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   331264篇
  免费   17357篇
  国内免费   699篇
林业   25151篇
农学   14379篇
基础科学   3024篇
  48984篇
综合类   43141篇
农作物   17977篇
水产渔业   18927篇
畜牧兽医   144668篇
园艺   6616篇
植物保护   26453篇
  2019年   3838篇
  2018年   4744篇
  2017年   5199篇
  2016年   5280篇
  2015年   4616篇
  2014年   6010篇
  2013年   16621篇
  2012年   8896篇
  2011年   11515篇
  2010年   8667篇
  2009年   8974篇
  2008年   10776篇
  2007年   10115篇
  2006年   10111篇
  2005年   9371篇
  2004年   9110篇
  2003年   8981篇
  2002年   8160篇
  2001年   9161篇
  2000年   8943篇
  1999年   7725篇
  1998年   4443篇
  1997年   4494篇
  1996年   4212篇
  1995年   4893篇
  1994年   4269篇
  1993年   3946篇
  1992年   6071篇
  1991年   6350篇
  1990年   6180篇
  1989年   6171篇
  1988年   5533篇
  1987年   5552篇
  1986年   5537篇
  1985年   5589篇
  1984年   4890篇
  1983年   4490篇
  1982年   3445篇
  1981年   3232篇
  1980年   3171篇
  1979年   4356篇
  1978年   3680篇
  1977年   3327篇
  1976年   3173篇
  1975年   3168篇
  1974年   3499篇
  1973年   3585篇
  1972年   3266篇
  1971年   3095篇
  1970年   3075篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
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   
54.
55.
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   
56.
57.
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   
58.
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   
59.
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   
60.
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