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   356175篇
  免费   18541篇
  国内免费   705篇
林业   25563篇
农学   14438篇
基础科学   3025篇
  50176篇
综合类   51715篇
农作物   17987篇
水产渔业   19367篇
畜牧兽医   159139篇
园艺   6733篇
植物保护   27278篇
  2019年   3825篇
  2018年   4826篇
  2017年   5208篇
  2016年   5370篇
  2015年   4693篇
  2014年   6103篇
  2013年   16858篇
  2012年   9239篇
  2011年   11880篇
  2010年   8733篇
  2009年   8980篇
  2008年   11117篇
  2007年   10469篇
  2006年   10593篇
  2005年   9780篇
  2004年   9605篇
  2003年   9454篇
  2002年   8683篇
  2001年   10013篇
  2000年   9610篇
  1999年   8281篇
  1998年   4551篇
  1997年   4590篇
  1996年   4317篇
  1995年   4976篇
  1994年   4443篇
  1993年   4131篇
  1992年   6696篇
  1991年   7076篇
  1990年   6953篇
  1989年   6902篇
  1988年   6339篇
  1987年   6368篇
  1986年   6381篇
  1985年   6391篇
  1984年   5542篇
  1983年   5085篇
  1982年   3794篇
  1981年   3598篇
  1980年   3510篇
  1979年   4998篇
  1978年   4222篇
  1977年   3790篇
  1976年   3534篇
  1975年   3542篇
  1974年   4221篇
  1973年   4265篇
  1972年   3965篇
  1971年   3740篇
  1970年   3701篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
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   
46.
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   
47.
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   
48.
49.
50.
Rostral and caudal rhinoscopy in dogs and cats facilitates the investigation of the nasal cavity and accurate biopsy. Rostral rhinoscopy can be performed by rigid endoscopes; caudal rhinoscopy requires flexible endoscopes. Deep anaesthesia or additional analgesia with local anaesthesia is necessary. The nasal cavity is assessed by its form, colour, surface of the mucous membrane, hyperemia, plaques, lesions, and the secretion is assessed by its quantity, colour and viscosity. Foreign bodies and neoplasia must also be looked for. Case reports with abnormal findings are described.  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