全文获取类型
收费全文 | 264篇 |
免费 | 5篇 |
国内免费 | 23篇 |
专业分类
林业 | 12篇 |
农学 | 40篇 |
25篇 | |
综合类 | 98篇 |
农作物 | 49篇 |
畜牧兽医 | 7篇 |
园艺 | 58篇 |
植物保护 | 3篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 19篇 |
2012年 | 16篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 22篇 |
2006年 | 19篇 |
2005年 | 13篇 |
2004年 | 13篇 |
2003年 | 3篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有292条查询结果,搜索用时 15 毫秒
51.
为了解当前东北春麦区小麦生产品种和后备品系对中国小麦秆锈菌生理小种21C3CTH、21C3CFH和34MKG的抗性水平,于2006-2010年对来自辽宁、吉林、黑龙江和内蒙古的68份小麦品种和947份后备品系进行了苗期和/或成株期抗秆锈病鉴定。结果表明,有48份小麦生产品种和877份后备品系对秆锈病表现抗性,占供试材料的70.56%和92.61%,这说明东北春麦区小麦生产品种和后备品系对小麦秆锈病的抗性普遍较强,但仍存在部分感病品种和感病后备品系,秆锈病发生与流行的威胁依然存在。 相似文献
52.
茉莉3品种叶肉细胞超微结构的季节变化研究 总被引:2,自引:0,他引:2
应用透射电镜对地栽3茉莉品种叶肉细胞超微结构的季节变化进行详细观察和比较研究。结果显示,3茉莉品种春季和秋季叶肉细胞的超微结构完整,但夏季和冬季3茉莉品种叶肉细胞超微结构变化明显且品种间的变化有差异。茉莉遭受高温(夏季)或低温(冬季)胁迫时,叶肉细胞超微结构的变化具有适应意义,但随着胁迫时间的延长,细胞亚显微结构会受伤害。比较研究结果表明,双瓣茉莉比单、多瓣茉莉抗低温和高温能力更强,有细胞超微结构基础,在高温和低温胁迫下,双瓣茉莉细胞超微结构更稳定。 相似文献
53.
[目的]探讨3个紫薇品种的花粉离体培养与萌发。[方法]以3个紫薇品种(‘红蝶飞舞’、‘翠盘堇薇’和‘紫爪银薇’)的盛花期花粉为材料,对花粉离体培养及花粉管萌发进行了研究。[结果]筛选出紫薇花粉萌发的最适培养基为150 g/L蔗糖+60 mg/L硼酸+20 mg/L CaC l2+20 mg/LMgSO4+100 mg/L KNO3,其中蔗糖和硼酸的浓度对紫薇花粉萌发有明显影响。紫薇的长、短花丝萌发力存在差异,其中‘紫爪银薇’和‘红蝶飞舞’短花丝的花粉萌发力高于长花丝,而‘紫爪银薇’相反。在荧光显微镜下观察,自交授粉后2~6 h内花粉萌发形成花粉管,花粉管生长速度由快到慢。[结论]为培育紫薇新品种提供了理论依据。 相似文献
54.
Pawitar Singh O. P. Choudhary Pritpal Singh 《Communications in Soil Science and Plant Analysis》2018,49(3):334-343
Most of the crop salt tolerance studies are often conducted in a glasshouse and are limited under field conditions. Therefore, the present research study was conducted under field conditions to evaluate the performance of six wheat cultivars at five salinity levels (EC 0, 3, 6, 9, and 12 dS m?1) in split plot design with three replications. Increasing salinity significantly increased soil pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Yield parameters of different cultivars were affected more at higher salinity levels than lower in two years. Data over two years revealed that up to EC 9 dS m?1 cultivars PBW 658 and HD 2967 performed ???better on the absolute yield basis but PBW 621 produced ?higher relative yield. At EC 12 dS m?1, PBW 658 produced significantly higher grain yield (4.23 t ha?1) than cultivars HD 2967 (4.11 t ha?1) and PBW 621 (3.99 t ha?1); therefore, should be preferred at salinity more than 9 dS m?1. 相似文献
55.
Khawar Jabran Ehsan Ullah Nadeem Akbar Muhammad Yasin Umar Zaman Wajid Nasim 《Archives of Agronomy and Soil Science》2017,63(10):1465-1476
Conventionally flooded rice (CFR) requires enormous water and labor inputs. Water scarcity aspires for cultivation of water-saving rice. Growth response and physiology of basmati rice genotypes under the water-saving production systems has not been reported yet. Studies were conducted for 2 years to compare the growth and physiology of three rice cultivars (Super Basmati, Basmati-2000 and Shaheen Basmati), under high (CFR), medium (alternate wetting and drying [AWD]) and low water input (aerobic rice [AR]) systems. Leaf area index, crop growth rate, leaf area duration and dry matter accumulation were higher for AR followed by AWD and CFR, respectively. Shaheen Basmati had a lower growth and relative water contents than Super Basmati and Basmati-2000, probably due to its shorter stature and shorter life cycle. Photosynthetic rate and stomatal conductance of rice cultivars in the different production were affected only at reproductive stage. Basmati-2000 grown as AR had the highest photosynthetic rate followed by the same cultivar under AWD. The results of this study provide us an idea that basmati cultivars can attain a high growth and development with low water input. This would be helpful to grow rice successfully under water-short rice-growing environments. 相似文献
56.
