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161.
Jian Zhang Hui Huang Da-Fu Wei Yong Guan Fu-Zeng Hu Anna Zheng 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):626-632
Sequential anionic copolymerization of styrene and glycidyl methacrylate (GMA) was performed with the protection of argon under normal pressure, where styrene, GMA, toluene, THF, n-butyllithium and a small amount of lithium chloride (LiCl) were used as first monomer, second monomer, solvent, polar reagent, initiator and additive, respectively. Polystyrene-b-poly(glycidyl methacrylate) diblock copolymers (PS-b-PGMA) with well-defined structure and narrow molecular weight distribution were prepared by the copolymerization reaction of poly(styryl)lithium with GMA under certain temperatures. The copolymers were characterized using gel permeation chromatography (GPC), 1H-NMR, 13C-NMR, thin layer chromatography (TLC) and hydrochloric acid-dioxane argentimetric methods. The effects of additives, copolymerization temperature and THF dosage on the copolymerization were studied. No chain transfer reaction of anionic polymerization of styrene in toluene was observed. Slightly broader molecular weight distribution of PS-b-PGMA was observed with the increase the GMA repeat units. Using THF/toluene blend solvent could reduce the polydispersity index (M w /M n ) and dissolve the copolymer better than toluene alone. Lower temperature (< -40°C) and LiCl are required to prepare PS-b-PGMA with narrower molecular weight distribution. 相似文献
162.
Xiantong Guan Bing Ding Xiaofeng Liu Jiajia Zhu Changhuan Mi Xiaogang Zhang 《Journal of Solid State Electrochemistry》2013,17(7):2087-2093
Li-rich layered Li1.2Ni0.2Mn0.6O2 has been surface modified by nickel–manganese composite oxide (Ni0.5Mn1.5O x ) to serve as a novel cathode material with novel layered spinel structure for lithium-ion battery. The as-prepared Li1.2Ni0.2Mn0.6O2 before and after surface modification by Ni0.5Mn1.5O x as well as simply blended Li1.2Ni0.2Mn0.6O2 with spinel LiNi0.5Mn1.5O4, have been characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electronic microscopy, and differential scanning calorimetry. Electrochemical studies indicate that the Ni0.5Mn1.5O x surface modified Li1.2Ni0.2Mn0.6O2 with peculiar layered spinel character dramatically represented increased discharge capacity, improved cycling stability as well as excellent rate capability at high-voltage even up to 5.0 V. 相似文献
163.
2β,3α-Dihydroxyurs-12-en-28-oic acid(6) is a naturally occurring diastereoisomer of corosolic acid with glycogen phosphorylase inhibitory activity.A new strategy for the semi-synthesis of 6 was developed.Using the commercially available ursolic acid(1) as the starting materials,6 was synthesized through five facile reactions with a high stereoselectivity and an overall yield of 47.3%.The structure of 6 was confirmed by optical rotation.ESI-MS,1H NMR and 13C NMR data. 相似文献
164.
Addition of nitroalkanes into n‐alkanes can lower the activation barriers of free‐radical production and accelerate the decomposition of n‐alkanes at relatively low temperatures. Four initial decomposition mechanisms of the n‐butane/nitroethane binary mixture were proposed for the promoting effect and considered theoretically at the B3LYP, BB1K, BMK, MPW1K, and M06‐2X levels with MG3S basis set. Energetics above was compared to high‐level CBS‐QB3 and G4 calculations. Calculated results confirm the feasibility of the four initial decomposition pathways: (I) the C? NO2 bond rupture of nitroethane to produce ethyl and ·NO2, (II) HONO elimination from nitroethane followed by decomposition to ·OH and ·NO, (III) rearrangement of nitroethane to ethyl nitrite which further dissociates into CH3CH2O· and ·NO, and (IV) direct hydrogen‐abstraction of nitroethane with n‐butane. 相似文献
165.
Qing Wang Dongya Yang Guorong Cao Yijun Guan Lin Zhuang 《International Journal of Polymer Analysis and Characterization》2013,18(1):40-56
The bisazo chromophore molecule (CAAPM) and helical biphenyl bisazo polyurethane (HBBPU) were synthesized. The structures of CAAPM and HBBPU were characterized by FT-IR and UV-vis spectroscopic techniques. The measurements of refractive index and thermo-optic coefficient (dn/dT) of HBBPU were demonstrated at different wavelengths and different temperatures by the ATR technique. By using CCD digital imaging devices, transmission loss of the internal waveguide was measured. The refractive index dispersions and Sellmeyer coefficients of HBBPU were obtained by the Sellmeyer equation. A Y-branched switch based on the thermo-optic effect was proposed and the performance of the switch was simulated. With a branching angle of 0.143° and the FD-BPM method, the result showed that the power consumption of the thermo-optic switch could be only 3.6 mW, and the response time of the switch could reach about 8 ms. This is a significant improvement in reducing power consumption compared with the normal Y-branched polymer thermo-optic switch. 相似文献
166.
