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91.
Mirjam C. K. Geditz Georg Heinkele Asma Ahmed Peter G. Kremsner Reinhold Kerb Matthias Schwab Ute Hofmann 《Analytical and bioanalytical chemistry》2014,406(17):4299-4308
Artesunate (AS), a hemisuccinate derivative of artemisinin, is readily soluble in water and can easily be used in formulations for parenteral treatment of severe malaria. AS is rapidly hydrolyzed to the active metabolite dihydroartemisinin (DHA) and primarily eliminated by biliary excretion after glucuronidation. To investigate systematically the AS metabolism and pharmacokinetics, a novel liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of AS and its metabolites DHA and DHA glucuronide (DHAG) in human plasma samples was developed. Compared to previous methods, our method includes for the first time the quantification of the glucuronide metabolite using a newly synthesized stable isotope-labeled analogue as internal standard. Sample preparation was performed with only 50 μL plasma by high-throughput solid-phase extraction in the 96-well plate format. Separation of the analytes was achieved on a Poroshell 120 EC-C18 column (50*2.1 mm, 2.7 μm, Agilent Technologies, Waldbronn, Germany). The method was validated according to FDA guidelines. Calibration curves were linear over the entire range from 1 to 2,500 nM (0.4–961.1 ng/mL), 165 to 16,500 nM (46.9–4,691.8 ng/mL), and 4 to 10,000 nM (1.8–4,604.7 ng/mL) for AS, DHA, and DHAG, respectively. Intra- and interbatch accuracy, determined as a deviation between nominal and measured values, ranged from ?5.7 to 3.5 % and from 2.7 to 5.8 %, respectively. The assay variability ranged from 1.5 to 10.9 % for intra- and interbatch approaches. All analytes showed extraction recoveries above 85 %. The method was successfully applied to plasma samples from patients under AS treatment. Figure
Chemical structures and combined MRM chromatograms of the analytes AS, DHA and DHAG 相似文献
92.
The relatively narrow depth of field and long focal distance of the microscope are the basic facts on which the procedure is founded. To the microscope a videocamera is connected. As long as the adjustments of the microscope are unchanged and your recordings are made in focus you can compare sizes and determine the magnification factor and thus obtain real sizes. The maximal error of measurement is calculated: 4.65 ± 3.10%. 相似文献
93.
Christophe Barrera-Esteve Florent Bergeret Charles Dossal Emmanuel Gobet Asma Meziou Rémi Munos Damien Reboul-Salze 《Methodology and Computing in Applied Probability》2006,8(4):517-540
In the natural gas market, many derivative contracts have a large degree of flexibility. These are known as Swing or Take-Or-Pay options. They allow their owner to purchase gas daily, at a fixed price and according to a volume of their choice. Daily,
monthly and/or annual constraints on the purchased volume are usually incorporated. Thus, the valuation of such contracts
is related to a stochastic control problem, which we solve in this paper using new numerical methods. Firstly, we extend the
Longstaff–Schwarz methodology (originally used for Bermuda options) to our case. Secondly, we propose two efficient parameterizations
of the gas consumption, one is based on neural networks and the other on finite elements. It allows us to derive a local optimal
consumption law using a stochastic gradient ascent. Numerical experiments illustrate the efficiency of these approaches. Furthermore,
we show that the optimal purchase is of bang-bang type.
相似文献
94.
Kinetics of the sulfuric acid catalyzed esterification of palmitic acid with isobutyl alcohol has been studied and reviewed critically. A theoretical rate equation is derived by the following reaction mechanism: (1) The reaction of sulfuric acid and isobutyl alcohol produces isobutyl sulfuric acid which acts as a catalyst; (2) Palmitic acid is protonated by the catalyst to form the reaction intermediate; and (3) The esterification proceeds reversibly. The experimental results are consistent with this rate equation. 相似文献
95.
