全文获取类型
收费全文 | 1378篇 |
免费 | 46篇 |
国内免费 | 93篇 |
专业分类
林业 | 97篇 |
农学 | 135篇 |
基础科学 | 128篇 |
433篇 | |
综合类 | 596篇 |
农作物 | 33篇 |
水产渔业 | 23篇 |
畜牧兽医 | 38篇 |
园艺 | 18篇 |
植物保护 | 16篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 28篇 |
2020年 | 29篇 |
2019年 | 33篇 |
2018年 | 26篇 |
2017年 | 45篇 |
2016年 | 53篇 |
2015年 | 66篇 |
2014年 | 58篇 |
2013年 | 86篇 |
2012年 | 135篇 |
2011年 | 114篇 |
2010年 | 99篇 |
2009年 | 83篇 |
2008年 | 63篇 |
2007年 | 90篇 |
2006年 | 81篇 |
2005年 | 68篇 |
2004年 | 49篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 36篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有1517条查询结果,搜索用时 15 毫秒
71.
72.
P. Jiménez O. Ortiz D. Tarrasón M. Ginovart M. Bonmatí 《Biology and Fertility of Soils》2007,44(2):393-398
This work has evaluated the effects of thermally dried (TDS) or composted (CDS) dewatered sewage sludge on β-glucosidase activity,
total (TCH) and extractable (ECH) carbohydrate content, microbial biomass carbon and basal respiration of soils from limestone
quarries under laboratory conditions. Two doses (low and high) of the dewatered sludge (DS) or of the respective TDS or CDS
were applied to a clayey and a sandy soil, both coming from working quarries. The soil mixtures and the controls (soils with
no added sludge) were incubated for 9 months at 25°C and 30% of field capacity. The addition of sludge increased all the studied
soil parameters, and the increase depended on the amount of sludge. Except in the case of TCH and ECH, the enhancing effect
decreased with time, but at the end of incubation, parameters of the treated soils were higher than those of the control.
The rank order of the initial stimulating effect was soil–TDS ≥ soil–DS ≥ soil–CDS, and probably, this order depended on the
proportion of stable organic matter, which was the lowest in the TDS. Values of metabolic quotient (qCO2) were higher at the lower dose, and they did not change during incubation in the CDS-treated soils. Both TCH and ECH were
the parameters with the greatest significant sludge and dose effects. Basal respiration, microbial biomass carbon and β-glucosidase
activity were the best measured parameters in distinguishing the long-term effects of the three sludge types over the soils. 相似文献
73.
通过现场调查采样及室内分析,研究了兰州市七里河安宁污水处理厂和雁儿湾污水处理厂污泥中重金属的形态分布特征,并对其进行了潜在生态风险评价。结果表明,污泥总体呈高有机质、高全N和有效P、高微量营养元素,且Cu、Zn、Cd、Pb、Ni5种重金属的含量均低于污泥农用控制标准,具有很好的农用价值。污泥中Zn、Cd、Pb主要以有机结合态和残渣态存在,而Cu、Ni可交换态所占比例较高,分别为14.95%和14.41%,不稳定态所占比例分别为41.12%和31.04%,表现出较高的生物活性和可利用性。七里河和雁儿湾污泥中重金属的潜在生态风险属于低度风险;Cd、Cu是污泥中重金属潜在生态风险的主要贡献者,在污泥处理处置时应引起高度重视。 相似文献
74.
75.
Sanae El Maaloum Alae Elabed Zainab El Alaoui-Talibi Abdelilah Meddich Abdelkarim Filali-Maltouf Allal Douira 《Communications in Soil Science and Plant Analysis》2020,51(5):622-634
ABSTRACTThe exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation. 相似文献
76.
生物强化处理油田含油污泥的试验研究 总被引:1,自引:0,他引:1
采用油泥、菌剂及其他添加物充分混合后堆放的方法,进行了3种条件下的微生物对含油污泥的强化分解研究。结果表明,在菌剂和锯末的共同作用下,经过45d后,污泥含油量从24%下降到11%,去除率达到54%;而菌剂单独作用下,含油量下降到16%,去除率达为33%;在没有菌剂作用下,含油量仍然保持在20%以上。对处理过程中pH变化特性进行了研究。试验说明,生物强化分解是含油污泥处理的有效途径。 相似文献
77.
