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   870篇
  免费   51篇
林业   81篇
农学   38篇
基础科学   3篇
  242篇
综合类   53篇
农作物   102篇
水产渔业   76篇
畜牧兽医   221篇
园艺   18篇
植物保护   87篇
  2023年   13篇
  2022年   33篇
  2021年   47篇
  2020年   48篇
  2019年   30篇
  2018年   31篇
  2017年   32篇
  2016年   41篇
  2015年   35篇
  2014年   36篇
  2013年   44篇
  2012年   62篇
  2011年   73篇
  2010年   46篇
  2009年   40篇
  2008年   46篇
  2007年   63篇
  2006年   37篇
  2005年   38篇
  2004年   26篇
  2003年   32篇
  2002年   22篇
  2001年   4篇
  2000年   5篇
  1999年   10篇
  1998年   7篇
  1997年   5篇
  1996年   1篇
  1993年   2篇
  1992年   3篇
  1991年   3篇
  1989年   2篇
  1986年   1篇
  1980年   2篇
  1979年   1篇
排序方式: 共有921条查询结果,搜索用时 0 毫秒
171.
The slash-and-burn system is a subsistence agronomical practice widespread in tropical areas worldwide. This system has been extensively studied,especially for its impacts on agronomical aspects and soil physicochemical properties; however, knowledge of soil microbial diversity under slash and bum is scarce. In this study, for the first time, soil bacterial diversity of three locations from Central Mozambique, where slash and burn has been practiced for different durations of the forest fallow p...  相似文献   
172.
A severe physiological disorder of ‘Clementine’ mandarins in the Assini area of Argolis, Southestern Greece, was investigated for two successive years. Irregular-shaped necrotic spots were observed on the rinds of mandarins, mainly at the fruit stylar-ends, from the color break till harvest time. In order to investigate the possible correlation between the disorder and the inorganic nutrition of the fruit, spotted and symptomless mandarin rinds, in four commercial orchards were chemically analyzed. The relationship between fruit inorganic nutrition and the disorder symptoms were not consistent. Using Electron Scanning Microscopy, invisible cracks were observed at the cuticle and the external strata of the spotted rind whereas oil glands remained intact. Considering the results of chemical analyses, microscopic observations, as well as, the information given by the growers, this physiological disorder should be attributed to sudden changes of climatic conditions and not to nutritional imbalance.  相似文献   
173.
Journal of Plant Diseases and Protection - A survey of Rhizoctonia solani isolates from potato tubers and stems grown in European and Far Eastern regions of Russia in 2012–2020 was conducted....  相似文献   
174.
European Journal of Plant Pathology - Sorghum anthracnose caused by the fungal pathogen Colletotrichum sublineolum, is one of the most economically important diseases of sorghum globally and in...  相似文献   
175.
Journal of Plant Diseases and Protection - Bacterial spot caused by Xanthomonas euvesicatoria pv. euvesicatoria (Xanteu) is one of the major causes of yield losses in tomato (Lycopersicon...  相似文献   
176.
Plant Foods for Human Nutrition - γ-linolenic acid (GLA, 18:3n-6) is a bioactive fatty acid (FA) that exerts several healthy actions; however, its occurrence is restricted to a few oils. The...  相似文献   
177.
Corn tortillas have a short shelf life due to increased firmness and microbial spoilage. Commercial corn tortillas use carboxymethyl cellulose (CMC) to delay staling; however this gum is expensive when compared to the rest of the tortilla ingredients. Glycerol has been added to bread and wheat tortillas to increase pliability and salt has been shown to mask the flavor of glycerol in corn tortillas. The possibility to reduce staling in corn tortillas by adding glycerol/salt as an alternative to CMC was investigated by monitoring changes in physico-chemical properties during 2 weeks of storage at 25 °C. Molecular and macroscopic changes were followed using thermal and mechanical analysis. During storage an increase in amylopectin recrystallization was observed in all samples. The “freezable” water content of all tortillas decreased over the first 3–5 days of storage with an increase after 7 days, while moisture content and water activity remained constant. Glycerol/salt tortillas exhibited a sharper transition region in the DMA temperature scan suggesting a more homogenous sample. CMC tortillas were significantly stiffer than glycerol tortillas after 14 days of storage. Glycerol/salt combinations may offer at least a partial replacement for CMC since it helped control the stiffness, water homogeneity and distribution during storage.  相似文献   
178.
179.
Under future climate change, modification of temperature and salinity are expected to result in distribution shifts of marine organisms, including commercial fish and shellfish. Changes are anticipated everywhere, including in the seas of many important fishing nations. Species turnover will in turn result in both opportunities and threats to fishing industries. To determine the impacts for northwest European shelf fisheries, we project changes for 49 commercially important fish and shellfish species using an ensemble of five ecological niche models and three different downscaled climate change projections. The habitat suitability and latitudinal shifts projected from the recent past (1997–2016) to two futures (2030–2050; 2050–2070) were calculated for waters around the United Kingdom. Of the species examined, around half were projected to have consistently more suitable habitat in the future, including European seabass (Dicentrarchus labrax, Moronidae), sardine (Sardina pilchardus, Alosidae) and anchovy (Engraulis encrasicolus, Engraulidae). Conversely, it is suggested that UK waters will become less suitable for species including Atlantic cod (Gadus morhua, Gadidae) and saithe (Pollachius virens, Gadidae). Our comprehensive approach using a number of models and climate change scenarios shows that while there are differences in the magnitude of change between models, and while some models perform better for certain species compared with others, overall, the general trends in habitat suitability and abundance are robust across models and climate scenarios. This emphasises the value in using more than one modelling technique with different climate scenarios (i.e., an ensemble approach) to capture the uncertainty or agreement around climate change projections.  相似文献   
180.
Bioactive plants from Argentina and Bolivia   总被引:4,自引:0,他引:4  
Antibacterial and molluscicidal activities of methanol and chloroform extracts of 16 plant species belonging to the families Compositae and Melastomataceae were evaluated. The chloroform extract of Vernonanthura tweediana and the methanol extract of Senecio santelisis resulted to be very toxic to brine shrimp nauplii (LC(50)=1 microg/ml). Chloroform extracts of S. santelisis and Senecio leucostachys as well as the methanol extract of Wedelia subvaginata displayed molluscicidal effects on Biomphalaria peregrina showing LC(100)<100 microg/ml. Moderate antibacterial action was produced by the chloroform extracts of Flaveria bidentis, Grindelia scorzonerifolia and Vernonia incana against two strains of Staphylococcus aureus.  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