人造元素

关于化学元素的学说,构成了化学的基本内容,我们周围世界中所有的复杂物质就是由这些元素组成的。在长时期内,人们一直认为元素是不可改变的,并且没有共同的联系。直到1869年,门捷列也夫才发现了所有化学元素的普遍规律性,并且在这个基础上创立了著名的周期系。这位伟大的俄罗斯学者的科学成就,标志着化学上新纪元的开始。门捷列也夫的发现的重要意义是:他确定了所有元素的化学性质随着它们原子量的增加的有规律的周期的重覆性。门捷列也夫把性质相似的元素一个个地上下对齐,这样就组成了周期表。他证明了,每一种化学元素的原子都有着一定的形态,这种形态的特徵不仅仅是由原     

人类的起源图解

达尔文和恩格斯关于人类起源的解释世纪以来,学者不断地积累了有关生命界的知识,这些知识打开了人类起源的秘密。在这些学者中,最卓越的便是达尔文和恩格斯。 19世纪中叶,达尔文在材料积累和研究的基础上,令人信服地指出了:地球上的生命发生於几亿年以前;高等生物是由低等生物演化而来的:猿是人类最接近的祖先, 但是达尔文终究不能揭露出从动物演变成人的原因:这个伟大的任务被马克思主义的奠基人之一——恩格斯完成了。他指出,是劳动创造了人。在自然界和社会上都存在着两种不可调和的观点:宗教唯心和科学唯物的。宗教说,世界上的一切,包括人类及其社会,都是被上帝创造的,是永远不变的。建立在科学事实和实践基础上的唯物主义却证明了,自然界和社会不是也不可能没有改变的,任何事物都是在走向死亡和毁灭,而新的则开始萌芽、生长和发展。关于人类起源的科学尤其确凿地证明了这个真理。     

海军的新型声纳会伤害鲸鱼吗

经过多年的争论，国家海洋渔业机构于去年夏天批准美国海军使用新型低频声纳系统查找敌方潜艇的位置。这一许可促使自然资源保护委员会和一个由其他环境组织组成的联盟向联邦法院控告海军，称这种声纳将对海洋生命造成巨大的危害。     

模拟碳的地球化学循环

引起大气二氧化碳缓慢增加的自然界地球化学过程，通过温室效应很可能引起了过去全球变暖的一些地质时期的出现。     

等离子体粒子加速器

等离子体中产生的电场能够使电子加速以获得高能。这个方法可望使场强比能量最大的传统加速器的场强高出10，000倍。     

新疆西准噶尔地区塔斯特岩体锆石LA-ICPMS年龄及其意义

西准噶尔萨吾尔地区地处新疆阿勒泰地区吉木乃县及塔城地区和丰县。酸性侵入岩在区内较发育，其研究对于准噶尔地区后碰撞构造一岩浆演化时限的厘定具有重要的意义。塔斯特岩体是萨吾尔地区重要的复式花岗岩体，与区内铜、金矿化关系密切。塔斯特岩体锆石LA-ICPMS年龄为337±4Ma（1δ），形成于早石炭世。结合已有的地球化学特征研究，这一年龄显示西准噶尔地区在早石炭世已处于后碰撞环境。本文获得的塔斯特岩体成岩年龄是目前在准噶尔地区获得的最老的后碰撞花岗岩锆石U-Pb年龄之一，为准噶尔地区后碰撞构造-岩浆演化时限的厘定提供了新的证据。     

太阳能电池

可弯曲的轻质太阳能电池展开竞争     

The information requirements and information-seeking behaviours of health and social care professionals providing care to children with health care needs: a pilot study

OBJECTIVES: The objectives of this work were to identify the sources of information currently received, information-seeking behaviours, information requirements and preferences for future information provision amongst health and social care professionals providing care to children with health care needs. METHODS: Data were collected using a cross-sectional postal questionnaire survey. RESULTS: A wide range of information resources was reported as being available to professionals. However, a large proportion of respondents found it necessary to perform additional searches for information, suggesting that current resources were not satisfying their needs. The majority of professionals reported a preference for electronic formats, whilst a smaller proportion preferred hard copy materials. Participants promoted the use of informal networks as a means of support and exchange of information. CONCLUSION: Supplementing the information that is provided in electronic and hard copy formats, by enhancing informal networks, may be the most effective way of meeting the information needs of this group of professionals.     

User library service expectations in health science vs. other settings: a LibQUAL+ Study

Objectives: To explore how the library service expectations and perceptions of users might differ across health‐related libraries as against major research libraries not operating in a medical context; to determine whether users of medical libraries demand better library service quality, because the inability of users to access needed literature promptly may lead to a patient who cannot be properly diagnosed, or a diagnosis that cannot be properly treated. Methodology: We compared LibQUAL+® total and subscale scores across three groups of US, Canadian and British libraries for this purpose. Results: Anticipated differences in expectations for health as other library settings did not emerge. Conclusions: The expectations and perceptions are similar across different types of health science library settings, hospital and academic, and across other general research libraries.