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951.
Yu Min Han Zhi Li Jiu Li Luo 《中国化学快报》2007,18(11):1427-1430
Taking the Lindemann model as a sample system in which there exist chemical reactions,diffusion and heat conduction,we found the theoretical framework of linear stability analysis for a unidimensional nonhomogeneous two-variable system with one end subject to Dirichlet conditions,while the other end no-flux conditions.Furthermore,the conditions for the emergence of temperature waves are found out by the linear stabilily analysis and verified by a diagram for successive steps of evolution of spatial profile of temperature during a period that is plotted by numerical simulations on a computer.Without doubt,these results are in favor of the heat balance in chemical reactor designs. 相似文献
952.
John D. Ramshaw 《Journal of statistical physics》1984,35(1-2):49-75
The theory of dielectric polarization in random media is systematically formulated in terms of response kernels. The primary response kernel K(12) governs the mean dielectric response at the pointr
1 to the external electric field at the pointr
2 in an infinite system. The inverse of K(12) is denoted by L(12); it is simpler and more fundamental than K(12) itself. Rigorous expressions are obtained for the effective dielectric constant
* in terms of L(12) and K(12). The latter expression involves the Onsager-Kirkwood function (
*–
0)(2
*+
0) /0* (where 0 is an arbitrary reference value), and appears to be new to the random medium context. A wide variety of series representations for
* are generated by means of general perturbation expansions for K(12) and L(12). A discussion is given of certain pitfalls in the theory, most of which are related to the fact that the response kernels are long ranged. It is shown how the dielectric behavior of nonpolar molecular fluids may be treated as a special case of the general theory. The present results for
* apply equally well to other effective phenomenological coefficients of the same generic type, such as thermal and electrical conductivity, magnetic susceptibility, and diffusion coefficients.Work performed under the auspices of the United States Department of Energy. A preliminary report on this work was given at the Eighth West Coast Statistical Mechanics Conference, University of California, Berkeley, 22 June 1982. 相似文献
953.
BaxCe0.8Tb0.2O3-a (x=0.98-1.03) solid electrolytes were synthesized and characterized by using X-ray diffraction (XRD). By using AC impedance spectroscopy and gas concentration cell electromotive force (EMF) measurements, the electrical conduction behavior of the specimens was investigated in different gases during 500-1000 ℃ The influence of nonstoichiometry in the specimens with x ≠ 1 on conduction properties was studied and compared with that in the specimen with x = 1. The results show that the specimens are all of perovskite-type orthorhombic structure. In 500-1000 ℃, electronic hole conduction is dominant in dry and wet oxygen, air or nitrogen. Protonic conduction is dominant in wet hydrogen and it is about two orders of magnitude higher than that in hydrogen-free atmospheres (oxygen, air and nitrogen). The electrical conductivity of the same specimen in water vapor-saturated oxygen, air or nitrogen is slightly higher than that in corresponding gas without water vapor. The electrical conductivities of the nonstoichiometric specimens are higher than those of the stoichiometric one. 相似文献
954.
V.?B.?BalakirevaEmail author A.?Yu.?Stroeva V.?P.?Gorelov 《Russian Journal of Electrochemistry》2005,41(5):535-539
Values of partial conductions (ionic: protonic, oxygen, hole) and their activation energies in LaYO3 are determined at 700–1050°C, pO2 ranging from air to 10−15 Pa, and pH2O = 0.04–13.5 kPa for different versions of doping with calcium (when introduced into the lanthanum or yttrium sublattices, or into both sublattices simultaneously). The conductivity increases in the series La0.97Ca0.03YO3 − α < LaY0.97Ca0.03O3 − α < La0.985Y0.985Ca0.03O3 − α, which means that the stoichiometric composition with a 1 : 1 ratio between Y and La has the highest conductivity.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 610–615.Original Russian Text Copyright © 2005 by Balakireva, Stroeva, Gorelov. 相似文献
955.
V. Ya. Kavun N. F. Uvarov A. B. Slobodyuk O. V. Brovkina L. A. Zemnukhova V. I. Sergienko 《Russian Journal of Electrochemistry》2005,41(5):488-500
Methods of 19F NMR and impedance spectroscopy are used to investigate the internal mobility of fluoride (ammonium) ions and electrophysical characteristics of complex trivalent antimony fluorides MSb4F13, MSb3F10, MSb2F7, M2Sb3F11, M3Sb4F15, and MSbF4 (M is an alkali cation, ammonium, thallium). The ion motion types in the cationic and anionic sublattices of the fluorides are determined at 150–500 K. The polymorphous transformations in the fluorides are usually phase transitions to a superionic state and their high ionic (superionic) conductivity (σ ≥ 10−4 to 10−2 S cm−1 at 400 K) is due to the diffusion motion of ions of fluoride, ammonium, and possibly sodium, potassium, and thallium. The high polarizability of thallium ions favors the development of high mobility of fluoride ions in the fluorides.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 560–572.Original Russian Text Copyright © 2005 by Kavun, Uvarov, Slobodyuk, Brovkina, Zemnukhova, Sergienko. 相似文献
956.
