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71.
Ewa Wagner-Wysiecka Elżbieta Luboch Jan F. Biernat 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):19-22
Several new types of ionizable chromoionophores have been synthesized. Their reactions with metal cations have been studied by spectroscopic methods. Preferential complexation of lithium ions was found for many of these reagents. 相似文献
72.
Kozerski L Kamieński B Kawecki R Urbanczyk-Lipkowska Z Bocian W Bednarek E Sitkowski J Zakrzewska K Nielsen KT Hansen PE 《Organic & biomolecular chemistry》2003,1(20):3578-3585
Parent genistein and its new amine complexes with morpholine and piperazine were studied comparatively in the solid and liquid states by X-ray crystallography and 13C and 15N NMR spectroscopy. Biochanine A and its complexes were used as reference. Secondary deuterium isotope effects on 13C chemical shifts in solution were studied in parent isoflavones and their morpholine and piperazine complexes to aid in evaluation of the electronic distribution in both systems. In addition, to quantify the extent of proton transfer as well as to establish strong hydrogen bonding of the 7-OH group in a morpholine complex, proton transfer from the 7-OH group to the piperazine nitrogen atom was also confirmed by 13C NMR in the solid state and by X-ray studies. The effect of 7-OH deprotonation yields a high frequency shift of 7-8 ppm on the C-7 carbon atom of the piperazine complex whereas it is as large as 12 ppm in the morpholine complex in the solid. The former trend is confirmed from solution state concentration studies which also show that the isoflavones have a strong tendency to form complexes with bases. Depending on the pKa difference between the isoflavones and the base this leads either to proton transfer and ion-pair formation or, in the case of a larger pKa difference, to a hydrogen bonded ion pair. The concentration studies show formation of a 1:1 genistein-piperazine complex in DMSO. Addition of water leads to formation of solvent separated ions. The C-5 OH group is involved in strong intramolecular hydrogen bonding leading to a pseudo aromatic ring extending the aromatic part of the drug pharmacophore. The analysis also suggests the way that both the C-7 and C-4' hydroxyl group of genistein may participate in stabilising the ternary inhibitor complexes of tyrosine-specific kinases or DNA topoisomerase II. 相似文献
73.
A. Skwierawska E. Luboch J.F. Biernat V. Ch. Kravtsov Yu. A. Simonov A. A. Dvorkin V. K. Bel'skii 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(1):71-86
16-Membered dibenzoazo- and dibenzoazoxycrown ethers have been synthesized. The Z and E isomers of the azocrown compound have been separated and the geometry of the –N=N– and –-N(O)=N–- groups determined. Potassium iodide complexes of the azo- and azoxycrown ethers were obtained and their structures were determined by the X-ray method. The crystal of the azocrown ether complex is triclinic, space group P¯1, a = 21.071(5), b = 12.112(4), c = 8.757(2) Å = 81.28(2), = 84.66(2), = 107.49(2)°. The azoxycrown ether complex is monoclinic, space group C2/c, a = 15.648(3), b = 19.597(4), c = 14.651(3) Å; = 111.30(3). 相似文献
74.
FT-IR spectroscopic, AM1 and PM3 computational studies of conformation of natural products: cytisine
Infrared spectra were recorded for cytisine (1) and its model compounds: N-methyl-2-pyridone (2) and piperidine (3) in solution. Eight solvents of different polarity, polarizability and acid-base properties: CCl(4), CS(2), CHCl(3), CDCl(3) (for comparison with the NMR spectra), CH(2)Cl(2), MeOH, Et(2)O and Et(3)N were chosen. Experimental FT-IR spectra were analysed with the help of those calculated for isolated derivatives at the AM1 and PM3 levels. Influence of environment on the conformational preferences in solvated cytisine was discussed and compared with those in the solid state (X-ray measurements) and in the gas phase (quantum-mechanical calculations). 相似文献
75.
Pamuła E De Cupere V Dufrêne YF Rouxhet PG 《Journal of colloid and interface science》2004,271(1):80-91
The adsorption of collagen on polystyrene (PS) and polystyrene oxidized by oxygen plasma discharge (PSox) was studied as a function of time using radiolabeling, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Radiolabeling and XPS indicated that the initial step of adsorption was faster on PS than on PSox. AFM imaging under water revealed very different supramolecular organization of the adsorbed films depending on time and on the nature of the substrate: PS showed patterns of collagen aggregates at all adsorption times (from 1 min to 24 h); PSox was covered with a smooth layer except at long adsorption times (24 h), for which a mesh of collagen structures was observed. After fast drying, the collagen layer remained continuous and showed a morphology which recalled that observed under water. The mechanical stability of the adsorbed films was assessed under water by scraping with the AFM probe at different loading forces: no perturbations were created on PSox; in contrast, the layer adsorbed on PS was sensitive to scraping, the minimum force required to alter the collagen layer morphology increasing with time. These differences in the film properties were correlated with force measurements upon retraction: multiple adhesion forces were observed with collagen adsorbed on PS samples, whereas such an effect was never observed on PSox. The results show that the amount adsorbed and the organization of the adsorbed film respond differently to the adsorption time and that this is influenced by surface hydrophobicity. The quick initial adsorption on PS, compared to PSox, is thought to leave dangling collagen segments that are responsible for the observed morphology, for adhesion forces, and for lower mechanical resistance of the adsorbed layer. 相似文献
76.
