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41.
Pedersen DS Capone DL Skouroumounis GK Pollnitz AP Sefton MA 《Analytical and bioanalytical chemistry》2003,375(4):517-522
A mixture of [(2)H(7)]-geraniol, [(2)H(7)]-nerol, [(2)H(7)]-linalool and [(2)H(7)]-alpha-terpineol was prepared for use as internal standards in a rapid and accurate analytical method, employing gas chromatography-mass spectrometry (GC/MS), to determine the concentration of geraniol, nerol, linalool and alpha-terpineol in wine. The method avoids the possible formation, degradation and interconversion of these compounds during their analysis. 相似文献
42.
Reviakine I Georgiou DK Vekilov PG 《Journal of the American Chemical Society》2003,125(38):11684-11693
During layerwise growth of crystals, capillarity governs the generation of new crystal layers. Theory predicts that the line tension of the layer edge determines, via the characteristic two-dimensional capillary length L(c), the rates of generation and initial growth of the new layers. To test the correlation between L(c) and the rate of layer generation, we used in situ Tapping Mode Atomic Force Microscopy (TM-AFM) to study the generation and spreading of layers during crystallization of rhombohedral, R3, porcine insulin. We show that crystallization of this insulin form is uniquely suitable for such an investigation due to the linear kinetics of step growth it exhibits. This linear kinetics reflects the abundance of the incorporation sites along the rough steps, the lack of long-range step-step interactions, and the transport control of the growth kinetics. The kinetic coefficients are 7 x 10(-)(3) and 4 x 10(-)(2) cm s(-)(1), respectively, in the absence and presence of the cosolvent acetone-somewhat high for proteins and comparable to values for inorganic systems. We show that (i). the relevant capillary length, the size of a critical quadrangular 2D nucleus L(c), is the main scaling factor for the density of growth steps, while (ii). all steps longer than L(c) grow with a rate determined only by the supersaturation and independent of their length. We explain the divergence of (ii). from theoretical predictions with the high supersaturations typical of the growth of this protein system. 相似文献
43.
Demetrios N. Nicolaides Konstantina C. Fylaktakidou Konstantinos E. Litinas George K. Papageorgiou Dimitra J. Hadjipavlou-Litina 《Journal of heterocyclic chemistry》1998,35(3):619-625
1,3-Cycloaddition reactions of new 2-oxo-2H-[1]benzopyran-4-carbonitrile N-oxide 2 with dipolarophiles, o-aminophenols and o-phenylenediamine resulted in 4-heterocyclic substituted coumarin derivatives. These derivatives are screened for antiinflammatory activity in vitro through their antiproteolytic activity, the interaction with 1,1-diphenyl-2-picrylhydrazyl and the ability to affect superoxide anion and to inhibit β-glucuronidase and soybean lipoxygenase. 相似文献
44.
Application of solvent microextraction in a single drop for the determination of new antifouling agents in waters 总被引:1,自引:0,他引:1
A new, rapid microextraction technique termed solvent microextraction (SME) has been developed for the simultaneous determination of new generation antifouling agents, in water samples. Chlorothalonil, dichlofluanid and Sea nine 211 were employed as model compounds to asses the extraction procedure and were determined by gas chromatography with electron capture detection. Experimental parameters which control the performance of SME, such as selection of solvent, exposure time, agitation, organic drop volume, and salt concentration were optimized. The new method provided good average enrichment factors of >10.7 for all analytes, good precision (RSD < 8.5%) and good linearity (r2 > 0.9880). The limits of detection (LODs) were in the range of 0.00025-0.003 microg/L (S/N = 3). The SME was performed in different type of natural water samples and acceptable recoveries were obtained for the tested analytes. The results demonstrated that SME is a rapid, accurate and effective preparation method and could be successfully performed for the determination of antifouling agents in water samples. 相似文献
45.
Katerina Orfanou Dimitra Topouza George Sakellariou Stergios Pispas 《Journal of polymer science. Part A, Polymer chemistry》2003,41(16):2454-2461
The complexation between narrow molecular weight distribution poly(2‐vinylpyridine) (P2VP) and polystyrene (suPS) or polyisoprene (suPI) end‐functionalized with one sulfonic acid group was examined in tetrahydrofuran dilute solutions by a combination of static and dynamic laser light scattering. Both apparent weight‐average molecular weight (Mw,app) and hydrodynamic radius (Rh) of the complexes exhibited a maximum at a certain molar ratio of suPS chains to P2VP monomeric units. This indicated that the P2VP backbone may be saturated by the grafted end‐functionalized chains because of repulsion between the grafted chains. By changing the molar mass of P2VP from 100,000 to 30,000 g/mol, the values of Mw,app and Rh decreased. When suPI was used instead of suPS, similar trends were observed. In the latter case, it was possible to prepare block copolymer‐like micelles by transferring the P2VP/suPI blend solutions in decane, which is a selective solvent for PI. The non‐covalent‐bonded polymeric micelle characteristics were investigated as a function of sulfonic acid/2‐vinylpyridine units ratio as well as temperature. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2454–2461, 2003 相似文献
46.
