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   66篇
  免费   4篇
林业   3篇
农学   7篇
基础科学   3篇
  23篇
农作物   9篇
水产渔业   11篇
畜牧兽医   8篇
园艺   1篇
植物保护   5篇
  2023年   1篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   5篇
  2016年   4篇
  2015年   1篇
  2014年   2篇
  2013年   8篇
  2012年   1篇
  2011年   3篇
  2010年   4篇
  2009年   3篇
  2008年   2篇
  2007年   2篇
  2006年   1篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
  2002年   5篇
  2000年   3篇
  1999年   3篇
  1990年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1971年   1篇
  1969年   2篇
  1965年   1篇
排序方式: 共有70条查询结果,搜索用时 437 毫秒
51.
In order to formulate appropriate strategies for the conservation and utilization of the wild mulberry genetic resources available in India, a study was undertaken with 20 mulberry genotypes from the four different species. Seventeen intersimple sequence repeat primers were used to generate a total of 114 markers, of which 98 (85.96%) were polymorphic. Seven unique bands for Morus serrata Roxb. and one for both M. serrata Roxb. and Morus macroura Miq. were identified, of which one fragment has been sequenced and deposited in the EMBL-GeneBank (AJ-585512). The genetic dissimilarity coefficients varied from 0.078 to 0.530 among these genotypes and from 0.168 to 0.465 among the species. The dendrograms realized from these markers clustered the genotypes into three groups. The outermost group was M. serrata Roxb., which was followed by the group of M. macroura Miq. and the innermost group contained genotypes of Morus indica L. and Morus alba L. This intermixing of genotypes of M. indica and M. alba supports the view that M. indica is merely a synonym of M. alba. Distribution of the genotypes on a two-dimensional figure upon multidimensional scaling with ALSCAL program, further, confirmed the genetic divergence between the cultivated and wild mulberry groups. On the basis of the results a few potential wild mulberry genotypes were identified for its conservation and utilization in breeding programs to confer the stress tolerance to the cultivated varieties of mulberry.  相似文献   
52.
Long-term soil cultivation at the same depth affects soil characteristics and crop productivity. The aim of the study was to investigate the impact of a long-term different intensity soil tillage methods and deep loosening on weed number, weed agrobiological group and soil seed bank changes in till Bathygleyic Dystric Glossic Retisol soil under the climatic conditions of the Western Lithuania (geographical coordinates 55°43′38″N, 21°27′43″E). The study included different soil tillage methods (conventional ploughing, shallow ploughing and shallow ploughless tillage) and deep loosening. During investigational years, the greatest weed number in crops and the greatest weed seed number in the seed bank were determined in the soil reduced tillage (shallow ploughing and shallow ploughless tillage). The weed number in crops of conventional ploughing soil was 35.8% lover compared to reduced tillage soil. The weed seed number in the seed bank of conventional ploughing was 49.6% lover compared to reduced tillage Decreasing soil tillage intensity resulted in weed seeds concentration in the upper topsoil. A one-time deep loosening had a significant effect during the crop rotation: the weed number in crops and weed seed number in the seed bank were determined to have increased by 26.6% and 51.6% in conventional ploughing soil and by 11.9% and 23.2% shallow ploughless soil respectively. However, after deep loosening, the number of Poa annua in crops decreased 2.9 times in plots of conventional ploughing and 1.7 times – in plots of shallow ploughing soil.  相似文献   
53.
The form of sulfur fertilizer can influence its behavior and crop response. A growth chamber study was conducted to evaluate five sulfur fertilizer forms (ammonium sulfate, ammonium thiosulfate, gypsum, potassium sulfate, and elemental sulfur) applied in seed row at 20 kg S ha?1 alone, and in combination with 20 kg phosphorus pentoxide (P2O5) ha?1, to three contrasting Saskatchewan soils. Wheat, canola, and pea were grown in each soil for 8 weeks and aboveground biomass yields determined. The fate of fertilizer was evaluated by measuring crop sulfur and phosphorus concentration and uptake, and supply rates and concentrations of available sulfate and phosphate in the seed row. Canola was most responsive in biomass yield to the sulfur fertilizers. Sulfate and thiosulfate forms were effective in enhancing soil-available sulfate supplies in the seed row, crop sulfur uptake, and yield compared to the elemental sulfur fertilizer. Combination of sulfur fertilizer with monoammonium phosphate may provide some enhancement of phosphate availability, but effects were often minor.  相似文献   
54.
