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961.
Wei Xu Dongliang Chen Wangsheng Chu Ziyu Wu Augusto Marcelli Annibale Mottana Alexander Soldatov Maria Franca Brigatti 《Journal of synchrotron radiation》2011,18(3):418-426
An attempt to refine the local structure of a layered structure such as mica is made by combining angle‐resolved XANES (AXANES) and single‐crystal X‐ray diffraction (SC‐XRD) experiments. Ab initio calculations of AXANES spectra of several tri‐octahedral micas have been used to further interpolate experimental data and to deduce physico/chemical effects. Structural distortions have been found highly correlated with the compositional disordering that arises from electronic interactions between anions and cations, and extend the interlayer entering deep into nearby tetrahedral and octahedral sheets. Multiple occupations at the same atomic site have been investigated in detail both in the parallel and perpendicular components of AXANES spectra. Finally, the best fit obtained, computed in the framework of the multiple‐scattering theory, is presented and the limitations of the muffin‐tin potential in layered systems are briefly discussed. 相似文献
962.
以氯化铜(CuCl2)为研究对象,通过变换有机元制备了3种结构相似的层状类钙钛矿结构的有机-无机杂合物.用扫描电子显微镜(SEM)、X射线衍射分析(XRD)和FT-IR分别对这3种杂合物的无机元、有机元和晶体结构以及各组分问的相互作用进行分析.实验结果表明,当有机元为链状烷基胺时,层状结构非常明显,而当有机元为带刚性苯... 相似文献
963.
964.
The nickel-aluminum layered double hydroxide (Ni-Al LDH) was synthesized by a simple co-precipitation method and used as a solid-phase extraction (SPE) sorbent for separation and pre-concentration of trace levels of salicylic acid (SA) from aqueous solutions. Extraction of analyte is based on the adsorption of salicylate ions on the Ni-Al (NO3−) LDH and/or their exchanging with LDH interlayer NO3− ions. The retained analyte on the LDH was stripped by 3 mol L−1 NaOH solution and its concentration was subsequently determined spectrofluorometrically at λem = 400 nm with excitation at λex = 270 nm. Various parameters affecting the extraction efficiency of SA on the Ni-Al (NO3−) LDH, such as pH, amount of nano-sorbent, sample loading flow rate, elution conditions, sample volume and matrix effects were investigated. In the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.12 μg L−1 and 40, respectively. The relative standard deviation (RSD) for six replicate determinations of 10 μg L−1 SA was 2.3%. The calibration graph using the pre-concentration system was linear in the range of 0.3-45 μg L−1 with a correlation coefficient of 0.9985. The optimized method was successfully applied to the determination of SA in blood serum, willow leaf and aspirin tablet. 相似文献
965.
Xu J Zhao S Han Z Wang X Song YF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10365-10371
Well-ordered, ultra-thin films (UTFs) based on the hybrid assembly of Na(9)[EuW(10)O(36)]·32H(2)O (denoted as EuW(10)) and exfoliated MgAl layered double hydroxide (LDH) monolayers have been fabricated by utilising a layer-by-layer (LBL) technique. The assembly process was monitored by UV/Vis absorption and fluorescence spectroscopy measurements to get a stepwise and regular growth of the UTFs upon increasing the deposited cycles. In the resulting (EuW(10)/LDH)(n) UTFs, the intercalation of EuW(10) anions into LDH monolayers allows the UTFs to retain their optical properties. Meanwhile, LDH monolayers provide EuW(10) with a confined and protective microenvironment to isolate them from each other between adjacent layers. The UTFs exhibit a periodic, long-range, ordered structure. Anisotropic luminescence spectroscopy measurements show that the (EuW(10)/LDHs)(n) UTFs display well-defined red luminescence with an anisotropy value, r, of about 0.15. Therefore, the cooperative and orientation effects between the host layers and guest anions play significant roles for the improved properties of the (EuW(10)/LDHs)(n) UTFs. This work could benefit the design and fabrication of novel electro-optical devices based on the UTFs of hybrid materials. 相似文献
966.
