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971.
ZHANG Jing-Bo LI Pan YANG Hui ZHAO Fei-Yan TANG Guang-Shi SUN Li-Na LIN Yuan 《物理化学学报》2014,30(8):1495-1500
为了提高量子点敏化纳晶薄膜太阳能电池的光电转换效率,我们通过连续在酸和多硫溶液中处理铅片制备了对多硫电解液具有高电催化活性的硫化铅电极.通过电化学阻抗谱测试评价所制备硫化铅电极的催化活性,从而确定制备高效硫化铅电极的最佳条件.以在最佳条件下制备的硫化铅为对电极、CdSe量子点敏化TiO2纳晶薄膜为工作电极和多硫电解液组装成量子点敏化太阳能电池.光电性能测试结果表明所制备的电极具有良好的催化活性和光电转换性能.与已报导的方法相比,新方法大幅度地减少制备过程所需的时间,但却提高了所制备的硫化铅对电极的催化活性.通过X射线衍射和扫描电镜测试表征了硫化铅的生成过程,探讨了催化活性提高的原因. 相似文献
972.
Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature 下载免费PDF全文
Dr. Kui Yu Dr. Xiangyang Liu Queena Y. Chen Prof. Huaqing Yang Prof. Mingli Yang Xinqin Wang Prof. Xin Wang Dr. Hong Cao Dr. Dennis M. Whitfield Prof. Changwei Hu Dr. Ye Tao 《Angewandte Chemie (International ed. in English)》2014,53(27):6898-6904
Primary alkyl amines (RNH2) have been empirically used to engineer various colloidal semiconductor nanocrystals (NCs). Here, we present a general mechanism in which the amine acts as a hydrogen/proton donor in the precursor conversion to nanocrystals at low temperature, which was assisted by the presence of a secondary phosphine. Our findings introduce the strategy of using a secondary phosphine together with a primary amine as new routes to prepare high‐quality NCs at low reaction temperatures but with high particle yields and reproducibility and thus, potentially, low production costs. 相似文献
973.
Sharmistha Karmakar Dr. Ayan Datta 《Angewandte Chemie (International ed. in English)》2014,53(36):9587-9591
At room temperature, 1,2‐hydrogen‐transfer reactions of N‐heterocyclic carbenes, like the imidazol‐2‐ylidene to give imidazole is shown to occurr almost entirely (>90 %) by quantum mechanical tunneling (QMT). At 60 K in an Ar matrix, for the 2, 3‐dihydrothiazol‐2‐ylidene→thiazole transformation, QMT is shown to increase the rate about 105 times. Calculations including small‐curvature tunneling show that the barrier for intermolecular 1,2‐hydrogen‐transfer reaction is small, and QMT leads to a reduced rate of the forward reaction because of nonclassical reflections even at room temperature. A small barrier also leads to smaller kinetic isotope effects because of efficient QMT by both H and D. QMT does not always lead to faster reactions or larger KIE values, particularly when the barrier is small. 相似文献
974.
Dr. Masaki Yoshida Dr. Mio Kondo Prof. Toshikazu Nakamura Prof. Ken Sakai Prof. Shigeyuki Masaoka 《Angewandte Chemie (International ed. in English)》2014,53(43):11519-11523
A series of [{(terpy)(bpy)Ru}(μ‐O){Ru(bpy)(terpy)}]n+ ( [RuORu]n+ , terpy=2,2′;6′,2′′‐terpyridine, bpy=2,2′‐bipyridine) was systematically synthesized and characterized in three distinct redox states (n=3, 4, and 5 for RuII,III2 , RuIII,III2 , and RuIII,IV2 , respectively). The crystal structures of [RuORu]n+ (n=3, 4, 5) in all three redox states were successfully determined. X‐ray crystallography showed that the Ru? O distances and the Ru‐O‐Ru angles are mainly regulated by the oxidation states of the ruthenium centers. X‐ray crystallography and ESR spectra clearly revealed the detailed electronic structures of two mixed‐valence complexes, [RuIIIORuIV]5+ and [RuIIORuIII]3+ , in which each unpaired electron is completely delocalized across the oxo‐bridged dinuclear core. These findings allow us to understand the systematic changes in structure and electronic state that accompany the changes in the redox state. 相似文献
975.
Christian B. Winiger Dr. Shaoguang Li Dr. Ganesh R. Kumar Dr. Simon M. Langenegger Prof. Dr. Robert Häner 《Angewandte Chemie (International ed. in English)》2014,53(49):13609-13613
The efficient collection of solar energy relies on the design and construction of well‐organized light‐harvesting systems. Herein we report that supramolecular phenanthrene polymers doped with pyrene are effective collectors of light energy. The linear polymers are formed through the assembly of short amphiphilic oligomers in water. Absorption of light by phenanthrene residues is followed by electronic energy transfer along the polymer over long distances (>100 nm) to the accepting pyrene molecules. The high efficiency of the energy transfer, which is documented by large fluorescence quantum yields, suggests a quantum coherent process. 相似文献
976.
