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81.
B. W. Bailey J. M. Rankin R. Weinbloom 《International journal of environmental analytical chemistry》2013,93(1):3-9
The use of ternary complexes in the determination of anionic surfactants has been investigated and an analytical method using linear alkyl sulfonates as a test substance has been developed. The method involves the formation of the chloroform-extractable bisphenanthroline Cu(II)-linear alkyl sulfonate (LAS) complex and the subsequent equilibration of the extract with erythrosine to form the extractable bisphenanthroline Cu(II)-erythrosine complex. In the equilibration step erythrosine displaces LAS quantitatively, allowing the determination of the LAS originally present by measuring the absorbance of the extracted bisphenanthroline-Cu(II)-erythrosine complex. Results are reported of studies made to determine the optimum analytical conditions, the sensitivity, and the precision for the method described. 相似文献
82.
83.
Jishan Fan Fucai Li Gen Nakamura 《Mathematical Methods in the Applied Sciences》2015,38(11):2073-2080
We establish a new regularity criterion for the 2D full compressible magnetohydrodynamic system in a bounded domain. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
84.
We prove a logarithmic regularity criterion for the 3D generalized magnetohydrodynamics (MHD) system with diffusion terms ?Δu and (?Δ)βb, with . Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
85.
Jorge A. Vila Yelena A. Arnautova Osvaldo A. Martin Harold A. Scheraga 《Journal of computational chemistry》2014,35(4):309-312
The goal of this study is twofold. First, to investigate the relative influence of the main structural factors affecting the computation of the 13C′ shielding, namely, the conformation of the residue itself and the next nearest‐neighbor effects. Second, to determine whether calculation of the 13C′ shielding at the density functional level of theory (DFT), with an accuracy similar to that of the 13Cα shielding, is feasible with the existing computational resources. The DFT calculations, carried out for a large number of possible conformations of the tripeptide Ac‐G XY ‐NMe, with different combinations of X and Y residues, enable us to conclude that the accurate computation of the 13C′ shielding for a given residue X depends on the: (i) (?,ψ) backbone torsional angles of X ; (ii) side‐chain conformation of X ; (iii) (?,ψ) torsional angles of Y ; and (iv) identity of residue Y . Consequently, DFT‐based quantum mechanical calculations of the 13C′ shielding, with all these factors taken into account, are two orders of magnitude more CPU demanding than the computation, with similar accuracy, of the 13Cα shielding. Despite not considering the effect of the possible hydrogen bond interaction of the carbonyl oxygen, this work contributes to our general understanding of the main structural factors affecting the accurate computation of the 13C′ shielding in proteins and may spur significant progress in effort to develop new validation methods for protein structures. © 2013 Wiley Periodicals, Inc. 相似文献
86.
Eva Greibe Magnus Leth-Møller Sofie Stampe Per Ovesen Michael Pedersen Elke Hoffmann-Lücke 《Biomedical chromatography : BMC》2022,36(6):e5350
Artificial sweeteners are widely used as substitutes for sugar. The sweeteners are generally considered safe, however their whereabouts during pregnancy and lactation and the effect on child development are poorly explored. There is a need for new tools to measure these substances during pregnancy and lactation. Here, we describe the development and validation of a sensitive liquid chromatography–tandem mass spectrometry method for the simultaneous quantification of acesulfame, cyclamate, saccharin and sucralose in human plasma, umbilical cord blood, amniotic fluid and breast milk. The samples were prepared by protein precipitation and separated on a Luna Omega Polar C18 column (2.1 × 50 mm, 1.6 μm). Electrospray ionization in negative mode and multiple reaction monitoring were used to monitor the ion transitions. The validated concentration ranges were from 1 to 500 ng/ml (10–500 ng/ml for sucralose). Interassay precisions were all ≤15% and the accuracies were within ±15%. Stability, linearity, dilution integrity, carryover and recovery were also examined and satisfied the validation criteria. Finally, this analytical method was successfully applied on spiked samples of plasma, umbilical cord blood, amniotic fluid and breast milk, proving its suitability for use in clinical studies on artificial sweeteners, including during pregnancy and lactation. 相似文献
87.
