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181.
I. I. Chernobaev M. N. Yakubovich A. I. Tripol’skií N. V. Pavlenko V. L. Struzhko 《Theoretical and Experimental Chemistry》1997,33(1):38-40
Methane is formed in the Fischer-Tropsch synthesis under real conditions both through intermediates leading to chain propagation
and by hydrogenation of surface carbon.
L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, 252039 Kiev,
Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, No. 1, pp. 41–43, January–February, 1996. 相似文献
182.
A. Barański 《Chemistry of Heterocyclic Compounds》1985,21(2):153-156
A method was proposed for the synthesis of 3,5-diaryl-4-nitroisoxazoles entailing the brominatian of potassium salts of the corresponding 3,5-diaryl-2-isoxazolinyl-4-nitronic acids. The method may be used for the conversions of both the trans and cis isomers of 3,5-disubstituted 4-nitro-2-isoxazolines.Communication 9, See [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 189–192, February, 1985. 相似文献
183.
Frański R Schroeder G Rybachenko V Szwajka OP 《Rapid communications in mass spectrometry : RCM》2002,16(5):390-395
The fragmentation pattern of some protonated 2,5-diaryl-1,3,4-oxadiazoles is discussed. An unusual decomposition consisting of elimination of the isocyanic acid molecule from the internal oxadiazole ring was found. This fragmentation pathway was deduced on the basis of B/E linked scan mass spectra of metastable ions with liquid secondary ion mass spectrometry as the ionization method and also of low-energy CID mass spectra where electrospray was used as the ionization technique. High resolution measurements were also performed. 相似文献
184.
A. M. Kamiński 《Reaction Kinetics and Catalysis Letters》1992,48(1):309-313
Pyrolysis of propane in the presence of acetylene and acetylene labeled with C-14 has been studied in the temperature range of 833–1019 K. The inhibition effect of acetylene on the thermal decomposition of propane is turning into an accelerating effect at higher temperature.
C14 833–1019 . .相似文献
185.
A sensitive flotation—spectrophotometric method, based on the ion associate formed by the anionic thiocyanate complex of osmium with the basic dye methylene blue (MB) is described. The ion associate precipitates when the aqueous solution is shaken with toluene, and the separated and washed compound is dissolved in acetone. The molar absorptivity is 2.2 × 105 l mol-1 cm-1 at 655 nm. Beer's law is obeyed. The molar ratio of Os:SCN:MB in the separated and washed ion associate is 1:6:3. Ruthenium reacts similarly. The method is applied to the determination of traces of osmium in crucible platinum after separation of osmium by distillation as tetroxide. 相似文献
186.
R. Dybczyński 《Journal of Radioanalytical and Nuclear Chemistry》1980,60(1):45-54
Results of several IAEA intercomparison runs organized over the last 8 years are analyzed from the point of view of contribution and performance of NAA as compared to other techniques. It is shown that NAA is the method of good accuracy and precision providing on average greater share of results than any other single analytical technique. The prominent position of NAA among other methods used in trace analyses seems to be firmly established and there are no signs that there might be any change of the trend in the nearest future. 相似文献
187.
Mariola Koszytkowska-Stawińska 《Tetrahedron letters》2004,45(28):5437-5440
N-Pivaloyloxymethyl amides and sulfonamides, readily available from N-alkylation of both amides and sulfonamides with commercial chloromethyl pivaloate, were converted into acyclic azanucleosides via a one-pot base silylation/nucleoside coupling procedure. 相似文献
188.
Dzygiel A Rzeszotarska B Masiukiewicz E Cmoch P Kamieński B 《Chemical & pharmaceutical bulletin》2004,52(2):192-198
Methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate hydrochloride (1). and free ester (2). were obtained and 2 was reacted with Ac(2)O to give the acetylated products 3-6. Compounds 1-6 were studied using HPLC, GC-MS, FTIR and multinuclear NMR spectroscopy, including the cross-polarisation magic angle spinning (CPMAS) technique. The results of the acetylation of 2 were compared to those of the acetylation of 5-amino-1H-[1,2,4]triazole, and for 2 a significant decrease in the susceptibility to acetylation was found. The reaction of 2 with Ac(2)O at 20 degrees C, regardless of the amount and the concentration of the latter, including neat Ac(2)O, proceeds fully regioselectively and leads to one product: methyl 1-acetyl-5-amino-1H-[1,2,4]triazole-3-carboxylate (3). In sharp contrast to 5-amino-1H-[1,2,4]triazole, neither an additional monoacetylated isomer, whether annular or exocyclic, nor any diacetylated derivative could be detected. The diacetylation of 2 requires the process to be carried out in neat boiling Ac(2)O and, as in the case of 5-amino-1H-[1,2,4]triazole, gives two diacetylated isomers. These are methyl 1-acetyl-3-(acetylamino)-1H-[1,2,4]triazole-5-carboxylate (4) and 1-acetyl-5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (5). Hypothetical pathways of their formation have been suggested. A mixture of 4 and 5 upon hydrolysis of the ring acetyl group gives the monoacetylated derivative methyl 5-(acetylamino)-1H-[1,2,4]triazole-3-carboxylate (6). The spectroscopic, structural and conformational characteristics of compounds 1-6 have been given and methods for their preparation have been provided. 相似文献
189.
A symmetry-adapted perturbation theory based on Kohn-Sham determinants [SAPT(KS)] and utilizing asymptotically corrected exchange-correlation potentials has been applied to the He2, Ne2, (H2O)2, and (CO2)2 dimers. It is shown that SAPT(KS) is able to recover the electrostatic, first-order exchange, second-order induction, and exchange-induction energies with an accuracy approaching and occasionally surpassing that of regular SAPT at the currently programmed theory level. The use of the asymptotic corrections is critical to achieve this accuracy. The SAPT(KS) results can be obtained at a small fraction of the time needed for regular SAPT calculations. The robustness of the SAPT(KS) method with respect to the basis set size is also demonstrated. A theoretical justification for high accuracy of SAPT(KS) predictions for the electrostatic, first-order exchange, and second-order induction energies has been provided. 相似文献
190.
Maria?NowakowskaEmail author Krzysztof?Szczubia?ka Miros?aw?Gr?bosz 《Colloid and polymer science》2004,283(3):291-298
The interactions between copolymers of sodium styrene sulfonate (SSS) and N-isopropylacrylamide (NIPAM), anionic polyelectrolytes, and dodecyltrimethylammonium chloride (DTAC), a cationic surfactant, were studied in aqueous solutions of various ionic strengths. The copolymers were found to be thermoresponsive, showing a lower critical solution temperature (LCST). The influence of the polymer composition, the surfactant concentration, and the ionic strength on the LCST was studied. The surfactant was found to interact strongly with the polymer, forming mixed polymer-surfactant micelles. The critical aggregation concentration (cac) of the polymer-surfactant system was found from fluorescence spectroscopy using pyrene as a fluorescent probe. A strong dependence of the anionic polyelectrolyte-cationic surfactant interactions on the structure of the ionic comonomer was observed. 相似文献