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991.
D. Blanco Gomis A M Picinelli Lobo M. D. Gutiérrez Alvarez J. J. Mangas Alonso 《Chromatographia》1990,29(3-4):155-160
Summary A rapid and sensitive method for the simultaneous determination of primary amino acids in apple is described. After sample preparation, amino acids were derivatized with o-phthaldialdehyde/2-mercaptoethanol and separated on a reversed phase column with a gradient of phosphate buffer-tetrahydrofuran-methanol as the mobile phase. Detection was carried out with a fluorescence detector at excitation and emission wavelengths of 340 nm and 425 nm respectively. Recovery studies showed good results for all substances (91–109%) (with coefficients of variation ranging, from 0.1 to 9.0%). This method was applied to the monitoring of amino acids during the ripening of apples. 相似文献
992.
Summary Recently much attention has been directed to the validation of analytical methods. The level of validation will depend on the method application. If a method is developed for general use, for instance by different analysts, instruments or laboratories, then the effect of these changes need evaluation. This is normally referred to as ruggedness testing, where the limitations of the method to changes in the specified conditions are examined.This paper examines the use of Plackett-Burman fractional factorial experiment designs for ruggedness testing in high performance liquid chromatography (HPLC). The ability of these designs to identify confounding effects is applied to the stability indicating analysis of Salbutamol and its major degradation product, AH4045. The results show that confounding effects, proving extremely pertinent to HPLC, can be identified.The assay proved rugged to most tested changes although not to the use of column packing material from different manufacturers. 相似文献
993.
Mieczysław Jaroniec Jarosław Ościk Anna Deryło Ryszard Kusak Janusz Czarniecki 《Monatshefte für Chemie / Chemical Monthly》1982,113(1):29-35
An equation for multilayer adsorption from multicomponent liquid mixtures on solid surfaces1 has been examined. For this purpose experimental adsorption data for four alcohols from benzene/n-heptane mixture on silica gel have been measured. Average number of the adsorbed layers, heterogeneity parameter and capacity of the surface phase have been evaluated by using the equation mentioned above.
Mehrschichten-Adsorption von Alkoholen aus Benzol/n-Heptan-Mischung an Silica Gel
Zusammenfassung Eine Gleichung für Mehrschichten-Adsorption an festen Oberflächen1 aus Mehrkomponentenlösungen wurde getestet. Zu diesem Zweck wurden experimentelle Daten für die Adsorption von vier Alkoholen aus Benzol/n-Heptan-Mischung an Silica Gel herangezogen. Der Mittelwert für die Anzahl der Adsorptionsschichten, der Heterogenitätsparameter und die Kapazität der Oberflächenphase wurde aus dieser Gleichung berechnet.相似文献
994.
Steroids comprise a large group of natural substances that must frequently be monitored in various biological materials. Due to the metabolic versatility of steroid molecules, extremely complex mixtures are often encountered, necessitating the use of a chromatographic procedure prior to measurement. In this article we present our work, that is, the development of analyses of biological steroids (especially vitamin D compounds and neurosteroids) using gas chromatography/mass spectrometry, high-performance liquid chromatography (including inclusion chromatography using cyclodextrin) and liquid chromatography/mass spectrometry. 相似文献
995.
《Journal of separation science》2003,26(11):1028-1034
Reversed phase liquid chromatography with diode array detection (DAD) and electrospray mass spectrometric (ESI MSD) methods were developed for the identification of anthraquinone color components of cochineal, lac dye, and madder – red natural dyestuffs. Electrospray mass spectrometry was found to be more suitable than diode array detection for such analysis because of its higher sensitivity (detection limits in the range 30–90 ng mL–1) and selectivity. The developed method permitted unequivocal identification of carminic acid and laccaic acid A as coloring matters in examined preparations of cochineal and lac dye, respectively. In madder more chemical color species were found: alizarin, purpurin, lucidin, ruberythric acid, and also aluminum and calcium alizarin lake. Among the methods recommended so far, the present one allows fast, direct, and unequivocal identification of components of very complicated natural products used in art. 相似文献
996.
Summary A simple and sensitive method has been developed for the liquid chromatographic determination of short-chain aliphatic amines
in water. Analytes are retained in solid-phase extraction (SPE) cartridges, and then derivatized by drawing an aliquot of
the fluorogeneic reagent 9-fluorenylmethyl chloroformate (FMOC) through the cartridges. After a certain reaction time the
derivatives formed are desorbed with acetonitrile. The collected extracts are then chromatographed on a LiChrospher 100 RP18 125 mm×4 mm i.d., 5 μm, column using an acetonitrile-water gradient. The influence of experimental conditions (SPE material,
volume of sample, concentration of FMOC, time of reaction and pH) has been investigated. Optimal results have been obtained
with C18 SPE cartridges using a sample volume of 5.0 mL. For derivatization, 0.25 mL aliquots of 25 mM FMOC have been used, the reaction
time being only 2 min. The method has been applied to the quantification of several aliphatic amines: methylamine, ethylamine,
dimethylamine,n-butylamine,n-pentylamine andn-hexylamine. Under the proposed conditions the percentages of analytes retained plus derivatized were of about 54–107% compared
to those obtained with direct solution derivatization. The method provided good reproducibility, linearity and accuracy within
the 0.050–1.0 mg L−1 concentration range. The limits of detection were in the 0.25–5.0 μg L−1 range. The utility of the described approach has been tested by analysing tap water, river water and industrial waste water. 相似文献
997.
