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31.
Hannes Orelma Antti Korpela Vesa Kunnari Ali Harlin Anna Suurnäkki 《Cellulose (London, England)》2017,24(4):1691-1704
Reinforcing of cellulose nanofibril (CNF) films by partial dissolution with N-methylmorpholine-N-oxide (NMMO) was investigated. The method investigated is composed of impregnation of CNF film with liquid solution of NMMO followed by dry heat activation. The heat activation of the impregnated film was carried out using a heated calendering nip, which enabled simultaneous heating and compression. The partial dissolution of cellulose by NMMO caused a significant increase in the transparency of CNF film due to the decrease of film porosity and increased surface smoothness. The dry strength of the reinforced film was increased from 122 up to 195 MPa. Furthermore, the wet strength of the reinforced film was up to 70% greater than the dry strength of pure CNF film. The changes in the fibrillar structure were investigated with topographical imaging (SEM and AFM) and spectroscopically using NMR and FTIR. No significant changes in the fibril structure or cellulose morphology were observed. Moreover, the treated film resisted significant water pressure, highlighting CNF film’s permanent water resistance. The partial dissolution process with NMMO was also capable of reinforcing a CNF composite film with macro scale structural elements (lyocell short-cut fibres). The strategy investigated is a robust and fast method to improve the mechanical properties of fibrillary cellulose films, allowing them utilization in applications where improved water resistance and fully cellulosic character are required properties. 相似文献
32.
An equivalent plastic strain gradient theory [1] is extended to account for finite strains. The presented model considers discontinuities of the equivalent plastic strain at grain boundaries by using enriched trial functions in the Finite-Element discretization. As a consequence, a grain boundary flow rule is introduced, depending on both the mean value and the jump of the equivalent plastic strain. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
33.
Eric J. Bylaska Kiril Tsemekhman Scott B. Baden John H. Weare Hannes Jonsson 《Journal of computational chemistry》2011,32(1):54-69
Semi‐local functionals commonly used in density functional theory (DFT) studies of solids usually fail to reproduce localized states such as trapped holes, polarons, excitons, and solitons. This failure is ascribed to self‐interaction which creates a Coulomb barrier to localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid‐DFT, e.g., B3LYP and PBE0) have shown to promise in rectifying this type of failure, as well as producing more accurate band gaps and reaction barriers. The evaluation of exact exchange is challenging for large, solid state systems with periodic boundary conditions, especially when plane‐wave basis sets are used. We have developed parallel algorithms for implementing exact exchange into pseudopotential plane‐wave DFT program and we have implemented them in the NWChem program package. The technique developed can readily be employed in Γ‐point plane‐wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car‐Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
34.
Schüttig H Grotemeyer J 《European journal of mass spectrometry (Chichester, England)》2011,17(5):465-475
Photodissociation (PD) mass spectra and mass selected (1+1)-photodissociation spectra of C(2)H(5)I(+?), C(2)D(5)I(+?),1- C(3)H(7)I(+?), 2-C(3)H(7)I(+?), 1-C(4)H(9)I(+?) and 2- C(4)H(9)I(+?) radical cations were studied within the ? ← X~ absorption band. The photodissociation mass spectra within the range 13,600-15,900 cm(-1) (1.68-1.97 eV) evidence only a simple cleavage of the C-I bond and formation of the corresponding alkyl ions. The resonant (1+1)-photodissociation spectra of C(2)H(5)I(+?) and C(2)D(5)I(+?) show intense vibrational structure in the excited ? state. The thresholds for formation of the states of C(2)H(5)I(+?) and C(2)D(5)I(+?) were estimated to be (13,278 ± 12) cm(-1) (1.6462 ± 0.0014 eV)and (13,363 ± 12) cm(-1) (1.6586 ± 0.0014 eV), respectively. Whereas a few resonant vibronic excitations could be identified with 1-C(3)H(7)I(+?) and 1- C(4)H(7)I(+), no vibrational features were observable with 2- C(3)H(7)I(+?) and 2-C(4)H(9)I(+?). It is concluded that 1- and 2-iodoalkane radical cations do not rearrange, even under the conditions of electron ionisation used to generate the molecular ions. 相似文献
35.
