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991.
K. Ghosh A. Dutta J.K. Bhattacharjee 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):219-221
We calculate using diagrammatic perturbation theory in the two-loop approximation, the specific heat exponent for the classical N-vector model in a random external field for spatial dimension (D) lying between four and six. The calculation supports the modified hyperscaling , where is the correlation length exponent.
Received: 18 March 1998 / Revised: 17 April 1998 / Accepted: 21 April 1998 相似文献
992.
Porous Solids Arising from Synergistic and Competing Modes of Assembly: Combining Coordination Chemistry and Covalent Bond Formation 下载免费PDF全文
Ananya Dutta Dr. Kyoungmoo Koh Dr. Antek G. Wong‐Foy Prof. Adam J. Matzger 《Angewandte Chemie (International ed. in English)》2015,54(13):3983-3987
Design and synthesis of porous solids employing both reversible coordination chemistry and reversible covalent bond formation is described. The combination of two different linkage modes in a single material presents a link between two distinct classes of porous materials as exemplified by metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). This strategy, in addition to being a compelling material‐discovery method, also offers a platform for developing a fundamental understanding of the factors influencing the competing modes of assembly. We also demonstrate that even temporary formation of reversible connections between components may be leveraged to make new phases thus offering design routes to polymorphic frameworks. Moreover, this approach has the striking potential of providing a rich landscape of structurally complex materials from commercially available or readily accessible feedstocks. 相似文献
993.
Clint D. Gamlin Naba K. Dutta Namita Roy Choudhury 《Polymer Degradation and Stability》2003,80(3):525-531
The thermal degradation behavior of a range of ethylene-propylene-diene (EPDM) elastomers, covering the whole range of composition, has been examined under isothermal conditions between 410 and 440 °C using thermogravimetric analysis. The kinetic parameters of degradation for the polymers have been evaluated using different mathematical models based on different proposed mechanisms of degradation. The experimental data were fitted to the models using non-linear regression analysis technique based on Marquardt-Levenberg algorithm. It appears that the degradation of EPDMs follows the Avrami-Erofeev two-dimensional nucleation model or a random chain-scission mechanism. No observable trend was found between the ethylene content of EPDM and the activation energy of degradation. 相似文献
994.
High-energy ball milling of monoclinic ZrO2–30 mol% anatase TiO2 mixture at different durations results in the formation of m-ZrO2–a-TiO2 solid solution from which the nucleation of nanocrystalline cubic (c) ZrO2 polymorphic phase sets in. Post-annealing of 12 h ball-milled sample at different elevated temperatures for 1 h results in almost complete formation of c-ZrO2 phase. Microstructure of the unmilled, all the ball milled and annealed samples has been characterized by Rietveld's X-ray powder structure refinement method. Particle size, rms lattice strain, change in lattice parameters and phase content of individual phases have been estimated from Rietveld analysis, and are utilized to interpret the results. In course of milling, (1 1 1) of cubic lattice became parallel to () plane of monoclinic lattice due to the orientation effect and cubic phase may have been formed on the (0 0 1) of the m-ZrO2–a-TiO2 solid solution lattice. A comparative study of microstructure and phase transformation kinetics of ZrO2–10, 20 and 30 mol% a-TiO2 ball-milled and post-annealed samples reveals that rate of phase transformation m→c-ZrO2 increases with increasing a-TiO2 concentration and 30 mol% of nanocrystalline c-ZrO2 phase can be obtained within 4 h of milling time in the presence of 30 mol% of a-TiO2. The post-annealing treatment at 773, 873 and 973 K for 1 h duration each reveals that rate of c-ZrO2 formation with increasing temperature is retarded with increasing a-TiO2 concentration but the amount of c-ZrO2 becomes almost equal (95 mol%) at 973 K. It suggests that almost fully stabilized nanocrystalline c-ZrO2 can be formed by adding a tetravalent solute to m-ZrO2. 相似文献
995.
996.
Raghvendra S. Yadav Ranu K. Dutta Manvendra Kumar Avinash C. Pandey 《Journal of luminescence》2009,129(9):1078-1082
Nano-size YBO3:Eu3+ phosphor has been synthesized by the co-precipitation method. X-ray diffraction (XRD) pattern confirmed the formation of hexagonal vaterite-type structures of YBO3:Eu3+ nanoparticles. The transmission electron microscopy (TEM) study revealed the formation of spherical YBO3:Eu3+ nanoparticles with size 20-40 nm. The photoluminescence spectra revealed that the ratio of the red emission (5D0-7F2) to the orange emission (5D0-7F1) was much higher in the synthesized nano-size YBO3:Eu3+ phosphor. The improved relative intensity, i.e., higher R/O value of emission peaks, is due to a lower symmetry of crystal field around Eu3+ ions. 相似文献
997.
998.
Dependence of amplification without inversion (AWI) on the relative strength of probe and coherent field Rabi frequencies
has been studied in H2 and LiH molecules for three-level Λ configuration. We have derived exact analytical expressions for coherences and populations
keeping all the orders of probe field Rabi frequency (G) and coherent field Rabi frequency. (Θ) in the steady state limit. Previously, first-order approximation (i.e. keeping only
the first-order term in G) was used and hence AWI was studied for the condition Θ>>G. Here, by using the exact analytical expressions of coherences and populations, we have shown that AWI is maximum when Θ
is within the same order of probe field Rabi frequency G irrespective of the choice of different ro-vibrational transitions in both the molecules. However, the shape of the gain
profile and the maximum value of gain on the probe field and the absorption on coherent field depend on the choice of different
ro-vibrational levels as the upper lasing levels. Effect of bidirectional pumping, homogeneous and inhomogeneous broadening
on AWI process has been studied. By solving the density matrix equations numerically it has been shown that both the transient
and the steady state AWI can be obtained and the numerical values of coherences and populations at large time are in very
good agreement with exact analytical values in the steady state limit. It has been shown that in molecules AWI can be obtained
on probe field of smaller wavelength than that of the coherent field which has not been observed in atoms so far. 相似文献
999.
Convexifactors, Generalized Convexity, and Optimality Conditions 总被引:3,自引:0,他引:3
The recently introduced notion of a convexifactor is further studied, and quasiconvex and pseudoconvex functions are characterized in terms of convexifactors. As an application to a chain rule, a necessary optimality condition is deduced for an inequality constrained mathematical programming problem. 相似文献
1000.