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讨论了正项级数的两种判别法:比值判别法和根值判别法,以及两者的关系,得出凡是可用比值判别法的正项级数必能用根值判别法,逆命题不成立,根据具体问题的特点采用不同的方法,解题得难以程度不同。 相似文献
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讨论了正项级数的两种判别法:比值判别法和根值判别法,以及两者的关系,得出凡是可用比值判别法的正项级数必能用根值判别法,逆命题不成立,根据具体问题的特点采用不同的方法,解题得难以程度不同。 相似文献
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本文根据不同的随访资料类型,介绍两种寿命表法,即完全数据的队列寿命表法和不完全数据的队列寿命表法.由该两种方法估计的各项指标均数及标准误与传统的平均数法结果相同.而对于在随访期间发生失访或者终检的情况时,就必须采用不完全数据队列寿命表法. 相似文献
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由生物物理研究所主持,植物研究所参加完成的"菠菜主要捕光复合物的晶体结构"研究成果以Article的方式发表在2004年3月18日出版的Nature上,该晶体结构图被选作本期杂志的封面图案.本文介绍了该项成果的研究背景、意义、主要创新点及方法. 相似文献
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秦仁昌 《中国科学院研究生院学报》1964,9(1):99-99
The fern genus Diplaziopsis C. Chr. of Index Filicum has long been considered as
a monotypic one, with the sole species, D. javanica (B1.) C. Chr. from tropical Asia. In
1906, H. Christ described a second species, Allantodia cavaleriana Christ (=D. cavale-
riana C. Chr.) from Kweichow, West China, but this was since not fully recognized by
fern students in general, being often considered as a variety of the first species. This
is certainly a mistake, as is shown by ample herbarium specimens today. In the recent
work on the genus, the writer has found among the herbarium material two additional
new species from China, thus bringing the genus up to four species in Asia, mainly from
China, where, as it is, the genus has its center of development from the long past.
Phylogenetically, Diplaziopsis C. Chr. represents one of the offshoots from the great
stock of diplazioid ferns, of which the genus Diplazium Sw. constitutes the main body
of the group and from which our genus differs chiefly in its leaves of a thin texture with
reticulated venation, but not so much in its type of indusium as it has generally been
emphasized by most botanists in the past, for, as it is, the type of indusium in Di-
plaziopsis also prevails in many species of Diplazium, for which C. B. Clarke (Trans.
Linn. Soc. ser. 2, Bot. I:495, 1880) created, but really superfluously, a subgenus Pseudal-
lantodia, about which the writer will dwell in another paper in the near future. Suffice
it to say here that the indusium in Diplaziopsis as revealed by the species treated here
is, indeed, typical of diplazioid ferns, only often, as it happens, with its adaxial edge
pressed so tight under the expanding sorus that it is unable to open freely along its upper
free edge and, as a result, its thin vaulted back bursts open from the pressure of the ex-
panding sorus underneath.
As a result of the present study, following four species of the genus have been re-
cognized.
Diplaziopsis javanica (B1.) C. Chr. Ind. Fil. (1905) 227.
Wide spread in tropical Asia, northwardly to Bakbo and the southern part of Yun-
nan, China.
D. cavaleriana (Christ) C. Chr. Ind. Fil. Suppl. I (1913) 25.
Ranges from West China through northern part of Fukien of East China to Japan.
D. intermedia Ching, sp. nov.
Endemic in West China: Mt. Omei, Szechuan, and Kweichow.
D. hainanensis Ching, sp. nov.
In conclusion, it may be pointed out that with the modern plant taxonomy pursued
in a more efficient manner than in the past, and especially by the introduction of the
cytotaxonomic methods, the so-called “monotypic genera”, as conceived by the orthodox
systematists, will continue to prove, to a great extent, to be lack of enough scientific
ground. The fact that the “monotypic genus” of Diplaziopsis C. Chr. is now found to
be a genus of four well-defined species is once again an instance to illustrate the pointat issue. 相似文献
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