THE WORK OF THE ELECTRICAL DIVISION OF THE BUREAU OF STANDARDS     

Rosa EB 《Science (New York, N.Y.)》1912,35(888):8-19

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Global and local conservation priorities     

Mittermeier RA  Gascon C  Rajaobelina L  Supriatna J  Cardoso da Silva JM  Rodríguez CM  Zhi L  Brandon K 《Science (New York, N.Y.)》2007,318(5855):1377-82; author reply 1377-83

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The impact of agricultural soil erosion on the global carbon cycle   总被引：4，自引：0，他引：4  

Van Oost K  Quine TA  Govers G  De Gryze S  Six J  Harden JW  Ritchie JC  McCarty GW  Heckrath G  Kosmas C  Giraldez JV  da Silva JR  Merckx R 《Science (New York, N.Y.)》2007,318(5850):626-629

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year(-1) to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year(-1) resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.  相似文献   

紧凑型玉米高产栽培理论与技术研究   总被引：19，自引：0，他引：19  

赵致  张荣达  吴盛黎  宋碧  张帮琨  江龙  王嵩  胡建风 《中国农业科学》2001,34(5):537-543

 采用裂区和正交旋转组合设计方法 ,研究了紧凑型玉米登海 6号的产量及产量结构、群体主要质量生理指标、田间小气候指标、高产栽培技术方案等。获得了登海 6号间套作种植条件下 ,产量在 12 996～ 13 2 2 7kg/ ha时的高产栽培理论参数和多套技术方案。大面积高产试验结果表明 :紧凑型玉米杂交种登海 6号有较大的增产潜力 ,两年13 .85 ha平均产量达到 12 5 10 kg/ ha,其中 75 4 .7m2产量高达 15 4 77kg/ ha。黔西北山区玉米生育期间的气候生态条件能满足高产的需要  相似文献   

Effectiveness of parks in protecting tropical biodiversity   总被引：2，自引：0，他引：2  

Bruner AG  Gullison RE  Rice RE  da Fonseca GA 《Science (New York, N.Y.)》2001,291(5501):125-128

We assessed the impacts of anthropogenic threats on 93 protected areas in 22 tropical countries to test the hypothesis that parks are an effective means to protect tropical biodiversity. We found that the majority of parks are successful at stopping land clearing, and to a lesser degree effective at mitigating logging, hunting, fire, and grazing. Park effectiveness correlates with basic management activities such as enforcement, boundary demarcation, and direct compensation to local communities, suggesting that even modest increases in funding would directly increase the ability of parks to protect tropical biodiversity.  相似文献   

THE NATIONAL BUREAU OF STANDARDS AND ITS RELATION TO SCIENTIFIC AND TECHNICAL LABORATORIES     

Rosa EB 《Science (New York, N.Y.)》1905,21(527):161-174

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和谐社会视野中大学生思想政治教育的新思考     

赵捷  陈宜大  叶飞霞 《福建农业大学学报(哲学社会科学版)》2006,9(1):68-71

加强大学生思想政治教育，促进大学生德智体美劳全面和谐发展，在构建社会主义和谐社会中起着基础性作用。按照建设社会主义和谐社会的要求，针对高校思想政治教育对象多元化、思想认识多元化、价值取向多元化、信息来源多元化以及择业去向多元化，大学生的思想道德素质水平呈现层次性和差异性的状况，在大学生思想政治教育的培养目标、工作原则、方法途径、内容体系、评价体系提出新的要求。  相似文献   

犬细小病毒分离株VP2基因的克隆与序列分析   总被引：10，自引：0，他引：10  

杨玲  徐向明  殷俊  宗卫峰  陈璐  李厚达 《扬州大学学报(农业与生命科学版)》2002,23(3):12-14

以犬细小病毒 (Canine parvovirus,CPV)扬州分离株病毒的 DNA为模板 ,根据基因库 CPV-d序列设计合成了VP2基因的 1对特异引物 ,进行聚合酶链式反应 ,扩增出约 1 .7kb的片段 ,按常规方法克隆进 p UC1 8载体 ,经 Eco R 和Sal 双酶切筛选到阳性质粒 ,进一步对该片段进行序列分析。结果表明 :所扩增基因片段长度为 1 740 bp,与美国参考株 CPV-d (type 2 )、CPV-1 5 (type 2 a)、CPV-3 9(type 2 b)相比较 ,核苷酸同源性分别高达 99.5 %、99.7%、99.7%。  相似文献   

Evolution. Climb every mountain?     

Elena SF  Sanjuán R 《Science (New York, N.Y.)》2003,302(5653):2074-2075

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The coevolution of cultural groups and ingroup favoritism     

Efferson C  Lalive R  Fehr E 《Science (New York, N.Y.)》2008,321(5897):1844-1849

Cultural boundaries have often been the basis for discrimination, nationalism, religious wars, and genocide. Little is known, however, about how cultural groups form or the evolutionary forces behind group affiliation and ingroup favoritism. Hence, we examine these forces experimentally and show that arbitrary symbolic markers, though initially meaningless, evolve to play a key role in cultural group formation and ingroup favoritism because they enable a population of heterogeneous individuals to solve important coordination problems. This process requires that individuals differ in some critical but unobservable way and that their markers be freely and flexibly chosen. If these conditions are met, markers become accurate predictors of behavior. The resulting social environment includes strong incentives to bias interactions toward others with the same marker, and subjects accordingly show strong ingroup favoritism. When markers do not acquire meaning as accurate predictors of behavior, players show a markedly reduced taste for ingroup favoritism. Our results support the prominent evolutionary hypothesis that cultural processes can reshape the selective pressures facing individuals and so favor the evolution of behavioral traits not previously advantaged.  相似文献