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251.
P. Parrilla P. Kaim E. A. Hogendoorn R. A. Baumann 《Analytical and bioanalytical chemistry》1999,363(1):77-82
In the development of a screening method for the determination of residues of mecoprop in soils involving coupled-column RPLC-UV (228 nm) the cleanup performance of a 5 μm GFF-II internal surface reversed phase (ISRP, Pinkerton) analytical column (50 × 4.6 mm I.D.) as a first column was investigated. In comparison to an analytical C18 column the ISRP column substantially improved the separation between acidic analyte and co-extracted humic substances. Under the selected coupled-column conditions soil extracts obtained after hydrolysis with an aqueous alkaline solution, acidifying and centrifugation could be analyzed directly allowing the determination of mecoprop in soils to a level of about 0.02 mg/kg. A rapid concentration step on a 100 mg C18 solid phase extraction (SPE) cartridge was adopted into the procedure providing a limit of detection (S/N = 3) of 0.01 mg/kg of mecoprop in soil. The method was validated by analyzing freshly spiked soil samples and samples with aged residues. In case of freshly spiked samples the overall recovery was 87% (n = 18, spiked level 0.02–8.0 mg/kg) with a repeatability of 6.8% and a reproducibility of 8.3%. No significant decrease of the recovery was observed for samples with aged residues (n = 15, spiked level 0.1 and 8.0 mg/kg) during a storage of 29 days in the refrigerator at about 4?°C; a storage of 67 days provided a mean recovery of 76% (n = 14, spiked level 8.0 mg/kg). 相似文献
252.
Sven Tombrink Saskia Müller Richard Heming Antje Michels Peter Lampen Joachim Franzke 《Analytical and bioanalytical chemistry》2010,397(7):2917-2922
In this study a simple micro-tube-based system for analysis of metal-containing liquids is introduced and its analytical performance
is evaluated. It is based on a miniaturised dielectric barrier discharge driven at atmospheric pressure. The emission lines
of various elements are observed. The system is developed for quantitative measurements and the limits of detection are determined.
Because of very low flow rates of just μL min−1 the approach requires extremely low sample volumes. 相似文献
253.
Dirk Pfefferkorn Sven Sonntag Samuel O. Kyeremateng Zofia Funke Hans‐Werner Kammer Jörg Kressler 《Journal of Polymer Science.Polymer Physics》2010,48(17):1893-1900
The pressure–volume–temperature behavior of miscible blends of poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) was studied over extended ranges of temperature and pressure. From pressure–volume–temperature data, the reduction parameters for the Flory‐Orwoll‐Vrij equation‐of‐state were determined. It was found that reduction parameters as well as density, thermal expansion coefficient, and isothermal compressibility vary with composition in a nonlinear manner. The surface tension of the blends in the molten state was measured over the whole composition range using the sessile drop method. The surface tension was found to display negative deviation from additivity pointing toward a remarkable surface excess of PMA. Moreover, surface tension displays a minimum in the range of low PEO content at weight fraction of ~0.19. In addition, the temperature coefficient of surface tension shows negative deviation from linearity. It stays constant when PMA is in excess. Results are discussed in terms of equation‐of‐state thermodynamics. The minimum of surface tension can be well explained by weak self‐association of PEO in the bulk. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1893–1900, 2010 相似文献
254.
