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91.
Magnesium-aluminum-iron layered hydroxides with hydrotalcite-like structure have been synthesized, and their chemical composition and crystal lattice parameters have been elucidated. Thermal decomposition of the iron-containing layered hydroxides has been studied by X-ray diffraction, thermogravimetry, and IR spectroscopy; the decomposition starts with loss of interlayer water, followed by dehydroxylation of metal hydroxide layers and decomposition of anions at higher temperature. Onset of the both decomposition stages has been shifted to lower temperature with increasing iron fraction in the sample. Magnesium-aluminum-iron hydroxides restore their structure after annealing and subsequent rehydration. 相似文献
92.
I. I. Lebedeva D. M. Kisel’kov V. A. Val’tsifer 《Russian Journal of Inorganic Chemistry》2018,63(9):1131-1140
By X-ray powder diffraction analysis, Raman spectroscopy, scanning and transmission electron microscopy, and low-temperature nitrogen adsorption method, it was studied how the temperature of hydrothermal synthesis affects the phase composition of precursor species and the structure and morphology of alumina obtained under conditions of low-temperature hydrothermal synthesis at 90–130°C in the system 0.5Al2(SO4)3 · 18H2O∥0.2C16H33(CH3)3NBr∥5i-PrOH∥85H2O∥2CO(NH2)2. It was found that, at THTS = 90–110°C, alumina microspheres with globular structure form from X-ray amorphous hydrated alumina with an admixture of NH4Al3(SO4)2(OH)6. It was shown that needle-like alumina particles with slitlike pores form from NH4Al(OH)2CO3 obtained at THTS = 110–120°C. At THTS = 130°C, under conditions of the formation of γ-AlOOH, alumina spherulites constituted by needle-like particles with block–layer structure form. It was determined that the temperature range of the formation of metastable crystalline modifications of alumina is controlled by the phase composition of hydrothermal synthesis products. 相似文献
93.
Konstantin V. Pochivalov Yaroslav V. Kudryavtsev Tatyana N. Lebedeva Lyubov A. Antina Anna N. Ilyasova Mikhail Yu. Yurov Andrey V. Basko Alexander E. Zavadskii 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2225-2233
Constructing phase diagrams for the mixtures of semicrystalline polymers and low molecular mass substances by DSC can meet with difficulties in the case of slow polymer crystallization. A problem of this kind is encountered for high-energy compositions poly[3,3-bis(azidomethyl)oxetane] (PBAMO)–2,4-dinitro-2,4-diazapentane (DNAP). In this study, the experimental phase diagram PBAMO–DNAP is constructed by an optical method, which makes it possible to visualize structural transformations. The kinetic studies by DSC and XRD reveal that 30–50 days of storing a homogenized PBAMO–DNAP mixture at room temperature are needed to attain stationary values of the crystallinity degree and heat of fusion. Even after that, the DSC method cannot deliver a solubility curve of DNAP in PBAMO, which is naturally generated by the optical method. This curve separates a domain of physical gels, effectively crosslinked by polymer crystallites and swollen with the plasticizer molecules, from a two-phase domain, in which the above gel reaches osmotic equilibrium with the pure plasticizer. It is also shown that the melting temperature of DNAP drops with growing the PBAMO content in the mixture, which is consistent with a decrease in the mean size of plasticizer crystals formed in polymer pores during the previous cooling. 相似文献
94.
Thermal oxidative destruction of complexes of heterocyclic N-oxides with Zn(II)tetra-phenylporphyrin
N. Sh. Lebedeva W. Zielenkiewicz E. Utzig Y. A. Gubarev V. P. Andreev Ya. P. Nizhnik 《Journal of Thermal Analysis and Calorimetry》2008,91(2):601-608
Thermogravimetry, differential thermal analysis and differential scanning calorimetry were applied for investigation of molecular
complexes of heterocyclic N-oxide with zinc(II)tetraphenylporphyrin. The kinetic characteristics of the process of the thermal
oxidative destruction for individual compounds and their molecular complexes have been calculated. The obtained results indicate
that the complex formation of ZnTPhP with heteroaromatic N-oxides leads to an increase of the thermal stability both the metalloporphyrin
and the ligands. It has been shown that the stability of the molecular complexes of ZnTPhP with heteroaromatic N-oxides depends
on basicity of the coordinated ligand. 相似文献
95.
Lebedeva NV Sun FC Lee HI Matyjaszewski K Sheiko SS 《Journal of the American Chemical Society》2008,130(13):4228-4229
Adsorption-induced degradation of brushlike macromolecules was monitored through molecular imaging by atomic force microscopy. The rate constant for C-C bond cleavage was shown to be extremely sensitive to the substrate surface energy. A few percent increase in the surface energy from 69.2 to 71.2 mN/m led to an order of magnitude increase of the scission rate. The absolute values of the rupture forces ranging from 2.57 to 2.47 nN are in agreement with previously calculated and measured values for stretching surface-tethered molecules. 相似文献
96.
