全文获取类型
收费全文 | 1213篇 |
免费 | 117篇 |
出版年
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 39篇 |
2017年 | 27篇 |
2016年 | 44篇 |
2015年 | 77篇 |
2014年 | 62篇 |
2013年 | 92篇 |
2012年 | 101篇 |
2011年 | 77篇 |
2010年 | 42篇 |
2009年 | 51篇 |
2008年 | 54篇 |
2007年 | 62篇 |
2006年 | 57篇 |
2005年 | 42篇 |
2004年 | 27篇 |
2003年 | 27篇 |
2002年 | 29篇 |
2001年 | 27篇 |
2000年 | 31篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 10篇 |
1993年 | 11篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1966年 | 4篇 |
1961年 | 5篇 |
排序方式: 共有1330条查询结果,搜索用时 15 毫秒
131.
Although the chemical nature of the catalytic mechanism of the serine protease alpha-chymotrypsin (alpha-CT) is largely understood, the influence of the enzyme's structural dynamics on its catalysis remains uncertain. Here we investigate whether alpha-CT's structural dynamics directly influence the kinetics of enzyme catalysis. Chemical glycosylation [Solá RJ & Griebenow K (2006) FEBS Lett 580, 1685-1690] was used to generate a series of glycosylated alpha-CT conjugates with reduced structural dynamics, as determined from amide hydrogen/deuterium exchange kinetics (k(HX)). Determination of their catalytic behavior (K(S), k(2), and k(3)) for the hydrolysis of N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) revealed decreased kinetics for the catalytic steps (k(2) and k(3)) without affecting substrate binding (K(S)) at increasing glycosylation levels. Statistical correlation analysis between the catalytic (DeltaG( not equal)k(i)) and structurally dynamic (DeltaG(HX)) parameters determined revealed that the enzyme acylation and deacylation steps are directly influenced by the changes in protein structural dynamics. Molecular modelling of the alpha-CT glycoconjugates coupled with molecular dynamics simulations and domain motion analysis employing the Gaussian network model revealed structural insights into the relation between the protein's surface glycosylation, the resulting structural dynamic changes, and the influence of these on the enzyme's collective dynamics and catalytic residues. The experimental and theoretical results presented here not only provide fundamental insights concerning the influence of glycosylation on the protein biophysical properties but also support the hypothesis that for alpha-CT the global structural dynamics directly influence the kinetics of enzyme catalysis via mechanochemical coupling between domain motions and active site chemical groups. 相似文献
132.
Gérard Coureaud Rachel Charra Frédérique Datiche Charlotte Sinding Thierry Thomas-Danguin Solène Languille Bernard Hars Benoist Schaal 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2010,196(10):779-790
Birth is part of a continuum and is a major developmental change. Newborns need to adapt rapidly to the environment in terms
of physiology and behaviour, and ability to locate the maternal source of milk is vital. Mechanisms have evolved resulting
in the emission of olfactory cues by the mother and the processing of these cues by the young. Here, we focus on some sensory,
cognitive and behavioural strategies developed by the European rabbit (Oryctolagus cuniculus) that optimize the early development of offspring. In this species, chemosensory communication between the mother and young
plays a critical role in eliciting adaptive neonatal responses. In particular, lactating females release a molecule, the mammary
pheromone, which has several functional impacts. It triggers orocephalic responses involved in the quick localization of nipples
and sucking. Moreover, this unconditioned signal promotes rapid appetitive learning of novel odorants, acting as a potent
organizer of neonatal cognition. The mammary-pheromone-induced odour memory requires consolidation/reconsolidation processes
to be maintained in the long term. Finally, as this mode of conditioning also promotes learning of mixtures of odorants, it
supports investigations related to the capacity of neonatal olfaction to extract biological value from the complex environment. 相似文献
133.
Viviana G. Solís Neffa 《Plant Systematics and Evolution》2010,284(3-4):231-253
With the objective of contributing to understanding the patterns of variation within the Turnera sidoides complex, a detailed evaluation of morphological variation along the range of T. sidoides subsp. pinnatifida was performed. A multivariate analysis based on leaf traits and flower colour data enabled differentiation of five morphotypes. Common-garden experiments demonstrated that the morphological variants have a strong genetic basis. It was also found that the morphotypes are geographically structured along the subspecies range, display different habitat preferences, and occur in regions with different climatic regimes. Although these results are suggestive of adaptive differentiation of T. sidoides subsp. pinnatifida, comparisons between morphological and bioclimatic ordinations showed that the patterns observed cannot be fully explained by current climatic conditions. It is proposed that Miocene–Pleistocene events may explain the origin of the five morphotypes and that current climatic and ecological factors may be contributing to the maintenance of the extent and patterns of morphological differentiation in T. sidoides subsp. pinnatifida. 相似文献
134.
