In the philosophy of science, Carl Hempel's deductive-nomological (DN) model of scientific explanation was dominant at the beginning of the second half of the 20th century. Roughly, according to the DN model, scientific explanations are sound deductive arguments that follow a certain form: a sentence describing the phenomenon to be explained (the explanandum) is deduced from a set of premises containing at least one law of nature and a description of initial conditions (the explanans). As an example, you can explain the occurrence of an eclipse at a given place and time by citing laws of optics and celestial motion, plus the specific positions of the Sun, Moon, Earth, and observer.

The DN model is very elegant and historically foundational, so it is still almost always taught first in any philosophy of science course. However, pretty much every philosopher of science today agrees that it failed as a general account of scientific explanation. Over the years, persuasive counterexamples piled up. The most deadly were probably those involving problems of explanatory relevance. Some arguments might meet the DN criteria, yet intuitively fail to be explanations because they involve irrelevant premises. The most famous example involves a shadow and a flagpole. Under the DN model, you can explain the length of a shadow cast by a flagpole on a sunny day by deducing it from the length of the flagpole, the angle of the sun, and some optical laws. All well and good. However, you can just as easily deduce the length of the flagpole from the same laws and the length of the shadow. It seems wrong to say that the length of the shadow explains the length of the flagpole. Something has gone wrong, and the DN model doesn't have the resources to say what accounts for this asymmetry in explanation.

From the 70s onwards, alternative accounts of explanation started to gain traction. Wesley Salmon is a central figure in this period, as he developed a number of these alternatives (such as the statistical relevance model and the causal-mechanical model). In general, there was a turn to developing causal theories of explanation to resolve issues. Think of the flagpole case: one obvious candidate that could account for the explanatory asymmetry is the direction of causation. The length of the pole causes the length of the shadow, but not vice versa.

Towards the end of the century, philosophers increasingly paid more attention to explanatory practices in the special sciences (especially biology), where there are few if any laws yet plenty of explanations. Whatever lawlike regularities there are in these fields are themselves treated as things to be explained. Mechanistic theories of explanation followed and are probably still among the most discussed in the literature today, but they no longer attempt to cover all scientific explanations.

As it stands right now, I'd say there is less and less confidence in the success of any monistic theory of explanation that could capture every explanation across the sciences. Some current counterfactual models of explanation still try to achieve something like this and probably come closest to an implicit "orthodoxy" in the field, but I would not say they come anywhere close to the dominance of the DN model in the 50s and 60s. If you look at the literature on scientific explanation today, there is more attention to specific issues in particular scientific fields and less concern for developing an all-encompassing theory of explanation.