全文获取类型
收费全文 | 1502篇 |
免费 | 101篇 |
国内免费 | 4篇 |
出版年
2023年 | 14篇 |
2022年 | 27篇 |
2021年 | 35篇 |
2020年 | 24篇 |
2019年 | 27篇 |
2018年 | 39篇 |
2017年 | 37篇 |
2016年 | 48篇 |
2015年 | 71篇 |
2014年 | 87篇 |
2013年 | 106篇 |
2012年 | 142篇 |
2011年 | 115篇 |
2010年 | 79篇 |
2009年 | 77篇 |
2008年 | 95篇 |
2007年 | 106篇 |
2006年 | 88篇 |
2005年 | 71篇 |
2004年 | 54篇 |
2003年 | 60篇 |
2002年 | 49篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有1607条查询结果,搜索用时 250 毫秒
1.
2.
Paul J. Chuba Myron A. Leon Amit Banerjee Sunil Palchaudhuri 《Molecular & general genetics : MGG》1989,216(2-3):287-292
Summary
Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters. 相似文献
3.
Rakesh M. Vohra Uttam C. Banerjee Sunil Das Syamalima Dube 《Biotechnology letters》1989,11(12):851-854
Summary A highly active extracellular rifamycin oxidase was isolated fromCurvularia lunata var.aeri. The enzyme has a pH optimum of 6.5 and temperature optimum of 50°C. 相似文献
4.
It is well established that plasmids are involved in the expression of lipopolysaccharide in certain species of Shigella. In Shigella sonnei, both the biosynthesis of oligosaccharide side chains (O antigen), and cell invasiveness are controlled exclusively by a 120 megadalton (MDa) plasmid. In Shigella dysenteriae 1, a 10 kilobase (kb) plasmid is required for O-antigen production. Shigella dysenteriae 1 strains devoid of this plasmid lose the ability to synthesize O antigen. Interestingly, this 10-kb plasmid is not stably maintained in Escherichia coli K-12 strains, where it is lost spontaneously at a high frequency. Our genetic analyses of Shigella dysenteriae 1 strain IDBM11 and its derivatives indicate that the stability of this plasmid is associated with the histidine region of the chromosome which is unique to Shigella dysenteriae. Furthermore, the 10-kb plasmid is stably maintained in wild-type IDBM11 with an intact histidine locus. However, this plasmid is not stable in IDBM11 derivatives (e.g., IDBM11-1 and IDBM11-2), in which the his locus has been substituted with the histidine region of an E. coli K-12 chromosome. The S. dysenteriae IDBM11 strain, and its derivatives (lacking a 10-kb plasmid), displayed an invasive property as demonstrated by their internalization by HeLa cells in an in vitro assay. Thus the 10-kb plasmid of Shigella dysenteriae 1 is required for O-antigen synthesis but not for cell invasion. 相似文献
5.
6.
A restriction enzyme map of the IncFI plasmid ColV2-K94 was generated using EcoRI, BamHI, HindIII, and XhoI; the genetic features of this element were then mapped from previous heteroduplex studies. 相似文献
7.
Sunil Palchaudhuri Ranajit Kumar Dipak Sen Ruma Pal Sajal Ghosh Banwarilal Sarkar Sujit K. Bhattacharya Sudhir C. Pal 《FEMS microbiology letters》1985,30(1-2):187-191
Abstract Multiple antibiotic-resistant Shigella dysenteriae type 1 isolates from a recent epidemic in West Bengal (India) showed identical plasmid patterns. All isolates were resistant to ampicillin (Am), chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm) and trimethoprim (Tp) and contained 6 plasmids, ranging from 2.5–120 kb. The Am resistance determinant was located on the 120 kb plasmid. This plasmid was unstable when the S. dysenteriae strains were grown above 37°C. The Bangladesh strains of S. dysenteriae type 1 showed identical plasmid patterns, except that many isolates were Am-sensitive and lacked the 120 kb plasmid. In strains from both Bangladesh and West Bengal, predominantly group-B plasmids conferred resistance to Cm and Tc. Comparisons of Eco R1 fragments generated from the total plasmid DNA content of each strain support the view that the plasmids present in the S. dysenteriae type 1 strains isolated from all recent epidemics in India and Bangladesh were identical. 相似文献
8.
9.
Isha Gupta Devender Singh Sitender Singh Pawan Kumar Shri Bhagwan Vinod Kumar Harish Kumar Sunil Kumar Chhikara 《Luminescence》2023,38(5):585-599
Terbium(III)-doped yttrium aluminate perovskite (YAP:xTb3+) (x = 0.01–0.08 mol) was synthesized using a simple gel-combustion method. Structural elucidations were performed using X-ray diffraction (XRD) and Rietveld analysis. Fourier-transform infrared spectral studies validated the efficient synthesis of designed doped samples. Transmission electron microscopic images showed the agglomerated irregular dimensions of the synthesized nanocrystalline materials. When excited at 251 nm, a strong emissive line attributed to 5D4 → 7F5 electronic transition was observed at 545 nm (green emission). The maximum luminescence was found at the optimized concentration (0.05 mol) of Tb3+ ions; this emission was quenched by dipolar–dipolar (d–d) interactions. Chromaticity (x and y) and correlated colour temperature parameters were obtained by analysing the emission profiles. Finally, the colour coordinates of nanophosphors were closer to the National Television Standards Committee green coordinates, which replicates their potency in the design and architecture of R-G-B-based white LEDs. 相似文献
10.