常用的氮肥、磷肥和钾肥一般呈什么颜色和形状?如何简易鉴别氮肥和钾肥?
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采用摇表(或接地电阻测试仪)直接得到接地电阻的读数,因此不用单独测量电压和电流,也不用布放电流线和电压线。()
A. 正确
B. 错误
基站安装需要的设备及附件有基站设备、POE、扇区天线、天线馈线、()、屏蔽RJ45水晶头、天线支架、接地线、防水套件基站同步单元。
A. 基带电缆
B. 服务器
C. 磁盘阵列
A database is running in ARCHIVELOG mode and regular backups are performed. A user receives the following error message . Which is the recommended sequence of operations you need to perform for the query successfully?()
A. Drop the affected tablespace, re-create the tablespace, restore the datafiles, and the tablespace.
B. Take the affected datafile offline (if not already offline), restore the damaged image of the datafile, and then bring it online.
C. Restart the database in MOUNT mode, restore the damaged datafile, recover the datafile and then open the database with resetlogs.
D. Put the database in RESTRICTED mode, restore all the datafiles in the affected datafile and recover the tablespace, and then put the database in normal operational mode.&e