B. Kaufmann S. Souverain S. Cherkaoui P. Christen J. -L. Veuthey 《Chromatographia》2002,56(3-4):137-141
Summary A rapid analytical method has been developed for the mutual resolution of three steroidal compounds, withaferin A, iochromolide,
and withacnistin. Liquid chromatography was performed on a Chromolith analytical column (4.6 mm i.d.×50 mm), made from a cylindrical
silica rod, operated at a flow rate of 4 mL min−1 with a simple linear gradient prepared from 0.1% aqueous formic acid and 0.1% formic acid in acetonitrile. Under optimum
conditions simultaneous separation of the compounds was achieved in less than 7 min, one eighth the time required for conventional
LC separation. The overall analysis time was reduced without sacrificing chromatographic performance—essential for the resolution
of positional isomers such as iochromolide and withacnistin. The column was coupled to a single-quadrupole mass spectrometer
and the method was characterized by good performance in terms of repeatability, selectivity, linearity, and sensitivity. Detection
limits in the single-ion-monitoring mode were 0.15 μg mL−1 or below. Finally, the developed method was successfully applied to the determination of withanolides in extracts fromlochroma gesnerioides obtained by three different processes—traditional Soxhlet extraction and two faster methods, microwave-assisted extraction
and pressurized solvent extraction. 相似文献
998.
苯并菲盘状液晶的合成、亲氟效应及分子对称性对介晶性的影响 总被引:3,自引:0,他引:3
New symmetrical and asymmetrical triphenylene-containing discotic liquid crystals with two different peripheral alkyl chains, known as sym-TP(OC6H13)3(OR)3 and asym-TP(OC6H13)3(OR)3, were synthesized. Their thermotropic liquid crystal properties were investigated through polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The asyrranetdcal discogens are 2,6,11-rialkoxy-3,7,10-trihexyloxytriphenylenes, with the alkyl chain carbon numbers varying from 3-10, 12, and 14, while the symmetrical compounds are 2,6,10-trialkyloxy-3,7,11-trihexyloxytriphenylene. Two fluoroalkoxy substituted triphenylene discogens, 2,6,10-td(4,4,4-trifluorobutoxy)-3,7,11-trihexyloxytriphenylene and its asymmetrical isomer 2,6,11-tri(4,4,4-trifluorobutoxy)-3,7,10-trihexyloxytdphenylene were prepared. These two compounds show higher melting and clearing points than their alkoxy analogs, which implies that fluorophilic effect exists in the formation and stabilization of discotic columnar mesophase. The triphenylene derivatives TP(OC6H13)3(OR)3 with two different peripheral chains, symmetrically or asymmetrically attached on triphenylene cores, have lower melting points and clearing points than those of the higher symmetrical compounds TP(OR)6 with the same total chain carbon numbers. The mixed-chain-triphenylenes with longer alkoxy chains (n=9,10,12,14) show columnarmesophase at room temperature. 相似文献
999.
A sensitive and specific method was developed for the determination of sophoridine (SRI), sophocarpine (SC) and matrine (MT) in rabbit plasma by HPLC-MS. After an administration of Kuhuang by injection, blood samples were collected and extracted with methanol. The extract solutions were analysed by HPLC-MS method. The separation was performed on a ZORBAX Extend-C18 column using methanol/water/diethylamine (50:50:0.07, v/v/v) as mobile phase. The quinolizidine alkaloids were detected by using mass spectrometry in the SIM mode. There was a good linear relationship between peak area and concentration of analytes over the concentration range of 13.2–995.0 ng mL–1 for SRI, 7.0–530.0 ng mL–1 for SC and 8.8–655.0 ng mL–1 for MT, respectively. The absolute recovery of this method was more than 57% for SRI, 87% for SC and 91% for MT. The accuracy of assay was more than 90%. The limits of detection (LODs) were 6.8 ng mL–1 for SRI, 3.5 ng mL–1 for SC and 4.2 ng mL–1 for MT, respectively. The limits of quantitation (LOQs) were 13.2 ng mL–1 for SRI, 7.0 ng mL–1 for SC and 8.8 ng mL–1 for MT, respectively. The intra-day and inter-day coefficients of variation (RSDs) were less than 10.1, 6.3 and 5.8% for SRI, SC and MT, respectively. The developed method was applied to determine the concentration–time profiles of SRI, SC and MT in rabbit plasma after injection of Kuhuang. 相似文献
1000.
Magdalena Kurdziel Elżbieta Szczepaniec-Cieciak Monika Watorczyk Barbara Dabrowska 《Journal of solution chemistry》2004,33(5):453-464
The solubility of solid 2-methyl-1,3-butadiene (isoprene) in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K has been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in the solute. The experimental value of the mole fraction solubility of solid isoprene in liquid argon at 87.3 K is (1.41 ± 0.27) × 10–6 and (1.56 ± 0.36) × 10–7 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbon in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for isoprene than is liquid nitrogen. The experimental values of the solubilities of isoprene in liquid argon and nitrogen were compared with results obtained for selected unsaturated and aromatic hydrocarbons. 相似文献