全文获取类型
收费全文 | 3149篇 |
免费 | 156篇 |
国内免费 | 202篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 44篇 |
2021年 | 66篇 |
2020年 | 70篇 |
2019年 | 73篇 |
2018年 | 44篇 |
2017年 | 59篇 |
2016年 | 91篇 |
2015年 | 74篇 |
2014年 | 96篇 |
2013年 | 193篇 |
2012年 | 108篇 |
2011年 | 135篇 |
2010年 | 114篇 |
2009年 | 163篇 |
2008年 | 162篇 |
2007年 | 158篇 |
2006年 | 151篇 |
2005年 | 120篇 |
2004年 | 140篇 |
2003年 | 117篇 |
2002年 | 94篇 |
2001年 | 85篇 |
2000年 | 63篇 |
1999年 | 103篇 |
1998年 | 74篇 |
1997年 | 73篇 |
1996年 | 69篇 |
1995年 | 78篇 |
1994年 | 91篇 |
1993年 | 70篇 |
1992年 | 63篇 |
1991年 | 57篇 |
1990年 | 61篇 |
1989年 | 51篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 47篇 |
1985年 | 38篇 |
1984年 | 26篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1972年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有3507条查询结果,搜索用时 15 毫秒
1.
JUN YOKOYAMA TATSUYA FUKUDA AKIKO YOKOYAMA MASAYUKI MAKI 《Botanical journal of the Linnean Society. Linnean Society of London》2002,138(3):369-380
Morphologically intermediate plants between Weigela hortensis (Siebold & Zucc.) K.Koch and W. maximowiczii (S.Moore) Rehder have been found in Miyagi and Yamagata Pref., northern Japan. Quantitative character analyses of flowers, pollen stainability and molecular analyses indicated that the intermediate plants were hybrids of those two species. This is the first record of an intersectional hybrid with W. maximowiczii (sect. Weigelastrum ) as one of the parent species. The morphological differences among hybrid individuals imply the possibility of backcrosses or formation of second or later generations of hybrids, although those may be quite rare because of a low frequency of viable pollen grains. Causes of hybridization between two distantly-related species in Weigela are discussed. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 369–380. 相似文献
2.
A phosphotransferase-dependent aryl-β-glucoside uptake and utilisation system (abg) was isolated from the ruminal Clostridium (“C. longisporum”). The system is composed of three genes, abgG, abgF and abgA, and a number of regulatory regions, including terminator/antiterminator type stem-loop structures preceding the abgG and abgF genes. Similarity analysis of the proteins encoded by these genes indicated that they were responsible for the regulation
of the abg system through antitermination (AbgG), the uptake and phosphorylation of aryl-β-glucosides (AbgF) and the hydrolysis of the
intracellular phosphorylated glycosides (AbgA). Experimental evidence for the functions of AbgF and AbgA was obtained. Although
it was not possible to demonstrate any function for AbgG, a promoter 5′ to the abgG gene was identified which was responsible for expression of the downstream genes. The abg system is remarkably similar to operons from the gram negative Enterobacteriaceae, both in the coding and non-coding regulatory
regions.
Received: 3 April 1997 / Accepted: 8 September 1997 相似文献
3.
4.
5.
The ability of Bacillus subtilis, strain BB, to colonise cabbage seedlings endophytically was examined following seed inoculation. Strain BB was recovered from different plant parts including leaves (cotyledons), stem (hypocotyl) and roots. While high bacterial populations persisted in the roots and lower stem, they were lower in the upper stem and leaves through time. In addition to cabbage, strain BB colonised endophytically the roots of 5 other vegetable brassicas. Fatty acid methyl ester (FAME) and PCR fingerprinting analysis confirmed the reliability of the detection method. Studies conducted with transmission electron microscope (TEM) showed that BB mainly colonised intercellular spaces of cortical tissues including intercellular spaces close to the conducting elements of roots and stem of cabbage seedlings. Gold labelling was specifically associated with BB and the fibrillar material filling the intercellular spaces where bacterial cells were found. 相似文献
6.
Romano Gellini Filippo Bussotti Davide Bettini Paolo Grossoni Alessandro Bottacci 《Plant biosystems》2013,147(3-4):481-504
Abstract We propose a study of the main species belonging to the genus Quercus in Italy, characterized and identified by means of leaf surface observation, with special attention devoted to waxes, trichomes and stomata. Comparing our results with the classification proposed by SCHWARZ (1984), we find that species belonging to Schwarz's subgenus Quercus are recognizable because their waxes are structured in vertical scales; the two other subgenera (Sclerophyllodrys and Cerris) present smooth wax structures, their distinctive feature being the shape of the stomatal rima, which is roundish in Sclerophyllodrys and elliptical in Cerris. The study characterizes Quercus pubescens Willd. and Quercus petraea Liebl. by analyzing some morphometric traits; but the authors feel that further research is needed on these critical taxonomic entities. Lastly, the study examines forms of was degeneration correlated to the phenomenon known as oak decline. 相似文献
7.
8.
9.
M. Iranshahr 《Plant Systematics and Evolution》1987,155(1-4):55-57
Two species ofConsolida are described as new:C. lorestanica is distributed in W. Iran (Lorestan), andC. kandaharica is endemic to S. Afghanistan.Dedicated to Hofrat Prof. DrK. H. Rechinger on the occasion of this 80th birthday. 相似文献
10.