全文获取类型
收费全文 | 640篇 |
免费 | 58篇 |
出版年
2023年 | 4篇 |
2022年 | 10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698条查询结果,搜索用时 31 毫秒
671.
Asbeck Thomas Kozk Daniel Spnu Andreea P. Mikol Martin Zemlerov Veronika Svoboda Miroslav 《Ecosystems》2022,25(3):712-726
Ecosystems - The impact of forest management on biodiversity is difficult to scrutinize along gradients of management. A step towards analyzing the impact of forest management on biodiversity is... 相似文献
672.
Eric J. Horstick Diana C. Jordan Sadie A. Bergeron Kathryn M. Tabor Mihaela Serpe Benjamin Feldman Harold A. Burgess 《Nucleic acids research》2015,43(7):e48
Many genetic manipulations are limited by difficulty in obtaining adequate levels of protein expression. Bioinformatic and experimental studies have identified nucleotide sequence features that may increase expression, however it is difficult to assess the relative influence of these features. Zebrafish embryos are rapidly injected with calibrated doses of mRNA, enabling the effects of multiple sequence changes to be compared in vivo. Using RNAseq and microarray data, we identified a set of genes that are highly expressed in zebrafish embryos and systematically analyzed for enrichment of sequence features correlated with levels of protein expression. We then tested enriched features by embryo microinjection and functional tests of multiple protein reporters. Codon selection, releasing factor recognition sequence and specific introns and 3′ untranslated regions each increased protein expression between 1.5- and 3-fold. These results suggested principles for increasing protein yield in zebrafish through biomolecular engineering. We implemented these principles for rational gene design in software for codon selection (CodonZ) and plasmid vectors incorporating the most active non-coding elements. Rational gene design thus significantly boosts expression in zebrafish, and a similar approach will likely elevate expression in other animal models. 相似文献
673.
674.
Ana-Maria OpreaLenuta Profire Catalina Elena LupusoruCristina Mihaela Ghiciuc Diana CiolacuCornelia Vasile 《Carbohydrate polymers》2012,87(1):721-729
Mixed hydrogels based on natural, biodegradable and biocompatible polysaccharides, such as cellulose (C) and chondroitin sulphate (CS) in various mixing ratios were prepared by a crosslinking technique and characterized by swelling behaviour, FTIR spectroscopy, scanning electron microscopy, toxicity and biocompatibility tests.The mixed cellulose/chondroitin sulphate hydrogels have been loaded with 7-[2-nitroxiacetyl-oxy-3-(4-acetyl-amino-phenoxy)-propyl]-8-morpholino-1,3-dimethyl-xanthine, a novel nitric oxide donor compound with a lower toxicity and a higher anti-inflammatory activity than its parent molecules, paracetamol and theophylline. Swelling and release kinetics have been also studied. It has been established that an increase of CS content in hydrogels composition leads to a higher swelling ratio for all formulations and to a decreased released amount of nitric oxide donor compound. It has been found that the swelling occurs by an anomalous swelling mechanism, while the release of nitric oxide donor compound follows a diffusion controlled mechanism. 相似文献
675.
Mihaela Gheorghiu Andreea Olaru Aurelia Tar Cristina Polonschii Eugen Gheorghiu 《Biosensors & bioelectronics》2009,24(12):3517-3523
A new and exciting biosensing avenue based on assessment of the non-monotonous, concentration dependent effect of pore formation is discussed. A novel kinetic model is advanced to relate surface plasmon resonance (SPR) data with actual concentrations of interacting partners. Lipid modified L1 sensor chip provide the accessible platform for SPR exploration of peptide–membrane interaction, with POPC and melittin as model systems. We show that quantitative assessment of the interaction between an antimicrobial peptide and lipid modified sensors is capable to provide both sensing avenues and detailed mechanistic insights into effects of pore-forming compounds. The proposed model combined with appropriate design of the experimental protocol adds a new depth to the classic SPR investigation of peptide–lipid interaction offering a quantitative platform for detection, improved understanding of the manifold facets of the interaction and for supporting the controlled design of novel antimicrobial compounds. This biosensing approach can be applied to an entire set of pore-forming compounds including antimicrobial peptides and exo-toxins. 相似文献
676.
Mihaela C. Balasu Laurentiu N. Spiridon Simona Miron Constantin T. Craescu Axel J. Scheidig Andrei-Jose Petrescu Stefan E. Szedlacsek 《PloS one》2009,4(5)
The activity of ERK2, an essential component of MAP-kinase pathway, is under the strict control of various effector proteins. Despite numerous efforts, no crystal structure of ERK2 complexed with such partners has been obtained so far. PTP-SL is a major regulator of ERK2 activity. To investigate the ERK2–PTP-SL complex we used a combined method based on cross-linking, MALDI-TOF analysis, isothermal titration calorimetry, molecular modeling and docking. Hence, new insights into the stoichiometry, thermodynamics and interacting regions of the complex are obtained and a structural model of ERK2-PTP-SL complex in a state consistent with PTP-SL phosphatase activity is developed incorporating all the experimental constraints available at hand to date. According to this model, part of the N-terminal region of PTP-SL has propensity for intrinsic disorder and becomes structured within the complex with ERK2. The proposed model accounts for the structural basis of several experimental findings such as the complex-dissociating effect of ATP, or PTP-SL blocking effect on the ERK2 export to the nucleus. A general observation emerging from this model is that regions involved in substrate binding in PTP-SL and ERK2, respectively are interacting within the interface of the complex. 相似文献
677.
678.
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
679.
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
680.
Survival in northern microrefugia in an endemic Carpathian gammarid (Crustacea: Amphipoda) 下载免费PDF全文
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