全文获取类型
收费全文 | 643篇 |
免费 | 58篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 31篇 |
2015年 | 53篇 |
2014年 | 32篇 |
2013年 | 49篇 |
2012年 | 60篇 |
2011年 | 75篇 |
2010年 | 43篇 |
2009年 | 34篇 |
2008年 | 35篇 |
2007年 | 47篇 |
2006年 | 36篇 |
2005年 | 42篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 17篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1987年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有701条查询结果,搜索用时 15 毫秒
681.
Georgiana Petrareanu Mihaela C. Balasu Andrei M. Vacaru Cristian V. A. Munteanu Aura E. Ionescu Iulia Matei Stefan E. Szedlacsek 《Applied microbiology and biotechnology》2014,98(18):7855-7867
Phosphoketolases (PKs) are large thiamine pyrophosphate (TPP)-dependent enzymes playing key roles in a number of essential pathways of carbohydrate metabolism. The putative PK genes of Lactococcus lactis (Ll) and Leuconostoc mesenteroides (Lm) were cloned in a prokaryotic vector, and the encoded proteins were expressed and purified yielding high purity proteins termed PK-Ll and PK-Lm, respectively. Similarly, the PK gene of Pseudomonas aeruginosa was expressed, and the corresponding protein (PK-Pa) was purified to homogeneity. The amino acid sequences predicted on the basis of genes’ nucleotide sequences were confirmed by mass spectrometry and display low relative similarities. Circular dichroism (CD) spectra of these proteins predict higher α-helix than β-strand contents. In addition, it is predicted that PK-Ll contains tightly packed domains. Enzymatic analysis showed that all three recombinant proteins, despite their dissimilar amino acid sequences, are active PKs and accept both xylulose 5-phosphate (X5P) and fructose 6-phosphate (F6P) as substrates. However, they display substantially higher preference for X5P than for F6P. Kinetic measurements indicated that PK-Pa has the lowest K m values for X5P and F6P suggesting the highest capacity for substrate binding. PK-Ll has the largest k cat values for both substrates. Nevertheless, in terms of substrate specificity constant, PK-Pa has been found to be the most active PK against X5P. Structural models for all three analysed PKs predict similar folds in spite of amino acid sequence dissimilarities and contribute to understanding the enzymatic peculiarities of PK-Pa compared to PK-Ll and PK-Lm. 相似文献
682.
Luciana Stanica Mihaela Gheorghiu Miruna Stan Cristina Polonschii Sorin David Dumitru Bratu 《Journal of enzyme inhibition and medicinal chemistry》2017,32(1):1079-1090
Carbonic anhydrase IX (CA IX) is an important orchestrator of hypoxic tumour environment, associated with tumour progression, high incidence of metastasis and poor response to therapy. Due to its tumour specificity and involvement in associated pathological processes: tumourigenesis, angiogenesis, inhibiting CA IX enzymatic activity has become a valid therapeutic option. Dynamic cell-based biosensing platforms can complement cell-free and end-point analyses and supports the process of design and selection of potent and selective inhibitors. In this context, we assess the effectiveness of recently emerged CA IX inhibitors (sulphonamides and sulphocoumarins) and their antitumour potential using an electrical impedance spectroscopy biosensing platform. The analysis allows discriminating between the inhibitory capacities of the compounds and their inhibition mechanisms. Microscopy and biochemical assays complemented the analysis and validated impedance findings establishing a powerful biosensing tool for the evaluation of carbonic anhydrase inhibitors potency, effective for the screening and design of anticancer pharmacological agents. 相似文献
683.
Survival in northern microrefugia in an endemic Carpathian gammarid (Crustacea: Amphipoda)
下载免费PDF全文
![点击此处可从《Zoologica scripta》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Denis Copilaş‐Ciocianu Alina‐Andreea Zimţa Michał Grabowski Adam Petrusek 《Zoologica scripta》2018,47(3):357-372
Gammarus leopoliensis (Crustacea: Amphipoda) is considered a north‐eastern Carpathian endemic species and therefore can be regarded as an appropriate model for testing the hypothesis of Quaternary glacial survival in northern microrefugia. However, 250 km south, the south‐western Carpathians harbour populations that resemble phenotypically both G. leopoliensis and Gammarus kischineffensis, a similar species distributed east of the Carpathians. We used maximum‐likelihood and Bayesian methods to evaluate the phylogenetic relationships of these three taxa based on mitochondrial and nuclear markers, and quantitatively compared diversity patterns, phylogeography and divergence times among north‐eastern and south‐western Carpathian taxa. Results indicate that G. leopoliensis and the south‐western populations form together a strongly supported group (G. leopoliensis s.l.) which, along with G. kischineffensis, belongs to the Gammarus balcanicus clade. This group contains 12 lineages mainly of Pliocene age. G. leopoliensis consists of two widely distributed and recently expanded allopatric sister lineages that diverged from the southern ones ca. 4 Ma, indicating long‐term survival in northern microrefugia. The southern lineages are micro‐endemic and display a scattered distribution, suggesting a more ancient, relict pattern. We conclude that the contrasting diversity patterns between the disjunct distributional areas of G. leopoliensis s.l. reflect differential survival of lineages across the latitudinal gradient, offering a promising system for comparing the evolutionary ecology of lineages persisting in latitudinally disconnected microrefugia. These results fill an important gap in the knowledge of European gammarid biogeography and reveal that all Carpathian Gammarus taxa are ancient and diverse species complexes. 相似文献
684.
