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   165篇
  免费   4篇
  国内免费   1篇
林业   21篇
农学   19篇
基础科学   7篇
  39篇
综合类   12篇
农作物   18篇
水产渔业   13篇
畜牧兽医   22篇
园艺   6篇
植物保护   13篇
  2023年   3篇
  2022年   7篇
  2021年   2篇
  2020年   3篇
  2019年   8篇
  2018年   10篇
  2017年   9篇
  2016年   5篇
  2015年   2篇
  2014年   4篇
  2013年   14篇
  2012年   8篇
  2011年   10篇
  2010年   16篇
  2009年   9篇
  2008年   12篇
  2007年   5篇
  2006年   5篇
  2005年   4篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   3篇
  1999年   1篇
  1998年   1篇
  1996年   4篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1965年   1篇
排序方式: 共有170条查询结果,搜索用时 15 毫秒
1.
A field experiment was conducted on summer mungbean residue recycling (SMBRR) and basmati rice–wheat cropping system (BRWCS) at New Delhi, India. The SMBRR enhanced the system productivity and net returns by ~19.1% and 22.1% compared to summer fallow (SF) with highest magnitude under genotypic sequence of P 2511/HD 2967. Two genotypes each in basmati rice (PB 1 and P 2511) and wheat (HD 2967 and HD 2733) responded well to SMBRR with respect to grain yield efficiency index (GYEI) ≥ 1.0. SMBRR also registered ~13.5% higher microbial biomass carbon (MBC) than SF. Soil organic carbon (SOC) storage also increased by ~6.8% in 0–30 cm soil layer. The rice–wheat–summer mungbean system produced significantly highest energy efficiency compared to the rice–wheat–summer fallow system with highest values under genotypic sequence of P 2511/HD 2967 as a result of better yield expression. Overall, SMBRR with suitable genotypic sequence improved the system productivity, profitability, and nutrient dynamics in BRWCS, which are vital for long-term sustainability of this system.  相似文献   
2.
Although the System of Rice Intensification (SRI) has been reported to produce higher paddy (Oryza sativa L.) yields with better-quality grains, little research has addressed the latter claim. This study investigated the interactive effects of rice cultivation methods with different irrigation schedules and plant density on the uptake and concentration of sulfur (S), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in the grain and straw of two rice cultivars during two rainy seasons in the northern plains of India. As the two seasons differed in amounts of rainfall, there were impacts of soil moisture differences on nutrient uptake. Plots with SRI cultivation methods enhanced the grain uptake and concentrations of S, Zn, Fe, Mn and Cu by 36, 32, 28, 32 and 63%, respectively, compared to conventional transplanting (CT). Under SRI management, the highest concentrations of S, Zn and Cu in the grain and straw occurred with irrigation intervals scheduled at 3 days after disappearance of ponded water (DADPW; 3D), whereas Fe and Mn concentrations in the grain and straw were higher with irrigation at 1 DADPW (1 D ) compared with plots under 3 D or 5 DADPW (5 D ). The higher nutrient uptakes were also manifested in higher grain yield in 1 D and 3 D plots (by 9 and 6%, respectively) compared with 5 D . Wider spacing (25 × 25 cm) compared with closer spacing (20 × 20 cm) significantly increased yield and the uptake and concentrations of all the said nutrients in the grains. When comparing the performance of two cultivars, the total uptakes of Zn, Fe, Mn and Cu in both grain and straw were significantly more in Hybrid 6444 than the improved variety Pant Dhan 4. Overall, SRI crop management compared to CT practices led to more biological fortification of rice grains with respect to S and the four micronutrients studied, giving a concomitant yield advantage of about 17% on average in this region.  相似文献   
3.
The population of the freshwater animal was declined day by day due to the degradation of habitat and use of illegal fishing methods, which cause a great threat to these aquatic animals. The main purpose of this study was to scrutinize the wild population and fecundity of freshwater prawn Macrobrachium assamense peninsulare in Rawasan stream to assess the health status of prawn. Fecundity was estimated by a random sampling of prawn from five selected sites of Rawasan stream. A wild collection of a total of 35 ovigerous females was collected for an interval of 2 years (August 2013–July 2015) from May to September month, that is breeding session. The maximum number of eggs was 102 eggs in an individual having 52 mm total length and 2.66 g body weight. It was concluded that fecundity of Macrobrachium assamense peninsulare was low, and egg dimension was larger than other closely related species of freshwater prawn. Fecundity of Macrobrachium assamense peninsulare showed a positive relationship with a total weight (R2 = .71) and moderate with the total length (R2 = .38). A strong correlation exists between egg mass and total weight, and between egg mass and total length of female (R2 = .849 and R2 = .77 at p < .05) respectively. The numbers of eggs, that is fecundity, in a female were increased with the body growth of an individual, which results in a linear graph.  相似文献   
4.
