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991.
Flow injection (FI) methodology, using diffuse reflectance in the visible region of the spectrum, for the analysis of nickel, precipitated in the form of dimethylglyoximate, is presented. A reflectance cell, constructed in polytetrafluoroethylene, using a LED (light emitting diode) as light source and a LDR (light dependent resistor) as detector, is described. The analytical signal (S) correlates with nickel concentration (C) between 1.6 × 10−4 and 6.6 × 10−4 mol L−1. This correlation is described by the equation S = −1.108 + 3.314 × 104C − 2.081 × 107C2 (r = 0.9996). The experimentally observed limit of detection is about 1.3 × 10−4 mol L−1, as in lower concentrations the formation of precipitate is not observed. The experimental quantitation limit is about 1.6 × 10−4 mol L−1. The mean R.S.D. (relative standard deviation) is about 2.7%. Samples containing nickel were analyzed and the results obtained in this method were compared with those of other methods using the statistical Student's t-test. 相似文献
992.
A simple flow injection chemiluminescence (FI-CL) method was proposed for the determination of nitrofurazone. Strong CL signal was generated during the reaction of nitrofurazone with H2O2 and N-bromosuccinimide (NBS) in alkaline condition. The CL signal was proportional to the nitrofurazone concentration in the range 1.0 × 10−7 to 1.0 × 10−5 g mL−1. The detection limit was 2 × 10−8 g mL−1 nitrofurazone and the relative standard deviation was less than 4% (6.0 × 10−6 g mL−1 nitrofurazone, n = 11). The proposed method was successfully applied to the determination of nitrofurazone in compound furacillin nasal drops, human plasma and urine samples. The CL reaction mechanism was also discussed briefly. Singlet oxygen generated in the reaction between H2O2 and NBS was suggested to be participated in the CL reaction. 相似文献
993.
Hantash J Bartlett A Oldfield P Dénès G O'Rielly R David F 《Analytical and bioanalytical chemistry》2007,387(1):351-357
A flow-injection biosensor-like system based on a nonenzymatic approach has been developed to determine the carbamate pesticide
carbaryl in complex biological samples without lengthy and expensive extraction steps. Molecularly imprinted polymeric beads
were used to immobilize carbaryl from biological samples. pH variation permitted the elution of carbaryl from the binding
cavity to the flow cell. A pH electrode was used to detect changes in the charge of carbaryl in the sample solution resulting
from the protonation and deprotonation of the molecule over different pH ranges. At pH 2.0, the secondary amine group is protonated,
giving a (+1) charge to the carbaryl molecule. At pH 8.0, the ionized carbaryl loses a proton to become neutral, changing
the local pH of the flow cell. The pH change at the flow cell generated by the deprotonation of carbaryl ion in alkaline medium
was used to determine the carbaryl concentration. Parameters influencing the performance of the system were optimized for
use in the detection procedure. The validated biosensor-like system had a carbaryl detection limit of 10.0 μg/mL and a response
that was linear (r
2 > 0.98) over the concentration range of 10.0–00 μg/mL. 相似文献
994.
The literature about direct solid sample analysis of the past 10–15 years using electrothermal atomic absorption spectrometry
has been reviewed. It was found that in the vast majority of publications aqueous standards were reported as having been used
for calibration after careful program optimization. This means the frequently expressed claim that certified reference materials
with a matrix composition and analyte content close to that of the sample have to be used for calibration in solid sample
analysis is not confirmed in the more recent literature. There are obviously limitations, and there are examples in the literature
where even calibration with certified reference materials did not lead to accurate results. In these cases the problem is
typically associated with spectral interferences that cannot be corrected properly by the systems available for conventional
line source atomic absorption spectrometry, including Zeeman-effect background correction. Using high-resolution continuum
source atomic absorption spectrometry, spectral interferences become visible owing to the display of the spectral environment
at both sides of the analytical line at high resolution, which makes program optimization straightforward. Any spectrally
continuous background absorption is eliminated automatically, and even rapidly changing background absorption does not cause
any artifacts, as measurement and correction of background absorption are truly simultaneous. Any kind of fine-structured
background can be eliminated by “subtracting” reference spectra using a least-squares algorithm. Aqueous standards are used
for calibration in all published applications of high-resolution continuum source atomic absorption spectrometry to direct
solid sample analysis.
This contribution is based on a presentation given at the Colloquium for Analytical Atomic Spectroscopy (CANAS ‘07) held March
18–21, 2007 in Constance, Germany. 相似文献
995.
The direct electron transfer between hemoglobin (Hb) and an electrode was realized by first immobilizing the protein onto
SBA-15.The results of the immobilization showed that the adsorption was pH-dependent with a maximum adsorption near the isoelectric
point of the protein, and SBA-15 with a larger pore diameter showed greater adsorption capacity for Hb. UV–vis spectroscopy
and nitrogen adsorption analysis indicated that Hb was adsorbed within the channel of SBA-15 and no significant denaturation
occurred to the protein. The Hb/SBA-15 composite obtained was used for the fabrication of a Hb biosensor to detect hydrogen
peroxide. A pair of well-defined redox peaks at −0.337 and −0.370 V on the Hb/SBA-15 composite modified glassy carbon electrode
was observed, and the electrode reactions showed a surface-controlled process with a single proton transfer at a scan rate
range from 20 to 1,000 mV/s. The sensor showed a fast amperometric response, a low detection limit (2.3 × 10−9 M) and good stability for the detection of H2O2. The electrochemical results indicated that the immobilized Hb still retained its biological activity. 相似文献
996.
