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961.
962.
Ping Cheng Kuang Xu Yan Chi Chen Ting Ting Wang Yu Chen Cheng Long Yang Shi Ying Ma Yong Liang Hui Ming Ge Rui Hua Jiao 《Tetrahedron letters》2019,60(26):1706-1709
Chemical study of the insect-derived bacterium, Streptomyces sp. NA4286, led to the discovery of four new polyketides, murayaquinones B-E (1–4), together with a known compound, murayaquinone (5). The structures of new compounds (1–4) were determined by extensive analysis of their NMR and HRESIMS data. The absolute configuration of (+)-1 and (?)-1 was assigned through comparison of experimental and calculated ECD spectra. Murayaquinone D (3) exhibited potent cytotoxic activities against six human cancer cell lines with IC50 values ranging from 1.03 to 9.99 μM. 相似文献
963.
Cheng-Li Jiao Shuang Wang Xiao-Liang Si Zhi-Bao Li Shuang Liu Jian Zhang Li-Xian Sun Fen Xu Yu-Jia Sun Huai-Ying Zhou Yutaka Sawada 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1565-1571
A 3D supramolecule (H3O)2[Cu(2,6-pdc)2]·H2O (pdc = pyridinedicarboxylate) has been solvothermally synthesized and characterized by X-ray powder diffraction and FT-IR spectrum. The thermal decomposition characteristics of the complex were investigated by thermogravimetric analysis, which revealed a three-step mass loss process. The low-temperature molar heat capacities of crystalline (H3O)2[Cu(2,6-pdc)2]·H2O were measured by temperature-modulated differential scanning calorimetry for the first time. A phenomenon of glass transition was observed. The thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the above molar heat capacity data. 相似文献
964.
965.
Jianzhong Xu Zhanmeng He Weihong Wu Haiyun Ma Jixing Xie Hongqiang Qu Yunhong Jiao 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1341-1350
Hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene (HHPCP) is prepared and characterized by FTIR, 1H-NMR, and 31P-NMR spectroscopy. Then an investigation of the flame retardancy, thermal decomposition behavior of epoxy resin (EP) containing HHPCP is carried out using limiting oxygen (LOI) test, horizontal flame test, smoke density rate (SDR) test, thermogravimetric analysis (TG), and thermal gravimetric analyzer-mass spectrometry (TG-MS). The decomposition process of HHPCP is studied by TG-MS and FTIR. The result shows that the LOI value of EP increase from 20.5 to 26.5 %, when 7.5 mass% HHPCP is added into EP. The addition of 1 mass% nano-montmorillonite (nMMT) into EP–7.5 mass% HHPCP sample as synergist can increase the LOI value of EP–7.5 mass% HHPCP–1 mass% nMMT sample from 26.5 to 27.5 %. The SDR test indicates that smoke suppression of HHPCP on EP is not significant. TG analysis reflects that the EP–7.5 mass% HHPCP sample and EP–7.5 mass% HHPCP–1 mass% nMMT show higher thermal stability properties with an increasing T onset and T max comparing with neat-EP. TG-MS result indicates that the main pyrolysis product of EP is H2O, CO, CO2, C6H6, C6H5OH, HOC6H4CH3, and flammable hydrocarbon fragments CxHy. Compared with neat-EP sample, nonflammable water vapor of EP–7.5 mass% HHPCP sample increased, whereas CO2 and the flammable hydrocarbon fragments CxHy and flammable gas CO decreased. TG-MS and FTIR result suggests that HHPCP decomposed first by inter-molecular dehydration, then P–N hexatomic ring of HHPCP decomposed during 470 and 560 °C, and a little no-flame gas containing nitrogen element volatilized into the gaseous phase. 相似文献
966.
Jiao J Long GJ Grandjean F Beatty AM Fehlner TP 《Journal of the American Chemical Society》2003,125(25):7522-7523
The suitability of [{(eta5-C5H5)Fe(eta5-C5H4)}4(eta4-C4)Co(eta5-C5H5)][PF6]2, [1][PF6]2, for use as a molecular quantum cellular automata (QCA) cell is demonstrated. To this end the structure of 1 in the solid state and the conversion of 1 to mono- and dicationic mixed-valence complexes have been accomplished. The latter compounds have been isolated as pure materials and characterized by IR, EPR, and M?ssbauer spectroscopies and single-crystal XRD (monocation only) and magnetic susceptibility measurements. Near-IR spectra demonstrate the mixed valence character of the cations (valence trapped on the IR, EPR and M?ssbauer time scales), and the energies of the intervalence charge-transfer bands provide a measure of the hole hopping frequency. 相似文献
967.
