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991.
Li‐Jun Yang Kun Jiang Jun‐Jie Tan Shi‐Jin Qu Hong‐Feng Luo Chang‐Heng Tan Da‐Yuan Zhu 《Helvetica chimica acta》2013,96(1):119-123
Chemical investigation on the stem and root of Melicope pteleifolia afforded three new prenylated benzene metabolites as racemic mixtures, named pteleifolins A–C ( 1 – 3 , resp.). Their gross structures were elucidated on the basis of spectroscopic analysis, especially 2D‐NMR experiments. An enantiomer resolution of (±)‐ 1 using chiral HPLC was performed, and the absolute configuration of the enantiomers were determined to be (+)‐(S)‐ 1 and (?)‐(R)‐ 1 by means of circular‐dichroism analysis. 相似文献
992.
Bao-Min Wang Zhang Yuan Zhi-Qiang Guo Hai-Nan Ma Chuan Fook Lai 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(13):2253-2259
As a new nano-scale functional material, it is necessary to achieve a uniform distribution in the composites for gaining the CNFs’ excellent reinforcing effect. In this paper, CNFs were purified by the method of high temperature annealing treatment. Six surfactants, methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), sodium dodecyl sulfate (SDS), dodecylamine (DDA), N, N-dimethyl formamide (DMF) and cetyltrimethyl ammonium bromide (CTAB) were used individually and combinatorially in a certain concentration to disperse the CNFs in aqueous solution. To achieve a good dispersion of the CNFs, a method utilizing ultrasonic processing was employed. The CNFs treated by the method of high temperature annealing treatment were characterized by differential thermal analysis (DTA) and thermogravimetry analysis (TGA), and the ultrasonication-driven dispersion of CNFs in aqueous solutions were monitored by UVvis spectroscopy and transmission electron microscopy (TEM). The experiments reveal that the method of high temperature annealing treatment purified the CNFs and the maximum achievable dispersion of CNFs corresponds to the maximum UV absorbance of the solution. All results show that the surfactants mixture of MC and SDS in a certain concentration of 0.4 and 2.0 g/L has the maximum dispersion effect on CNFs in aqueous solution, the optimum concentration ratio of MC, SDS, and CNFs was 2: 10: 1. 相似文献
993.
A practical and efficient liquid‐phase synthesis of 3,4,5‐trisubstituted isoxazoles using poly(ethylene glycol) as supported is described. Soluble‐polymer‐supported nitrile oxide generated in situ reacted with chalcones to afford polymer‐supported isoxazolines, which were cleaved by sodium methoxide to generate 3,4,5‐trisubstituted isoxazoles instead of 3,4,5‐trisubstituted isoxazolines. This sequential process provided a novel method to synthesize 3,4,5‐trisubstituted isoxazoles. 相似文献
994.
A facile one‐pot synthesis of 2,5‐disubstituted oxazoles was developed via cyclization of aldoximes and phenylacetylene then dehydrogenation oxidation. 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone was studied for the selective oxidation of oxazolines using Cu2+/Li+ as catalyst and O2 as indirect oxidant. The reaction results showed that this catalyst system can effectively catalyze the oxidation of oxazolines to the corresponding oxazoles. Thus, a variety of polysubstituted oxazoles was easily synthesized in high yields by catalytic oxidation of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone/CuCl2/LiCl/O2. 相似文献
995.
Li Zhang Sheng-mei Yuan Li-ming Yang Zhen Fang Guang-chao Zhao 《Mikrochimica acta》2013,180(7-8):627-633
A glassy carbon electrode was modified with β-manganese dioxide (β-MnO2), and glucose oxidase (GOx) was immobilized on its surface. The β-MnO2 nanowires were prepared by a hydrothermal method and characterized by scanning electron microscopy and powder X-ray diffraction. They were then dispersed in Nafion solution and cast on the glassy carbon electrode (GCE) to form an electrode modified with β-MnO2 nanowires that exhibits improved sensitivity toward hydrogen peroxide. If GOx is immobilized in the surface, the β-MnO2 acts as a mediator, and Nafion as a polymer backbone. The fabrication process was characterized by electrochemical impedance spectroscopy, and the sensor and its materials were characterized by cyclic voltammetry and amperometry. The biosensor enables amperometric detection of glucose with a sensitivity of 38.2 μA?·?mM?1?·?cm?2, and a response time of?<?5 s. This study also demonstrates the feasibility of realizing inexpensive, reliable, and high-performance biosensors using MnO2 nanowires. Figure
The sensitive determination of glucose was realized at a β-MnO2 NWs modified glassy carbon electrode by amperometry. The relatively fast, reproducible and low-cost manufacturing procedure suggests that it can offer an excellent platform for glucose oxidase-biosensing applications. 相似文献
996.
