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61.
Dudley E El-Sharkawi S Games DE Newton RP 《Rapid communications in mass spectrometry : RCM》2000,14(14):1200-1207
In order to optimise the analysis of urinary nucleosides by high performance liquid chromatography/mass spectrometry (HPLC/MS), the HPLC separation of these compounds was performed at different 'flow rates' and 0.2mL/min was found to give both a better separation and ionisation. The ionisation conditions were optimised to give the best intensity of the molecules quasi-molecular ions. The ion distribution profile and ionisation in both positive and negative mode were examined and the detection of the protonated molecule in positive mode chosen for further analysis. The limits of detection of the method developed are reported and representative LC/MS and LC/MS/MS spectra shown. Typical urinary nucleoside chromatograms are presented. 相似文献
62.
J. P. Stark 《Journal of statistical physics》1971,3(4):395-399
The classical canonical partition function for a one-dimensional, two-component system is examined for the case of nearest-neighbor interactions. The quasi-chemical model of solid solutions is found to be a natural consequence of the definition of the partition function when one replaces the normal configurational energy with a configurational free energy. Consequently, the quasi-chemical theory may be viewed as a consequence of the definition of the partition function and not as merely a physically pleasing model. 相似文献
63.
Structure-based drug discovery requires the iterative determination of protein-ligand costructures in order to improve the binding affinity and selectivity of potential drug candidates. In general, X-ray and NMR structure determination methods are time consuming and are typically the limiting factor in the drug discovery process. The application of molecular docking simulations to filter and evaluate drug candidates has become a common method to improve the throughput and efficiency of structure-based drug design. Unfortunately, molecular docking methods suffer from common problems that include ambiguous ligand conformers or failure to predict the correct docked structure. A rapid approach to determine accurate protein-ligand costructures is described based on NMR chemical shift perturbation (CSP) data routinely obtained using 2D 1H-15N HSQC spectra in high-throughput ligand affinity screens. The CSP data is used to both guide and filter AutoDock calculations using our AutoDockFilter program. This method is demonstrated for 19 distinct protein-ligand complexes where the docked conformers exhibited an average rmsd of 1.17 +/- 0.74 A relative to the original X-ray structures for the protein-ligand complexes. 相似文献
64.
R. Westwood Dudley H. Williams Adrian N. H. Yeo 《Journal of mass spectrometry : JMS》1970,3(12):1485-1488
The [NO2C7H6]+ ions generated from m-alkylnitrobenzenes have been shown to be different in their decomposition from those generated from p-alkylnitrobenzenes, even when the alkyl group is methyl and the departing fragment a hydrogen radical. Thus, in these cases even molecular ions of relatively high internal energy do not reversibly ring-expand to cycloheptatriene structures. In addition, the [NO2C7H6]+ ions, assumed to be benzylic, do not ring-expand to nitrotropylium ions at internal energies sufficient to cause subsequent loss of NO or NO2 from the p- and m-isomers, respectively. 相似文献
65.
[reaction: see text] A simple, efficient, and high-yielding synthesis of quinazolin-4-ylamine and thieno[3,2-d]pyrimidin-4-ylamine derivatives is reported under microwave irradiation conditions. Reaction conditions including temperature, solvent, and reaction time have been studied. An efficient parallel workup procedure was developed to generate a small library (23 compounds) in a short time period. 相似文献
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69.
D.G. Dudley 《Wave Motion》1983,5(4):369-384
Data into and out of a transient eletromagnetic system are considered in the framework of modern system identification. System solutions that take the form of a complex exponential series are discussed. Since the identification of the parameters in the series is non-linear, emphasis shifts to the identification of the parameters in the difference equation whose solution is the exponential series. The subject is cast in the formalism of system identification with generalizations to more complex systems. Two examples are given, one involving an actual electromagnetic experiment. 相似文献
70.
Triphilic Ionic‐Liquid Mixtures: Fluorinated and Non‐fluorinated Aprotic Ionic‐Liquid Mixtures 下载免费PDF全文
Dr. Oldamur Hollóczki Dr. Marina Macchiagodena Henry Weber Martin Thomas Dr. Martin Brehm Prof. Dr. Annegret Stark Dr. Olga Russina Dr. Alessandro Triolo Prof. Dr. Barbara Kirchner 《Chemphyschem》2015,16(15):3325-3333
We present here the possibility of forming triphilic mixtures from alkyl‐ and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domains—polar and nonpolar—three stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self‐associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long‐range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment. 相似文献