本文比较了来自不同有机物组合的三种堆肥(马粪和垫草,貂场废弃物,城市生活垃圾和污泥)和纸浆厂固体废弃物对提高番茄生长的影响.番茄、水芹、小红萝卜种植在有机养分贫瘠的土盆中,发芽后评价四个处理的植物毒性.结果表明:马粪和垫草,貂场废弃物能刺激番茄苗根部和地上部的生长,城市生活垃圾堆肥和纸浆厂固体废弃物有强烈的抑制作用;城市生活垃圾堆肥和无修复的土壤同样抑制种子萌发,纸浆厂固体废弃物处理使水芹和小红萝卜苗畸形发育,这些处理的有毒成分和养分失调都可能造成生长抑制的影响,不经过腐熟的纸浆厂固体废弃物施用到农业土壤有可能对蔬菜类植物造成有害的影响. 相似文献
78.
浸提时间对污泥中重金属浸出的影响 总被引:2,自引:0,他引:2
[目的]探讨污泥中重金属的释放动力学特性。[方法]采集了我国南京某污水厂的剩余污泥,应用固体废物浸出毒性的浸出方法,研究了浸提时间对污泥中重金属浸出的影响。[结果]污泥中重金属在水溶液中的浸出存在明显的吸附-解吸(释放)的动态平衡过程。污泥中重金属种类的最大浸出浓度因重金属种类的不同而存在较大差异,其中,Cr、Cu、Fe、Ni和Zn的最大浸出浓度均出现在第8小时,Mn的则出现在第18小时左右,而Mo虽然在第8小时后的浸出浓度变化渐趋缓慢,直到第24小时时仍未达到其最高浸出浓度。[结论]浸提时间对污泥中重金属的浸出影响显著,污泥具有较高含量的有机质、氮和磷等营养元素,其潜在的农业利用价值较高。 相似文献
79.
《Journal of plant nutrition》2013,36(8):1311-1323
Tomato (Lycopersicon esculentum Mill.) yields are known to decrease for plants grown in saline soils. This study was conducted to determine the effects of arbuscular mycorrhizal fungi (AMF) inoculation on fruit yield and mineral content of salt-tolerant and salt-sensitive tomato cultivars grown with varied levels of salt. NaCl and CaCl2were added to soil in the irrigation water in equal molar ratios to give ECe values of 1.4 (nonstressed) and 4.9 dS m?1 (salt stressed). Plants were grown in a greenhouse using unsterilized, low phosphorus (P) (silty clay) soil-sand mix. Mycorrhizal root colonization occurred whether cultivars were salt stressed or nonstressed, but the extent of AMF root colonization was higher in AMF inoculated than uninoculated plants. The salt tolerant cultivar ‘Pello’ generally had higher AMF root colonization than the salt sensitive cultivar ‘Marriha’. Shoot dry matter (DM) yield, fruit fresh yield, and AMF colonization were higher for plants grown under nonstressed than for plants grown under salt stressed conditions. Shoot DM and fruit fresh yields were higher in AMF inoculated than uninoculated plants grown with or without salt stress. Pello generally had higher fruit fresh yield per plant and fruit weight than Marriha, but these differences were only significant for fruit weight in unioculated plants grown under salt stressed conditions. The enhancement in fruit fresh yield due to AMF inoculation was 26 and 23% under nonstressed and 28 and 46% under salt stressed treatments for Pello and Marriha, respectively. For both cultivars, fruit contents of P, potassium (K), zinc (Zn), copper (Cu), and iron (Fe) were higher in AMF inoculated compared with uninoculated plants grown under nonstressed and salt stressed conditions. Fruit Na concentrations were lower in AMF inoculated than uninoculated plants grown under salt stressed conditions. The enhancement in P, K, Zn, Cu, and Fe acquisition due to AMF inoculation was more pronounced in Marriha than in Pello cultivar under salt stressed conditions. The results of this study indicated that AMF inoculated plants had greater tolerance to salt stress than unioculated plants. 相似文献
80.