Zhongke Yan Jianwei Zhao Lirong Qin Fan Mu Ping Wang Xining Feng 《Mikrochimica acta》2013,180(1-2):145-150
Granular nanowires with a diameter of about 60 nm were fabricated from cuprous oxide (Cu2O) by an electrochemical method using anodic aluminium oxide as the template. A non-enzymatic sensor for hydrogen peroxide (H2O2) was then developed on the basis of a gold electrode modified with Cu2O nanowires and Nafion. The resulting sensor enables the determination of H2O2 with a sensitivity of 745 μA?mM?1?cm?2, over a wide linear range (0.25 μM to 5.0 mM), and with a low detection limit (0.12 μM). The results demonstrate that the use of such granular nanowires provides a promising tool for the design of non-enzymatic chemical sensors. Figure
A non-enzymatic sensor for hydrogen peroxide (H2O2) was developed on the basis of a gold electrode modified with Cu2O nanowires and Nafion. The resulting sensor enables the determination of H2O2 with a sensitivity of 745 μA mM?1 cm?2, over a wide linear range (0.25 μM to 5.0 mM), and with a low detection limit (0.12 μM). The results demonstrate that the use of such granular nanowires provides a promising tool for the design of non-enzymatic chemical sensors 相似文献
997.
We are reviewing the state of electrochemical sensing of H2O2 based on the use of metal nanoparticles. The article is divided into subsections on sensors based on nanoparticles made from Ag, Pt, Pd, Cu, bimetallic nanoparticles and other metals. Some sensors display high sensitivity, fast response, and good stability. The review is subdivided into sections on sensors based on heme proteins and on nonenzymatic sensors. We also discussed the challenges of nanoscaled sensors and their future aspects. Figure
Sensing mechanism of (A) mediator-based enzyme biosensor, (B) mediator-less enzyme biosensor and (C) nonenzymatic sensors with metal nanoparticles for the electrocatalytic reduction toward H2O2 相似文献
998.
A transition-metal-free method for the synthesis of indolines has been developed. In the presence of K2CO3, the cyclization reaction of N-(ortho-chloromethyl)aryl amides and iodonium ylides proceeded smoothly at room temperature in moderate to good yields. 相似文献
999.
Two dinuclear succinato‐bridged nickel(II) complexes [Ni(RR‐L)]2(μ‐SA)(ClO4)2 ( 1 ) and [Ni(SS‐L)]2(μ‐SA)(ClO4)2 ( 2 ) (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy. Single crystal X‐ray diffraction analyses revealed that the NiII atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central NiII atoms in a bis bidentate fashion to form dimers in 1 and 2 . The monomers of {[Ni(RR‐L)]2(μ‐SA)}2+ and {[Ni(SS‐L)]2(μ‐SA)}2+ are connected by O–H ··· O and N–H ··· O hydrogen bonds into a 1D right‐handed and left‐handed helical chain along the b axis, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy. 相似文献
1000.
Quinoline bridged imidazolium precursors 5,8‐bis(N‐R‐imidazolylidenylmethylene)quinoline PF6– salts [H2L](PF6)2 [R = Me ( 1a ), R = naphthylmethyl ( 1b )] were prepared by quaternization of N‐methylimidazole and N‐naphthylmethylimidazole with 5,8‐bis(bromomethyl)quinoline, respectively. Reaction of the imidazolium ligands 1a and 1b with Hg(OAc)2 and Ag2O in acetonitrile gave the macrocyclic transition metal carbene complexes [Hg2L2](PF6)4 ( 2a and 2b ) and [Ag2L2](PF6)2 ( 3a and 3b ), respectively. All the N‐heterocyclic carbene complexes were characterized in detail by NMR, ESI‐MS, and elemental analysis. Structures of complexes 2a and 3a were determined by X‐ray diffraction studies. Structural studies revealed that the coordination arrangement of the central mercury atom in complex 2a displays a tricoordinate mode and the molecular conformation results in a“closed” form with the bridging quinoline functionality in the macrocycle, whereas the silver complex 3a does not show an coordiantion between the bridging quinoline and the AgI ion, which results in an “open” conformation of the macrocycle. The HgII and AgI NHC complexes showed similar UV absorption and luminescence in acetonitrile solutions. 相似文献