全文获取类型
收费全文 | 322篇 |
免费 | 9篇 |
国内免费 | 10篇 |
专业分类
林业 | 15篇 |
农学 | 15篇 |
基础科学 | 12篇 |
128篇 | |
综合类 | 106篇 |
农作物 | 8篇 |
水产渔业 | 6篇 |
畜牧兽医 | 7篇 |
园艺 | 38篇 |
植物保护 | 6篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 31篇 |
2011年 | 22篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 14篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有341条查询结果,搜索用时 15 毫秒
1.
Cities around the world are investing in urban forest plantings as a form of green infrastructure. The aim is that these plantations will develop into naturally-regenerating native forest stands. However, woody plant recruitment is often cited as the most limiting factor to creating self-sustaining urban forests. As such, there is interest in site treatments that promote recruitment of native woody species and simultaneously suppress woody non-native recruitment. We tested how three, common site treatments—compost, nurse shrubs, and tree species composition (six-species vs. two-species)—affected woody plant recruitment in 54 experimental plots beneath a large-scale tree planting within a high-traffic urban park. We identified naturally regenerating seedling and sapling species and measured their abundance six-years after the site was planted. This enabled us to examine initial recruitment dynamics (i.e. seedlings) and gain a better understanding of seedling success as they transition to the midstory (i.e. saplings). Seedling and sapling recruitment (native and total) was greater in areas with higher canopy cover. The combination of the nurse shrub treatment with compost and species composition (six-species) treatments increased seedling recruitment by 47% and 156%, respectively; however, the nurse shrub treatment by itself decreased seedling recruitment by 5% and native seedling recruitment by 35%. The compost treatment alone had no effect on the total number of recruits but resulted in 76% more non-native seedlings. The sizes of these treatment effects were strongly dependent on whether the forest plantings were in open areas, versus areas with existing tree canopy, the latter condition facilitating recruitment. Our findings therefore suggest that combinations of site treatments, paired with broad canopy tree species, may be most effective for promoting regeneration of native species resulting in more self-sustaining urban forests. 相似文献
2.
3.
《Communications in Soil Science and Plant Analysis》2012,43(17):2636-2646
Slickspot peppergrass (Lepidium papilliferum) is an herbaceous biennal or possibly perennial “rare” endemic plant of the southwestern Idaho high desert listed as a threatened species. This plant establishes perennial seed banks, with seeds remaining dormant and viable for several years. This study aimed to enhance the germination and early growth of this plant by adopting a new medium, a nutrient-enriched agar solution, also added with humic acid (HA) and water-extractable organic matter (WEOM) fractions isolated from a green compost (GC) and a mixed compost (MC). The germination percentage of slickspot peppergrass in this new medium was much greater than that obtained in previous studies. Further, the addition of GC-HA in the medium enhanced significantly the germination and early growth of this plant. The addition of GC-WEOM and MC-WEOM were beneficial only on plant growth for at least 7 months. 相似文献
4.
《Communications in Soil Science and Plant Analysis》2012,43(21):2661-2674
A synthetic superabsorbent polymer used to improve water-holding capacity of soils was investigated. Two water qualities, two irrigation intervals, and two application rates were administered to 24 treated soil columns. Polymer absorbance of water was proportional with time but inversely proportional to salinity levels. After a threshold period, which was longer for the lower water application rate, cumulative evaporation (E = √ct) increased with decrease in irrigation interval and the type of amendments added in order of control > peat moss > the absorbent copolymer. The value of c was largely determined by the water application rate and the type of the soil amendment. Salt and moisture distributions were governed by the amount of water conserved. Peat moss was more effective in leaching salts. The quantity of water applied per irrigation, rather than cumulative amount, seemed to affect water conservation, whereas the cumulative amount of water affected electrical conductivity–sodium absorption ratio (EC-SAR) distributions. 相似文献
5.
蘑菇培养料加入864菌液发酵与二次发酵的效果比较 总被引:1,自引:0,他引:1
通过加入864菌液发酵和二次发酵栽培蘑菇的试验,比较培养料中微生物群落、培养料成份及产菇量,说明加入864菌液发酵是代替二次发酵栽培蘑菇的较好方法。 相似文献
6.
蘑菇培养料二次发酵新工艺初探 总被引:3,自引:0,他引:3
通过对培养料二次发酵不同加热控温方法及培养料堆放形式的比较试验,认为控温培养后再行巴氏消毒的二次发酵新工艺可有效地把二次发酵原理同我国食用菌栽培条件相结合,取得显著的增产节能效果。 相似文献
7.
8.
9.
This experiment evaluated the influence of manure, peat, and vermiculite incorporated at low and high rates (0.0118 and 0.0236 m3/m2) and under two soil moisture regimes on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling (1+0 for 1+1) xylem water potential (xylem), whole-plant growth, root architectural development, and subsequent field performance under fertilized and non-fertilized conditions. Trends in soil moisture retention were observed (high manure > high peat > control) but there were no differences in xylem. Root length in the wetter soil moisture experiment was initially (three months) greatest for seedlings in high vermiculite and least in high manure but there were no differences among treatments at lifting (eight months). Mean height was greatest for seedlings grown in vermiculite and peat (wetter nursery experiment) after two field seasons. Field fertilization (35 g/seedling) with controlled-release fertilizer in the planting hole stimulated height growth initially, but decreased height and diameter growth during the second growing season. Dramatic improvements associated with the use of nursery soil amendments were not realized, but the failure to identify negative effects, a potential reduction in disease incidence, and improvement of nursery soil physical and chemical properties may justify their use. 相似文献
10.
Anthony S. Davis Douglass F. Jacobs Kevyn E. Wightman Zonda K. D. Birge 《New Forests》2006,31(2):293-303
Bareroot hardwood seedling production involves intensive soil management. To increase soil organic matter (OM), nurseries
commonly grow a cover crop for 1 year after every 1–2 year of seedling production. Raising soil OM levels can also be achieved
through addition of soil amendments. We studied the influence of chicken manure (CM) and composted leaf, tree, and lawn trimmings
(Cp) on soil properties and morphology of green ash (Fraxinus pennsylvanica Marsh.) and northern red oak (Quercus rubra L.) seedlings. CM was applied at 725, 1450, or 2900 kg ha−1 (CM725, CM1450, and CM2900, respectively) and Cp was applied at 200 m3 ha−1. Addition of CM and Cp significantly raised soil OM levels and altered soil chemical properties compared to the control (Ctrl).
Root-collar diameter increased with addition of CM1450, CM2900, or Cp compared to CM725 or Ctrl plots for northern red oak,
but was largest in soils amended with CM2900 for green ash. Conversely, height was greatest with addition of CM725 for northern
red oak, but green ash seedlings were shorter in Ctrl plots than in all amendments except for CM725. Root volume of green
ash and northern red oak seedlings was positively influenced by addition of CM or Cp. Seedling responses to nursery soil amendments
vary with different forms and amounts of OM. Benefits to seedling growth through application of appropriate materials in the
proper balance can improve seedling morphological quality and positively influence soil chemical properties. 相似文献