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991.
Akbar Heydari Samad Khaksar Maryam Esfandyari Mahmoud Tajbakhsh 《Tetrahedron letters》2007,48(7):1135-1138
A simple and convenient procedure for direct reductive amination of aldehydes and ketones with sodium borohydride is described. The reaction has been carried out in methanol in the presence of a catalytic amount of H3PW12O40 (0.5 mol %). α,β-Unsaturated aldehydes and ketones can be easily converted into the corresponding allyl alcohols by reaction with H3PW12O40 (0.5 mol %)/NaBH4. 相似文献
992.
Akbar Heydari Roohollah Kazem Shiroodi Hossein Hamadi Maryam Esfandyari Mehrdad Pourayoubi 《Tetrahedron letters》2007,48(33):5865-5868
The commercially available heteropoly acid H3PW12O40 (0.5 mol %) is a very efficient and environmentally benign catalyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-tert-butyl dicarbonate at room temperature in short reaction times (<10 min). No competitive side products such as isocyanates, ureas, N,N-di-tert-butoxycarbonyls, O-Boc and oxazolidinones were observed. Chiral α-amino alcohols and esters afforded the corresponding N-Boc derivatives chemoselectively in excellent yields. 相似文献
993.
Issa Yavari Zinatossadat Hossaini Maryam Sabbaghan Majid Ghazanfarpour-Darjani 《Tetrahedron》2007,63(38):9423-9428
The reaction of ethyl propiolate with triphenylphosphine (Ph3P) in the presence of N-alkylisatins led to ethyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ5-oxaphosphole-4-carboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones in good yield. The reaction of dialkyl acetylenedicarboxylates with Ph3P in the presence of N-alkylisatins led to dialkyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ5-oxaphosphole-3,4-dicarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones and alkyl 4-(alkoxy)-5-oxo-2,5-dihydro-3-furancarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones. 相似文献
994.
Two new ZnII(μ‐4,4′‐bipy) coordination polymers with acetate anions, [Zn(4,4′‐bipy)(AcO)2] ( 1 ) and [Zn2(4,4′‐bipy)(AcO)4] ( 2 ), have been synthesized. The compounds were characterized with elemental analysis, IR‐, 1H NMR‐, 13C NMR spectroscopy and studied by thermal analysis, fluorescence measurements and x‐ray crystallography. The structural studies of compound 1 suggest the structure is a coordination polymer of zinc(II) consisting of linear double chains formed by bridging 4,4′‐bipy ligand and connection of the acetate‐bridged centrosymmetric [Zn2(OAc)2]2+ nodes. 相似文献
995.
996.
Second-order standard addition for deconvolution and quantification of fatty acids of fish oil using GC-MS 总被引:1,自引:0,他引:1
In the present work two second-order calibration methods, generalized rank annihilation method (GRAM) and multivariate curve resolution-alternating least square (MCR-ALS) have been applied on standard addition data matrices obtained by gas chromatography-mass spectrometry (GC-MS) to characterize and quantify four unsaturated fatty acids cis-9-hexadecenoic acid (C16:1ω7c), cis-9-octadecenoic acid (C18:1ω9c), cis-11-eicosenoic acid (C20:1ω9) and cis-13-docosenoic acid (C22:1ω9) in fish oil considering matrix interferences. With these methods, the area does not need to be directly measured and predictions are more accurate. Because of non-trilinear conditions of GC-MS data matrices, at first MCR-ALS and GRAM have been used on uncorrected data matrices. In comparison to MCR-ALS, biased and imprecise concentrations (%R.S.D. = 27.3) were obtained using GRAM without correcting the retention time-shift. As trilinearity is the essential requirement for implementing GRAM, the data need to be corrected. Multivariate rank alignment objectively corrects the run-to-run retention time variations between sample GC-MS data matrix and a standard addition GC-MS data matrix. Then, two second-order algorithms have been compared with each other. The above algorithms provided similar mean predictions, pure concentrations and spectral profiles. The results validated using standard mass spectra of target compounds. In addition, some of the quantification results were compared with the concentration values obtained using the selected mass chromatograms. As in the case of strong peak-overlap and the matrix effect, the classical univariate method of determination of the area of the peaks of the analytes will fail, the “second-order advantage” has solved this problem successfully. 相似文献
997.