Nature’s Chemical Signatures in Human Olfaction: A Foodborne Perspective for Future Biotechnology 下载免费PDF全文
Andreas Dunkel Martin Steinhaus Matthias Kotthoff Bettina Nowak Dietmar Krautwurst Peter Schieberle Thomas Hofmann 《Angewandte Chemie (International ed. in English)》2014,53(28):7124-7143
The biocatalytic production of flavor naturals that determine chemosensory percepts of foods and beverages is an ever challenging target for academic and industrial research. Advances in chemical trace analysis and post‐genomic progress at the chemistry–biology interface revealed odor qualities of nature’s chemosensory entities to be defined by odorant‐induced olfactory receptor activity patterns. Beyond traditional views, this review and meta‐analysis now shows characteristic ratios of only about 3 to 40 genuine key odorants for each food, from a group of about 230 out of circa 10 000 food volatiles. This suggests the foodborn stimulus space has co‐evolved with, and roughly match our circa 400 olfactory receptors as best natural agonists. This perspective gives insight into nature’s chemical signatures of smell, provides the chemical odor codes of more than 220 food samples, and beyond addresses industrial implications for producing recombinants that fully reconstruct the natural odor signatures for use in flavors and fragrances, fully immersive interactive virtual environments, or humanoid bioelectronic noses. 相似文献
977.
Meilian Zhao Feng Yang Prof. Ying Xue Prof. Dan Xiao Prof. Yong Guo 《Chemphyschem》2014,15(1):157-164
A comprehensive first‐principles theoretical study of the electronic properties and half‐metallic nature of zigzag edge‐oxidized graphene quantum dots (GQDs) is carried out by using density functional theory (DFT) with the screened exchange hybrid functional of Heyd, Scuseria and Ernzerhof (HSE06). The oxidation schemes include ‐OH, ‐COOH and ‐COO groups. We identify oxidized GQDs whose opposite spins are localized at the two zigzag edges in an antiferromagnetic‐type configuration, showing a spin‐polarized ground state. Oxidized GQDs are more stable than the corresponding fully hydrogenated GQDs. The partially hydroxylated and carboxylated GQDs with the same size exhibit half‐metallic state under almost the same electric‐field intensity whereas fully oxidized GQDs behave as spin‐selective semiconductors. The electric‐field intensity inducing the half metal increases with the length of the partially oxidized GQDs, ranging from M=4 to 7. 相似文献
978.
Experimental and Theoretical Investigation of the First‐Order Hyperpolarizability of Octupolar Merocyanine Dyes 下载免费PDF全文
Dr. Frédéric Castet Dr. Mireille Blanchard‐Desce Frédéric Adamietz Yevgen M. Poronik Prof. Dr. Daniel T. Gryko Prof. Dr. Vincent Rodriguez 《Chemphyschem》2014,15(12):2575-2581
Hyper‐Rayleigh scattering experiments and quantum chemical calculations are combined to investigate the second‐order nonlinear optical responses of a series of three‐arm merocyanine derivatives. They exhibit an octupolar hyperpolarizability response with lower amplitude than crystal violet due to a lower extent of the photoinduced charge transfer and reduced bond length alternation. Strong effects on the second‐order optical response measured close to the two‐photon absorption level are clearly evidenced; for example, the effective measured polarization ratio deviates below the ideal octupolar value of 3/2 even at very low excitation power. These effects are attributed to two‐photon absorption resonance, which we believe modifies dynamically the population of the ground state versus that of the excited state. 相似文献
979.
Chong Zhao Dan Lei Prof. Li‐Hua Gan Dr. Zhu‐Xia Zhang Prof. Chun‐Ru Wang 《Chemphyschem》2014,15(13):2780-2784
Sc2S@C84 has recently been detected but not structurally characterized. 1 Density functional theory calculations on C84 and Sc2S@C84 show that the favored isomer of Sc2S@C84 shares the same parent cage as Sc2C2@C84, whereas Sc2S@C84:51383, which violates the isolated‐pentagon rule, is the second lowest energy isomer with the widest HOMO–LUMO gap and shows high kinetic stability. The analysis shows that Sc2S@C84:51575 is favored when the temperature exceeds 2 800 K and it can transform into the most favorable isomer Sc2S@C84:51591. Molecular orbital analysis indicates that both Sc2S and Sc2C2 formally transfer four electrons to the cage, and quantum theory of atoms in molecules analysis demonstrates that there is a covalent interaction between Sc2S and C84:51591. The IR spectra of Sc2S@C84 are provided to aid future structural identification. 相似文献
980.
采用高温固相合成法制备了Er3+,Yb3+双掺杂的GdOCl荧光材料,并研究其荧光性能。该双掺杂体系荧光粉吸收紫外光,发出红色(619 nm)和近红外(~979 nm)荧光。在这些荧光材料中,1个Er3+离子可以有效将其能量转移给2个Yb3+离子。通过改变Yb3+掺杂浓度,对比Gd0.998 5-yOCl∶0.0015Er3+,yYb3+中的Er3+的发射光谱和不同检测波长的荧光寿命变化特点,对Er3+-Yb3+发生量子剪裁的能级进行分析和指认,并计算了能量转化效率(η)和量子效率(Q)。正是由于具备这种荧光性能,该荧光材料体系有望在荧光太阳能收集器以及军事和医学的红外显示和探测技术中获得应用。 相似文献