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131.
Susana Sadler Simões Antonio Castañera Ajenjo Mário João Dias 《Rapid communications in mass spectrometry : RCM》2011,25(18):2603-2610
A qualitative and quantitative analytical method was developed for the simultaneous determination of Δ9‐tetrahydrocannabinol (THC), 11‐hydroxy‐Δ9‐tetrahydrocannabinol (11‐OH‐THC) and l1‐nor‐9‐carboxy‐Δ9‐tetrahydrocannabinol (THC‐COOH) in whole blood. The samples were prepared by solid‐phase extraction followed by ultra‐performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) analysis using positive ion electrospray ionization and multiple reaction monitoring. The chromatographic separation was performed with an Acquity UPLC® HSS T3 (50 × 2.1 mm i.d., 1.8 µm) reversed‐phase column using a methanol/2 mM ammonium formate (formic acid 0.1%) gradient in a total run time of 9.5 min. MS/MS detection was achieved with two precursor‐product ion transitions per substance. The method was fully validated, including selectivity and capacity of identification, according to the identification criteria (two transitions per substance, signal‐to‐noise ratio, relative retention time and ion ratio) without the presence of interferences, limit of detection (0.2 µg/L for THC and 0.5 µg/L for 11‐OH‐THC and THC‐COOH), limit of quantitation (0.5 µg/L for all cannabinoids), recovery (53–115%), carryover, matrix effect (34‐43%), linearity (0.5‐100 µg/L), intra‐assay precision (CV < 10% for the relative peak area ratios and <0.1% for the relative retention time), inter‐assay accuracy (mean relative error <10%) and precision (CV <11%). The method has already been successfully used in proficiency tests and subsequently applied to authentic samples in routine forensic analysis. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
132.
Judith Mawer Sean F. Johnston Mariachiara Di Matteo Catarina Madruga Ana Simões Josep Simon 《Ambix》2015,62(3):292-303
133.
Raquel M. C. Gonçalves Ana M. N. Simões Joaquim J. Moura-Ramos 《Journal of solution chemistry》1993,22(6):507-517
In the present work the solution process of globular solutes (xenon, cyclohexane, cyclooctane and adamantane) in n-alkane solvents is analyzed. New experimental data on solution enthalpies of adamantane in those solvents are presented. The cavity model previously proposed is corrected with respect to the dependence of the surface tension on the curvature radius of the microscopic cavity and a new equation is proposed to describe this dependence. 相似文献
134.
Anu Teearu Signe Vahur Uku Haljasorg Ivo Leito Tõiv Haljasorg Lauri Toom 《Journal of mass spectrometry : JMS》2014,49(10):970-979
2,5‐Dihydroxybenzoic acid (DHB) is one of the most widely used and studied matrix compounds in matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. However, the influence of ageing of the DHB solution on the MALDI mass spectra has not been yet systematically studied. In this work, the possible changes occurring in the acidified acetonitrile/water solution of the MALDI matrix compound DHB during 1‐year usage period have been monitored with MALDI‐Fourier transform ion cyclotron resonance mass spectrometer (MALDI‐FT‐ICR‐MS) and attenuated total reflectance Fourier transform infrared (ATR‐FT‐IR) spectroscopy. No significant ageing products have been detected. The ability of the aged DHB solution to act as a MALDI matrix was tested with two materials widely used in art and conservation – bone glue (a proteinaceous material) and shellac resin (a resinous material) – and good results were obtained. A number of peaks in the mass spectra measured from the DHB solution were identified, which can be used for internal calibration of the mass axis. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
135.
136.