Jens Langer Sven Krieck Reinald Fischer Helmar Görls Matthias Westerhausen Prof. Dr. 《无机化学与普通化学杂志》2010,636(7):1190-1198
Iodide is a very soft and large anion and as such its extreme ability to be polarized leads to a flat energy surface with respect to the variation of the Ca–I distances in [(L)nCaI2] and [(L)nCa(R)I]. The influence of the donor strength and the bulkiness of the neutral coligands L on the Ca–I distances is studied. The base adducts of calcium diiodide can be isolated after the addition of L to CaI2 or from the Schlenk equilibrium after the direct synthesis of calcium powder with aryl iodides. As L the ethers diethyl ether (Et2O), tetrahydrofuran (thf), tetrahydropyran (thp), 1,2‐dimethoxyethane (dme), 18‐crown‐6 (18C6), bis(methoxyethyl)ether (diglyme), and amines tetramethylethylenediamine (tmeda), and hexamethyltriethylenetetramine (hmteta) are studied yielding the adducts [(thp)4Ca(Ph)I] ( 1a ), [(thf)4Ca(Ph)I] ( 1b ), [(dme)2(thf)Ca(Ph)I] ( 1c ), [(18C6)Ca(Ph)I] ( 1d ), and [(tmeda)2Ca(Ph)I] ( 1e ), as well as [(thp)4CaI2] ( 2a ), [(thf)4CaI2] ( 2b ), [(Et2O)4CaI2] ( 2c ), [(diglyme)(thf)2CaI2] ( 2d ), [(diglyme)(dme)CaI2] ( 2e ), [(dme)2(thf)CaI2] ( 2f ), [(18C6)CaI2] ( 2g ), [(tmeda)2CaI2] ( 2h ), and [(hmteta)CaI2] ( 2i ). For comparison reasons, [(thf)4Ca(Ph)Br] ( 3a ), [(thp)4CaBr2] ( 4a ), [(thf)4CaBr2] ( 4b ), and [(dme)2(AcOH)CaBr2] ( 4c ) with AcOH being acetic acid are included as well. The comparison shows that the coordination number of calcium itself only plays an insignificant role whereas bulkiness and donor strength of L represent the key influences. 相似文献
255.
256.
L. v. Udránszky und E. Baumann 《Fresenius' Journal of Analytical Chemistry》1890,29(1):238-239
Ohne Zusammenfassung 相似文献
257.
258.
259.
Nga H. Nguyen Brad M. Rosen Xuan Jiang Sven Fleischmann Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5577-5590
SET‐LRP is mediated by a combination of solvent and ligand that promotes disproportionation of Cu(I)X into Cu(0) and Cu(II)X2. Therefore, the diversity of solvents suitable for SET‐LRP is limited. SET‐LRP of MA in a library of solvents with different equilibrium constants for disproportionation of Cu(I)X such as DMSO, DMF, DMAC, EC, PC, EtOH, MeOH, methoxyethanol, NMP, acetone and in their binary mixtures with H2O was examined. H2O exhibits the highest equilibrium constant for disproportionation of Cu(I)X. The apparent rate constant of the polymerization exhibits a linear increase with the addition of H2O. This is consistent with higher equilibrium constants for disproportionation generated by addition of H2O to organic solvents. Furthermore, with the exception of alcohols and carbonates, the rate constant of polymerization in binary mixtures could be correlated with the Dimroth‐Reichardt solvent polarity parameter. This is consistent with the single‐electron transfer mechanism proposed for SET‐LRP that involves a polar transition state. These experiments demonstrate that the use of binary mixtures of solvents with H2O provides a new, simple and efficient method for the elaboration of a large diversity of reaction media that are suitable for SET‐LRP even when one of the two solvents does not mediate disproportionation of Cu(I)X. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5577–5590, 2009 相似文献
260.
A sonic spray ionization (SSI) interface for liquid chromatography-mass spectrometry (LC-MS) analysis was optimized for analysis of 2-[(1R)-3-[bis(1-methylethyl)amino]-1-phenylpropyl]-4-methyl-phenol (tolterodine), used as a model drug substance, and the influence of different parameter settings was evaluated using factorial design. A comparison between SSI and electrospray ionization (ESI) was made for tolterodine, tolterodine metabolites, and a set of steroids.SSI was found to give slightly poorer repeatability and broader peaks for tolterodine compared to ESI. However, there was no significant difference in chromatographic peak shape, and the repeatability using SSI was similar to that obtained using ESI if a ratio (area of tolterodine/area of metabolite) was used. In this study, the sensitivity was higher using SSI. For the analysis of pregnanolone, less water loss was obtained using SSI, probably due to less energy being transferred to the analyte upon ionization. 相似文献