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   155492篇
  免费   7999篇
  国内免费   85篇
林业   7815篇
农学   5098篇
基础科学   1065篇
  19485篇
综合类   26215篇
农作物   6209篇
水产渔业   7436篇
畜牧兽医   78662篇
园艺   2299篇
植物保护   9292篇
  2018年   2906篇
  2017年   3085篇
  2016年   2464篇
  2015年   1771篇
  2014年   2025篇
  2013年   5695篇
  2012年   4203篇
  2011年   5669篇
  2010年   4159篇
  2009年   3901篇
  2008年   5338篇
  2007年   5273篇
  2006年   4213篇
  2005年   3980篇
  2004年   3978篇
  2003年   3965篇
  2002年   3784篇
  2001年   4896篇
  2000年   4836篇
  1999年   3681篇
  1998年   1569篇
  1997年   1552篇
  1996年   1417篇
  1995年   1725篇
  1994年   1584篇
  1993年   1544篇
  1992年   3246篇
  1991年   3498篇
  1990年   3473篇
  1989年   3451篇
  1988年   3155篇
  1987年   3223篇
  1986年   3292篇
  1985年   3164篇
  1984年   2607篇
  1983年   2292篇
  1982年   1572篇
  1981年   1456篇
  1979年   2346篇
  1978年   1892篇
  1977年   1513篇
  1976年   1520篇
  1975年   1552篇
  1974年   1994篇
  1973年   2071篇
  1972年   2064篇
  1971年   1985篇
  1970年   1864篇
  1969年   1698篇
  1967年   1487篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
A four month old female toy Poodle showing multiple nodules 2 to 3 cm in diameter, some of which had ruptured over the neck and trunk area, was diagnosed as having nodular panniculitis. The animal had been treated with a course of chloramphenicol and ampicillin for one month with no response. The diagnosis was based on history, clinical signs, laboratory data and dramatic response to the addition of corticosteroid to the antibiotic therapy.  相似文献   
992.
993.
994.
A herd of 180 beef cows was synchronized with prostaglandin and bred by artifical insemination for five successive years. Factors influencing the success or failure of estrus synchronizing programs were identified, including the management of nutrition, postpartum interval, cow age and artificial insemination technology. Specific recommendations on the management of prostaglandin-controlled breeding programs resulted in improving the pregnancy rates from 33% in year 1 to 67% in year 5. Improved management and close veterinary supervision were shown to improve the success of an estrus synchronization program.  相似文献   
995.
Alkaline phosphatase (APase) activity in tissue samples, with adherent bacteria, was measured from two sites in the rumen and from two sites in the abomasum of 57 yearling Angus and Hereford bulls and heifers fed a high or a low energy diet. In the rumen, APase activity was higher at the caudoventral blind sac than at the dorsal sac in animals of both breeds fed the high energy diet and in Angus bulls fed the low energy diet, but the reverse was observed in Hereford bulls fed the low-energy diet (P less than .01). In the abomasum, APase levels were higher for bulls than heifers (P less than .01) and higher at the fundic than at the pyloric region (P less than .01). Morphological studies also showed that rumen samples from animals fed a high energy diet exhibited a more widely distributed APase activity and an increase in the digestive recycling of epithelial cells that produced some "pitting" of the tissue. The higher APase activity of the epithelial tissue of animals fed the high energy diet may be explained by the greater rate of cell death and renewal indicated by the higher mitotic index reported by other researchers who have studied the cell cycle of the rumen epithelium in ruminants fed high and low energy diets.  相似文献   
996.
A condition resembling chronic malignant catarrhal fever was seen in a 9-month-old pet sika hind (Cervus nippon). From an initial acute depression, pyrexia, and anorexia, the condition progressed to include hypopyon, keratitis, lethargy, loss of condition, sloughing of one hoof and eventually death after seven weeks. There were multiple, 5 to 8mm diameter dark-red nodules throughout the mesenteries and mediastinum, along abdominal organ ligaments, and about the uterus and kidneys. Histopathology showed the nodules to be organising vascular thrombi. Concurrent perivascular mononuclear infiltrations and intravascular thrombi in many tissues confirmed that the condition was malignant catarrhal fever.  相似文献   
997.
998.
999.
1000.
Year end tax planning   总被引:1,自引:1,他引:0       下载免费PDF全文
  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