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71.
The configuration interaction (CI ) method where the efficiency of the generators of the unitary group is most fully exploited is the internally contracted multireference CI method. In the most recent version of this method the semi-internal configurations were kept uncontracted, which means that the number of configurations can still be quite large. In the present study the necessary formulas are derived for the case where the semi-internal states are also contracted. The highest density matrix that appears in these formulas is of order 5, and the computational treatment of this large matrix is discussed in detail. 相似文献
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al-Khalili A Thomas R Ehlerding A Hellberg F Geppert WD Zhaunerchyk V af Ugglas M Larsson M Uggerud E Vedde J Adlhart C Semaniak J Kamińska M Zubarev RA Kjeldsen F Andersson PU Osterdahl F Bednarska VA Paál A 《The Journal of chemical physics》2004,121(12):5700-5708
Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD. 相似文献
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Arylation of 1-(methoxycarbonyl)-2,5-dihydropyrrole under standard Heck reaction conditions produces a mixture of compounds. The olefin undergoes two types of palladium-catalyzed reactions: (a) arylation to provide C-3 arylated derivatives and (b) competing double bond isomerization. Addition of silver carbonate and thallium acetate fully suppressed the isomerization, and good yields of C-3 substituted compounds were achieved after arylation with aryl halides. With regard to aryl triflates as arylating agents, addition of lithium chloride was necessary to promote the Heck reaction. This additive excluded the use of silver and thallium salts, but high regioselectivity and good yields could be obtained by employing tri-2-furylphosphine as ligand. Arylation was rendered both regioselective and enantioselective (58% ee) with 1-naphthyl triflate as substrate utilizing a (R)-BINAP/thallium acetate combination. The C-3 arylated enamides were converted further into the corresponding 3-arylpyrrolidines. 相似文献
77.
Xiaolin Hou K. G. Andersson J. Roed A. Byskov T. Roed 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):133-143
Hairless rats, clothes, human hair, filter paper and water were exposed to gaseous elemental iodine in a glass chamber for
60–120 minutes. The deposition of gaseous elemental iodine on skin and lung of rats, human hair, water, clothes and paper
were investigated by measuring iodine content in the exposed material by epithermal neutron activation analysis (ENAA). For
measurement of the iodine concentration in the chamber air, elemental iodine in the air was collected by continuously sucking
air through an active charcoal column. The trapped iodine in the active charcoal was then determined by ENAA. The measured
deposition velocity in the test chamber of gaseous elemental iodine on skin, clothing, hair and water ranges from 0.006 on
filter paper and water to about 0.05 cm/s on skin and clothes. The variation of elemental iodine concentration in air of the
glass chamber was investigated by collecting and analyzing air samples at various time intervals. The results show that the
variation with time in the concentration of the iodine can be described by an exponential function. 相似文献
78.
Asakawa T Ishino S Hansson P Almgren M Ohta A Miyagishi S 《Langmuir : the ACS journal of surfaces and colloids》2004,20(17):6998-7003
A halide-sensitive fluorescence probe was utilized to evaluate the miscibility of fluorocarbon and hydrocarbon surfactants in aqueous micellar systems. The fluorescence of 6-methoxy-N-1,1,2,2-tetrahydroheptadecafluorodecylquinolinium chloride, FC10MQ, was quenched by halide ions dissociated from the surfactant. The fluorescence in micellar solutions showed an initially rapid decay. This suggests that halide ions effectively quench FC10MQ fluorescence at the micellar surface. The subsequent slow decay corresponds to the quenching of FC10MQ fluorescence in the aqueous bulk phase by the free counterions. The Stern-Volmer plots for fluorescence quenching gave a distinct break at the critical micelle concentration of the cationic surfactants. The abrupt increase in fluorescence quenching is attributed to the solubilization of the probe in the micelles. The fluorescence quenching behavior provides direct information about the immiscibility of fluorocarbon and hydrocarbon species in micelles, and the results indicate that almost pure fluorocarbon micelles appear in surfactants mixtures. 相似文献
79.
Metabolic profiling of new synthetic cannabinoids AMB and 5F‐AMB by human hepatocyte and liver microsome incubations and high‐resolution mass spectrometry 下载免费PDF全文
80.