全文获取类型
收费全文 | 11194篇 |
免费 | 1016篇 |
国内免费 | 8篇 |
出版年
2021年 | 95篇 |
2018年 | 116篇 |
2017年 | 129篇 |
2016年 | 186篇 |
2015年 | 341篇 |
2014年 | 320篇 |
2013年 | 444篇 |
2012年 | 578篇 |
2011年 | 541篇 |
2010年 | 390篇 |
2009年 | 321篇 |
2008年 | 510篇 |
2007年 | 533篇 |
2006年 | 477篇 |
2005年 | 564篇 |
2004年 | 486篇 |
2003年 | 467篇 |
2002年 | 459篇 |
2001年 | 171篇 |
2000年 | 149篇 |
1999年 | 164篇 |
1998年 | 158篇 |
1997年 | 119篇 |
1996年 | 121篇 |
1995年 | 119篇 |
1994年 | 101篇 |
1993年 | 135篇 |
1992年 | 129篇 |
1991年 | 146篇 |
1990年 | 139篇 |
1989年 | 144篇 |
1988年 | 143篇 |
1987年 | 113篇 |
1986年 | 117篇 |
1985年 | 93篇 |
1984年 | 101篇 |
1983年 | 91篇 |
1982年 | 93篇 |
1981年 | 126篇 |
1980年 | 96篇 |
1979年 | 118篇 |
1978年 | 108篇 |
1977年 | 99篇 |
1976年 | 81篇 |
1975年 | 83篇 |
1974年 | 107篇 |
1973年 | 112篇 |
1972年 | 87篇 |
1970年 | 96篇 |
1969年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
41.
42.
Jennifer J Beard David Evans Walter Peter G Allsopp 《Australian Journal of Entomology》2003,42(1):51-78
Abstract In many areas of the world, spider mites are significant pests of sugarcane. Australia is currently fortunate in lacking the most destructive species, and usually suffers only sporadic damage. Herein, we provide a key to the genera of spider mites associated with sugarcane, review the most significant genus, Oligonychus Berlese, and provide a key to the species of grass-feeding Oligonychus in the Australasian region. The species O. araneum Davis, O. digitatus Davis, O. grypus Baker and Pritchard, O. orthius Rimando, and O. oryzae (Hirst) are redescribed, while the Australian O. zanclopes sp. n. Beard and Walter from sugarcane and rice, O. turbelli sp. n. Beard and Walter, O. ephamnus sp. n. Beard and Walter and O. festucolus sp. n. Beard and Walter from other grasses, are newly described. Previous records of O. grypus in Australia appear to be misidentifications of what is described here as the new species O. zanclopes . 相似文献
43.
44.
45.
Mohammed Safwat Abdel-Salam Walter Klingmüller 《Molecular & general genetics : MGG》1987,210(1):165-170
Summary A method for transposon mutagenesis in Azospirillum lipoferum 29708 is reported with transposon Tn5. The suicide plasmid pSUP2021 was used to deliver Tn5 in A. lipoferum using Escherichia coli SM10 as the donor. Neomycin-resistant transconjugants were detected at a frequency of 6x10-6 per recipient. Different types of mutants were isolated, e.g. auxotrophic, coloured, IAA-negative, and IAA-overproducers. Among the auxotrophic mutants, cysteine and methionine requirers prevailed. Random Tn5-insertion with only one copy per mutant was demonstrated by Southern blotting and hybridization. Tn5-induced mutants are relatively stable, with reversion rates of 2–20×10-8. A gene which is a part of the carotenoid pathway is closely linked to the histidine genes. The existence of two pathways for IAA production in A. lipoferum is discussed. 相似文献
46.
Vacuoles of tobacco mesophyll and of suspension-cultured cells were isolated in order to study the localization of peroxidase isoenzymes. Only basic peroxidases were detectable by electrophoretic separation of the vacuolar sap. Some of the basic peroxidases have formerly been described as an ionically bound cell-wall fraction. This fraction, however, was found to be an artifact produced by incomplete cell breakage. Reinvestigation of isolated cell walls confirmed that mainly acidic peroxidases are localized in the cell walls where they move freely or are bound. As a consequence of former and present results we think it probable that all of the peroxidase isoenzymes are secretory proteins because they have to be transported from the sites of synthesis in the cytoplasm to the sites of function, the extracytoplasmic spaces, cell wall (acidic peroxidases), and vacuole (basic peroxidases).Abbreviation ER
endoplasmic reticulum
- PAGE
polyacrylamide gel electrophoresis 相似文献
47.
Summary Sequence divergence between the 3 long terminal repeats (LTR) of avian reticuloendotheliosis virus (REV), deletion variant proviral clone 2-20-4, and spleen necrosis virus (SNV)—proviral clones 14-44, 60, and 70—was found to involve two classes of base substitutions: low-frequency interspersed and high-frequency clustered substitutions. Clones 2-20-4 and 14-44 have diverged 4.4% owing to low-frequency substitutions. In contrast, two high-frequency substitution segments have diverged by 30% and 29%, respectively. Clustered substitutions appear to be located either within or next to tandem repeats, suggesting their introduction concomitant with sequence deletions and duplications commonly associated with such repeats. A new 19-bp tandem repeat is found in clone 2-20-4. Its sequence could have evolved from the 26-bp repeats found in the SNV clones. 相似文献
48.
49.
50.