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   194297篇
  免费   10687篇
  国内免费   115篇
林业   9040篇
农学   6429篇
基础科学   1157篇
  24333篇
综合类   31023篇
农作物   7345篇
水产渔业   9947篇
畜牧兽医   100457篇
园艺   2559篇
植物保护   12809篇
  2019年   1771篇
  2018年   2998篇
  2017年   3271篇
  2016年   3085篇
  2015年   2642篇
  2014年   3263篇
  2013年   7813篇
  2012年   5760篇
  2011年   6761篇
  2010年   4525篇
  2009年   4500篇
  2008年   6642篇
  2007年   6481篇
  2006年   6006篇
  2005年   5586篇
  2004年   5392篇
  2003年   5452篇
  2002年   5028篇
  2001年   6119篇
  2000年   6042篇
  1999年   4958篇
  1998年   1932篇
  1997年   1920篇
  1996年   1774篇
  1995年   2164篇
  1994年   1777篇
  1993年   1818篇
  1992年   3789篇
  1991年   3982篇
  1990年   4019篇
  1989年   4020篇
  1988年   3727篇
  1987年   3691篇
  1986年   3651篇
  1985年   3545篇
  1984年   2887篇
  1983年   2584篇
  1982年   1765篇
  1979年   2655篇
  1978年   2110篇
  1977年   1843篇
  1976年   1767篇
  1975年   1930篇
  1974年   2353篇
  1973年   2453篇
  1972年   2431篇
  1971年   2209篇
  1970年   2152篇
  1969年   1976篇
  1967年   1761篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
1. To test the preferences of hens for particular social conditions when laying, they were provided with choices of nest‐sites varying in seclusion. Three experimental conditions were used.

2. In Experiment 1, nest‐site selection by members of a group of light hybrids was studied in a complex pen‐system. Eggs were clumped in distribution ; only one individual laid in the most secluded part of the system.

3. Experiment 2 provided light hybrids with an extensive outdoor area, but similarly clumped laying was observed; there was no indication that hens attempted to find concealment for nesting.

4. In Experiment 3, hens from a group of light hybrids just coming into lay and from a group of mature medium hybrids were tested singly, in an area that included a cage containing some of their flockmates. Most subjects from both groups laid near the other birds rather than in isolation.

5. In semi‐intensive conditions, the majority of hens are apparently gregarious rather than solitary in their nesting behaviour.  相似文献   

992.
993.
994.
A two year old Thoroughbred gelding, presented with guttural pouch hemorrhage, had the internal and external carotid arteries ligated. Guttural pouch mycosis was detected on endoscopic examination. After one month of topical antifungal therapy, the horse was returned and euthanized because of recurrent epistaxis. A bacterial infection of the guttural pouch with associated ulceration and hemorrhage from the maxillary artery was found at necropsy.

A two year old grade gelding had ulceration and hemorrhage from the external carotid artery. Utilizing balloon-tipped catheters and arterial ligation, hemestasis was achieved in the internal carotid artery and the external carotid artery and its branches. Mycotic ulceration of the internal carotid artery was detected endoscopically and treated with local antifungal therapy for one month. Thirty-three days postoperatively the horse returned, bleeding from a lesion in the maxillary artery. The rationale for surgical intervention to prevent epistaxis associated with guttural pouch mycosis and possible etiologies for postsurgical epistaxis are discussed.

  相似文献   
995.
A nine year old Hereford crossbred cow with a history of progressive neurological signs was referred to the Western College of Veterinary Medicine, Saskatoon. A large intracranial mass, histologically identified as a schwannoma, was found to be compressing the left brain stem and appeared to have arisen from the left fifth cranial nerve.  相似文献   
996.
997.
William osler and comparative medicine   总被引:2,自引:2,他引:0       下载免费PDF全文
During the last thirty years of the nineteenth century, comparative medicine deeply influenced veterinary education in Montreal, New York and Philadelphia. Of the many physicians and veterinarians involved in this movement, Sir William Osler has attracted the most biographical and historical attention. However, his contributions to comparative medicine have been characterized inexactly, partly because of his later prominence as a clinician and partly because little has been written about the history of veterinary education in Quebec.

Osler's teaching and research in comparative medicine as well as his efforts to promote a veterinary profession are described and set alongside the work of other physicians and veterinarians who were his contemporaries. As a result, Osler's contributions to comparative medicine are seen to be many and important but by no means unique. Other Quebec veterinarians, including Duncan McEachran, Orphyr Bruneau, Victor T. Daubigny and J.A. Couture, and such physicians as T. Wesley Mills and J. George Adami made as many, and in some cases greater, contributions to veterinary education in Quebec than did Osler. That they have not received the degree of recognition that Osler has received reveals Osler's ability to represent values and ideals and draws attention to some essential features of late nineteenth-century comparative medicine.

  相似文献   
998.
999.
Torsion of abdominal organs in sows: a report of 36 cases   总被引:3,自引:3,他引:0       下载免费PDF全文
Necropsy records of 36 sows with torsion of abdominal organs involving individually the stomach, the spleen, a liver lobe or the intestine were reviewed for the years 1970 to 1983, and the age, the clinical signs and the gross lesions were recorded. These acute abdominal accidents were characterized clinically by sudden death. Dry sows from large breeding units were affected. Twenty-six cases were diagnosed between January 1981 and December 1983 while only ten cases had been seen between 1970 and 1980. Gastric torsion was the most common condition (40% of the cases) and the other three conditions were equally represented (20% each). Management practises that could be responsible for the apparent increase in occurrence of this problem are discussed.  相似文献   
1000.
A review of the principles of cancer chemotherapy for pet animals is presented. The various pharmacological classes of antineoplastic drugs are described with specific references to those drugs that have been widely used in veterinary medicine.  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