The objective of this work was to assess the effect of the incidence of cassava anthracnose disease (CAD) on the performance and yield of cassava cultivars planted in Owerri, Imo state. Eighteen cultivars were planted in a randomized complete block design and replicated three times over a period of 3 years. Cultivars TMS 30211, TMS 30001, 98/0510 and TMS 4(2)1425 were regarded as resistant due to the possession of more than three desirable characteristics such as the least size of cankers and absence of cankers in the first and second trials (2003/04 and 2004/05) respectively, lowest severity score and highest weight of healthy fresh tuber and stems. They are recommended for use as parent materials for breeding for resistance to CAD. Cultivar Akwakwuru had the largest size of cankers on whole plant, highest fresh weight of infected tubers and stems which led to low yield and less planting materials. It is regarded as susceptible and may lead to spread of CAD. The correlation of weight of infected fresh tubers on size of canker on whole plant, young stem and maturing stem were positively and highly significantly correlated (r = 0.645, r = 0.470, r = 0.583 and r = 0.622, respectively). 相似文献
57.
58.
《Communications in Soil Science and Plant Analysis》2012,43(3):284-296
Photosynthetic traits are affected by many environmental factors, of which the most important ones are microclimate of crop stand and meteorological conditions. A 2-year field study was conducted to determine the photosynthetic rate (P) and chlorophyll index (SPAD) alteration in various spring barley cultivars throughout development stages under field conditions. The tests involved three seed rates (SR) [200 (SR I), 400 (SR II), and 600 (SR III) viable seeds per m2] and three cultivars (Aura DS, Barke, and Gustav). The measurements were made four times during the growing season. In 2008, the P values were the greatest at BBCH 45 under warm conditions coupled with a lack of rainfall. The spring barley cultivars differed in tolerance of the weather conditions between the experimental years. The P of Barke was the greatest in warm and dry conditions (2008), and that of Gustav was greatest mainly in wet conditions. The P of Aura DS was lower than the trial mean in both years. The SRs effect on P and SPAD was significant only in sporadic cases. The variation of P and SPAD depended significantly (P ≤ 0.05, P ≤ 0.01) on the weather factors and their interaction. 相似文献
59.
Root size,distribution and soil water depletion as affected by cultivars and environmental factors 总被引:1,自引:0,他引:1
Field experiments were carried out in two parts at the Luancheng Experimental Station in the North China Plain. Part I, which was a continuous experiment that ran from 1990 to 2008, investigated the change of grain yield, evapotranspiration (ET), root size and soil water utilization of winter wheat (Triticum aestivum L.) under three water regimes (rain-fed, two and four irrigation applications). Part II used 10 cultivars released from 1970 to 2000 that were grown under the same condition for two seasons (2005/2006 and 2006/2007) to compare root size, root:shoot ratio and soil water depletion (SWD). The results of testing in Part I showed that the yield and ET of winter wheat gradually increased from 1990 to the present. There was no consistent change in total root length (TRL) over time. The difference in root size among seasons and irrigation treatments mainly occurred in the upper soil profile, where the root length density (RLD) was greater. No direct relationship was found between root size and soil water use. Thus, TRL was not a factor that indicated the water extracting capacity of crops. The results from Part II revealed that the seasonal ET of earlier released cultivars (ERC) was similar to that of recently released cultivars (RRC) under well-watered conditions. However, ET was slightly increased from ERC to RRC under water deficit conditions, indicating high soil water depletion by RRC. TRL decreased from ERC to RRC and was significantly correlated with plant height. The breeding of winter wheat that reduced plant height not only increased harvest index, but also reduced root size, resulting in a smaller root:shoot ratio. The reduction in TRL from ERC to RRC mainly occurred in the top soil profile. The results from both tests indicate that TRL is not a factor that determines soil water use; rather, the distribution of RLD along the soil profile plays more important role in soil water utilization. Smaller root size in the upper soil layer did not affect soil water uptake, and might be more economical in terms of production efficiency. 相似文献
60.
Instrumental and sensory quality characteristics of blueberry fruit from twelve cultivars 总被引:1,自引:0,他引:1
Robert Saftner James Polashock Mark Ehlenfeldt Bryan Vinyard 《Postharvest Biology and Technology》2008,49(1):19-26
We compared the instrumental and sensory quality characteristics of blueberry fruit from ten highbush (Vaccinium corymbosum L.) cultivars, Chanticleer, Weymouth, Hannah's Choice, Duke, Bluecrop, Coville, Berkeley, Bluegold, Elliott and Lateblue and two rabbiteye (Vaccinium virgatum Aiton) cultivars, Coastal and Montgomery, grown in New Jersey. Cultivars varied in sensory intensity and acceptability scores. Highbush cultivars, Coville and Hannah's Choice, scored highest among the cultivars in sensory scores for intensity of blue color, juiciness, sweetness and blueberry-like flavor and for acceptability of appearance, color, fruit size, sweet/tart balance, flavor and overall eating quality. In contrast, rabbiteye cultivars, Coastal and Montgomery, and the highbush cultivars, Elliott and Weymouth, scored lowest among the cultivars in sensory scores for intensity of bursting energy, skin toughness, texture during chewing, juiciness, and blueberry-like flavor and for acceptability of appearance, color, fruit size, flavor and overall eating quality. Analytical quality characteristics of surface color, size, compression firmness, soluble solids content (SSC), pH, titratable acidity (TA), SSC/TA ratio, and aromatic volatile concentration also varied among cultivars, but no instrumental measurement adequately predicted consumer acceptability scores. The overall eating quality of blueberry fruit was best correlated with flavor scores followed by sensory scores for intensity of juiciness, bursting energy and sweetness and for acceptability of appearance. 相似文献