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   2175篇
  免费   102篇
  国内免费   69篇
林业   76篇
农学   68篇
基础科学   25篇
  154篇
综合类   1035篇
农作物   47篇
水产渔业   32篇
畜牧兽医   861篇
园艺   22篇
植物保护   26篇
  2024年   12篇
  2023年   24篇
  2022年   32篇
  2021年   54篇
  2020年   65篇
  2019年   82篇
  2018年   41篇
  2017年   50篇
  2016年   83篇
  2015年   78篇
  2014年   150篇
  2013年   145篇
  2012年   161篇
  2011年   163篇
  2010年   144篇
  2009年   142篇
  2008年   115篇
  2007年   124篇
  2006年   108篇
  2005年   88篇
  2004年   129篇
  2003年   95篇
  2002年   30篇
  2001年   27篇
  2000年   24篇
  1999年   23篇
  1998年   16篇
  1997年   16篇
  1996年   15篇
  1995年   20篇
  1994年   17篇
  1993年   21篇
  1992年   14篇
  1991年   13篇
  1990年   5篇
  1988年   2篇
  1987年   4篇
  1986年   1篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1980年   2篇
排序方式: 共有2346条查询结果,搜索用时 62 毫秒
31.
本研究遵循动物福利"5F"原则,结合150家规模化奶牛养殖场实地调研数据,构建奶牛场动物福利评价体系,测度动物福利水平,并进一步建立嵌入动物福利水平测度值的规模化奶牛养殖场收入函数,验证关联效应。结果表明:生理福利和环境福利是影响我国规模化奶牛养殖场动物福利的最重要的2个维度,受访的规模化奶牛养殖场生理福利和环境福利的平均水平较高,卫生福利亟待提升,生理福利、环境福利、卫生福利和行为福利对规模化奶牛养殖场经济效益有积极作用。  相似文献   
32.
动物通过皮毛携带、搬运等方式对种子在空间上的扩散产生不同影响,是植物种子实现远距离扩散的重要途径。以草原毒害草醉马草(Achnatherum inebrians)为研究材料,采用野外模拟及控制性试验,测定了马、牛、羊皮毛附着和保留种子的能力,以及鼠类、蚂蚁对种子的搬运能力,分析动物对醉马草种子的扩散规律。结果表明,马、牛、羊模型种子的附着率:羊 > 牛 > 马(P<0.05),种子掉落率:羊 < 牛 < 马(P<0.05);随着行走天数的延长,种子在马、牛、羊皮毛上的附着率呈下降趋势。马的背部以及牛、羊的背、侧部最易附着种子;种子的侧部最易附着在皮毛上,以种子顶部附着的种子最不易掉落。24 h内鼠类、蚂蚁对种子的扩散范围分别为0~15 cm和0~40 cm。综上所述,家畜对醉马草种子起到远距离扩散作用,且羊比马、牛更容易增加种子的扩散强度。蚂蚁、鼠类对醉马草种子起到短距离扩散作用。  相似文献   
33.
The objective of this study was to develop equations for estimating ileal digestible crude protein (CP) and metabolizable energy (ME) contents of meat meal (MM) and meat and bone meal (MBM) as feed ingredients for pigs based on in vitro assays. Test ingredients were 4 sources of MM and 3 sources of MBM. Ash and CP contents of the ingredients ranged from 3.8% to 33.1% and 46.8% to 82.9% (as-is basis), respectively. In vitro ileal disappearance (IVID) of CP was determined and ileal digestible CP content was calculated by multiplying CP content by IVID of CP. In vitro total tract disappearance (IVTTD) of dry matter (DM) was determined and ME was calculated using gross energy, CP contents, and IVTTD of DM. The IVID of CP and IVTTD of DM ranged from 77.2% to 88.7% and from 82.7% to 92.4%, respectively. Calculated ileal digestible CP and ME contents ranged from 37.8% to 73.5% DM and 2,405 to 3,905 kcal/kg DM, respectively. Ash contents were negatively correlated (P < 0.001) with CP (r = −0.99), in vitro ileal digestible CP (r = −0.97), gross energy (r = −1.00), in vitro digestible energy (r = −0.97), and adjusted ME (r = −0.97). The most fitting equations for ileal digestible CP and adjusted ME were: ileal digestible CP (% DM) = 11.91 − 0.90 × Ash (% DM) + 0.74 × IVID of CP (%) (R2 = 0.99) and adjusted ME (kcal/kg DM) = 130.85 − 50.90 × ash (% DM) + 47.06 × IVTTD of DM (%) (R2 = 0.99). To validate the accuracy of the prediction equations for ME, mean bias and linear bias were determined using a regression analysis. Calculated ME values of MM and MBM were in a good agreement with data obtained from animal experiments based on a statistically insignificant bias in the models. In conclusion, ME concentrations of MM and MBM as swine feed ingredients can be calculated using ash concentration and in vitro disappearance of dry matter.  相似文献   
34.
35.
Oral infection of goats with Mycobacterium avium subsp. hominissuis (MAH) resulted in a large variety of granulomas in organized gut-associated lymphatic tissues and intestinal lymph nodes. To characterize the cellular composition of granulomas, CD4+, CD8+, γδ, B lymphocytes and plasma, CD25+, CD68+, MHC-II+, Ki67+ and endothelial cells were labeled in consecutive frozen sections by immunohistochemistry and acid fast bacilli (AFB) by Kinyoun stain. Granulomas with extensive necrosis, little mineralization and variable numbers of AFB surrounded by many CD4+ T cells, but only few epitheloid macrophages were observed in severely sick goats at 2–3 mpi. They were interpreted as exuberant immune reaction. Organized granulomas with very few AFB were seen in clinically healthy goats at 13 mpi. The necrotic cores were surrounded by a zone of granulomatous infiltrate with many epitheloid macrophages and few lymphocytes. This zone was initially wide and highly vascularized and became progressively smaller. It was enclosed by an increasing layer of connective tissue. All organized granulomas were surrounded by compartimentalized tertiary lymphoid tissue. The granulomas in experimental infection of goats with MAH reflect the heterogeneity of lesions seen in mycobacterial infections of humans and ruminants and are therefore valuable for comparative research.  相似文献   
36.
In Burkina Faso, we assessed the efficacy of treating cattle with a footbath containing aqueous formulations of pyrethroids to control two tsetse-fly species, Glossina tachinoides Westwood, 1850 (Diptera, Glossinidae) and Glossina palpalis gambiensis Vanderplank 1949. Legs were the most targeted parts of the body for tsetse-fly blood meals: 81% (95% CI: 73, 89) for G. tachinoides and 88% (81, 95) for G. palpalis.

