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171.
D. Jacquemart H. Tran 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(4):569-579
Using absorption FT spectra (Bruker IFS 120, unapodized FWHM resolution ≈0.001 cm−1), about 1400 lines, between 880 and 1050 cm−1, and belonging to the ν6 band of both 12CH379Br and 12CH381Br isotopologues have been studied. Self- and N2-broadening coefficients are measured at various temperatures with an accuracy estimated to be around 10%. Their temperature-dependence exponents nself and nN2 have been derived with an accuracy estimated to be between 10% and 20%. A rotational dependence with the quantum number J has been observed for both nself and nN2, and has been empirically modeled using average values and polynomial expansions. 相似文献
172.
A copper-catalyzed synthesis of methyl esters from aromatic aldehydes in the presence of tert-butyl hydrogen peroxide (TBHP) was developed via a radical reaction mechanism. TBHP acts not only as an efficient oxidant, but also as a green methyl source in such transformation. Moreover, this method could also be efficiently extended to the methyl esterification of benzylic alcohols. 相似文献
173.
174.
Bakr F. Abdel-Wahab Salwa F. Mohamed Abd El-Galil E. Amr Mohamed M. Abdalla 《Monatshefte für Chemie / Chemical Monthly》2008,139(9):1083-1090
Methyl 2-(thiazol-2-ylcarbamoyl)acetate was synthesized and used as starting material. It was treated with hydrazine hydrate
to afford the hydrazide, which was reacted with nitromethane and formaldehyde to give the saturated nitropyrimidine. The hydrazide
was reacted with phenyl isothiocyanate to afford the thiosemicarbazide, which was cyclized with ethyl bromoacetate, sodium
hydroxide, or sulfuric acid to afford N-phenylthiazolidinone, N-phenyltriazole, and thiadiazolyl derivatives. The methyl 2-(thiazol-2-ylcarbamoyl)acetate was coupled with diazonium salts
of aniline, 4-chloroaniline, 4-bromoaniline, or 4-aminobenzenesulfonamide to afford the carbamoyl acetates, which were reacted
with 2-aminobenzimidazole, 1,2,4,5-tetrachlorophthalic anhydride, and hydrazine hydrate to afford the corresponding thiazolylmalonamide,
tetrachloroisoindolylimide, and tri-azole derivatives. Schiff bases and imides are newly synthesized candidates obtained via simple condensation of the hydrazide with aldehydes, 2,3-pyridinedicarboxylic anhydride, or 1,8-naphthalenedicarboxylic anhydride.
The pharmacological screening showed that many of these compounds have good antihypertensive α-blocking activity and low toxicity.
Correspondence: Abd El-Galil E. Amr, National Research Center, Applied Organic Chemistry, Dokki, Cairo, Egypt. 相似文献
175.
Lab-on-valve for the automatic determination of the total content and individual profiles of linear alkylbenzene sulfonates in water samples 总被引:1,自引:0,他引:1
Methods for the total content and individual determination of linear alkylbenzene sulfonates (LAS) in water samples based on the use of a lab-on-valve (LOV) module alone or coupled to CE equipment, respectively, have been developed. The total content of LAS has been determined by intrinsic absorption measurements (DA method) and after reaction with a methyl orange-cetylpyridine chloride mixture (MO method) with detection limits (LODs) of 21 ng/L and 15 microg/L, respectively, quantification limits (LOQs) of 70 ng/L, 50 microg/L, and development times of 100 and 124 s, respectively. The method for individual separation-quantification of LAS at very low concentration is based on automatic SPE preconcentration in the LOV module coupled on-line with the CE equipment. The LODs and LOQs thus obtained range between 1-21 and 4-70 ng/L, respectively, with linear dynamic ranges from the LOQ to 10 microg/L. Preconcentration factors of 10,000 and high efficiency to eliminate interferents by SPE enable application of the method to treated effluent, waste, surface and sea waters. 相似文献
176.
Three and four bond order couplings between carbonyl carbon and other neighboring protons have been investigated in detail with the help of 2D heteronuclear multiple bond correlation (HMBC) spectrum. The methine and methylene protons in pentad and tetrad configuration were found to couple with carbonyl carbon. The intensity ratio of methylene protons’ cross peaks in HMBC spectrum shows that 50% of poly methyl acrylate (PMA) is in isotactic and 50% is in syndiotactic configuration. The configurational analysis was mainly carried out with the help of 2D HMBC spectrum. 相似文献
177.
Imidazolium-based polymer supported gadolinium triflate as a heterogeneous recyclable Lewis acid catalyst for Michael additions 总被引:1,自引:0,他引:1
A heterogeneous Lewis acid catalytic system has been developed by incorporating gadolinium triflate on to poly[styrene-co-(1-((4-vinylphenyl)methyl)-3-methylimidazolium) tetrafluoroborate] (1-Gd(OTf)3), and the catalytic activity of this system has been examined for Michael additions of amines and thiols to α,β-unsaturated esters and acrylonitrile. The reactions proceed in moderate to excellent yields in the presence of catalytic system 1-Gd(OTf)3. The catalytic system could be efficiently recycled and reused. 相似文献
178.
179.
Zhipeng Xiang Wenjin Li Kai Wan Zhiyong Fu Zhenxing Liang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214601
Molecule aggregation in solution is acknowledged to be universal and can regulate the molecule's physiochemical properties, which however has been rarely investigated in electrochemistry. Herein, an electrochemical method is developed to quantitatively study the aggregation behavior of the target molecule methyl viologen dichloride. It is found that the oxidation state dicationic ions stay discrete, while the singly-reduced state monoradicals yield a concentration-dependent aggregation behavior. As a result, the molecule's energy level and its redox potential can be effectively regulated. This work does not only provide a method to investigate the molecular aggregation, but also demonstrates the feasibility to tune redox flow battery's performance by regulating the aggregation behavior. 相似文献
180.
Dr. Andreas Eitzinger Justus Reitz Patrick W. Antoni Prof. Dr. Herbert Mayr Dr. Armin R. Ofial Jun.-Prof. Max M. Hansmann 《Angewandte Chemie (International ed. in English)》2023,62(40):e202309790
A series of mesoionic, 1,2,3-triazole-derived N-heterocyclic olefins (mNHOs), which have an extraordinarily electron-rich exocyclic CC-double bond, was synthesized and spectroscopically characterized, in selected cases by X-ray crystallography. The kinetics of their reactions with arylidene malonates, ArCH=C(CO2Et)2, which gave zwitterionic adducts, were investigated photometrically in THF at 20 °C. The resulting second-order rate constants k2(20 °C) correlate linearly with the reported electrophilicity parameters E of the arylidene malonates (reference electrophiles), thus providing the nucleophile-specific N and sN parameters of the mNHOs according to the correlation lg k2(20 °C)=sN(N+E). With 21<N<32, the mNHOs are much stronger nucleophiles than conventional NHOs. Some mNHOs even excel the reactivity of mono- and diacceptor-substituted carbanions. It is exemplarily shown that the reactivity parameters thus obtained allow to calculate the rate constants for mNHO reactions with further Michael acceptors and predict the scope of reactions with other electrophilic reaction partners including carbon dioxide, which gives zwitterionic mNHO-carboxylates. The nucleophilicity parameters N correlate linearly with a linear combination of the quantum-chemically calculated methyl cation affinities and buried volumes of mNHOs, which offers a valuable tool to tailor the reactivities of strong carbon nucleophiles. 相似文献