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1.
The surface charge is a key concept in electrochemistry. Mathematically, the surface charge is obtained from a spatial integration of the volume charge along a particular direction. Ambiguities thus arise in choosing the starting and ending points of the integration. As for electrocatalytic interfaces, the presence of chemisorbates further complicates the situation. In this minireview, I adopt a definition of the surface charge within a continuum picture of the electric double layer. I will introduce surface charging behaviors of firstly ordinary electrochemical interfaces and then electrocatalytic interfaces featuring partially charged chemisorbates. Particularly, the origin of nonmonotonic surface charging behaviors of electrocatalytic interfaces is explained using a primitive model. Finally, a brief account of previous studies on the nonmonotonic surface charging behavior is presented, as a subline of the spectacular history of electric double layer. 相似文献
2.
Liuhua Xie 《中国物理 B》2022,31(6):67103-067103
The effect of strain on charge density wave (CDW) order in $\alpha$-U is investigated within the framework of relativistic density-functional theory. The energetical stability of $\alpha$-U with CDW distortion is enhanced by the tensile strain along $a$ and $b$ axes, which is similar to the case of negative pressure and normal. However, the tensile strain along $c$ axis suppresses the energetical stability of CDW phase. This abnormal effect could be understood from the emergence of a new one-dimensional atomic chain along $c$ axis in $\alpha$-U. Furthermore, this effect is supported by the calculations of Fermi surface and phonon mode, in which the topological objects and the dynamical instability show opposite behaviors between strains along $a$/$b$ and $c$ axes. 相似文献
3.
A general framework for describing photofission observables of actinides at an average excitation energy below 30 MeV 下载免费PDF全文
Guan-Lin Wang Hao-Yang Lan Xiao-Ming Shi Zhi-Chao Zhu Wen Luo 《中国物理C(英文版)》2022,46(8):084102-084102-14
A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications, such as short-lived isotope production, nuclear waste disposal, and nuclear safeguards. However, the available experimental data for photofission observables are limited, and the existing models and programs have mainly been developed for neutron-induced fission processes. In this study, a general framework is proposed for characterizing the photofission observables of actinides, including the mass yield distributions (MYD) and isobaric charge distributions (ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons (np) and prompt γ rays (γp). The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input. These models are then validated individually against experimental data at an average excitation energy below 30 MeV, which shows the reliability and robustness of the general framework. Finally, we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including 232Th, 235, 238U and 240Pu. It is found that the 238U(γ, f) reaction is more suitable for producing neutron-rich nuclei compared to the 232Th(γ, f) reaction. In addition, the average multiplicity number of both np and γp increases with the average excitation energy. 相似文献
4.
5.
Atsunobu Akita Emeritus Prof. Hisayoshi Kobayashi Prof. Dr. Hiroaki Tada 《Chemphyschem》2019,20(16):2054-2059
The development of nanostructured semiconductor electrodes represented by a mesoporous TiO2 nanocrystalline (mp-TiO2) film is currently bringing great progresses in photoelectrochemical (PEC) devices for solar-to-electricity and solar-to-chemical conversion. Two serious losses can occur in PEC devices: 1) recombination between the conduction band (CB) electrons and valence band (VB) holes in the bulk and at the surface and 2) back reaction or electron trapping by oxidant in the electrolyte solution during transport to the electron-collecting electrode. Thus, the major challenge in common with the nanostructured semiconductor photoanodes is to achieve efficient charge separation and electron transport. In this study, an ultrathin SiOx layer was formed on both the external and the internal surface of mp-TiO2 using an original chemisorption-calcination technique employing 1,3,5,7-tetramethyltetrasiloxane as a starting material. The SiOx surface modification of the mp-TiO2 photoanode drastically prolongs the mean lifetime of CB-electrons in TiO2 because of enhanced charge separation and electron transport by the negative charge applied in aqueous electrolyte solution. We have demonstrated that the performance of a one-compartment H2O2-photofuel cell using mp-TiO2 as the photoanode is greatly boosted by the surface modification with the SiOx layer. We anticipate that this methodology is widely applicable to nanostructured metal oxide semiconductor electrodes, contributing to the improvement in the performance of PEC devices. 相似文献
6.
Anodic stripping voltammetry was made in AgNO3 solution, here Ag was deposited under long term potentiostatic conditions to evaluate the reduction charge, qr, and then was stripped by linear sweep voltammetry to determine the oxidation charge, qo. The charges were unbalanced, satisfying ca. qo=0.7|qr|, where other possible reduction charge such as by dioxygen and dichlorosilver were subtracted. The 30 % loss of the anodic charge can be ascribed to the negative capacitance by the potential sweep generation of Ag+. The generated Ag+ forms a dipole with a counter ion, of which orientation is the same as the direction of the externally applied electric field and opposite to the dipoles of solvent. The redox dipole decreases the conventional double layer capacitance caused by solvent dipoles, and high concentrations of Ag+ takes the capacitance to be negative values. The unbalanced charge, however, has no influence on quantitative determination of concentrations Ag+ by use of a calibration line. 相似文献
7.