135.
SNPStats: a web tool for the analysis of association studies 总被引:4,自引:0,他引:4
136.
Self-excision of the antibiotic resistance gene nptII using a heat inducible Cre-loxP system from transgenic potato 总被引:5,自引:0,他引:5
Cuellar W Gaudin A Solórzano D Casas A Nopo L Chudalayandi P Medrano G Kreuze J Ghislain M 《Plant molecular biology》2006,62(1-2):71-82
Resistance to antibiotics mediated by selectable marker genes remains a powerful selection tool for transgenic event production. However, regulatory agencies and consumer concerns favor these to be eliminated from food crops. Several excision systems exist but none have been optimized or shown to be functional for clonally propagated crops. The excision of the nptII gene conferring resistance to kanamycin has been achieved here using a gene construct based on a heat-inducible cre gene producing a recombinase that eliminates cre and nptII genes flanked by two loxP sites. First-generation regenerants with the Cre-loxP system were obtained by selection on kanamycin media. Following a heat treatment, second generation regenerants were screened for excision by PCR using nptII, cre, and T-DNA borders primers. Excision efficiency appeared to be at 4.7% depending on the heat treatment. The footprint of the excision was shown by sequencing between T-DNA borders to correspond to a perfect recombination event. Selectable marker-free sprouts were also obtained from tubers of transgenic events when submitted to similar heat treatment at 4% frequency. Spontaneous excision was not observed out of 196 regenerants from untreated transgenic explants. Biosafety concerns are minimized because the expression of cre gene driven by the hsp70 promoter of Drosophila
melanogaster was remarkably low even under heat activation and no functional loxP site were found in published Solanum sequence database. A new plant transformation vector pCIP54/55 was developed including a multiple cloning site and the self-excision system which should be a useful tool not only for marker genes in potato but for any gene or sequence removal in any plant. 相似文献
137.
Are network motifs the spandrels of cellular complexity? 总被引:1,自引:0,他引:1
Cellular networks display modular organization at different levels, from small sets of genes exchanging signals in morphogenesis to large groups of proteins involved in cell death. At the smallest scale, minute groups of interacting proteins or genes, so-called 'network motifs', have been suggested to be the functional building blocks of network biology. In this context, the relative abundance of a network motif would reflect its adaptive value. However, although the overabundance of motifs is non-random, recent studies by Mazurie et al. and by Kuo et al. show that motif abundance does not reflect their true adaptive value. Just as some architectural components emerge as a byproduct of a prior decision, common motifs might be a side effect of inevitable rules of genome growth and change. 相似文献
138.
A randomised controlled trial to evaluate a training programme for physician-patient communication required the analysis of paired count data. The impact of departures from the Poisson assumption when paired count data are analysed through use of a conditional likelihood is illustrated. A simple approach to providing robust inference is outlined and illustrated. 相似文献
139.
Solórzano C Bouquelet S Pereyra MA Blanco-Favela F Slomianny MC Chavez R Lascurain R Zenteno E Agundis C 《Glycoconjugate journal》2006,23(7-8):591-598
Neutrophils participate in host protection and central to this process is the regulation of oxidative mechanisms. We purified
by affinity chromatography the receptor for the GlcNAc-specific WGA from CD14+ CD16+ cell lysates (WGAr). The receptor is
a 141 kDa glycoprotein constituted by two subunits of 78 and 63 kDa. It is mainly composed of Ser, Asx, and Gly, and, in a
minor proportion, His, Cys, and Pro. Its glycan portion contains GlcNAc, Gal, and Man; NeuAc and GalNAc were identified in
a minor proportion. The amino acid sequence of the WGA receptor was predicted from tryptic peptides by MALDI-TOF, both subunits
showed homology with cytokeratin type II (26 and 29% for the 78 and 63 kDa subunits, respectively); the 78 kDa subunit showed
also homology with the human transferrin receptor (24%). Antibodies against WGAr induce higher oxidative burst than WGA, determined
by NBT reduction; however, this effect was inhibited (p < 0.05) with GlcNAc suggesting that WGAr participates as mediator in signal transduction in neutrophils. 相似文献
140.
Mönica M. Solórzano Kraemer 《Pal?ontologische Zeitschrift》2006,80(2):107-111
Eohomopterus simojovelensis n. sp., the first fossil record of the subfamily Paussinae (Coleoptera: Carabidae) from the Miocene amber of the Simojovel
area, Chiapas, Mexico, is described. The morphology of the new species is compared withEohomopterus poinari
Nagel, 1997 from Dominican amber as well as with extant representatives ofEohomopterus, and the biogeographical implications are discussed.
相似文献