全文获取类型
收费全文 | 3628篇 |
免费 | 264篇 |
国内免费 | 140篇 |
出版年
2024年 | 4篇 |
2023年 | 61篇 |
2022年 | 36篇 |
2021年 | 87篇 |
2020年 | 68篇 |
2019年 | 93篇 |
2018年 | 100篇 |
2017年 | 110篇 |
2016年 | 121篇 |
2015年 | 109篇 |
2014年 | 116篇 |
2013年 | 278篇 |
2012年 | 119篇 |
2011年 | 105篇 |
2010年 | 95篇 |
2009年 | 138篇 |
2008年 | 170篇 |
2007年 | 161篇 |
2006年 | 146篇 |
2005年 | 146篇 |
2004年 | 164篇 |
2003年 | 142篇 |
2002年 | 137篇 |
2001年 | 129篇 |
2000年 | 160篇 |
1999年 | 102篇 |
1998年 | 106篇 |
1997年 | 86篇 |
1996年 | 106篇 |
1995年 | 65篇 |
1994年 | 55篇 |
1993年 | 60篇 |
1992年 | 73篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 51篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 30篇 |
1985年 | 31篇 |
1984年 | 38篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有4032条查询结果,搜索用时 671 毫秒
111.
J. J. González-Aguilera A. Ma. Fernández-Peralta 《Plant Systematics and Evolution》1981,139(1-2):147-154
The meiotic behaviour abnormalities, fertility and size of pollen of 6 taxa ofSesamoides have been analysed. Besides diploids (2x), polyploids (4x, 6x, 8x) have been found. The chromosome base number is x = 10, but an origin from x = 5 is suggested. 相似文献
112.
(+)-Abscisic acid was isolated as the methyl ester from Pinus densiflora pollen and identified spectroscopically. 相似文献
113.
Solvent-extractable lipids in Pinus densiflora pollen were investigated. The cis- and trans-isomers of 1,16-dioxo-, 1-hydroxy-16-oxo- and 1, 16-dihydroxyhexadecan-7-yl p-coumarates were identified. 相似文献
114.
Michael D. Grove Gayland F. Spencer Philip E. Pfeffer Nagabhushanam Mandava J.David Warthen Joseph F. Worley 《Phytochemistry》1978,17(7):1187-1189
6-d-Glucopyranosyl esters of palmitic, oleic, linoleic and linolenic acids were identified in Brassica napus (rape) pollen. These esters are inactive as plant growth promoters in the bean second-internode bioassay. 相似文献
115.
利用SSR分子标记对中国沙棘(Hippophae rhamnoides ssp. sinensis Rousi)自由授粉的种子进行父本分析,研究其子代的父本来源和花粉散布模式。结果显示:在80%的置信水平上,193个子代中有104个个体可以确定花粉来源;在20个确定的父本中,16个为中国沙棘,4个为肋果沙棘(H.neurocarpa S.W.Liu et T.N.He)。传粉格局分析结果显示,中国沙棘有效花粉散布范围为3~71 m,平均距离为20.4 m,2株母本分别有87.23%和78.95%的有效花粉来自距其30 m的范围之内,研究结果表明中国沙棘自然种群以近距离传粉为主。此外,在黑河上游沙棘杂交带中,中国沙棘子代中的肋果沙棘花粉平均贡献率达到14.84%,表明中国沙棘与肋果沙棘存在较高的种间当代花粉流。 相似文献
116.
The relationship between floral display size, pollen carryover and geitonogamy in Myosotis colensoi (Kirk) Macbride (Boraginaceae) 总被引:2,自引:0,他引:2
ALASTAIR W. ROBERTSON 《Biological journal of the Linnean Society. Linnean Society of London》1992,46(4):333-349
The relative amounts of self- and cross-pollen deposited on stigmas depends on both the number of pollinator visits that occur within plants and the amount of pollen carryover. Data collected for Myosotis colensoi (Kirk) Macbride and compiled from a survey of the literature, reveal that pollen carryover is frequently very high (upwards of 80%) and this at least partially relieves some of the effects of geitonogamous pollinator movements. It is suggested that in some cases, selection for traits that confer a high rate of pollen carryover may occur. Aspects of the plant–pollinator interaction that are likely to influence pollen carryover are discussed. 相似文献
117.
In vitro germination of wheat pollen on raffinose medium 总被引:1,自引:0,他引:1
118.
Despite the potential importance of adult nutrition in the ecology of parasitoids, information on the range of natural foods
they exploit is confined to a relatively small number of species. We provide some simple guidelines for determining dietary
range in adult parasitoids, both to facilitate and to encourage further research into this aspect of parasitoid biology.
相似文献
119.
N. B. M. Brantjes 《Plant Systematics and Evolution》1982,141(1):41-52
Polygala vauthieri andP. monticola var.brizoides have secondary pollen presentation from a basket-like structure on the style apex. This basket is loaded after the first visit by a bee. Pollen reception, therefore, can precede the issue of pollen. A sticky stigma secretion glues the pollen from the basket under the head of the bee visitor in an exactly predetermined spot on the left side only. This position mostly forms a kind of safe spot, where the bee can not remove the pollen. The exact position on the bee's head is determined by the species specific distance between style tip and nectary in the visited flower. In this way the two sympatric species deposit the pollen 2 mm apart on the visitor and so can avoid hybridization pollination, while being visited by the same group of bees. 相似文献
120.