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71.
辽宁杨树主要病虫害的识别及防治 总被引:3,自引:0,他引:3
文章对辽宁省杨树速生丰产林建设发展中经常遇到的病虫害进行了介绍,并重点阐述了发生在杨树上的主要种类蒙古象甲、黑绒金龟、白杨透翅蛾、杨干象、青杨天牛、光肩星天牛、杨树溃疡病、杨树腐烂病、杨树黑斑病的形态识别、危害部位和防治方法等。 相似文献
72.
A comparison of agrisilvicultural systems with plantation forestry in the Atlantic Lowlands of Costa Rica 总被引:1,自引:0,他引:1
Survival and growth data (ages 0–5 years) are presented for two timber species (Acacia mangium, Cordia alliodora) planted in monocultures or in association with a sequence of agricultural cropsZea mays, Zingiber officinale andEugenia stipitata (a fruit shrub) in the tropical humid Caribbean lowlands of Costa Rica. Average annual height and diameter growth rates were 3.2 m and 4.0 cm (C. alliodora), 3.5 m and 3.8 cm (A. mangium).C. alliodora associated with crops gave the greatest productivity with an average total stem volume increment of 19 m3 ha–1 yr–1. Root rot ofA. mangium (mainlyRosellinia sp.), leading to tree mortality, was greater in pure plots compared to associated plots.A. mangium can not be recommended for similar sites because of this problem. 相似文献
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Designing pest-suppressive multistrata perennial crop systems: shade-grown coffee in Central America
During most of its cultivation in Central America, coffee (Coffea arabica L.) suffered few serious pest problems. However, over the past three decades, three factors contributed to significantly
increase pest levels and losses: the recent introduction of new pests; more favorable conditions for existing pests, diseases,
and weeds due to lower shade levels; and secondary pest problems caused by pesticide use. The strategy of maximizing coffee
production with pest control dominated by synthetic pesticides has not only increased yields substantially, but also production
costs, pesticide resistance, and both human health and environmental risks. An analysis of the response of the food web in
coffee plantations to varying levels of light and humidity associated with different shade levels provides the basis for identifying
the optimum shade conditions which minimize the entire pest complex and maximize the effects of beneficial microflora and
fauna acting against it. These optimum shade conditions for pest suppression differ with climate, altitude, and soils. The
selection of tree species and associations, density and spatial arrangement, as well as shade management regimes are critical
decisions for shade strata design. Site-specific knowledge of the seasonal food web dynamics permits growers to determine
the appropriate seasonal shade management in order to further suppress pest levels. For example in a low-elevation dry coffee
zone, 35 to 65% shade promotes leaf retention in the dry season and reduces Cercospora coffeicola, weeds, and Planococcus citri; at the same time, it increases the effectiveness of microbial and parasitic organisms without contributing to increased
Hemileia vastatrix levels or reducing yields. In these conditions, shade should be at a maximum early in the dry season and at a minimum by
the middle of the rainy season. Further research is needed on: the effects of individual tree species on the food web; the
role of canopy architecture for coffee vigor, photosynthesis, leaf drying, pest susceptibility, and pruning regimes; and on
simple observation methods and decision criteria for farmer management of tree-coffee-food web interactions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
76.
Martina M. Backes 《Agroforestry Systems》2001,50(2):119-132
In order to precisely assess the role of agroforestry for the conservation of (agro-)biological diversity there is a need
to adjust sampling methods used in plant sociology. This study is on the contribution of agroforestry land use to the in-situ conservation of indigenous trees within a typical East-African smallholder farming system in Western Kenya. A modified approach
to measuring species richness and abundance is presented. The selection of tree-rich structures was done according to management
patterns rather than considering syntaxonomic classifications from the vegetation science point of view. This approach, which
is better suited to the strongly human-influenced vegetation of agroecosystems, employs between-management unit diversity
measures to help evaluate abundance and constancy of species in particular management units.
The predominant off-farm vegetation patterns are riverine forests, rocky hillsides, hedgerows, wooded grassland relicts, woodlands or colline forest
relicts and tree groves whereas the noticeable tree-rich on-farm management units are homegardens, homesteads, life fences, coffee- and banana-groves and annual cropping fields. 98% out
of all indigenous tree species known from Bungoma, occur in off-farm lands. 53% of the indigenous tree species occur in tree rich on-farm management units while 47% of the indigenous trees are dependent on the maintenance of off-farm lands. Hedgerows embody the most promising secondary vegetation structure that shows ample potential to accommodate a wide
range of indigenous perennial species outside the natural vegetation formations. The pattern of distribution of various vegetation
structures, and the mixture with diverse tree-based on-farm plots are interesting features in regard to floristic and eco-diversity on a landscape level. In this respect, three areas
that show different population densities and distinct agro-historical conditions were compared. In regions of particular high
population density the degree of association of various functional land use forms and woodland structures – each characterised
by its own floristic make-up – is comparatively high. In contrast, in regions with less population but that were settled at
a later date, one encounters fewer stands of woody plants with lower numbers of species.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
77.
YU NmglouWorld Bank Loan Project Management Center. State Forestry Administration. Beijing . China 《中国林业科技(英文版)》2002,(3)
Basedon the results of monitoring the environment of China National Afforestation Project (NAP) and the investigation on insect pests and diseases in 1.2 million ha of plantations, the author elaborates the areas, species and causes of insect pests and diseases occurring in the project's areas and provides fundamental theory for guiding environmental protection and plantation establishment in a sound way. Since the project's activities strictly follovved the guideline of environmental protection in past five years, little losses were caused by some commonly insect pests and diseases. 相似文献
78.
79.
藜蒴主要病虫害及防治技术探讨 总被引:2,自引:0,他引:2
藜蒴是我省优良的乡土阔叶树种,具有速生、耐寒、适应性广等特点,也是一种良好的造纸原料资源。近年来,随着我省藜蒴面积增大,其病虫害种类多,危害也日趋严重。文章探讨了藜蒴的主要病虫害及其防治技术,旨在更好地保护藜蒴森林资源。 相似文献
80.
杭州悬铃木方翅网蝽的捕食性天敌种类及日本通草蛉幼虫捕食作用 总被引:1,自引:0,他引:1
本文调查发现杭州悬铃木方翅网蝽Corythucha ciliata(Say)的捕食性天敌有5科7种,主要是日本通草蛉Chrysoperla nipponensis(Okamoto)、普通草蛉Chrysoperla carnea(Stephens)和小花蝽属Orius spp..日本通草蛉幼虫对悬铃木方翅网蝽成虫、若虫的捕食功能反应均符合Holling Ⅱ型方程,捕食作用强弱为:日本通草蛉3龄幼虫捕食若虫>日本通草蛉2龄幼虫捕食若虫>日本通草蛉3龄幼虫捕食成虫,其对应的搜寻效率α与处理时间Th值分别为1.0141、0.5687、0.3757和0.0075、0.0121、0.0267.成虫和若虫共存时,日本通草蛉3龄幼虫喜好捕食若虫.日本通草蛉幼虫的搜寻效应随猎物密度的增加而降低.在悬铃木方翅网蝽若虫密度相同的条件下,日本通草蛉2龄、3龄幼虫随着自身密度的增大,其平均捕食量逐渐减少,捕食作用率也相应降低,其捕食作用率E与自身密度P的关系分别为:E=0.3164 P-0.4700和E=0.3411 P-0.4762.日本通草蛉幼虫间存在分摊竞争. 相似文献