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291.
Abstract

The rhizomes of Bergenia ciliata (B. ciliata, Family: Saxifragaceae) are widely used for treating gastric ulcers in folk medicine in Asia. It was hypothesized that anti-ulcer activity of B. ciliata is due to its anti-Helicobacter pylori (H. pylori) activity. The anti-H. pylori activity was investigated on six clinical bacterial isolates using agar well-diffusion and broth micro-dilution methods. The anti-H. pylori activity of amoxicillin (standard) was the highest (Zone of inhibition; ZI?=?25?mm, minimum inhibitory concentration; MIC=0.125?µg/µL) whereas among all the extracts of the rhizomes, methanol extract showed the highest activity (ZI?=?16?mm, MIC?=?12.50?µg/µL). Bioassay guided isolation of methanol extract using chromatographic and crystallization techniques isolated bergenin (ZI?=?21mm, MIC?=?0.391µg/µL) as constituent responsible for anti-H. pylori activity. The present study describes for the first time anti-H. pylori activity and possible mechanism of anti-ulcer properties of rhizomes of B. ciliata.  相似文献   
292.
The cationic polymerization of N-tert-butyl aziridine (TBA) can be conducted in such a way that the rate of termination is much slower than the rate of propagation, thus permitting preparation of a corresponding polymer which is “temporarily living”. Reactions of N-methyl-N-tert-butyl aziridinium triflate (which is the model for the active species of the living polymer) with different nucleophiles show that, at room temperature, the aziridinium ring reacts almost instantaneously with nucleophiles to form the corresponding ring-opened product. Analogous reactions with the aziridinium end group of living poly-TBA lead to polymers with varying end groups such as hydroxy, ester, primary, secondary or tertiary amino, halogen, and others. End group analysis by means of 360-MHz 1H-NMR nuclear magnetic resonance spectroscopy showed that the concentration of the end groups was in all cases equal to the concentration of the methyl head group, originating form the initiation reaction, if the terminating nucleophile was added five minutes after initiation (at 15°C). Under these conditions the polymerization is quantitative for initiator concentrations down to 0.01 mol L?1.  相似文献   
293.
In this paper, the importance of using directly measured loss figures is emphasized, as an alternative to the traditional loss estimation approach. The traditional approach that requires only a few direct measurements but demands more attention towards loss coefficients, empirical factors and design margins, renders a modern machine uncompetitive due to its complex flux picture. Measured loss data for two electrical steel grades is collected and provided for a wide range of frequencies and polarization levels (6–10 kHz, 0.1–1.8 T). The effect of, sample orientation (the cutting direction), sample dimensions (the cutting length) and sample production (the cutting process) on the loss figures is also measured and documented for the studied frequency–polarization domain. The aim of this measurement-based approach is to help reduce some of the uncertainties associated with the traditional approach and thus the design margins.  相似文献   
294.
A new chalcone compound, (E)-1-([1,1′-Biphenyl]-4-yl)-3-(4-bromothiophen-2-yl)prop-2-en-1-one (BBTP), crystallizes in the monoclinic space group P21/c and its structure has been characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and ultraviolet and visible (UV-Vis) absorption spectroscopy. The structural and spectroscopic analyses of the chalcone were calculated using DFT/B3LYP method. Molecular structure, crystal structure arrangement, and intermolecular hydrogen bond interactions were determined by single crystal X-ray diffraction method. In the crystal packing, intermolecular C?H···O hydrogen bonds and C?H···π interaction formed infinite two-dimensional sheets, thus strengthening the crystal structure. Hirshfeld surface analysis, HOMO-LUMO, and molecular electrostatic potential results are also reported.  相似文献   
295.
