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   178912篇
  免费   10110篇
  国内免费   111篇
林业   6878篇
农学   5631篇
基础科学   1200篇
  21655篇
综合类   30592篇
农作物   6498篇
水产渔业   9426篇
畜牧兽医   92624篇
园艺   2232篇
植物保护   12397篇
  2018年   2453篇
  2017年   2699篇
  2016年   2523篇
  2015年   2122篇
  2014年   2586篇
  2013年   6734篇
  2012年   4881篇
  2011年   6095篇
  2010年   3832篇
  2009年   3809篇
  2008年   5849篇
  2007年   5612篇
  2006年   5373篇
  2005年   4996篇
  2004年   4909篇
  2003年   4928篇
  2002年   4683篇
  2001年   5877篇
  2000年   5786篇
  1999年   4649篇
  1998年   1832篇
  1997年   1759篇
  1996年   1635篇
  1995年   2113篇
  1994年   1894篇
  1993年   1782篇
  1992年   3849篇
  1991年   4000篇
  1990年   4035篇
  1989年   3992篇
  1988年   3669篇
  1987年   3808篇
  1986年   3791篇
  1985年   3645篇
  1984年   3100篇
  1983年   2721篇
  1982年   1827篇
  1981年   1728篇
  1980年   1679篇
  1979年   2734篇
  1978年   2264篇
  1977年   1923篇
  1976年   1736篇
  1975年   1858篇
  1974年   2437篇
  1973年   2449篇
  1972年   2400篇
  1971年   2120篇
  1970年   1994篇
  1969年   1892篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
101.
Thirteen mixed-breed beef bulls, 1 to 4 years old, were used to determine the effect of live and dead filarial nematodes, Setaria labiatopapillosa, placed in the vaginal cavity of the testes. When dead worms were used, granulomatous lesions developed on the tunica vaginalis parietalis in 7 of 8 testes. The lesions were similar to those seen in some clinical cases of periorchitis. Similar lesions developed in 5 of 6 testes after live worms were implanted in the vaginal cavity of the testes and tetramisole (8 mg/kg) was injected subcutaneously 6 days after implantation. When live worms were implanted and tetramisole was not given, lesions developed in 3 of 6 testes. It was concluded that the granulomatous reaction was a local response to dead or killed S labiatopapillosa.  相似文献   
102.
GRAY  S. J.; PRICE  COLIN 《Forestry》1990,63(2):161-175
Traditional forest economics deals with regularly-ordered activities.For many reasons, however, choices must often be made amongconflicting operational priorities. In these circumstances,maximizing net discounted revenue per hectare does not maximizeglobal profit. Priorities for action should be chosen in orderof urgency index ratio, defined as the cost of delaying an operationdivided by the units of limited resource needed to undertakethe operation. Forest managers tend to use informal and sometimesconflicting rules to assign priorities among uses of limitedresources. These priorities often differ from those indicatedby urgency index ratio. Urgency index ratio can be determinedby simple calculations based on readily-available data. Theconcept can be extended to include multiple constraints.  相似文献   
103.
Washed and unwashed red blood cells (RBC) from young calves, adult cattle, hamsters and humans were incubated with Leptospira interrogans serovars pomona and ballum. Washed cells suspended in saline were always haemolysed while unwashed cells and those which were washed and resuspended in plasma were never haemolysed, despite the presence of large numbers of organisms within the culture supernatant. Pomona produced greater haemolysis of cattle and human RBC than did ballum, but with hamster RBC ballum produced greater haemolysis than did pomona. A group of 6- to 9-month-old cattle infected with pomona showed no signs of clinical disease and RBC taken from them before infection and during the development of antibodies to pomona were haemolysed by pomona only after the cells were washed. Plasma therefore appears to have a protective function. This in vitro protective function of plasma even extended to plasma from young seronegative calves.  相似文献   
104.
105.
106.
107.
108.
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