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971.
碘离子的氧化与碘单质的分离是海带中碘元素分离的关键步骤。采用反加试剂法改进碘离子氧化步骤,采用水蒸气蒸馏法改进碘单质的分离,达到了实验现象明显,终点判断简单,分离度高,环境污染少的优点。 相似文献
972.
The synthesis of naproxen-containing diaryliodonium salts has been realized from naproxen methyl ester and ArI(OH)OTs activated by trimethylsilyl trifluoromethanesulfonate (TMSOTf) in a solvent mixture comprising dichloromethane and 2,2,2-trifluoroethanol (TFE). Those iodonium salts have been successfully used in the functionalization of an aromatic ring of naproxen methyl ester, including fluorination, iodination, alkynylation, arylation, thiophenolation, and amination and esterification reactions. Moreover, further hydrolysis of the obtained 5-iodo-naproxen methyl ester afforded 5-iodo-naproxen. 相似文献
973.
The Ti–TPyP reagent, i.e. an acidic aqueous solution of the oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato] titanium(IV) complex,
TiO(tpyp), was developed as a highly sensitive and selective spectrophotometric reagent for determination of traces of hydrogen
peroxide. Using this reagent, determination of hydrogen peroxide was performed by flow-injection analysis with a detection
limit of 0.5 pmol per test. The method was actually applied to determination of several constituents of foods, human blood,
and urine mediated by appropriate oxidase enzymes. The reaction specificity of the TiO(tpyp) complex for hydrogen peroxide
was clarified from the viewpoint of the reaction mechanisms and molecular orbitals based on ab initio calculations. The results
provided a well-grounded argument for determination of hydrogen peroxide using the Ti–TPyP reagent experimentally. This review
deals with characterization of the high sensitivity and reaction specificity of the Ti–TPyP reagent for determination of hydrogen
peroxide, to prove its reliability in analytical applications.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
974.
The prediction of drug metabolism is an important task in drug development. Besides well-established in vitro and in vivo
methods using biological matrices, several biomimetic models have been developed. This review summarizes three different nonenzymatic
strategies, including metalloporphyrins as surrogates of the active centre of cytochrome P450, Fenton’s reagent, and the electrochemical
oxidation of drug compounds. Although none of the systems can simulate the whole range of cytochrome P450-catalyzed reactions
adequately, the biomimetic models show some advantages over standard in vitro methods. For example, metalloporpyhrin catalysts
allow the synthesis of certain metabolites in sufficient amounts and with sufficient purities to permit characterization and
further pharmacological and toxicological tests. The electrochemical generation of metabolites coupled on-line to liquid chromatography/mass
spectrometry is a promising tool for studying reactive metabolites and can be applied in automated high-throughput screening
approaches. In this paper, detailed comparisons with cytochrome P450 catalysis are drawn, advantages and disadvantages of
the respective methods are revealed, and possible applications are discussed. 相似文献
975.
Ping Yin Rongjun Qu Hou Chen Yuan Tian Gui Yin Chongrong Bao 《Central European Journal of Chemistry》2008,6(3):438-442
Theoretical studies on the thermodynamic and kinetic properties of the reactions of scandium (I) ion with the sulfur-transfer
reagent SCO via the C-O bond activation pathway have been carried out over the temperature range of 200-1200 K using the DFT/B3LYP
method, general statistical thermodynamics, and Eyring transition state theory with Wigner correction. The relevant reactions
include reaction 1
1Sc+ + SCO → 1IM1 → 1TS1 → 1IM2 (Step 1) → 1TS2 → 1IM3 → 1ScO+ + 1CS (Step 2), and reaction 2
3Sc+ + SCO → 3IM1 → CP → 1IM2 → 1TS2 → 1IM3 → 1ScO+ +1CS in which the spin multiplicity changes from the triplet state to the singlet state in the crossing region. It was concluded
that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding
exoergic energies, ΔE, and reaction barriers, respectively. Step 2 of reaction 1 is both thermodynamically and kinetically favored over the whole temperature range. Moreover, both Reaction 1 and reaction 2 are exothermic and spontaneous processes in which their entropy increases, and the magnitudes of their thermodynamic values
all decrease with increasing temperature.
相似文献
976.
Lanfranchi DA Blanc MC Vellutini M Bradesi P Casanova J Tomi F 《Magnetic resonance in chemistry : MRC》2008,46(12):1188-1194
The (13)C NMR behaviour of 21 p-menthanic terpene bearing an oxygenated function (alcohol, ketone, acetate) was examined in the presence of a chiral lanthanide shift reagent (Yb(hfc)(3)). For each monocyclic compound, we measured the lanthanide-induced shift (LIS) on the signals of the carbons and the splitting of signals allowing the enantiomeric differentiation. Some general features were found about their LIS behaviour: experimental data establishing distinct patterns for carvomenthone-like compounds and menthone-like compounds. The enantiomeric splitting was observed for the majority of signals in the spectrum of each compound. In the case of alcohols and acetates, the influence of the relative stereochemistry (cis vs trans) of isopropyl(ene) and the binding function was discussed. 相似文献
977.
978.
2-芳基硫代芳胺的结构广泛存在于许多具有重要生理、药理活性的天然产物、药物以及材料当中, 研究此类结构的构建对这些化合物的合成路线设计可以提供新的思路. 传统合成2-芳基硫代芳胺, 常需多步骤或高温、强碱条件下进行, 能进行此类反应的反应物有限, 所得产物收率不高. 选用三氟乙酰基作为芳胺氮原子上的保护基, 利用三氟乙酰基的邻位促进效应, 并采用碘化亚铜/L-脯氨酸的催化体系, 在乙二醇二甲醚中, 碳酸钾为碱, 于60 ℃一步实现N-三氟乙酰基邻碘代苯胺与芳基硫酚的偶联, 以高产率获得了N-三氟乙酰基-2-芳基硫代芳胺. 反应条件温和, 催化体系价廉易得, 反应操作简便. 相似文献
979.
A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the separation and analysis of d- and l-thyroxine was developed using R(−)/S(+)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole, [R(−)/S(+)-DBD-PyNCS] as a chiral derivatization reagents. The T4 derivatives with R(−)-DBD-PyNCS were efficiently separated on a reversed-phase column with water-acetonitrile containing 0.1% formic acid (41:59, v/v) as the eluent and analyzed using ESI-MS with negative selected ion monitoring (SIM) mode. The calibration curves of both the d-T4 and l-T4 were linear over the concentration range of 0.13-13 μg/ml. The detection limits (S/N = 3) were 28 ng/ml for d-T4 and 40 ng/ml for l-T4, respectively. The relative standard deviations (RSD, n = 5) were less than 3.6% at 1.3 μg/ml for both T4 enantiomers. The proposed method was applied to the determination of l-T4 enantiomer in a pharmaceutical formulation. 相似文献
980.
Omran A. Omran Kim L. Larsen Reinhard Wimmer Donghong Yu 《Monatshefte für Chemie / Chemical Monthly》2008,139(9):1103-1108
Tetra- and tri-thioated derivatives of tetrakis[(ethoxycarbonyl)methoxy]tetrathiacalix[4]arenes were synthesized by thionation
with Lawesson’s reagent in dry toluene. The prepared compounds’ structures were investigated by FT-IR, 1H NMR, 2D-NMR, MALDI-TOF-MS, and X-ray crystallography.
Correspondence: Omran A. Omran, Chemistry Department, Faculty of Science, Sohag University, Sohag 82524 Egypt. 相似文献