Hepatitis C virus (HCV) is a major health problem across the world affecting the people of all age groups. It is the main cause of hepatitis and at chronic stage causes liver cirrhosis and hepatocellular carcinoma. Various therapeutics are made against HCV but still there is a need to find out potential therapeutics to combat the virus. The goal of this study is to identify the phytochemicals of Azadirachta indica leaves having antiviral activity against HCV NS3 protease through molecular docking and simulation approach. Results show that the compound 3-Deacetyl-3-cinnamoyl-azadirachtin possesses good binding properties with HCV NS3/4A protease. It can be concluded from this study that Deacetyl-3-cinnamoyl-azadirachtin may serve as a potential inhibitor against NS3/4A protease. 相似文献
96.
Asma Balakrishna Kalluraya Nagaraja Manju Chigahally Lakshmegowda Sharath 《Journal of heterocyclic chemistry》2020,57(8):3105-3115
A novel series of 5-(p-(prop-2-ynyloxy)phenyl)-3-aryl-4,5-dihydropyrazole-1-carbothioamides 2a-f and functionalized 2-(3-(aryl)-5-(4-(prop-2-ynyloxy)phenyl)-4,5-dihydropyrazol-1-yl)-4-(3-arylsydnone-4-yl)thiazoles 4a-l were synthesized. The newly synthesized compounds were elucidated by analytical and spectral analysis. From the single-crystal X-ray diffraction method, it was observed that 2d crystallizes in a monoclinic crystal system with P21/n space group. The compounds 2d crystallized with cell parameters a = 15.0614 (19) Å, b = 6.0805 (7) Å, c = 20.903 (7) Å, α = 114.136 (6)o, β = 110.709 (14) o, γ = 96.553 (5) o, V = 1790.6 (4) Å3, Z = 4. From the Hirshfeld surface computational method, the major intercontacts present in these molecules are H…H (31.6%), C…H (18.2%) and S…H (12.2%), respectively. The newly synthesized compounds were tested for their ability to bleach 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical using DPPH scavenging assay. Among the synthesized compounds carbothioamide compounds 2c (90.7%) and 2b (89.8%) exhibited good DPPH scavenging activity compared to the rest of the compounds. Most of the synthesized carbothioamide molecules ( 2a-f ) found to be potent compared to the thiazole derivatives ( 4a-l ). 相似文献
97.
Differential scanning calorimetry (DSC) has many applications during preformulation screening of new drug candidates, but
definitive assignment of peaks to specific events in the sample is difficult without supplementary data from other techniques.
To some extent these problems can be overcome by running multiple experiments at different heating rates. Typically 2 and
20 °C min−1 are indicated. However, modern instruments are capable of achieving much faster heating rates (up to 750 °C commercially);
with this extended range comes a new capacity for investigating the physical form of materials. Here, the use of fast DSC
heating rates for materials characterisation is explored, focussing on determination of melting temperatures, glass formation
and polymorph screening. 相似文献
98.
Prof. Dr. Thomas C. Nugent Abdul Sadiq Ahtaram Bibi Prof. Dr. Thomas Heine Lei Liu Zeonjuk Dr. Nina Vankova Dr. Bassem S. Bassil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(13):4088-4098
Relying on the assembly of commercially available catalyst building blocks, highly stereocontrolled quaternary carbon (all carbon substituted) formation has been achieved with unmatched substrate diversity. For example, the in situ assembly of a tricomponent catalyst system allows α‐branched aldehyde addition to nitroalkene or maleimide electrophiles (Michael products), while addition to an α‐iminoester affords Mannich reaction products. Very good yields are observed and for fifteen of the eighteen examples 96–99 % ee is observed. Using racemic α‐branched aldehydes, two contiguous (quaternary–tertiary) stereogenic centers can be formed in high diastereo‐ and enantiomeric excess (eight examples) via an efficient in situ dynamic kinetic resolution, solving a known shortcoming for maleimide electrophiles in particular. The method is of practical value, requiring only 1.2 equiv of the aldehyde, a 5.0 mol % loading of each catalyst component, for example, O‐tBu‐L ‐threonine (O‐tBu‐L ‐Thr), sulfamide, DMAP or O‐tBu‐L ‐Thr, KOH, and room temperature reactions. As a highlight, the first demonstration of ethylisovaleraldehyde ( 7 ) addition is disclosed, providing the most congested quaternary stereogenic carbon containing succinimide product ( 8 ) known to date. Finally, mechanistic insight, via DFT calculations, support a noncovalent assembly of the catalyst components into a bifunctional catalyst, correctly predict two levels of product stereoselectivity, and suggest the origin of the tricomponent catalyst system’s exceptionality: an alternative hydrogen bond motif for the donor‐acceptor pair than currently suggested for non‐assembled catalysts. 相似文献
99.
