Сборник тезисов находится на сайте.

Because тезисов is in the genitive plural.

The base form is тезисы = theses / abstracts / summary points.
In сборник тезисов, Russian uses a very common pattern:

• сборник = collection, compilation
• тезисов = of theses / of abstracts

So the literal structure is a collection of abstracts. English often uses of for this idea, while Russian usually shows it by changing the noun’s ending instead of adding a separate word.

Сборник means a collection, compilation, or volume containing gathered materials.

It is often used for things like:

• сборник рассказов = a collection of stories
• сборник задач = a problem book / collection of exercises
• сборник статей = a collection of articles

So сборник тезисов is something like a collection of abstracts or booklet of theses/abstracts, depending on context.

Because находится emphasizes location: is located / is situated / can be found.

• Сборник тезисов находится на сайте = The collection of abstracts is on the website / can be found on the website.

Russian often avoids using есть in simple present-tense statements of identity or existence when English would use is. If you want to say where something is located, находиться is very natural.

Compare:

• Книга на столе. = The book is on the table.
• Книга находится на столе. = The book is located on the table.
  This sounds a bit more formal or explicit.

So here находится gives a slightly formal, informational tone.

Because the preposition на here means on, and after на in this meaning of location, Russian uses the prepositional case.

• сайт = website, site
• на сайте = on the website

This is a standard pattern:

• на столе = on the table
• на странице = on the page
• на сайте = on the website

So сайте is the prepositional singular form of сайт.

Yes. The best translation depends on context.

Possible translations include:

• The collection of abstracts is on the website.
• The book of abstracts is on the website.
• The collection of theses is on the website.
• The abstracts booklet is available on the website.
• The collection of abstracts can be found on the website.

The tricky word is тезисы. In academic Russian, it often means conference abstracts or summary theses, not necessarily philosophical theses in the English sense. So abstracts is often the most natural translation.

Yes, Russian word order is fairly flexible, although different orders can change emphasis.

Neutral order:

• Сборник тезисов находится на сайте.

This presents the topic first and then says where it is.

Other possible orders:

• На сайте находится сборник тезисов.
  = On the website there is a collection of abstracts.
  This puts more focus on the location first.

• На сайте сборник тезисов.
  Possible in some contexts, but less complete and less formal than the original.

So the original sentence sounds natural and neutral, especially in formal written language.

Russian does not have articles like a or the.

So Сборник тезисов находится на сайте can mean:

• The collection of abstracts is on the website
• A collection of abstracts is on the website

Which one is correct depends on context. In most real situations, context makes it clear whether the noun is definite or indefinite.

English speakers often look for an article, but Russian simply does not mark this grammatically.

Сборник is in the nominative singular because it is the grammatical subject of the sentence.

The sentence structure is:

• Сборник тезисов = subject
• находится = verb
• на сайте = location phrase

So:

• сборник = nominative singular
• тезисов = genitive plural
• сайте = prepositional singular

A rough pronunciation guide is:

SBOR-neek TYE-zee-saf na-HO-deet-sya na SY-te

A few notes:

• сборник starts with a consonant cluster, roughly sbor-
• тезисов is pronounced with stress on the first syllable: ТЕзисов
• находится has stress on хо: нахОдится
• сайте has stress on сай: сАйте

A more careful approximation:

СБОР-ник ТЕ-зи-сов на-ХО-дит-ца на САЙ-те

The -тся in находится is pronounced roughly like -ца.

It is somewhat more formal or official than simply leaving the verb out or using a shorter everyday phrasing.

Compare:

• Сборник тезисов на сайте.
  Short, headline-like, less complete.

• Сборник тезисов есть на сайте.
  Usually less natural here.

• Сборник тезисов находится на сайте.
  Clear, formal, standard informational style.

This makes it very suitable for announcements, academic contexts, and official websites.

No, not in standard Russian for this meaning.

Russian normally says:

• на сайте = on the website

Even though English learners may think of information as being in a website, Russian treats it as on the website.

So:

• на сайте = correct
• в сайте = generally incorrect here

This is something you mainly need to memorize.

The dictionary forms are:

• сборник → сборник
• тезисов → тезис
• находится → находиться
• на → на
• сайте → сайт

So literally, the sentence is built from:

• сборник = collection
• тезис = thesis / abstract / summary point
• находиться = to be located
• на = on
• сайт = website

You would change the verb находиться.

Present:

• Сборник тезисов находится на сайте.
  = The collection of abstracts is on the website.

Past:

• Сборник тезисов находился на сайте.
  = The collection of abstracts was on the website.

Future:

• Сборник тезисов будет находиться на сайте.
  = The collection of abstracts will be on the website.

In everyday speech, people might also choose simpler wording depending on context, but these forms are grammatically correct and natural.