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991.
Jean-Claude Alvarez Isabelle Etting Islam Amine Larabi 《Biomedical chromatography : BMC》2022,36(8):e5391
An LC-MS/MS method for hair testing of glyphosate and aminomethylphosphonic acid (AMPA), its main biodegradation product, has been developed. After decontamination, 50 mg of hair was ground and sonicated in water for 2 h. The method was fully validated in the 5–500 pg/mg range for glyphosate and 10–500 pg/mg for AMPA, and the limits of detection were 2 and 5 pg/mg, respectively. Matrix effect for glyphosate and AMPA was compensated by an isotope-labeled internal standard. Hair samples from four farmers who regularly used glyphosate and one farmer who used glyphosate but not his wife and 14 hair samples from nonoccupationally exposed subjects were tested. Glyphosate was found in head hair of three farmers, with concentration in the range 14–188 pg/mg. The fourth was found negative but with hair colored in red. Glyphosate was detected in 10 of 14 hair samples from nonoccupationally exposed subjects at concentrations of 11.5 pg/mg or lower and only in one segment (0–3 cm) of the farmer's spouse (6 pg/mg). AMPA was detected in five subjects, above the limit of quantification only in two of three occupationally exposed subjects with positive glyphosate. Further studies should be conducted to validate this potential new biomarker that could be useful for assessing long-term exposure to glyphosate. 相似文献
992.
993.
Shirar AJ Wilcox DS Hotopp KM Storck GL Kleiner I Dian BC 《The journal of physical chemistry. A》2010,114(46):12187-12194
The ground state spectrum of m-methylbenzaldehyde (m-MBA) was measured with a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. The methyl rotor on m-MBA introduces an internal rotation barrier, which leads to splitting of the torsional energy level degeneracy into A and E states. Ab initio calculations predict a low torsional barrier for both the O-cis and O-trans conformers, resulting in a large doublet splitting up to several gigahertz in the frequency spectrum. The rotational constants, distortion terms, and V(3) values for both species have been determined from the ground state rotational spectrum using the BELGI-C(s) fitting program. There are significant differences in the torsional potential for the O-cis and O-trans m-MBA conformers. Molecular orbitals and resonance structures for each conformer are analyzed to understand the difference in torsional barrier height as well as the irregular shape of the O-trans torsional potential. 相似文献
994.
Petkov JT Tucker IM Penfold J Thomas RK Petsev DN Dong CC Golding S Grillo I 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):16699-16709
The impact of multivalent counterions, Al(3+), on the surface adsorption and self-assembly of the anionic surfactant sodium dodecyl dioxyethylene sulfate, SLES, and the anionic/nonionic surfactant mixtures of SLES and monododecyl dodecaethylene glycol, C(12)E(12), has been investigated using neutron reflectivity, NR, and small angle neutron scattering, SANS. The addition of relatively low concentrations of Al(3+) counterions induces a transition from a monolayer to well-defined surface bilayer, trilayer, and multilayer structures in the adsorption of SLES at the air-water interface. The addition of the nonionic cosurfactant, C(12)E(12), partially inhibits the evolution in the surface structure from monolayer to multilayer interfacial structures. This surface phase behavior is strongly dependent upon the surfactant concentration, solution composition, and concentration of Al(3+) counterions. In solution, the addition of relatively low concentrations of Al(3+) ions promotes significant micellar growth in SLES and SLES/C(12)E(12) mixtures. At the higher counterion concentrations, there is a transition to lamellar structures and ultimately precipitation. The presence of the C(12)E(12) nonionic cosurfactant partially suppresses the aggregate growth. The surface and solution behaviors can be explained in terms of the strong binding of the Al(3+) ions to the SLES headgroup to form surfactant-ion complexes (trimers). These results provide direct evidence of the role of the nonionic cosurfactant in manipulating both the surface and solution behavior. The larger EO(12) headgroup of the C(12)E(12) provides a steric hindrance which disrupts and ultimately prevents the formation of the surfactant-ion complexes. The results provide an important insight into how multivalent counterions can be used to manipulate both solution self-assembly and surface properties. 相似文献
995.
Dr. Ting Wu Dr. Isabelle Leray Dr. Valérie Génot Jean Pierre Lefèvre Alexandre Korovitch Dr. Nguyêt‐Thanh Ha‐Duong Dr. Jean‐Michel El Hage Chahine Prof. Jacques Alexis Delaire 《Chemphyschem》2010,11(15):3355-3362
The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix‐DANS4 are determined to optimize the geometry of the microreactor used for the flow‐injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix‐DANS4) the 1:1 Pb2+‐Calix‐DANS4 complex is predominantly formed with a high stability constant (log K1:1=6.82) and a slow second‐order rate constant (k=9.4×104 L mol?1 s?1). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h?1 to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors. 相似文献
996.
Diego Bohoyo Isabelle Le Potier Céline Rivière Hans Klafki Jens Wiltfang Myriam Taverna 《Journal of separation science》2010,33(8):1090-1098
We evaluated the potential of CE to analyse different isoforms of unphosphorylated recombinant tau protein and for separating one phosphorylated tau from the respective unphosphorylated protein. Different capillary coatings such as polyacrylamide, poly‐(ethylene oxide) and polybrene (PB) were evaluated to overcome the poor efficiencies obtained with fused‐silica capillary. Although peak asymmetry values were quite similar for the three investigated coatings, the peak efficiencies were 35‐fold and 5‐fold higher with PB coating than with polyacrylamide and poly(ethylene oxide) coatings, respectively. The recovery percentage (over 97%) was satisfactory and confirmed the efficacy of PB coating to limit the adsorption of tau protein to capillary walls. Moreover, PB coating produced higher repeatability for migration times (RSD values <1.2%) in comparison to the neutral coatings. The potential of PB‐modified capillary in producing high resolutive separations of one phosphorylated tau isoform from its unphosphorylated counterpart and of a mixture of phosphorylated and unphosphorylated tau peptides was demonstrated with 50 mM phosphate buffer pH 3.0. The separation of unphosphorylated tau isoform 352 (Tau‐352) from Tau‐352 phosphorylated in vitro by the mitogen‐activated protein kinase ERK2, was accomplished in less than 15 min. 相似文献
997.
