全文获取类型
收费全文 | 16372篇 |
免费 | 275篇 |
国内免费 | 1066篇 |
专业分类
林业 | 1794篇 |
农学 | 1424篇 |
基础科学 | 334篇 |
1593篇 | |
综合类 | 2069篇 |
农作物 | 2237篇 |
水产渔业 | 281篇 |
畜牧兽医 | 6510篇 |
园艺 | 713篇 |
植物保护 | 758篇 |
出版年
2023年 | 122篇 |
2022年 | 153篇 |
2021年 | 85篇 |
2020年 | 101篇 |
2019年 | 114篇 |
2018年 | 122篇 |
2017年 | 73篇 |
2016年 | 120篇 |
2015年 | 133篇 |
2014年 | 456篇 |
2013年 | 261篇 |
2012年 | 311篇 |
2011年 | 343篇 |
2010年 | 282篇 |
2009年 | 239篇 |
2008年 | 278篇 |
2007年 | 369篇 |
2006年 | 732篇 |
2005年 | 292篇 |
2004年 | 278篇 |
2003年 | 449篇 |
2002年 | 664篇 |
2001年 | 434篇 |
2000年 | 262篇 |
1999年 | 210篇 |
1998年 | 103篇 |
1997年 | 76篇 |
1996年 | 111篇 |
1995年 | 95篇 |
1994年 | 173篇 |
1993年 | 355篇 |
1992年 | 460篇 |
1991年 | 573篇 |
1990年 | 625篇 |
1989年 | 386篇 |
1988年 | 948篇 |
1987年 | 1065篇 |
1986年 | 759篇 |
1985年 | 901篇 |
1984年 | 1031篇 |
1983年 | 704篇 |
1982年 | 709篇 |
1981年 | 487篇 |
1980年 | 295篇 |
1979年 | 179篇 |
1978年 | 80篇 |
1960年 | 67篇 |
1959年 | 68篇 |
1957年 | 70篇 |
1955年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
尼泊尔引入社区林业管理已有20多年。虽然有社区林业管理促进了公有林和私有林树木生长的报道,但其对当地社区获得林产品,如木材、薪柴,以及其他非木材林产品(NWFP)的促进作用还没有完全得到证实。此外,社区林业的介入有明显的社会效益。通过资料收集和实地考察分析了尼泊尔中部山区执行社区林业政策对社会经济的影响。 相似文献
992.
Standard for Bamboo and its International Trend 总被引:1,自引:0,他引:1
WANG Zhaohui JIANG Zehui SUN QixiangResearch Institute of Wood Industry Chinese Academy of Forestry Beijing P.R. China 《中国林业科技(英文版)》2004,3(2):55-65
1 INTRODUCTIONNational forestry ecological engineering, as afundamental affair for environmental protectioncontains combating desertification, soil and waterconservation. Two measures might be taken to preventsoil and water losses. One measure is to enlarge theforest area and to stop cutting or to decrease cuttingforest so as to make forest coverage keep rising at astable speed, forest resources should be examined byremote sensing technology. The other is to control thecirculation of wood… 相似文献
993.
TIAN Xiaorui SHU Lifu WANG Mingyu ZHAO Fengjun Forest Protection Laboratory of State Forestry Administration Research Institute of Forest Ecology Environment Protection Chinese Academy of Forestry Beijing P.R.China 《中国林业科技(英文版)》2006,5(4):87-92
INTRODUCTION The moisture content of fuel is a critical parameter in fire ignition because flammability is closely dependent on it (Dimitrakopoulos et al. 2001). Dead fuel lying on the forest floor (fallen branches, litter, foliage) is the most dangerous because it is drier than live fuel and more dependent on rapid atmospheric changes. The moisture content of live fuel plays a marginal role in fire ignition, but it is critical in fire propagation modeling because the amount of water is d… 相似文献
994.
