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161.
可变竞争区域类竞争指标根据对象木某个描述型指标函数确定竞争区域;而树冠在树木的生长过程中具有重要的作用,并且反映了树木的长期竞争水平,根据这两种思想提出一种新的竞争可变区域类竞争指标——树冠影响度。采用典型选样法设置研究样地,并对样地内树种的各个测树因子进行调查统计,应用树冠影响度对数据进行分析讨论,结果显示:样地树种平均树冠影响度为0.359 4,样地中群落竞争相对较弱,群落结构相对稳定,其中马尾松(Pinus massoniana)的树冠影响度最小,为0.261 3;枫香(Liquidambar formosana)的树冠影响度最大,为0.510 1。优势种群树种平均树冠影响度小于非优势种群树种,优势种群受到的竞争较小,竞争能力较强,针叶树种平均树冠影响度小于阔叶树种树种,针叶树在群落中处于优势地位。 相似文献
162.
163.
国有林场在内蒙古林业生态建设中具有骨架作用,是祖国生态安全屏障的重要组成部分与支撑点,也是贯彻落实生态文明建设,践行“绿水青山就是金山银山”理念不可或缺的重要实施主体。在深入了解与掌握内蒙古自治区西部地区6个市国有林场经营现状的基础上,总结归纳了内蒙古西部地区国有林场经营的特点,深入分析了内蒙古西部地区国有林场面临的问题与困境,并探讨解决这些问题的途径,为国有林场今后的发展提出了合理化建议。 相似文献
164.
165.
通过对旺苍县盐井河采育场10多年来引种栽培日本落叶松的结果与旺苍县外其它地区的引种栽培试验结果和本地华山松的生长情况进行对比分析,证明引种是成功的,进一步探讨了日本落叶松在旺苍的引种效果和生态适应性,提出了旺苍自然地理分布的引种适生区,是旺苍北部中山区主要速生造林树种之一。 相似文献
166.
167.
Responses of the endemic leguminous shrub Bauhinia faberi var. microphylla, to various soil water supply regimes were studied in order to assess water stress tolerance of seedlings. Two-month-old
seedlings were grown under water supply regimes of 100, 80, 60, 40, and 20% water field capacity (FC), respectively, in a
temperature and light-controlled greenhouse. Plant height and leaf number were measured monthly over a 4-month period, while
water use (WU), water-use efficiency (WUE), leaf relative water content (RWC), biomass production and its partitioning were
recorded at the end of the experiment. Seedlings exhibited the greatest biomass production, height, basal diameter, branch
number, leaf number, and leaf area when soil content was at 100% FC, and slightly declined at 80% FC. These parameters declined
significantly under 60% FC water supply, and severely reduced under 40 and 20% FC. RWC, WU and WUE decreased, while the ratio
of root mass to stem mass (R:S) increased in response to decreasing water supply. Water stress caused leaf shedding, but not
plant death. The results demonstrated that B. faberi var. microphylla seedlings could tolerate drought by reducing branching and leaf area while maintaining a high R:S ratio. However, low dry
mass and WUE at 40 and 20% FC suggested that the seedlings did not produce significant biomass under prolonged severe water
deficit. Therefore, before introducing B. faberi var. microphylla in vegetation restoration efforts, water supply above 40% FC is recommended for seedlings to maintain growth. 相似文献
168.
In this paper, the basic principle of chromosome walking is presented and we used an actin gene of radiata pine (Pinus radiata) as an example to conduct upstream and downstream chromosome walking for EST sequences. The full genomic sequence (2154 bp)
of the actin gene, including promoters 5′ UTR, CDS and 3′ UTR, was identified by chromosome walking. PCR amplification and DNA band sequencing
from 200 unrelated radiata pine trees revealed a total of 21 SNPs for the actin gene, three in the promoter region, 15 in CDS and 4 in 3′ UTR. The results of this experiment provide a technical framework
for SNPs discovery in none coding regions of candidate genes.
__________
Translated from Acta Botanica Boreali-Occidentalia Sinica, 2007, 27 (8): 1571–1576 [译自: 西北植物学报] 相似文献
169.
Land use plays a much more important role than other factors, such as climate, soil properties, topographic features, vegetation
coverage, human activities and others, in affecting soil erosion and sediment discharge. In order to understand the effects
of changes in land use on sediment discharge and to provide a theoretical basis for land use planning, management and ecological
restoration, we used the controlled Qiaozidong watershed and the uncontrolled Qiaozixi watershed in the third sub-region of
the Loess Plateau as examples and analyzed the effects of land use and land cover on the discharge of sediments. The results
show that the impact of land use and land cover on the annual amount of sediment discharge is significant. Compared with the
uncontrolled watershed during similar periods, the amount of sediment discharged from the controlled watershed was reduced
by 44%, 75% and 86%, respectively, in wet, normal and dry years. In the controlled watershed, compared with the period from
1986 to 1994, the amount of sediments discharged was less during the period from 1995 to 2004. The impact of land use and
land cover on sediment discharge demonstrated characteristics of seasonal fluctuation. The effects of sediment reduction in
the controlled watershed were greater than those in the uncontrolled watershed in May and September. In the controlled watershed,
the reduction effect coincided with the distribution of rainfall. The amount of discharged flood sediments is closely correlated
with rainfall, rainfall intensity in a 60 min period and the volume of flood. The rainstorm-runoff process and the rainstorm-sediment
discharge process demonstrate that land cover has a strong regulatory and control function in the flood process and sediment
discharge in rainstorms. For the controlled watershed, given the same precipitation frequency distribution, the average amount
of sediment discharged during the land use period from 1995 to 2004 was less than that during the earlier land use period
from 1986 to 1994 under every recurrent period.
__________
Translated from Journal of Beijing Forestry University, 2007, 29(6): 115–122 [译自: 北京林业大学学报] 相似文献
170.
以苏南丘陵区邓下小流域为研究区,针对目前小流域内植被物种多样性状况和水平,选择物种丰富度指数(33、Shannon—Weiner指数(SW)、Simpson指数(SP)和Pielou均匀度指数(J)作为物种多样性的测度指标,分析不同植物群落结构特征。对流域内现有主要植被类型(茶园、杉木林、马尾松林、毛竹林、水田和旱耕地共6种)以0—10cm,10—20cm,20~40cm和40~60cm分层挖土壤剖面,分析各植被类型下土壤养分效应,以期为小流域综合治理与植被恢复中植被模式选择提供理论指导。 相似文献