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   117篇
  免费   1篇
林业   12篇
农学   7篇
基础科学   1篇
  21篇
综合类   15篇
农作物   4篇
水产渔业   11篇
畜牧兽医   26篇
园艺   7篇
植物保护   14篇
  2023年   1篇
  2022年   7篇
  2021年   4篇
  2020年   7篇
  2019年   9篇
  2018年   2篇
  2017年   4篇
  2016年   5篇
  2015年   1篇
  2014年   10篇
  2013年   6篇
  2012年   7篇
  2011年   13篇
  2010年   4篇
  2009年   3篇
  2008年   6篇
  2007年   4篇
  2006年   3篇
  2005年   8篇
  2004年   6篇
  2003年   1篇
  2002年   3篇
  2000年   1篇
  1996年   1篇
  1990年   1篇
  1970年   1篇
排序方式: 共有118条查询结果,搜索用时 15 毫秒
1.
The carotenogenic thraustochytrid Thraustochytrium sp. RT2316-16 was grown in batch and repeated-batch cultures using different feeds containing glucose, or glycerol, and yeast extract, for the production of lipids, phospholipids and carotenoids. RT2316-16 produced canthaxanthin, astaxanthin and β-carotene. The effects of biotin, ascorbic acid, light and temperature were evaluated in some of the experiments. In 2-day-old batch cultures, the combined mass percentage of eicosapentaenoic acid and docosahexaenoic acid in total lipids was between 16.5% (glycerol-based medium in the dark; biomass concentration = 4.2 ± 1.1 g L−1) and 42.6% (glucose-based medium under light; biomass concentration = 3.3 ± 0.1 g L−1), decreasing to 3.8% and 6.1%, respectively, after day 4. In repeated-batch cultures, the total lipids in the biomass increased after glucose or glycerol was fed alone, whereas the total carotenoids (168 ± 7 μg g−1 dry weight (DW)) and phospholipids in the biomass increased after feeding with yeast extract. The biomass with the highest content of phospholipids (28.7 ± 4.3 mg g−1 DW) was obtained using a feed medium formulated with glycerol, yeast extract and ascorbic acid. Glycerol was the best carbon source for the production of a biomass enriched with total lipids (467 ± 45 mg g−1 DW). The composition of carotenoids depended strongly on the composition of the feed. Repeated-batch cultures fed with yeast extract contained canthaxanthin as the main carotenoid, whereas in the cultures fed only with glucose, the biomass contained mainly β-carotene.  相似文献   
2.
3.
4.
Journal of Pest Science - Semiochemicals such as herbivore-induced plant volatiles (HIPVs) and host chemicals serve as communication signals for parasitoids searching for oviposition sites. The...  相似文献   
5.
African trypanosomosis is a potentially fatal disease that is caused by extracellular parasitic protists known as African trypanosomes. These parasites inhabit the blood stream of their mammalian hosts and produce a number of pathological features, amongst which is anemia. Etiology of the anemia has been partly attributed to an autoimmunity-like mediated erythrophagocytosis of de-sialylated red blood cells (dsRBCs) by macrophages. Lactose infusion to infected animals has proven effective at delaying progression of the anemia. However, the mechanism of this anemia prevention is yet to be well characterized. Here, the hypothesis of a likely induced further modification of the dsRBCs was investigated. RBC membrane galactose (RBC m-GAL) and packed cell volume (PCV) were measured during the course of experimental trypanosomosis in mice infected with Trypanosoma congolense (stb 212). Intriguingly, while the membrane galactose on the RBCs of infected and lactose-treated mice (group D) decreased as a function of parasitemia, that of the lactose-untreated infected group (group C) remained relatively constant, as was recorded for the uninfected lactose-treated control (group B) animals. At the peak of infection, the respective cumulative percent decrease in PCV and membrane galactose were 30 and 185 for group D, and 84 and 13 for group C. From this observed inverse relationship between RBCs membrane galactose and PCV, it is logical to rationalize that the delay of anemia progression during trypanosomosis produced by lactose might have resulted from an induction of galactose depletion from dsRBCs, thereby preventing their recognition by the macrophages.  相似文献   
6.
There is no report of diversity, biological properties and bioactive compounds of sponge-associated fungi from Indonesia’s mangrove ecosystem to date. This study was designed to isolate sponge-associated fungi from a mangrove ecosystem in Mangkang, to screen the antimicrobial and extracellular enzyme properties of the isolates, characterize the biologically promising isolates using molecular approaches, and profile the secondary metabolites using phytochemical and thin-layer chromatography (TLC) analyses. An unidentified sponge that lived in association with mangrove roots was collected from Mangkang. Total of eight associated fungi were isolated from the sponge. Among all isolates, only two fungi SPMKF 1 and SPMKF 6 produced extracellular amylase, another two fungi SPMKF 4 and 5 showed antibacterial activity against MRSA, and only one fungus SPMKF 8 was able to produce extracellular amylase and show antimicrobial activity against ESBL E. coli, Salmonella enterica ser. Typhi strain MDR and C. albicans, while SPMKF 2, SPMKF 3 and SPMKF 9 did not show any biological properties. The result of genetic characterization proved that SPMKF 1 was Cladosporium tenuissimum, SPMKF 4 was Eutypella sp., SPMKF 5 was Lasiodiplodia theobromae, SPMKF 6 was Fusarium keratoplasticum and SPMKF 8 was F. solani. Furthermore, an amylase gene was detected in fungi SPMKF 1, 6 and 8 while among the BGC, only NRPS genes were detected in SPMKF 4, 5 and 8. Interestingly, several same metabolites indicating the same retention factor (Rf) values in TLC were detected in the fungal crude extracts by TLC.  相似文献   
7.
