首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1325篇
  免费   120篇
  国内免费   99篇
化学   1017篇
晶体学   12篇
力学   40篇
综合类   7篇
数学   185篇
物理学   283篇
  2023年   23篇
  2022年   20篇
  2021年   31篇
  2020年   46篇
  2019年   51篇
  2018年   40篇
  2017年   36篇
  2016年   56篇
  2015年   55篇
  2014年   53篇
  2013年   73篇
  2012年   112篇
  2011年   96篇
  2010年   75篇
  2009年   57篇
  2008年   78篇
  2007年   64篇
  2006年   70篇
  2005年   70篇
  2004年   52篇
  2003年   43篇
  2002年   53篇
  2001年   53篇
  2000年   39篇
  1999年   27篇
  1998年   12篇
  1997年   18篇
  1996年   28篇
  1995年   14篇
  1994年   14篇
  1993年   6篇
  1992年   12篇
  1991年   14篇
  1990年   10篇
  1989年   9篇
  1988年   9篇
  1987年   2篇
  1986年   5篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有1544条查询结果,搜索用时 15 毫秒
1.
运用密度泛函理论和非平衡格林函数结合的方法,研究电极区N掺杂对扶手椅型石墨烯纳米带电子输运特性的影响.结果表明,与本征扶手椅型石墨烯纳米带电流-电压曲线相比,宽度为7的石墨烯纳米带电流-电压曲线表现出明显的不对称性,其中心N掺杂表现强烈的整流特性,整流系数达到102数量级,且将N原子从电极区中心位置移动到边缘,整流特性减弱.研究结果表明宽度为7的扶手椅型石墨烯纳米带出现强整流现象的原因主要是负向偏压下能量窗内没有透射峰引起的,该研究结果对将来石墨烯整流器件的设计具有重要的意义.  相似文献   
2.
Bu  De-liang  Zhang  San-guo  Li  Na 《应用数学学报(英文版)》2022,38(4):843-860
Acta Mathematicae Applicatae Sinica, English Series - Joint analysis of multiple phenotypes can have better interpretation of complex diseases and increase statistical power to detect more...  相似文献   
3.
An ultrasensitive electrochemical biosensor was fabricated for electroanalytical determination of ascorbic acid(AA), dopamine(DA) and uric acid(UA) individually and simultaneously based on polypyrrole hollow nanotubes loaded with Au and Fe3O4 nanoparticles(NPs) uniformly(PPy@Au-Fe3O4). The PPy@Au-Fe3O4 nanotubes were synthesized in one-pot using MoO3 nanorods as templates and the polymerization of Py, the formation of Au and Fe3O4 NPs and the removel of MoO3 templates took place stimultaneously. Electrochemical studies reveal that PPy@Au-Fe3O4modified glassy carbon electrode(GCE) possesses excellent electro-catalytic activities toward the oxidation of AA, DA and UA. Their oxidation peak currents increase linearly in the concentration ranges of 1-2000 μmol/L for AA, 0.01-25 and 25-300 μmol/L for DA and 0.1-300 μmol/L for UA. Their detection limit values(S/N=3) were calculated as 0.45, 0.0049, and 0.051 μmol/L for AA, DA and UA in the individual detection. By changing the concentrations simultaneously, the calibration curves showed linearity to 1000, 200, and 200 μmol/L with detection limit of 0.39, 0.0060, and 0.060 μmol/L for AA, DA, and UA, respectively. Finally, the obtained biosensor was successfully applied to the detection of AA, DA, and UA with satisfactory results on actual samples.  相似文献   
4.
Photonic materials use photons as information carriers and offer the potential for unprecedented applications in optical and optoelectronic devices. In this study, we introduce a new strategy for photonic materials using metal–organic frameworks (MOFs) as the host for the rational construction of donor–acceptor (D–A) heterostructure crystals. We have engineered a rich library of heterostructure crystals using the MOF NKU‐111 as a host. NKU‐111 is based upon an electron‐deficient tridentate ligand (acceptor) that can bind to various electron‐rich guests (donors). The resulting heterocrystals exhibit spatially segregated multi‐color emission resulting from the guest‐dependent charge‐transfer (CT) emission. Spatially effective mono‐directional energy transfer results from tuning the energy gradient between adjacent domains through the selection of donor guest molecules, which suggests potential applications in integrated optical circuit devices, for example, photonic diodes, on‐chip signal processing, optical logic gates.  相似文献   
5.
A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)2(GA)Pb2I7 (HA=n-hexylammonium, GA=guanidinium). This structure features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non-luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above-band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two-fold higher PL emission compared with the pristine (HA)2(GA)Pb2I7.  相似文献   
6.
Mesoporous core–shell nanostructures with controllable ultra-large open channels in their nanoshells are of great interest. However, soft template-directed cooperative assembly to mesoporous nanoshells with highly accessible pores larger than 30 nm, or even above 50 nm into macroporous range, remains a significant challenge. Herein we report a general approach for precisely tailored coating of hierarchically macro-/mesoporous polymer and carbon shells, possessing highly accessible radial channels with extremely wide pore size distribution from ca. 10 nm to ca. 200 nm, on diverse functional materials. This strategy creates opportunities to tailor the interfacial assembly of irregular mesostructured nanounits on core materials and generate various core–shell nanomaterials with controllable pore architectures. The obtained Fe,N-doped macro-/mesoporous carbon nanoshells show enhanced electrochemical performance for the oxygen reduction reaction in alkaline condition.  相似文献   
7.
