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   97191篇
  免费   5832篇
  国内免费   42篇
林业   4042篇
农学   3116篇
基础科学   569篇
  12246篇
综合类   16759篇
农作物   4124篇
水产渔业   5030篇
畜牧兽医   49337篇
园艺   1350篇
植物保护   6492篇
  2021年   773篇
  2020年   854篇
  2019年   981篇
  2018年   1660篇
  2017年   1812篇
  2016年   1703篇
  2015年   1488篇
  2014年   1746篇
  2013年   4050篇
  2012年   3336篇
  2011年   3769篇
  2010年   2387篇
  2009年   2257篇
  2008年   3543篇
  2007年   3406篇
  2006年   3121篇
  2005年   3011篇
  2004年   2836篇
  2003年   2818篇
  2002年   2599篇
  2001年   3110篇
  2000年   2945篇
  1999年   2411篇
  1998年   1028篇
  1997年   935篇
  1996年   827篇
  1995年   1006篇
  1994年   894篇
  1993年   885篇
  1992年   1873篇
  1991年   1858篇
  1990年   1797篇
  1989年   1857篇
  1988年   1605篇
  1987年   1720篇
  1986年   1780篇
  1985年   1710篇
  1984年   1343篇
  1983年   1193篇
  1982年   857篇
  1979年   1136篇
  1978年   917篇
  1977年   792篇
  1975年   824篇
  1974年   1020篇
  1973年   1061篇
  1972年   1017篇
  1971年   969篇
  1970年   914篇
  1969年   834篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
Melanoma is a common neoplasm in horses, with a high rate of incidence in the perineum and ventral tail. Surgical excision is often recommended to remove such masses and can be achieved in the standing horse either via local infiltration of local anaesthetic, or via epidural administration of a local anaesthetic and/or an adrenergic α2 receptor agonist. The clinical records of all horses with tail and/or perineal melanomas that received epidural anaesthesia at a single equine hospital, over a 7-year period, were reviewed to determine the drugs administered and complications associated with the epidural injection. Twenty-five cases were identified, five of which received epidural anaesthesia on two occasions. Epidural anaesthesia was insufficient to allow surgical melanoma excision in two horses; repeated epidural injection allowed sufficient loss of sensation in one of these horses and additional regional infiltration of local anaesthetic allowed completion of surgery in the other. Three horses developed significant ataxia associated with epidural anaesthesia, two of which became recumbent. Both recumbent horses were placed under general anaesthesia, and in one of these, rope-assisted anaesthetic recovery resulted in additional complications associated with facial nerve paresis, fractured ribs and a fracture of the first coccygeal vertebra, with associated neurological dysfunction of the rectum, anus, tail and surrounding skin.  相似文献   
993.
994.
995.
Jervis  M.  Huaman  O.  Cahuascanco  B.  Bahamonde  J.  Cortez  J.  Arias  J. I.  Torres  C. G.  Peralta  O. A. 《Veterinary research communications》2019,43(3):165-178
Veterinary Research Communications - Mesenchymal stem cells (MSCs) are found in virtually all tissues, where they self-renew and differentiate into multiple cell types. Cumulative data indicate...  相似文献   
996.
Subsequent to a possum (Trichosurus vulpecula) poisoning operation purportedly using 1% phosphorus baits, six dogs with access to poisoned possums died of phosphorus poisoning. Two dogs survived, following treatment with oral copper sulphate and parenteral vitamin K. Clinical signs included depression, jaundice, vomiting and bloody diarrhoea. Post-mortem lesions included large areas of subcutaneous, interstitial and intermuscular haemorrhage, subserosal haemorrhage and liver degeneration. Free phosphorus was detected in the ingesta of three of the dogs which died up to 7 days after the last of the poison was laid. Analysis of two batches of baits used showed P levels of 1.17% and 1.24%.  相似文献   
997.
Antipyrine disposition in the dehydrated camel   总被引:1,自引:0,他引:1  
In the present study the effects of water deprivation in the camel ( Camelus dromedarius ) on the pharmacokinetic profile of antipyrine were assessed. A crossover design was used. The pharmacokinetics of antipyrine in adult and young camels were compared. Antipyrine was administered intravenously to young and adult female camels when water was available ad libitum and to the adult camels after 14 days of dehydration. The elimination half-life of antipyrine in watered adult camels was 136.5 ± 16.7 min. The half-life of elimination and the mean residence time of antipyrine were significantly prolonged following dehydration. The observed effects of water deprivation were not a function of age, as the pharmacokinetic profile of antipyrine in young camels was similar to that of the adults, but more likely due to the changes in oxidative metabolic capacity of the liver as a result of a reduced general metabolism. The results of the present study also show that the intrinsic clearance of antipyrine is proportional to the camel's body weight, as previously shown for other mammalian species.  相似文献   
998.
Furosemide is a problematic drug in a prolonged-release product because its absorption is site specific, taking place mainly in the upper parts of the alimentary tract. The aim of the study reported here was to develop prolonged-release furosemide formulations for dogs. The type of preparation selected was a hydroxypropyl methylcellulose (HPMC) matrix tablet. Evaluation was based on dissolution studies, on in vivo disintegration studies in the canine stomach and on bioavailability studies in Beagle dogs. The variables tested were the viscosity grade of the polymer, the amount of polymer and presence or absence of an alkaline compound (potassium carbonate) in the formulation. When potassium carbonate was included, furosemide was absorbed so slowly that drug administration once daily would give plateau drug plasma concentrations, even though the elimination half-life of furosemide is only about one hour.  相似文献   
999.
Surgical management of a large colorectal diverticulum in a dog A 10-year-old crossbred dog had a lour month history of intermittent rectal prolapse. Castration and use of stool softeners had been attempted to control tenesmus and obstipation. Examination per rectum was normal. Three months later colopexy was performed and the dog began defecating normally immediately after surgery. After one month, obstipation and tenesmus returned. Initially, faeces were misshapen and ribbon-like, then defecation stopped. Palpation per rectum revealed a band-like ventral mucosal fold approximately 6 cm Irom the anus. A contrast study demonstrated a large (4X2 cm), well-defined diverticulum in the colorectum. Diverticulectomy was performed using a surgical stapling device, which allowed rapid excision and substantially reduced risk of faecal contamination. Recovery was good and the dog remained clinically normal, although a slight narrowing of the colorectum was seen radiographically.  相似文献   
1000.
The objective of this study was to describe the arterial distribution of the hindfoot of the llama (Lama glama). Ten adult llamas, preserved in 6% formalin solution at 0 degree C, were dissected. The arterial system was perfused with a solution of 14% coloured plaster; the venous system was perfused with a solution of 17% coloured industrial gelatin. Angiographies were also obtained. In the llama, the arterial distribution is of the saphenous type and this simple sort of irrigation could be used as a didactic model. The caudal branch of the saphenous artery divides into the small lateral plantar artery and the larger medial plantar artery, which continues as the plantar common digital artery III, and it is the main blood supply of the hindfoot. The dorsal pedal artery is underdeveloped and the perforating tarsal artery does not exist in this species. The plantar common digital artery III divides into the plantar proper digital II, III and IV. Branches from the plantar proper digital artery III supply the digits. We compared the arterial distribution of the hindfoot of the llama with that of other domestic animals including the one-humped camel (Camelus dromedarius).  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