全文获取类型
收费全文 | 731篇 |
免费 | 47篇 |
国内免费 | 81篇 |
出版年
2023年 | 11篇 |
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 22篇 |
2019年 | 35篇 |
2018年 | 15篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 26篇 |
2014年 | 31篇 |
2013年 | 24篇 |
2012年 | 50篇 |
2011年 | 21篇 |
2010年 | 39篇 |
2009年 | 39篇 |
2008年 | 25篇 |
2007年 | 36篇 |
2006年 | 27篇 |
2005年 | 32篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1991年 | 4篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1982年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1959年 | 17篇 |
1958年 | 30篇 |
1957年 | 12篇 |
1956年 | 15篇 |
1955年 | 21篇 |
1954年 | 19篇 |
1953年 | 26篇 |
1952年 | 19篇 |
1951年 | 15篇 |
1950年 | 19篇 |
排序方式: 共有859条查询结果,搜索用时 15 毫秒
1.
DI MAGGIO G 《Bollettino della Società italiana di biologia sperimentale》1950,26(3):335-336
2.
3.
Purification and crystallization of ferric enterobactin receptor protein, FepA, from the outer membranes of Escherichia coli UT5600/pBB2 总被引:2,自引:0,他引:2
The ferric enterobactin receptor protein, FepA, was isolated and purified from the outer membranes of a genetically transformed strain of Escherichia coli (UT5600/pBB2) using anion-exchange chromatography, chromatofocusing and gel filtration. The purified protein was found to crystallize from 25 mM sodium phosphate buffer in the presence of 0.8% beta-D-octylglucoside under a range of conditions. The protein formed mostly small rods and needle-shaped crystals in the hanging drop method. 相似文献
4.
Influence of environmental factors on 2,4-dichlorophenoxyacetic acid degradation by Pseudomonas cepacia isolated from peat 总被引:1,自引:0,他引:1
A Pseudomonas cepacia, designated strain BRI6001, was isolated from peat by enrichment culture using 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole carbon source. BRI6001 grew at up to 13 mM 2,4-D, and degraded 1 mM 2,4-D at an average starting population density as low as 1.5 cells/ml. Degradation was optimal at acidic pH, but could also be inhibited at low pH, associated with chloride release from the substrate, and the limited buffering capacity of the growth medium. The only metabolite detected during growth on 2,4-D was 2,4-dichlorophenol (2,4-DCP), and degradation of the aromatic nucleus was by intradiol cleavage. Growth lag times prior to the on-set of degradation, and the total time required for degradation, were linearly related to the starting population density and the initial 2,4-D concentration. BRI6001, grown on 2,4-D, oxidized a variety of structurally similar chlorinated aromatic compounds accompanied by stoichiometric chloride release. 相似文献
5.
Molecular recognition of siderophores in fungi: role of iron-surrounding N-acyl residues and the peptide backbone during membrane transport in Neurospora crassa.
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Recognition of ferric siderophores in Neurospora crassa was found to depend on the number and kind of N-acyl residues that surrounded the iron coordination center. In the coprogen series, uptake decreased in the order of coprogen, neocoprogen I, and neocoprogen II, indicating that gradual replacement of the N-transanhydromevalonyl groups by N-acetyl groups had an adverse effect on uptake. The reverse effect was observed in the ferrichrome series, where uptake decreased in the order of ferrichrysin, asperchrome D1, asperchrome B1, and ferrirubin. Configuration of the anhydromevalonyl group (cis or trans) in ferrichromes was also an important determinant in the recognition process. On the basis of uptake and inhibition studies, it is proposed that in ferrichromes part of the molecule (iron configuration and the N-acyl groups) is responsible for binding, whereas another (cyclic peptide ring) is involved in the subsequent process of transport. 相似文献
6.
白细胞介素-2中枢镇痛作用途径的探讨 总被引:3,自引:0,他引:3
抗IL-2受体α亚基的单克隆抗体不能阻断IL-2的中枢镇痛作用,以及丧失与IL-2受体β亚基结合能力的IL-2突变体仍具有提高大鼠痛阈的能力,这表明IL-2的中枢镇痛作用并不是通过IL-2受体所介导,亦表示IL-2的免疫和镇痛作用是通过不同的受体途径实现的。加之内源性阿片肽与IL-2分子有着共同的抗原决定基和结构相似性,提示IL-2可以与阿片受体直接结合产生中枢镇痛效应。从放射免疫法测定的IL-2侧脑室注射后不同时间大鼠脑内不同核团的内源性阿片肽含量,推测IL-2的中枢镇痛作用可能还与弓状核、室旁核、蓝斑等核团的β-EP和LEK有关。 相似文献
7.
Monitoring the persistence of Laccaria bicolor as an ectomycorrhizal symbiont of nursery-grown Douglas fir by PCR of the rDNA intergenic spacer 总被引:2,自引:0,他引:2
B. HENRION C. DI BATTISTA D. BOUCHARD D. VAIRELLES B. D. THOMPSON † F. LE TACON F. MARTIN 《Molecular ecology》1994,3(6):571-580
The large-scale inoculation of selected beneficial ectomycorrhizal fungi in forest nurseries has generated renewed interest in the ecology of these symbiotic fungi. However, information on the dissemination and persistence of introduced symbionts is scarce due to the limitation of the current identification methods. To identify ectomycorrhizal fungi on single root tips, we investigated the polymorphism of the PCR-amplified ribosomal DNA intergenic spacer (IGS) from a wide range of ectomycorrhizal fungi. To investigate the reliability of this molecular approach in large-scale surveys, the dissemination and persistence on Douglas fir seedlings of the introduced Laccaria bicolor S238N were assessed in a forest nursery in the Massif Central (France). Several hundred ectomycorrhizas and fruiting bodies were sampled from plots where control and L. bicolor inoculated-Douglas fir seedlings were grown for 1.5 years. PCR typing of mycorrhizas indicated that trees inoculated with L. bicolor S238N remained exclusively colonized by that isolate (or sexually derived isolates) for the entire test period. In contrast, control seedlings were infected by indigenous isolates of Laccaria laccata and Thelephora terrestris. The molecular evidence for the persistence of the introduced mycobiont despite the competition from indigenous isolates of the same species provides further illustration of the potential of exotic species for large-scale microbial application. 相似文献
8.
Zhang Yi Liang Yi Han Jing Hu Xiaohui Li Xiaojing Zhao Hailiang Bai Longqiang Shi Yu Ahammed Golam Jalal 《Journal of Plant Growth Regulation》2023,42(1):376-389
Journal of Plant Growth Regulation - Photoperiod and micronutrient iron (Fe) are critical for plant growth and development. However, the interactive effects of Fe nutrition and photoperiod on... 相似文献
9.
10.