全文获取类型
收费全文 | 673篇 |
免费 | 89篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 33篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 30篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 34篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1970年 | 4篇 |
1968年 | 3篇 |
1966年 | 5篇 |
排序方式: 共有763条查询结果,搜索用时 15 毫秒
721.
Cristina M. Coates 《Inorganica chimica acta》2009,362(13):4797-9373
In order to assess the changes in the redox activity of a metal ion that result from inductive effects, three electronically modified derivatives of the ligand, N-benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LH), have been prepared: N-(4-nitro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LNO2), N-(4-chloro)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LCl), and N-(4-methoxy)benzyl-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (LOMe). Due to the lack of a fully conjugated π-system between the 4-benzyl substituent and the N-donors, the electronic perturbation should influence a bound metal ion’s redox properties through primarily inductive pathways. The organic ligands react with MnCl2 to form mononuclear complexes with the general formula [Mn(LR)Cl2]. The parent ligand, LH, and its three derivatives each coordinate Mn(II) ions in a cis-α conformation, with the amine N-donors installed trans to the Mn-Cl bonds. Despite its distance from the metal ion, the electron-donating or - withdrawing group has a notable impact on both the metrical parameters of the Mn(II) compounds and the Mn(III/II) reduction potential. A single inductive perturbation can vary the reduction potential by as much as 50 mV. 相似文献
722.
723.
Extensive chromosome repatterning was demonstrated in Stylidium crossocephalum F. Muell by means of karyotype analysis of a sample of 191 native plants taken from 69 collection sites throughout the species range between Yanchep and Geraldton on the coastal sand plain north of Perth in Western Australia. Both polymorphic and polytypic variation occurred. Of the 42 haploid genomic combinations of chromosomes defined in this study, no less than 26 were found as heterozygotes only and were of localized occurrence. 16 stable genomes, occurring as homozygotes, generally had more extensive but polytypic distributions. Although pollen fertility in native plants was always found to be greater than 40%, and usually greater than 90%, synthetic crosses proved to be totally or almost completely pollen sterile. This is explained on the hypothesis that chromosome repatterning in this species is associated with the generation and modulation of recessive zygotic lethal systems which exist in locally coadapted combinations. These eliminate the products of self fertilization while permitting the relatively free development of cross pollination products in natural populations. 相似文献
724.
725.
726.
727.
The ability of five strains of Listeria monocytogenes to initiate growth at five different temperatures in brain heart infusion (BHI) broth adjusted to various water activity ( a w ) values with either sodium chloride (NaCl), sucrose or glycerol was investigated. Glycerol was the least toxic of the three solutes studied, with three of five strains of L. monocytogenes capable of growing in BHI broth adjusted with glycerol to an a w value of 0.90 at 30 C, compared to a w minima of 0.93 and 0.92 in broth adjusted with sucrose and sodium chloride, respectively. The minimum a w value required for growth generally increased as the incubation temperature decreased. Listeria monocytogenes appeared to tolerate glycerol and NaCl best when growing at 30 and 15°C, respectively, while for sucrose, temperature did not appear to influence growth of the organism. Listeria monocytogenes is one of the few food-borne pathogens that can grow at an a w value below 0.93. 相似文献
728.
729.
730.