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   192篇
  免费   11篇
林业   13篇
农学   8篇
基础科学   1篇
  51篇
综合类   6篇
农作物   49篇
水产渔业   16篇
畜牧兽医   37篇
园艺   4篇
植物保护   18篇
  2023年   1篇
  2022年   7篇
  2021年   16篇
  2020年   15篇
  2019年   12篇
  2018年   18篇
  2017年   15篇
  2016年   15篇
  2015年   5篇
  2014年   15篇
  2013年   27篇
  2012年   6篇
  2011年   10篇
  2010年   7篇
  2009年   5篇
  2008年   13篇
  2007年   6篇
  2006年   1篇
  2005年   2篇
  2004年   2篇
  2002年   2篇
  1998年   1篇
  1997年   1篇
  1988年   1篇
排序方式: 共有203条查询结果,搜索用时 203 毫秒
1.
This study evaluated the supplementation effects of three herbal plants (thyme [THY], eucalyptus [EUC] and celery [CEL]), a commercial phytogenic additive ?containing essential oils (PFA‐EO, Digestarom® P.E.P.) and monensin (MON) in calf starter on performance, rumen fermentation and blood metabolites during pre‐ (days 3–55) and post‐weaning (days 56–70). Sixty‐six Holstein dairy calves (3 days of age, 41.2 ± 3 kg of BW) were allocated to one of six starters supplemented with: (i) no additives (CON), (ii) MON (30 mg/kg), (iii) THY (23 g/kg), (iv) CEL (23 g/kg), (v) EUC (23 g/kg) and (vi) PFA‐EO (3 g/kg). All the calves were offered starters ad libitum plus 6 L of whole milk daily. Starter intake tended to be the highest in calves fed PFA‐EO and THY; intermediate in calves fed CON, MON and EUC; and the lowest in those fed CEL. Average daily gain (ADG) and feed efficiency (FE) remained unaffected by dietary treatments during the pre‐weaning. During the post‐weaning period, ADG and FE ?were greatest in calves fed EUC followed by those fed CON, MON, PFA‐EO and THY, and then in those fed CEL. No differences were observed among the treatments in skeletal growth, faecal score, rumen pH or ammonia‐N concentration. Compared to calves fed CON and MON, those fed the herbal plants or PFA‐EO tended to recorded higher molar proportions of acetate and butyrate, and the acetate: propionate ratio. Blood malondialdehyde level did not differ among treatments, but calves on CON had the highest glucose concentration, and those fed PFA‐EO recorded the highest value for β‐hydroxyl butyrate on day 70. In conclusion, the results indicate that the three herbs and PFA‐EO are capable of modulating some of the rumen fermentation parameters and blood metabolites as well as eucalyptus could potentially be a better alternative to monensin for improving post‐weaning performance.  相似文献   
2.
3.
Trunk disease is a major problem on grapevine in Zanjan province, causing serious decline, despite which its aetiology remains unknown. The purpose of this study was to investigate factors involved in grapevine decline in vineyards of Zanjan province. Samples were collected from twigs and branches of grapevines in the region between October and November 2018. Fungal isolates were identified based on morphological characteristics and ITS-rDNA sequence data for selected isolates. The frequency and diversity of the fungal community recovered from grapevines in Darreh Sejin in Zanjan province were higher than in other regions. A total of 112 fungal isolates comprising 22 species were recovered. Phaeoacremonium minimum, Microsphaeropsis olivacea and Kalmusia variispora were identified as the dominant species in the region examined and could be considered the main trunk pathogens of grapevines in Zanjan region. In inoculation tests, M. olivacea was proved to be pathogenic on grapevine for the first time in this study.  相似文献   
4.
Recently, the nanotechnology industry has seen a growing interest in integrating silver nanoparticles(AgNPs) into agricultural products, which increases soil exposure to these particles. This demands an investigation into the effect of AgNPs on soil health. Changes in soil enzyme activities upon exposure to AgNPs can serve as early indicators of any adverse effects that these particles may have on soil quality. This study aimed to determine the effects of AgNP size, concentration, coating, and e...  相似文献   
5.
Journal of Soils and Sediments - Carbon capture and storage (CCS) has been frequently discussed as a strategy for meeting CO2 emission reduction and its targets. However, some critical issues have...  相似文献   
6.
