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891.
892.
用分子光谱法研究了甲基-β-环糊精(M-CD)和羟丙基-β-环糊精(HP-CD)与4-(N,N-二甲氨基)-苯甲酸-2′-乙基己基酯(EHDAB)分子间的包结作用.结果表明,柔性的2′-乙基己基和刚性的芳香端都包结在M-CD和HP-CD空腔中,形成了2∶1笼型主-客体包结物.疏水性2′-乙基己基在包结物的热力学稳定性中起重要作用,亲水性M-CD和HP-CD将EHDAB增溶在水中,提高了EHDAB分子的紫外吸收程度,M-CD和HP-CD空腔抑制了光诱导EHDAB分子内扭转电荷转移,显著提高了EHDAB的光化学稳定性,增强了其抗氧化性,降低了酸碱性水解程度,包结物的热稳定性与所用主体环糊精相当. 相似文献
893.
894.
Xibao Li Jiyou Liu Juntong Huang Chaozheng He Zhijun Feng Zhi Chen Liying Wan Fang Deng 《物理化学学报》1985,37(6):2010030-0
Organic photocatalysts have attracted attention owing to their suitable redox band positions, low cost, high chemical stability, and good tunability of their framework and electronic structure. As a novel organic photocatalyst, PDI-Ala (N, N'-bis(propionic acid)-perylene-3, 4, 9, 10-tetracarboxylic diimide) has strong visible-light response, low valence band position, and strong oxidation ability. However, the low photogenerated charge transfer rate and high carrier recombination rate limit its application. Due to the aromatic heterocyclic structure of g-C3N4 and large delocalized π bond in the planar structure of PDI-Ala, g-C3N4 and PDI-Ala can be tightly combined through π–π interactions and N―C bond. The band structure of sulfur-doped g-C3N4 (S-C3N4) matched well with PDI-Ala than that with g-C3N4. The electron delocalization effect, internal electric field, and newly formed chemical bond jointly promote the separation and migration of photogenerated carriers between PDI-Ala and S-C3N4. To this end, a novel step-scheme (S-scheme) heterojunction photocatalyst comprising organic semiconductor PDI-Ala and S-C3N4 was prepared by an in situ self-assembly strategy. Meanwhile, PDI-Ala was self-assembled by transverse hydrogen bonding and longitudinal π–π stacking. The crystal structure, morphology, valency, optical properties, stability, and energy band structure of the PDI-Ala/S-C3N4 photocatalysts were systematically analyzed and studied by various characterization methods such as X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, ultraviolet visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, and Mott-Schottky curve. The work functions and interface coupling characteristics were determined using density functional theory. The photocatalytic activities of the synthesized photocatalyst for H2O2 production and the degradation of tetracycline (TC) and p-nitrophenol (PNP) under visible-light irradiation are discussed. The PDI-Ala/S-C3N4 S-scheme heterojunction with band matching and tight interface bonding accelerates the intermolecular electron transfer and broadens the visible-light response range of the heterojunction. In addition, in the processes of the PDI-Ala/S-C3N4 photocatalytic degradation reaction, a variety of active species (h+, ·O2-, and H2O2) were produced and accumulated. Therefore, the PDI-Ala/S-C3N4 heterojunction exhibited enhanced photocatalytic performance in the degradation of TC, PNP, and H2O2 production. Under visible-light irradiation, the optimum 30%PDI-Ala/S-C3N4 removed 90% of TC within 90 min. In addition, 30%PDI-Ala/S-C3N4 displayed the highest H2O2 evolution rate of 28.3 μmol·h-1·g-1, which was 2.9 and 1.6 times higher than those of PDI-Ala and S-C3N4, respectively. These results reveal that the all organic photocatalyst comprising PDI-based supramolecular and S-C3N4 can be efficiently applied for the degradation of organic pollutants and production of H2O2. This work not only provides a novel strategy for the design of all organic S-scheme heterojunctions but also provides a new insight and reference for understanding the structure–activity relationship of heterostructure catalysts with effective interface bonding.
相似文献
895.