利用研究区棉花种植面积和产量相关统计数据,探究研究区棉花种植面积和产量的时空变化特征及单产和面积作用对棉花产量的影响。研究结果表明:(1) 近62年来,研究区的棉花种植面积、棉花产量和单产均呈上升趋势,而且表现出明显的阶段性和波动性,1949—1985年间增长缓慢,1986—2011年增长迅速。(2) 就棉花总产波动来看, 单产的作用占42.04%,面积作用占50.96%,在1949—1985年间单产增加对棉花总产量提高的贡献较大,在1986—2011年间棉花种植面积扩大对棉花总产量提高的贡献较大。(3) 1985年前棉花种植面积较稳定,波动不大,主要靠挤占粮食作物面积来扩大,1986年之后棉花种植面积扩大迅速,主要途径为开荒造地。(4) 棉花市场价格的波动、生产成本的上升、产量的徘徊、生产环境的恶化和品种等直接影响着研究区棉花生产的竞争力和棉农增收。  相似文献   
8.
利用研究区棉花种植面积和产量相关统计数据,探究研究区棉花种植面积和产量的时空变化特征及单产和面积作用对棉花产量的影响。研究结果表明:(1) 近62年来,研究区的棉花种植面积、棉花产量和单产均呈上升趋势,而且表现出明显的阶段性和波动性,1949—1985年间增长缓慢,1986—2011年增长迅速。(2) 就棉花总产波动来看, 单产的作用占42.04%,面积作用占50.96%,在1949—1985年间单产增加对棉花总产量提高的贡献较大,在1986—2011年间棉花种植面积扩大对棉花总产量提高的贡献较大。(3) 1985年前棉花种植面积较稳定,波动不大,主要靠挤占粮食作物面积来扩大,1986年之后棉花种植面积扩大迅速,主要途径为开荒造地。(4) 棉花市场价格的波动、生产成本的上升、产量的徘徊、生产环境的恶化和品种等直接影响着研究区棉花生产的竞争力和棉农增收。  相似文献   
9.
In this study, the interaction between crop load and irrigation level on yield, fruit size, skin color and stem-end splitting fruit ratio in the apple cultivar ‘Gala, Galaxy’ grafted on rootstock M9 were investigated. Six irrigation programs were applied during the whole growth season: deficit irrigation (rates of 0.25 kc, 0.50 kc, 0.75 kc), full irrigation (rate of 1.00 kc), excess irrigation (rate of 1.25 kc) and non-irrigation (rates of 0.00 kc of “Class A” pan evaporation coefficient). Four crop loads in each irrigation application were performed by hand thinning after the June drop as a- a low crop load (3 fruits cm?2 TCA), b- a medium crop load (5 fruits cm?2 TCA), c- a heavy crop load (7 fruits cm?2 TCA), and d- an un-thinned crop load (>?7 fruits cm?2 TCA). The total tree yield increased with crop load and irrigation levels. Fruit size was significantly increased by the low crop load. Irrigation increased the fruit size compared to non-irrigation treatment. Further 0.75 kc, 1.00 kc and 1.25 kc irrigation treatments significantly increased the fruit length. Irrigation reduced the fruit flesh firmness. While the low crop load increased the skin red color, it decreased the fruit skin brightness. The yellowness of skin decreased with increasing in the irrigation amount. Irrigation reduced the skin brightness and yellowness, but it increased red color. Crop load and irrigation significantly affected the stem-end splitting fruit ratio. While the splitting fruit ratio increased with a decrease in the crop load, it decreased with an increase in irrigation amount, relatively. Consequently, the low and medium crop load treatments would be beneficial to increase the ratio of marketable fruits without any significant losses in yield for ‘Gala’ apple, especially under 0.75 kc deficit irrigation treatment.  相似文献   
10.
The overall sex ratio of offspring (dead embryos and hatch chicks) from all the fertilized eggs of 140 hens collected for 30 days was studied using duplex PCR of certain fragments of sex chromosomes. Additional 894 dead embryos over a period of 21 days of incubation were also investigated to verify the sex ratio of the dead embryos. The sex of the early dead embryos was identified using this molecular sexing technique. The sex ratio of the hatch chicks and the total offspring of the hens investigated in this experiment did not differ from the expected sex ratio (i.e., 1:1)., However, the number of female dead embryos was significantly more than that of males. The data indicated that the different physiologic function of males and females contributed to female-biased mortality during incubation. It was also found by further analysis that the sex ratios of the offspring of some hens were significantly biased to female or male over the period investigated, which suggested that the sex ratio of offspring might be influenced by the maternal condition to some degrees.  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