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91.
Hansen RR Tipnis AA White-Adams TC Di Paola JA Neeves KB 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13648-13658
Von Willebrand factor (VWF) binding and platelet adhesion to subendothelial collagens are initial events in thrombus formation at sites of vascular injury. These events are often studied in vitro using flow assays designed to mimic vascular hemodynamics. Flow assays commonly employ collagen-functionalized substrates, but a lack of standardized methods of surface ligation limits their widespread use as a clinical diagnostic. Here, we report the use of collagen thin films (CTF) in flow assays. Thin films were grown on hydrophobic substrates from type I collagen solutions of increasing concentration (10, 100, and 1000 μg/mL). We found that the corresponding increase in fiber surface area determined the amount of VWF binding and platelet adhesion. The association rate constant (k(a)) of plasma VWF binding at a wall shear stress of 45 dyn/cm(2) was 0.3 × 10(5), 1.8 × 10(5), and 1.6 × 10(5) M(-1) s(-1) for CTF grown from 10, 100, and 1000 μg/mL solutions, respectively. We observed a 5-fold increase in VWF binding capacity with each 10-fold increase in collagen solution concentration. The association rates of Ser1731Thr and His1786Asp VWF mutants with collagen binding deficiencies were 9% and 22%, respectively, of wild-type rates. Using microfluidic devices for blood flow assays, we observed that CTF supported platelet adhesion at a wall shear rate of 1000 s(-1). CTF grown from 10 and 100 μg/mL solutions had variable levels of platelet surface coverage between multiple normal donors. However, CTF substrates grown from 1000 μg/mL solutions had reproducible surface coverage levels (74 ± 17%) between normal donors, and there was significantly diminished surface coverage from two type 1 von Willebrand disease patients (8.0% and 24%). These results demonstrate that collagen thin films are homogeneous and reproducible substrates that can measure dysfunctions in VWF binding and platelet adhesion under flow in a clinical microfluidic assay format. 相似文献
92.
Miroslava ?pérová Petr Nasadil Alena Pr??ová Ji?í Ku?erík 《Journal of Thermal Analysis and Calorimetry》2012,110(1):71-76
The degree of polymerization is one of the main parameters reflecting cellulose ageing. Viscometry is a method frequently used for determination of cellulose fibers polymerization degree, however, sample preparation and viscosity measurement are demanding, time consuming and do not provide reproducible results. In this study, the relationship between polymerization degree of cellulose fibers obtained by viscosity measurement and their degradation parameters obtained by thermal analysis were investigated. Differential scanning calorimetry provided values of effective combustion heat and thermogravimetry (TG) was used for the determination of temperatures and associated mass losses during the cellulose degradation. Effective combustion heat did not show any correlation with degree of polymerization of investigated cotton fabrics. In contrast, results from TG suggested several promising nonlinear correlations which could be used as a hint to develop a method useful for quick determination of cotton fabrics polymerization degree. The most promising correlations with cellulose polymerization degree were found for both rates of thermal and thermo-oxidative degradations. 相似文献
93.
Borkin DA Puscau M Carlson A Solan A Wheeler KA Török B Dembinski R 《Organic & biomolecular chemistry》2012,10(23):4505-4508
5-Exo-dig cyclocondensation of alk-3-yn-1-ones with hydrazines, in the presence of montmorillonite K-10, provides an effective method with a high atom economy for the synthesis of diversely 1,3,5-trisubstituted pyrazoles. The microwave-accelerated reaction proceeds in the absence of solvent and leads to 5-benzyl substituted pyrazoles with good yields (72-91%). The regiochemistry of the process was confirmed by the X-ray crystallographic structure determination of 1-(2-fluorophenyl)-5-(4-methylbenzyl)-3-phenyl-1H-pyrazole. 相似文献
94.
Lucie Marková Zuzana Ciesarová Kristína Kukurová Henryk Zieliński Ma?gorzata Przygodzka Alena Bednáriková Peter ?imko 《Chemical Papers》2012,66(10):949-954
The aim of this work was to study the effect of various spices (cloves, cinnamon, allspice, white pepper, anise, star anise, coriander, fennel, nutmeg, cardamom, vanilla, and ginger) on acrylamide formation in buckwheat ginger cakes. The spices were characterised by their free radical scavenging activity and applied to formulation of the buckwheat ginger cakes in the same portions. After baking, the acrylamide content was determined by LC/ESI-MS-MS. The results showed a reduction in acrylamide content of up to 23 % in the buckwheat ginger cakes with the addition of nutmeg, fennel, anise, or cloves. A decrease in acrylamide content from 5 % to 11 % was found in the buckwheat ginger cakes with vanilla, cardamom, white pepper, or ginger. By contrast, the acrylamide content in the buckwheat ginger cakes with cinnamon or coriander increased by up to 29 %. No change in the acrylamide content was observed in the buckwheat ginger cakes with star anise or allspice. Only a slight correlation between the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH·) free radical scavenging activity of the added spices and the final acrylamide content in the buckwheat ginger cakes (0.68) was observed. The final acrylamide content was probably influenced not only by the free radical scavenging activity of the spices added, but also by their chemical composition and the reactiveness of particular constituents with synergistic/antagonistic effect in the matrix studied. 相似文献
95.
Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal. 相似文献
96.
Sergey A. Lermontov Alena N. Malkova Andrei V. Churakov 《Journal of organometallic chemistry》2009,694(16):2476-2479
A new method of 1-fluorosilatrane synthesis on the basis of silicon tetrafluoride complexes obtained from SiO2 is offered. Chemical properties of 1-fluorosilatrane in reactions of nucleophilic substitution are investigated. It is shown that fluorine can be substituted by O-nucleophiles (lithium methoxide, isopropoxide and phenoxide) and C-nucleophile (lithium phenylacetylenide). 相似文献
97.
Jiri A. Mares Petr Prusa Martin Nikl Karel Nitsch Alena Beitlerova Miroslav Kucera Martin Hanus Yurij Zorenko 《Radiation measurements》2010,45(3-6):369-371
Scintillating properties of Ce3+-doped (Lu,Y) aluminum garnet single crystalline films (SCF) were investigated. Thin SCF films of thickness between 1 and 30 μm were grown by a liquid phase epitaxy (LPE) method in various fluxes. The α-particle excitation (mainly 5.4857 MeV line of 241Am) of pulse height spectra is used to measure scintillation response of SCF, especially peak of those α-rays which are totally absorbed in the films. Detailed studies and evaluation of scintillation measurements of large sets of Ce3+-doped SCF (Lu,Y) aluminum garnets showed that at present time (i) YAG:Ce SCF have comparable scintillation properties as YAG:Ce single crystals, especially their Nphels photoelectron yields are the same while (ii) scintillation properties of LuAG:Ce SCF do not reach those of LuAG:Ce single crystal. 相似文献
98.
Polina R. Petrova Alena V. Koval’skaya Alexander N. Lobov 《Natural product research》2019,33(13):1897-1902
The first direct synthesis of 3-N-methyl-9-formylcytisine via electrophylic formylation is described. It is established, that Vilsmeier-Haack and Gatterman variants of this reaction are unsuccessful in the case with 3-substituted (-)-cytisine derivatives, but Duff procedure (with hexamethylenetetramine in trifluoroacetic acid) gives a possibility to obtain the target pseudo aromatic aldehyde with the 69% yield. Convenient precursors for [4 + 2]- or [3 + 2]-cycloaddition reactions are obtained by means of condensation of synthesized 3-N-methyl-9-formylcytisine with acetone, nitromethane and phosphorous ylides with yields from 70 to 87%. Alternative aprroach to alkenyl products and to 9-alkynyl-3-methylcytisine is realized using the Heck and Sonogashira cross-coupling reactions of methyl vinyl ketone, cyclohexenone or trimethylsilylacetylene with 9-bromo-3-methylcytisine (55, 70 and 60% accordingly). It is shown, that interaction of 3-N-methyl-9-formylcytisine with hydroxylamines leads to corresponding nitrone (93%) and oxime (70%). All individual compounds are isolated by column chromatography and completely characterized on the basis of NMR spectroscopy data. 相似文献
99.
100.
Dmitrii L. Obydennov Diana I. Nigamatova Alexander S. Shirinkin Oleg E. Melnikov Vladislav V. Fedin Sergey A. Usachev Alena E. Simbirtseva Mikhail Y. Kornev Vyacheslav Y. Sosnovskikh 《Molecules (Basel, Switzerland)》2022,27(24)
A straightforward approach for the construction of the new class of conjugated pyrans based on enamination of 2-methyl-4-pyrones with DMF-DMA was developed. 2-(2-(Dimethylamino)vinyl)-4-pyrones are highly reactive substrates that undergo 1,6-conjugate addition/elimination or 1,3-dipolar cycloaddition/elimination followed by substitution of the dimethylamino group without ring opening. This strategy includes selective transformations leading to conjugated and isoxazolyl-substituted 4-pyrone structures. The photophysical properties of the prepared 4-pyrones were determined in view of further design of novel merocyanine fluorophores. A solvatochromism was found for enamino-substituted 4-pyrones accompanied by a strong increase in fluorescence intensity in alcohols. The prepared conjugated structures demonstrated valuable photophysical properties, such as a large Stokes shift (up to 204 nm) and a good quantum yield (up to 28%). 相似文献