Jiao H Costuas K Gladysz JA Halet JF Guillemot M Toupet L Paul F Lapinte C 《Journal of the American Chemical Society》2003,125(31):9511-9522
Density functional theory has been used to probe the bonding and electronic properties of the homo- and heterobimetallic sp carbon chain complexes (ML(m), = (eta(5)-C(5)R(5))(eta(2)-R(2)PCH(2)CH(2)PR(2))Fe, (eta(5)-C(5)R(5))(NO)(PR(3))Re; z = 0-4). All neutral complexes are best described by MCtbd1;CCtbd1;CM electronic structures, in accord with much experimental data. The singlet dications are best described by cumulenic (+)M=C=C=C=C=M(+) valence formulations. However, the diiron and rhenium/iron dications are found to possess triplet states of nearly identical energy, clarifying experimental magnetic data. Their electronic structures have dominant *(+)MCtbd1;CCtbd1;CM(+)* character, with some spin delocalization onto the carbon chain. The mixed valence monocation radicals exhibit delocalized unpaired electrons, in accord with class III (strongly coupled) and II (weakly coupled) assignments made from experimental data earlier, with some spin density on the carbon chain. An isolable diiron trication has a doublet ground state, but some computational data suggest a close-lying quartet. For the unknown diiron tetracation, a bis(carbyne) or (2+)Fetbd1;CCtbd1;CCtbd1;Fe(2+) electronic structure is predicted. Calculated adiabatic ionization potentials show the iron endgroup to be more electron-releasing than rhenium, in accord with electrochemical data. This polarizes the electronic structures of the rhenium/iron complexes. To help validate the computed model structures, crystal structures of ((eta(5)-C(5)Me(5))Fe(eta(2)-dppe))(2)(mu-C(4)) and [((eta(5)-C(5)Me(5))Fe(eta(2)-dippe))(2)(mu-C(4))](3+) 3PF(6)(-) are determined. Data are analyzed with respect to related diruthenium and dimanganese complexes. 相似文献
968.
The preparation of methyl 2‐methylazulene‐1‐carboxylate (1) was carried out in the presence of molecular sieves to obtain a good yield. The product was subjected to bromination under different reaction conditions to obtain methyl 1‐bromo‐2‐methylazulene‐1‐carboxylate (2) and methyl 1‐bromo‐2‐(bromomethyl) azulene‐1‐carboxylate (3). 相似文献
969.
The interactions between β‐cyclodextrin (β‐CD) and the mixtures of cationic‐anionic surfactants in aqueous solution were investigated by surface tension and 1H NMR measurements. It was shown that the critical micelle concentration (cmc) increased linearly with the increase of β‐CD concentration. Furthermore, β‐CD formed 1∶1 inclusion complex with both cationic and anionic surfactants in the mixed surfactant systems, and no significant selective inclusion was observed. The thermodynamic parameters of the inclusion process of β‐CD to mixed cationic‐anionic surfactants were calculated by a numerical method based on the surface tension measurements, and it was found that the inclusion process was both enthalpy and entropy favorable. 相似文献
970.
Phenolic and polymethoxylated flavones are important bioactive components in citrus fruit. Here, a rapid and sensitive method based on ultra-high performance liquid chromatography coupled with triple-quadrupole mass spectrometry (UHPLC-QqQ-MS) was developed for the simultaneous determination of phenolic and polymethoxylated flavones in the peels and pulp of mandarins, tangelos, and oranges. Three phenolic acids and eight flavonoids, including polymethoxylated flavones, were separated and determined using positive and negative ion modes in a single chromatographic run of only 11?min using the multiple reaction monitoring detection mode. The method was validated with high recoveries from 96.1% to 103.5%, good precision with interday relative standard deviations less than or equal to 7.3%, intraday relative standard deviations ≤2.64%, low limits of detection from 1.0 to 18?µg L–1, and low limits of quantitation in the range from 3.0 to 61?µg L–1. The application of this UHPLC-QqQ-MS/MS method to the citrus extracts of three cultivars showed that mandarin fruits contained the highest total amounts of the 11 analytes, followed by tangelos and oranges. This study provides a reliable and quantitative method that can be used for the development of functional products and quality evaluation of citrus fruits. 相似文献