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   87294篇
  免费   5188篇
  国内免费   42篇
林业   2978篇
农学   2711篇
基础科学   526篇
  9921篇
综合类   16188篇
农作物   3655篇
水产渔业   4303篇
畜牧兽医   45546篇
园艺   1082篇
植物保护   5614篇
  2019年   807篇
  2018年   1193篇
  2017年   1376篇
  2016年   1291篇
  2015年   1145篇
  2014年   1361篇
  2013年   3453篇
  2012年   2557篇
  2011年   3040篇
  2010年   1979篇
  2009年   1947篇
  2008年   2935篇
  2007年   2837篇
  2006年   2688篇
  2005年   2535篇
  2004年   2384篇
  2003年   2412篇
  2002年   2275篇
  2001年   2904篇
  2000年   2782篇
  1999年   2268篇
  1998年   975篇
  1997年   893篇
  1996年   790篇
  1995年   957篇
  1994年   863篇
  1993年   857篇
  1992年   1812篇
  1991年   1811篇
  1990年   1751篇
  1989年   1816篇
  1988年   1570篇
  1987年   1680篇
  1986年   1739篇
  1985年   1665篇
  1984年   1312篇
  1983年   1167篇
  1982年   842篇
  1981年   723篇
  1979年   1107篇
  1978年   900篇
  1977年   781篇
  1976年   734篇
  1975年   810篇
  1974年   999篇
  1973年   1041篇
  1972年   994篇
  1971年   946篇
  1970年   887篇
  1969年   811篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Prolonged surgical anaesthesia in the dog was induced with propofol (6.5 ± 1.3 mg/kg) followed by alfentanil (25.5 ± 5 μg/kg) (mean ± 1 sd) and maintained with a continuous infusion of propofol (0.14 to 0.18 mg/kg/min) and alfentanil (2 to 3 μg/kg/min). Neuromuscular blockade was produced with vecuronium (0.1 mg/kg). After induction of anaesthesia with propofol, administration of alfentanil to dogs which had received no pre-anaesthetic medication produced cardiac arrest and apnoea. Administration of atropine intravenously immediately prior to alfentanil prevented these cardiac depressant effects. The cardiac depressant effect of alfentanil was not as severe in a second group of dogs in which anaesthesia was induced with thiopentone. After commencing the continuous infusion anaesthetic regime and establishment of IPPV, blood pressure and heart rate remained stable during the remaining 4 to 6 h period of anaesthesia. Recovery from anaesthesia was smooth and uneventful. The depressant effects of alfentanil on respiration and on consciousness were reversed rapidly by administration of nalbuphine (10 mg total dose). The smooth recovery and the integration of anaesthesia and post operative analgesia attained by the reversal of alfentanil with nalbuphine make this an attractive anaesthetic regime for major surgery in dogs, provided that facilities for IPPV are available.  相似文献   
992.
Liver glycogen levels of broilers infected with Eimeria acervulina, E. brunetti, or E. tenella fell during the acute phase of the infection with the maximum effect at 5–6 days post-inoculation (DPI). During the early recovery phase (6–8 DPI), liver glycogen levels in the E. acervulina-infected birds increased to levels up to 3 times greater than those found in uninoculated control birds. A lesser increase was occasionally seen in E. tenella-infected birds. Pair feeding studies showed that the decrease in liver glycogen was not related to the amount of feed consumed. The magnitude of the glycogen overshoot at 7 DPI was not related to the depression of weight gain at 5 and 6 DPI. When feed was withheld from birds, liver glycogen levels of uninoculated control birds fell rapidly within 1 h after feed withdrawal. In birds infected with E. acervulina, liver glycogen levels remained high even after 3 h starvation. Injection of glucagon indicated that glycogen could be mobilized in both infected and uninfected birds.  相似文献   
993.
The semisynthetic aminoglycoside amikacin is a potentially valuable antibiotic in broodmare practice due to its efficiency against Gram negative bacteria which have developed resistance to gentamicin. Each of 4 mares conceived when amikacin at 200 ug/ml in buffered extender was used in artificial insemination or as a prebreeding infusion. After intrauterine infusion of 2 g amikacin in 200 ml saline, 4 mares conceived to natural service or insemination with untreated semen after seven hours. In unbuffered saline solutions, amikacin (1 g/100 ml) and gentamicin (1 mg/ml) were spermicidal in vitro.  相似文献   
994.
A 4th of 667 cattle examined at a Wisconsin abattoir had teat papillomas. Excised teat papillomas were sorted by gross morphologic characteristics into 3 groups: (i) atypical filiform, (ii) atypical flat, and (iii) typical fibropapilloma. Bovine papilloma virus capsid antigen was detected in thin-section slides of the 3 groups of teat papillomas by peroxidase-antiperoxidase assay. The bovine papilloma virus involved with the atypical papillomas could not be characterized by molecular hybridization, because enough pure virus could not be harvested. Homogenates of the 3 groups of teat papillomas were inoculated on 2 ponies and 4 calves. Typical fibropapillomas were produced on the 4 calves, and fibromas, on the 2 ponies. Atypical papillomas were produced only in 2 heifers.  相似文献   
995.
The efficacy of oral vaccination for hemorrhagic enteritis of turkeys was assessed by comparing flocks raised on the same premises, under the same management, with and without vaccination. The immunizing virus, a strain of marble spleen disease virus of pheasants, was administered via the drinking water. Vaccinated and unvaccinated turkeys differed significantly in feed conversion rates and spleen weights after challenge.  相似文献   
996.
997.
998.
999.
1000.
Pharmacokinetics of amikacin in cats   总被引:1,自引:0,他引:1  
Six mixed-breed adult cats were given 5 mg of amikacin sulfate/kg of body weight by rapid IV, IM, and SC routes of administration. The serum concentration-vs-time data were analyzed, using a noncompartmental model. The harmonic mean +/- pseudo-SD of the effective half-life of amikacin was 78.8 +/- 19.3 minutes after IV administration, 118.7 +/- 14.4 minutes after IM administration, and 117.7 +/- 12.8 minutes after SC administration. The arithmetic mean +/- SD of mean residence time was 118.3 +/- 21.7 minutes, 173.4 +/- 19.9 minutes, and 171.7 +/- 19.1 minutes after IV, IM, and SC drug administration, respectively. The mean apparent volume of distribution at steady state was 0.17 +/- 0.02 L/kg, and the mean total body clearance was 1.46 +/- 0.26 ml/min/kg. Mean bioavailability was 95 +/- 20% after IM administration and 123 +/- 33% after SC drug administration. A recommended dosage of 10 mg/kg, q 8 h can be expected to provide a therapeutic serum concentration of amikacin with a mean steady-state concentration of 14 micrograms/ml. The SC route of administration is preferred, because of rapid absorption, good bioavailability, and ease of administration.  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