This study developed a nanosensor for the detection and determination of favipiravir, a presumed drug that has potential therapeutic efficacy in treating COVID-19 patients, from tablets and serum samples. This nanosensor was obtained by adding the optimum amount of diamond nanoparticles into carbon paste. For the determination of favipiravir adsorptive stripping differential pulse (AdSDPV) and adsorptive stripping square wave voltammetry (AdSSWV) were used. Limit of detection values were found as 4.83×10−9 M and 2.44×10−7 M for bulk and 5.18×10−8 M and 4.38×10−8 M for serum samples using AdSDPV and AdSSWV, respectively. Recovery studies made of the tablet and serum produced satisfactory results. 相似文献
88.
《Arabian Journal of Chemistry》2022,15(11):104199
The harmful effects of pesticide residues are a threat to our health. Therefore, the current study aimed to validate a simple method for the determination of pesticide residues in commonly consumed fruits and vegetables from Al-Rass, Al-Qassim region, Saudi Arabia. A total of 1430 samples were collected from a local market and then analyzed for monitoring of 49 pesticide residues. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) multi-residue extraction method followed by gas chromatography equipped with triple-quadrupole mass spectrometry (GC–MS/MS) was successfully implemented. This 17-min-run analytical method detects and quantifies pesticide residues with acceptable validation performance parameters in terms of sensitivity, selectivity, linearity, the limit of quantification, accuracy, and precision. The linear range of the calibration curves ranged from 10 to 300 µg/L, all the pesticide LODs ranged from 0.0005 to 0.0024 mg/kg, and the pesticide LOQs ranged from 0.0011 to 0.0047 mg/kg. The recovery values at the three fortification levels ranged from 78 % to 107 %, and the precision values (expressed as RSD%) were less than 20 % for all of the investigated analytes. The results showed that 138 (9.65 %) of the analyzed samples were contaminated with pesticide residues, 40 (2.80 %) of the analyzed samples exceeded the maximum residue limit (MRL) of the European Commission regulations (EC) for pesticides residues, 98 (6.85 %) of the analyzed samples were contaminated with residues below the MRL, and 1292 (90.35 %) of the analyzed samples were pesticide residue-free. Coriander contained the highest percentage (46.88 %) of pesticide residues, particularly tetradifon that representing 18.75 % noncompliance with the MRL, followed by parsley, with 20.59 % pesticide residues (10.29 % non-compliance). Multiple pesticide residues were observed most frequently in tomatoes and dates which were contaminated with buprofezin and ethion respectively. 相似文献
89.
Nucleic acid–based electrochemical sensors are ideally suited to the detection of molecular targets for which enzymatic detection or direct electrochemical oxidation – reduction reactions are not possible. Moreover, the versatility of nucleic acids in their ability to bind a great variety of target types, from small molecules to single-entity mesoscopic targets, makes them attractive receptors for the development of electrochemical biosensors. In this brief opinion piece, we discuss field advances from the past two years. We hope the works highlighted here will inspire the community to pursue creative designs enabling the detection of larger and more complex targets with a specific focus on analytical validation and translation into preclinical or clinical applications. 相似文献
90.
Fbio Bernardo Providencia Gonzlez-Hernndez Nuno Ratola Vernica Pino Arminda Alves Vera Homem 《Molecules (Basel, Switzerland)》2021,26(11)
Volatile methylsiloxanes (VMSs) constitute a group of compounds used in a great variety of products, particularly personal care products. Due to their massive use, they are continually discharged into wastewater treatment plants and are increasingly being detected in wastewater and in the environment at low concentrations. The aim of this work was to develop and validate a fast and reliable methodology to screen seven VMSs in water samples, by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The influence of several factors affecting the extraction efficiency was investigated using a design of experiments approach. The main factors were selected (fiber type, sample volume, ionic strength, extraction and desorption time, extraction and desorption temperature) and optimized, employing a central composite design. The optimal conditions were: 65 µm PDMS/Divinylbenzene fiber, 10 mL sample, 19.5% NaCl, 39 min extraction time, 10 min desorption time, and 33 °C and 240 °C as extraction and desorption temperature, respectively. The methodology was successfully validated, showing low detection limits (up to 24 ng/L), good precision (relative standard deviations below 15%), and accuracy ranging from 62% to 104% in wastewater, tap, and river water samples. 相似文献