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   187篇
  免费   13篇
林业   8篇
农学   8篇
  26篇
综合类   3篇
农作物   9篇
水产渔业   22篇
畜牧兽医   106篇
园艺   6篇
植物保护   12篇
  2023年   5篇
  2022年   13篇
  2021年   25篇
  2020年   20篇
  2019年   27篇
  2018年   7篇
  2017年   10篇
  2016年   12篇
  2015年   13篇
  2014年   9篇
  2013年   12篇
  2012年   11篇
  2011年   9篇
  2010年   2篇
  2009年   2篇
  2008年   8篇
  2007年   7篇
  2006年   5篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
排序方式: 共有200条查询结果,搜索用时 15 毫秒
191.
192.
Precision Agriculture - Changes in land use in riverside ecosystems added to the flood and ebb regimes of rivers modify the spatial variability of the physical–mechanical attributes of soil,...  相似文献   
193.
Measuring ammonia(NH3)volatilization from urea-fertilized soils is crucial for evaluation of practices that reduce gaseous nitrogen(N)losses in agriculture.The small area of chambers used for NH3volatilization measurements compared with the size of field plots may cause significant errors if inadequate sampling strategies are adopted.Our aims were:i)to investigate the effect of using multiple open chambers on the variability in the measurement of NH3volatilization in urea-amended field plots and ii)to define the critical period of NH3-N losses during which the concentration of sampling effort is capable of reducing uncertainty.The use of only one chamber covering 0.015%of the plot(51.84 m2)generates a value of NH3-N loss within an expected margin of error of 30%around the true mean.To reduce the error margin by half(15%),3–7 chambers were required with a mean of 5 chambers per plot.Concentrating the sampling efforts in the first two weeks after urea application,which is usually the most critical period of N losses and associated errors,represents an efficient strategy to lessen uncertainty in the measurements of NH3volatilization.This strategy enhances the power of detection of NH3-N loss abatement in field experiments using chambers.  相似文献   
194.
Although stem cell therapy is a promising alternative for treatment of degenerative diseases, there are just few reports on the use of stem cells therapy in horse's reproductive system. This study aims to evaluate the effect of intratesticular injection of bone marrow mesenchymal stromal/stem cells (MSCs) in healthy stallions, and its outcome on seminal parameters and fertility. In Experiment 1, 24 stallions were divided into treatment group (TG) and control group (CG). In the TG, an intratesticular application of MSC was performed, and in the CG, only PBS was used. Measurements of testicular volume, surface temperature and Doppler ultrasonography were performed 24 and 48 hr after treatments. Fifteen days after application, the testicles were removed and submitted to histological analysis. In Experiment 2, 3 fertile stallions received similarly treatment with MSCs. Physical examination and sperm analysis were performed weekly during 60 days after treatment, and at the end, semen from one of them was used for artificial inseminations of 6 healthy mares. In Experiment 1, clinical examinations showed no signals of acute inflammation on both groups according to the analysed variables (p > .05). Also, no signal of chronic inflammation was observed on histological evaluation. In Experiment 2, stallions presented no physical alterations or changes in sperm parameters, and a satisfactory fertility rate (83%; 5/6) was observed after AI. The results support the hypothesis that intratesticular application of bone marrow MSCs is a safe procedure, and this could be a promising alternative to treat testicular degenerative conditions.  相似文献   
195.
196.
Somatic cell counts (SCCs) levels indicate the occurrence of infections in goat udders and are related to the productivity of goat milk, cheese and yoghurt. This work presents a segmentation method for counting somatic cells in goat milk images, intending to detect an infection known as mastiffs, which is the major cause of loss in dairy farming. The image segmentation procedure is devised by using the lab color space and the watershed transform. A large number of samples under variable preparation conditions are treated with the proposed method. A comparison between manual and the proposed technique is presented. Promising results indicates that video-microscopy systems may be employed to develop automated SCC for goat milk.  相似文献   
197.
Ascidians of the genus Aplidium are recognized as an important source of chemical diversity and bioactive natural products. Among the compounds produced by this genus are non-nitrogenous metabolites, mainly prenylated quinones and hydroquinones. This review discusses the isolation, structural elucidation, and biological activities of quinones, hydroquinones, rossinones, longithorones, longithorols, floresolides, scabellones, conicaquinones, aplidinones, thiaplidiaquinones, and conithiaquinones. A compilation of the 13C-NMR spectral data of these compounds is also presented.  相似文献   
198.
199.
An elutriation technique was developed to obtain large quantities of pure canine monocytes. Firstly, peripheral blood mononuclear cells (PBMC) were isolated from whole blood by Ficoll gradient. Then, the PBMC were separated by an elutriation procedure. We demonstrated that these techniques allow the isolation of canine peripheral blood monocytes with a purity of 64% +/- 7.9 when labelled with anti-CD14 antibody. This purity increased to 83% +/- 2.2 after separation by magnetic anti-CD14 microbeads. The cell viability was more than 95% and apoptotic cells were less than 10%. The monocytes purified by these methods were functionally active in a mixed leukocyte reaction (MLR). A lymphocyte fraction was obtained directly only by elutriation with an average of 79.9% +/- 10.7 of CD5+, 7.9% +/- 3.5 of CD21+ and 1.78% +/- 2.53 of CD14+. Our results indicate that this elutriation procedure is a safe method to purify monocytes as well as lymphocytes, useful in MLR.  相似文献   
200.
A marine-derived strain of Clonostachys rosea isolated from sediments of the river Loire estuary (France) was investigated for its high lipid production. The fungal strain was grown on six different culture media to explore lipid production changes. An original branched conjugated fatty acid, mainly present in triglycerides and mostly produced when grown on DCA (23% of total fatty acid composition). It was identified as 4-Me-6E,8E-hexadecadienoic on the basis of spectroscopic analyses. This fatty acid reduced viability of MCF-7 breast cancer cells in a dose dependent manner (up to 63%) at physiological free fatty acid human plasma concentration (100 μM). Reduction of gene expression of two lipogenic enzymes, the acetyl CoA carboxylase (ACC) and the fatty acid synthase (FAS) was evaluated to explore the mechanisms of action of 4-Me-6E,8E-16:2 acid. At 50 μM, 50% and 35% of mRNA gene expression inhibition were observed for ACC and FAS, respectively.  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