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101.
M. Rodrigues M. Schreiner M. M?der M. Melcher M. Guerra J. Salomon M. Radtke M. Alram N. Schindel 《Applied Physics A: Materials Science & Processing》2010,99(2):351-356
We report the results of an analytical investigation on 416 silver-copper coins stemming from the Ottoman Empire (end of 16th
and beginning of 17th centuries), using synchrotron micro X-ray fluorescence analysis (SRXRF). In the past, analyses had already
been conducted with energy dispersive X-ray fluorescence analysis (EDXRF), scanning electron microscopy with energy dispersive
X-ray spectrometry (SEM/EDX) and proton induced X-ray emission spectroscopy (PIXE). With this combination of techniques it
was possible to confirm the fineness of the coinage as well as to study the provenance of the alloy used for the coins. 相似文献
102.
103.
104.
Luca Stabellini Wei Lu Alfredo De Rossi Thomas Antoni Mathieu Carras Stefano Trillo Gaetano Bellanca 《Optical and Quantum Electronics》2008,40(14-15):1085-1090
A Finite Difference Time Domain approach is used to design and to optimize quantum-well based infrared photodetectors. Results showing the influence of some parameters on the performance of these devices are presented and discussed. 相似文献
105.
Rendiconti del Circolo Matematico di Palermo Series 1 - 相似文献
106.
Francesco P. Ballistreri Lucia Brinchi Raimondo Germani Gianfranco Savelli Gaetano A. Tomaselli Rosa M. Toscano 《Tetrahedron》2008,64(44):10239-10243
An aqueous reaction medium, based on a surfactant solution of diethyltetradecylamine N-oxide (AOE-14), was developed for the enantioselective epoxidation of 1,2-dihydronaphthalene and of various cis-β-alkyl styrenes with increasing hydrophobicity, using bleach as oxidant and the Jacobsen chiral (salen)Mn(III) as catalyst. AOE-14 is able to both solubilize all reactants in water and bind the metal of the salen complex acting as coligand. Its use leads to good yields (>75%) and to ee values ranging from 75% up to 91% even in the case of cis-β-alkyl styrenes where lower cis/trans epoxide ratios are observed. The ratio of surfactant/substrate used is 1:1 or 4:1, much lower than those generally used in the literature. 相似文献
107.
Francisca Zamora Khalid Hakkou Abdelillah Alla Manuel Rivas Antxón Martínez De Ilarduya Sebastián Muñoz‐Guerra Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2009,47(4):1168-1177
The synthesis, characterization, and some properties of new copolyesters analogous to poly(butylene terephthalate) (PBT), based on L ‐arabinaric and galactaric acids, are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of methyl 2,3,4‐tri‐O‐methyl‐L ‐arabinarate or methyl 2,3,4,5‐tetra‐O‐methyl‐galactarate and dimethyl terephthalate with 1,4‐butanediol. Their weight‐average molecular weights ranged between 10,000 and 34,000, with polydispersities ranging from 1.4 to 2.2. The composition of all the copolymers was analyzed by NMR, and was found to have a statistical microstructure. All these copolyesters were thermally stable, with degradation temperatures well above 300 °C. The melting temperature and crystallinity decreased in both series, and the glass transition temperature increased and decreased respectively, for the PBTGa and PBTAr series with increasing amounts of aldaric units in the copolyester chain. Only PBT‐derived copolyesters containing a maximum of 30% aldaric units showed discrete scattering characteristic of crystalline material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1168–1177, 2009 相似文献
108.
Célia Fonseca Guerra Tushar van der Wijst Jordi Poater Marcel Swart F. Matthias Bickelhaupt 《Theoretical chemistry accounts》2010,125(3-6):245-252
We have investigated the performance of the dispersion-corrected density functionals (BLYP-D, BP86-D and PBE-D) and the widely used B3LYP functional for describing the hydrogen bonds and the stacking interactions in DNA base dimers. For the gas-phase situation, the bonding energies have been compared to the best ab initio results available in the literature. All dispersion-corrected functionals reproduce well the ab initio results, whereas B3LYP fails completely for the stacked systems. The use of the proper functional leads us to find minima for the adenine quartets, which are energetically and structurally very different from the C4h structures, and might explain why adenine has to be sandwiched between guanine quartets to form planar adenine quartets. 相似文献
109.
Paula Guerra Ethel Eljarrat Damià Barceló 《Analytical and bioanalytical chemistry》2010,397(7):2817-2824
This paper describes the development of a methodology for the simultaneous determination and quantification of hexabromocyclododecane
(HBCD), tetrabromobisphenol A (TBBPA), and related compounds (bisphenol A, monobromobisphenol A, dibromobisphenol A, and tribromobisphenol
A) in sludge and sediment samples. The selected method is based on an extraction with dichloromethane: methanol followed by
purification via SPE C18 cartridges. Instrumental determination was carried out by liquid chromatography–quadrupole linear ion trap mass spectrometry
(LC-QqLIT-MS), with quantification based on isotopic dilution method. Analyte recoveries were in the range of 39–120% and
88–126% for spiked sewage and sediment, respectively. Repeatability of replicate extractions was better than 13% relative
standard deviation. Linearity was checked in the range of 0.05 and 25 injected nanograms. Limits of detection (LODs) and limits
of quantification (LOQs) were in the range of 0.6 and 2.7 ng/g and 1.4 and 66 ng/g for sediment and sludge samples, respectively.
The developed method was applied to sewage sludge and sediment samples collected along the Ebro River and Cinca River, one
of its tributaries (northeast of Spain). TBBPA levels in sewage sludge ranged from not quantified to 1,329 ng/g dw, whereas
levels in sediment samples were lower, between not detected and 15 ng/g dw. As regards HBCD, concentrations were between not
detected and 375 ng/g for sludge samples and 0.8 and 1850 ng/g for sediments. 相似文献
110.
Two different kinds of organoclays were prepared by mixing a pristine montmorillonite and a double‐chain ammonium salt in many different thermoplastic or elastomeric polymers. Independently of the chemical nature of the considered polymers, the obtained organoclays presented a basal spacing of 4 or 6 nm, when the mixing occurred in the absence or in the presence of a small amount of stearic acid (SA), respectively. X‐ray diffraction and Fourier transform infrared measurements support the hypothesis that these two kinds of organoclays correspond to paraffin‐type tilted and perpendicular bi‐layer intercalates, respectively. The co‐intercalation of SA molecules with the double‐chain amphiphile is suggested, to explain the observed expansion of the clay interlayer distance. The obtained results suggest an easy way to control the organoclay structure in polymer composites. Moreover, the authors on the basis of these results propose a criticism to the extensive literature that systematically explains most d basal spacing increase observed for clays in polymer with the penetration of apolar polymer chains in the clay interlayer space. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献