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71.
Mustafa Catir Murat Cakici Semistan Karabuga Sabri Ulukanli Ertan Şahin Hamdullah Kilic 《Tetrahedron: Asymmetry》2009,20(24):2845-2853
Optically active propargylic alcohols are important chiral-building blocks in asymmetric synthesis, while the asymmetric addition of a terminal alkyne to an aldehyde is one of the most important procedures to prepare these chiral-building blocks. In this work, a family of chiral 4,4′-biquinazoline alcohols has been conveniently prepared from the easily accessible (S)-2-acetoxycarboxylic acid chlorides by reaction sequences beginning with condensation and followed by key synthetic steps including chlorination, nickel(0)-mediated homocoupling, and deprotection in addition to being examined as potential ligands in the enantioselective addition of phenylacetylene to aldehydes. These chiral ligands can be combined with Ti(OiPr)4 and then used to catalyze the asymmetric addition of zinc acetylide, produced in situ by the reaction of phenylacetylene with diethylzinc, to aldehydes. The best enantiomeric excess obtained in this study was 75%. 相似文献
72.
Sabri Cevik Bihter Şaşmaz Mehmet Poyraz Musa Sarı Orhan Büyükgüngör 《Journal of chemical crystallography》2011,41(6):796-800
Abstract
Hydrothermal synthesis and the structural characterization of V(IV) complex of 2-pyrazinecarboxylate (pzc), is reported. The vanadium is in a distorted octahedral environment. Pairs of pyrazine-2-carboxylate ligands are always cis to each other. The pzc ligands do not link adjacent vanadium atom directly. The remainder of the three-dimensional network is completed by intense hydrogen bonding of uncoordinated water molecules to aqua and pzc ligands. Cis-[VIVO(pzc)2(H2O)]·2H2O, 1, was characterized by means of elemental analysis (CHNS), TGA, FT-IR, manganometric titration, bond valance sum calculations and single crystal X-ray diffraction methods. Crystal data for 1: monoclinic space group P2 1 /c and unit-cell parameters are a = 9.1142(5), b = 16.5822(10), c = 12.8936(7) ?, β = 131.625(3)° and Z = 4. To the best of our knowledge, cis-[VIVO(pzc)2(H2O)] is reported without single crystal structure by Eugenio Garribba and his colleagues in year 2006. Herein we complete full characterization of the title complex with single crystal structure and also 1 will be the first reported example of solid vanadium complex of 2-pyrazinecarboxylates involving intense hydrogen bonding. 相似文献73.
A charge trapping memory with 2 nm silicon nanoparticles (Si NPs) is demonstrated. A zinc oxide (ZnO) active layer is deposited by atomic layer deposition (ALD), preceded by Al2O3 which acts as the gate, blocking and tunneling oxide. Spin coating technique is used to deposit Si NPs across the sample between Al2O3 steps. The Si nanoparticle memory exhibits a threshold voltage (Vt) shift of 2.9 V at a negative programming voltage of –10 V indicating that holes are emitted from channel to charge trapping layer. The negligible measured Vt shift without the nanoparticles and the good re‐ tention of charges (>10 years) with Si NPs confirm that the Si NPs act as deep energy states within the bandgap of the Al2O3 layer. In order to determine the mechanism for hole emission, we study the effect of the electric field across the tunnel oxide on the magnitude and trend of the Vt shift. The Vt shift is only achieved at electric fields above 1 MV/cm. This high field indicates that tunneling is the main mechanism. More specifically, phonon‐assisted tunneling (PAT) dominates at electric fields between 1.2 MV/cm < E < 2.1 MV/cm, while Fowler–Nordheim tunneling leads at higher fields (E > 2.1 MV/cm). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
74.
