全文获取类型
收费全文 | 264061篇 |
免费 | 15982篇 |
国内免费 | 7857篇 |
专业分类
林业 | 30301篇 |
农学 | 24540篇 |
基础科学 | 8881篇 |
50184篇 | |
综合类 | 27451篇 |
农作物 | 19938篇 |
水产渔业 | 17241篇 |
畜牧兽医 | 74904篇 |
园艺 | 7981篇 |
植物保护 | 26479篇 |
出版年
2022年 | 2884篇 |
2021年 | 4787篇 |
2020年 | 5013篇 |
2019年 | 5621篇 |
2018年 | 5063篇 |
2017年 | 6042篇 |
2016年 | 6605篇 |
2015年 | 6842篇 |
2014年 | 8020篇 |
2013年 | 19193篇 |
2012年 | 8553篇 |
2011年 | 10378篇 |
2010年 | 10599篇 |
2009年 | 10932篇 |
2008年 | 9135篇 |
2007年 | 8494篇 |
2006年 | 9080篇 |
2005年 | 7984篇 |
2004年 | 6176篇 |
2003年 | 5727篇 |
2002年 | 4819篇 |
2001年 | 5073篇 |
2000年 | 5073篇 |
1999年 | 5552篇 |
1998年 | 5508篇 |
1997年 | 5338篇 |
1996年 | 4975篇 |
1995年 | 5407篇 |
1994年 | 4661篇 |
1993年 | 4316篇 |
1992年 | 3901篇 |
1991年 | 3858篇 |
1990年 | 3488篇 |
1989年 | 3301篇 |
1988年 | 2840篇 |
1987年 | 2800篇 |
1986年 | 2544篇 |
1985年 | 2888篇 |
1984年 | 2895篇 |
1983年 | 2829篇 |
1982年 | 2521篇 |
1981年 | 2507篇 |
1980年 | 2488篇 |
1979年 | 2405篇 |
1978年 | 2284篇 |
1977年 | 2202篇 |
1976年 | 2051篇 |
1975年 | 1795篇 |
1974年 | 1800篇 |
1973年 | 1751篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
51.
Fang Chen Hao Zhang Na Zhao Xuehai Yang Encun Du Shaowen Huang Wanzheng Guo Wei Zhang Jintao Wei 《Animal Science Journal》2021,92(1):e13619
Heat stress in poultry is deleterious to productive performance. Chlorogenic acid (CGA) exerts antibacterial, anti-inflammatory, and antioxidant properties. This study was conducted to evaluate the effects of dietary supplemental CGA on the intestinal health and cecal microbiota composition of young hens challenged with acute heat stress. 100-day-old Hy-line brown pullets were randomly divided into four groups. The control group (C) and heat stress group (HS) received a basal diet. HS + CGA300 group and HS + CGA600 group received a basal diet supplemented with 300- and 600-mg/kg CGA, respectively, for 2 weeks before heat stress exposure. Pullets of HS, HS + CGA300, and HS + CGA600 group were exposed to 38°C for 4 h while the control group was maintained at 25°C. In this study, dietary CGA supplementation had effect on mitigate the decreased T-AOC and T-SOD activities and the increasing of IL-1β and TNFα induced by acute heat stress. Dietary supplementation with 600 mg/kg CGA had better effect on increasing the relative abundance of beneficial bacterial genera, such as Rikenellaceae RC9_gut_group, Ruminococcaceae UCG-005, and Christensenellaceae R-7_group, and deceasing bacteria genera involved in inflammation, such as Sutterella species. Therefore, CGA can ameliorate acute heat stress damage through suppressing inflammation and improved antioxidant capacity and cecal microbiota composition. 相似文献
52.
53.
Osteomyelitis caused by Cryptococcus neoformans was diagnosed in a three-year-old male Irish wolfhound. The case details and radiological findings of radiolucency and periosteal reaction of the left third metatarsal bone had lead to an initial diagnosis of a malignant bone tumour. Biopsy revealed a fungal granuloma and culture identified the causal organism. A four month course of ketaconazole was instigated and the lameness resolved. Twelve months after the end of treatment there was no recurrence of the problem. 相似文献
54.
55.
Differences in gas exchange parameters i.e. carbon exchange rate (CER), transpiration (Tr), water vapor conductance (g) were investigated, under a controlled environment, in a semi-dwarf (SD) Triticum aestivum line, its tall (TL) near isoline and the Payne (PA) variety characterized by small leaves. The plants were maintained in: (a) optimal substrate moisture condition (CTR); (b) salinized by watering with a 0.12 m NaCl solution (SLT); (c) water stressed by withholding waterings during a period of six days (STR); (d) stressed and salinized during the same period and with the same saline solution (S + S). CER and Tr were negatively affected by the stresses; SLT and S + S treatments had a higher WUE compared to their respective controls CTR and STR.
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO2 concentration curves contributed to explaining the SD performance. 相似文献
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO
56.
阐述了某工程由于施工原因,导致预应力混凝土工字形屋面梁强度不足的预制构件的检验鉴定过程和方法。采用回弹法推定混凝土实际强度;通过静载试验测试构件的实际挠度、抗裂和承载能力。分析了导致混凝土强度不足的原因。 相似文献
57.
58.
呼和浩特市大气污染状况的研究及遥感信息的利用 总被引:1,自引:0,他引:1
利用遥感技术结合地物波谱测定和叶表面内大气污染元素的含量测定分析研究大气污染是一种有效可靠的方法。克服了常规大气监测的弊病。充分显示了快速、准确的优越性。为城市规划和环境的综合治理提供了可靠的科学依据。 相似文献
59.
Abstract. A humoral antibody response was demonstrated by ELISA in rainbow trout immunized intraperitoneally with extracts from the branchiuran ectoparasite Argulus foliaceus. A similar immunization protocol produced a higher titre response in a rabbit. Both trout and rabbit identified several antigenic components on immunoblots. ELISA and immunoblotting indicated that rainbow trout and rabbit anti-A. foliaceus sera identified components from the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus. 相似文献
60.