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991.
Plant species diversity of homegardens of Cuba and its significance for household food supply 总被引:3,自引:0,他引:3
The cultivation of different plants in homegardens for self-sufficiency has a long tradition in Cuba, but knowledge about homegardens in Cuba is small. To analyse this more deeply, cultivated plants of 31 homegardens were surveyed in three villages in eastern Cuba in 2001. Two of the study villages were located in a humid area with an annual precipitation of about 2200 mm. The third village was situated in a semiarid area with about 450 mm precipitation. The plants studied in the homegardens included those for human consumption such as fruits, vegetables, tubers and cereals as well as spices and medicinal plants. In total, 101 different plant species were found with an average number of 18 to 24 species per homegarden for the three villages. A broad range of species was found in all villages, because irrigation is used under semiarid conditions, which lead to a relative high similarity in species composition between the villages. But, also differences due to the climatic situation became evident, particularly with the medicinal plants. In general, homegarden production provided a broad and diverse basis for self-sufficiency of the households. Although homegarden production showed to be only a small source of income, it is particularly important because of low-paid outside work and minimal food provision of the state.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
992.
993.
北京八达岭植物群落多样性特征分析 总被引:5,自引:0,他引:5
根据34个样地的调查资料,分析了该地区森林植物群落物种多样性的特征:群落内各层物种丰富度指数的大小为草本层>灌木层>乔木层;多样性指数的大小为乔木层<灌木层和草本层。灌木层与草本层的多样性指数随林分郁闭度变化而变化,在林分郁闭度为25%的侧柏黄栌混交林中,灌木层的多样性指数和丰富度指数小于草本层;在郁闭度53%的杂木林中,灌木层和草本层的多样性指数接近;在郁闭度53%以上的各个群落内,草本层的多样性指数和丰富度指数基本上都大于灌木层。人工林中的物种多样性变化多样,明显低于天然林,林分层次单一,更新不良,缺乏灌木层和地被植物,生态系统很不稳定。 相似文献
994.
Toru Kohama Nobuya Mizoue Satoshi Ito Akio Inoue Kotaro Sakuta Hiroyuki Okada 《Journal of Forest Research》2006,11(4):235-242
We examined the extent to which direct and indirect measures of light and microsite conditions could explain variation in
tree height and diameter at the base of 6-year-old Cryptomeria japonica trees planted in a group selection opening of about 0.32 ha on a steep slope at Shiiba, Miyazaki Prefecture, southern Japan.
We first used the gap light index (GLI) and soil thickness (ST) as directly measured indices. For an indirect measure of light, we used a between-cohort competition index (BCI) estimated from the position and total height of residual trees. For indirect measures of microsite, we examined topographic
indices (slope, plan and profile curvature, average slope gradient, and relative elevation) derived from digital elevation
models (DEMs) with different resolutions ranging from 2 to 10 m. The multiple linear regression using GLI and ST explained about 45% of variation in tree size, while simple regression using only GLI explained about 35%. The contribution of ST was about half of GLI. The multiple regressions using BCI and the topographic indices did not explain any more variation than using BCI alone (R
2 of about 0.26). We conclude that microsite conditions with shallower soil and steeper slope have negative effects on tree
growth in group selection openings, although the relative importance is smaller than light conditions. More comprehensive
studies considering several openings with more heterogeneous topography including different species are needed to generalize
our growth prediction using the indirect measures, which are useful for practical forest management. 相似文献
995.
996.
997.
基于1998~2018年黑龙江省国有林业产业数据,从发展规模、产业结构、投入产出效益、专业化水平等4个方面对黑龙江省国有林业产业发展现状进行总体概述和分析。借助产业贡献度指标测算国有林业产业对黑龙江省经济发展的贡献水平,并基于三次产业构成进一步对国有林业产业贡献度进行了结构性动态评价。研究得出:黑龙江省国有林业产业对地区经济发展贡献呈现稳步上升的特征,第一产业表现突出,第二、三产业呈小幅下降、小幅上升的反向变动特征。基于结果分析,从产业自身发展和持续推进多种经营产业转型两个方面提出方向性建议。 相似文献
998.
999.
立地管理措施对2代4年生杉木林生长的影响 总被引:14,自引:1,他引:14
在福建省南平峡阳国有林场开展5种不同立地管理措施对1片29a生第1代杉木人工林采伐后营造的4a生第2代杉木人工林生产力影响的研究。研究结果表明,5种处理的第2代杉木林地位指数与第1代相比均略有下降。BL3BM0(收获树干和树皮、加倍采伐剩余物)处理的4a生2代杉木林生长最好,地位指数仅比1代下降0.67;其次为BL0BM0(收获地上所有有机质)处理,地位指数比1代下降0.85;BL1BM0(清走树木的所有部分)处理杉木生长最差,地位指数下降1.67。炼山处理(BL2BM1)与保留相同数量采伐剩余物而不炼山的处理(BL2BM0)相比,杉木生长没有显著差异。 相似文献
1000.