全文获取类型
收费全文 | 2025篇 |
免费 | 24篇 |
国内免费 | 178篇 |
出版年
2023年 | 23篇 |
2022年 | 26篇 |
2021年 | 55篇 |
2020年 | 59篇 |
2019年 | 72篇 |
2018年 | 93篇 |
2017年 | 36篇 |
2016年 | 47篇 |
2015年 | 65篇 |
2014年 | 154篇 |
2013年 | 126篇 |
2012年 | 64篇 |
2011年 | 87篇 |
2010年 | 66篇 |
2009年 | 87篇 |
2008年 | 88篇 |
2007年 | 86篇 |
2006年 | 68篇 |
2005年 | 94篇 |
2004年 | 62篇 |
2003年 | 57篇 |
2002年 | 54篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 32篇 |
1998年 | 29篇 |
1997年 | 35篇 |
1996年 | 40篇 |
1995年 | 36篇 |
1994年 | 42篇 |
1993年 | 33篇 |
1992年 | 30篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 28篇 |
1986年 | 14篇 |
1985年 | 27篇 |
1984年 | 34篇 |
1983年 | 28篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有2227条查询结果,搜索用时 43 毫秒
21.
With the aim of making clear the boundaries between species in thePoa acroleucahisauchii-nipponica aggregate, chromosomes and morphological features of 746 collections gathered from 125 localities in Japan were examined.
For morphological observations, the voucher specimens of 95 collections whose chromosome numbers were reported previously
(Tateoka, 1985) were also used. Tetraploids (2n=28) and hexaploids (2n=42), as well as a few pentaploids which were the hybrids
between 4× and 6×, were found. By examining morphological features of these collections, two groups were recognized in tetraploids
and one in hexaploids. The two tetraploid groups corresponded toPoa acroleuca Steud. andP. hisauchii Honda, and the hexaploid group toP. nipponica Koidz. It was confirmed that the hairiness on the internerve surface of lemma, ligule hairiness and the length ratio of anther/
lemma are the most important features for discriminating between these species; panicle shape, leaf shape and anther length
are also helpful for the identification. The ambiguity of the boundaries between species which was hitherto present in the
taxonomy of this species aggregate was unrelated to the creation of nature itself but was attributable to the insufficiency
of our research work. 相似文献
22.
23.
近几年来,在武汉东湖,每到深秋至次年初夏都出现数量较多,主要附生在枝角类和桡足类等浮游动物体表的柄裸藻属(Colacium Ehr.)植物;在冬末春初,出现种群数量的高峰。自1981年至1984年,作者曾对它进行过有关形态、分类和生态方面的探讨。在本文仅简述其有关形态和分类方面的问题。 相似文献
24.
世界蚜虫分类研究进展 总被引:4,自引:0,他引:4
本文综述了世界蚜虫分类研究进展。内容包括形态分类、细胞分类、生物化学分类以及化石研究等,并以M.L.Sharma的文献目录为基础,对世界蚜虫分类研究报告篇数进行统计。结果表明:世界各国蚜虫分类研究进展极不平衡,美国、加拿大、日本及欧洲的一些国家包括荷兰、丹麦、瑞典、捷克、波兰、德国等其α分类任务基本完成,印度也进展较快,离完成α分类任务为期不远。苏联欧洲部分也已基本完成,亚洲部分和中国尚有大量α级分类工作有待完成。 相似文献
25.
26.
27.
28.
29.
J. S. C. Smith O. S. Smith 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,71(4):607-612
Summary Alcohol soluble seed storage proteins (zeins and alcohol soluble glutelins) of maize (Zea mays L.) were separated by reversed-phase high-performance liquid chromatography (RP-HPLC). The objectives were to assess the reproducibility of chromatographic profiles using seed of inbred lines that had been produced in different locations and years. Reproducible differences between sources were seen but these were restricted to proteins that contributed 2% or less to an inbred profile. The majority of variation (93% for peak percent area; 99.8% for elution time) was between inbreds. RP-HPLC can therefore provide distinctive phenotypic profiles that are largely characteristic of genotype. Such qualitative and quantitative data will be valuable for studies of taxonomy, evolution, genetics, and germplasm identification. 相似文献
30.
Osbertia, a stoloniferous group confined to the montane regions of Mexico and adjacent Guatemala, was first proposed as a genus byGreene (1895), but most workers have retained the taxon as part ofHaplopappus. It is clearly closer toNoticastrum, Erigeron orHeterotheca than it is toHaplopappus sensu stricto. The present treatment recognizes two species, a widespread highly variableOsbertia stolonifera and a newly describedO. chihuahuana from northwestern Mexico. Distribution maps, distinguishing features, full synonymy and illustrations are presented. 相似文献