为了从物质微观结构上了解氧化锌避雷器阀片的性能,采用基于密度泛函理论的第一性原理方法对ZnO(002)/β-Bi_2O_3(210)界面结构进行弛豫和电子结构计算.结果表明弛豫后,原子间的键长发生改变.界面区域差分电荷密度图和原子布居分析可得ZnO层片中Zn原子电荷缺失,β-Bi_2O_3层片中O原子电荷富集,ZnO层片向β-Bi_2O_3层片转移电子电荷23.61e.晶界结构的内建电场由ZnO层片指向β-Bi_2O_3层片,内建电场是ZnO电阻阀片具有非线性伏安特性的重要原因.界面附近态密度表明界面的结合主要依靠ZnO层片中Zn原子与β-Bi_2O_3层片中O原子相互作用.计算显示ZnO(002)/β-Bi_2O_3(210)界面结合较强,界面能约为-4.203 J/m~2.本文研究结果对于研制高性能非线性伏安特性氧化锌电阻片提供了机理解释和理论支持. 相似文献
8.
Durairaj Gopalakrishnan Santhanam Srinath Baburaj Baskar Nattamai S.P. Bhuvanesh Mani Ganeshpandian 《应用有机金属化学》2019,33(3)
Two organometallic Ru(II)‐p‐cymene complexes of the type [Ru(η6‐p‐cymene)(L)Cl]PF6 1 and 2 , where L is N,N‐bis(4‐isopropylbenzylidene)ethane‐1,2‐diamine (bien, L1 ) or N,N‐bis (pyren‐2‐ylmethylene)ethane‐1,2‐diamine (bpen, L2 ) have been prepared and characterized well. Because of appended pyrenyl groups in coordinated bpen ligand, the complex 2 exhibits higher DNA and protein binding than complex 1 in which isopropylbenzyl groups are incorporated. Interestingly, the luminescent characteristic complex 2 is unique in displaying DNA cleavage after light activation by UVA light at 365 nm through oxygen dependent mechanism. AFM analysis attests the photo‐induced DNA fragmentation ability of complex 2 . Also, the complex 2 cleaves the protein after light exposure in a non‐specific manner suggesting that it can act as a protein photo cleaving agent. In contrast to the trend of DNA and protein interaction of complexes, the complex 1 exhibits cytotoxic activity against human breast carcinoma ( MCF‐7 ) and liver carcinoma ( HepG2 ) with potency higher than that of complex 2 due to enhanced hydrophobicity of isopropyl groups present in p‐cymene and bien ligands. Indeed, complex 2 is inactive against MCF‐7 and HepG2 cancer cell lines even up to 200 μM concentration. The AO/EB staining assay reveals that the complex 1 is able to induce late apoptotic mode of cell death in breast cancer cells, which is further confirmed by inter‐nucleosomal DNA cleavage. Furthermore, the complexes 1 and 2 are evaluated for their catalytic activities and found to be working well for the β‐carboline directed C–H arylation to afford the desired products in good yield (40–47%). 相似文献
9.
Due to the difficulty in achieving high efficiency and high color purity simultaneously, blue emission is the limiting factor for the performance and stability of OLEDs. Since 2003, we have been working on organic light‐emitting diodes (OLEDs), especially on blue light. After a series of molecular designs, novel strategies have been proposed from different aspects. At first, highly efficient deep blue emission could be achieved through molecular design with highly twisted structure to suppress fluorescence quenching and redshift. Deep blue emitters with high efficiency in solid state, a twisted structure with aggregation induced emission (AIE) characteristics was incorporated to inhibit molecular aggregation, and triplet‐triplet fusion (TTF) and hybridized localized charge transfer (HLCT) were adopted to increase the ratio of triplet exciton used. Secondly, a highly efficient blue OLED could be achieved through improving charge transport. New electron transport materials (ETMs) with wide band gap were developed to control charge transport balance in devices. Thirdly, a highly efficient deep blue emission could be achieved through a mesoscopic structure of out‐coupling layer. A mesoscopic photonic structured organic thin film was fabricated on the top of metal electrode by self‐aggregation in order to improve the light out‐coupling efficiency. 相似文献
10.
Magdalena Obłoza Dr. Łukasz Łapok Dr. Tomasz Pędziński Prof. Katarzyna M. Stadnicka Prof. Maria Nowakowska 《Chemphyschem》2019,20(19):2482-2497
A series of novel aza-BODIPY dyes substituted with p-(dimethylamino)phenyl groups were synthesized and their spectral and electrochemical properties were compared. In particular, the impact of p-(Me2N)Ph- groups on these characteristics was of consideration. For two aza-BODIPYs studied, a near-IR absorption band was observed at circa λabs=796 nm. Due to the pronounced intramolecular charge transfer (ICT) exerted by the presence of strongly electron-donating p-(Me2N)Ph- substituents, the compounds studied were weakly emissive with the singlet lifetimes (τS) in the picosecond range. Nanosecond laser photolysis experiments of the brominated aza-BODIPYs revealed T1→Tn absorption spanning from ca. 350 nm to ca. 550 nm with the triplet lifetimes (τT) ranged between 6.0 μs and 8.5 μs. The optical properties of the aza-BODIPYs studied were pH-sensitive. Upon protonation of the dimethylamino groups with trifluoroacetic acid in toluene, a stepwise disappearance of the NIR absorption band at λabs=790 nm was observed with the concomitant appearance of a blue-shifted absorption band at λabs=652 nm, which was accompanied by a prominent emission band at λfl=680 nm. The transformation from a non-emissive to an emissive compound is associated with the inhibition of the ICT. As estimated by CV/DPV measurements, all aza-BODIPYs studied exhibited two irreversible oxidation and two quasi-reversible reduction processes. All compounds studied exhibit extremely high photostability and thermal stability. 相似文献