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   1122篇
  免费   66篇
  国内免费   3篇
林业   35篇
农学   17篇
基础科学   15篇
  146篇
综合类   169篇
农作物   20篇
水产渔业   33篇
畜牧兽医   682篇
园艺   7篇
植物保护   67篇
  2021年   10篇
  2019年   20篇
  2018年   17篇
  2017年   20篇
  2016年   18篇
  2015年   23篇
  2014年   18篇
  2013年   45篇
  2012年   32篇
  2011年   45篇
  2010年   34篇
  2009年   23篇
  2008年   34篇
  2007年   39篇
  2006年   42篇
  2005年   36篇
  2004年   29篇
  2003年   31篇
  2002年   21篇
  2001年   35篇
  2000年   24篇
  1999年   26篇
  1998年   16篇
  1997年   11篇
  1996年   16篇
  1995年   12篇
  1994年   11篇
  1992年   18篇
  1991年   32篇
  1990年   25篇
  1989年   14篇
  1988年   19篇
  1987年   22篇
  1986年   14篇
  1985年   28篇
  1984年   19篇
  1983年   17篇
  1982年   12篇
  1981年   13篇
  1979年   12篇
  1978年   13篇
  1977年   18篇
  1974年   10篇
  1973年   25篇
  1972年   19篇
  1971年   12篇
  1970年   9篇
  1969年   10篇
  1967年   11篇
  1966年   15篇
排序方式: 共有1191条查询结果,搜索用时 15 毫秒
101.
102.
The objective of this study was to examine the efficacy of a caudal epidural anaesthesia using lidocaine or xylazine in a high volume for analgesia of the flank, navel and hamstring tendon. Fourteen calves weighing 57.7 +/- 5.1 kg and 37.9 +/- 9.3 (mean +/- SEM) days old were randomly divided into two groups of seven calves each. Calves belonging to the lidocaine group were given a 2% lidocaine solution in the sacrococcygeal vertebral space epidurally at a volume of 0.4 ml/kg (8 mg/kg) body weight (BW). Animals of the xylazine group were administered an epidural anaesthesia with xylazine at a dose of 0.1 mg/kg BW, diluted with a 0.9% saline solution to a corresponding final volume of 0.4 ml/kg BW. Heart rate and respiratory rate were measured and the degree and duration of analgesia was determined by the response to a skin prick with a hypodermic needle over a period of 350 min after epidural injection. After epidural anaesthesia with lidocaine the mean heart rate increased during dorsal recumbency, whereas after xylazine both heart rate and respiratory rate decreased significantly (P < 0.05). The epidural injection of xylazine compared with lidocaine caused longer (P < 0.05) analgesia at the hamstring tendon (mean +/- SEM, 120.7 +/- 29.7 min versus 93.6 +/- 3.5 min) and at the flank (100.7 +/- 24.4 min versus 78.3 +/- 11.1 min). There were no differences in the intensity of analgesia between groups. After xylazine application analgesia at the navel was achieved for 95.0 +/- 14.1 min whereas after lidocaine injection sufficient analgesia at the navel was found in just two of seven calves for 55 and 95 min respectively. Based on above experiences, a second study was performed, in which a combination of xylazine and local anaesthetics was used and the injection volume was increased to prove the efficacy of caudal epidural anaesthesia in 15 calves (26.3 +/- 26.7 days; 57.1 +/- 19.5 kg) submitted to the clinic for regular umbilical surgery. In these cases the xylazine (0.1 mg/kg BW) was diluted with 2% lidocaine (n = 7) or 2% procaine (n = 8) to a corresponding final volume of 0.5-0.6 ml/kg BW. In all cases complete anaesthesia of the surgical area was achieved and no adverse effects were observed. Overall the high volume caudal epidural anaesthesia represents an effective, safe, cheap and easy to perform alternative for anaesthesia of the navel, flank and hamstring tendon in calves without major side effects.  相似文献   
103.
104.
The hypothesis that an altered expression of CD11/CD18 on bovine circulating monocytes, polymorphonuclear leukocytes (PMN), or both, contributes to an increased mastitis susceptibility in periparturient cows was tested. Expression of CD18 and CD11a, -b, -c on bovine monocytes and PMN were assessed in 8 Friesian-Holstein cows by flow cytometry from 2 wk before calving to 5 wk after calving. Minor changes in adhesion molecule expression levels were detected throughout the experimental period. Compared with PMN, monocytes exhibited an expression level that was similar for CD18, higher for CD11a and CD11c, but lower for CD11b. Differences in density may reflect the relative importance of these adhesion molecules on both leukocyte types. In this study, the decreased number of milk resident macrophages and PMN observed during the periparturient period could not be attributed to changes of CD11/CD18 levels on circulating leukocytes.  相似文献   
105.
106.
The reliability and reproducibility of random amplified polymorphic DNA analysis (RAPD) was compared with restriction fragment length polymorphism (RFLP) by analysing three virus strains isolated from zoo animals in Berlin and three isolates which were cultivated from pets from Northern Germany. The RAPD technique was evaluated as a reliable tool with good reproducibility of the patterns for each virus strain investigated. Problems of interpretation due to inconsistent intensity of bands in different polymerase chain reaction runs may arise for less experienced personnel. The RAPD analysis can be performed within one working day and needs less DNA compared with RFLP so costs will be reduced. The obvious advantage of RFLP is that the pattern can be traced to the recognition site of the restriction enzyme whereas the RAPD primer sequence is not present in the orthopoxvirus genome at all. To the authors knowledge, the RAPD technique has never been applied in DNA viruses before and they conclude that this technique is a useful tool for the discrimination of closely related cowpoxviruses.  相似文献   
107.
108.
Commercial otic preparations that contained dexamethasone or triamcinolone acetate were applied twice daily to both ears of 2 groups of dogs (n = 8). Marked adrenocortical suppression, reflected by low serum cortisol concentrations, was observed in all dogs. Results of ACTH response tests were blunted after 7 days of treatment. Twenty-one days after treatment, serum cortisol concentrations still were suppressed in all dogs, compared with pretreatment control concentrations. Fourteen days after cessation of otic treatment, 5 of 8 dogs still had inadequate release of cortisol in response to ACTH.  相似文献   
109.
110.
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