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941.
A commercially-available sulfonphthalein derivative was demonstrated to be a chemodosimeter for Fe2+ and its sensing behavior was further investigated by UV-vis spectroscopy in aqueous media under the optimum conditions. In the presence of chlorophenol red (CPR) and H2O2, the absorption maximum at 435 nm decreased upon addition of Fe2+, resulting in a significant color change of the CPR solution from yellow to colorless. The chemosensor system did not show significant responses to a series of other metal ions including Al3+, Zn2+, Cd2+, Hg2+, Mn2+, Co2+, Fe3+, Ni2+, Cu2+, La3+, Ce4+, Th4+, Pd2+, Pb2+, Sb3+, Cr3+, Au3+, Ag+, Nd3+, Sm3+, alkali and alkaline earth metal cations, allowing for highly selective naked-eye detection of Fe2+. Quantitative analysis was carried out kinetically for practicable the Fe2+ assay when either fixed time method or the initial rate method was applied. When the detecting time was set, the decrease of absorbance signal was linear with Fe2+ concentration in the range of 0 to 7.50 × 10?5 mol L?1 and the regression equation was ΔA = 0.00759 + 0.00593C Fe with a correlation coefficient r = 0.9953. The chemodosimetric system has employed an irreversible Fenton reagent-promoted oxidation of the CPR free chromophore and the hydroxyl radicals were generated in the presence of both Fe2+ and hydrogen peroxide. The mechanistic interpretation of the signaling process was partially confirmed by the radical scavenging experiment and the FT-IR analysis of the intermediates formed at different reaction periods. 相似文献
942.
An efficient one-pot route to synthesize tertiary alcohol compounds using Barbier–Grignard reaction of unactivated alkyl or aryl bromides with ester in THF at 65 °C catalyzed by CuO has been developed and systematically investigated. A wide range of substituted tertiary alcohol compounds were obtained in good to high yields. The reaction is highly chemoselective. The mechanism involving the leaving group of R2O-group is discussed. 相似文献
943.
944.
Two new neolignans, syripinnalignins A and B ( 1 and 2 , resp.), were isolated from the 95% EtOH extract of the stem of Syringa pinnatifolia Hemsl . var. alashanensis. The structures of 1 and 2 were elucidated by spectroscopic methods, including UV, IR, HR‐ESI‐MS, and extensive 1D‐ and 2D‐NMR techniques. 相似文献
945.
946.
947.
Linli Zhang Yitian Tang Zhaobin Han Kuiling Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5027-5031
A series of MnI complexes containing lutidine‐based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional‐group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth‐abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer‐sphere mode of substrate–catalyst interactions probably dominates the catalysis. 相似文献
948.
The combined nucleation effect of graphene oxide (GO) and calcium pimelate (CaPi) which are chemically compound together (expressed in GO ? CaPi) in isotactic polypropylene (iPP) was investigated. Fourier transform infrared (FTIR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA) verified that CaPi was chemically compound with GO by chelate bonds. The crystallization behavior and crystalline morphologies of iPP nucleated with different mass ratio of GO and CaPi were investigated. The crystallization peak temperature of iPP nucleated with 0.2 wt% GO ? CaPi with the mass ratio of 1:5 (GO1 ? C5) was increased by 8.3°C when compared with that of pure iPP, and the relative content of β‐crystal reached up to 0.7962. Whereas, the crystallization peak temperature of iPP nucleated with 0.2 wt% GO and CaPi which are blended together by mechanical force (expressed in GO + CaPi) with the mass ratio of 1:5 (GO1 + C5) was only increased by 5.0°C. It was attributed to that the aggregation of GO + CaPi caused the decrease of the crystallization peak temperature, while the GO1 ? C5 uniformly dispersed in the iPP matrix. Unexpectedly, the relative content of β‐crystal of iPP nucleated with 0.02 wt% GO1 ? C5 reached up to 0.8094, and the crystallization peak temperature was increased by 6.7°C compared with that of pure iPP. Meanwhile, the impact strength, tensile strength and heat deflection temperature of iPP nucleated with 0.02 wt% GO1 ? C5 increased by almost 45.86%, 2.03% and 7.7°C, respectively. The iPP nucleated with GO1 ? C5 obtained a balance between stiffness and toughness and the thermo‐mechanical property of nucleated iPP was improved. 相似文献
949.
Jean‐Franois Ayme Sbastien Dhers Jean‐Marie Lehn 《Angewandte Chemie (International ed. in English)》2020,59(30):12484-12492
Three imine‐based metal complexes, having no overlap in terms of their compositions, have been simultaneously generated from the self‐sorting of a constitutional dynamic library (CDL) containing three amines, three aldehydes, and three metal salts. The hierarchical ordering of the stability of the three metal complexes assembled and the leveraging of the antagonistic and agonistic relationships existing between the constituents within the constitutional dynamic network corresponding to the CDL were pivotal in achieving the sorting. Examination of the process by NMR spectroscopy showed that the self‐sorting of the FeII and ZnII complexes depended on an interplay between the thermodynamic driving forces and a kinetic trap involved in their assembly. These results also exemplify the concept of “simplexity”—the fact that the output of a self‐assembling system may be simplified by increasing its initial compositional complexity—as the two complexes could self‐sort only in the presence of the third pair of organic components, those of the CuI complex. 相似文献
950.
Zhenguang Wang Chuanchuan Zhang Henggang Wang Yuan Xiong Xinjian Yang Yu‐e Shi Andrey L. Rogach 《Angewandte Chemie (International ed. in English)》2020,59(25):9997-10002
Sulfur is not normally considered a light‐emitting material, even though there have been reports of a dim luminescence of this compound in the blue‐to‐green spectral region. Now, it is shown how to make red‐emissive sulfur by a two‐step oxidation approach using elemental sulfur and Na2S as starting materials, with a high photoluminescence quantum yield of 7.2 %. Polysulfide is formed first and is partially transformed into Na2S2O3 in the first step, and then turns back to elemental S in the second step. The elevated temperature and relatively oxygen‐deficient environment during the second step transforms Na2S2O3 into Na2SO3 incorporated with oxygen vacancies, thus resulting in the formation of a solid‐state powder consisting of elemental S embedded in Na2SO3. It shows aggregation‐induced emission properties, attributed to the influence of oxygen vacancies on the emission dynamics of sulfur by providing additional lower energy states that facilitate the radiative relaxation of excitons. 相似文献