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91.
Highly effective direct synthesis of DMC from CH_3OH and CO_2 using novel Cu-Ni/C bimetallic composite catalysts 总被引:1,自引:0,他引:1
Novel Cu-Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH3OH and CO2. 相似文献
92.
Poly(trimethylene terephthalate)(PTT) is an excellent fiber material.Its thermal degradation and isothermal crystalline behaviors were in this study investigated using thermogravimetric analysis(TGA),thermogravimetric analysis-Fourier transform infrared spectroscopy(TGA-FTIR) analysis,differential scanning calorimetry(DSC) and X-ray diffraction(XRD).The thermal degradation mechanism of PTT follows Mclafferty rearrangement principle.The PTTwithintrinsicviscosity(Ⅳ) of 0.74 dL/g has a maximum crystallinity... 相似文献
93.
Zhong Lv Zhang Zhi Jie Sun Fei Xue Xian Jin Luo Nai Yun Xiu Li Teng Zong Gen Peng 《中国化学快报》2009,20(8):921-923
A series of novel benzimidazole derivatives was synthesized and their anti-Coxsackie virus B_3(CVB_3) activity was evaluated in VERO cells.Compounds 9 and 10 exhibited better inhibitory activity than those of ribavirin(RBV) with IC_(50) values of 5.30 and 1.06μg/mL,respectively. 相似文献
94.
Jonathan R.E. Thabano Michael C. BreadmoreJoseph P. Hutchinson Cameron JohnsPaul R. Haddad 《Journal of chromatography. A》2009,1216(25):4933-4940
Polymeric ion-exchange monoliths typically exhibit low capacities due to the limited surface area on the globules of the monoliths. The ion-exchange binding of protonated weakly basic analytes on deprotonated carboxylate sites on methacrylate polymer monoliths has been increased by templating the monoliths with silica nanoparticles. The templating method is achieved by adding the nanoparticles as a suspension to the polymerisation mixture. After polymerisation, the nanoparticles are removed by washing the monolith with strong base. Monolithic columns prepared using this procedure have exhibited a 33-fold increase in ion-exchange capacity when compared to untemplated monoliths prepared and treated under similar conditions. The templating procedure does not alter the macroporous properties of the polymer monolith, confirmed through scanning electron microscopy and BET surface area analysis, but provides increased capacity predominantly through the re-orientation of more carboxylic acid groups. The resulting increase in ion-exchange capacity has proven to be useful for the preconcentration and separation of neurotransmitters by in-line solid-phase extraction–capillary electrophoresis. The increased capacity of the templated monolith allowed the injection time to be increased 10 times over that of an untemplated monolith, allowing 10 times more sample to be injected with the efficiencies and recoveries remaining unaffected. The enhancement in sensitivity for the test mixture of neurotransmitter (dopamine, norepinephrine and metanephrine) ranged 1500–1900 compared to a normal hydrodynamic injection in capillary electrophoresis. Efficiencies obtained for the neurotransmitters were 100 000–260 000 plates, typical of those obtained in capillary zone electrophoresis. The applicability of the increased capacity silica nano-templated polymer monolith was demonstrated by analysing trace levels of caffeine in biological, food and environmental samples. 相似文献
95.
Mohamed Dawod Michael C. BreadmoreRosanne M. Guijt Paul R. Haddad 《Journal of chromatography. A》2009,1216(15):3380-3386
Electrokinetic supercharging (EKS) has been used in the last few years as a powerful tool for separation and on-line preconcentration of different types of analytes. We have developed a valuable modification for EKS system, namely counter-flow EKS (CF-EKS) and applied it for the separation and on-line preconcentration of seven non-steroidal anti-inflammatory drugs (NSAIDs) in water samples. In CF-EKS, a hydrodynamic counter-flow is applied during electrokinetic injection of the analytes within the EKS system. This counter-flow minimises the introduction of the sample matrix into the capillary, allowing longer injections to be performed. Careful choice of the optimum counter-flow as well as the optimum injection voltage allowed the sensitivity to be enhanced by 11,800-fold, giving limits of detection (LODs) of 10.7–47.0 ng/L for the selected NSAIDs. The developed method was validated and then applied for the determination of the studied NSAIDs in drinking water as well as wastewater samples from Hobart city. 相似文献
96.