Sedlmaier SJ Mugnaioli E Oeckler O Kolb U Schnick W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(40):11258-11265
The oxonitridophosphate SrP3N5O has been synthesized by heating a multicomponent reactant mixture that consisted of phosphoryl triamide OP(NH2)3, thiophosphoryl triamide SP(NH2)3, SrS, and NH4Cl enclosed in evacuated and sealed silica‐glass ampoules up to 750 °C. The compound was obtained as nanocrystalline powder with needle‐shaped crystallites. The crystal structure was solved ab initio on the basis of electron diffraction data by means of automated electron diffraction tomography (ADT) and verified by Rietveld refinement with X‐ray powder diffraction data. SrP3N5O crystallizes in the orthorhombic space group Pnma (no. 62) with unit‐cell data of a=18.331(2), b=8.086(1), c=13.851(1) Å and Z=16. The compound is a highly condensed layer phosphate with a degree of condensation κ=1/2. The corrugated layers ${{{\hfill 2\atop \hfill \infty }}}The oxonitridophosphate SrP(3)N(5)O has been synthesized by heating a multicomponent reactant mixture that consisted of phosphoryl triamide OP(NH(2))(3), thiophosphoryl triamide SP(NH(2))(3), SrS, and NH(4)Cl enclosed in evacuated and sealed silica-glass ampoules up to 750 °C. The compound was obtained as nanocrystalline powder with needle-shaped crystallites. The crystal structure was solved ab initio on the basis of electron diffraction data by means of automated electron diffraction tomography (ADT) and verified by Rietveld refinement with X-ray powder diffraction data. SrP(3)N(5)O crystallizes in the orthorhombic space group Pnma (no. 62) with unit-cell data of a=18.331(2), b=8.086(1), c=13.851(1) ? and Z=16. The compound is a highly condensed layer phosphate with a degree of condensation κ=?. The corrugated layers (∞)(2){(P(3)N(5)O)(2-)} consist of linked, triangular columns built up from P(O,N)(4) tetrahedra with 3-rings and triply binding nitrogen atoms. The Sr(2+) ions are located between the layers and exhibit six-, eight-, and ninefold coordination. FTIR and solid-state NMR spectra of SrP(3)N(5)O are discussed as well. 相似文献
967.
968.
网络异构性与传输可靠性是视频通信存在的两大问题.在视频编码中,分层编码用来解决网络传输异构性问题,多描述编码是解决传输可靠性的有效手段,而多描述视频分层编码则是二者的结合.在分层编码技术的基础上,结合基于宏块分裂的多描述编码,提出了基于宏块分裂的多描述视频分层编码.同时,还给出了基于行、列、帧分解的多描述视频分层编码方案,并对4种多描述分层编码方案进行了比较.实验结果表明,所提出的基于宏块分裂多描述分层编码方案在网络异构的适应性和传输可靠性上具有优越性. 相似文献
969.
Lithium-rich layered oxide Li1.2Ni0.16Co0.08Mn0.56O2 can be referred as a crystalline mixture of Li2MnO3 and LiNi0.4Co0.2Mn0.4O2 at equal molar ratio. In the paper, the solid state reaction of M(AC)2·4H2O (M = Mn, Co and Ni) and LiOH·H2O has been performed to obtain nanocrystalline Li1.2Ni0.16Co0.08Mn0.56O2 using a small molecular organic acid (i.e., oxalic acid (OA), citric acid (CA) or tartaric acid (TA)) as additive. The introduction of organic acids can help to improve the layered structure and inhibit the particle growth of Li1.2Ni0.16Co0.08Mn0.56O2, and the different organic acids exert distinct influences on the structural and electrochemical properties of Li1.2Ni0.16Co0.08Mn0.56O2. In detail, the nanoparticles obtained in the presence of OA have the smallest average size of 50–150 nm, which correspondingly exhibit the highest initial discharge capacity of 267.52 mAh g−1 at 0.1C and the best high-rate capability (e.g., 152.22 mAh g−1, 5C) when applied as a lithium ion battery cathode. Furthermore, the active substance obtained from TA shows the best cycling stability and a discharge capacity of 202.42 mAh g−1 can be retained after 50 cycles at 0.5C. 相似文献
970.
The electrical stability of molybdenum disulfide (MoS2) transistors is crucial for their use in various applications. However, it is tricky to evaluate the inherent stability of MoS2 transistors because it is highly dependent on environmental conditions during measurement such as humidity, light, and electrical factors. We studied the threshold voltage instability under negative bias stress at a variety of temperatures in a vacuum and in the dark to eliminate any environmental effects. In particular, the measurement of transfer curves under stress is minimized in order to study the inherent instability of MoS2 transistors, even though the measurement of transfer curves is normally indispensable to check for the evolution of electrical instability. MoS2 transistors have high average effective energy when compared to conventional amorphous Si and oxide semiconductor transistors, which allows for adequate operation at high temperatures. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献