Pb1-xZnxS (x = 0 to 0.4 in steps of 0.1) ternary semiconductor material shave been prepared by co-precipitation method. The structural and electrical studies have been carried out to understand the influence of Zinc on activation energy. X-ray diffractograms showed that the Pb1-xZnxS compounds are polycrystalline in nature with cubic phase. The temperature-dependent conductivity measured in the range 300–4 K showed a change in the conduction mechanism at 62 K and 31 K. The activation energies evaluated at low and very low temperature regions. Activation energy increases and conductivity decreases with the increase of Zn in Pb1-xZnxS compounds. The samples are exhibiting low freezing temperature points indicating their capability to use in low temperature applications. 相似文献
957.
Polycarboxylate‐Templated Coordination Polymers: Role of Templates for Superprotonic Conductivities of up to 10−1 S cm−1
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Dr. Syed Meheboob Elahi Santanu Chand Wei‐Hua Deng Arun Pal Dr. Madhab C. Das 《Angewandte Chemie (International ed. in English)》2018,57(22):6662-6666
Three coordination polymers (CPs) have been synthesized based on a [Co(bpy)(H2O)4]2+ chain (bpy=4,4′‐bipyridine) by a template approach. The frameworks are neutralized by different templated polycarboxylate anions (furan di‐carboxylate (fdc) in Co‐fdc, benzene tri‐carboxylate (btc) in Co‐tri and benzene tetra‐carboxylate (btec) in Co‐tetra). These templates with different degrees of protonation and ionic carrier concentration played significant role on crystal packing as well as formation of well‐directed H‐bonded networks which made these CPs perform well in proton conduction (PC). The PC value reaches to 1.49×10?1 S cm?1 under 80 °C and 98 % relative humidity (R.H.) for Co‐tri, which is the highest among CPs/MOFs/COFs and is an example of conductivity in the order of 10?1 S cm?1. Co‐tri and Co‐tetra are excellent proton conductors at mild temperature (40 °C) and 98 % R.H. (conductivities up to 2.92×10?2 and 1.38×10?2 S cm?1, respectively). 相似文献
958.
Aggregation of Giant Cerium–Bismuth Tungstate Clusters into a 3D Porous Framework with High Proton Conductivity
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Jian‐Cai Liu Qing Han Dr. Li‐Juan Chen Prof. Dr. Jun‐Wei Zhao Prof. Dr. Carsten Streb Prof. Dr. Yu‐Fei Song 《Angewandte Chemie (International ed. in English)》2018,57(28):8416-8420
The exploration of high nuclearity molecular metal oxide clusters and their reactivity is a challenge for chemistry and materials science. Herein, we report an unprecedented giant molecular cerium–bismuth tungstate superstructure formed by self‐assembly from simple metal oxide precursors in aqueous solution. The compound, {[W14CeIV6O61]([W3Bi6CeIII3(H2O)3O14][B‐α‐BiW9O33]3)2}34? was identified by single‐crystal X‐ray diffraction and features 104 metal centers, a relative molar mass of ca. 24 000 and is ca. 3.0×2.0×1.7 nm3 in size. The cluster anion is assembled around a central {Ce6} octahedron which is stabilized by several molecular metal oxide shells. Six trilacunary Keggin anions ([B‐α‐BiW9O33]9?) cap the superstructure and limit its growth. In the crystal lattice, water‐filled channels with diameters of ca. 0.5 nm are observed, and electrochemical impedance spectroscopy shows pronounced proton conductivity even at low temperature. 相似文献
959.
960.
Data on previous conductimetric studies of ionic transport in fluoride composites and vitreous materials are compiled. The F- conductivity of composites 21SrF2 · 79LaF3 (content, mol %) and 34NaF · 66PbF2 reaches 0.007 S cm-1 at 500 K and that of glasses based on InF3 and PbF2, 6 × 10-5 S cm-1 at 400 K, which exceeds that of -PbF2 and LaF3 crystals. 相似文献