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91.
92.
分析了中国东北小兴安岭林区红松种群的生活史过程及其影响因素,对红松生活史的4个阶段进行了分析,并讨论了其进化和保护对策.红松的传粉和受精主要受天气条件的影响.林冠下的光照是控制红松幼苗生长和存活的主要因素.红松种子生产的周期性波动会引起有关动物种群的相应变化.动物是阔叶红松林生态系统中不可缺少的组成成分,松鼠在红松种群的天然更新中起着非常重要的作用.了解森林生态系统中物种的协同进化关系对于我们保护森林生物多样性和生态系统的完整性有着重要的意义.在红松的保护中,我们不仅要保护树木本身,而且还应当保护与红松相关的动物、生境乃至整个生态系统. 相似文献
93.
Change in spatial characteristics of forest openings in the Klamath Mountains of northwestern California,USA 总被引:4,自引:0,他引:4
Carl N. Skinner 《Landscape Ecology》1995,10(4):219-228
Change in the spatial characteristics of forest openings was investigated in three forested watersheds in north-western Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fire suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based upon fractals. Significant differences were found using the Kolmogorov-Smirnov two-sample test between the perimeters, areas, distance from sample point to nearest opening, and distance between neighboring openings. The perimeters and areas became smaller, and the distances from the sample point to the nearest opening and between neighboring openings became greater over the 41 years between aerial photo sets. The estimated area occupied by openings decreased from 25.8 % to 15.6 % of the study area. No significant difference was found in the shape of the openings except as the shape indices were influenced by changes in size of the openings.This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献
94.
报道了中国小兴安岭云杉树上一种新干基白腐病,其病原菌为鳞片昂氏多孔菌Onnia leporina(Fr.)H.Jahn。该病主要发生在成熟林分,造成受害木干基白腐,被侵染树木极易风折或风倒而死亡。根据中国的材料对该病病菌进行了宏观和微观的详细描述,并与欧洲的材料进行了对比。 相似文献
95.
Kenji Ohse Kenji Tamura Haruo Tanaka Teruo Higashi 《Soil Science and Plant Nutrition》2005,51(1):37-42
At Mt. Hirugatake in the Tanzawa Mountains, Kanto district, Japan, the deciduous broadleaved forests have rapidly declined. In our previous studies, we reported that the amount of soil organic matter had significantly decreased at the early and final stages of forest decline, and that the soil microbial biomass also showed a large decrease at these stages, suggesting that the composition of soil organic matter might have also changed with forest decline. To clarify the influences of forest decline on the composition of soil organic matter, the amount of humic substances, optical properties of humic acid, and the amount of soil carbohydrates in surface soils at different stages of forest decline were investigated. The amounts of humic acid and fulvic acid decreased to a lesser extent at the early and middle stages of forest decline, and showed a significant decrease at the final stage. As the amount of humin significantly decreased at the early stage, it was plausible that the distinct decrease in the total carbon content of the soil surface horizons at the early stage of forest decline was induced by the decrease in the amount of humin, and at the final stage, by the decrease in the amounts of humic acid and fulvic acid. The amount of soil carbohydrates did not change appreciably with forest decline although the soil organic matter content markedly decreased. It was suggested that most of the carbohydrates in the soil surface horizons were in a stabilized form consisting of complexes with humic substances, metals, and minerals, and would not be affected by the environmental changes associated with forest decline. 相似文献
96.
97.
Plant species-level research that comprises inventories, impact studies and monitoring is necessary if plant resources are to be harvested sustainably by human populations living adjacent to protected areas in sub-Saharan Africa. This research assessed the extraction of plant products from two montane forest ecosystems, Uzungwa Scarp Forest Reserve (USFR) and Bwindi Impenetrable National Park (BINP), East Africa. In USFR, data from vegetation sampling and interviews with local people were used to understand the ecological and socio-economic aspects of non-timber forest product (NTFP) harvesting. The densities of eight commonly harvested tree species, most of which were used as building poles, were approximately 2.4-4.5 times lower in disturbed versus undisturbed habitats across all four sites in USFR. Interviews with 91 women and 54 men suggested that most species were harvested for medicinal uses (57 species) and building purposes (50 species). In BINP, the liana Loeseneriella apocynoides (Apocynaceae), is harvested for basketry weaving. Evidence suggested that the liana was harvested in both protected and unprotected areas of BINP. Data collected suggested a negative impact on this species in an unprotected versus a protected area, with stem diameters larger than 1 cm significantly more abundant in the protected area. This study reveals that harvesting of NTFPs occurs even in these two protected forest areas, and that over-exploitation not only threatens species of high-demand, but could also alter forest structure and composition. Management practices that encourage the monitoring of sustainable harvesting levels of species and promote alternative plants for the same uses should be considered as part of conservation strategies. 相似文献
98.
大兴安岭水湿地改造对土壤和植被的影响 总被引:1,自引:1,他引:1
采用定位观测和抽样调查方法,对大兴安岭不湿地改造前后的土壤理化性质、植物群落特征进行了系统调查。通过分析发现,经一的水湿地土壤主要理化性质及肥力的变化均利于落叶松生长;植物群落种数呈现增加、减少、再增加的变化规律。造林10a后,草本植物大量减少,乔、灌木少量增加,植物群落向以落叶松为诉 森林群落发展。这种变化对当本地区经济发展有积极的一面。但地区域揿样性及生态环境产生不利影响。因此,对大兴安岭水湿 相似文献
99.
大兴安岭林区冻土及湿地对生态环境的作用 总被引:23,自引:0,他引:23
为研究中国大兴安岭林区生态环境问题 ,作者对大兴安岭林区高纬度多年冻土区的冻土、冻土地带的湿地和森林的生长状况进行了调研及现地考察 .结果表明 :大兴安岭的冻土退化、原始湿地萎缩和新生湿地扩张将会对大兴安岭的森林及环境造成威胁 .作者认为气候变暖和人为活动是冻土退化的主要原因 ,气候变暖和森林破坏 (大面积采伐或森林火灾 )导致冻土退化 ,不但影响冻土上层的原始湿地 ,也导致新生湿地的扩张 ,林地被湿地取代 ,形成恶性循环 .建议对冻土、湿地、森林的相互制约机理进行长期定位观测研究 相似文献
100.