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81.
Caroline Antion 《Surface science》2007,601(10):2232-2244
Energetics and chemistry of liquid surfaces and liquid/liquid interfaces of binary A-B alloys are calculated using a subregular solution model. In this model, two macroscopic energetic parameters are used to produce an asymmetric miscibility gap. They are related to two microscopic parameters which describe the interaction energy between two atoms as a function of the composition of the first coordination shell of each atom. The impact of the asymmetry of the A-B interactions on the surface and interfacial energies and adsorption are analyzed by comparing the results obtained with this subregular model to those calculated for a regular solution. The role of the asymmetry on the prewetting and wetting transitions are also discussed. Calculations performed in the Co-Cu system are in good agreement with experimental data of surface energy. 相似文献
82.
Parworth CL Tucker MK Holmes BE Heard GL 《The journal of physical chemistry. A》2011,115(45):13133-13138
The 1,2-HX elimination reaction (where X = F, Cl, Br, OH) has been established as an important reaction in the degradation of compounds introduced into the upper atmosphere, including common CFC replacement compounds. By analyzing the electron densities of the transition state geometries of these reactions using QTAIM, we see that we can divide these reactions into two types. For HF and HOH elimination, the transition state is a complete ring of bonds, and neither the C-H nor the C-X bonds have been broken at the maximum of energy. There is very little accumulation of electron density on the X atom, with the majority of charge being lost by the hydrogen atom undergoing elimination, being transferred on to the two carbon atoms. In HCl and HBr elimination, a similar loss of electron density of the hydrogen atom is accompanied by significant accumulation of electron density on the X atom and a smaller change in electron density on the carbon atoms. The C-X bond is broken in the transition state geometry, with no ring critical point being present. This may explain the relative stabilities of halohydrocarbons and haloalcohols with respect to loss of H-X. 相似文献
83.
Caroline Bergh Ralf Torgrip Conny Östman 《Rapid communications in mass spectrometry : RCM》2010,24(19):2859-2867
A selective and sensitive method for the simultaneous determination of 14 organophosphate and six phthalate esters using gas chromatography (GC) and mass spectrometry (MS) is presented. Both of these compound classes are frequently found in the indoor environment due to their use as bulk additives in numerous polymers, consumer products and building materials. GC/MS utilizing positive ion chemical ionisation (PICI) in selected reaction monitoring (SRM) mode with isobutane as the reagent gas was found to be the best of the tested methods; it proved superior to electron ionisation (EI) in selected ion monitoring (SIM) mode and to PICI using methane as the reagent gas. The method was applied to indoor air samples collected by active air sampling using solid‐phase extraction (SPE) cartridges. Organophosphates and phthalates were simultaneously determined with method detection limits (MDLs) in the range of 0.1–47 ng m?3. For most compounds the MDLs were ≤0.2 ng m?3, but due to the presence of some of these ubiquitous indoor air pollutants in the blanks, significantly higher MDLs were observed for a few compounds. Finally, the method was also applied in the screening of a much more complex sample matrix, indoor dust. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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86.
Caged versions of the most common mitochondrial uncouplers (proton translocators) have been prepared that sense the reactive oxygen species (ROS) hydrogen peroxide to release the uncouplers 2,4-dinitrophenol (DNP) and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP) from caged states with second order rate constants of 10 (±0.8) M−1 s−1 and 64.8 (±0.6) M−1 s−1, respectively. The trigger mechanism involves conversion of an arylboronate into a phenol followed by fragmentation. Hydrogen peroxide-activated uncouplers may be useful for studying the biological process of ageing. 相似文献
87.
Elin S. Karlsson Caroline H. Johnson Sunil Sarda Lisa Iddon Mazhar Iqbal Xiaoli Meng John R. Harding Andrew V. Stachulski Jeremy K. Nicholson Ian D. Wilson John C. Lindon 《Rapid communications in mass spectrometry : RCM》2010,24(20):3043-3051
The use of high‐performance liquid chromatography/mass spectrometry (HPLC/MS) and proton nuclear magnetic resonance (1H NMR) spectroscopy for the kinetic analysis of acyl glucuronide (AG) isomerisation and hydrolysis of the 1‐β‐O‐acyl glucuronides (1‐β‐O‐AG) of phenylacetic acid, (R)‐ and (S)‐α‐methylphenylacetic acid and α,α‐dimethylphenylacetic acid is described and compared. Each AG was incubated in both aqueous buffer, at pH 7.4, and control human plasma at 37°C. Aliquots of these incubations, taken throughout the reaction time‐course, were analysed by HPLC/MS and 1H NMR spectroscopy. In buffer, transacylation reactions predominated, with relatively little hydrolysis to the free aglycone observed. In human plasma incubations the calculated rates of reaction were much faster than for buffer and, in contrast to the observations in buffer, hydrolysis to the free aglycone was a significant contributor to the overall reaction. A diagnostic analytical methodology based on differential mass spectrometric fragmentation of 1‐β‐O‐AGs compared to the 2‐, 3‐ and 4‐positional isomers, which enables selective determination of the former, was confirmed and applied. These findings show that HPLC/MS offers a viable alternative to the more commonly used NMR spectroscopic approach for the determination of the transacylation and hydrolysis reactions of these AGs, with the major advantage of having the capability to do so in a complex biological matrix such as plasma. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
88.
Jean-Philippe Basly Anséline Gradolatto Caroline Teyssier Naric Chantal Canivenc-Lavier 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):355-359
Summary. A selective
column switching high performance liquid chromatographic method has been used for the simultaneous determination of apigenin
and metabolites in rat liver perfusate. This new method clearly separated apigenin and the metabolites with high resolution.
The structures of metabolites were proposed based on selective ion recording and full scan analysis by electrospray ionization
mass spectrometry.
Corresponding author. E-mail: basly@pharma.unilim.fr
Received May 15, 2002; accepted (revised) September 13, 2002 相似文献
89.
This paper extends the results of Goh [1], and Takeuchi and Adachi [2,3] concerning the generalized linear Volterra model. We introduce a piecewise linear Volterra model for a two- species system. The solution of the steady-state problem is then shown to be equivalent to finding the solution to the Generalized Linear Complementarity Problem. We show when this nonnegative equilibrium is unique and globally asymptotically stable in the sense of Goh [1]. 相似文献
90.