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   4091篇
  免费   239篇
  国内免费   181篇
林业   487篇
农学   221篇
基础科学   25篇
  680篇
综合类   1668篇
农作物   248篇
水产渔业   15篇
畜牧兽医   294篇
园艺   483篇
植物保护   390篇
  2024年   24篇
  2023年   72篇
  2022年   118篇
  2021年   162篇
  2020年   260篇
  2019年   200篇
  2018年   94篇
  2017年   130篇
  2016年   196篇
  2015年   146篇
  2014年   190篇
  2013年   221篇
  2012年   252篇
  2011年   297篇
  2010年   214篇
  2009年   255篇
  2008年   253篇
  2007年   242篇
  2006年   200篇
  2005年   156篇
  2004年   134篇
  2003年   81篇
  2002年   88篇
  2001年   64篇
  2000年   67篇
  1999年   62篇
  1998年   43篇
  1997年   39篇
  1996年   42篇
  1995年   31篇
  1994年   33篇
  1993年   25篇
  1992年   23篇
  1991年   22篇
  1990年   21篇
  1989年   20篇
  1988年   13篇
  1987年   9篇
  1986年   5篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1955年   2篇
排序方式: 共有4511条查询结果,搜索用时 31 毫秒
951.
在探明菌根真菌美味红菇生理活性物质的基础上,为使其实用化,又从该菌的发酵液中提取并研制成真菌复合制剂。除在医学上进行了一系列抗菌活性试验外,同时还在育苗造林上,利用不同树种进行防病保苗促进生长的生物活性试验。本文主要报道应用美味红菇复合制剂对几种亚热带针阔叶树种幼苗和种子进行体内生物活性的试验结果。目的在于观察和研究该复合制剂对促进幼苗生长和提高抗生能力的生物效应,以便进一步开拓美味红菇复合制剂的有效应用范围和途径。  相似文献   
952.
确证15种霉菌可引起毛竹材霉变,对这15种霉菌的分类学形态特征及其在毛竹材上诱致的霉变外貌特征进行了详细描述;指出其中10种霉菌为毛竹材重要致霉菌,提出在竹材霉变试验中可选用菌体相对覆盖量目测法估计竹材霉变程度。  相似文献   
953.
954.
刺革菌科10种主要木材腐朽菌的培养特性   总被引:2,自引:0,他引:2  
通过对子实体进行组织分离获得菌种,并将其接种子PDA平板培养基上,25℃恒温培养,根据菌落细胞外氧化酶检测反应、菌丝类型及分化、产孢情况、菌丝及菌落颜色、刚毛及表皮细胞的有无等培养特性,对刺革菌科10种主要木材腐配菌培养特性及鉴定分类系统地进行了研究。  相似文献   
955.
Khasa  P.D.  Sigler  L.  Chakravarty  P.  Dancik  B.P.  Erickson  L.  Mc Curdy  D. 《New Forests》2001,22(3):179-197
The effect of three levels of fertilizer on thegrowth of three species of containerized-grownconifer seedlings (Pinus contorta, Picea glauca, and Picea mariana) and twospecies of bare-root conifer seedlings (Pinus sylvestris and Larix sibirica),and on the colonization of these seedlings bysix species of ectomycorrhizal fungi (Hebeloma longicaudum, Laccaria bicolor,Paxillus involutus, Pisolithustinctorius, Rhizopogon vinicolor andSuillus tomentosus), was studied. Thegrowth of the seedlings in both container-grownand bare-root nurseries increased as the levelsof fertilizer increased. For better seedlinggrowth and environmental quality it may be possible to reduce the level of fertilizers in commercial nurseries upto 33% by using selected mycorrhizal fungi.Ectomycorrhizal colonization in all seedlingswas not affected by fertilizer levels. Hebeloma longicaudum, L. bicolor, P.involutus, and P. tinctorius formedwell-developed ectomycorrhizae, whereasectomycorrhizal development by R.vinicolor and S. tomentosus was poor.Native mycorrhizal fungi colonizednon-inoculated control seedlings; however,their colonization was always lower than withinoculated fungi.  相似文献   
956.
