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   282377篇
  免费   15984篇
  国内免费   656篇
林业   24278篇
农学   14190篇
基础科学   2978篇
  45529篇
综合类   27829篇
农作物   17603篇
水产渔业   17674篇
畜牧兽医   117737篇
园艺   6413篇
植物保护   24786篇
  2021年   2551篇
  2020年   2957篇
  2019年   3710篇
  2018年   4362篇
  2017年   4741篇
  2016年   5027篇
  2015年   4474篇
  2014年   5911篇
  2013年   16477篇
  2012年   7584篇
  2011年   9689篇
  2010年   7981篇
  2009年   8490篇
  2008年   9025篇
  2007年   8239篇
  2006年   8545篇
  2005年   7741篇
  2004年   7569篇
  2003年   7480篇
  2002年   6685篇
  2001年   7574篇
  2000年   7256篇
  1999年   6504篇
  1998年   4285篇
  1997年   4337篇
  1996年   4080篇
  1995年   4642篇
  1994年   4050篇
  1993年   3734篇
  1992年   5032篇
  1991年   5264篇
  1990年   5067篇
  1989年   5056篇
  1988年   4475篇
  1987年   4497篇
  1986年   4346篇
  1985年   4538篇
  1984年   4137篇
  1983年   3841篇
  1982年   3069篇
  1981年   2917篇
  1980年   2865篇
  1979年   3489篇
  1978年   3041篇
  1977年   2812篇
  1976年   2628篇
  1975年   2505篇
  1974年   2671篇
  1973年   2754篇
  1972年   2449篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
植物健康综合管理系统(IpHM)在保证根系健康生长方面确实起到了作用。这就对种植者提出了挑战。植物营养调节、水分管理、根/冠生长管理的成败取决于是否有健康的根系和成分配比适当的栽培基质。[编者按]  相似文献   
72.
73.
74.
The parasympathetic and sympathetic divisions of the autonomic nervous system are involved in homeostatic control of a wide variety of ocular functions, including accommodation, pupillomotor control, lacrimation, eyelid position, and aqueous humor production. Familiarity with the functional anatomy of the autonomic nervous system is paramount to the understanding and application of the large number of autonomic drugs used in veterinary ophthalmology. The cholinergic and adrenergic agents discussed in this article are commonly employed to facilitate routine ophthalmic examination, in the diagnosis of autonomic dysfunction, and in the treatment of a variety of ocular diseases.  相似文献   
75.
76.
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   
77.
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   
78.
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   
79.
80.
1. White blood cell responses of broilers, turkeys and ducks were examined at regular intervals after being subjected to various degrees of food restriction. 2. Restricted-fed broilers showed increases in heterophil and basophil numbers, together with a corresponding decrease in lymphocytes. The heterophil/lymphocyte ratio was raised. There were no differences between broiler strains. 3. After only one week of feeding restricted diets, heterophils were significantly raised in selected and unselected 2-week-old ducks. At 21 weeks of age, those ducks receiving 50% of food required to achieve their ad libitum-fed body weight had raised heterophils. 4. Ducks receiving food to achieve 25% of ad libitum-fed birds produced a marked basophilia, but no heterophilia. 5. After two weeks of food restriction, turkeys responded with significant heterophil/lymphocyte ratios following two degrees of restricted feeding. 6. It was concluded that in some poultry, a heterophilia may be the response to mild to moderate stress but a basophilia may result after severely stressing birds.  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