Fuyu Guan Cornelius E. Uboh Lawrence R. Soma Mary Robinson George A. Maylin Xiaoqing Li 《Analytical and bioanalytical chemistry》2013,405(14):4707-4717
Dermorphin is a unique opioid peptide that is 30–40 times more potent than morphine. It was misused and went undetected in horse racing until 2011 when intelligence obtained from a few North American race tracks suggested its use. To prevent such misuse, a reliable analytical method became necessary for detection and identification of dermorphin in post-race horse samples. This paper describes the first liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for such a purpose. Equine plasma and urine samples were pre-treated with ethylenediamine tetra-acetic acid and urea prior to solid-phase extraction (SPE) on Oasis MCX cartridges. Resulting eluates were dried under vacuum and analyzed by LC–MS/MS for dermorphin. The matrix effect, SPE efficiency, intra-day and inter-day accuracy and precision, and stability of the analyte were assessed. The limit of detection was 10 pg/mL in plasma and 20 pg/mL in urine, and the limit of confirmation was 20 pg/mL in plasma and 50 pg/mL in urine. Dermorphin in plasma is stable at ambient temperature, but its diastereomer is unstable. With isotopically labeled dermorphin as an internal standard, the quantification range was 20–10,000 pg/mL in plasma and 50–20,000 pg/mL in urine. The intra-day and inter-day accuracy was from 91 % to 100 % for the low, intermediate, and high concentrations. The intra-day and inter-day coefficients of variation were less than 12 %. The method differentiates dermorphin from its diastereomer. This method is very specific for identification of dermorphin in equine plasma and urine, as assessed by BLAST search and targeted SEQUEST search, and by MS/MS spectrum library search. The method has been successfully applied to analysis of samples collected following dermorphin administration to research horses and of official post-race samples. Figure
? 相似文献
167.
Jiamin Gu Reihong Feng Zhiyuan Wu Shuguang Guan Jiling Guo Chunru Cheng Pingping Xu Jingxian Zhang Yang Wang Hua Qu Wei Man Wenbo Yu Yajun Cui Shuhong Guan Dean Guo 《Journal of separation science》2013,36(14):2366-2372
A rapid and convenient method was established to preparatively isolate the three ellagic acid types of compounds, which were the main polyphenols in Euphorbia pekinensis, by flexibly applying solvent extraction combined with counter‐current chromatography (CCC). The total extract (extracted using 95% ethanol) of E. pekinensis was pretreated by two simple steps before CCC isolation, following the procedure: the total extract was extracted by classical solvent extraction using petroleum ether and ethyl acetate, respectively, and then the ethyl acetate extract was suspended using 95% ethanol, after being allowed to stand overnight, the sediment was obtained. Partial sediment (100 mg) was then directly separated by CCC with a two‐phase solvent system composed of chloroform‐95% ethanol‐water‐85% formic acid (50:50:50:5, v/v/v/v). About 22 mg of 3,3′‐dimethoxy ellagic acid (1), 12 mg of 3,3′‐di‐O‐methyl‐4‐O‐(β‐d ‐xylopyranosyl)ellagic acid (2), and 35 mg of ellagic acid (3) with purities of 96.0, 95.2, and 95.4% were obtained respectively in one step within 4 h. After being purified by washing with methanol, the purities of the three compounds obtained were all above 98%. The purities were determined by HPLC and their chemical structures were further identified by 1H and 13C NMR spectroscopy. The recoveries were calculated as 84.6, 85.7, and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for the preparative separation of polyphenols from E. pekinensis. 相似文献
168.
Science China Chemistry - Three novel transition metal complexes [ML2(phen)]·H2O (M= Mn, Co, Zn; HL= C10H7O2NSe, 2-phenyl-4-selenazole carboxylic acid, phen= 1,10-phenanthroline) 1~3... 相似文献
169.
The electronic structure and redox properties of the highly oxidizing, isolable RuV?O complex [RuV(N4O)(O)]2+, its oxidation reactions with saturated alkanes (cyclohexane and methane) and inorganic substrates (hydrochloric acid and water), and its intermolecular coupling reaction have been examined by DFT calculations. The oxidation reactions with cyclohexane and methane proceed through hydrogen atom transfer in a transition state with a calculated free energy barrier of 10.8 and 23.8 kcal mol?1, respectively. The overall free energy activation barrier (ΔG≠=25.5 kcal mol?1) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of [RuIII(N4O)(HOCl)]2+ (ΔG=15.0 kcal mol?1) and the substitution of HOCl by a water molecule (ΔG≠=10.5 kcal mol?1). For water oxidation, nucleophilic attack on RuV?O by water, leading to O? O bond formation, has a free energy barrier of 24.0 kcal mol?1, the major component of which comes from the cleavage of the H? OH bond of water. Intermolecular self‐coupling of two molecules of [RuV(N4O)(O)]2+ leads to the [(N4O)RuIV? O2? RuIII(N4O)]4+ complex with a calculated free energy barrier of 12.0 kcal mol?1. 相似文献
170.
Li Yao Saijing Zheng Yafeng Guan Jun Yang Baizhan Liu Weimiao Wang Xiaolan Zhu 《Analytica chimica acta》2013
Determination of the tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its N- and O-glucuronides (NNAL-N-Gluc and NNAL-O-Gluc) is important for toxicology analysis of tobacco smoke induced carcinogenicity and the understanding of detoxification mechanisms of the carcinogenic nitrosamine in humans. But previously reported indirect measurement methods involving enzymolysis and base treatment steps were tedious and time-consuming. In this work, a direct measurement method for simultaneous determination of urinary NNAL, NNAL-N-Gluc and NNAL-O-Gluc by liquid chromatography–tandem mass spectrometry (LC–MS/MS) in a single run was developed for the first time without the need to perform enzymatic or base hydrolysis. Urine samples were purified using dichloromethane and further extracted by solid-phase extraction. Then they were analyzed by LC–MS/MS operated in electrospray positive ionization mode. Chromatographic separation was achieved on a Phenomenex Kinetex PFP column within 6 min. The proposed method was validated and the results demonstrated that the method can produce satisfactory recoveries and reproducibility for the analytes. The applicability of this newly developed method was investigated for the simultaneous analysis of the three metabolites in smokers’ urine and the obtained results were comparable to those detected using the conventional enzymolysis method. 相似文献