全文获取类型
收费全文 | 651篇 |
免费 | 23篇 |
国内免费 | 122篇 |
专业分类
林业 | 102篇 |
农学 | 73篇 |
基础科学 | 65篇 |
141篇 | |
综合类 | 297篇 |
农作物 | 33篇 |
水产渔业 | 14篇 |
畜牧兽医 | 49篇 |
园艺 | 16篇 |
植物保护 | 6篇 |
出版年
2024年 | 5篇 |
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 31篇 |
2020年 | 32篇 |
2019年 | 30篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 49篇 |
2015年 | 33篇 |
2014年 | 38篇 |
2013年 | 49篇 |
2012年 | 59篇 |
2011年 | 61篇 |
2010年 | 64篇 |
2009年 | 40篇 |
2008年 | 34篇 |
2007年 | 40篇 |
2006年 | 16篇 |
2005年 | 23篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有796条查询结果,搜索用时 15 毫秒
101.
C. Vanderghem Y. BrostauxN. Jacquet C. BleckerM. Paquot 《Industrial Crops and Products》2012,35(1):280-286
A Box-Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus × giganteus for enzymatic hydrolysis. The effects of three independent variables, namely cooking time (1, 2 and 3 h), formic acid/acetic acid/water ratio (20/60/20, 30/50/20 and 40/40/20) and temperature (80, 90 and 107 °C) on pulp yield, residual Klason lignin content, concentration of degradation products (furfural and hydroxymethylfurfural) in the black liquor, and enzymatic digestibility of the pulps were investigated. The major parameter influencing was the temperature for pulp yield, delignification degree, furfural production and enzymatic digestibility. According to the response surface analysis the optimum conditions predicted for a maximum enzymatic digestibility of the glucan (75.3%) would be obtained using a cooking time of 3 h, at 107 °C and with a formic acid/acetic acid/water ratio of 40/40/20%. Glucan digestibility was highly dependent on the delignification degree. 相似文献
102.
103.
研究了Fenton试剂强化微电解工艺预处理中纤板热磨废水的效果。结果表明,保持废水中亚铁离子(Fe2+)和过氧化氢(H2O2)的摩尔比为0.05~0.10,反应30 min后将废水pH值调到8.5,可进一步将微电解出水的化学需氧量值从14 000 mg.L-1降低到3 500 mg.L-1左右,大幅提升了预处理的效果,并为后续的生化处理提供良好的基础。另外,对热磨废水和最终出水进行了气相色谱/质谱联用技术(GC-MS)分析,结果显示,微电解-Fenton氧化工艺的氧化能力可以打开所有热磨废水中单环萜烯的键,将它们氧化成低碳原子的酯类、醇类和酮类化合物,但还不足以将废水中所有双环萜烯的键打开。图5表1参13 相似文献
104.
焦化废水是一种难降解的有机废水,常规的生物处理工艺难以使其达标排放。本文采用先混凝预处理后生化处理的方法,探讨有机无机改性聚合氯化铝和助凝剂对高浓度、高色度焦化废水预处理的效果,其中CODcr和NH3-N的去除效率与药剂投放量、废水温度、原水浓度以及曝气时间有一定的相关性。研究结果表明:在药剂投放量为3.0~3.5 mg/L,废水处理温度30~40℃,废水CODcr浓度稀释调整到2 000~3 000 mg/L,其CODcr的去除效率可达70%以上,NH3-N的去除率可达50%以上。滤液经生化处理,曝气为30 h,其CODcr的去除效率可达88.87%,NH3-N的去除率可达59.30%。该试验的混凝预处理减轻了后续生化处理的压力,从而提高了生化系统的处理效率。此外,混凝沉淀物还可作为燃料加以资源化利用。 相似文献
105.
106.
107.
A two-step method was developed to evaluate potato resistance to black scurf caused by Rhizoctonia solani. Tuber piece inoculum was first conducted in the laboratory, which was also first reported in this study. After inoculation with pathogen discs and culture for 48 h, the necrotic spots on the inoculated potato pieces were generated and measured by the crossing method. Further evaluation was conducted through field experiments using a wheat bran inoculum method. The wheat bran inoculum was placed into the pit dispersedly and surrounded seed tubers. Each cultivar or line was subjected to five treatments of 0-, 2-, 3-, 4-, and 5-g soil inoculum. The results showed that 2–4 g of wheat bran inoculum was the optimum for identifying tuber black scurf resistance. The laboratory scores positively correlated with the incidence and severity of black scurf in the field. According to the results in the laboratory, relatively resistant cultivars could be selected for further estimation of tuber black scurf resistance in field experiments. It is a practical and effective screening method for rapid identification of resistant potato germplasm, which can reduce workload in the field, shorten time required for identification. 相似文献
108.
病害是导致沙打旺(Astragalus adsurgens)草地产量下降的主要原因之一。本研究用杀菌剂对沙打旺种子进行预处理,在培养皿和盆栽两种培养条件下模拟沙打旺种子在自然环境中受到不同病原真菌侵染后的萌发和生长状况,探讨杀菌剂预处理的作用和效果。结果表明,人工接种病原菌后,经杀菌剂处理的种子,其发芽率,植株的株高、根长和干重较无菌水处理种子显著提高(P0.05),而发病率、死亡率和平均病情指数则相应地显著降低(P0.05)。不同杀菌剂的防治效果有所不同,在多菌灵、代森锰锌和甲基托布津3种杀菌剂中,代森锰锌预处理防治效果最好。 相似文献
109.
为了提高稻草(RS)的转化率和产物收率,采用了超声、蒸汽爆破和Na_2SO_3处理3种方法对稻草进行预处理(处理后的稻草分别记为CS-RS、ZQ-RS和Na_2SO_3-RS),通过XRD、SEM、元素分析及化学组分含量分析,筛选出Na_2SO_3处理是最好的预处理方法。Na_2SO_3-RS在200℃下经10%Fe-resin在3.3%的NaCl溶液中水解后,转化率达到97.3%,还原糖(TRS)和平台化合物乙酰丙酸(LA)的产率分别达到为29.6%和13.5%。 相似文献
110.
Silicon influences cadmium translocation by altering subcellular distribution and chemical forms of cadmium in peanut roots 总被引:1,自引:0,他引:1
Effects of silicon (Si) on subcellular distribution and chemical forms of Cd in two contrasting peanut cultivars, Qishan 208 (low seed Cd cultivar) and Haihua 1 (high seed Cd cultivar), were investigated by a hydroponics experiment at low Cd level (0.2 μM CdCl2). Two cultivars differ in Cd translocation, subcellular distribution and chemical forms. In comparison to Qishan 208, Haihua 1 shows higher translocation factors (TFs); this may be resulted from higher Cd in the soluble fraction, and a larger proportion of inorganic Cd (extracted by 80% ethanol) and water-soluble Cd (extracted by d-H2O) in roots. Pretreatment with Si decreased Cd in the cell wall, and enhanced Cd in the soluble fraction for both cultivars. However, effects of Si on chemical forms and TFs are cultivar dependent. Si enhances Cd translocation and the d-H2O extractable Cd in Haihua 1. Positive correlations were observed between TF and Cd in the soluble fraction (r = 0.71, P < 0.05), and between TF and d-H2O extractable Cd in root (r = 0.89, P < 0.001). Therefore, larger proportion of d-H2O extractable Cd may be responsible for high TF in Si pretreated plants of Haihua 1. 相似文献