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111.
Christoph von Bültzingslwen Aisling K. McEvoy Colette McDonagh Brian D. MacCraith 《Analytica chimica acta》2003,480(2):275-283
An optical sensor for the measurement of high levels of carbon dioxide in gas phase has been developed. It is based on fluorescence resonance energy transfer (FRET) between a long-lifetime ruthenium polypyridyl complex and the pH-active disazo dye Sudan III. The donor luminophore and the acceptor dye are both immobilised in a hydrophobic silica sol–gel/ethyl cellulose hybrid matrix material. Tetraoctylammonium hydroxide (TOA-OH) is used as an internal buffering system. Fluorescence lifetime is measured in the frequency domain, using low-cost phase modulation measurement technology. The use of Sudan III as an acceptor dye has enabled the sensor to have a dynamic range up to 100% carbon dioxide. The sensor displays 11.2° phase shift between the limit of detection (LOD) of 0.06 and 100% CO2 with a resolution of better than 2%. The encapsulation in the silica/polymer hybrid material has provided the sensor with good mechanical and chemical stability. The effect of molecular oxygen, humidity and temperature on the sensor performance was studied in detail. 相似文献
112.
von Bultzingslöwen C McEvoy AK McDonagh C MacCraith BD Klimant I Krause C Wolfbeis OS 《The Analyst》2002,127(11):1478-1483
An optical sensor for the measurement of carbon dioxide in Modified Atmosphere Packaging (MAP) applications has been developed. It is based on the fluorescent pH indicator 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) immobilised in a hydrophobic organically modified silica (ormosil) matrix. Cetyltrimethylammonium hydroxide was used as an internal buffer system. Fluorescence is measured in the phase domain by means of the Dual Luminophore Referencing (DLR) sensing scheme which provides many of the advantages of lifetime-based fluorometric sensors and makes it compatible with established optical oxygen sensor technology. The long-term stability of the sensor membranes has been investigated. The sensor displays 13.5 degrees phase shift between 0 and 100% CO2 with a resolution of better than 1% and a limit of detection of 0.08%. Oxygen cross-sensitivity is minimised (0.6% quenching in air) by immobilising the reference luminophore in polymer nano-beads. Cross-sensitivity towards chloride and pH was found to be negligible. Temperature effects were studied, and a linear Arrhenius correlation between ln k and 1/T was found. The sensor is stable over a period of at least seven months and its output is in excellent agreement with a standard reference method for carbon dioxide analysis. 相似文献
113.
Boskovic C Güdel HU Labat G Neels A Wernsdorfer W Moubaraki B Murray KS 《Inorganic chemistry》2005,44(9):3181-3189
The syntheses, structures, and magnetochemical characterization of two novel mixed-chelate undeca- and dodecanuclear ferric complexes are reported. Preformed tri- and pentanuclear ferric complexes that possess tridentate Schiff base (L2- and (L'2-) and acetate ligands were reacted with 1,1,1-tris(hydroxymethyl)ethane (H3thme) to afford [Fe11O3(OH)(O2CMe)8(thme)2(L)6] (1) and [Fe12O4(O2CMe)8(thme)2(NH2(CH2)2O)2(L')6] (2), respectively, following structural agglomeration and rearrangement associated with ligand substitution. The incorporation of more than one type of ligand that can both chelate and bridge the Fe centers gives rise to the complicated molecular structures displayed by 1 and 2. As a result of the tripodal conformation of thme3-, the cores of both molecules incorporate several face-shared defect {Fe3O4}+ cuboidal subunits. Variable-temperature dc and ac magnetic susceptibility studies, together with low-temperature magnetization measurements, are consistent with S = 5/2 and S = 0 ground-state spins for 1 and 2, respectively, and suggest that excited states with higher spin values lie relatively close in energy to the ground state for both species. Low-temperature micro-SQUID measurements on oriented single crystals of 1 confirm the easy-axis type magnetic anisotropy suggested by conventional SQUID magnetometry. However magnetization hysteresis is not observed down to 0.04 K, which is ascribed to rapid quantum tunneling of the magnetization associated with transverse interactions. 相似文献
114.
E. Colette Crepeau 《European Polymer Journal》1983,19(12):1099-1105
In order to prepare chelating polymers and metalliferous dyes, chemical modification of poly(butylacrylate-co-glycidylmethacrylate) is carried out. The present article refers to the study of this modification using models. Two compounds are chosen, viz. glycidyl isobutyrate which is a model for one monomer unit and diglycidyl-2,4 dimethylglutarate which is a model for two consecutive monomer units. The syntheses of these models are described; the kinetics of their reaction with 4-hydroxybenzoic acid are studied. Orders in catalyst (dimethyldodecylamine) and in reactants are respectively 1 and 1.5 for both models. Rate constants are determined in various solvents. The results fit Madec's pattern. 相似文献
115.
