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131.
Lolo M Pedreira S Vázquez BI Franco CM Cepeda A Fente CA 《Analytical and bioanalytical chemistry》2007,387(5):1933-1937
An efficiency extraction of fluoroquinolones in chicken muscle was achieved by pulverizing it in a freezer mill before treatment
with NaOH (10mM)/MeCN (1:1). The improvement of cryogenic grinding in the extraction was demonstrated for the same piece (whole
leg) of four chickens treated with enrofloxacin in equal doses. A confirmatory method based on high-performance liquid chromatography
tandem mass spectrometry (HPLC-MS/MS) was used to analyze the extracts. The chromatographic separation was achieved in 5min
with a Synergi Fusion-RP 80A (50 x 2mm, 4μm) column filled with a hybrid polymer. The HPLC was coupled with a detector based
in a quadrupole–linear ion trap Q-TRAP that allows a confirmatory detection according to the European legislation. The specificity
of the method was assessed by testing a number of representative blank muscle samples (n = 10) to verify the absence of potential interfering compounds. The limits of detection and quantitation were 2 and 5ng g-1 of quinolones in muscle samples, respectively. The chromatographic method was demonstrated to be linear for the range studied
(5–500ng g-1) with the P value for lack-of-fit in the ANOVA table greater or equal to 0.10 (calibration coefficient 0.9998 and 0.9996 for ciprofloxacin
and enrofloxacin, respectively). The mean intra-day relative standard deviation (RSD) (n = 6, c = 50ng g-1) was 6%; inter-day assay gave a RSD of 12%. The extraction and clean-up were carried out in one step with very satisfactory
recovery data (between 65 and 101%). 相似文献
132.
A simple, expeditious procedure for confirming the presence of N-nitrosamines in previously screened positive water samples was proposed. Water samples were continuously aspirated into a photometric flow system for screening. Positive samples were then confirmed and N-nitrosamines were identified by gas chromatography using different detectors (mass spectrometry, flame ionization and nitrogen-phosphorus). The system for the screening purpose was based on the preconcentration of the analytes onto a sorbent column, elution, and derivatization to form nitrite, then formation of a coloured product (Griess reaction) and photometric detection. The detection limits of the gas chromatographic method for 100 ml of sample were 2.0-3.5 microg/l, 20-80 and 3-13 ng/l for flame ionization, nitrogen-phosphorus and mass spectrometric detectors, respectively. The precision as RSD was similar for all detectors (3.0-6.5%). The screening of different types of water showed that wastewaters contain levels of N-nitrosamines that can be detected only using MS as a detector. 相似文献
133.
Neumann MG Schmitt CC Prieto KR Goi BE 《Journal of colloid and interface science》2007,315(2):810-813
A method based on the aggregate to monomol emission ratio, I(aggr)/I(monomol), was used to determine the minimal hydrotropic concentration (MHC) of aromatic hydrotropes. The main advantage of this method is that it does not require the use of probes or other additives, which might disrupt the aggregation process. Also, it relies on spectrophotometric measurements, which are more sensitive and less arduous than others, like conductivity, light scattering and surface tension. 相似文献
134.
135.
Fernández F Cordero B Durand J Muller G Malbosc F Kihn Y Teuma E Gómez M 《Dalton transactions (Cambridge, England : 2003)》2007,(47):5572-5581
A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system. 相似文献
136.
137.
Eleonor Harboure Oscar Salinas Beatriz Viviani 《Journal of Fourier Analysis and Applications》2007,13(3):267-284
As Fefferman and Stein showed, there is a tight connection between Carleson measures and BMO functions. In this work we extend
this type of results to the more general scope of the BMOϕ(ω) spaces. As a byproduct a weighted version of the Triebel-Lizorkin space
is introduced, which turns out to be isomorphic to BMO(ω) as in the unweighted case. 相似文献
138.
The synthesis of the retinoid skeleton has been exhaustively explored using the Stille coupling for the formation of the side-chain single bonds. On employing the experimental catalytic conditions developed by Farina [Pd2(dba)3, AsPh3, NMP] we have modified the electronic and steric requirement of the coupling parters, alkenyl stannanes and electrophiles (alkenyl iodides and triflates). The comprehensive survey afforded appropriately matched components for every bond formation considered. Moreover, from the comparison of the reactivities of different coupling partners with different degrees of steric hindrance, the sensitivity of the Stille coupling to steric effects was confirmed. Besides providing a variety of building blocks for retinoid synthesis, the study highlights some trends that might be useful for the application of the Stille reaction to the synthesis of unsubstituted conjugated polyenes. 相似文献
139.
M. Beatriz de la Calle-Guntiñas Frank Laturnus F. C. Adams 《Analytical and bioanalytical chemistry》1999,364(1-2):147-153
A method is described for the determination of dimethylselenide and dimethyldiselenide using a purge-and-trap/thermal desorption device (PT/TD) coupled to a capillary column gas chromatograph with a six-way Valco valve. The system is constructed in such a way that it allows also on-column injections of the volatile compounds in organic solvents for external calibration purposes without the need to disassemble the PT/TD. The influence of the purge flow, purge time and volume of sample, on the purge efficiency of the PT system is studied. Desorption time and temperature are optimised for the TD mode of operation. Atomic absorption spectrometry (AAS) and flame photometric detection (FPD) have been used for the final determination of the volatile compounds. The figures of merit achieved with both detectors are reported. 相似文献
140.
Isabel Bandrés Sandra Meler Beatriz Giner Pilar Cea Carlos Lafuente 《Journal of solution chemistry》2009,38(12):1622-1634
Aggregation of the ionic liquids 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium triflate, 1-butyl-2-methylpyridinium
tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium
dicyanamide, and 1-octyl-3-methylpyridinium tetrafluoroborate in aqueous solution has been characterized at 298.15 K through
density, ρ, speed of sound, u, and conductivity, σ, measurements. In addition, apparent molar volumes, V
φ
, and isentropic compressibilities, κ
s
, have been calculated from the experimental data. To characterize the formation of aggregates, the critical aggregation concentration
of the ionic liquids, cac, the degree of ionization of the aggregates, β, and the standard Gibbs energy of aggregation, DGm°\Delta G_{\mathrm{m}}^{\circ}, have been obtained, with good agreement between results derived from the different methods. The dependence on the structural
variation of these ions has been analyzed by comparing the results obtained for this series of ionic liquids. 相似文献