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Effects of forest management (thinning) on gross ammonification, net ammonification, net nitrification, microbial biomass, and N2O production were studied in the forest floor of adjacent untreated control (“C”) and thinned (“T”) plots in three beech (Fagus sylvatica L.) stands in the Swabian Jura (Southern Germany) during three intensive field campaigns in the year 2004. The investigated sites are located less than 1 km apart on the slopes of a narrow valley. Due to different exposure (southwest, northeast, northwest), the three sites are characterized by warm‐dry microclimate (southwest site, SW) and cool‐moist microclimate (northeast site, NE; and northwest site, NW). Measurements at the NW site covered the second year (13 to 20 months) after thinning, and measurements at the SW and NE sites covered the sixth year (61 to 68 months) after thinning. Mean gross ammonification varied insignificantly across the six plots (range: 37.5 ? 31.2 to 51.0 ? 10.5 mg N (kg dry soil)–1 d–1). The SW site was characterized by very low net nitrification and nitrate (NO ) concentrations that were not significantly different between control and thinned plot. In contrast, for the thinned plot at the NE site (NET), significantly increased mean net nitrification (2.3 ? 1.2 mg N (kg dry soil)–1 d–1 at the NET plot vs. 0.4 ? 0.2 mg N (kg dry soil)–1 d–1 at the NEC plot) and mean extractable NO concentrations (43.9 ? 22.8 mg N (kg dry soil)–1 at the NET plot vs. 4.1 ? 0.8 mg N (kg dry soil)–1 at the NEC plot) were observed. The differences in net nitrification and NO concentrations across the research plots were related to differences in the forest‐floor C : N ratios: net nitrification increased exponentially below a threshold C : N value of about 25. The results of this study indicate that the forest floor of the warm‐dry SW site is very resistant to N loss triggered by thinning due to high C : N ratios around 30. Under the cool‐moist microclimate of the NE site, a significantly lower C : N ratio of 22.1 at the thinned plot (control plot: 26.7) coincided with significantly increased net nitrification. Thus, different responses of net nitrification to thinning under different microclimate appear to be triggered by different C : N ratios. Nitrous oxide production was mainly governed by forest‐floor water content, and since differences in water content at adjacent control and thinned plots were low, N2O production was not significantly different between adjacent control and thinned plots. 相似文献
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间伐改变林分环境,也对林木生长、森林碳储量及林木竞争关系造成一定影响,研究15%、25%、35% 3个间伐强度处理8 a后小兴安岭天然次生林中杉木的径阶分布、碳密度分配特征及竞争指数,对森林经营的指导和森林碳汇发展有重要意义。结果表明,35%抚育间伐强度均使杉木径阶分布频率偏离正态性;间伐改变了林木各器官碳密度的分配,其趋势是随着间伐强度的增大树干碳密度占总量的比例先减小再增加,而树枝生物量分配规律则呈逐渐减小的趋势;25%和35%间伐强度,杉木地上部分的生物量和碳密度均显著大于对照样地,其中25%间伐强度时生物量和碳密度最大,而15%间伐强度的杉木生物量与对照样地无显著差异,而碳密度却小于对照样地;同CK相比,T15样地杉木的Hegyi竞争指数减少了2.05%,而T25、T35分别增加了36.07%和14.66%;冗余分析(RDA)结果表明,Hegyi竞争指数、间伐强度共同解释了碳密度变化的61.3%,且Hegyi竞争指数增长不利于林分碳密度增加,竞争压力通过改变各器官的碳密度来响应。 相似文献
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确定适宜的抚育方式以建立适宜的林分结构,使森林的多种效益得到充分发挥。此次试验采用标准地法,通过测定林分生长量、林分蓄积量及林下植被3个方面的5个指标,进行青海云杉林抚育效果调查分析。结果表明:(1)抚育间伐显著地提高了青海云杉林平均胸径和平均树高的生长量,分别提高了23%和30%;(2)抚育间伐极显著的提高了青海云杉林分的蓄积量,提高了40%;(3)抚育间伐前期明显抑制了林下灌木的生长,加快了林下草本的生长,后期灌木和草本又慢慢恢复为抚育前的状态,但林下植被种类变得单一。 相似文献
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为探讨疏穗对葡萄酒类黄酮物质含量的影响,以‘赤霞珠’为试验材料,在果实豌豆粒大小时期进行疏穗处理,葡萄藤负载量分别为22(CK)、16穗·株-1(C1)和10穗·株-1(C2)。采收成熟葡萄果实酿造干红葡萄酒,应用高效液相色谱-质谱联用(HPLC-MS)分析酒样中类黄酮物质的种类及含量。结果表明,疏穗提高了葡萄酒中单体花色苷和黄烷醇的含量,降低了黄酮醇的含量。主成分分析可以看出3种疏穗处理下‘赤霞珠’葡萄酒品质具有差异性。表明在山西乡宁地区,适度疏穗可以提高‘赤霞珠’葡萄酒中类黄酮物质的含量。其中葡萄藤负载量为10穗·株-1时,葡萄酒中类黄酮含量最高。 相似文献
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AIM:To study the effects of synthetic kainic acid (SKA) and 1-heptanol (1-Hep), a gap junction blocker, on the cytoskeletal filament expression in the astrocytes. METHODS:The neonatal rat brain was obtained from the Wistar rats (1 day old) and primary purified astrocytes were obtained by differential attachment for removing filamentoblasts and orbital shaker for removing the oligodendrocytes. The effects of SKA and other interventions on the morphologic changes and expression levels of skeleton protein filamentous actin (F-actin) were observed in the astrocytes after 24 h of the exposures by laser scanning confocal microscopy. The effect of 1-Hep on the expression of F-actin was also explored. RESULTS:Compared with control group, the fluorescence intensities in KCl group and KCl+SKA group were increased, and highly increased in KCl+SKA group. The F-actin filaments in the above 2 groups were more intensive, thickened and concentrated than those in control group, and more obvious in KCl+SKA group. l-Hep significantly decreased the expression of F-actin in KCl group and KCl+SKA group as compared with control group, and parts of the filamentous fracture were seen in the astrocytes in all 1-Hep-treated groups, in which some of the filamentous lines were crosscut. CONCLUSION:Increase in the expression of F-actin in the astrocytes affects the structure and function of the intercellular gap junctions, which may be involved in the mechanism of SKA-induced epilepsy. 相似文献