Django管理员没有显示模型

如果我能弄清楚为什么我的模型没有在管理员中显示,我该死的.

models.py看起来像这样:

from django.db import models

class Publication(models.Model):
    title = models.CharField(max_length=255)

    def __unicode__(self):
        return unicode(self.title)

admin.py

from django.contrib import admin
from publications.models import Publication

admin.site.register(Publication)

settings.py

...

MIDDLEWARE_CLASSES = (
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    # Uncomment the next line for simple clickjacking protection:
    # 'django.middleware.clickjacking.XFrameOptionsMiddleware',
)

TEMPLATE_CONTEXT_PROCESSORS = (
'django.core.context_processors.request',
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
)    


INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # Uncomment the next line to enable the admin:
    'django.contrib.admin',
    # Uncomment the next line to enable admin documentation:
    # 'django.contrib.admindocs',
    'south',
    'publications',
)

目录结构:

xrdb/
??? manage.py
??? publications
?   ??? __init__.py
?   ??? models.py
?   ??? tests.py
?   ??? views.py
??? xrdb
    ??? __init__.py
    ??? admin.py
    ??? settings.py
    ??? urls.py
    ??? wsgi.py

从管理页面,我可以看到组,用户和站点.没有出版物!!

任何帮助？谢谢!!

编辑:我已经同步和迁移,admin.autodiscover()在urls.py中.

编辑II:更新了上面的文件.添加了目录结构.