Gigault J Le Hécho I Dubascoux S Potin-Gautier M Lespes G 《Journal of chromatography. A》2010,1217(50):7891-7897
Asymmetrical flow field-flow fractionation (AFlFFF) hyphenated to multi-angle laser-light scattering (MALS) was evaluated in order to determine single walled carbon nanotube (SWCNT) length distribution. Fractionation conditions were investigated by examining mobile phase ionic strength and pH, channel components and cross-flow rate. Ammonium nitrate-based mobile phase with 10(-5)molL(-1) ionic strength and pH 6 allows the highest sample recovery (89±3%) to be obtained and the lowest loss of the longest SWCNT. A cross-flow rate of 0.9mLmin(-1) leads to avoid any significant membrane-sample interaction. Length was evaluated from gyration radius measured by MALS by comparing SWCNT to prolate ellipsoid. In order to validate the fractionation and the length determination obtained by AFlFFF-MALS, different SWCNT aliquots were collected after fractionation and measured by dynamic light scattering (DLS). AFlFFF is confirmed to operate in normal mode over 100-2000nm length. MALS length determination after fractionation is found to be accurate with 5% RSD. Additionally, a shape analysis was performed by combining gyration and hydrodynamic radii. 相似文献
998.
Judzentiene A Budiene J Butkiene R Kupcinskiene E Laffont-Schwob I Masotti V 《Natural product communications》2010,5(12):1981-1984
The chemical composition of the essential oils of aerial parts of Artemisia campestris ssp. campestris, collected from ten different locations in Lithuania is detailed in this paper. The major component in all the oils was caryophyllene oxide (8.5-38.8%), whereas compounds with the caryophyllane skeleton ranged from 10.2 to 44.5%. Other representative constituents were germacrene D (< or = 15.0%), humulene epoxide II (< or = 8.1%), beta-ylangene (< or = 7.7%), spathulenol (< or = 6.8%), beta-elemene (< or = 6.8%), beta-caryophyllene (< or = 6.2%), junenol (< or = 6.1%) and alpha- or beta-pinene (< or = 5.5%). Eighty-seven compounds were identified, comprising 73.6-92.3% of the oils. The chemical composition was highly variable depending on the sample location. Toxicity of A. campestris oils was determined using the brine shrimp (Artemia sp.) assay. LC50 values ranging to 20 microg/mL were obtained for three of the oils after 24 hours of exposure. Data of this test revealed that A. campestris ssp. campestris essential oils with dominant caryophyllene oxide are notably toxic. 相似文献
999.
Ahmed Meskini Mustapha Raihane Chady Hakme Isabelle Stevenson Gérard Seytre 《European Polymer Journal》2009,45(3):804-812
In the frame of a research aiming at developing new dielectric polymers containing CCN and CF substituents with strong dipole moment, statistical copolymers based on cyano monomers such as acrylonitrile (AN), methacrylonitrile (MAN), methylvinylidene cyanide (MVCN) and 2,2,2-trifluoroethylmethacrylate (MATRIF), were synthesized and characterized. Elemental analysis has shown that the molar percentages of AN and MAN in the copolymers were 45 mol.%, while only 5 mol.% of MVCN was incorporated in the poly(MVCN-co-MATRIF) copolymer. These copolymers exhibit glass transition temperatures, Tg, in the range of 70-90 °C. The dynamic dielectric analyses and their complex permittivities of these copolymers were studied versus the temperature and the frequency. Evidence of an α-relaxation phenomenon in the glass transition region, which is confirmed by the Vogel-Fulcher-Tammann (VFT) temperature dependence of the relaxation times, was assigned to the cooperative reorientation motions of the cyano groups. The values of dielectric strength (Δε) for the copolymers based on MATRIF were determined by Havriliak-Negami (HN) fitting from the dispersion curves, and can be related to the polarity of the monomer unit and to the packing of the macromolecular chains. These relaxations are sometimes overlapped by conduction phenomena due to ionic impurities at low frequencies and high temperatures dipolar losses. In the glassy state, the permittivity values of AN and MAN copolymers show an increase of polarity which makes them candidates for some applications amongst advanced electrical materials such as dielectric layer for capacitors. 相似文献
1000.
Evelyne Neau Otilio Hernández-Garduza Joan Escandell Christophe Nicolas Isabelle Raspo 《Fluid Phase Equilibria》2009
A theoretical analysis of the strengths and weaknesses of the Soave, Twu and Boston–Mathias attractive terms was performed with the Redlich–Kwong EoS. Special attention was paid to the variations of the alpha functions and their first and second derivatives with respect to temperature. Contrary to the Soave function, abnormal behaviors of the derived Twu and Boston–Mathias functions were evidenced in the temperature range commonly covered by industrial applications. The unsuccessful variations of the derived alpha functions observed with these two last models strengthen the interest of the Soave equation for the modeling of derived thermodynamic properties. The accuracy of pure component data modeling by means of the cubic equation of state is discussed in a second part. 相似文献