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   1580篇
  免费   100篇
  国内免费   2篇
林业   256篇
农学   51篇
基础科学   12篇
  368篇
综合类   113篇
农作物   39篇
水产渔业   80篇
畜牧兽医   653篇
园艺   18篇
植物保护   92篇
  2023年   9篇
  2022年   13篇
  2021年   33篇
  2020年   44篇
  2019年   37篇
  2018年   35篇
  2017年   42篇
  2016年   43篇
  2015年   33篇
  2014年   40篇
  2013年   104篇
  2012年   85篇
  2011年   70篇
  2010年   62篇
  2009年   63篇
  2008年   96篇
  2007年   77篇
  2006年   82篇
  2005年   62篇
  2004年   64篇
  2003年   65篇
  2002年   55篇
  2001年   31篇
  2000年   28篇
  1999年   16篇
  1998年   14篇
  1997年   9篇
  1995年   25篇
  1994年   15篇
  1993年   12篇
  1992年   9篇
  1991年   8篇
  1990年   15篇
  1989年   12篇
  1988年   8篇
  1986年   8篇
  1985年   7篇
  1984年   7篇
  1983年   9篇
  1982年   9篇
  1981年   8篇
  1974年   8篇
  1970年   8篇
  1968年   9篇
  1958年   7篇
  1957年   7篇
  1939年   7篇
  1938年   10篇
  1935年   6篇
  1931年   9篇
排序方式: 共有1682条查询结果,搜索用时 15 毫秒
41.
<正>近期伊利诺伊大学的J.A.Almeida博士、 Hans H.Stein博士以及Carsten Pedersen博士联手展开体重对于标准化回肠蛋白质和氨基酸吸收率的影响试验,结论证明,20 kg以下的仔猪回肠对于粗蛋白和氨基酸的吸收率比20~50 kg的育成猪和50~110 kg的育肥猪低。而且同一猪群的不同猪只也表现出吸收率的差异性。例如,在测定的300只仔猪中粗蛋白和氨基酸的吸收率  相似文献   
42.
Succinate dehydrogenase inhibitors (SDHIs) have played a crucial role in disease control to protect cereals as well as fruit and vegetables for more than a decade. Isoflucypram, the first representative of a newly installed subclass of SDHIs inside the Fungicide Resistance Action Committee (FRAC) family of complex II inhibitors, offers unparalleled long‐lasting efficacy against major foliar diseases in cereals. Herein we report the chemical optimization from early discovery towards isoflucypram and the first hypothesis of its altered binding mode in the ubiquinone binding site of succinate dehydrogenase. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   
43.
    
Ohne Zusammenfassung  相似文献   
44.
Six dogs were entered into a 30-day, prospective, nonrandomized, uncontrolled clinical trial evaluating the effects of an oral preparation of budesonide on the hypothalamic-pituitary-adrenal (HPA) axis during therapeutic management of active inflammatory bowel disease. Oral budesonide, at a dose of 3 mg/m(2), was administered once daily. Upon entry and completion of the trial, serum basal cortisol, adrenocorticotropic (ACTH)-stimulated cortisol, endogenous ACTH concentration, serum alkaline phosphatase (SAP) activity, and urine specific gravity were evaluated, as well as owner assessment of glucocorticoid-associated side effects. Significant suppression of the HPA axis occurred. No significant differences in SAP activity, urine specific gravity, or owner-subjective assessments were detected.  相似文献   
45.
Induced resistance to the apple scab fungus Venturia inaequalis was demonstrated in greenhouse tests with 12-day-old seedlings of the apple cultivar Golden Delicious treated with methyl 2,6-dichloro-isonicotinate or 3,5-dichlorosalicylic acid prior to inoculation with the causal fungus. Studies of the dose-response of flusilazole on induced resistant plants revealed synergistic effects between both crop protection principles. Therefore, the use of such resistance-inducing compounds in the field might allow a reduction in the number of fungicide applications, and possibly a reduction in dose, thus resulting in improved efficacy of fungicides. There was also evidence that induced resistance could prove to be a valid strategy for the treatment of pathogen populations with reduced sensitivity to a given fungicide. © 1998 SCI  相似文献   
46.
47.
OBITUARY     
  相似文献   
48.
49.
We investigated carbon (C) uptake and respiratory losses of an adult Pinus cembra tree at the alpine timberline throughout an entire year by means of an automated, multiplexing gas exchange system. These chamber measurements were then combined with biomass data for scaling up the C budget to the tree level. Integrated over an entire year, the cumulative C gain of the tree under study was 23.5 kg of C in 2002. The daily C balance was negative for 5 months and the estimated total wintertime respiratory losses were 9% of the amount of C fixed during the growing season. The total annual C loss of the tree consumed 55% of the annual net C gain and the remaining surplus was stored in new tissues (36%) and used for fine root growth (9%). Thus, the overall C budget of P. cembra at the upper timberline is balanced fairly well, although the C sink strength in fine roots is strongly limited owing to low root zone temperatures when compared to conifers at lower elevation sites.  相似文献   
50.
Hidden allergens are a common problem in food safety that has been known for many years. This is why the European Parliament adopted Directive 2003/89/EC amending 2000/13/EC. In addition to specific ingredients, Directive 2003/89/EC also requests the declaration of specific products that were used in the production and could be a risk for allergic individuals. This also includes the declaration of fining agents and lysozyme used in wines. In fact, it could be assumed that fining agents would be almost completely removed during the manufacturing process; however, until now there has been no necessity to analyze wine for these fining agents. By applying enzyme-linked immunosorbent assay (ELISA), residuals of fining agent proteins and the stabilizer lysozyme were investigated in various German wines. The results showed no detectable amounts of fining agents in wines, except for dried egg white and lysozyme, both derived from hen's egg white. For those products, adverse reactions against treated wines could not be excluded.  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