Identity refers to the distinctive character belonging to any given individual，or shared by all members of a particular social category or group.The issue of identity is attracting increasing attention in linguistic research.Halliday’s view of language mentions identity as one of the aspects of social life which is bound into grammar.It is generally accepted that language is a means of expressing social identity.

As a means of social practice，academic writing plays a significant role in the development of science.Recent research clearly indicates that academic writing is not a uniform body of discourse but varies according to disciplinary conventions，cultural expectations and writers’ professional status and experience.In the process of academic writing，writers may take into considerations of these conventions and expectations to make themselves accepted as qualified insiders in their respective communities.The production of writing is a manifestation of the writers’ identity.

Based on the above assumptions，this study focuses on the construction of authorial identity in academic discourse.Methodologically，it is a corpus-based descriptive analysis and the discussion is set against the background of contrastive analysis between English and Chinese.The data chosen for the study are published research articles （RAs） of Linguistics and Chemistry，representing the disciplines which belong to the ‘soft’ and ‘hard’ sciences respectively.The contrastive approach helps to examine the influencing factors in identity construction.The research investigates various linguistic resources which writers utilize for signaling their identities in claim-making and in the interaction with the readers.The investigations show that these resources project authorial identity in different degrees，from explicit to implicit.

The explicit representation of authorial identity is realized through first person references which express the utmost visibility of writers in academic writing.In presenting themselves，writers of RAs may strategically use first person singular pronouns （FPSPs） or first person plural pronouns （FPPPs）.Use of FPSPs is the most direct way to stress the authority of writers.Use of FPPPs is comparatively complex in the sense that the referents of the pronouns may be ambiguous.In this study，FPPPs are classified into four sub-categories.They are collective we，editorial we，inclusive authorial we and generic we.

With the help of context，different rhetorical roles of the first person authorial pronouns are recognized.The rhetorical roles demonstrate the activities of writers in academic writing.These roles include discourse-organizer，researcher and opinion-holder.The role of discourse-organizer foregrounds the writer’s responsibility of framing the text for the readers.The researcher role highlights not only the writer’s familiarity with his/her disciplinary practices，but also the attempt to gain the readers’ trust by validating his/her research framework.The role of opinion-holder emphasizes the interactive nature of academic writing.As an opinion-holder，a writer may open a dialogue with the readers to negotiate claims.

The authorial identity is implicitly projected by means of agentless constructions and stance markers.Agentless constructions include constructions with inanimate subjects and anticipatory it-clauses.The investigation indicates that agentless constructions，though construct less powerful and overt identities，do not obscure the authorial identity completely.Instead，these linguistic means allow writers to maintain a balance between overt evaluative positioning and detached claim-making when illustrating claims，constructing a convincing argument or drawing tentative conclusions.Thus writers could construct an identity that is likely to persuade community members to accept the validity of their research.

Stance markers are widely recognized as a key resource through which the authorial viewpoint is indirectly conveyed，projecting a textual “voice” or community recognized personality.The stance markers investigated in the present study include hedges and boosters.Hedges and boosters are interpersonal aspects of language use.As regards authorial identity projected in RAs，they work as the ways that writers intrude to stamp their personal authority onto their arguments or step back and disguise their involvement.The findings show that hedges help project writers’ personae of caution，modesty and deference，while boosters highlight writers as competent members of the discourse communities.The rhetorical employment of these stance markers enables an academic writer to seek a balance between the researcher’s authority as expert-knower and his/her humility as disciplinary servant.

Considering the results of the comparison both between languages and between disciplines，three potential influencing factors are identified.These factors are cultural conventions，disciplinary variability and pragmatic considerations.These factors may overlap or work independently for the accounts of the results of the study.

The investigation of authorial identity in academic discourse has theoretical and pedagogical implications.Theoretically，the proposed theoretical framework reveals the relation between the socio-cultural factors and linguistic devices with the modulation of genre theory in academic writing.The linguistic resources examined for the construction of authorial identity and the findings about the explicit and implicit projection of authorial identity enrich academic writing theory and research.Pedagogically，this study is a useful starting point to raise writers’ awareness of the explicit/implicit linguistic resources available for the projection of authorship.The comparative analysis provides teachers and students with knowledge of preferred patterns in academic writing.