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   112篇
  免费   4篇
  国内免费   7篇
林业   75篇
农学   2篇
  5篇
综合类   37篇
农作物   2篇
畜牧兽医   2篇
  2024年   1篇
  2022年   1篇
  2020年   2篇
  2019年   1篇
  2018年   2篇
  2017年   3篇
  2016年   1篇
  2015年   3篇
  2014年   7篇
  2013年   2篇
  2012年   11篇
  2011年   5篇
  2010年   1篇
  2009年   5篇
  2008年   6篇
  2007年   2篇
  2006年   10篇
  2005年   3篇
  2004年   9篇
  2003年   8篇
  2002年   1篇
  2001年   4篇
  2000年   6篇
  1999年   5篇
  1998年   7篇
  1997年   3篇
  1996年   4篇
  1995年   2篇
  1994年   3篇
  1993年   4篇
  1992年   1篇
排序方式: 共有123条查询结果,搜索用时 0 毫秒
21.
ABSTRACT

Organic matter levels combined with drought periods during the growing season have adverse impacts on rain-fed potato production in coarse textured soils of eastern Canada. Using pulp fiber residues (PFR) may build up soil organic matter, improve crops yield and nutrient uptake, and reduce the need for supplemental irrigation in this region. A box experiment with 3 rates of PFR [0, 45, and 90 Mg ha? 1 dry mater carbon (C) basis] with or without supplementary drip irrigation was established in a sandy loam soil in New Brunswick, Canada. Red clover, barley, and potato were cultivated as three crops of the rotation in 1999, 2000, and 2001, respectively. The PFR only applied before red clover in fall 1998. Selected soil chemical and physical properties were measured before planting and after harvest. Crops yield and nitrogen (N), phosphorus (P), and potassium (K) accumulation were determined at harvest. Soil organic-C content, bulk density and water holding capacity were improved by PFR application. Red clover and barley biomass production were significantly increased by PFR application. This effect was promoted by supplemental irrigation. Potato tuber yield was not affected by PFR and it was higher in rain-fed compared to supplementary irrigated system. Although, there was some initial evidence of N immobilization but generally PFR application increased N, P, and K bioavailability. This research has demonstrated that PFR can successfully be used as soil amendment in coarse textured soils without any adverse effect.  相似文献   
22.
对拟赤杨、火力楠、米槠、山乌桕等 4种阔叶树进行BCTMP制浆、打浆强度分析、漂白工艺研究、与硫酸盐木浆配抄强度比较及黑液分析 ,结果表明 ,拟赤杨、火力楠、米槠、山乌桕等 4种阔叶树具有较好的制浆适应性  相似文献   
23.
针对杨木自催化乙醇法蒸煮废液成分复杂,副产物价值高等特点,采用蒸馏-超滤法分离回收废液中的乙醇和木质素副产物,降低废液污染程度.实验分析了多种因素对分离回收过程的作用规律,确定了最佳的工艺条件.结果表明,在浓缩体积比值0.5、截留相对分子质量(Mr)10000、压力0.20MPa、搅拌速度600r/min、温度30℃的最优条件下,该法能有效回收废液中有用组分,并能显著降低废液污染程度.  相似文献   
24.
制浆生物技术的研究与工业应用   总被引:16,自引:3,他引:13  
综述了制浆工业中生物技术研究的发展简史,务类酶制剂在制浆工业中的研究与应用概况,着重介绍了当前制浆生物技术研究热点这一的木聚糖酶的研究与应用。同时简介了制浆生物技术的研究进展。  相似文献   
25.
To characterize the mechanism of the reaction of lignin with aqueous acetic acid (AW) containing a small amount of H2SO4, guaiacylglycerol--guaiacyl ether (GOG), and guaiacylglycerol--syringol ether (GOS) were refluxed in 90% AW with 0.28% H2SO4 for 0–120 min. Reaction products and their silylated derivatives were characterized by analytical methods such as gas chromatography-mass spectrometry and nuclear magnetic resonance. When the model compounds were allowed to react at boiling temperature for 0 min (heat-up time 30 min), most of their primary alcohol groups and some of their secondary alcohol groups were acetylated, but their phenolic groups were not. About 90% of GOG was degraded, polymerized, or both during boiling for at least 15 min, yielding guaiacol and isocoumaran compounds (GOG-e and GOG-f) in addition to homovanillin (II) as guaiacylvinyl alcohol (I) and other minor products. GOS yielded syringol, homovanillin (II), and a novel compound (V) together with unknown products but not the corresponding isocoumaran compounds.  相似文献   
26.
用盐酸沉淀马尾松硫酸盐制浆黑液中的木素,经离心分离,干燥后制成本素粉末。然后用木素代替部分苯酚合成本素酚醛树脂,调制供胶合板用的胶粘剂,并进行压板试验。经分离木素后的黑液,CODcr和色度均大大下降,使黑液的污染负荷大大降低。木素型胶粘剂胶合的三层胶合板的胶合强度超过了国家标准规定的指标。  相似文献   
27.
通过对目前造纸工业中6种主要造纸废液的成分对喷雾干燥工艺参数造成影响的研究,得出了不同造纸废液的喷雾干燥有不同的工艺条件,分析了废液的浓度、温度和粘度之间的相应关系,最后针对喷雾干燥出口温度高、热效率较低的特点,提出了用干燥后的热尾气浓缩稀废液节能新工艺。  相似文献   
28.
论述木片制浆生产工艺中通过利用冷喷放降低蒸煮热耗、蒸煮中期或终了汽液转注节能、放汽及喷放热能的回收利用等几种节省热能和综合利用热能的方法。制浆生产过程中的热耗主要消耗在蒸煮部分,为此,从蒸煮工艺、操作工艺入手,合理利用热能,达到提质降耗,提高经济效益的目的。  相似文献   
29.
提出了非木材木质纤维生物质碱性亚硫酸盐制浆(ASP)生物炼制的理念,研究了总用碱量、亚硫酸化度、温度和时间对麦草碱性亚硫酸盐法蒸煮深度脱木质素特性和木质素磺化的影响。结果表明:麦草ASP法具有高的深度脱木质素选择性;深度脱木质素延伸与木质素磺化度提高具有一致性;总用碱量、亚硫酸化度、最高温度和保温时间对深度脱木质素选择性和木质素磺化度都有重要的影响;在总碱用量18.0%,亚硫酸化度85.0%,液比值3.5,最高温度168℃,保温150 min的条件下,可制得卡伯值8.8,得率56.8%,黏度为33.3 mPa.s的优良纸浆,此时黑液中磺化木质素磺酸基含量达2.16 mmol/g(以固形物计)。从深度脱木质素选择性、木质素磺化和纸浆基本特性考虑,麦草ASP法具有制浆生物炼制的前景。  相似文献   
30.
The basic density of pulp wood can be used to convert green volume to dry weight, and as an indicator of the fibre quality. Because the methods for measuring basic density are cumbersome, a practical, on‐line method for sorting Norway spruce pulp wood with respect to basic density was developed. The relationship between mean annual ring width and basic density was used to sort the pulp wood. Brief visual inspection could separate piles of logs with different mean annual ring widths from each other with an acceptable precision. The resulting classes had significantly different mean basic densities (380, 400 and 434 kg m?3). Means of other properties, such as juvenile wood content, heartwood content, and dry matter content, also differed among classes.  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