barriers

n.

a structure or object that impedes free movement

any condition that makes it difficult to make progress or to achieve an objective

"intolerance is a barrier to understanding"

同义词：roadblock

anything serving to maintain separation by obstructing vision or access

Barriers to New Competition
Barriers to New Competition
Knocking down barriers: advances in siRNA delivery.
Interpretive Barriers to Successful Product Innovation in Large Firms
Interpretive Barriers to Successful Product Innovation in Large Firms
Business Model Innovation: Opportunities and Barriers
Combat duty in Iraq and Afghanistan, mental health problems, and barriers to care.
Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers
Mind the Gap: Why do people act environmentally and what are the barriers to pro-environmental behavior?
ChemInform Abstract: CONFORMATIONAL ANALYSIS. 125. THE IMPORTANCE OF TWOFOLD BARRIERS IN SATURATED D MOLECULES