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81.
Isonicotinic acid hydrazide or isonicotinylhydrazide, commonly known as isoniazid, is an antibacterial agent that has been
used to treat tuberculosis. It interacts with microbial cell walls. Schiff’s bases or anils are the compounds having >C=N−N<
linkages, which have immense applications as catalysts, stabilizers, pigments, dyes, and drugs. They have good ability to
form chelates with many metal ions. Isoniazid can form Schiff’s bases with diketones such as acetoacetanilide. Acetoacetanilide
isonicotinylhydrazone and its metal chelates exhibit anticancer activity. Our studies on N-methyl-acetoacetanilide isonicotinylhydrazone and its metal chelates revealed that they are active against pathogenic fungal
strains. Hence, it is worthwhile to synthesize new complexes of ligands having different substituents on the acetoacetanilide
moiety. We synthesized five new metal chelates of ω-bromoacetoacetanilide isonicotinylhydrazone. The ligand behaved as a tridentate
monoanion or as a tridentate dianion in the complexes. These compounds were characterized mainly by elemental analysis; conductivity
measurements; and electronic, infrared, and nuclear magnetic resonance spectral studies. We also carried out antifungal studies
of these compounds against four selected pathogenic fungal strains using a cup-plate technique. Both the ligand and its metal
chelates were active against all fungal strains investigated. However, the chelates were found to be more active than the
ligand. 相似文献
82.
B3LYP/6-31G* calculations indicate that annelation of three-, four-, or five-membered rings to the rim of corannulene results in lowering the bowl-to-bowl inversion barrier and flattens the bowl structure. The role of the peri hydrogen repulsion as a causative factor for such a behavior is disputed, the structure-energy relationships in this class of compounds were shown to fit with a mixed quartic-quadratic potential. 相似文献
83.
Suja Haridas C.S. Deepa K Sreejarani Sankaran Sugunan 《Reaction Kinetics and Catalysis Letters》2003,79(2):373-379
Concentrated (0.2 M) aqueous solutions of HP-acids, such as H3+x+mPVIV
mVV
x-mMo12-xO40 and their analogues with an excess VO2+ cation, are oxidized by dioxygen at 343 K and atmospheric pressure through intermediate active complexes (IAC) [Hx+m-1PVIV
mVV
x-mMo12-xO40
4
-] · [VO2+]y · O2, where m + y ≥ 3. The electron transfer to the coordinated O2 molecule inside AC is the limiting stage at high m. At low m, the formation of IAC becomes the limiting stage that results in a sharp decrease in the oxidation rate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
84.
Jenkins CL Lin G Duo J Rapolu D Guzei IA Raines RT Krow GR 《The Journal of organic chemistry》2004,69(25):8565-8573
Among the proteinogenic amino acids, only proline is a secondary amine and only proline has a saturated ring. Electronegative substituents on C-4 (that is, C(gamma)) have a substantial effect on the trans/cis ratio of the prolyl peptide bond and the pucker of the pyrrolidine ring. 2-Azabicyclo[2.1.1]hexane is, in essence, a proline analogue with two C(gamma) atoms, one in each of the two prevalent ring puckers of proline. Here, 2-azabicyclo[2.1.1]hexane analogues of 2S-proline, (2S,4S)-4-hydroxyproline, and (2S,4S)-4-fluoroproline residues were synthesized, and their trans/cis ratios were shown to be invariant in a particular solvent. Thus, the substitution of a proline residue on C-4 affects the trans/cis ratio by altering the pucker of its pyrrolidine ring. This finding has implications for the conformation of collagen, which has an abundance of 2S-proline and (2S,4R)-4-hydroxyproline residues, and can be stabilized by (2S,4R)-4-fluoroproline and (2S,4S)-4-fluoroproline residues. 相似文献
85.
Kar S Sarkar B Ghumaan S Janardanan D van Slageren J Fiedler J Puranik VG Sunoj RB Kaim W Lahiri GK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(17):4901-4911
The symmetrically dinuclear title compounds were isolated as diamagnetic [(bpy)2Ru(mu-H2L)Ru(bpy)2](ClO4)2 (1-(ClO4)2) and as paramagnetic [(acac)2Ru(mu-H2L)Ru(acac)2] (2) complexes (bpy=2,2'-bipyridine; acac- = acetylacetonate = 2,4-pentanedionato; H2L = 2,5-dioxido-1,4-benzoquinonediimine). The crystal structure of 22 H2O reveals an intricate hydrogen-bonding network: Two symmetry-related molecules 2 are closely connected through two NH(H2L2-)O(acac-) interactions, while the oxygen atoms of H2L2- of two such pairs are bridged by an (H2O)8 cluster at half-occupancy. The cluster consists of cyclic (H2O)6 arrangements with the remaining two exo-H2O molecules connecting two opposite sides of the cyclo-(H2O)6 cluster, and oxido oxygen atoms forming hydrogen bonds with the molecules of 2. Weak antiferromagnetic coupling of the two ruthenium(III) centers in 2 was established by using SQUID magnetometry and EPR spectroscopy. Geometry optimization by means of DFT calculations was carried out for 1(2+) and 2 in their singlet and triplet ground states, respectively. The nature of low-energy electronic transitions was explored by using time-dependent DFT methods. Five redox states were reversibly accessible for each of the complexes; all odd-electron intermediates exhibit comproportionation constants K(c)>10(8). UV-visible-NIR spectroelectrochemistry and EPR spectroscopy of the electrogenerated paramagnetic intermediates were used to ascertain the oxidation-state distribution. In general, the complexes 1n+ prefer the ruthenium(II) configuration with electron transfer occurring largely at the bridging ligand (mu-H2Ln-), as evident from radical-type EPR spectra for 13+ and (+. Higher metal oxidation states (iii, iv) appear to be favored by the complexes 2m; intense long-wavelength absorption bands and RuIII-type EPR signals suggest mixed-valent dimetal configurations of the paramagnetic intermediates 2+ and 2-. 相似文献
86.