The presence of Eimeria spp. oocysts in fecal samples collected from 1,108 broiler houses in six regions, representing about 12% of all broiler farms in Turkey, was studied using the modified McMaster method. The age of the chickens in the 1,108 pens varied from 1 to 50 days. Oocysts were found in 602 (54.3%) of these broiler houses, and the mean OPG (oocysts per gram of feces) in those samples was 36,498.7 (50–952,000). No indication of clinical coccidiosis or other clinically evident infection or wide mortality was encountered in any of the pens studied. Further study showed that the age of the chickens, the occurrence of diarrhea on the houses and the density of broiler breeding in the area correlated with subclinical coccidiosis prevalence.  相似文献   
55.
56.
57.
The effects of organic manure supplementation on rice–pulse cropping system productivity were studied. Three pulses, viz., blackgram, greengram and pea were grown after rice on the same plots to explore the feasibility of growing second crops with carry-over residual soil moisture and residual soil fertility. The study revealed that during the rainy season, 30%–35% higher rice grain yield was obtained when both inorganic and organic sources of nutrients were applied compared with the full dose of inorganic fertilizer, and the rice grain yield was 65%–78% higher than obtained following farmers’ practices. In the post-rainy season, pea crop recorded the highest grain yield of 490 kg ha-1 under the treatment combination of Sesbania and inorganic fertilizer. Organic carbon, and available N, P, K also enhanced yield by 20%–29%, 5.0%–29.4% to 7.9%–39.9% and 22.4%–60.3%, respectively when 25% N was applied through different organic sources of nutrients (green manure/press mud/farmyard manure).  相似文献   
58.
In the present study, hybrid and inbred oysters were produced by factorial hybridization between two closely related species, the Pacific oyster Crassostrea gigas and the Portuguese oyster C. angulata. Tissues samples were used for the analysis of total lipid content (TLC) and fatty acid composition (FAC). In general, FAC but not TLC in hybrid oysters was significantly different from inbred oysters. Hybrid oysters have significantly lower ∑SFA composition but higher ∑PUFA composition than inbred oysters, with heterosis for ∑SFA, ∑MUFA and ∑PUFA of ?6.03%, ?6.53% and 14.31% respectively. Moreover, hybrid oysters have significantly higher EPA + DHA content and n3/n6 PUFA ratio than inbred oysters, indicating higher lipid nutritional quality than inbred oysters. Among them, the hybrid ♀ C. gigas × ♂ C. angulata appears to be the most nutritious. These results indicated that the lipid nutritional quality of oysters can be improved by hybridization.  相似文献   
59.
Stigmasterol, isolated from the bark of Butea monosperma was evaluated for its thyroid hormone and glucose regulatory efficacy in mice. Its administration at 2.6 mg/kg/d for 20 days reduced serum triiodothyronine (T3), thyroxin (T4) and glucose concentrations as well as the activity of hepatic glucose-6-phophatase (G-6-Pase) with a concomitant increase in insulin indicating its thyroid inhibiting and hypoglycemic properties. A decrease in the hepatic lipid peroxidation (LPO) and an increase in the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) suggested its antioxidative potential. The highest concentration tested (5.2 mg/kg) evoked pro-oxidative activity.  相似文献   
60.
The green mussel, Perna viridis is known to have the ability to selectively ingest certain suspended particles from water. However, the preferential ingestion of specific phytoplankton taxa by P. viridis under different environmental conditions is not well understood. A study was undertaken to identify the phytoplankton taxa that are preferentially ingested and rejected by P. viridis in different environmental conditions at Marudu Bay, Malaysia. Phytoplankton abundance and composition in stomach and surrounding waters were determined microscopically. The gonad development stages of P. viridis and various environmental parameters of the bay including temperature, salinity, dissolved oxygen, current speed, pH, visibility, chlorophyll a, nutrients concentration and suspended particles were also determined. Results of current study demonstrated that selective ingestion in P. viridis was mainly influenced by seston concentration, phytoplankton abundance and composition. At high seston concentration with low phytoplankton abundance, P. viridis selectively ingested Coscinodiscus spp. In contrast, P. viridis was found to ingest wider range of phytoplankton at low seston concentration and high phytoplankton abundance. Interestingly, Chaetoceros spp. and Bacteriastrum spp. were selectively rejected by P. viridis in both high and low seston conditions. Nevertheless, no selective ingestion behaviour was evidenced in low seston with low phytoplankton conditions. Besides phytoplankton, zooplankton has also contributed significantly in the diet of P. viridis, where high numbers of copepod and bivalve larvae were found in the stomach. The findings of current study can be useful in determining potential farming sites for green mussel in future.  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