XUE Fenglian ZHAO Guangjie College of Material Science Technology Beijing Forestry University Beijing P.R.China Postgraduate major research: wood science 《中国林业科技(英文版)》2005,4(2):75-81
In recent years, many researchers all over the worldhave used inorganic compounds to improve theproperties of wood, for inorganic compounds are cheapand can be obtained easily. Furthermore, they havegood functions and are environmental-friendly if theyare well controlled (Chen Zhilin, 2003). Wood-hybridcomposite is a kind of organic-inorganic hybridmaterial(OIH). OIH means that organicmacromolecule material and inorganic material becomea mixed in molecule level to get excellent capabilities… 相似文献
995.
1 HISTORICAL PROCESS ANDPRESENT SITUATION ON PRIVATEFORESTRY IN CHINABefore 1978, all the private sectors were bannedto own forest tenure in China. At that time, forestwas managed by state-run forest farms, state-runforestry industry bureaus or collectives. When thereform and opening-up policy was initiated inChina, with the implementation of HouseholdResponsibility System (HRS) in rural areas, privatesectors began to participate in forestry. In March1981, the State… 相似文献
996.
HE Youjun CUI Guofa FENG Zongwei.Research Institute of Forestry Policy Information Chinese Academy of Forestry Beijing P.R. China. College of Resources Environment Beijing Forestry University Beijing P.R..China. Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing P.R..China 《中国林业科技(英文版)》2005,4(3):29-36
INTRODUCTIONA large number of nature resources have fosteredhuman beings in the world. However, during the lastfew decades these nature resources and biodiversitywere subjected to various anthropogenic pressuressuch as plantation, deforestation, construction ofhydro-electric project, overgrazing and exploitation andother developmental activities (He Youjun, et al, 2004b;Li Ang, et al, 2002; Swamy, et al, 2000). In order toprotect environment and biodiversity, we have to facethe challenge… 相似文献
997.
CHANG Delong SONG Zhanqian HU Weihua HUANG WenhaoLI Fuhai ZHANG Yunling. Paulownia Research Center of China Zhengzhou P.R.China. Research Institute of Chemical Processing Utilization of Forest Productsof Chinese Academy of Forestry Nanjing P.R.China 《中国林业科技(英文版)》2006,5(1):1-7
INTRODUCTIONPaulownia is one of important species with fastgrowth and high yield oriented to industry uses inChina, paulownia wood is widely used in furniture-making, decorating materials, musical instrumentsmanufacture (Jiang Jianping 1990), etc. Brown orblack stain often appears on the surface of paulowniawood during processing and using. Discolorationseriously affects paulownia utilization, and it cancause huge loss due to low grade and price causedby stain (Cheng Junqing 1983a, 1983b… 相似文献
998.
WANG Huoran WANG Zhihe XIE Peixin. Research Institute of Forestry. Chinese Academy of Forestry. Beijing . China. Forestry Institute of Chuxiong Prefecture. Yunnan Province. China 《中国林业科技(英文版)》2002,(3)
Chemical analyses were conducted with leave oils of Eucalyptus smithii, E. bakeri, E. polybractea, E. dives, E. radiata and E. macarthurii vvhich were introduced to southwestern China from Australia. It was found that the leaf oils of E. smithii, E. bakeri and E. polybractea contained 81-90% of 1 ,8-cineole, and E. dives and E. radiata contained higher a-phelandrene and piperitone. There vvere significant inter- and intraspeciflc variations in leaf oil yield, it also varied with seasons in vvhich leaves vvere harvested. The results suggested that more research should be undertaken to identify genotypes with high-yield of leaf oils. These species could be applied to develop community forestry. 相似文献
999.
本文介绍一种森林抽样样本容量表。简单随机抽样用迭代公式计算样本容量,该式将样本容量表示为估计的变动系数和规定容许相对抽样误差的函数。迭代法在林业中用于计算样本容量时被证明并非都是收敛的。这里介绍一种修正的迭代方案,并编成数表来使用。 相似文献
1000.
扦插是林木无性繁殖较喜用的,因能从单株获得大量的插条苗,可避免嫁接的不亲和性,同时,插条比其他无性繁殖方法和压条、嫁接等的材料的获得要便利。实生苗茎部插条桉树实生苗扦插容易形成根系,Gior-dano于1961年用赤桉一年生苗基部(0—30厘米)扦插,其生根率在60%以上。通常插条需要3个月以上才能生根。但葡萄桉在同 相似文献