全文获取类型
收费全文 | 339篇 |
免费 | 17篇 |
专业分类
林业 | 32篇 |
农学 | 27篇 |
基础科学 | 5篇 |
99篇 | |
综合类 | 19篇 |
农作物 | 50篇 |
水产渔业 | 40篇 |
畜牧兽医 | 50篇 |
园艺 | 6篇 |
植物保护 | 28篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 39篇 |
2012年 | 23篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 25篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 78 毫秒
221.
Dewachi O Joubert P Hamid Q Lavoie JP 《Veterinary immunology and immunopathology》2006,109(1-2):31-36
Heaves, a condition associated with airway neutrophilia, is believed to result from an allergic response to environmental dust particles. However, the contribution of neutrophils to the allergic response is poorly understood. It has been hypothesized that Th2-type cytokines can directly activate neutrophils to produce pro-inflammatory mediators. The present study focused on the presence of receptors for the Th2-type cytokines interleukin (IL)-5 and IL-9 on peripheral blood neutrophils of horses with heaves. Neutrophils were isolated from peripheral blood of horses with heaves (n=7), and normal control (n=5) before (pasture) and 3 weeks following a continuous natural allergen challenge (stabling). Horses with heaves had significantly increased numbers of neutrophils expressing IL-5 and IL-9 receptors compared to control while in pasture, and further increased during stabling in heaves affected horses but not in control animals. These results provide a possible mechanism by which Th2-type cytokines may activate neutrophils in equine heaves. 相似文献
222.
Hamid Khazaei Shahram-D. Mohammady Maria Zaharieva Philippe Monneveux 《Genetic Resources and Crop Evolution》2009,56(1):105-114
Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C3 crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency
for grain and biomass production (WUEG and WUEB, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher
in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as
within bread wheat. It was also positively correlated to stomatal frequency. The highest WUEG and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUEB and biomass than durum wheat. WUEG and WUEB were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUEG was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity
of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUEG. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships
between WUEG and its different components (water consumed, transpiration efficiency and carbon partitioning). 相似文献
223.
Goli M Ezzatpanah H Ghavami M Chamani M Aminafshar M Toghiani M Eghbalsaied S 《Tropical animal health and production》2012,44(7):1673-1680
The major pathogens causing mastitis were evaluated by multiplex-polymerase chain reaction (M-PCR) with self-designed primers in four quarters of the first, third, and fifth parities in industrial, semi-industrial, and traditional dairy cattle farms in Iran. With the incidence of infection in the quarters by Staphylococcus aureus and Streptococcus agalactiae, the mean log somatic cell count (log SCC) increased from 5.06 to 5.77. The smallest changes occurred with Escherichia coli. Contagious pathogens, when compared with environmental pathogens, were more prevalent and common and created more profound quantitative and qualitative changes in SCC profiles. The second part of the study surveyed the diversity of contaminating pathogens and their effect on quantitative and qualitative profiles of somatic cells. M-PCR was used to determine the absence (M-PCR(-)) and presence of one (M-PCR(+1)), two (M-PCR(+2)), and three (M-PCR(+3)) major pathogens in raw milk samples. Quarter log SCC increased from 5.06 (for M-PCR(-1)) to 5.5 (for M-PCR(+1)), 5.7 (for M-PCR(+2)), and 6 (for M-PCR(+3)). Percent changes in polymorphonuclears (PMNs) were not significant between different quarters and parities but were significant between different farms in terms of pathogen diversity (P?0.05). Therefore, by increasing the number of types of major pathogens involved in subclinical mastitis, SCC of udder quarters and the proportion of PMNs significantly increased, whereas the proportion of lymphocytes significantly decreased. This subject is very important in increasing the shelf life of dairy products, because PMNs are introduced to the enzymatic pools. 相似文献
224.
