如何拆分R中的特定段落？

Question

我想从一篇长文中提取特定的段落。例如：

txt1 <- "What is claimed is:
1. A hybridized CMP conditioner, comprising: a base; 
a first abrasive unit, provided on said base and comprising a first
bonding layer fixed on said base, a substrate for abrasive unit provided     
on said first bonding layer and an abrasive layer provided on said 
substrate for abrasive unit, said abrasive layer being a diamond coating 
formed through a chemical vapor deposition process, and said diamond 
coating being provided on the surface thereof with a plurality of abrasive     
tips. 
2.  The hybridized CMP conditioner according to claim 1, wherein said base
is provided on the surface thereof with a central region and an annular     
outer region around the outside of said central region. 
3.  The hybridized CMP conditioner according to claim 2, wherein said
central region is provided with a recessed portion for said first abrasive
unit to be provided therein, and said annular outer region is provided 
with a plurality of first accommodating portions spaced apart from each 
other for said second abrasive units to be provided therein. "

我只想摘录第一段。如下所示：

1. A hybridized CMP conditioner, comprising: a base; 
a first abrasive unit, provided on said base and comprising a first
bonding layer fixed on said base, a substrate for abrasive unit provided     
on said first bonding layer and an abrasive layer provided on said 
substrate for abrasive unit, said abrasive layer being a diamond coating 
formed through a chemical vapor deposition process, and said diamond 
coating being provided on the surface thereof with a plurality of abrasive     
tips. 

我已经尝试使用strsplit函数来做

strsplit(txt1, "\n1.", perl = TRUE)

但结果并不是我想要的。

[1] "What is claimed is:"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

[2] " A hybridized CMP conditioner, comprising: a base; \na first abrasive 
unit, provided on said base and comprising a first bonding layer fixed on 
said base, a substrate for abrasive unit provided on said first bonding 
layer and an abrasive layer provided on said substrate for abrasive unit, 
said abrasive layer being a diamond coating formed through a chemical 
vapor deposition process, and said diamond coating being provided on the 
surface thereof with a plurality of abrasive tips; and \na plurality of 
second abrasive units, provided on said base and comprising a second 
bonding layer fixed on said base, a carrying post provided on said second 
bonding layer, an abrasive particle provided on said carrying post and an 
abrasive material-bonding layer provided between said carrying post and 
said abrasive particle. \n2.  The hybridized CMP conditioner according to 
claim 1, wherein said base is provided on the surface thereof with a 
central region and an annular outer region around the outside of said 
central region. "

Answer 1

使用strsplit

 # split at newline followed by number and '.'
paragraphs <- unlist(strsplit(txt1, "\\n(?=(\\d+\\. ))", perl = TRUE))
 # get rid of newlines and select 1st paragraph
gsub(" *\\n", " ", paragraphs)[2]