Sustainable photocatalytic H2 evolution has attracted extensive attention in recent years because it can address both energy shortage and environmental pollution issues. In particular, metal sulfide solid-solution photocatalysts have been widely applied in photocatalytic hydrogen generation owing to their excellent light harvesting properties, narrow enough band gap, and suitable redox potentials of conduction and valance bands. However, it is still challenging to develop low-cost and high-efficiency sulfide solid-solution photocatalysts for practical photocatalytic hydrogen evolution. Recently, 1D MnxCd1-xS nanostructures have shown superior light absorption, charge separation, and H2-evolution activity owing to their shortened diffusion pathway of carriers and high length-to-diameter ratios. Thus, 1D MnxCd1-xS nanostructures have been applied in photocatalytic H2 evolution. However, a single MnxCd1-xS photocatalyst still has some disadvantages for photocatalytic H2 evolution, such as the rapid recombination of photogenerated electron-hole pairs and low quantum efficiency. Herein, to further boost the separation of photogenerated charge carriers and H2-evolution kinetics, an in situ solvothermal method was used to synthesize the 1D/2D Schottky-based heterojunctions between the Mn0.2Cd0.8S nanorods (MCS NRs) and Ti3C2 MXene nanosheets (NSs). Furthermore, various characterization methods have been used to investigate the crucial roles and underlying mechanisms of metallic Ti3C2 MXene NSs in boosting the photocatalytic H2 evolution over the Mn0.2Cd0.8S nanorods. X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscopy (HRTEM), element mapping images, and X-ray Photoelectron Spectroscopy (XPS) results clearly demonstrate that hybrid low-cost Schottky-based heterojunctions have been successfully constructed for practical applications in photocatalytic H2 evolution. Additionally, the photocatalytic hydrogen evolution reaction (HER) was also carried out in a mixed solution of Na2SO3 and Na2S using as the sacrificial agents. The highest hydrogen evolution rate of the optimized 1D/2D Schottky-based heterojunction is 15.73 mmol·g-1·h-1, which is 6.72 times higher than that of pure MCS NRs (2.34 mmol·g-1·h-1). An apparent quantum efficiency of 19.6% was achieved at 420 nm. The stability measurements of the binary photocatalysts confirmed their excellent photocatalytic stability for practical applications. More interestingly, the UV-Vis diffuse reflection spectra, photoluminescence (PL) spectrum, transient photocurrent responses, and Electrochemical Impedance Spectroscopy (EIS) Nyquist plots clearly confirmed the promoted charge separation between the MCS NRs and Ti3C2 MXene NSs. The linear sweep voltammetry also showed that the loading of MXene cocatalysts could greatly decrease the overpotential of pure MCS NRs, suggesting that the 2D Ti3C2 NSs could act as an electronic conductive bridge to improve the H2-evolution kinetics. In summary, these results show that the 2D/1D hybrid Schottky-based heterojunctions between metallic Ti3C2 MXene NSs and MCS NRs can not only improve the separation of photogenerated electrons and holes but also decrease the H2-evolution overpotential, thus resulting in significantly enhanced photocatalytic H2 generation. We believe that this study will inspire new ideas for constructing low-cost Schottky-based heterojunctions for practical applications in photocatalytic H2 evolution.
相似文献
896.
在用阳极氧化法制备有序排列TiO2纳米管阵列薄膜的基础上,引入脉冲沉积工艺,成功实现了均匀、弥散分布的Cu2O纳米颗粒修饰改性TiO2纳米管阵列,形成Cu2O/TiO2 纳米管异质结复合材料. 利用场发射扫描电镜(FESEM)、场发射透射电镜(FETEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis DRS)对样品进行表征,重点研究了Cu2O/TiO2 纳米管异质结的光电化学特性和对甲基橙(MO)的可见光催化降解性能. 结果表明,Cu2O纳米颗粒均匀附着在TiO2纳米管阵列的管口和中部位置,所制备的Cu2O/TiO2 纳米管异质结具有高效的可见光光催化性能;在浓度为0.01 mol·L-1的CuSO4溶液中制得的Cu2O/TiO2纳米管异质结表现出最好的电化学特性和光催化性能;另外,对Cu2O纳米颗粒影响光催化活性的机理进行了讨论. 相似文献
897.
898.
两块超导体,中间用极薄的氧化层(绝缘层)隔开,便构成了所谓的“超导隧道结”.按照量子物理,超导库珀对应该有机会穿透氧化层的壁垒.这样,绝缘层看起来也是超导的——虽然有电流流过,但在绝缘层的两端却测不到电压.1962年,年仅22岁的英国剑桥大学研究生约瑟夫森(B.D.Josephson),通过认真的理论推演,预言了上述隧道效应的存在.在以后的数年中,这个预言连同一系列相关的预言(统称为约瑟夫森效应),作为量子力学在宏观世界同样适用的例证,均在实验中被证实,约瑟夫森因此获得了1973年度诺贝尔物理奖. 相似文献
899.
水产品的新鲜度极大地影响着人类的生命及身体健康,水产品在存放过程中会释放出以三甲胺为代表的胺类气体,通过检测这类气体的浓度可以监控水产品的新鲜度.本文以具有优良气体敏感性能的MoO3纳米带作为基体,通过引入Cu3Mo2O9纳米颗粒制备Cu3Mo2O9/MoO3复合材料,具有非常好的三甲胺气体敏感性能、快速响应/恢复时间及长期稳定性.结果表明,采用这种复合材料制备的气敏元件在50—240℃,质量分数为5×10-6时对三甲胺气体的响应可达到Rair/Rgas=13.9,最小检测极限的体积分数为2×10-7.分布在MoO3纳米带表面的Cu3Mo2O9颗粒与基体形成异质结界面,利用Cu3Mo2O... 相似文献
900.
以自组装SiO2纳米球为模板,通过煅烧和模板刻蚀制备具有三维有序大孔结构的TiO2/CeO2复合光催化剂(3DOM TiO2/CeO2).用XRD、SEM、FT-IR、DRS、PC等手段对所制备的光催化剂进行表征,在模拟太阳光下,以罗丹明B为模型降解物,对样品的光催化活性进行测试.结果表明,3DOM TiO2/CeO2的光催化降解活性与TiO2/CeO2相比得到进一步提高,其原因可能是由于3DOM结构可以产生慢光子效应,提高了TiO2/CeO2复合光催化剂的光吸收能力,进而提高了TiO2/CeO2的光催化性能. 相似文献