685.
The white-rot fungus Trametes versicolor decolorized Amaranth. The hypothesis that the carbon structure of Amaranth was broken down in smaller mass fragments was
investigated analyzing the products of decoloration. FTIR spectroscopy, ion chromatography, sulfite and ammonia analysis were
used to compare the culture filtrate before dye addition, with the pure dye, the culture filtrate after dye addition, and
the culture filtrate during the treatment. The hypothesis of polymerization of the decoloration products was tested by spectrophotometric
analysis of dialysates of the pure dye, the culture filtrate before dye addition, and the culture filtrates after dye addition
and decoloration. FTIR showed that the signals typical for the azo group disappeared after decoloration, while new peaks appeared
that were characteristic of substituted naphthalenic or benzenic compounds. Ion chromatography showed that the level of sulfate
in the treatment increased when compared with the level of the sulfate in control, suggesting that the sulfonic groups were
being stripped from Amaranth’s structure and metabolized to sulfate. Sulfite measurements for the treatment and controls showed
no significant difference, and were well below the saturation concentration for sulfite in water, confirming that the medium
was aerobic. Ammonia concentration did not change with the decoloration. Absorbance scans after dialysis of decolorized samples
showed no new peaks, suggesting that the decoloration products were not polymerized. These observations suggests that the
decoloration mechanism starts with the azo link removal, followed by desulfonation, naphthalene ring opening, and the formation
of smaller mass fragments, similar to fungal metabolites. 相似文献
686.
The evolution of omics and computational competency has accelerated discoveries of the underlying biological processes in an unprecedented way. High throughput methodologies, such as flow cytometry, can reveal deeper insights into cell processes, thereby allowing opportunities for scientific discoveries related to health and diseases. However, working with cytometry data often imposes complex computational challenges due to high-dimensionality, large size, and nonlinearity of the data structure. In addition, cytometry data frequently exhibit diverse patterns across biomarkers and suffer from substantial class imbalances which can further complicate the problem. The existing methods of cytometry data analysis either predict cell population or perform feature selection. Through this study, we propose a “wisdom of the crowd” approach to simultaneously predict rare cell populations and perform feature selection by integrating a pool of modern machine learning (ML) algorithms. Given that our approach integrates superior performing ML models across different normalization techniques based on entropy and rank, our method can detect diverse patterns existing across the model features. Furthermore, the method identifies a dynamic biomarker structure that divides the features into persistently selected, unselected, and fluctuating assemblies indicating the role of each biomarker in rare cell prediction, which can subsequently aid in studies of disease progression. 相似文献
687.
688.
Mihaela Kavran Igor Pajović Dušan Petrić Aleksandra Ignjatović-Ćupina Nedeljko Latinović Miomir Jovanović Stephen Alexander Quarrie Marija Zgomba 《Entomologia Experimentalis et Applicata》2020,168(2):148-157
Aquatain® mosquito formulation (AMF) is a silicone-based monomolecular film, which has recently been approved for use in the European Union. The physical mode of action based on lowering water surface tension prevents mosquito larvae/pupae respiration. Additionally, AMF disables gravid females from landing on the water surface and obstructs the natural oviposition process. Due to multistage effects on mosquitoes, AMF could be a product of choice for defined water body and container breeders such as Culex pipiens L. complex, principal vector of West Nile virus in Europe, and the invasive Aedes albopictus (Skuse) (both Diptera: Culicidae), vector of dengue and chikungunya viruses. The primary objectives of this study were to evaluate the efficacy of AMF, to determine the susceptibility of the immature forms of C. pipiens and A. albopictus, and the persistence/longevity of the product to suppress the eclosion of adults. AMF achieved high mortality rates of juvenile A. albopictus and C. pipiens under laboratory conditions. However, in the field C. pipiens larvae showed higher susceptibility to AMF than A. albopictus. Pupae of the two mosquito species were highly susceptible to the presence of AMF. When C. pipiens juveniles were exposed to AMF in the wild, effects lasted for 21 days in densely covered water bodies and 56 days in water recipients with less vegetation. In both breeding sites, natural habitat and artificial water recipient, the two mosquito species with high impact on public health in Europe could successfully be suppressed by application of AMF (1 ml m−2). 相似文献
689.
690.
Mihaela Škulj Veronika Okršlar Špela Jalen Simona Jevševar Petra Slanc Borut Štrukelj Viktor Menart 《Microbial cell factories》2008,7(1):6