全文获取类型
收费全文 | 151篇 |
免费 | 2篇 |
专业分类
化学 | 121篇 |
力学 | 2篇 |
数学 | 15篇 |
物理学 | 15篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 16篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有153条查询结果,搜索用时 15 毫秒
51.
Kerst Thomas Sand Johan Ihantola Sakari Peräjärvi Kari Nicholl Adrian Hrnecek Erich Toivonen Harri Toivonen Juha 《Optical Review》2018,25(3):429-436
Optical Review - This paper presents the remote detection of alpha contamination in a nuclear facility. Alpha-active material in a shielded nuclear radiation containment chamber has been localized... 相似文献
52.
Sauli Vuoti Riku Talja Leena-Sisko Johansson Harri Heikkinen Tekla Tammelin 《Cellulose (London, England)》2013,20(5):2359-2370
In this study we have manufactured nanofibrillar cellulose and modified the fibre surface with ester groups in order to hydrophobise the surface. Nanofibrillated cellulose was chosen to demonstrate the phenomena, since due to its high surface area the effects at issue are pronounced. The prepared NFC ester derivatives were butyrate, hexanoate, benzoate, naphtoate, diphenyl acetate, stearate and palmitate. X-ray photoelectron spectroscopy, solid state NMR and contact angle measurements were used to demonstrate the chemical changes taking place on the cellulose surface. NFC ester derivatives can be prepared after a careful solvent exchange to a water-free solvent medium has been carried out. Butyl and palmitoyl esters were chosen for film forming tests due to the difference in their carbon chain lengths, and their contact angles and water vapour and oxygen permeation rates were studied. The prepared nanocellulose esters show increased hydrophobicity even at very low levels of substitution and readily form films when the films are prepared from acetone dispersions. The permeation rates suggest a potential use as barrier materials. 相似文献
53.
Kari Kopra Alessio Ligabue Qi Wang Markku Syrjänpää Olga Blaževitš Stefan Veltel Arjan J. van Adrichem Pekka Hänninen Daniel Abankwa Harri Härmä 《Analytical and bioanalytical chemistry》2014,406(17):4147-4156
A quenching resonance energy transfer (QRET) assay for small GTPase nucleotide exchange kinetic monitoring is demonstrated using nanomolar protein concentrations. Small GTPases are central signaling proteins in all eukaryotic cells acting as a “molecular switches” that are active in the GTP-state and inactive in the GDP-state. GTP-loading is highly regulated by guanine nucleotide exchange factors (GEFs). In several diseases, most prominently cancer, this process in misregulated. The kinetics of the nucleotide exchange reaction reports on the enzymatic activity of the GEF reaction system and is, therefore, of special interest. We determined the nucleotide exchange kinetics using europium-labeled GTP (Eu-GTP) in the QRET assay for small GTPases. After GEF catalyzed GTP-loading of a GTPase, a high time-resolved luminescence signal was found to be associated with GTPase bound Eu-GTP, whereas the non-bound Eu-GTP fraction was quenched by soluble quencher. The association kinetics of the Eu-GTP was measured after GEF addition, whereas the dissociation kinetics could be determined after addition of unlabeled GTP. The resulting association and dissociation rates were in agreement with previously published values for H-RasWt, H-RasQ61G, and K-RasWt, respectively. The broader applicability of the QRET assay for small GTPases was demonstrated by determining the kinetics of the Ect2 catalyzed RhoAWt GTP-loading. The QRET assay allows the use of nanomolar protein concentrations, as more than 3-fold signal-to-background ratio was achieved with 50 nM GTPase and GEF proteins. Thus, small GTPase exchange kinetics can be efficiently determined in a HTS compatible 384-well plate format. Figure
? 相似文献
54.
The problem of computing Pareto optimal solutions with distributed algorithms is considered inn-player games. We shall first formulate a new geometric problem for finding Pareto solutions. It involves solving joint tangents
for the players' objective functions. This problem can then be solved with distributed iterative methods, and two such methods
are presented. The principal results are related to the analysis of the geometric problem. We give conditions under which
its solutions are Pareto optimal, characterize the solutions, and prove an existence theorem. There are two important reasons
for the interest in distributed algorithms. First, they can carry computational advantages over centralized schemes. Second,
they can be used in situations where the players do not know each others' objective functions. 相似文献
55.
Combination of the enantioselective properties of the two versatile gas-chromatographic chiral stationary phases (CSPs) octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-gamma-CD (Lipodex E) 1 and L-valine-diamide-based CSP Chirasil-Val-C11 2 has been realized by doping the chiral polymer 2 with the nonpolymeric selector 1. The resulting mixed-mode CSP Chirasil-Val(gamma-Dex) 3 was found to have a greatly improved enantioselectivity toward proline and aspartic acid (as N-trifluoroacetyl ethyl or methyl esters) in comparison to the single-mode CSP 2. The presence of the CD selector in 3 extended the scope of gas-chromatographic enantioseparations achievable on 2 to underivatized alcohols, terpenes, and other chiral compounds that are exclusively enantioseparated on 1. 相似文献
56.