Magdalena Prokopowicz Elbieta Luboch Jan F. Biernat Jacek Namienik Andrzej Przyjazny 《Journal of separation science》1998,21(5):303-307
Quartz rods coated with a thin layer of chemically modified silica gel have been used for the generation of a two-component gaseous standard mixture containing carbon monoxide and carbon dioxide. A new method based on thermal decomposition of immobilized compounds chemically bonded to the surface of silica gel has been used in the generation process. The oxalic acid moiety bonded to the glycydoxypropylsilylated surface of silica gel underwent decarbonylation and decarboxylation at 300°C, yielding carbon monoxide and carbon dioxide. On-line connection of a thermal desorber with the GC/FID enabled calibration of the detector following the process of methanization of CO and CO2. The following amounts of CO and CO2 were generated per unit length of the rod: 15.1 × 10−8 Mol cm−1 (RSD = 5.71%) for CO and 34.2 × 10−8 Mol cm−1(RSD = 5.16%) for CO2. 相似文献
77.
Danuta Kruk Elzbieta Masiewicz Evrim Umut Martin Schlögl Roland Fischer Hermann Scharfetter 《Molecular physics》2019,117(7-8):944-951
ABSTRACT1H spin-lattice relaxation studies have been performed for pure [Bi(NO3)3(H2O)3]*18-crown-6 in powder and its solution in dimethyl sulfoxide (DMSO). The experiments have been carried out in the frequency range of 10?kHz–30?MHz and the temperature range of 240–277?K; at 277?K the solution is already frozen. The 1H relaxation of pure [Bi(NO3)3(H2O)3]*18-crown-6 has been interpreted in terms of three dynamical processes. Quadrupole Relaxation Enhancement effects have been observed in the frozen DMSO solution of [Bi(NO3)3(H2O)3]*18-crown-6. The specific mechanisms of the 1H spin-lattice relaxation enhancement have been discussed distinguishing between effects caused by time independent (residual) and fluctuating 1H-209Bi dipole-dipole interactions. 相似文献
78.
79.
Lithium (Li) and its salts have been demonstrated to be the most effective drug in both acute and prophylactic treatment of bipolar disorder. The exact molecular mechanisms and particular target regions accounting for its mood-stabilizing effect remain unknown. Knowledge of Li distribution and its regional pharmacokinetic properties in the living brain is of value in localizing its action in the brain. Pharmacokinetic measurements in different anatomical regions of the human brain are not yet available. Limited pharmacokinetic measurements in rat brain subvolumes have been performed using atomic absorption technique. However, a noninvasive way of estimating the pharmacokinetics in different regions of the brain where the drug exerts its beneficial effects would allow such methods to be used in the study of patients undergoing Li therapy. Earlier (7)Li MR studies on rat brain regions have provided preliminary pharmacokinetic information from the whole brain. Using (7)Li MR spectroscopic imaging (SI) technology, Li distribution in brain regions of the rat at therapeutic dosages has been recently demonstrated by us. Here we report feasibility of local pharmacokinetic measurements on brain regions obtained by magnetic resonance SI technology. Our results suggest that Li is most active in a region stretching from the anterior cingulate cortex and striatum to the caudal midbrain, with greatest activity including the preoptic area and hypothalamic region. Some activity was seen in prefrontal cortex, but only minimal amounts in the region of the cerebellum and metencephalic brainstem. 相似文献
80.
Gary Chartrand Elzbieta B. Jarrett Farrokh Saba Ebrahim Salehi Ping Zhang 《Czechoslovak Mathematical Journal》2001,51(2):351-361
For a nontrivial connected graph F, the F-degree of a vertex in a graph G is the number of copies of F in G containing . A graph G is F-continuous (or F-degree continuous) if the F-degrees of every two adjacent vertices of G differ by at most 1. All P3-continuous graphs are determined. It is observed that if G is a nontrivial connected graph that is F-continuous for all nontrivial connected graphs F, then either G is regular or G is a path. In the case of a 2-connected graph F, however, there always exists a regular graph that is not F-continuous. It is also shown that for every graph H and every 2-connected graph F, there exists an F-continuous graph G containing H as an induced subgraph. 相似文献