M. Patt A. Schildan H. Barthel G. Becker M. H. Schultze-Mosgau B. Rohde C. Reininger O. Sabri 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):557-562
[18F]Florbetaben ([18F]BAY 94-9172) is a promising β-amyloid (Aβ) targeted PET-tracer currently in late stage clinical development. [18F]Florbetaben can assist in the more accurate diagnosis of Alzheimer’s Disease (AD) by non-invasive, in vivo detection of
Aβ in the brain. To determine the arterial input function of the PET tracer—as part of a proof of mechanism (PoM) study—arterial
samples were drawn from all subjects at predefined time points post injection (p.i.), and the proportion of unchanged tracer
[18F]Florbetaben was determined by HPLC analysis. Plasma metabolite profiles were investigated following intravenous administration
of 300 MBq (±60 MBq) of [18F]Florbetaben to both, patients with AD and healthy controls (HCs), and various methods for processing the blood samples were
evaluated. Addition of acetonitrile to plasma samples (obtained from whole blood by centrifugation) and precipitation of proteins
resulted in a recovery of more than 90% of the initial radioactivity in the supernatants. High Performance Liquid Chromatography
using a polymer-based column (PRP-1) in conjunction with gradient elution was found to be a suitable method of metabolite
analysis of [18F]Florbetaben. HPLC analyses indicated that [18F]Florbetaben is rapidly metabolized in vivo with an estimated initial half-life of about 6 min. A polar metabolite fraction,
consisting presumably of more than one component, and (to a smaller extent) of the demethylated derivative of [18F]Florbetaben were time-dependently detected in plasma. 相似文献
75.
Sabri Touidjine Moulai Karim Boulkadid Djalal Trache Samir Belkhiri Hamdane Akbi Anes Abdessamed 《国际化学动力学杂志》2023,55(2):72-86
Polyester (HTPS) based polyurethane (PU) elastomers were currently established to be effective binders for high-energy composites with improved performances. Conventional PU binders are mostly non-energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, it may be introduced in PU-based compositions to overcome their performance drawback. Kinetic parameters must be specified in order to build PU binders with the most convenient and appropriate features. Therefore, the cure kinetics of polyester based polyurethane binder systems were investigated by Fourier transform infrared spectroscopy (FT-IR) isothermal method. The polyester prepolymer (Desmophen® 1200) was cured with hexamethylene diisocyanate (HDI: Desmodur® N100) at various molar ratios (R[NCO]/[OH] = 0.6, 1, 1.25, and 1.5) and under different isothermal conditions (T = 60°C, 80°C, 100°C, and 120°C). In addition, the effect of the addition of nitrocellulose on the kinetics of polymerization of PU was investigated. The progression of the reaction was followed based on the decrease of the peak intensity of –NCO group at 2271 cm−1 as a function of the reaction time. The curing kinetic model and the apparent activation energy (Eα) were determined by the use of Kamal autocatalytic model and Friedman isoconversional method, respectively. 相似文献
76.
Ricerche di Matematica - In this paper, we prove the existence and uniqueness results of entropy solutions to a class of nonlinear parabolic p(u)-Laplacian problem with Fourier-type boundary... 相似文献
77.
Masood Parvez M. Saeed Arayne Rizwana Sabri Najma Sultana 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):e398-e399
The absolute configuration was determined for the title compound, C38H70NO13+·Cl?·3.5H2O. The cation contains a 14‐membered macrocyclic lactone and two sugars, namely cladinose and desosamine. The six‐membered rings of the sugars adopt chair conformations. The structure is stabilized by strong hydrogen bonds, with O?O distances in the range 2.486 (9)–2.830 (5) Å; other distances are N?O = 2.860 (5), N?Cl = 3.134 (4) and O?Cl = 3.303 (4) Å. 相似文献
78.
Karabuga S Cakici M Kazaz C Sahin E Kilic H Ulukanli S 《Organic & biomolecular chemistry》2011,9(22):7887-7896
A series of sulfoxides were sulfoximinated using oxidative addition of 3-aminoquinazolinones by lead tetraacetate in the presence of hexamethyldisilazane. They were applied for the first time in catalytic enantioselective addition to aromatic aldehydes with a product enantiopurity (ee) of 92% in the case of 2-methoxybenzaldehyde. 相似文献
79.
Rizwana Zahoor Samina Roohi Mushtaq Ahmad Zafar Iqbal Nagina Amir Saima Tariq Paul. B. Savage 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):841-844
Ceragenins/cationic steroid antimicrobials (CSAs) are a group of cholic acid derivatives with many properties that make them favourable for application as anti-infective agents. CSA-107 is also a member of this group that was labelled with 99mTc by using SnCl2·2H2O as reducing agent and Na–K tartrate as transchelating agent. Labelling efficiency was optimized by varying the amount of reducing agent, pH, and time of incubation. Labelling efficiency and the stability of 99mTc-CSA-107 in human serum was determined by paper and thin layer chromatography, which were >95 and >90 % respectively. In vitro binding of 99mTc-CSA-107 was >95 % determined by using Staphylococcus aureus bacteria. 相似文献
80.