7.
This study investigates the effects of feeding diet based on untreated (UT) or ensiled alkali‐treated (ET) barley straw with either urea or casein supplementation, on feed intake, digestibility, ruminal pH, water intake and faecal and urinary characteristics. Four sheep fitted with ruminal cannulas were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Barley straw was treated by the dry (spraying) method in pH adjusted of hydrogen peroxide (pH 11.5), ensiled for 6 weeks and included at 65% of the diet dry matter (DM). The results showed that straw pH reduced from 11.58 to 8.60 after 6 weeks of ensilage. The ET diet increased average DM digestibility and intake by 19% and 43% respectively. Total water intake was similar across treatments, while the water/DM intake ratio was 23% higher with the UT diet than with the ET one. Ruminal (6.73 vs. 6.84) and faecal (8.67 vs. 9.05) pH decreased but urinary pH (6.14 vs. 8.13) increased as a result of feeding animals on the ET diet compared with the UT diet. Compared with the UT diet, the ET one decreased faecal fibre (12%), moisture (32%) and water holding capacity, while it increased faecal ash (10%) and density (20%). The volume of urine excreted by the sheep fed with the ET diet increased by 67%, but their urine specific gravity (SG) decreased. No significant effects were observed for the dietary N supplementation and interactions between straw type × N supplementation with regard to any of the measured characteristics except for DM intake, which reduced due to the casein supplementation in the ET diet. These results indicate that the alkali treatment and ensilage of barley straw increased digestibility, intake, faecal consistency and urinary pH and dilution but decreased straw alkalinity as well as ruminal and faecal pH.  相似文献   
8.
The present study was carried out to characterize ACE inhibitory peptides which are released from the trypsin hydrolysate of wheat gluten protein. In silico proteolitic digestion of a high molecular weight glutenin subunit was performed. Among the resultant fragments, four peptides were selected for chemical synthesis based on the chemoinformatics studies and docking properties. The ACE inhibitory activity and kinetic parameters of the most important peptides were determined. Molecular docking simulation was also performed to predict the sites on ACE in which these peptides bind and displayed inhibition mechanisms. Two peptide sequences of IPALLKR (P4) and AQQLAAQLPAMCR (P6) showed higher ACE inhibitory activity among peptide collection. The IC50 values of P6 and P4 were 43 ± 1.3 μM and 68 ± 2.8 μM, respectively. P6 peptide was proved to be a more potent ACE inhibitor than P4 peptide. Lineweaver-Burk plots revealed that P6 and P4 behaved as non-competitive and competitive ACE inhibitors, respectively. The simulations showed that P4 bound to the active site region. Conversely, P6 bound to the N-terminus entrance of substrate tunnel and obstructed the substrate access into the catalytic site. Overall, the results showed that these peptides would be considered as a model for discovering new bio-compatible ACE inhibitors.  相似文献   
9.
Genetic Resources and Crop Evolution - The pomegranate (Punica granatum L.) is an ancient fruit plant which has been consumed for its nutritional value and medicinal properties by mankind. Several...  相似文献   
10.
In this approach, a derivatization method is described for monitoring of organic acids in fermentation media without any separation step. The aqueous phase of fermentation media was evaporated and heated in a silylation reagent to form trimethylsilyl (TMS) derivatives. The silylated compounds are analyzed by 29Si nuclear magnetic resonance (29Si NMR) and gas chromatography-mass spectrometry (GC-MS). 29Si NMR can qualitatively monitor the components produced in the Krebs cycle. Quantification of these compounds is investigated by using selected ion monitoring mode of mass spectrometry. In this mode, mass to charge (m/z) values of their [M - 15]+ ions, which are 465, 275, 247, 221, 335, 251, and 313 of TMS derivatives of citric, alpha-ketoglutaric, succinic, fumaric, l-malic, oxaloacetic, and palmitic (as an internal standard), acids, respectively, are used. The limit of detection and the linear working range for derivatized citric acid were found to be 0.1 mg L(-1) and 10-3 x 10(4) mg L(-1). The relative standard deviation of the method for five replicates was 2.1%. The average recovery efficiency for citric acid added to culture media was approximately 97.2%. Quantitative results of GC-MS are compared with those obtained by an ultraviolet-visible method.  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