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   339659篇
  免费   18220篇
  国内免费   720篇
林业   25043篇
农学   14309篇
基础科学   3031篇
  48805篇
综合类   48976篇
农作物   17790篇
水产渔业   18804篇
畜牧兽医   148492篇
园艺   6637篇
植物保护   26712篇
  2019年   3830篇
  2018年   4634篇
  2017年   5134篇
  2016年   5224篇
  2015年   4585篇
  2014年   5962篇
  2013年   16655篇
  2012年   8769篇
  2011年   11385篇
  2010年   8495篇
  2009年   8849篇
  2008年   10661篇
  2007年   9889篇
  2006年   10080篇
  2005年   9348篇
  2004年   9126篇
  2003年   8907篇
  2002年   8225篇
  2001年   9294篇
  2000年   8927篇
  1999年   7680篇
  1998年   4477篇
  1997年   4516篇
  1996年   4235篇
  1995年   4963篇
  1994年   4391篇
  1993年   4068篇
  1992年   6290篇
  1991年   6540篇
  1990年   6344篇
  1989年   6308篇
  1988年   5727篇
  1987年   5778篇
  1986年   5881篇
  1985年   5941篇
  1984年   5206篇
  1983年   4746篇
  1982年   3652篇
  1981年   3450篇
  1980年   3394篇
  1979年   4764篇
  1978年   4077篇
  1977年   3641篇
  1976年   3398篇
  1975年   3446篇
  1974年   4022篇
  1973年   4040篇
  1972年   3722篇
  1971年   3512篇
  1970年   3362篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
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   
105.
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   
106.
107.
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   
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