Lilo K. Mailnder Peter Lorenz Hannes Bitterling Florian C. Stintzing Rolf Daniels Dietmar R. Kammerer 《Molecules (Basel, Switzerland)》2022,27(23)
Matricaria recutita L., German chamomile, is one of the most widely used medicinal plants, whose efficacy has been proven in numerous studies. However, its roots have attracted only little interest so far, since mainly above-ground plant parts are used for medicinal purposes. To broaden the knowledge of chamomile roots, a profound phytochemical characterization was performed along with a bioactivity screening of corresponding root extracts. While volatile constituents such as chamomillol and polyynes were detected using GC-MS, HPLC-MSn analyses revealed the occurrence of four coumarin glycosides, more than ten phenolic acid esters and five glyceroglycolipids. Furthermore, the antioxidant activity of the extracts was evaluated. Polar extracts revealed IC50 values ranging from 13 to 57 µg/mL in the DPPH radical scavenging assay, which is in the same range as reported for chamomile flower extracts. In addition, superoxide radical scavenging potential and mild antibacterial effects against S. aureus und B. subtilis were demonstrated. Moreover, to assess interspecies variation in chamomile roots, extracts of M. recutita were compared to those of M. discoidea DC. Interestingly, the latter revealed stronger antioxidant activity. The presented results aim at the valorization of chamomile roots, previously discarded as by-product of chamomile flower production, as a sustainable source of bioactive phytochemicals. 相似文献
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Classical parameters obtained from surface tension technique coupled to small angle X-ray scattering (SAXS) measurements gave support to investigate conformational changes in the bovine serum albumin (BSA)-sodium dodecyl sulfate (SDS) complexes, as well as the size of the micelle-like clusters distributed along the polypeptide chain. The studied systems were composed of 1 wt% of BSA in the absence and presence of increasing SDS molar concentration up to 80 mM, under experimental conditions of low ionic strength and pH 5.40. At SDS concentrations below the critical aggregation concentration (cac) of 2.2 mM, SAXS results indicate that the detergent does not modify the native protein conformation. However, the beginning of protein unfolding, evidenced by SAXS through an increase in the values of radius of gyration Rg and protein maximum dimension Dmax, is coincident with the onset of SDS cooperative binding to BSA identified by the first breakpoint in the surface tension-SDS profile. Further SDS addition leads to the formation of micelle-like aggregates randomly distributed along the unfolded polypeptide chain, consistent to a necklace and bead model. The SAXS data also demonstrate that the SDS micelles grow in size up to 50 mM detergent. At 50 mM surfactant, the micelles stop growing. This concentration is near the BSA saturation binding by SDS measured by dialyzes and indicated by the second breakpoint in surface tension-SDS profile. The SAXS and surface tension data are also consistent with the formation of free micelles in equilibrium with BSA-SDS complexes for surfactant amount above the saturation. 相似文献
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40.
Hannes Aiginger 《Zeitschrift für Physik A Hadrons and Nuclei》1966,197(1):8-25
The bremsstrahlung cross sections, differential in photon energy and angle have been determined by measuring the x-rays emitted from thin targets (Al2O3: 56,5 and 113 μg/ cm2; Au: 9,7 and 24,4 μg/cm2) for incident electron energies of 180 and 380 keV with a 5×5 inch NaI scintillation spectrometer at angles from 0 to 150 degrees. A response matrix is used to convert the measured pulse height distribution into the spectrum of photons incident on the spectrometer. The results show that in this energy region the Bethe-Heitler-Sauter (Born approximation) theory underestimates the cross sectionsd 2 σ/dk · dΩ anddσ/dk. The application of the Elwert factor gives a considerable improvement. For Al2O3 the Elwert corrected Born approximation gives values which are generally within the limits of error of the measurements. The experimental values of theHeitler parameter\(\Phi _{rad} /\bar \Phi \) are 5,0 (Al2O3) and 6,7 (Au) for 180 keV and 5,6 (A12O3) and 7,3 (Au) for 380 keV. The angular distribution of the radiation has been compared with some characteristic angles predicted by the theory ofSommerfeldKulenkampff. Special consideration has been given to the high frequency limit. The cross sections at this energy have been derived from the correctedSauter-Fano theory and are in good agreement with the measurements. 相似文献