The pulmonary development is extremely complex and highly ordered, a process involving several cell types, which are involved in different phases of development, beginning in the embryonic phase until the differentiation and specialization of cells forming specialized organs. The development of respiratory system (larynx, trachea, bronchi and lungs) begins in the fourth week of embryonic development, and remains incomplete until the last weeks of fetal development, becoming mature just before the birth.
The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information.
Last date updated on July, 2014