The in-stable efficacy of footbath treatments was compared with manual full spraying with a 0.005% alphacypermethrin (Dominex, FMC, Philadelphia, USA) formulation (250 mL versus 2 L). The proportions of knocked-down flies were the same with footbath and full spray but the latter was more protective against fly bites. In field use, the efficacy of both methods should be similar given the recommended treatment frequency: 3 days for footbath versus 7 days for full spray.

Among 96 cattle drinking at the same water point in Dafinso (Burkina Faso), 68 (71%) were treated with a footbath containing a 0.005% deltamethrin formulation (Vectocid, CEVA SA, Libourne, France). We observed the effect of this live-bait technique on the one hand on released cohorts of reared, irradiated flies, and on the other hand on wild tsetse flies. In both cases, the footbath treatment was associated with a reduction of the apparent fly density probably related to an increased mortality.  相似文献   

37.
All feces produced during 24 h were collected from five pigs and cortisol and immunoreactive cortisol metabolites (CICM), and IgA were quantified. Within pigs, the concentrations of CICM and IgA varied extensively between random samples obtained from a single fecal dropping, and deviated in most cases significantly from the true concentration measured in total fecal output (CV 6.7-130%). The CICM and IgA contents varied considerably (CV 8.1-114%) within and between individual fecal droppings from the same pig compared to the total fecal excretion. In conclusion, single random samples could not be used to reliably quantify the total fecal concentration or excretion of CICM or IgA in pigs. Analyses of all feces collected during shorter periods than 24 h did not provide an accurate estimate of the daily excretion of CICM. Thus, the concentration of stress sensitive molecules in random single fecal samples as an indicator of animal welfare should be interpreted with prudence.  相似文献   
38.
39.
提高农业科技服务能力 推进农村小康社会建设   总被引:1,自引:0,他引:1  
中国全面建设小康社会重点在农村,难点在如何增加农民收入,很大程度上取决于如何为八亿农民提供农业科技服务,促进农业技术创新和科技成果转化为现实生产力。本文从中国农业生产的现状、科技服务“缺位和滞后”和力量不足等问题入手,提出改革现行的农业科技运行和转化机制、开展科农携手共建利益共同体、发挥示范榜样作用、提高劳动者的科技素质等对策,促进科学研究面向生产第一线和科技成果直接应用于生产,为农民提供全方位、多层次、多领域的科技服务,推进农村全面建设小康社会进程。  相似文献   
40.
王忠霞 《农业图书情报学刊》2010,22(11):253-254,257
利用调查分析的方法对2009年《图书馆学刊》栏目设置情况进行了详细的描述,《学刊》栏目数量适当,结构合理,展示了整体性、灵活性和科学性的特点,突出了学术性、先进性和继承性的特色。  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