初级的

This Hornbook provides an overview of the history and traditions underlying today's admiralty and maritime law.

本书是关于海事法历史与传级读本。

Ferns were the first terricolous vascular plants, and still comprise an important part of primary productivity of ecosystems.

蕨类植物是最早登陆维管植物，至今仍然是生态级生产力重要组成部分。

First, the precursor of chromatoid body adhered to the inner surface of the nuclear envelope.The nuclear envelope where the chromatoid body adhering was destroyed.

在级精原细胞细胞核中，拟染色体前体物质先附著于核膜，处核膜崩溃。

By chiseling a BOL on a surface of a lens, a apochromatic system is composed, which actualizes the system's apochromatism, as well as revising primary aberration.

并将二元光学面刻画在透镜表面，在校正级像差同时，实现了复消色差。