Generally, SCI and SCIE journals are considered to have a similar level of quality. However, in some countries, like for example in Korea (I think in China and Japan as well), SCI journals are given more weight (or perceived to have higher quality) than SCIE journals. Perhaps, it is also because a lot of SCI journals have longer history than SCIE journals. As what I have noticed, many of the top-ranked journals in their respective fields are SCI journals, and only a few SCIE journals. And many of the Society-sponsored journals are SCIE. So the 'perception' of quality is relative to where you are located.
According to Thomson Reuters, SCIE is the expanded version of SCI. One can understand if a journal is indexed by SCI, then normally it is available in SCIE as well
Generally, SCI and SCIE journals are considered to have a similar level of quality. However, in some countries, like for example in Korea (I think in China and Japan as well), SCI journals are given more weight (or perceived to have higher quality) than SCIE journals. Perhaps, it is also because a lot of SCI journals have longer history than SCIE journals. As what I have noticed, many of the top-ranked journals in their respective fields are SCI journals, and only a few SCIE journals. And many of the Society-sponsored journals are SCIE. So the 'perception' of quality is relative to where you are located.
SCIE journals are the expanded and extended list of SCI journals. In future some more good journals will be included in SCIE based on the quality. SCI or SCIE journals and the published papers are of same quality as for as its quality and recognition are concerned. In civil engineering field many journals listed in SCIE are of very high quality and publishing papers is these journals is very difficult. Once published, you have really achieved something impossible. Publish few papers in SCI or SCIE to have international recognition.
To Answer Prakash Kumar Singh: There is nothing like paid SCI journals. Once you pay and publish, you have compromised the quality. Any paper can be published if one is ready to pay. Avoid pay and publish concept to have more credibility of your paper. I have seen few good papers in paid journals as well. Some times you may have to publish in other journals, if your paper is not of high quality. Good wishes.
SCI is not covering many journals of engineering discipline. Now a days good civil engineering journals are listed in SCIE. I agree with Mr. Hui Yai that SCI is better if journals cover your area. Good wishes.
In my field of study, coastal science and engineering, there are only about 40% good journals in SCI and the other 60% in SCIE. So the difference between SCI and SCIE is not in quality. As the letter from Thomson Reuters, the difference lies in storage media.
All the Journals listed in SCI are in SCIE, however the reverse is not the same. This is irrespective of the quality of journals. Yes I agree that older journals are in SCI and newer ones are in SCIE due to space constrain.
The Science Citation Index (SCI) is a sub-set of the Science Citation Index Expanded (SCIE), containing journals that rank competitively among the most highly-cited core journals in their category or categories. The Science Citation Index Expanded is essentially the web version of what used to be a database available only on CDRom/Diskette. When selecting the journals for the Science Citation Index we choose the top journals from each subject category and supplement this with top regional journals from each category to give broad geographic and multidisciplinary coverage. The evaluation of and acceptance of a journal for the Science Citation Index Expanded or the Science Citation Index is essentially the same with one major difference. While every science journal in our database is covered in the Science Citation Index Expanded and only those journals of relatively significantly higher citation impact are selected for the Science Citation Index. In other words, Science Citation Index covers only the most highly cited, highest impact journals in each category. This is because of the constraints of the CDROM and print media there is no difference in the selection process for Science Citation Index and Science Citation Index Expanded journals.