Shayessteh Dadfarnia Ali Mohammad Haji Shabani Fatema Tamadon Maryam Rezaei 《Mikrochimica acta》2007,158(1-2):159-163
A simple and rapid flow injection system is proposed for indirect determination of cyanide by flame atomic absorption spectrometry.
It consists of a microcolumn of immobilized salen (N,N′-bis(salicylidene)ethylenediamine) on sodium dodecyl sulfate (SDS)-coated
alumina saturated with silver ion and a carrier of dilute solution of sodium hydroxide (10−5 mol L−1). The micro-column was located between the injection valve and nebulizer of atomic absorption spectrometry. Injection of
250 μL of aqueous cyanide standard or sample solution at pH range of 9–11 cause elution of silver as silver cyanide complexes,
which was then measured by flame atomic absorption spectrometry. The absorbance was proportional to the concentration of cyanide
in the sample. The graph of absorbance (as peak height) vs. cyanide concentration was linear over the concentration range
of 0.1–10 mg L−1 of cyanide, and the detection limit was 0.06 mg L−1. The relative standard deviation at 1 and 3 mg L−1 of cyanide concentration were 4.1 and 4.7%, respectively. The method was successfully applied to determination of cyanide
in water and industrial waste waters, and the accuracy was examined through independent analysis by accepted method of pyridine-barbituric
acid. 相似文献
998.
Minoo Dabiri Mostafa Baghbanzadeh Maryam S. Nikcheh 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1249-1252
Summary. Oxalic acid is used as an efficient catalyst in the condensation of 2-aminoaryl ketones with carbonyl compounds leading to
the formation of quinolines in excellent yields under solvent-free conditions. This methodology offers significant improvements
for the synthesis of quinolines with regard to the yield of products, simplicity in operation, inexpensive reagents, and green
aspects by avoiding toxic catalysts and solvents. 相似文献
999.
Gholam Hossein Rounaghi Massoumeh Mohajeri Shima Ashrafi Hoda Ghasemi Saman Sedaghat Maryam Tavakoli 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):1-6
Conductance measurements are reported for nickel(II), cupper(II), silver(I) and cadmium(II), salts in acetonitrile (AN)–dimethylformamide
(DMF) binary solvents containing macrocyclic ligand, 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBDA18C6) at different temperatures.
The changes in molar conductance caused by addition of DBDA18C6 to solutions were analyzed by non-linear least squares to
give stability constants of 1:1 metal cation–DBDA18C6 complexes. The results show that the stabilities of the complexes are
sensitive to solvent composition and in some cases the sequence of stabilities is changed with changing the composition of
the mixed solvents. The values of thermodynamic quantities (ΔH°c and ΔS°c) for formation of DBDA18C6-Ni2+, DBDA18C6-Cu2+, DBDA18C6-Ag+ and DBDA18C6-Cd2+ complexes were obtained from temperature dependence of the stability constants and the results show that the values of ΔH°c and ΔS°c for these complexes are sensitive to the nature and composition of AN–DMF binary solutions, but they do not vary monotonically
with the solvent composition. 相似文献
1000.
Maryam Mirza-Aghayan Rabah Boukherroub Max Koenig 《Journal of organometallic chemistry》2005,690(4):1028-1032
This paper describes the photochemical and the thermal isomerization of s-cis(E,E) 1,1-diphenly-3,4-bis(trimethylsilylmethylene)-1-silacyclopentane (1a). Under thermal conditions a 1,3-sigmatropic of the methylene hydrogen occurs, yielding the s-trans isomer (1b). The photochemical irradiation of (1a) at 300 nm for 1 h in deoxygenated benzene gives the corresponding s-cis(E,Z) isomer (1c) and then the s-cis(Z,Z) isomer (1d) after prolonged irradiation (3 h). There was no evidence for the formation of the corresponding cyclobutene resulting from the ring closure of the exocylic diene. 相似文献