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   30454篇
  免费   1301篇
  国内免费   9篇
林业   1070篇
农学   892篇
基础科学   174篇
  4583篇
综合类   3993篇
农作物   1152篇
水产渔业   1150篇
畜牧兽医   16636篇
园艺   335篇
植物保护   1779篇
  2021年   224篇
  2020年   267篇
  2019年   337篇
  2018年   603篇
  2017年   667篇
  2016年   569篇
  2015年   365篇
  2014年   554篇
  2013年   1668篇
  2012年   869篇
  2011年   1118篇
  2010年   816篇
  2009年   768篇
  2008年   1087篇
  2007年   1058篇
  2006年   894篇
  2005年   722篇
  2004年   730篇
  2003年   668篇
  2002年   588篇
  2001年   746篇
  2000年   750篇
  1999年   549篇
  1998年   244篇
  1997年   227篇
  1995年   269篇
  1992年   405篇
  1991年   417篇
  1990年   435篇
  1989年   447篇
  1988年   349篇
  1987年   355篇
  1986年   385篇
  1985年   344篇
  1984年   334篇
  1983年   303篇
  1979年   482篇
  1978年   330篇
  1977年   374篇
  1976年   470篇
  1975年   491篇
  1974年   531篇
  1973年   485篇
  1972年   442篇
  1971年   359篇
  1970年   373篇
  1969年   436篇
  1968年   445篇
  1967年   446篇
  1966年   446篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
12.
13.
14.
15.
16.
17.
18.
19.
The mean area and minimal diameter of 3 histochemically determined myofiber types (1, 2A, and 2B; myosin ATPase in acid buffer) were calculated in middle gluteal muscle biopsy specimens from 62 stallions, 47 Andalusians and 15 Arabians, ranging in age from 6 to 12 years. Fourteen Andalusians and 7 Arabians were untrained, and the remainder were actively endurance-trained. The 6-month training schedules involved walking, slow trotting, and cantering. Fourteen Andalusians were moderately endurance-trained, whereas the other 19 Andalusians and 8 Arabians were strongly endurance-trained. Significant differences were not recorded between untrained and endurance-trained Arabians with respect to the area (type 1, 3,194 +/- 869 microns 2 and 3,150 +/- 370 microns 2; type 2A, 3,819 +/- 890 microns 2 and 3,380 +/- 356 microns 2; and type 2B, 4,872 +/- 962 microns 2 and 4,417 +/- 646 microns 2) or minimal diameter (type 1, 52.2 +/- 7.4 microns and 52.8 +/- 3.1 microns; type 2A, 58.1 +/- 6.7 microns and 55.0 +/- 2.8 microns; and type 2B, 65.3 +/- 6.4 microns and 63.4 +/- 4.3 microns) of the 3 fiber types, nor between untrained and endurance-trained Andalusians with respect to the area (untrained, 3,990 +/- 690 microns 2; moderately endurance-trained, 3,882 +/- 347 microns 2; and strongly endurance-trained, 3,758 +/- 510 microns 2) and minimal diameter (untrained, 58.1 +/- 4.7 microns; moderately endurance-trained, 59.7 +/- 2.7 microns; and strongly endurance-trained, 58.7 +/- 4.5 microns) of 2A fibers.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
20.
The feasibility of producing salmonella-free turkeys was investigated over a 5-year period. In Phase 1, a hatchery-breeder flock operation was monitored extensively for 4 years. Hatching eggs from a primary breeder over this period (1978-81) resulted in salmonella-free day-old poults from which 7500 hens and 600 tons were selected for breeders each of the 4 years. Approximately 2.5 million poults were produced over the 4 years. Salmonella arizonae was isolated from the hatchery debris over a 2-week period in 1980. The pelleted feed contained no animal protein products except fish solubles. A sample of feed from each delivery was cultured with no salmonella isolations. Environmental samples of dust and litter remained negative for salmonella. Phase 2 involved monitoring seven grow-out flocks initiated with salmonella-free poults with extra precautions directed at the feed and environment. The intestinal tracts of five of seven flocks at the time of marketing were negative for salmonella. Phase 3 involved a primary breeder-hatchery that had a 10-year history of S. sandiego infection in its breeder flocks and poults. A vaccination program using an autogenous oil-adjuvant bacterin supplementing other sanitation and management efforts resulted in elimination of S. sandiego. Because the breeder went out of business, it was not possible to determine if the freedom from salmonella could be sustained over a period of years.  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