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   2465篇
  免费   141篇
  国内免费   2篇
林业   126篇
农学   32篇
基础科学   10篇
  236篇
综合类   658篇
农作物   108篇
水产渔业   243篇
畜牧兽医   1067篇
园艺   26篇
植物保护   102篇
  2021年   34篇
  2020年   39篇
  2019年   52篇
  2018年   43篇
  2017年   55篇
  2016年   36篇
  2015年   35篇
  2014年   44篇
  2013年   107篇
  2012年   91篇
  2011年   109篇
  2010年   52篇
  2009年   52篇
  2008年   119篇
  2007年   119篇
  2006年   85篇
  2005年   71篇
  2004年   88篇
  2003年   92篇
  2002年   73篇
  2001年   44篇
  2000年   45篇
  1999年   51篇
  1998年   21篇
  1995年   21篇
  1994年   20篇
  1992年   39篇
  1991年   42篇
  1990年   39篇
  1989年   26篇
  1988年   32篇
  1987年   31篇
  1986年   37篇
  1985年   24篇
  1984年   17篇
  1983年   25篇
  1979年   17篇
  1978年   19篇
  1975年   17篇
  1974年   23篇
  1973年   32篇
  1972年   17篇
  1970年   23篇
  1969年   18篇
  1968年   22篇
  1901年   20篇
  1898年   16篇
  1897年   24篇
  1896年   24篇
  1895年   28篇
排序方式: 共有2608条查询结果,搜索用时 15 毫秒
91.
The efficacy of an ethylenediamine dihydriodide containing salt mixture was evaluated with regard to the prevention of naturally occurring foot rot in pastured cattle. Ninety-six cattle were assigned to the treatment group and 96 were assigned to the control group. The groups were allowed consumption of salt-mineral mixtures, ad libitum, that were identical, except with respect to iodine concentration. The control group's mixture contained 0.0025% iodine and the treatment group's mixture contained 0.125% iodine (0.156% ethylenediamine dihydriodide). The incidence of foot rot was measured, as was the severity of the lesions and accompanying lameness. The incidence of foot rot in the control group (20.8%) was significantly (P less than 0.05) greater than the incidence in the treatment group (8.3%). The severity of foot rot was greater (P = 0.024) in the control calves vs the treatment calves. Total serum iodine concentrations were measured in the 2 groups on days 0, 46, and 130 of the experiment. The serum iodine values of the treatment group on day 46 (46 +/- 19.8 g/dl) and day 130 (23 +/- 12.3 g/dl) were significantly different (P less than 0.01) than the serum iodine concentrations of the control animals and the pretreatment values (day 0) of both groups. Production was measured via calf weaning weights. There were no detectable differences between the 205-day adjusted weaning weights of the calves in the control group vs the calves in the treatment group. Clinical signs of iodism were not observed in the cattle involved in this study.  相似文献   
92.
93.
94.
Diurnal variations in the hydroxyl radical concentration of ambient air were measured for the first time by the technique of laser-induced fluorescence.  相似文献   
95.
96.
97.
98.
99.
Electrocardiograms were reocrded from 153 racehorses and 10 Olympic three-day-event horses. The horses were then grouped into those presented for routine examination, those in which there was a complaint of poor performance, those going to the Montreal Olympics, and those with upper respiratory tract abnormalities. When the ECGs of the four groups were compared on the basis of detection of abnormality, it was found that 93.2% of the poor performance group showed abnormalities of various types. The routine examination group showed 21.1% of horses with abnormal ECGs, and over half of these have been followed to the point where it can be said they raced unsuccessfully. In particular, this applied to those horses with T wave abnormalities in 4 or more leads, and to those with intraatrial block. There were significant T wave changes in 50% of the Olympic horses, and 43.7% of horses with laryngeal hemiplegia showed abnormality. While it can be concluded that T wave changes are highly significant findings in an ECG, it is also true that modification of the training programme is a way of helping trainers to get the best out of horses which might otherwise have a serious limitation of their performance potential.  相似文献   
100.
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