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   49840篇
  免费   2756篇
  国内免费   33篇
林业   1706篇
农学   1671篇
基础科学   253篇
  5851篇
综合类   8959篇
农作物   1533篇
水产渔业   2730篇
畜牧兽医   26436篇
园艺   575篇
植物保护   2915篇
  2019年   423篇
  2018年   782篇
  2017年   831篇
  2016年   756篇
  2015年   613篇
  2014年   760篇
  2013年   1755篇
  2012年   1363篇
  2011年   1695篇
  2010年   1159篇
  2009年   1102篇
  2008年   1692篇
  2007年   1599篇
  2006年   1508篇
  2005年   1396篇
  2004年   1402篇
  2003年   1378篇
  2002年   1205篇
  2001年   1927篇
  2000年   1998篇
  1999年   1506篇
  1998年   570篇
  1997年   501篇
  1996年   438篇
  1995年   613篇
  1994年   522篇
  1993年   457篇
  1992年   1153篇
  1991年   1216篇
  1990年   1180篇
  1989年   1100篇
  1988年   1080篇
  1987年   1110篇
  1986年   1072篇
  1985年   968篇
  1984年   850篇
  1983年   740篇
  1982年   473篇
  1981年   426篇
  1979年   663篇
  1978年   547篇
  1977年   481篇
  1976年   445篇
  1975年   474篇
  1974年   546篇
  1973年   539篇
  1972年   561篇
  1971年   475篇
  1970年   454篇
  1969年   489篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Gentamicin-impregnated polymethylmethacrylate beads were used to treat infective arthritis in the small tarsal joints of 11 severely lame horses. Under general anaesthesia, between five and 10 beads were placed into a 7 to 8 mm tract drilled across the affected joint and, in all except one horse, they were left in place for 14 days. Two of the horses were euthanased for reasons other than persistent tarsal joint sepsis, but the other nine survived and seven of them returned to their previous level of athletic performance.  相似文献   
993.
994.
995.
Emboli of central nervous tissue were detected in the jugular venous blood of two of 15 sheep stunned with a conventional cartridge-operated captive bolt gun and in two of 15 sheep stunned with a pneumatically activated gun. No emboli were detected in arterial blood from these sheep or in venous blood from sheep stunned electrically. Emboli from an animal with BSE could transmit the disease to people.  相似文献   
996.
997.
998.
The densitometric and mechanical structural properties of the left and right fifth metacarpal bones of 10 racing greyhounds with a fracture of the central tarsal bone and 10 without a fracture were investigated by dual energy x-ray absorptiometry and a servo-hydraulic materials testing machine. In all the greyhounds the bone mineral density of the left fifth metacarpal bone was significantly greater than that of the right (P<0.001), but there was no significant difference between the degree of asymmetry in bone mineral density in the two groups. The ultimate torque and energy-to-failure of the left fifth metacarpal bone of the greyhounds with a fracture of the right central tarsal bone were significantly higher than in the right fifth metacarpal bone and higher than in both the left and right fifth metacarpal bones of the greyhounds with no fracture (P<0.05). The ultimate torque and energy-to-failure were significantly related to bone mineral density (P<0.005), and 22 per cent of the variation in these structural properties could be explained by variations in bone mineral density. Fifth metacarpal remodelling in response to asymmetric cyclic loading is bone-specific, and structural properties are enhanced in the left fifth metacarpal of greyhounds with a fracture of the right central tarsal bone.  相似文献   
999.
Twenty-four specific pathogen-free cats were inoculated with 3 x 10(3) infectious units of a field isolate of Chlamydia psittaci on to the corneal surface. Seven days later they were assigned randomly to three groups of eight and treated orally for 19 days with either clavulanic acid-potentiated amoxycillin, doxycycline or a placebo. Both treated groups responded rapidly, with a marked reduction in isolation rates and clinical scores which were significantly lower than in the placebo group within two and four days, respectively. After two days the group treated with potentiated amoxycillin had a significantly lower isolation score than the group treated with doxycycline. Forty days after they were infected the clinical signs recurred in five of the eight cats treated with potentiated amoxycillin, but a four-week course of potentiated amoxycillin resulted in a complete clinical recovery with no evidence of a recurrence for six months.  相似文献   
1000.
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