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   295482篇
  免费   16817篇
  国内免费   1401篇
林业   24720篇
农学   14951篇
基础科学   3525篇
  45963篇
综合类   36121篇
农作物   17480篇
水产渔业   17661篇
畜牧兽医   121151篇
园艺   6626篇
植物保护   25502篇
  2020年   3116篇
  2019年   3899篇
  2018年   4253篇
  2017年   4703篇
  2016年   5085篇
  2015年   4636篇
  2014年   6002篇
  2013年   16724篇
  2012年   7523篇
  2011年   9667篇
  2010年   7920篇
  2009年   8442篇
  2008年   8944篇
  2007年   8069篇
  2006年   8725篇
  2005年   7916篇
  2004年   7570篇
  2003年   7290篇
  2002年   6752篇
  2001年   7631篇
  2000年   7263篇
  1999年   6627篇
  1998年   4455篇
  1997年   4507篇
  1996年   4214篇
  1995年   4841篇
  1994年   4283篇
  1993年   3961篇
  1992年   5395篇
  1991年   5595篇
  1990年   5395篇
  1989年   5313篇
  1988年   4823篇
  1987年   4869篇
  1986年   4881篇
  1985年   5008篇
  1984年   4534篇
  1983年   4179篇
  1982年   3313篇
  1981年   3170篇
  1980年   3126篇
  1979年   3963篇
  1978年   3480篇
  1977年   3157篇
  1976年   2856篇
  1975年   2781篇
  1974年   3309篇
  1973年   3302篇
  1972年   3045篇
  1971年   2860篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
172.
173.
174.
175.
176.
Ohne Zusammenfassung Mit 2 Abbildungen  相似文献   
177.
178.
Isolated dog neutrophils exposed to known chemotactic factors assumed a bipolar configuration in suspension. This response was initiated within 2 minutes with a gradual return to spherical shape. The rate of return to sphere was positively correlated with the dose of stimulant. Dog neutrophils exposed to N-formylmethionyl-leucyl-phenylalanine (fMLP) did not adapt to bipolar conformation and did not bind radiolabeled fMLP. These findings are consistent with other species (pig and cow) that also did not respond to fMLP.  相似文献   
179.
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   
180.
Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.  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