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991.
§1 引言 限量分配问题是古典概率论,组合论的重要内容。本文将文献[1]、[2]中的一类广泛的限量分配问题给以统一的处理并加以推广,归结为如下问题: 问题Ⅰ 内无序分配问题。给定m类盒和n类球,假定第i类球和第j类盒的个数分别为r_i、s_j(1≤i≤n,1≤j≤m),即所谓球的规格为(?)=(r_1,r_2,…,r_n)和盒的规格为(?)=(s_1,s_2,…,s_m)。已知第i类盒对于球的限量集为A_i(这里A_i∈N_0~t,其中每个元素表示该类盒所能容纳之球的规格,1≤i≤m),记A=(A_1,A_2,…,A_m)。则分配规格为(?)的球至规 相似文献
992.
In Hwan Jung Young Kwan Jung Jonghee Lee Jong‐Hwa Park Han Young Woo Jeong‐Ik Lee Hye Yong Chu Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2008,46(21):7148-7161
We synthesized two fluorene‐based copolymers poly[(2,5‐bis(4‐hexylthiophen‐2‐yl)thiazolo[5,4‐day]thiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] ( PF‐TTZT), and poly[(5,5′‐bis(4‐hexylthiophen‐2‐yl)‐2,2′‐bithiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] (PF‐TBTT), which contain the electron‐withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF‐TBTT are lower than those of PF‐TTZT, and the bandgap of PF‐TBTT is smaller than that of PF‐TTZT. Thus the bithiazole moiety in PF‐TBTT is more electron‐withdrawing than the thiazolothiazole moiety in PF‐TTZT. Light‐emitting devices with indium tin oxide (ITO)/poly(3,4‐ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2‐methyl‐8‐quinolinato)‐4‐phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF‐TBTT device was found to be almost three times better than that of the PF‐TTZT device, which is because electron injection from the cathode to PF‐TBTT is much easier than for PF‐TTZT. We also investigated the planarity and frontier orbitals of the electron donor‐acceptor (D‐A) moieties with computational calculations using ab initio Hartree–Fock with the split‐valence 6‐31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron‐withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7148–7161, 2008 相似文献
993.
Mu-hua Chen Wei Chu Jun-jie Zhu Lin Dong 《Journal of Sol-Gel Science and Technology》2008,47(3):354-359
Novel cobalt catalysts were prepared by sol–gel method, and enhanced by plasma treatment, for methane catalytic combustion.
These samples were characterized using X-ray diffraction, X-ray photoelactron spectroscopy, UV-vis spectroscopy, Fourier transform
infrared spectroscopy, thermal gravimetrical analysis, N2 Adsorption–desorption, temperature-programmed reduction and hydrogen–oxygen titration technologies. The XPS characterizations
suggested that plasma treatment was favorable for the enrichment of surface cobalt, with a value of surface cobalt from 2.2%
to 8.5% in mole. The specific surface area of the glow plasma assised sample (Co-Plas-Solgel-2) increased to 320 m2/g comparing with 305 m2/g of the conventional sample (Co-Solgel-1). The ignition temperature (T10%) of Co-Plas-Solgel-2 catalyst was about 50 °C lower than that of Co-Solgel-1, and its CH4 conversion was two times higher than that of Co-Solgel-1 during the whole range of catalytic combustion activity test (340–520 °C).
With a better dispersion and more active sites, the plasma assisted sample exhibited significant enhancement in catalytic
performances. 相似文献
995.
Let λ∈N_0~k satisfying λ_1λ_2…λ_k for natural number set N_0. An orderideal λ determined by λ is defined to be {(i,j):1jλ_i,1ik}N~2. A planepartition (reverse) π of shape λ is an order- reversing (preserving) map from λto N-0. If P is any set of plane partitions, the generating function (abbrev.asGF) of P is the polynomial or fromal power series , where |π|denotethe weight of π. The enumeration theory of plane partitions is an active fieldof combinatorics. There are several approaches which have been successfully 相似文献
996.
997.
998.
Structure-related infrared optical properties of BaTiO3 thin films grown on Pt/Ti/SiO2/Si substrates
Z.G. Hu G.S. Wang Z.M. Huang J.H. Chu 《Journal of Physics and Chemistry of Solids》2003,64(12):2445-2450
BaTiO3 thin films with different thickness have been grown on Pt/Ti/SiO2/Si substrates by a modified sol-gel method. X-ray diffraction analyses show that the BaTiO3 thin films are polycrystalline. The crystalline quality of the films is improved with increasing thickness. The infrared optical properties of the BaTiO3 thin films have been investigated using an infrared spectroscopic ellipsometry in the wave number range of 800-4000 cm−1 (2.5-12.5 μm). By fitting the measured pseudodielectric functions with a three-phase model (Air/BaTiO3/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been simultaneously obtained. The refractive index of the BaTiO3 thin films increases and on the other hand, the extinction coefficient does not change with increasing thickness in the entirely measured wave number range. The dependence of the refractive index on the film thickness has been discussed in detail and was mainly due to both the crystalline quality of the films and packing density. Finally, the absorption coefficient was calculated in the infrared region for applications in the pyroelectric IR detectors. 相似文献
999.
Let RE_λ(q) denote the GF for reverse plane partitions of shape λ with part restiction (i.e., the parts in ith row do not exceed n_i). Combining domination method with the techniques of combinatorial computation, we obtain the follo wing determinant expression. 相似文献
1000.
Electrochromic effects are observed by employing a single mixed ionic and electronic conducting layer in-between two transparent
electronic leads. Besides the simplicity of the arrangement, the advantage is the displacement of ions only within one phase
rather than across phase boundaries as required by conventional devices.
The applied voltage controls the compositions at the two interfaces according to Nernst's law independent of ions being majority
or minority charge carriers. Appropriate materials are intrinsic conductors in the unpolarized transparent state which become
n-type and p-type conducting at the negative and positive electrode side, respectively. Several materials have been investigated,
such as lithiated tungsten oxide and lithium/tantalum co-doped tungsten oxide.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 September 1994. 相似文献