Updated version of @Alaaedeen's answer. You can specify any part of the version of any package you want to install. This may cause other package versions to change. For example, if you don't care about which specific version of PyQt4 you want, do:
conda install pyqt=4
This would install the latest minor version and release of PyQt 4. You can specify any portion of the version that you want, not just the major number. So, for example
conda install pyqt=4.11
would install the latest (or last) release of version 4.11.
Keep in mind that installing a different version of a package may cause the other packages that depend on it to be rolled forward or back to where they support the version you want.
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