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331.
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【目的】了解广东省水稻秸秆露天焚烧大气污染物排放情况,为水稻秸秆的资源化利用以及大气污染治理提供一定的参考。【方法】基于广东省历年的稻谷产量、草谷比、水稻秸秆焚烧比例和焚烧效率指标,利用排放因子法估算了1990—2016年间广东省水稻秸秆产量及露天焚烧大气污染物的排放量,利用ArcGIS10.2软件分析了大气污染物排放的时空分布特征。【结果】1990—2016年间,广东省水稻秸秆资源量呈"下降-上升-下降-上升"的变化趋势,整体上由1990年的1 687万t下降到2016年的1 087万t,年平均减少率为1.7%。研究期间,PM、BC、OC、SO_2、NO_x、CH_4、CO和CO_2的排放量分别减少了8 800、200、5 200、1 100、800、2 900、106 500和2 585 800 t,减少率分别为48.09%、50.00%、48.60%、50.00%、50.00%、48.33%、48.45%和48.45%。广东省各地区水稻秸秆露天焚烧污染物排放量的空间分布表现出不均衡性,1990年,茂名、阳江、肇庆、广州、惠州、河源、汕尾、揭阳及潮州市的排放量较大,PM的排放总量均在1 000 t以上;2000年,大部分地市的PM排放量均在1 000 t以上;2010—2016年间,除揭阳市外,PM的排放量均低于1 000 t。【结论】1990—2000年,除粤北的部分县(市、区)外,广东省大部分地区的大气污染物排放强度均较高;2010年前,大气污染物排放的高值区主要集中在湛江、茂名、阳江、肇庆、梅州、惠州、揭阳以及潮州市;2016年,排放强度高的地区仅集中在粤西和粤东地区的小部分县(市、区)。 相似文献
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334.
比较了炼山全垦、全垦和直接挖穴造林等3种造林方式对红壤养分状况和土壤流失量变化的影响.结果表明,炼山和全垦造林将明显增强土壤和养分的流失,导致土壤有机质、氮、磷、钾等养分的减少和土壤肥力质量的下降. 相似文献
335.
Many studies have been conducted in examining the effects of N fertilizers on cereal yields and nitrogen (N) uptake, the effects of different kind of crop residues and their management practices on cereal yield, nitrogen uptake and simple N balance have not been studied extensively. We studied the effects of antecedent leguminous (white clover and field pea) and non-leguminous (perennial ryegrass and winter wheat) crop residues, each subjected to four different residue management practices (ploughed, rotary hoed, mulched and burned) on grain yield, nitrogen uptake by succeeding winter wheat crops, soil N mineralization and simple N balance. Grain yield and N uptake by the first wheat crop were significantly higher under leguminous than non-leguminous residues, following the order of white clover>pea>ryegrass>wheat. Grain yield under the mulched treatment was significantly lower than those of other management treatments due to lower plant population established. While N uptake was significantly lower under rotary hoed and mulched treatments as compared to other treatments, mulching had a positive residual effect on the grain yield of second wheat crop. Similar to grain yield, total soil N mineralization was greater under leguminous residues during the growing period of first wheat crop and was significantly correlated with C/N ratio of the residues. The calculated simple N balance showed that positive N balances occurred under white clover after one wheat crop when N inputs from only crop residue tops was considered. This also occurred even after two wheat crops when total N inputs from crop residues (tops+roots) were considered. However, with pea, the positive N balance occurred only after the first wheat crop when total N input from crop residues (tops+roots) were considered. These calculations demonstrated the important contribution of root-N to the N economy of the cropping system, which was largely ignored in most studies. The burning of residues showed no significant advantage over other residue management treatments. This was also evident from N balance calculations, which showed, in general, N balance was lower or more negative under residue-burned treatment as compared with other treatments. Overall, present results showed that it is beneficial to retain crop residues in the field, even though non-leguminous residues may cause substantial soil N immobilization initially reducing N availability to the first wheat crop, this N eventually became available to subsequent wheat crops and also increase the fertility of soils in the long-term. Thus, N inputs from crop residues are far more beneficial to the cropping system as compared to the burning of crop residues in the field or their removal from the field. 相似文献
336.