A. N. Il’yasova G. A. Shandryuk Y. V. Kudryavtsev T. N. Lebedeva M. Lutovac K. V. Pochivalov 《Polymer Science Series A》2016,58(6):1017-1024
The state diagram of the low-density polyethylene–p-xylene system that contains the solubility curve of p-xylene in the polymer is first built using the optical method with the involvement of the DSC data. It has been shown that, at 72°C, in a blend with a polymer mass fraction of 0.28, the full amorphization of the polymer proceeds simultaneously with the dissolution of p-xylene in it. Blends with a lower polymer content are also homogenized at the same temperature, although the duration of this process can take several days. In blends with a high polymer content, homogenization occurs at a higher temperature. This process is preceded by the formation of microheterogeneous single-phase gel with network junctions as polymer crystallites and amorphous regions saturated by p-xylene. Cooling of the homogeneous blends to–20°С is not accompanied by the full separation of low- and high-molecular-mass phases; in this case p-xylene not only forms an individual crystalline phase, but also partially crystallizes in amorphous regions of the polymer. 相似文献
97.
A. L. Volynskii D. A. Panchuk S. V. Moiseeva S. S. Abramchuk O. V. Lebedeva L. M. Yarysheva N. F. Bakeev 《Polymer Science Series A》2009,51(3):302-310
A newly proposed microscopic procedure makes it possible to estimate the strength of thin (nano-metric) coatings deposited onto various polymer supports. The strength of the deposited coating is shown to increase dramatically when the thickness of the coating decreases below 15 nm. It was also found that the strength of the coatings is controlled by the physical state of the polymer support. The Interfacial layer formed at the early stages of metal deposition onto the polymer surface is characterized by a higher strength as compared with that of a pure metal deposited onto the above interfacial layer. This observation can be explained by the following reasons: first, the dimensions of metallic grains in the interfacial layer are much smaller than those in a pure metal and, second, the intergrain space in the interfacial layer is filled with polymer matrix. At the same time, both the temperature and the adsorptionally active liquid medium affect polymer partitions in the interfacial composite layer and thus control the overall strength of thin coatings (≤15 nm). In the case of thicker coatings, the strength of the coating gradually decreases independently of the nature and state of the supporting polymer and approaches the strength of the bulk metal. 相似文献
98.
Densities of dilute solutions of 1,3-dimethyl-2-imiazolidinone in H2O and D2O, with the solute mole-fractions ranging up to 0.01, have been measured with an error of 1.5 · 10−5 g · cm−3 at (278.15, 288.15, 298.15, 308.15, 313.15, and 318.15) K and atmospheric pressure using a vibrating-tube densimeter. The partial molar volumes of the dissolved DMI (down to the infinite dilution) and solvent (H2O or D2O) as well as the excess molar volumes of the isotopically distinguishable solutions have been calculated. The effects of the solvent isotope substitution, solute concentration and temperature on the volume changes caused by DMI hydration have been considered. The obvious relationship between the D2O–H2O solvent isotope effects on the partial molar volume and enthalpy of solution of DMI has been discovered. 相似文献
99.
Thermal behavior of quinoline <Emphasis Type="Italic">N</Emphasis>-oxide hydrates and deuterohydrate
Yu. A. Gubarev N. Sh. Lebedeva V. P. Andreev G. V. Girichev 《Russian Journal of General Chemistry》2009,79(6):1183-1190
Spectral and thermochemical investigation of physicochemical properties of quinoline N-oxide crystallohydrates with H2O and D2O is carried out. Quinoline N-oxide is established to form with H2O a stable dihydrate where two water molecules are energetically not equal. Complete dehydration of quinoline N-oxide occurs when temperature reaches 150°C. With accounting for the obtained thermochenical data, quinoline N-oxide and its mono- and dihydrates are isolated in the individual state and their IR spectra are registered and considered. It is established that at boiling quinoline N-oxide in D2O proceeds chemical reaction affording isoindoline-1,3-dione (phthalimide). The product is identified by elemental analysis and 1H NMR and IR spectroscopy. The band assignment in the IR spectra of quinoline N-oxide, phthalimide and of the complex of the latter with D2O is based on the quantum-chemical DFT calculations. 相似文献
100.
J. Adamczewski-Musch P. Akishin K. -H. Becker S. Belogurov J. Bendarouach N. Boldyreva C. Deveaux V. Dobyrn M. Dürr J. Eschke J. Förtsch J. Heep C. Höhne K. -H. Kampert A. Khanzadeev L. Kochenda J. Kopfer P. Kravtsov I. Kres S. Lebedev E. Lebedeva E. Leonova S. Linev T. Mahmoud J. Michel W. Niebur E. Ovcharenko V. Patel C. Pauly D. Pfeifer S. Querchfeld J. Rautenberg S. Reinecke Y. Riabov E. Roshchin V. Samsonov V. Schetinin O. Tarasenkova M. Traxler C. Ugur M. Vznuzdaev 《Physics of Particles and Nuclei Letters》2017,14(6):904-912
The CBM RICH detector is an integral component of the future CBM experiment at FAIR, providing efficient electron identification and pion suppression necessary for the measurement of rare dileptonic probes in heavy ion collisions. An overview of the CBM RICH readout and DAQ system prototype is given, consisting of the PADIWA preamplifier-discriminator board, the TDC-HUB board TRBv3, and DAQ and analysis code in the CbmRoot framework. The laboratory setup built for studying the timing characteristics of the readout chain and the analysis results obtained using the laboratory measurements are presented. The fine time calibration and inter-channel delay correction techniques and their implementation and effect are discussed. 相似文献