Endophytic fungi in leaves and twigs of Quercus petraea . Surface sterilized leaf and twig samples taken in 1989 from sessile oak (Quercus petraea) in Austria yielded host-specific as well as unspecific ubiquistic endophytes. In leaves, Aureobasidium apocryptum and Apiognomonia quercina were the most frequent taxa, while Colpoma quercinum was the dominant species in twigs. The colonization rates of individual species were subjected to seasonal variation.  相似文献   
957.
 The morphological features and dietary functional components of two strains (FPF-13 and Oninome-B) of Pholiota adiposa (numerisugitake mushroom) grown on artificial bed blocks were examined. The components examined were chitin, mannitol, trehalose, guanosine 5′-monophosphate, ergosterol, and β-glucan. There was a significant difference in the external shape of the two strains. However, the differences in the contents of functional components between the two strains, as well as between the pilei and stipes of the strains, were small. In both strains the trehalose content was much higher than the mannitol content, in contrast to those of Lentinula edodes. From a commercial point of view, Oninome-B has a clear advantage over other strains of P. adiposa owing to its less removable scale. Received: May 15, 2002 / Accepted: June 10, 2002 Acknowledgment The authors thank Dr. F. Eguchi (Takasaki University of Health and Welfare) for his technical advice on the β-glucan analysis. Part of this report was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001 Correspondence to:K. Shimizu  相似文献   
958.
The degradation of wood, filter paper cellulose, and a lignin-substructure model, was measured in cultures of seven fungi usually regarded as brown-rot fungi. Hydroxyl radical production and the accumulation of oxalic acid in the cultures were also measured. Four of the fungi, Gloeophyllum trabeum, Tyromyces palustris, Laetiporus sulphureus, and Postia placenta, were typical brown-rot fungi, in that they preferentially degraded and eliminated the polysaccharides in wood and produced large amounts of hydroxyl radical. The rates of hydroxyl radical generation in cultures of the four fungi were directly proportional to the degradation rates of wood, cellulose, and the lignin-related compound, and inversely proportional to the amount of oxalic acid in the cultures. Two of the fungi, Daedalea dickinsii and Lentinus lepideus, did not degrade any of the substrates significantly and produced very little hydroxyl radical. Coniophora puteana had the highest rate of cellulose degradation, but did not degrade wood or the lignin model significantly and produced only negligible amounts of hydroxyl radical. These results indicate that brown-rot fungi produce large amounts of hydroxyl radical for the degradation of wood and crystalline cellulose.  相似文献   
959.
陕西省杨树外生菌根种类的调查研究   总被引:6,自引:3,他引:6  
唐明  陈辉 《林业科学》1994,30(5):437-441
对陕西省35种杨树外生菌根的调查研究,鉴定出9种外生菌根真菌。研究证明,一种外生菌根真菌可侵染不同种杨树;一种杨树又可被不同的菌根真菌侵染,并观察到在同一小根上顶端形成菌套,中部和下部形成泡囊丛枝这一混合型菌根形态。  相似文献   
960.
探讨了白腐菌预处理对丙酸蒸解法制取纤维素的影响.在白腐菌对玉米芯进行预处理过程中,赖锰过氧化物酶(MnP)、木质素过氧化物酶(LiP)、漆酶、木聚糖酶和纤维素酶的酶活分别在第5、 6、 7、 10和 15 d 达到最高值,分别为1.326、 10.25、 0.062 7、 0.33和 403 U/g.利用响应面分析法确定丙酸蒸解玉米芯最佳工艺条件为:料液比1∶ 10(g∶ mL),蒸解时间 70 min,丙酸质量浓度 900 g/L,产物中纤维素的质量分数为 91.09%.玉米芯经白腐菌预处理 10 d 后再用丙酸进行蒸解处理,产物中纤维素的质量分数和保留率分别为 97.12% 和 94.70%,而半纤维素和木质素的质量分数仅为 0.96% 和 0.92%.  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