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排序方式: 共有731条查询结果,搜索用时 31 毫秒
101.
Yufen Chen Tengxuan Tang Yuhua Chen Dongmei Xu 《Research on Chemical Intermediates》2018,44(4):2379-2393
A novel 1,8-naphthalimide dye with simple structure has been produced by a facile synthetic method for colorimetric and fluorescent sensing of H+ and Cu2+. In CH3CN/H2O (1/1, v/v), the dye could monitor H+ using dual channels (ratiometric absorbance and fluorescence intensity change) from pH 6.2 to 12.0. Meanwhile, in the pH range of 1.9–5.2, the dye could also be used to detect Cu2+ using triple channels [ultraviolet–visible (UV–Vis) absorption, fluorescence intensity reduction, as well as fluorescence blueshift]. The detection limits for Cu2+ evaluated by colorimetric and fluorescent titration were 6.10 × 10?7 and 2.62 × 10?7 M, respectively. The dye exhibited specific selectivity and sensitivity for H+ and Cu2+ over various coexisting metal ions. Moreover, the sensing mechanism of the dye for H+ and Cu2+ was carefully examined. 相似文献
102.
The influence of Escherichia coliform (E. coli), especially the proteins it secretes, on the nucleation, growth and aggregation processes of calcium bilirubinate (CaBR) in different mimic systems, such as NaCl aqueous solution and model bile, is studied in this paper. The results show that in NaCl aqueous solution the morphology of calcium bilirubinate (CaBR) changes from amorphous sheet structure to a highly self-organized and highly self-replicated fractal structure that is accumulated by rhombic microcrystals after the addition of E. coli. In model bile with the existence of E. coli, CaBR also forms a fractal structure, but the fractal structure is staghorn-like. Meanwhile, the composition of the prepared CaBRs is nonstoichiometric, and the crystallization is greatly improved with the existence of E. coli. Besides, formation mechanism of CaBRs affected by E. coli is explored, showing that the proteins secreted by E. coli interact with the Ca(2+) ions to provide nucleation sites for CaBRs, and the conformation of the proteins becomes more ordered, resulting in the improvement of the crystalline of CaBRs. On the other hand, the interaction of proteins and the Ca(2+) ions also promote the aggregation state of the CaBRs. 相似文献
103.
Fractional‐order switching type control law design for adaptive sliding mode technique of 3D fractional‐order nonlinear systems 下载免费PDF全文
In this article, an adaptive sliding mode technique based on a fractional‐order (FO) switching type control law is designed to guarantee robust stability for a class of uncertain three‐dimensional FO nonlinear systems with external disturbance. A novel FO switching type control law is proposed to ensure the existence of the sliding motion in finite time. Appropriate adaptive laws are shown to tackle the uncertainty and external disturbance. The calculation formula of the reaching time is analyzed and computed. The reachability analysis is visualized to show how to obtain a shorter reaching time. A stability criteria of the FO sliding mode dynamics is derived based on indirect approach to Lyapunov stability. Effectiveness of the proposed control scheme is illustrated through numerical simulations. © 2015 Wiley Periodicals, Inc. Complexity 21: 363–373, 2016 相似文献
104.
The carboranylpyrrole polymers are functional materials with superior thermal resistance and conducting performances. The carboranylpyrrole structures and Laplacian bond order (LBO) of carborane moiety, as well as the thermal resistance and conducting properties of carboranylpyrrole dimers or polymers, were investigated theoretically. The 11B NMR chemical shifts of 3-(2-methyl-o-carboranyl)alkyl-1H-pyrrole monomers (CP-1 to CP-5) were calculated and analyzed. The average LBO values of some characteristic chemical bonds in the carborane cages of CP-1 to CP-5 molecules were calculated. It is found that the average LBO values of carborane moieties change slightly with the increase in alkyl chain length. The temperature resulting in about 15–20 % weight loss for CP-1, CP-3, CP-4 and CP-5 polymers is predicted to be more than 700 °C. Apart from the C–C bonds in carborane moieties of 3-(2-R-o-carboranyl)propyl-1H-pyrrole (R = CH2OH, CH2OCH3, CN, COCl, Ph) substituents, the LBO values of other bonds in these cages change slightly relative to that in the molecule of 3-(2-methyl-o-carboranyl)propyl-1H-pyrrole (CP-3). The C–C bond LBO values in the carborane cages of these substituents with electron-donating groups (R = CH2OH, CH2OCH3) are bigger than that in CP-3, while those values in those substituents with electron-withdrawing groups (R = CN, COCl, Ph) are smaller than that in CP-3. The polymerization activity calculated for CP-1 to CP-5 monomers increases with the increase in alkyl chain length. The calculated orbital energy gap (?E LUMO?HOMO) of CP-1 to CP-5 dimers decreases with the increase in alkyl chain length, and accordingly, the electronic conductivity has the potential to increase. In addition, the calculated band gaps of CP-1 to CP-5 dimers cell models also decrease with the increase in alkyl chain length. 相似文献
105.
