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   323112篇
  免费   17127篇
  国内免费   703篇
林业   24808篇
农学   14241篇
基础科学   3022篇
  47550篇
综合类   44331篇
农作物   17794篇
水产渔业   18327篇
畜牧兽医   138481篇
园艺   6549篇
植物保护   25839篇
  2019年   3792篇
  2018年   4516篇
  2017年   4994篇
  2016年   5105篇
  2015年   4520篇
  2014年   5874篇
  2013年   16502篇
  2012年   8232篇
  2011年   10734篇
  2010年   8286篇
  2009年   8678篇
  2008年   10103篇
  2007年   9215篇
  2006年   9389篇
  2005年   8758篇
  2004年   8522篇
  2003年   8282篇
  2002年   7545篇
  2001年   8482篇
  2000年   8324篇
  1999年   7139篇
  1998年   4390篇
  1997年   4432篇
  1996年   4177篇
  1995年   4903篇
  1994年   4306篇
  1993年   3980篇
  1992年   5919篇
  1991年   6235篇
  1990年   5942篇
  1989年   5881篇
  1988年   5309篇
  1987年   5361篇
  1986年   5492篇
  1985年   5570篇
  1984年   4870篇
  1983年   4501篇
  1982年   3418篇
  1981年   3257篇
  1980年   3221篇
  1979年   4445篇
  1978年   3804篇
  1977年   3326篇
  1976年   3247篇
  1975年   3235篇
  1974年   3675篇
  1973年   3765篇
  1972年   3434篇
  1971年   3353篇
  1970年   3215篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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   
42.
43.
44.
45.
46.
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   
47.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.  相似文献   
48.
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   
49.
50.
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