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   3835篇
  免费   187篇
  国内免费   3篇
林业   265篇
农学   108篇
基础科学   29篇
  663篇
综合类   597篇
农作物   133篇
水产渔业   353篇
畜牧兽医   1564篇
园艺   105篇
植物保护   208篇
  2024年   5篇
  2023年   19篇
  2022年   41篇
  2021年   81篇
  2020年   92篇
  2019年   119篇
  2018年   109篇
  2017年   117篇
  2016年   100篇
  2015年   68篇
  2014年   103篇
  2013年   153篇
  2012年   239篇
  2011年   292篇
  2010年   168篇
  2009年   147篇
  2008年   280篇
  2007年   279篇
  2006年   265篇
  2005年   264篇
  2004年   244篇
  2003年   214篇
  2002年   197篇
  2001年   30篇
  2000年   27篇
  1999年   35篇
  1998年   28篇
  1997年   24篇
  1996年   23篇
  1995年   29篇
  1994年   18篇
  1993年   26篇
  1992年   18篇
  1991年   13篇
  1990年   14篇
  1989年   11篇
  1988年   16篇
  1987年   26篇
  1986年   12篇
  1985年   8篇
  1984年   17篇
  1983年   9篇
  1982年   7篇
  1981年   2篇
  1977年   6篇
  1975年   2篇
  1973年   4篇
  1971年   2篇
  1938年   2篇
  1904年   2篇
排序方式: 共有4025条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
55.
Within the past several decades, the number of Ehrlichia spp. recognized to infect cats, dogs, and human beings has expanded substantially. The recent application of advanced techniques in molecular biology has changed how ehrlichiosis is diagnosed and has provided new tools for the assessment of treatment. As these techniques are applied, the numerous questions that relate to the management of dogs and cats with ehrlichiosis ultimately will be answered. We hope this consensus statement will assist veterinarians in the management of their patients.  相似文献   
56.
OBJECTIVES: To review information on the pathogenesis, diagnosis and treatment of post-anaesthetic pulmonary oedema in horses. DATABASES USED: Pubmed 1970-present, personal files.  相似文献   
57.
<正>1锤片式粉碎机和超微粉碎机与超微粉碎机相比,锤片式粉碎机效率高、发热少且吸尘要求低。根据饲料配方和粉碎细度,装有普通硬合金锤片和圆孔筛的锤片式粉碎机的维护费用通常是0.02~0.1美元/t,电力成本约0.25~1美元/t。而超微粉碎机消耗2~4美元/t或更多,在许多情况下,零件磨损费超过0.25美元/t。  相似文献   
58.
59.
We conducted a five-year survey (2011–2015) of barley and wheat fields in Paraná state, Brazil, obtaining 754 Fusarium isolates from spikes with fusarium head blight (FHB)-symptoms. Multilocus genotyping and TEF-1α gene sequence analyses confirmed the dominance of the F. graminearum species complex (FGSC, 75.7%), but F. poae (11.5%), as well as F. avenaceum and related members of the F. tricinctum species complex (FTSC, 8.1%) appeared as substantial contributors to FHB. Within the FGSC, F. graminearum of the 15-ADON genotype was dominant (63%), followed by F. meridionale of the NIV genotype (23.1%), F. cortaderiae of the NIV (7%) or 3-ADON (2.6%) genotypes, and F. austroamericanum (3.8%) of the 3-ADON genotype. Substantial variation in pathogen composition was observed across years, with F. poae and F. meridionale frequencies significantly elevated in some years. Most F. poae strains produced DAS, diANIV, and butenolide, but not neosolaniol, T-2, or HT-2. All FTSC species produced moniliformin. Enniatin production was widespread among FTSC species, with the single F. acuminatum strain found to be the strongest producer of enniatins. Our findings confirm FGSC as a major contributor to FHB and expand considerably our knowledge of the presence, frequency, and conditions under which other pathogens may emerge, altering the spectrum of toxins that may accumulate in grain.  相似文献   
60.
Using extracts from suspension-cultured cells of soybean (Glycine max cv. Mandarin) as a source of active enzymes, the activities of glutathione transferases (GSTs) catalysing the conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) and selective herbicides were determined to be in the order CDNB≫ fomesafen>metolachlor=acifluorfen>chlorimuron-ethyl. GST activities showed a thiol dependence in a substrate-specific manner. Thus, GST activities toward acifluorfen and fomesafen were greater when homoglutathione (hGSH), the endogenously occurring thiol in soybean, was used as the co-substrate rather than glutathione (GSH). Compared with GSH, hGSH addition either reduced or had no effect on GST activities toward other substrates. In the absence of enzyme, the rates of hGSH conjugation with acifluorfen, chlorimuron-ethyl and fomesafen were negligible, suggesting that rapid hGSH conjugation in soybean must be catalysed by GSTs. GST activities were subsequently determined in 14-day-old plants of soybean and a number of annual grass and broadleaf weeds. GST activities of the plants were then related to observed sensitivities to post-emergence applications of the four herbicides. When enzyme activity was expressed on a mg-1 protein basis, all grass weeds and Abutilon theophrasticontained considerably higher GST activity toward CDNB than soybean. With fomesafen as the substrate, GST activities were determined to be in the order soybean≫Echinochloa crus-galli>Digitaria sanguinalis>Sorghum halepense=Setaria faberi with none of the broadleaf weeds showing any activity. This order related well to the observed selectivity of fomesafen, with the exception of A. theophrasti, which was partially tolerant to the herbicide. Using metolachlor as the substrate the order of the GST activities was soybean>A. theophrastiS. halepense>Amaranthus retroflexus>Ipomoea hederacea, with the remaining species showing no activity. GST activities toward metolachlor correlated well with the selectivity of the herbicide toward the broadleaf weeds but not toward the grass weeds. Acifluorfen and chlorimuron-ethyl were selectively active on these species, but GST activities toward these herbicides could not be detected in crude extracts from whole plants. © 1997 SCI  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