Solà Vázquez A Martín A Costa-Fernandez JM Ruiz Encinar J Bordel N Pereiro R Sanz-Medel A 《Analytical and bioanalytical chemistry》2007,389(3):683-690
There is an increasing concern regarding the toxicity and environmental distribution and impact of brominated organic compounds
employed as flame retardants. Thus, present interest in searching for new analytical techniques and methods allowing a rapid,
simple and reliable detection of those compounds in materials and wastes potentially containing such flame retardants is not
surprising. The feasibility of using radiofrequency glow discharge plasma spectrometry coupled with optical emission spectrometry
(rf-GD-OES) as a rapid and simple tool to directly analyse bromine-containing flame-retardant polymeric layers is investigated
here. Polymeric layers for calibration were made by mixing appropriate amounts of tetrabromobisphenol A, bisphenol A, phloroglucinol
and diphenylmethane-4,4′-diisocyanate in tetrahydrofuran. The corresponding blanks (polymers without tetrabromobisphenol A)
were also prepared. Detection of bromine was investigated both in the visible (at 470.48 nm) and in the near-infrared (at
827.24 nm) regions, using a charge-coupled device for detection. Discharge parameters affecting the emission intensity of
bromine were first optimized (in argon and helium as possible plasma gases) and the analytical performance characteristics
were then evaluated. The best detection limit (0.044% Br) was achieved measuring Br I 827.24 nm in a He discharge, using a
forward power of 70 W and a pressure of 45 Torr. The linearity range extended up to 27% Br. Finally, the applicability of
the rf-GD-OES method proposed to the quantitative analysis of bromine in solid materials coated with flame-retardant commercial
paints was successfully demonstrated.
Figure Flame Retardants 相似文献
997.
Alvarez-Romero GA Palomar-Pardavé ME Ramírez-Silva MT 《Analytical and bioanalytical chemistry》2007,387(4):1533-1541
The manufacture and evaluation of a novel sensor built with a composite material, highly selective to nitrate ions using doped
polypyrrole as a recognition agent, are presented. When the ratio of recognition agent to graphite was optimized at 1:1, and
the sensitivities found closely approached nernstian behavior. The stability times attained were less than 14 min with response
times also below 20 s. Batch characterization of the sensor displayed a sensitivity of 57.1 mV/decade of nitrate ion activity
() and a detection limit of 5.37 × 10−5 M, which are comparable to those reported for commercial sensors. Evaluation of the selectivity coefficients showed high
affinity to nitrate ion, superior to that of commercial sensors and others reported in the literature. The composite material
gives the sensor a prolonged service life with the added capability of allowing the regeneration of its active surface. Coupling
the sensor and a solid state, composite-type, reference electrode to a flow injection analysis system (FIA) permitted to achieve
an effective overall assessment of the system. A nitrate determination test was conducted on real samples. A comparison of
the results obtained, either with stationary measurements or with FIA, indicated that there were no significant differences
from the values from manufacturer’s specifications. 相似文献
998.
Helge Glöckner 《Journal of Functional Analysis》2007,245(1):19-61
Let G be a Lie group which is the union of an ascending sequence G1⊆G2⊆? of Lie groups (all of which may be infinite-dimensional). We study the question when in the category of Lie groups, topological groups, smooth manifolds, respectively, topological spaces. Full answers are obtained for G the group Diffc(M) of compactly supported C∞-diffeomorphisms of a σ-compact smooth manifold M; and for test function groups of compactly supported smooth maps with values in a finite-dimensional Lie group H. We also discuss the cases where G is a direct limit of unit groups of Banach algebras, a Lie group of germs of Lie group-valued analytic maps, or a weak direct product of Lie groups. 相似文献
999.
A flow injection sampling resonance light scattering system for total protein determination in human serum 总被引:1,自引:0,他引:1
Dong L Li Y Zhang Y Chen X Hu Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):1317-1322
A novel flow injection method with resonance light scattering detection was developed for the determination of total protein concentrations. This method is based on the enhancement of RLS signals from Methyl Blue (MB) by protein. The enhanced RLS intensities at 333 nm, in a pH 4.1 acidic aqueous solution, were proportional to the protein concentration over the range 2.0-37.3 and 1.0-36.0 microg ml-1 for human serum albumin (HSA) and bovine serum albumin (BSA), respectively. The corresponding limits of detection (3sigma) of 45 ng ml-1 for HSA and 80 ng ml-1 for BSA were attained. The method was successfully applied to the quantification of total proteins in human serum samples, the maximum relative error is less than 1% and the recovery is between 98% and 102%. The sample throughput was 60 h-1. 相似文献
1000.
The applicability of the headspace coupled to mass spectrometry for evaluation of the sensory quality of virgin olive oil samples is presented. The volatiles of the oil are directly transferred from the sample vial to the detector without chromatographic separation. The mass spectrum obtained can be considered as a fingerprint of the oil sample and can be used for classification purposes. After a training step with samples previously qualified following the official method, a classification model was created using the supervised technique soft independent modeling of class analogy (SIMCA). Eight negative (rancid, winey-vinegary, muddy sediment, hay-wood, vegetable water, earthy, fusty and musty-humidity) and three principal positive attributes (fruity, bitter and pungent) have been included in this study. With them, a classification model consisting of two main classes (extra- and lampante-virgin olive oil) was constructed. In addition, the unsupervised technique cluster analysis permited the discrimination among oils with different negative attributes. The proposed procedure has been applied to the classification of commercial samples (as extra- or lampante-virgin olive oils) and the results were compared with those provided by the expert's panel with acceptable correlation. 相似文献