A sensitive spectrophotometric method for the determination of hydroxylamine is described. The method is based on the oxidation of hydroxylamine to nitrite using sodium arsenate under alkaline condition. The formed nitrite is determined based on the diazo coupling reaction between p-nitroaniline and N-(1-naphthyl)ethylenediamine dihydrochloride [NEDA]. The system obeys Beer's law over the concentration range 0-7 microg of hydroxylamine at 545 nm and the colour is stable for 3 h. The molar absorptivity of the colour system is found to be 6.7 x 10(4) l mol(-1) cm(-1). The relative standard deviation is 1.2% for ten determinations at 4 microg of hydroxylamine. Interferences due to various foreign ions have been studied and the method has been applied to the determination of hydroxylamine and its derivatives used in pharmaceutical formulations after hydrolysis. 相似文献
87.
Kelly DR Baker SC King DS de Silva DS Lord G Taylor JP 《Organic & biomolecular chemistry》2008,6(4):787-796
During studies directed towards the discovery of nitrile hydrolysing enzymes from thermophiles, vanillin aldoxime was incubated with the thermophilic organism, Geobacillus sp. DDS012 isolated from Italian rye grass (Lolium multiflorum) silage. The predominant product was a dihydro-dimer, which could only be characterised by LC-MS. This was initially imagined to be the product of cycloaddition of vanillin aldoxime with the corresponding nitrile oxide, but preparation of the supposed adduct and model studies excluded this possibility. The rate constant for the second order dimerisation of 4-O-acetyl vanillin nitrile oxide was measured (1.21 x 10(-4) M(-1) s(-1), 0.413 M, 25 degrees C) and the (13)C-NMR signal for the nitrile oxide carbon was observed (delta(C) 34.4, br. t (1)J(13)C,(14)N circa 50 Hz). Treatment of vanillin aldoxime with potassium persulfate and iron sulfate gave material with the same LC-MS properties as the natural product, which is therefore identified as 5,5'-dehydro-di-(vanillin aldoxime) 1d formed by phenolic oxidative coupling. 相似文献
88.
Krow GR Gandla D Guo W Centafont RA Lin G DeBrosse C Sonnet PE Iii CW Ramjit HG Carroll PJ Cannon KC 《The Journal of organic chemistry》2008,73(6):2114-2121
Additions of iodonium-X reagents to N-alkoxycarbonyl-2-azabicyclo[2.2.1]hept-5-enes and the homologous 2-azabicyclo[2.2.2]oct-5-enes have been found to mirror the outcomes of additions of bromonium-X reagents. Only rearranged products were observed for reactions of either of these halonium ion reagents with the azabicylo[2.2.1]hept-5-enes. For the azabicyclo[2.2.2]oct-5-enes, nitrogen participation in addition of IOH or BrOH was dependent on the N-alkoxycarbonyl group. With larger N-Boc, N-Cbz, or N-Troc protecting groups, unrearranged 5-anti-hydroxy-6-syn-I(or Br)-2-azabicyclo[2.2.2]octanes were formed by nucleophilic attack at C(5) on syn-halonium ions. The structure of N-methyl-8-anti-bromo-4-anti-hydroxy-2-azabicyclo[3.2.1]octane has been reassigned by X-ray analysis. 相似文献
89.
90.
The sol-gel technique has been employed for synthesizing three precursor materials for the deposition of tungsten oxide based electrochromic films. The ion-exchange route yields tungstic acid precursor (ITA) which has a strong tendency to polymerize rapidly. Addition of hydrogen peroxide and/or acetic acid suppresses the gelation process and an ethanol soluble precursor material (AIPTA) possessing a low degree of polymerization and high chemical stability is obtained. Another precursor material APTA endowed with similar desirable characteristics is produced from direct reaction between tungsten metal powder and a mixture of hydrogen peroxide and acetic acid. These materials were characterized by FTIR and absorption edge studies and compared in terms of their degree of polymerization and modes of association of various functionalities with the tungsten metal ion. 相似文献