平板叶片

圆弧叶片

机翼型叶片

平板曲线向后叶片

I was astonished, for example, when a friend told me that he was offering to care for his younger brother and sister so that his father could take a vacation for his birthday—this was a gift to him. For us, this would be considered duty rather than a gift. Even between friends' gestures of this sort might be considered 'gifts' here.

While many students do call their professors, 'Professor' so and so or 'Dr.', so and so, some professors prefer to be called familiarly by their first names. And in the spirit of informality, many professors may invite students to their homes or can be seen chatting with students over a meal or a cup of coffee in the school cafeteria. A good number of instructors even request that students fill out Class evaluation forms which assess the content and presentation of the course.

My roommate was very sociable and had many boyfriends who came to visit often very late. One night, after midnight, I had to stay in the bathroom for an extra 40 minutes because I had heard a man's voice in my room. My roommate did not realize how awkward I would feel meeting a man while I was in my nightgown. You see, American students tend to be much more casual about these matters.

On many occasions, for instance, close friends or sometimes even casual acquaintances embrace or kiss each other on the cheeks in greeting or bidding farewell. It may even happen that where couples are close friends, the two husbands will kiss the other man's wife!

In the United States, for example, if a student wants to invite his teacher to a dinner party, the invitation should be sent a week or so before the party date. If the invitation is extended only three or four days before the party date, the teacher will feel he is not highly regarded.

For example, many American students seem to like to listen to popular and sometimes loud music while studying in their rooms. Sometimes they will even leave the music on when they leave the room. For Some reason, many will tell you, music helps them to relax and concentrate, an idea which other foreign students and I found very strange and disturbing. We'd like to study quietly without any disturbance.

从语义上来说，这个句子是不符合逻辑的；

这个句子从语法上来说，是完全正确的。

从语法上来说，这个句子是不符合规定的；

这个句子意义是可以理解的。

数理统计

应用统计

这个结构是表达与将来事实相反的情况的虚拟语气结构.

这个结构是表达混合情况的虚拟语气结构.

这个结构是表达与现在事实相反的情况的虚拟语气结构.

这个句子可以翻译成“如果你现在听从我的建议，你身体状况很快就会好起来。”

理论统计学

应用统计学

数理统计学

社会统计学

化学方法测定中性和石灰性土壤中速效磷，最长用的浸提剂是0.5M NaHCO3溶液

由于碳酸根的同离子效应，降低了碳酸钙的溶解度，抑制植物无效Ca-P的溶解，仅浸提生物活性较大的Ca-P

碳酸盐的碱液同时也可以使活性较大的Fe-P和Al-P发生水解作用而被浸提出来。

碱性溶液溶解土壤有机质，使有色的有机物质进入溶液，会影响比色结果，所以要用空白调节分光光度计的零点，以消除这一系统误差。

首要表现是对祖国的忠诚与热爱

反映了个人对祖国的依存关系

是鼓舞和凝聚一个民族的精神支柱

是调节个人和祖国之间关系的道德要求、政治原则和法律规范

先用BaCl2溶液制备Ba2+饱和土壤复合体

再定量加入标准MgSO4溶液，交换土壤复合体中的Ba2+，制备Mg2+饱和土壤复合体

最后滴加标准MgSO4溶液，调节待测液的电导率，使交换后待测悬浊液的电导率与参比液电导率相等

在用BaCl2和MgSO4溶液制备土壤复合体时，交换液中的Ba2+或Mg2+只置换下土壤胶体上吸附的K+，Na+，Ca2+和Mg2+。