基于透明质酸构筑的药物递送载体及其应用   总被引:1,自引:0,他引:1  
刘坤  白阳  杨靖  步怀天 《化学通报》2021,84(3):225-231
传统纳米药物控释载体主要通过细胞胞吞作用实现药物递送,其主要过程为被动靶向机制,因此会影响纳米载体在肿瘤组织的富集和治疗效果。近年来生物大分子透明质酸因其优异的水溶性、生物相容性、可降解性和肿瘤靶向性备受科研工作者青睐,已被广泛用于药物控释载体的构筑中,并成为靶向肿瘤治疗纳米载体领域的研究热点。本文根据透明质酸基纳米载体治疗机制的不同,从透明质酸基纳米载体在化疗、光热治疗、光动力治疗以及联合治疗的应用方面对其性能进行了总结和评述,并在此基础上展望了未来透明质酸基纳米治疗载体的研究方向和发展趋势。  相似文献   
8.
The relay stations play a significant role in long-range charge hopping transfer in proteins. Although studies have clarified that many more protein structural motifs can function as relays in charge hopping transfers by acting as intermediate charge carriers, the relaying properties are still poorly understood. In this work, taking a β-turn oligopeptide as an example, we report a dynamic character of a relay with tunable relaying properties using the density functional theory calculations. Our main finding is that a β-turn peptide can serve as an effective electron relay in facilitating long-range electron migration and its relay properties is vibration-tunable. The vibration-induced structural transient distortions remarkably affect the lowest occupied molecular orbital (LUMO) energy, vertical electron affinity and electron-binding mode of the β-turn oligopeptide and the singly occupied molecular orbital (SOMO) energy of the corresponding electron adduct and thus the relaying properties. Different vibration modes lead to different structural distortions and thus have different effects on the relaying properties and ability of the β-turn peptide. For the relaying properties, there approximately is a linear negative correlation of electron affinity with the LUMO energy of the β-turn or the SOMO energy of its electron adduct. Besides, such relaying properties also vary in the vibration evolution process, and the electron-binding modes may be tunable. As an important addition to the known static charge relaying properties occurring in various protein structural motifs, this work reports the dynamic electron-relaying characteristics of a β-turn oligopeptide with variable relaying properties governed by molecular vibrations which can be applied to different proteins in mediating long-range charge transfers. Clearly, this work reveals molecular vibration effects on the electron relaying properties of protein structural motifs and provides new insights into the dynamics of long-range charge transfers in proteins. © 2018 Wiley Periodicals, Inc.  相似文献   
9.
Redox homeostasis is one of the main reasons for reactive oxygen species (ROS) tolerance in hypoxic tumors, limiting ROS-mediated tumor therapy. Proposed herein is a redox dyshomeostasis (RDH) strategy based on a nanoplatform, FeCysPW@ZIF-82@CAT Dz, to disrupt redox homeostasis, and its application to improve ROS-mediated hypoxic tumor therapy. Once endocytosed by tumor cells, the catalase DNAzyme (CAT Dz) loaded zeolitic imidazole framework-82 (ZIF-82@CAT Dz) shell can be degraded into Zn2+ as cofactors for CAT Dz mediated CAT silencing and electrophilic ligands for glutathione (GSH) depletion under hypoxia, both of which lead to intracellular RDH and H2O2 accumulation. These “disordered” cells show reduced resistance to ROS and are effectively killed by ferrous cysteine-phosphotungstate (FeCysPW) induced chemodynamic therapy (CDT). In vitro and in vivo data demonstrate that the pH/hypoxia/H2O2 triple stimuli responsive nanocomposite can efficiently kill hypoxic tumors. Overall, the RDH strategy provides a new way of thinking about ROS-mediated treatment of hypoxic tumors.  相似文献   
10.
A novel nanostructured copper‐based solid‐phase microextraction fiber was developed and applied for determining the two most common types of phthalate environmental estrogens (dibutyl phthalate and diethylhexyl phthalate) in aqueous samples, coupled to gas chromatography with flame ionization detection. The copper film was coated onto a stainless‐steel wire via an electroless plating process, which involved a surface activation process to improve the surface properties of the fiber. Several parameters affecting extraction efficiency such as extraction time, extraction temperature, ionic strength, desorption temperature, and desorption time were optimized by a factor‐by‐factor procedure to obtain the highest extraction efficiency. The as‐established method showed wide linear ranges (0.05–250 μg/L). Precision of single fiber repeatability was <7.0%, and fiber‐to‐fiber repeatability was <10%. Limits of detection were 0.01 μg/L. The proposed method exhibited better or comparable extraction performance compared with commercial and other lab‐made fibers, and excellent thermal stability and durability. The proposed method was applied successfully for the determination of model analytes in plastic soaking water.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号