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Ryerson WN 《Science (New York, N.Y.)》2011,331(6022):1265; author reply 1265
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M D Dibner 《Science (New York, N.Y.)》1985,229(4719):1230-1235
The products of biotechnology are being developed for new diagnostics and therapeutics, and it is predicted that they will have great impact on the pharmaceutical industry. In the United States, pharmaceutical companies are incorporating biotechnology into their research and development programs, often with the contractual assistance of small biotechnology firms. Their strongest competition is arising in Japan, where there are now concerted government and industry efforts to expand biotechnology capabilities and to optimize commercialization. Strategies used by the United States and Japan to incorporate biotechnology into their pharmaceutical industries are examined and compared.  相似文献   

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Consistent behavior patterns are created by variable acts, and generally repeat only because detailed acts change. The accepted explanation of this paradox, that "cues" cause the changes, is irrelevant; it is unsupported by evidence, and incapable of dealing with novel situations. The apparent purposefulness of variations of behavioral acts can be accepted as fact in the framework of a control-system model of behavior. A control system, properly organized for its environment, will produce whatever output is required in order to achieve a constant sensed result, even in the presence of unpredictable disturbances. A control-system model of the brain provides a physical explanation for the existence of goals or purposes, and shows that behavior is the control of input, not output. A systematic investigation of controlled quantities can reveal an organism's structure of control systems. The structure is hierarchical, in that some quantities are controlled as the means for controlling higher-order quantities. The output of a higher-order system is not a muscle force, but a reference level (variable) for a lower-order controlled quantity. The highest-order reference levels are inherited and are associated with the meta-behavior termed reorganization. When controlled quantities are discovered, the related stimulus-response laws become trivially predictable. Variability of behavior all but disappears once controlled quantities are known. Behavior itself is seen in terms of this model to be self-determined in a specific and highly significant sense that calls into serious doubt the ultimate feasibility of operant conditioning of human beings by other human beings.  相似文献   

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我国茶叶氟含量状况研究   总被引:10,自引:0,他引:10  
测定了2000—2001年我国主要产茶省份的262家单位的绿茶、红茶、乌龙茶、花茶和黑茶共计577只茶样的水溶性氟含量,结果表明,不同茶类水溶性氟含量不同,以绿茶最低,平均含量为67.53±69.49μg·g-1;黑茶最高,平均含量为296.14±246.07μg·g-1;红茶类、乌龙茶类及花茶类含量居中,分别为177.01±121.49μg·g-1、167.68±112.28μg·g-1和140.97±150.51μg·g-1。名优茶水溶性氟含量比大宗茶低。茶园附近的环境条件对茶叶氟含量有较大影响。茶叶中氟的浸出率随着冲泡时间的延长和水温的增加而增加,一般在45min和90℃时趋于稳定。  相似文献   

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Noninvasive molecular-imaging technologies are providing researchers with exciting new opportunities to study small-animal models of human disease. With continued improvements in instrumentation, identification of better imaging targets by genome-based approaches, and design of better imaging probes by innovative chemistry, these technologies promise to play increasingly important roles in disease diagnosis and therapy.  相似文献   

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China's grain yield increased from 1 t ha~(–1) in 1961 to 6 t ha~(–1) in 2015, while successfully feeding not only its large population but also supplying agricultural products all over the world. These achievements were greatly supported by modern technology and distinct governmental policy. However, China's grain production has been causing a number of problems mainly related to declining natural resources and a lack of environmental protection. Due to the growing population and changing dietary requirements, increasing food production must be achieved by increasing resource use efficiency while minimizing environmental costs. We propose two novel development pathways that can potentially sustain agricultural crop production in the next few decades:(i) enhancing nutrient use efficiency with zero increase in chemical fertilizer input until 2020 and(ii) concurrently increasing grain yield and nutrient use efficiency for sustainable intensification with integrated nutrient management after 2020. This paper provides a perspective on further agricultural developments and challenges, and useful knowledge of our valuable experiences for other developing countries.  相似文献   

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赤泥中氟的迁移规律   总被引:1,自引:0,他引:1  
袁霄梅  王冰莹  熊飞 《安徽农业科学》2011,39(27):16724-16726,16771
结合某赤泥堆放场的水文地质条件,通过模拟试验,探讨了赤泥及冲灰水中氟化物进入地下水的运移规律。结果表明,赤泥堆场在大气降水和冲灰水的浸溶、淋溶作用下,氟化物会大量溶出,并随赤泥废液一起下渗,新鲜赤泥及石灰岩碎石对氟化物有一定的吸附作用,但吸附能力有限。  相似文献   

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家禽氟中毒的原因及防治   总被引:1,自引:0,他引:1  
<正>氟已被证实是动物必需的微量元素,适量的氟具有促进动物生长、发育、繁殖,参与骨骼代谢、防龋齿、影响动物造血功能及神经兴奋性和传导的作用,但过量摄入会引起畜禽中毒。近年来,家禽氟中毒呈上升趋势。本文就家禽氟中毒的原因、机理、症状、病理变化及如何防治  相似文献   

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酸性土壤有效氟提取方法的研究   总被引:5,自引:2,他引:5  
采用F-选择电极法,对福建省酸性土壤有效F的提取方法进行了研究。3种浸提剂(去离子水、0.01 mol.L-1 CaCl2和0.01mol.L-1 HCl)中,只有去离子水提取的土壤有效F与茶叶含氟量呈显著正相关(r=0.392*,n=38)。对去离子水提取条件的研究表明,随液土比的升高,F提取总量升高,在适当提高F提取量又保证测定精度的前提下,将水提取有效F的液土比定为10∶1;振荡速度对F提取量有轻微影响,将振荡速度定为180 r.min-1;振荡时间从30 min增加到60 min,F提取量有所增加,随振荡时间的继续增加,F提取量反而降低,因而将振荡时间定为60 min;F提取量随浸提温度的升高而增加,为了使测定结果符合一般田间情况,将浸提温度定为25℃。  相似文献   

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