Feng Y Guo Y OuYang Y Liu Z Liao D Cheng P Yan S Jiang Z 《Chemical communications (Cambridge, England)》2007,(35):3643-3645
Two unprecedented 2D entangled layers of warp-and-woof threads interwoven by left- and right-handed helical chains, {[Mn(salen)Au(CN)2]4(H2O)}n (salen = N,N'-ethylenebis(salicylideneaminato)) and {Mn(acacen)Ag(CN)2}n (acacen = N,N'-ethylenebis(acetylacetonylideneiminate)) 2, have been synthesized and characterized. 相似文献
106.
Yanyan Fang Pin Ma Hongbo Cheng Guoyu Tan Jiaxin Wu Jiaxin Zheng Xiaowen Zhou Shibi Fang Yuhua Dai Yuan Lin 《化学:亚洲杂志》2019,14(23):4201-4206
Two types of ionic liquids (ILs), 1‐(3‐hexenyl)‐3‐methyl imidazolium iodide and 1‐(3‐butenyl)‐3‐methyl imidazolium iodide, are synthesized by introducing an unsaturated bond into the side alkyl chain of the imidazolium cation. These new ionic liquids exhibit high thermal stability and low viscosity (104 cP and 80 cP, respectively). The molecular dynamics simulation shows that the double bond introduced in the alkane chain greatly changes the molecular system space arrangement and diminishes the packing efficiency, leading to low viscosity. The low viscosity of the synthesized ionic liquids would enhance the diffusion of redox couples. This enhancement is detected by fabricating dye‐sensitized solar cells (DSSCs) with electrolytes containing the two ILs and I2. The highest efficiency of DSSCs is 6.85 % for 1‐(3‐hexenyl)‐3‐methyl imidazolium iodide and 5.93 % for 1‐(3‐butenyl)‐3‐methyl imidazolium iodide electrolyte, which is much higher than that of 5.17 % with the counterpart 1‐hexyl‐3‐methyl imidazolium iodide electrolyte. 相似文献
107.
108.
A new view of the spatial relation between fluctuating wall pressure and near-wall streamwise vortices (NWSV) is proposed for wall bounded turbulent flow by use of the direct numerical simulation (DNS) database. The results show that the wall region with low pressure forms just below the strong NWSV, which is mostly associated with the overhead NWSV. The wall region with high pressure forms downstream of the NWSV, which has a good correspondence with the downwash of the fluids induced by the upstream NWSV. The results provide a significant basis for the detection of NWSV. 相似文献
109.
Bangmin Zhang Guowei Wang Feng Zhang Yuhua Xiao Shihui Ge 《Applied Physics A: Materials Science & Processing》2009,97(3):657-661
A series of (FeCoNiNbB)
x
–(SiO2)1−x
nano-granular thin films were fabricated by magnetron sputtering with different oblique incidence angles θ. High-resolution transmission electron micrographs show that the films consist of amorphous CoFeM (M = Ni, Nb, B) alloy particles
with diameter about 2 nm surrounded by amorphous SiO2 matrix. Excellent soft magnetic properties have been achieved with a variable in-plane uniaxial magnetic anisotropy field
H
k0, which increases monotonically with θ and x, and decreases with the composition of B in FeCoM. For one typical sample of x=0.63 with θ=30°, H
ch and H
ce are 4.2 Oe and 5.4 Oe, respectively, ρ reaches 12.5 mΩ cm and 4π
M
s and H
k0 are 5.70 kG s and 92 Oe, respectively, which lead to a high ferromagnetic resonance frequency f
r of 2.2 GHz. Based on the analysis of experimental results, two sources for the origin of the magnetic anisotropy, namely
anisotropic magnetic coupling and orientation order of atomic pairs, are suggested. 相似文献
110.
Undoped and RE ions doped SrB2Si2O8 were successfully synthesized. After the application of UV and VUV spectroscopy measurements, we made a novel discovery that the emission of SrB2Si2O8:Eu prepared in air can be switched between red and blue by the different excitations. The information is that quite a part of Eu3+ was spontaneously reduced to Eu2+ in air. The PL properties of Eu2+ in VUV and Eu3+, Ce3+ and Tb3+ in UV-VUV region in SrB2Si2O8 were evaluated for the first time. The excitation mechanisms of the O2−-Eu3+ CT, Ce3+f-d and Tb3+f-d transitions in UV region as well as the Eu3+f-d, O2−-Ce3+ CT, O2−-Tb3+ CT transitions and the host lattice absorption in VUV region were established. In addition, first principles calculation within the LDA of the DFT was applied to calculate the electronic structure and linear optical properties of SrB2Si2O8 and the results were compared with the experimental data. 相似文献