Éadaoin Tyrrell Robert A. Shellie Emily F. Hilder Christopher A. Pohl Paul R. Haddad 《Journal of chromatography. A》2009,1216(48):8512-8517
A fast ion chromatographic system is described which uses shorter column lengths and compares various eluent profiles in order to maximise the performance without sacrificing the chromatographic resolution. Both isocratic and gradient elution profiles were considered to find the most efficient mode of separation. The separation and determination of seven target anions (chloride, chlorate, nitrate, chromate, sulfate, thiocyanate and perchlorate) was achieved using a short (4 mm ID, 50 mm long) column packed with Dionex AS20 high-capacity anion exchange material. A hydroxide eluent was used at an initial concentration of 25 mM (at a flow-rate of 1.0 mL/min) and two performance maxima were found. The maximum efficiency occurred at a normalised gradient ramp rate of 5 mM/t0, resulting in a peak capacity of 16, while the fastest separation (<3 min) occurred at a normalised ramp rate of 30 mM/t0. The retention time, peak width and resolution using the different eluent profiles on varying column lengths is also compared. Further investigations in this study determined that the highest peak capacity separation under gradient conditions could be approximated using an isocratic separation. The advantage of using this novel approach to approximate the maximum efficiency separation removes the need for column re-equilibration that is required for gradient elution resulting in faster analyses and enhanced sample throughput, with benefits in particular for multidimensional chromatography. 相似文献
97.
Rawhi H. Al‐Far Salim F. Haddad Basem Fares Ali 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(8):m321-m324
In the structural motifs of two isomorphous triclinic salts, (C5H6Br2N3)2[MBr4] (M = CdII and MnII), each [MBr4]2− anion interacts with eight surrounding 2,6‐diamino‐3,5‐dibromopyridinium cations through intermolecular C/N—H...Br and Br...Br interactions, leading to a three‐dimensional framework structure. The cations show a minor degree of π–π stacking, adding extra stability to the three‐dimensional architecture. 相似文献
98.
Rawhi H. Al‐Far Salim F. Haddad Basem Fares Ali 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(11):m451-m454
The structures of three isomorphous compounds, namely bis(2,6‐dibromopyridinium) tetrabromidocuprate(II) dihydrate, (C5H4Br2N)2[CuBr4]·2H2O, bis(2,6‐dibromopyridinium) tetrabromidocadmate(II) dihydrate, (C5H4Br2N)2[CdBr4]·2H2O, and bis(2,6‐dibromopyridinium) tetrabromidomercurate(II) dihydrate, (C5H4Br2N)2[HgBr4]·2H2O, show a crystal supramolecularity represented by M—Br...H—O—H...Br—M intermolecular interactions along with (π)N—H...OH2 hydrogen‐bonding interactions forming layers connected via aryl–aryl face‐to‐face stacking of cations, leading to a three‐dimensional network. The anions have significantly distorted tetrahedral geometry and crystallographic C2 symmetry. The stability of this crystal lattice is evidenced by the crystallization of a whole series of isomorphous compounds. 相似文献
99.
This paper develops semistability and uniform semistability analysis results for switched linear systems. Semistability is the property whereby the solutions of a dynamical system converge to Lyapunov stable equilibrium points determined by the system’s initial conditions. Since solutions to switched systems are a function of the system’s initial conditions as well as the switching signals, uniformity here refers to the convergence rate of the multiple solutions as the switching signal evolves over a given switching set. The main results of the paper involve sufficient conditions for semistability and uniform semistability using multiple Lyapunov functions and sufficient regularity assumptions on the class of switching signals considered. 相似文献
100.
Optical absorption bands at ~18772 and ~18807 cm-1, previously assigned to A2Δ-X2Π electronic origin band transitions of the linear carbon-chain radicals C5H and C5D, respec-tively, have been reinvestigated. The spectra have been recorded in direct absorption apply-ing cavity ring-down spectroscopy to a supersonically expanding acetylene/helium plasma. The improved spectra allow deducing a l-C5H upper state spin-orbit coupling constant A'=-0.7(3) cm-1 and a A2Δ lifetime of 1.6±0.3 ps. 相似文献