Natalia Tong-Ochoa Kari Kopra Markku Syrjänpää Nicolas Legrand Harri Härmä 《Analytica chimica acta》2015
Protein post-translational modifications (PTMs) are regulatory mechanisms carried out by different enzymes in a cell. Kinase catalyzed phosphorylation is one of the most important PTM affecting the protein activity and function. We have developed a single-label quenching resonance energy transfer (QRET) assay to monitor tyrosine phosphorylation in a homogeneous high throughput compatible format. Epidermal growth factor receptor (EGFR) induced phosphorylation was monitored using Eu3+-chelate labeled peptide and label-free phosphotyrosine specific antibody in presence of a soluble quencher molecule. In the QRET kinase assay, antibody binding to phosphorylated Eu3+-peptide protects the Eu3+-chelate from luminescence quenching, monitoring high time-resolved luminescence (TRL) signals. In the presence of specific kinase inhibitor, antibody recognition and Eu3+-chelate protection is prevented, allowing an efficient luminescence quenching. The assay functionality was demonstrated with a panel of EGFR inhibitors (AG-1478, compound 56, erlotinib, PD174265, and staurosporine). The monitored IC50 values ranged from 0.08 to 155.3 nM and were comparable to those found in the literature. EGFR activity and inhibition assays were performed using low nanomolar enzyme and antibody concentration in a 384-well plate format, demonstrating its compatibility for high throughput screening (HTS). 相似文献
57.
Liedert R Amundsen LK Hokkanen A Mäki M Aittakorpi A Pakanen M Scherer JR Mathies RA Kurkinen M Uusitalo S Hakalahti L Nevanen TK Siitari H Söderlund H 《Lab on a chip》2012,12(2):333-339
We present a high-throughput roll-to-roll (R2R) manufacturing process for foil-based polymethyl methacrylate (PMMA) chips of excellent optical quality. These disposable, R2R hot embossed microfluidic chips are used for the identification of the antibiotic resistance gene mecA in Staphylococcus epidermidis. R2R hot embossing is an emerging manufacturing technology for polymer microfluidic devices. It is based on continuous feeding of a thermoplastic foil through a pressurized area between a heated embossing cylinder and a blank counter cylinder. Although mass fabrication of foil-based microfluidic chips and their use for biological applications were foreseen already some years ago, no such studies have been published previously. 相似文献
58.
We present a method for numerical computation of conformal mappings from simply or doubly connected domains onto so-called canonical domains, which in our case are rectangles or annuli. The method is based on conjugate harmonic functions and properties of quadrilaterals. Several numerical examples are given. 相似文献
59.
Harri Nyrhinen 《Journal of Theoretical Probability》2009,22(1):1-17
Let {S
n
;n=1,2,…} be a random walk in R
d
and E(S
1)=(μ
1,…,μ
d
). Let a
j
>μ
j
for j=1,…,d and A=(a
1,∞)×⋅⋅⋅×(a
d
,∞). We are interested in the probability P(S
n
/n∈A) for large n in the case where the components of S
1 are heavy tailed. An objective is to associate an exact power with the aforementioned probability. We also derive sharper
asymptotic bounds for the probability and show that in essence, the occurrence of the event {S
n
/n∈A} is caused by large single increments of the components in a specific way.
相似文献
60.
The effect of base sequence on the stability of the transition state (TS) of phosphodiester bond cleavage within linear single-stranded oligoribonucleotides has been studied in order to better understand why the reactivity of some phosphodiester bonds is enhanced compared to an unconstrained linkage. Molecular dynamics simulations of 3.0 ns were carried out for 14 oligonucleotides that contain in the place of the scissile phosphodiester bond a phosphorane structure mimicking the TS of the bond cleavage. The hydrolytic stability of the same oligonucleotides had previously been reported. Both the non-bridging oxyanions and the leaving 5[prime or minute]-oxygen of the pentacoordinated phosphorane moiety were observed to form hydrogen bonds with solvent water molecules in a similar way with all the compounds studied. In addition, water mediated hydrogen bonds between the phosphorane non-bridging oxyanions and the bases of the 3[prime or minute]-flanking sequence were detected with some of the compounds, but not with the most labile ones. Hence, it seems that the enhanced cleavage of some internucleosidic linkages does not result from the TS stabilisation by hydrogen bonding. With heterooligomers, the stacking of bases next to the cleavage site was observed to be enhanced on going from the initial state to the TS, whereas within uracil homooligomer, having initially negligible stacking, no change in the magnitude of stacking was seen. Accordingly, while strong stacking in the initial state is known to retard the phosphodiester bond cleavage, it may in the TS accelerate the reaction. Therefore, enhanced stacking on going from the initial state to transition state appears to be a factor that markedly contributes to the hydrolytic stability of phosphodiester bonds within oligonucleotides and may, at least partly, explain accelerated cleavage compared to fully unconstrained bonds, such as those in polyuridylic acid. 相似文献