if you want to get all dataset, you can use
xxxxxxx/api/v3/datasets
this gives you a paged, with start page, next page, end page link info at the bottom of json.
you can follow those link to get next page, any page, or end page.
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Here is some my note:
// 2 record, of sample
https://hub.arcgis.com/data.json
// first 10 record, with first, next, last page link, page[number]=180756&page[size]=10
https://hub.arcgis.com/api/v3/datasets
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domain/data.json get first 1000 record, but, (so far only 867) get dataset-id,
https://geohub.lacity.org/data.json
/{id} get details of this-id
https://geohub.lacity.org/api/v2/datasets/4576606b612542ebafff232ee4609d3d_29
get first 10 datasets, with next page, lasts page, total page,
https://geohub.lacity.org/api/v3/datasets
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http://data-ral.opendata.arcgis.com/data.json
https://opendata.arcgis.com/api/v2/datasets?filter[source]=City%20of%20Raleigh