Jasminum sambac (L.) is a South Asian folkloric medicinal plant that has traditionally been used to treat cardiovascular problems. The current investigation was meticulously organized to explore the pharmacological foundation for the medicinal uses of J. sambac pertaining to cardiovascular ailments and to investigate the core mechanisms. Mechanistic investigation revealed that crude leaf extract of J. sambac produced ex-vivo vasorelaxant effects in endotheliumintact aorta ring preparation and hypotensive effect was recorded via pressure and force transducers coupled to the Power Lab Data Acquisition System. Moreover; J. sambac showed cardioprotective effects against adrenaline -induced left ventricular hypertrophy in rabbits observed hemodynamic. CK-MB, LDH, troponin, CRP, ALT, AST, ALP levels were shown to be lower in the myocardial infarction model, as were necrosis, oedema, and inflammatory cell recruitment in comparison to control. J. sambac has shown good antioxidant potential as well as prolonged the noradrenaline induced platelet adhesion. The vasorelaxant and cardioprotective effects in both in vivo and ex vivo experiments, which are enabled by activation of muscarinic receptor and/or releasing the nitric oxide and by reducing the adrenaline, induced oxidative stress, justifying its usage in cardiovascular disorders.  相似文献   
296.
Fabrication of complex molecular films of organic materials is one of the most important issues in modern nanoscience and nanotechnology. Soft materials with flexible properties have been given much attention and can be obtained through bottom up processing from functional molecules, where self-assembly based on supramolecular chemistry and designed assembly have become crucial processes and technologies. In this work, we report the successful incorporation of cationic laser dye rhodamine 6G abbreviated as R6G into the pre-assembled polyelectrolyte/surfactant complex film onto quartz substrate by electrostatic adsorption technique. Poly(allylamine hydrochloride) (PAH) was used as polycation and sodium dodecyl sulphate (SDS) was used as anionic surfactant. UV-Vis absorption spec-troscopic characterization reveals the formation of only H-type aggregates of R6G in their aqueous solution and both H- and J-type aggregates in PAH/SDS/R6G complex layer-by-layber films as well as the adsorption kinetics of R6G onto the complex films. The ratio of the absorbance intensity of two aggregated bands in PAH/SDS/R6G complex films is merely independent of the concentration range of the SDS solution used to fabricate PAH/SDS com-plex self-assembled films. Atomic force microscopy reveals the formation of R6G aggregates in PAH/SDS/R6G complex films.  相似文献   
297.
Journal of Thermal Analysis and Calorimetry - Fluorescein dye was prepared and characterized on the basis of microanalytical methods, FTIR, NMR and UV–visible spectroscopy in order to ensure...  相似文献   
298.
We present a procedure for the determination of the isotopic ratios of silicon and oxygen from the same aliquot of anhydrous silicate material. The sample is placed in a bromine pentafluoride atmosphere as it is heated with a CO2 laser system releasing silicon tetrafluoride and oxygen gasses. The oxygen gas is then purified to remove other reaction by‐products through several liquid nitrogen traps before being captured onto a molecular sieve and transferred to an isotope ratio mass spectrometer. The silicon tetrafluoride gas is then purified using a supplementary line by repeatedly freezing to ?196°C with liquid nitrogen and then thawing with an ethanol slurry at ?110°C through a series of metal and Pyrex traps. The purified gas is then condensed into a Pyrex sample tube before it is transferred to an isotope ratio mass spectrometer for silicon isotope ratio measurements. This system has silicon yields of greater than 90% for pure quartz, olivine, and garnet standards and has a reproducibility of ±0.1‰ (2σ) for pure quartz for both oxygen and silicon isotope measurements. Meteoritic samples were also successfully analyzed to demonstrate this system's ability to measure the isotopic ratio composition of bulk powders with precision. This unique technique allows for the fluorination of planetary material without the need for wet chemistry. Though designed to analyze small aliquots of meteoritic material (1.5 to 3 mg), this approach can also be used to investigate refractory terrestrial samples where traditional fluorination is not suitable.  相似文献   
299.
Applied Biochemistry and Biotechnology - (E)-2-(3-Hydroxy-4-methoxybenzylidene)hydrazinecarbothioamide 3 was synthesized by reacting thiosemicarbazide with 2-hydorxy-3-methoxybenzaldehyde in dry...  相似文献   
300.
Accreditation and Quality Assurance - To analyze drinking water dataset, various statistical methods have been applied, including discriminant analysis, logistic regression and cluster analysis, to...  相似文献   
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