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221.
Summary A statistical analytical procedure for calculating entropy (S) and Helmholtz free energy (F) from the order parameters
obtained from ESR spectra of spin-labelled membranes is described. The method is here applied to some literature data. A
brief discussion on the results is also reported.
Riassunto Si descrive un metodo statistico per calcolare l'entropia (S) e l'energia libera di Helmholtz (F) dai parametri d'ordine ottenuti da spettri ESR di membrane spin-marcate. Il metodo è applicato da alcuni dati di letteratura e sono brevemente discussi i risultati ottenuti.
Резюме Описывается статистическая аналитическая процедура вычисления энтропии (S) и свободной энергии Гельмгольца (F) из параметров порядка , полученных из ESR спектров для мембран со спиновыми метками. Развитый мэтод применяется к некоторым данным, имеюшимися в литературе. Проводится обсуждение полученных результатов.相似文献
222.
Summary A practical liquid chromatographic early-warning system for polar pollutants in water ought to have detection limits at a level below a microgram per litre. Using ultraviolet absorbance detection this normally necessitates trace enrichment of the samples. In this study ten different sorbents have been tested with respect to their enrichment capacity. The hydrophobic polymeric PLRP-S material, in combination with a C-18 modified analytical column, proved to be the best choice. The influence of humic substances, present in surface water, was also studied. Lowering of the sample pH, resulted in a significant increase in the interferences due to the humic substances. 相似文献
223.
Plasma produced by a (1064 nm) Nd:YAG laser focused onto a graphite target at different nitrogen pressures in the range of 1–90 mTorr, was studied spectroscopically. In the spectral range of 350–600 nm, emission lines of CI neutral carbon (501.12, and 505.21 nm), NI neutral nitrogen (493.5 nm), CII (426.72, 463.7, 515.11 nm), and CIII ions (465.02 and 569.59 nm), and NII ions (501.06, and 500.73 nm), were dominating. Bands of C2 Swan (d3Πg → a3Πu, Δ ν=2, 1, 0, −1), and CN Violet (B2Σ +→ X2Σ+, Δ ν=1, 0, −1) systems, and ionic emissions from the First Negative system N2+ (band head at 391.44 nm), were faintly observed under our specific experimental conditions. From the band intensities, vibrational temperature for CN and C2 was calculated to be 1.25 and 0.31 eV at 90 mTorr, respectively. The electron density and temperature, measured by Stark broadening, assuming a local thermodynamic equilibrium (LTE), were found to be 2.1× 1017 cm−3 and 0.33 eV at 1mTorr, respectively. The validity of the LTE is discussed according to the results discussed. Pressure dependence shows a decrease in the vibrational temperature when nitrogen pressure increases, while the electron density and temperature increase. 相似文献
224.
225.
Deferasirox is an orally active iron chelating agent, and during process development for deferasirox, we observed six related substances (impurities), namely deferasirox methyl ester, deferasirox salicylyl derivative, deferasirox ethyl ester, deferasirox methoxy carbonyl derivative, bis(salicyl)imide, and deferasirox-2-isomer. The present work describes the detection, origin, synthesis, and characterization of these related substances. 相似文献
226.
Daniela Iuliana Sora Elena Cristea Florin Albu Victor David Andrei Medvedovici 《Biomedical chromatography : BMC》2010,24(6):663-674
Analytical aspects related to the assay of pentoxifylline (PTX), lisofylline (M1) and carboxypropyl dimethylxanthine (M5) metabolites are discussed through comparison of two alternative analytical methods based on liquid chromatography separation and atmospheric pressure electrospray ionization tandem mass spectrometry detection. One method is based on a ‘pure’ reversed‐phase liquid chromatography mechanism, while the second one uses the additional polar interactions with embedded amide spacers linking octadecyl moieties to the silicagel surface (C‐18 Aqua stationary phase). In both cases, elution is isocratic. Both methods are equally selective and allows separation of unknowns (four species associated to PTX, two species associated to M1) detected through specific mass transitions of the parent compounds and owning respective structural confirmation. Plasma concentration–time patterns of these compounds follow typical metabolic profiles. It has been advanced that in‐vivo formation of conjugates of PTX and M1 is possible, such compounds being cleaved back to the parent ones within the ion source. The first method was associated with a sample preparation procedure based on plasma protein precipitation by strong organic acid addition. The second method used protein precipitation by addition of a water miscible organic solvent. Both analytical methods were fully validated and used to assess bioequivalence between a prolonged release generic formulation and the reference product, under multidose and single dose approaches. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
227.
Hydrolysis of some imidazole, benzimidazole, and 1,2,3-benzotriazole derivatives according to HPLC and NMR diffusimetry data 总被引:1,自引:0,他引:1
Hydrolysis of 1-mesylimidazole, 1-mesylbenzotriazole, and 1-tosylbenzimidazole was studied by reversed-phase HPLC and pulsed field gradient NMR diffusimetry. The hydrolysis rate constants and half reaction times were determined. The self-diffusion coefficients of the substances in aqueous solutions were measured. The reversed-phase HPLC data agree well with those of NMR diffusimetry. 相似文献
228.
This paper describes the validation of a method for the determination of 24 priority substances from the European Framework Directive in estuarine and sea water using the new extraction technique known as stir bar sorptive extraction (SBSE), followed by thermal desorption using capillary gas chromatography-mass spectrometry. We studied linearity, detection and quantitation limits and accuracy (which includes determination of trueness and precision). Using the lack-of-fit method we tested linearity in the 0-200 ng L−1 range for all the priority substances. The detection and quantification limits were less than 5 and 10 ng L−1, respectively, for most of the compounds studied. Precision was assessed by variance analysis (ANOVA) and relative standard values of less than 10% were obtained for repeatability and less than 15% for intermediate precision. The recovery percentages in spiked estuarine and sea water were close to 100%. Finally, for quality control of the method (stability of precision and accuracy through time), we developed a method for calculating Shewhart control charts based on the information obtained in the validation process. 相似文献
229.
A. Johansen H. Saleur D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):551-555
Significant advances, both in the theoretical understanding of rupture processes in heterogeneous media and in the methodology
for characterizing critical behavior, allows us to reanalyze the evidence for criticality and especially log-periodicity in
the previously reported chemical anomalies that preceded the Kobe earthquake. The ion (Cl-, K+, Mg++, NO3
- and SO4
-) concentrations of ground-water issued from deep wells located near the epicenter of the 1995 Kobe earthquake are taken as
proxies for the cumulative damage preceding the earthquake. Using both a parametric and non-parametric analysis, the five
data sets are compared extensively to synthetic time series. The null-hypothesis that the patterns documented on these times
series result from noise decorating a simple power law is rejected with a very high confidence level.
Received 21 January 2000 相似文献
230.