47.
Costopoulos B Benaki D Pelecanou M Mikros E Stassinopoulou CI Varvarigou AD Archimandritis SC 《Inorganic chemistry》2004,43(18):5598-5602
The decapeptide Arg-Gly-Asp-Ser-Cys-Arg-Gly-Asp-Ser-Tyr, which contains two Arg-Gly-Asp (RGD) moieties in its sequence, has been successfully labeled with radioactive rhenium (Re-188) yielding a single, stable oxorhenium complex. This complex is being evaluated for possible application in oncology as a target-specific radiotherapeutic agent, because its radioactive technetium-99m analogue has already been applied for the scintigraphic detection of malignant melanoma in humans. For structural characterization purposes, the complex of the decapeptide was synthesized at the macroscopic level using nonradioactive rhenium (Re-185/Re-187). NMR and mass spectral analysis of the nonradioactive oxorhenium complex revealed that the decapeptide coordinates to the oxorhenium core through the N(amide) of Asp3, the N(amide) of Ser4, and the N(amide) and S(thiolate) atoms of Cys5 to form a complex of the ReO[N(3)S] type. 相似文献
48.
Nikolaos Stamatis Vassilios Triantafyllidis Dimitra Hela 《International journal of environmental analytical chemistry》2013,93(15):1602-1619
The occurrence of eight pharmaceutical compounds (PhCs), two metabolites and caffeine was investigated in River Acheloos, located in Western Greece, during a twelve-month monitoring period (March 2007–February 2008). Solid-phase extraction (SPE) was used for the extraction and pre-concentration of the target pollutants and gas chromatography mass spectrometry (GC–MS) for the detection and quantification. Recoveries were determined between 74.0–100.4% for distilled water and 72.6–95.1% for the river water, whereas the relative standard deviation was less than 9.4% for distilled water and 8% for the river water, respectively. The limits of detection ranged between 1–40 ng L?1. Two pharmaceuticals (paracetamol and carbamazepine), caffeine and the metabolite (salicylic acid), have been detected in all the analysed samples. Maximum concentration levels determined in river samples reached 305 ng L?1 recorded for paracetamol. The concentrations of target compounds were significantly higher in the samples collected at the sampling station situated after the wastewater treatment plant (WWTP) of Agrinio City compared to the samples collected in upper and lower parts of the river. Seasonal variations were attributed mainly to river flow variations and removal percentages by WWTP. Risk quotient method for median environmental concentrations revealed minimal to median risk with the exception of triclosan, ibuprofen and diclofenac, which presented high risk when maximum environmental concentrations were used. 相似文献
49.
Dimitra Kovala‐Demertzi Vaso Dokorou Zbigniew Ciunik Nikolaos Kourkoumelis Mavroudis A. Demertzis 《应用有机金属化学》2002,16(7):360-368
The triphenyltin adduct of mefenamic acid, [SnPh3L] ( 1 ), the monophenyltin complex [PhSnOL] n ( 2 ), and the dibutyltin complex [SnBu2L2] (3), where HL is 2‐[bis(2,3‐dimethylphenyl)amino]benzoic acid (mefenamic acid), have been prepared and structurally characterized by means of vibrational, 1H and 13C NMR spectroscopies. The crystal structure of 1 has been determined by X‐ray crystallography. X‐ray analysis revealed a pseudo‐pentacoordinated structure containing Ph3Sn coordinated to the carboxylato group. The structural distortion is a displacement from the tetrahedron toward the trigonal bipyramid. Significant C? H–π interactions and intramolecular hydrogen bonds stabilize the structure 1. The polar imino hydrogen atom participates in intramolecular hydrogen bonds. Complex 1 is self‐assembled via C? H–π and stacking interactions. Vibrational and NMR data are discussed in terms of the crystal structure and the proposed structures for 1–3. Compounds 1 and 3 were tested for antimycobacterial activity against Mycobacterium tuberculosis H37Rv. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
50.
Demetrios N. Nicolaides Konstantina C. Fylaktakidou Konstantinos E. Litinas Dimitra Hadjipavlou-Litina 《Journal of heterocyclic chemistry》1996,33(3):967-971
Reaction of compound 3 with nitrile oxide 4a affords compounds 5a and 6 in 73% and 3% yield respectively, while reaction of 3 with 4b affords only compound 5b (85%). Reactions of compound 8 with the nitrile oxides 4a,b result in compounds 9a,b . The compound 10 , prepared from 1 and O-methylhydroxylamine, reacts with nitrile oxide 4b to give the oxadiazole derivative 12 . The above referred coumarins are screened for antiinflammatory activity in vivo using the carrageenin rat paw edema and in vitro through their antiproteolytic activity and their ability to inhibit β-glucuronidase and 12-Lipoxygenase. 相似文献