Željka Jovanović Aleksandra Radosavljević Milorad Šiljegović Nataša Bibić Vesna Mišković-Stanković Zorica Kačarević-Popović 《Radiation Physics and Chemistry》2012,81(11):1720-1728
Silver nanoparticles (AgNPs) were synthesized in situ by γ-irradiation using poly(N-vinyl-2-pyrrolidone) (PVP) as a capping agent. The concentration, molecular weight and the structure (crosslinked and interpenetrated network) of PVP were varied, in order to determine the influence of the capping agent in the radiolytic synthesis of the Ag/PVP nanosystems. Transmission electron microscopy (TEM) showed that AgNPs obtained from the solutions containing higher PVP concentration and higher molecular weight were spherical in shape, with narrow size distribution and a diameter of~6 nm, while slightly larger rod-shaped silver agglomerates, with bimodal nanoparticle size distribution and diameters of ~10 nm and ~20 nm were obtained from the solutions containing lower PVP concentration and lower molecular weight. Strong plasmon coupling and extending of plasmon resonance was observed by UV–vis spectroscopy, as a result of formation of nanorod-like agglomerates. Crosslinked and interpenetrated network did not affect the structure of synthesized AgNPs. Ag/PVP nanocomposite, in the form of thin film, was obtained by solvent evaporation from Ag/PVP colloid solution with 10 wt% of PVP, and characterized by FTIR spectroscopy. The interactions in Ag/PVP nanocomposite are shown to be the result of the coordination bonding between AgNPs and nitrogen from pyrrolidone ring of PVP. The optical properties of investigated Ag/PVP nanosystems, as measured by the values of optical band gap, Eg, are mainly the consequence of the interparticle distance as a result of the concentration and the structure of surrounding PVP macromolecules. 相似文献
100.
We have investigated theoretically a feasible nuclear reaction to produce light double-Λ hypernuclei by choosing a suitable target. In the reaction from stopped Ξ ? on 6Li target light doubly-strange nuclei, ${^5_{\Lambda\Lambda}{\rm H}}$ and ${^6_{\Lambda\Lambda}{\rm He}}$ , are produced: we have calculated the formation ratio of ${^5_{\Lambda\Lambda}{\rm H}}$ to ${^6_{\Lambda\Lambda}{\rm He}}$ for Ξ ? absorptions from 2S, 2P and 3D orbitals of Ξ ?–6Li atom by assuming a d?α cluster model for 6Li. From this cluster model the d?α relative wave functions has a node due to Pauli exclusion among nucleons belonging to d and α clusters. Two kinds of d?α wave functions, namely 1s relative wave function with a phenomenological one-range Gaussian (ORG) potential and that of an orthogonality-condition model (OCM) are used. It is found that the probability of ${^5_{\Lambda\Lambda}{\rm H}}$ formation is larger than that of ${^6_{\Lambda\Lambda}{\rm He}}$ for all absorption orbitals: in the case of the major 3D absorption their ratio is 1.08 for ORG and 1.96 for OCM. The dominant low momentum component of the d?α relative wave function favors the ${^5_{\Lambda\Lambda}{\rm H}}$ formation with a low Q value compared to the ${^6_{\Lambda\Lambda}{\rm He}}$ formation with a high Q value. We have also calculated momentum distributions of emitted particles, d and n, displaying continuum spectra for single-Λ hypernuclei, ${^4_{\Lambda}{\rm H}}$ and ${^5_{\Lambda}{\rm He}}$ , and line spectra for the ${^5_{\Lambda\Lambda}{\rm H}}$ and ${^6_{\Lambda\Lambda}{\rm He}}$ nuclei. Thus, our present theoretical analysis would be a significant contribution to experiments in the strangeness ?2 sector of hypernuclear physics. 相似文献