Aav R Pehk T Tamp S Tamm T Kudrjašova M Parve O Lopp M 《Magnetic resonance in chemistry : MRC》2011,49(2):76-82
Spin-spin coupling constants between nuclei in NMR spectroscopy reflect their spatial arrangement. A number of calculation methods, applying different levels of theory, have been developed to support the stereochemical assignment of novel compounds. Nevertheless, revisions of the assignment of structures in the literature are not rare. In the present work, the reliability of the calculation methods amenable for a theoretical prediction of spin-spin coupling constants of vicinal protons to support correct stereochemical assignment of substitution at five-membered rings of 3-alkoxy-6,7-epoxy-2-oxabicyclo[3.3.0]octanes was studied. Experimental (3)J(H,H) coupling constants were compared with the coupling constants calculated for all possible diastereomers. The fully quantum chemical approach provided theoretical (3)J(H,H) coupling constants with an absolute deviation of no more than 1.1 Hz for 91% of the experimentally studied coupled spins, whereas the methods without quantum chemical geometry optimization resulted in completely unreliable predictions. Consequently, for a reliable stereochemical assignment of small and medium size molecules, the protocol for calculating the coupling constants based on the results of the quantum chemical geometry optimization is recommended. 相似文献
137.
Manuel Cordova Pinelopi Moutzouri Bruno Simões de Almeida Daria Torodii Prof. Lyndon Emsley 《Angewandte Chemie (International ed. in English)》2023,62(8):e202216607
The resolution of proton solid-state NMR spectra is usually limited by broadening arising from dipolar interactions between spins. Magic-angle spinning alleviates this broadening by inducing coherent averaging. However, even the highest spinning rates experimentally accessible today are not able to completely remove dipolar interactions. Here, we introduce a deep learning approach to determine pure isotropic proton spectra from a two-dimensional set of magic-angle spinning spectra acquired at different spinning rates. Applying the model to 8 organic solids yields high-resolution 1H solid-state NMR spectra with isotropic linewidths in the 50–400 Hz range. 相似文献
138.
Ana Paula Barrêto Gomes Lidiane Pinto Correia Mônica Oliveira da Silva Simões R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,88(2):383-387
The objective of this work was to develop
and validate a fast and reproducible method to determine the concentration
of metronidazole in drug substance and tablets. The samples were analyzed
by dynamic thermogravimetry, using 10, 20, 40, 60 and 80°C min–1
heating rates in nitrogen and in nitrogen with synthetic air. Obtained data
were used in the Antoine and Langmuir equations in order to have the pressure
curves. Vapor pressure curves of drug and tablet of metronidazole were evaluated
using the mathematical indexes of difference factor, f
1,
and similarity factor, f
2,
to compare their profiles. The data showed that there is no significant difference
between the vapor pressure profiles of drug and tablet of metronidazole in
both environmental conditions, which confirms that the process is really vaporization.
The concentration of metronidazole was determined in the raw material and
tablets of the drug. 相似文献
139.
140.
Thermal decomposition study of HAuCl4·3H2O and AgNO3 as precursors for plasmonic metal nanoparticles
K. Otto I. Oja Acik M. Krunks K. Tõnsuaadu A. Mere 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1065-1072
Thermal decomposition of HAuCl4·3H2O and AgNO3, as precursors for Au and Ag nanoparticles, respectively, was monitored by coupled TG–DTA with TG/EGA–FTIR and EGA–MS techniques in a flowing 80 %Ar + 20 %O2 and Ar atmospheres in the temperature range of 30–600 °C. The intermediate and final products of thermal decomposition were analysed by ex situ XRD and FTIR techniques. The thermal degradation of HAuCl4·3H2O starts immediately after melting at 75 °C and takes place in three steps in the temperature range of 75–320 °C with total mass loss of 49.4 and 49.7 % in artificial air and Ar atmospheres, respectively. EGA by MS and FTIR revealed a simultaneous release of H2O and HCl in the temperature range of 75–235 °C. EGA by MS revealed a release of Cl2 at around 225 °C and in the interval of 250–320 °C. According to the XRD analysis, the main solid product in the end of the first decomposition step at 190 °C is AuCl3; in the end of the second decomposition step at 240 °C is AuCl and the final product at 320 °C is Au. The thermal decomposition of AgNO3 takes place in a single step in the temperature range of 360–515 °C with a total mass loss of 39.0 and 37.8 % in flowing artificial air and Ar atmospheres, respectively. According to EGA–MS and EGA–FTIR the main evolved gases are NO2, NO and O2. The final product of the thermal decomposition at 600 °C is Ag irrespective of the atmosphere. 相似文献