Jamun (Syzygium cumini) is a tropical, underutilized fruit which is highly perishable in nature. It is a good source of vitamin C, tannins, gallic acid and anthocyanins and its beneficial effects are mostly due to the presence of bioactive compounds (pigments and phenolic compounds) in it. Due to astringent and fibrous nature, preparation of jam from jamun pulp is quite difficult, but other fruits (apple and kiwifruit) can be incorporated in it to improve its quality. This study aims to develop jam from blends of jamun with other fruits and analyse various physico-chemical, nutritional, textural and sensory properties. It was found that physico-chemical properties of jams were not found to vary greatly, but the jamun–kiwifruit jam was found to have fairly high amount of antioxidants(46.75 ± 0.67%), tartaric acid (26.24 ± 0.02 mg/100g sample), ascorbic acid (0.08 ± 0.01 mg/100 g sample) and lactic acid (23.95 ± 0.01 mg/100g sample) and lowest amount of 5-hydroxymethyl-2-furaldehyde (0.38 ± 0.04 mg/100 g sample). Jamun jam and jamun–kiwifruit jam possessed the texture required for jam while jamun–apple jam was found to be a relatively harder gel. Jam made with jamun and kiwifruit pulp was found to have highest acceptability on the basis of sensory evaluation.  相似文献   
5.
Tillage modifies soil structure and has been suggested as a practice to improve physical, hydrological and chemical properties of compacted soils. But little is known about effect of long‐term tillage on physicochemical soil properties and crop yield on sodic soils in India. Our objective was to investigate the effect of different tillage regimes on crop yield (wheat and paddy rice) and physicochemical properties of sodic soils. Two sodic sites under conventional tillage for 5 (5‐YT; 5‐year tillage) and 9 (9‐YT; 9‐year tillage) years were selected for this study. Changes in crop yield and physicochemical soil properties were compared with a control, sodic land without any till history, that is, 0‐year tillage/untilled (0‐YT). Five replicated samples at 0‐ to 10‐cm and 10‐ to 20‐cm soils depths were analysed from each site. In the top, 0‐ to 10‐cm soil depth 5‐YT and 9‐YT sites had higher particle density (Pd), porosity, water holding capacity, hydraulic conductivity, organic carbon, total nitrogen (Nt), available nitrogen (Navail), phosphorus (Pavail) and exchangeable calcium (Exch. Ca++) than 0‐YT, whereas bulk density (Bd), C : N ratio and CaCO3 were significantly lower. Bd, pH, EC and CaCO3 increased significantly with depth in all the lands, whereas Pd, porosity, water holding capacity, hydraulic conductivity, organic carbon, Nt, Navail, Pavail and Exch. Ca++ decreased. We conclude that continuous tillage and cropping can be useful for physical and chemical restoration of sodic soils. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
6.
Kamath JV  Rana AC 《Fitoterapia》2002,73(2):111-115
The effect of ethanolic extract of the roots of Calotropis procera has been studied in albino rats to explore its antifertility and hormonal activities. A strong antiimplantation (inhibition 100%) and uterotropic activity was observed at the dose level of 250 mg/kg (1/4 of LD(50)). No antiestrogenic activity could be detected.  相似文献   
7.
A field experiment was conducted with a bunched variety of peanut (Arachis hypogaea L.) cv. JL-24 during the summer seasons (March–June) of 1992 and 1993 in the humid tropical canal command area at the University Experimental Farm, Memari (23°1 N, 88°5 E and 21.34 m a.s.l) in West Bengal of eastern India. The soil at the site is of sandy loam (Typic Fluvaquent) texture and the area has a shallow water table. Weekly and seasonal field water balance components of actual evapotranspiration (ETa) including the capillary contribution into root zone were determined. Peanut yield and water productivity were determined for three ratios of irrigation water and cumulative pan evaporation (CPE) of 0.9, 0.7 and 0.5. Mean crop coefficients were determined for each 7-day period of growth and were related to leaf area index and growing degree-days. Average seasonal values of ETa of peanut were 434, 391 and 356 mm for the three treatments, respectively, for 115 days of growth. The total pod yield and WP were significantly higher in 0.9 IW:CPE treatment in the 1992 season. On an average, 0.9 IW:CPE treatment had 7 and 11% higher yields in 1992 and 1993, respectively, over treatments 0.7 and 0.5 IW:CPE. The maximum average Kc of 1.19 occurred about 9 weeks after sowing relative to grass reference ET (ETo).  相似文献   
8.