Beaulieu PL Gillard J Bailey MD Boucher C Duceppe JS Simoneau B Wang XJ Zhang L Grozinger K Houpis I Farina V Heimroth H Krueger T Schnaubelt J 《The Journal of organic chemistry》2005,70(15):5869-5879
(1R,2S)-1-Amino-2-vinylcyclopropanecarboxylic acid (vinyl-ACCA) is a key building block in the synthesis of potent inhibitors of the hepatitis C virus NS3 protease such as BILN 2061, which was recently shown to dramatically reduce viral load after administration to patients infected with HCV genotype 1. We have developed a scalable process that delivers derivatives of this unusual amino acid in >99% ee. The strategy was based on the dialkylation of a glycine Schiff base using trans-1,4-dibromo-2-butene as an electrophile to produce racemic vinyl-ACCA, which was subsequently resolved using a readily available, inexpensive esterase enzyme (Alcalase 2.4L). Factors that affect diastereoselection in the initial dialkylation steps were examined and the conditions optimized to deliver the desired diastereomer selectively. Product inhibition, which was encountered during the enzymatic resolution step, initially resulted in prolonged cycle times. Enrichment of racemic vinyl-ACCA through a chemical resolution via diastereomeric salt formation or the use of forcing conditions in the enzymatic reaction both led to improvements in throughput and the development of a viable process. The chemistry described herein was scaled up to produce multikilogram quantities of this building block. 相似文献
116.
Three methods of obtaining asymmetric diaryloxy complexes of titanium (h5-Cp)(h5-Cp′)Ti(OAr)(OAr′) are proposed.Each of these methods leads to secondary products, selective substitution of the ligand (OAr) or (OAr′) by chlorine atom occurs by the action of hydrochloric acid in C6H6 solution. 相似文献
117.
Brahmananda Ghosh David A. Lightner Antony F. McDonagh 《Monatshefte für Chemie / Chemical Monthly》2004,75(1):1189-1199
A symmetrical C(10)-selena-bilirubin analog, 8,12-bis(2-carboxyethyl)-7,13-dimethyl-2,3,17,18-tetraethyl-10-selenabiladiene-ac-1,19(21H,24H)-dione was synthesized from 8-(2-carboxyethyl)-2,3-diethyl-7-methyl-(10H)-dipyrrin-1-one in one step by reaction with diselenyl dichloride. The selena-rubin exhibited UV-vis and NMR spectroscopic properties similar to those of the parent mesobilirubin, and like bilirubin and mesobilirubin, it adopts an intramolecularly hydrogen-bonded conformation, shaped like a ridge-tile but with a steeper pitch. The longer C–Se bond lengths (2.2Å) and smaller bond angles at C–Se–C (88°), as compared to C–CH2–C (1.5Å, 106°), lead to an interplanar angle between the two dipyrrinones of only 72°, which is considerably less than that of bilirubin (100°) and close to that (74°) of its 10-thia-rubin analog. Despite the conformational distortion, the sensitivity of Se toward oxidation and the typically weak C–Se bond, the selena-rubin is metabolized in normal rats, like bilirubin, to acyl glucuronides, which are secreted into bile. In mutant (Gunn) rats lacking bilirubin glucuronosyl transferase (UGT1A1), glucuronide or other metabolites of the selena-rubin were not detected in bile, demonstrating the importance of hepatic glucuronidation for its biliary excretion. 相似文献
118.
Colette C Denier Andrée A Brisson-Lougarre Ghislaine G Biasini Jean J Grozdea Didier D Fournier 《BMC biochemistry》2002,3(1):2-8
Background
In humans, there are four alkaline phosphatases, and each form exibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnent with a trisomy 21 fetus (Down's syndrome) displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors. 相似文献119.
Stefan E. Boiadjiev Brian A. Conley Justin O. Brower Antony F. McDonagh David A. Lightner 《Monatshefte für Chemie / Chemical Monthly》2006,137(11):1463-1476
Summary. A set of four regioisomeric dipyrrinone propionic acids has been synthesized and their hepatic metabolism examined in rats:
xanthobilirubinic acid and pseudo-xanthobilirubinic acid each with a propionic acid on a pyrrole ring; exo-ψ-xanthobilirubinic acid and endo-ψ-xanthobilirubinic acid, each with a propionic acid transposed to a lactam ring. After intravenous injection all four isomers
were excreted to some degree in unchanged form in bile in normal rats. Xanthobilirubinic acid, the structurally closest dipyrrinone
to bilirubin, and exo-ψ-xanthobilirubinic acid were excreted almost entirely in unchanged form. However, a small fraction of xanthobilirubinic
acid acyl glucuronide was also detected. More extensive acyl glucuronidation was observed for pseudo-xanthobilirubinic acid,
and endo-ψ-xanthobilirubinic acid underwent slow metabolism to unidentified more polar products that did not seem to be glucuronides. 相似文献
120.
A.K. McEvoy C. McDonagh B.D. MacCraith 《Journal of Sol-Gel Science and Technology》1997,8(1-3):1121-1125
Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped
with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched
in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order
to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function
of dip-speed and water: precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen
quenching in particular concentration ranges and environments. 相似文献