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排序方式: 共有65条查询结果,搜索用时 31 毫秒
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通过分析全国12个城市2014年春季(3~5月)PM2.5监测数据,得出不同地区春季PM2.5分布特征,及不同地区PM2.5主要来源;比较六大经济协作区、不同功能城市及几个典型城市间PM2.5分布的差异,并分析其原因,为制定改善空气质量的有效措施提供合理依据。 相似文献
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Alex Beharav Dalia Lewinsohn Aleš Lebeda Eviatar Nevo 《Genetic Resources and Crop Evolution》2006,53(3):467-474
A total of 1027 genotypes of wild Lactuca spp. (L. serriola, L. saligna, and L. aculeata), originating from Israel, Jordan, East Turkey, Armenia, Kazakhstan, China, and various other countries in Europe were screened
for resistance to the lettuce downy mildew (Bremia lactucae Regel). The genotypes of L. serriola (N = 962); L. saligna (N = 43); and L. aculeata (N = 22) were tested at the seedling stage with two isolates of B. lactucae (race Bl-21 and Isr-74) isolated from cultivated lettuce in Italy and Israel, respectively. Altogether, the isolates possess
virulence against 17 out of 20 Dm genes/R-factors composing the established differential set of lettuce lines/varieties. They could therefore be used for preliminary
detection of the presence of new resistance factors. A total of 83 and three genotypes of L. serriola and L. saligna, respectively, were resistant to infection by each of the two isolates alone as well as to the infection by a mix of the
two isolates. These genotypes probably carry previously unknown resistance, and therefore could be suitable for exploitation
by breeders and further detailed research. The wild progenitor of lettuce, L. serriola, and related species harbor significant untapped genetic resources for lettuce improvement. 相似文献
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Yvonne Lokko Alfred Dixon Sam Offei Eric Danquah Martin Fregene 《Genetic Resources and Crop Evolution》2006,53(7):1441-1453
A study was conducted to determine the extent of genetic diversity among African cassava (Manihot esculenta Crantz) accessions resistant to the cassava mosaic virus disease (CMD), using simple sequence repeat (SSR) markers. The accessions
included a breeding stock (clone 58308), five improved lines, 62 CMD resistant and 10 CMD susceptible landraces. Genetic diversity
was assessed among accessions in five cluster groups derived from UPGMA analysis on data from 18 SSR primer pairs. Average
gene diversity, He, was high in all cluster groups, with an average heterozygosity of 0.591 ± 0.061. The estimator of inbreeding
Fis revealed a low level of inbreeding within groups and averaged −0.262 ± 0.142. Gene diversity among all accessions was
51.4% and gene diversity within cluster groups was 46.6%, while 4.8% was due to diversity between the different cluster groups.
The amount of genetic differentiation measured by Gst and Fst were 9.6% and 12.1% respectively, indicating a weak genetic
structure. 相似文献
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[目的]研究台山地区土壤富硒来源,为资源开发利用提供重要科学依据。[方法]从成土母质和大气沉降上,对比分析了硒的含量。[结果]源岩中,上寒武系地层含硒量高,可达1.34 mg/kg;大气干沉降物中,硒年通量平均达285.18μg/(m2.年)。[结论]上寒武统水石组为该区的主要物质来源,而大气沉降为提供丰富物质补充。 相似文献
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Determination of the C balance is of considerable importance when forecasting climate and environmental changes. Soil respiration
and biological productivity of ecosystems (net primary production; NPP) are the basic components of the terrestrial C cycle.
In this study, a previously made assessment of the annual CO2 flux from Russian soils was improved upon. CO2 emissions from Russian soils during the growing period were shown to represent, on average, 53–82% of the annual CO2 flux from Russian soils. The total annual CO2 flux from Russian soils was estimated at 4.50 Gt C (C source). The NPP of Russian ecosystems was estimated at 4.81 Gt C year–1 (C sink). Our calculations showed values of CO2 emissions and the C sink to be very close. This shows that, in general, terrestrial ecosystems are under steady state.
Received: 1 December 1997 相似文献
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我国农业面源污染对水体的影响及防治措施 总被引:24,自引:0,他引:24
通过分析中国化肥用量的变化与湖泊富营养化进程,揭示了农业面源污染的增加与水体污染的加重几乎同步,农业面源是造成水环境污染的重要因素。从农业面源污染负荷大、污染复杂和防治难度大三方面指出中国农业面源防治的艰巨性和长期性。最后提出建立防治农业面源污染的政策和法规、推广先进的科学技术和加强生态建设是防治中国农业面源对水体污染的重要措施。 相似文献
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综述了原花青素的来源、功能特性及其在食品、医药、化妆品领域的应用,并指出了原花青素生产中需要解决的问题,为原花青素的开发和应用提供了参考。 相似文献