   1419篇
  1993年   1271篇
  1992年   2768篇
  1991年   3006篇
  1990年   3025篇
  1989年   2963篇
  1988年   2737篇
  1987年   2786篇
  1986年   2834篇
  1985年   2678篇
  1984年   2263篇
  1983年   2017篇
  1982年   1345篇
  1979年   2121篇
  1978年   1679篇
  1977年   1403篇
  1976年   1404篇
  1975年   1536篇
  1974年   2058篇
  1973年   2040篇
  1972年   2021篇
  1971年   1917篇
  1970年   1818篇
  1969年   1686篇
  1968年   1390篇
  1967年   1503篇
  1966年   1394篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
71.
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   
72.
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   
73.
74.
Star catalogues     
  相似文献   
75.
76.
77.
78.
The feet of three two-humped camels (Camelus bactrianus), one lama (Lama glama) and four alpacas (Lama pacos) from zoos and a circus in the Netherlands were examined for the mange-mite Choroptes bovis. Mites were found on two of the camels, the lama, and three of the alpacas. On one camel and one alpaca small mange lesions on the feet were present. This is the first report of Chorioptes bovis and chorioptic mange in the two-humped camel.  相似文献   
79.
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   
80.
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