您可以使用Angular提供的Http Interceptor来实现这一点。拦截器是一个中间件，它拦截HTTP请求，可以用来修改请求和响应。

以下是一个示例，演示如何在请求头中添加Authorization标头：

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler } from '@angular/common/http';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest, next: HttpHandler) {
    const authReq = req.clone({
      headers: req.headers.set('Authorization', 'Bearer ' + localStorage.getItem('token'))
    });

    return next.handle(authReq);
  }
}

将此拦截器提供给您的应用程序：

import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AuthInterceptor } from './auth.interceptor';

@NgModule({
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true
    }
  ]
})
export class AppModule { }