Hamid Reza Taghiyari 《Wood Science and Technology》2012,46(5):939-952
Fire-retarding properties of 200?ppm nano-silver solution, with a size ranging from 20 to 80?nm, on five woody species were studied and compared with Borax and Celcune ? . Blocks of 150?×?130?×?9?mm3 were prepared and divided into four groups of control samples, nano-silver-, Borax-, and Celcune-impregnated specimens. A special apparatus was designed, and six fire-retarding properties of each specimen were measured, namely ignition, glowing, back-darkening and back-holing times, as well as length and width of burning. Results showed that all three kinds of treatments had improving effects on the fire-retarding properties. Celcune showed the best improvement on glowing time. Cluster analysis showed direct relation between density and fire-retardant properties; also, fire-retarding behaviors of the four hardwoods were quite different to those of the one softwood. Furthermore, there are improvements in some fire-retarding properties of nano-silver-impregnated specimens that are in connection with its heat-transfer property. 相似文献
225.
The Effects of Brackish Water on Growth Hormone/Insulin‐like Growth Factor‐1 Gene Expression of the Caspian Trout,Salmo trutta caspius (Kessler, 1877), During the Early Stage of Smoltification
下载免费PDF全文
![点击此处可从《Journal of the World Aquaculture Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
226.
227.
The rose plants were cultivated in the pots containing 75% cocopeat+ 25% perlite and were nourished with ½ Hoagland nutrient solutions with pH of 4.5, 5.5, 6.5, and 8. The results revealed that plant fresh and dry weight, flower bud, and stem diameter increased with the increase in pH from 4.5 to 6.5, but then started to decrease with further increase in pH up to 8. The highest number of buds, chlorophyll content, Fv/Fm, performance index (PI), and leaf phosphorus, iron, manganese, and copper concentrations were obtained at pH 6.5 and the lowest one at pH 8. The highest and lowest zinc concentration was observed at pH 6.5 and 4.5, respectively. According to the results, pH 6.5 was evaluated as optimum for hydroponic culture of rose, which resulted in the higher uptake of elements and better vegetative and reproductive growth and higher quality of rose plants. 相似文献
228.
Hamid R. Roosta 《Journal of plant nutrition》2014,37(10):1676-1689
Strawberry (Fragaria ananasa) plants were grown in hydroponics in a greenhouse, where the supply of different ammonium (NH4+): nitrate (NO3?) ratios, was investigated to reduce the negative effect of alkalinity in nutrient solutions. The experiment was arranged in factorial combination with two factors, NH4+:NO3? ratios (0%:100%, 25%:75%, 50%:50%, 75%:25%, and 100%:0%) and bicarbonate (0, 25, 50, and 75 mM; NaHCO3). Plants treated with increasing bicarbonate concentrations exhibited significantly inhibited growth. In plants treated with NH4+ and NO3? simultaneously, there was a counteraction of the bicarbonate-induced growth suppression. Sole NO3? application in the presence of high bicarbonate resulted in poor growth and plant death due to high alkalinity. The adverse effect of alkalinity on SPAD values and maximal quantum yield of PSII photochemistry (Fv/Fm) alleviated with increasing proportion of NH4+ in nutrient solutions. The results showed that fruit numbers and yield of strawberry increased with elevation of NH4+ in nutrient solutions. 相似文献
229.
Dwyer JR Uman MA Rassoul HK Al-Dayeh M Caraway L Jerauld J Rakov VA Jordan DM Rambo KJ Corbin V Wright B 《Science (New York, N.Y.)》2003,299(5607):694-697
Using a NaI(Tl) scintillation detector designed to operate in electrically noisy environments, we observed intense bursts of energetic radiation (> 10 kiloelectron volts) during the dart leader phase of rocket-triggered lightning, just before and possibly at the very start of 31 out of the 37 return strokes measured. The bursts had typical durations of less than 100 microseconds and deposited many tens of megaelectron volts into the detector. These results provide strong evidence that the production of runaway electrons is an important process during lightning. 相似文献
230.
Hulme M Mahony M Beck S Görg C Hansjürgens B Hauck J Nesshöver C Paulsch A Vandewalle M Wittmer H Böschen S Bridgewater P Diaw MC Fabre P Figueroa A Heong KL Korn H Leemans R Lövbrand E Hamid MN Monfreda C Pielke R Settele J Winter M Vadrot AB van den Hove S van der Sluijs JP 《Science (New York, N.Y.)》2011,333(6043):697-698