Summary The measurement of water consumption in the field is normally restricted to research purposes, although the development of practical field criteria for timing water application is required to improve crop productivity. To develop such criteria irrigation experiments on Soybean were conducted from flowering to grain filling at four locations which differed in their soil properties and the convective contribution of their climates to potential evapotranspiration. The energy balance, predawn leaf water potential (PLWP), soil moisture depletion, and a crop water stress index (CWSI) based on foliage temperature were measured. The range of soil, atmospheric, phenological and irrigation conditions, produced a common, linear relation between relative evapotranspiration (rET) and the logarithm of -PLWP. Correlation with the temperature based CWSI was weak. A similar relation with PLWP for other C3 plants was also derived from data in the literature. This relation could be helpful for irrigation scheduling once the critical values of rET for crop productivity are known.  相似文献   
9.
The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is an important insect pest of canola, Brassica napus L., in Ardabil, Iran. Host plant resistance is an essential component of integrated management of P. xylostella. We investigated the preferences and performance of P. xylostella on nine commercial cultivars of canola, namely Zarfam, RGS003, Adder, Okapi, Opera, Hyola401, Ebonite Option500 and Elite under greenhouse conditions at 23 ± 1°C, 50 ± 5% RH and 14L:10D. In free-choice situation, oviposition was lowest on Opera (23.5) and highest on Zarfam (44.7). In the life table study, fecundity of new generation female moths was lowest on Opera (95.4) and highest on Adder (145.7). Survival from egg to adult was significantly lower on Opera, Option500 and Hyola401 than on other tested cultivars. The intrinsic rate of natural increase (r m) and population growth rate (λ) were lowest on Opera and highest on Zarfam. The generation time (T) was shortest on Zarfam (17.2 days) and longest on Hyola401 (19.9 days) whereas doubling time (DT) was longest on Opera (3.9 days) and shortest on Zarfam (3.0 days). Our results clearly suggest that Opera was the most resistant host among the tested cultivars and has the potential to be used in the integrated management of P. xylostella.  相似文献   
10.
Segregation for salinity tolerance and ISSR markers based molecular polymorphism were investigated in a F3 plant population raised via single-seed descent method from a cross between salt-tolerant indica rice variety CSR10 and salt-susceptible premium traditional Basmati rice variety Taraori Basmati HBC19. A total of 130 F3plants were evaluated individually for salinity tolerance on 1–9 scale on the basis of seedling growth parameters; the average score ranged between 1.7 to 8.3. Frequency distribution curve obtained using the salinity tolerance data of F3 population and a chi-square analysis, showed a good fit to a normal distribution. Eleven plants each in the category of salt-tolerant and salt-susceptible were selected from the segregating F3 population for ISSR marker analysis. A total of 149 bands (4–11 bands per primer) ranging from 200 to 3530 bp were scored for the two rice varieties and the selected CSR10 × HBC19 segregating F3 plants using 26 ISSR primers. Of these, 89 were monomorphic and 60 were polymorphic. Of the 60 polymorphic bands,36 and 20 bands were specific to CSR10 andHBC19 respectively. The remaining four bands were amplified using UBC primers 810,848, 853 and 886 and present in only some of the CSR10 × HBC19 F3 plants. Notably, ISSR primers with dinucleotide repeat motif and 5'-anchored end amplified more number of bands (7.0 bands/primer) compared to3'-anchored dinucleotide primers (5.4bands/primer), but 3'-anchored dinucleotide primers revealed higher level of polymorphism (2.6 polymorphic bands/primer) compared to 5'-anchoreddinucleotide primers (1.43 polymorphic bands/ primer). While distribution of majority of the polymorphic bands were more or less in the expected ratios in salt-tolerant and/or salt-sensitive F3segregating plants, but some of the bands amplified using UBC ISSR primers 823, 825,826, 849, 853, 864, 866 and 884 showed highly skewed distribution. Such polymorphic bands stand greater chances of having a linkage with the genes/ QTLs for salinity tolerance and shall be the target for further studies. This revised version was published online in July 2006 with corrections to the Cover Date.  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