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   278895篇
  免费   15563篇
  国内免费   687篇
林业   24059篇
农学   14091篇
基础科学   2986篇
  44969篇
综合类   30071篇
农作物   17544篇
水产渔业   17470篇
畜牧兽医   112828篇
园艺   6400篇
植物保护   24727篇
  2021年   2513篇
  2020年   2922篇
  2019年   3740篇
  2018年   4314篇
  2017年   4735篇
  2016年   4946篇
  2015年   4382篇
  2014年   5748篇
  2013年   16310篇
  2012年   7278篇
  2011年   9525篇
  2010年   7850篇
  2009年   8387篇
  2008年   8907篇
  2007年   7969篇
  2006年   8306篇
  2005年   7630篇
  2004年   7405篇
  2003年   7190篇
  2002年   6404篇
  2001年   7023篇
  2000年   6809篇
  1999年   6116篇
  1998年   4222篇
  1997年   4281篇
  1996年   3996篇
  1995年   4656篇
  1994年   4012篇
  1993年   3705篇
  1992年   4817篇
  1991年   4994篇
  1990年   4696篇
  1989年   4682篇
  1988年   4139篇
  1987年   4172篇
  1986年   4175篇
  1985年   4419篇
  1984年   3991篇
  1983年   3706篇
  1982年   3018篇
  1981年   2874篇
  1980年   2871篇
  1979年   3555篇
  1978年   3114篇
  1977年   2850篇
  1976年   2731篇
  1975年   2648篇
  1974年   2835篇
  1973年   2813篇
  1972年   2460篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
The examination of the foot must be based on observations of the hoof, followed by a careful determination of areas of pain. This must be followed by an assessment of the biomechanical forces on the hoof and limb. Finally, imaging gives insight into the nature of the injury and allows the examiner to prognosticate the outcome.  相似文献   
36.
37.
38.
Over 54,600 ha of table grapes (Vitis vinifera), mainly cvs. ‘Thompson Seedless’, ‘Flame Seedless’ and ‘Redglobe’, are planted in Chile. Almost the entire production is exported to the USA, Europe, Asia, or one of several Latin American countries, which typically requires 15–40 d of maritime transportation. During this period, several physical, physiological, and pathological factors cause table grape deterioration. Because berry size is the main quality factor in international markets, farmers often overuse the growth regulators, gibberellic acid (GA3) and forchlorfenuron (CPPU), in an effort to increase berry size. We examined the effect of preharvest growth regulators on seedless (‘Thompson Seedless’, and ‘Ruby Seedless’) and seeded (‘Redglobe’) table grape cultivars during cold (0 °C) storage plus a shelf life period of 3 d at 20 °C. The overuse of GA3, eight instead of two GA3 applications on Thompson Seedless, and the use of one GA3 application on Redglobe and ‘Ruby Seedless’, increased berry pedicel thickness and lowered cuticle content but induced shatter and predisposed grapes to gray mold caused by Botrytis cinerea. In contrast, CPPU increased berry pedicel thickness and cuticle content but did not increase shatter or gray mold incidence. Clusters that were subjected to overuse of combined GA3 and CPPU were highly sensitive to shatter, had the thickest pedicel, and developed a high gray mold incidence during cold storage. Hairline, a fine cracking developed during cold storage, was induced on ‘Thompson Seedless’ and ‘Ruby Seedless’ by growth regulators, but no hairline occurred on ‘Redglobe’ table grapes. Therefore, berry quality during cold storage is greatly influenced by growth regulator management in the vineyard.  相似文献   
39.
The association of tumor-associated antigen (TAA) on the proliferation of BLV-infected lymphoblastoid B-cell lines (BL2M3 and BL312) was investigated. Flow cytometric analysis of the expression of TAA with monoclonal antibody (mAb) c143 showed high expression of TAA on the surfaces of BL2M3 and BL312 cells. A large amount of TAA was found in the culture supernatant of BL2M3 and BL312 cells as well as in the lysates of BL2M3 and BL312 cells. Culture supernatant but not lysates of BL2M3 and BL312 cells promoted the growth of either BL2M3 cells or BL312 cells. Furthermore, this growth promoting activity in culture supernatants of BL2M3 and BL312 cells was inhibited in a dose-dependent manner when cultured with mAb c143. These results suggested that TAA may be involved in the growth factor-mediated cell growth of bovine B-lymphoblastoid cell lines expressing TAA on their cell surface.  相似文献   
40.
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