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通过比较中美森林法的历史和现状,指出森林法修改和完善的紧迫性且时机已经成熟,以及森林法修改要重视理论研究和实际情况调查。我国森林法修改和完善可以借鉴美国森林法中的森林生态系统管理等先进理念。对美国《国有林管理法》与《中华人民共和国森林法》的结构与体例、立法精神、科学的地位、公众参与等内容进行了比较研究,据此给出一些《中华人民共和国森林法》的修改建议。 相似文献
123.
辽宁省森林生态系统服务功能及其价值初步研究 总被引:5,自引:0,他引:5
从生态系统服务功能的概念入手,根据2005年辽宁省森林资源清查数据和有关研究资料,采用替代工程、市场价值等方法,从直接经济价值和间接经济价值两方面评价了辽宁省森林生态系统服务功能的价值。 相似文献
124.
W.A. Houston 《Mangroves and Salt Marshes》1999,3(1):29-40
A hailstorm in October 1994 was found to have moderately or severely impacted on 5.3% of the mangrove forests in Port Curtis. All mangrove species showed evidence of hail damage, including the three most common species (Rhizophora stylosa, Ceriops tagal and Avicennia marina). Physical effects of hail damage included stripping of leaves from plants, holes punched through leaves, bruising to bark, divots removed from bark, branch and plant death. Speciesspecific differences in vulnerability to the effects of hail were observed with C.tagal experiencing relatively higher mortality rates than the other two common mangrove species. A delayed pattern of mortality was observed in two species _ C.tagal and A.marina. Alterations to mangrove community structure included: (1) reductions in stem density, stem diameter and basal area, (2) reductions in canopy cover (based on a photographic index of foliage projective cover) and (3) changes in relative abundance of species in mangrove zones. Recovery was observed in some stands but others had not recovered to prehail levels of canopy cover two years after the hailstorm. Recovery had occurred by regeneration of fresh leaves but no recruitment of young plants had been observed during the study. The forests in the impact area were dominated by either Ceriops tagal or Rhizophora stylosa with Avicennia marinaas a subdominant in places. C.tagal dominated forests within the impact area were relatively more severely affected (41.8% in the severe category) than R.stylosa dominated communities (only 17.4% in the severe category). This indicated that C.tagal dominated forests were more vulnerable to the effects of hail damage than R.stylosa dominated forests. In addition, hailimpacted C.tagal dominated forests represented a relatively high percentage of the area of C.tagal dominated forests in Port Curtis (44.3%). This percentage was much higher than hailimpacted R.stylosa dominated forests in Port Curtis (2.7%). These two factors – relatively severe impact on C.tagal communities and a relatively higher percentage affected within the Port Curtis area – illustrate that hailstorms, as a form of natural disturbance, are an important influence on the forest ecology of mangrove ecosystems in this region. 相似文献
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基于EDA技术的自动立木整枝机无线遥控发射系统 总被引:4,自引:0,他引:4
立木整枝是优质工业用材林定向抚育的重要环节,采用自动立木整枝机是实现高效、高质量和安全可靠整枝的有效途径。本文综合运用电子电路设计及优化技术、无线遥控及通信编解码技术,创造性地研制了基于CPLD的无线数字编码抗干扰自动立木整枝机无线遥控发射系统,通过优化CPLD内部逻辑电路有效消除了逻辑竞争冒险、降低了噪声干扰,确保了系统逻辑设计的正确性。该系统具有可靠、节能、抗干扰、工作效率高等优点。本研究成果及方法为推进其他林业机械的自动化与智能化进程提供了一种有效的新思路。 相似文献
128.
Cao Jin-zhen Yu Li-li You Xiao-di Kamdem D. Pascal 《中国林学(英文版)》2007,9(4):239-245
In order to clarify the interaction between copper and wood substances in wood treated with copper containing water-borne wood preservatives, the dielectric constant ε′ and dielectric loss factor ε″ of untreated wood and wood treated with four concentration levels of copper-ethanolamine (Cu-EA) solutions were determined within a temperature range from –100 to 40°C and a frequency range from 100 to 1 MHz. Three dielectric relaxation processes were observed in the ε″ spectrum; among them R-I is based on the reorientation of methylol groups in the amorphous region of wood cell walls and R-II is related to wood extractives. R-III appeared in Cu-EA treated wood, and its magnitude decreases with the concentration of Cu-EA solutions used in this experiment. This relaxation process was considered to be based on the reorientation of copper-ethanolamine-wood complexes in wood cell walls. At low copper retention, the hydrogen in the complex can form hydrogen bonding with adjacent hydroxyl groups, which results in a strong bonding state between copper and wood; at high copper retention, the numerous copper-ethanolamine complexes not only hinder them from forming hydrogen bonding with adjacent wood molecules due to steric hindrance, but also weaken the interaction between wood molecules themselves, which corresponds to reducing ε″ values of both R-I and R-III processes. The results explain the fact of in-creasing copper leaching in wood treated with high concentration copper-based water-borne preservatives. 相似文献
129.
Takao Kishimoto Tsutomu Ikeda Olov Karlsson Kengo Magara Shuji Hosoya 《Journal of Wood Science》2002,48(1):32-37
Methyl-d-xylopyranoside was allowed to react with-O-4-type quinone methide without a catalyst to elucidate the reactivities of secondary hydroxyl groups at the C2, C3, and C4 positions. Benzyl ether-type lignin-carbohydrate complex (LCC) compounds linked at the C2 and C4 positions were predominant, at a ratio of 23. However, the reactivity of the hydroxyl group at the C3 position was quite low. These results strongly suggest that the reactivity of the C2 hydroxyl group in xylan toward quinone methide intermediate is higher than that of the C3 hydroxyl group during biosynthesis of LCCs. 相似文献
130.
Jeffrey Chow 《Journal of Sustainable Forestry》2015,34(6-7):651-681
Mangroves worldwide provide a wide range of ecosystem services utilized directly and indirectly by local peoples. Between 1966 and 2001, Bangladesh established approximately 148,000 ha of mangrove plantations in coastal areas within the Barisal and Chittagong Divisions. Though erosion and human encroachment and conversion have removed over two-thirds of these stands, the Forest Department has continued to undertake new plantation activities.To investigate how and to what degree people directly utilize these mangroves, I conducted 340 household surveys across eight coastal villages located in close proximity to established plantations. The predominant direct use of the mangrove plantations by local rural communities is the extraction of detritus and nonmain stem material (e.g., limbs, leaves) for combustible fuel. This study uses household foraging distances to estimate and map net value densities based on reported market prices of extracted goods. The average extractive value of mangrove plantations is Tk 2,300 ha?1 yr?1, ranging among the villages from 300 to Tk 27,400 ha?1 yr?1, with values concentrated closer to the village. Cost-benefit analyses suggest that direct use values alone have justified the establishment and management of previously planted stands. However, other indirect values must be taken into account if these areas are to merit additional plantations. 相似文献