全文获取类型
收费全文 | 174篇 |
免费 | 22篇 |
国内免费 | 91篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 7篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有287条查询结果,搜索用时 31 毫秒
1.
2.
粘虫幼虫血淋巴中的凝集素 总被引:5,自引:0,他引:5
粘虫Mythlmna separata Walker幼虫血淋巴中含有凝集某些脊椎动物红细胞的凝集素,凝集活性可被乳糖、岩藻糖或神经氨酸抑制.用CNBr-sepharose 4B 进行亲和层析从血淋巴中分离的凝集素成分比较复杂,聚丙烯酰胺凝胶电泳显示三条区带,SDS聚丙烯酰胺凝胶电泳出现6个亚基,亚基分子量分别为71000、65000、56000、35000、33000及31000道尔顿. 相似文献
3.
小地老虎及粘虫幼虫对灭幼脲表现自然耐药力的体壁结构和生化基础 总被引:2,自引:1,他引:1
小地老虎Agrotis ypsilon rottem.幼虫对灭幼脲具有一定的自然耐药力。本文以粘虫Mythimna separata(Walker)作为敏感性虫种与之进行比较,实验结果表明,灭幼脲对两种试虫的室内毒力相差4倍左右,引起差异的原因,在体壁结构方面主要在于:(1)小地老虎幼虫的表皮层较粘虫的厚4.2倍左右;(2)上表皮不是匀质结构,依靠少数蜡道与体表沟通;(3)几丁质片层内的孔道数较少,仅及粘虫的1/4。由此构成了表皮对疏水性的灭幼脲表现抗穿透的性能。小地老虎幼虫体壁还含有较强的生化防卫体系,灭幼脲对多功能氧化酶、芳基酰胺酶有明显激活效应,这两种酶都是灭幼脲的降解酶。由此认为,小地老虎幼虫对灭幼脲所表现的自然耐药力,是由体壁的抗穿透性能以及由灭幼脲所激活的适应酶所造成。 相似文献
4.
Conserved sequence motifs in the unorthodox BvgS two-component sensor protein ofBordetella pertussis
The unorthodox two-component sensor protein BvgS ofBordetella pertussis contains several interesting sequence motifs of unknown functional relevance, such as a histidine motif in its output domain, which is conserved among several unorthodox sensor proteins, a putative nucleotide binding site [Walker box type A] in its linker region, and a region in its periplasmic domain with significant homology to the TonB protein ofEscherichia coli. We investigated potential functions of these sequences by constructingB. pertussis strains that express mutant BvgS derivatives. The His1172 residue in the output domain was exchanged for Gln, and the Walker motif was mutated either by the replacement of Lys625 by Arg, or of Gly624 by Val and Lys625 by Leu. To analyse the TonB motif, the periplasmic domain of BvgS was replaced with the corresponding domain of EvgS, anE. coli sensor that is highly homologous to BvgS but lacks the similarity with TonB. All mutations except the conservative Lys/Arg exchange in the Walker box caused the inactivation of BvgS, indicating the functional importance of the conserved motifs. The activity of the mutant proteins could be restored by complementation in trans with various separately expressed, truncated parts of BvgS. Mutations in the BvgS receiver domain could be complemented not only by a construct expressing the wild-type receiver and output domains, but also by the derivative containing the His-Gln exchange. Therefore, the histidine motif, although important for BvgS function, is not essential for complementation of BvgS mutants. The mutations in the Walker box and in the periplasmic domain could be complemented by a truncated BvgS derivative lacking the receiver and output domains. The characterization of a spontaneous revertant of the strain expressing the originally inactive EvgS/BvgS hybrid protein revealed the presence of a mutation in the BvgS linker region, conferring constitutive activity on the protein. As TonB energizes transport processes across the outer membrane ofE. coli, the strain expressing the constitutive EvgS/BvgS hybrid protein lacking the TonB motif was used in preliminary investigations of a possible direct involvement of BvgS in transport processes. 相似文献
5.
根据Fuzzy数学原理和三化螟生物学特性,组建了四代三化螟发生动态综合预测模型经对福建省将乐县16年四代三化螟发生期、发生量回报及1995年的预报,拟合率及正确率均达100%。 相似文献
6.
温度对粘虫产生和释放性信息素规律的影响 总被引:1,自引:1,他引:0
在21℃饲养的粘虫雌蛾腺体提取物中Zll-16:Aid含量峰值时间是羽化后第8~9天;25℃是羽化后第4~5天,27℃是羽化后第3~4天。低温不仅推迟了粘虫雌蛾求偶和释放性信息素的时间,而且降低了腺体中性信息素的滴度。在27℃,粘虫雌蛾腺体中Zll-16:Ald峰值的平均值达15ng;在25℃时为10ng,而在21℃时,只有5ng。由此可见,低温环境明显抑制粘虫雌蛾的性发育,延缓了性成熟。 相似文献
7.
Abstract The fatty acid (FA) compositions for total lipids from fat body, hemolymph and flight muscle of the armyworm moths, Mythirnna separata, at rest and after tethered flight for 1 h were determined by GC and GC-MS. The composition in these tissues comprises myristic acid (1%-2%), palmitic acid (more than 35%1, palmitoleic acid (9%-11%), stearic acid (less than 1%), oleic acid (about 32%), linoleic acid (12%-17%) and linolenic acid (3%-6%). After flight, FA level in the fat body, compared to that at rest, shows a significant decline at about 20 μg/mg tissue.h-1; the concentration of FAs in hemolymph rises evidently, but change of FA content in flight muscle appears to be small. From the changes of proportional composition of FAs in fat body, hemolymph and flight muscle, it is found that the FAs selectively utilized for flight in flight muscle are predominantly the palmitic acid and oleic acid. 相似文献
8.
A. Beyer 《Protein science : a publication of the Protein Society》1997,6(10):2043-2058
The AAA protein family, a recently recognized group of Walker-type ATPases, has been subjected to an extensive sequence analysis. Multiple sequence alignments revealed the existence of a region of sequence similarity, the so-called AAA cassette. The borders of this cassette were localized and within it, three boxes of a high degree of conservation were identified. Two of these boxes could be assigned to substantial parts of the ATP binding site (namely, to Walker motifs A and B); the third may be a portion of the catalytic center. Phylogenetic trees were calculated to obtain insights into the evolutionary history of the family. Subfamilies with varying degrees of intra-relatedness could be discriminated; these relationships are also supported by analysis of sequences outside the canonical AAA boxes: within the cassette are regions that are strongly conserved within each subfamily, whereas little or even no similarity between different subfamilies can be observed. These regions are well suited to define fingerprints for subfamilies. A secondary structure prediction utilizing all available sequence information was performed and the result was fitted to the general 3D structure of a Walker A/GTPase. The agreement was unexpectedly high and strongly supports the conclusion that the AAA family belongs to the Walker superfamily of A/GTPases. 相似文献
9.
10.