全文获取类型
收费全文 | 3351篇 |
免费 | 609篇 |
国内免费 | 217篇 |
专业分类
化学 | 1026篇 |
晶体学 | 28篇 |
力学 | 38篇 |
综合类 | 7篇 |
数学 | 35篇 |
物理学 | 1073篇 |
无线电 | 1970篇 |
出版年
2024年 | 24篇 |
2023年 | 110篇 |
2022年 | 70篇 |
2021年 | 179篇 |
2020年 | 170篇 |
2019年 | 119篇 |
2018年 | 103篇 |
2017年 | 141篇 |
2016年 | 181篇 |
2015年 | 165篇 |
2014年 | 251篇 |
2013年 | 228篇 |
2012年 | 245篇 |
2011年 | 237篇 |
2010年 | 151篇 |
2009年 | 204篇 |
2008年 | 238篇 |
2007年 | 215篇 |
2006年 | 187篇 |
2005年 | 159篇 |
2004年 | 109篇 |
2003年 | 119篇 |
2002年 | 86篇 |
2001年 | 63篇 |
2000年 | 77篇 |
1999年 | 49篇 |
1998年 | 54篇 |
1997年 | 27篇 |
1996年 | 38篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有4177条查询结果,搜索用时 0 毫秒
31.
Dimitra Papadimitriou Efthymios Liarokapis Wolfgang Richter 《Mikrochimica acta》2001,136(3-4):165-169
Strain effects on semiconductor layers were studied by means of optical spectroscopic techniques with a device developed
especially for the study of layered structures and microstructures. Raman, modulated photoreflectance and reflectance anisotropy
spectroscopy (RAS) were applied. Measurements were performed on elemental semiconductors (Si), semiconductor alloys (Si–Ge)
and III–V semiconductor compounds (GaAs). By application of RAS, strains lower than 10−4 could be resolved, which is at least one order of magnitude lower than those observable with Raman and modulated reflectance
techniques. The RAS spectra of layers strained along either the [010] or [011] direction showed a derivative-like structure
at E1-gap energies, which increased linearly and very quickly with increasing strain. The dependence of this spectral feature on
applied strain was used to evaluate strain-dependent effects. This behaviour strongly suggests that RAS can be applied for
the optical characterisation of strain in semiconductor microstructures and devices, with a higher efficiency and accuracy
than that achieved by previously established optical methods such as Raman and modulation spectroscopy. In addition, the compactness
and ease of operation of the instrumentation of RAS provides considerable potential for in situ monitoring/control of semiconductor fabrication conditions. 相似文献
32.
《Journal of separation science》2018,41(9):2085-2091
Isoelectric focusing plays a critical role in the analysis of complex protein samples. Conventionally, isoelectric focusing is implemented with carrier ampholytes in capillary or immobilized pH gradient gel. In this study, we successfully exhibited a carrier ampholyte‐free isoelectric focusing on paper‐based analytical device. Proof of the concept was visually demonstrated with color model proteins. Experimental results showed that not only a pH gradient was well established along the open paper fluidic channel as confirmed by pH indicator strip, the pH gradient range could also be tuned by the catholyte or anolyte. Furthermore, the isoelectric focusing fractions from the paper channel can be directly cut and recovered into solutions for post analysis with sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry. This paper‐based isoelectric focusing method is fast, cheap, simple and easy to operate, and could potentially be used as a cost‐effective protein sample clean‐up method for target protein analysis with mass spectrometry. 相似文献
33.
34.
Dr. Chisato Kato Ryo Machida Rio Maruyama Dr. Ryo Tsunashima Prof. Dr. Xiao‐Ming Ren Prof. Dr. Mohamedally Kurmoo Prof. Dr. Katsuya Inoue Dr. Sadafumi Nishihara 《Angewandte Chemie (International ed. in English)》2018,57(41):13429-13432
Continual progress has been achieved in information technology through unrelenting miniaturisation of the single memory bit in integrated ferromagnetic, ferroelectric, optical, and related circuits. However, as miniaturisation approaches its theoretical limit, new memory materials are being sought. Herein, we report a unique material exhibiting single‐molecule electric polarisation switching that can operate above room temperature. The phenomenon occurs in a Preyssler‐type polyoxometalate (POM) cluster we call a single‐molecule electret (SME). It exhibits all the characteristics of ferroelectricity but without long‐range dipole ordering. The SME affords bi‐stability as a result of the two potential positions of localisation of a Tb3+ ion trapped in the POM, resulting in extremely slow relaxation of the polarisation and electric hysteresis with high spontaneous polarisation and coercive electric fields. Our findings suggest that SMEs can potentially be applied to ultrahigh‐density memory 1 and other molecular‐level electronic devices operating above room temperature. 2 相似文献
35.
A Self‐Digitization Dielectrophoretic (SD‐DEP) Chip for High‐Efficiency Single‐Cell Capture,On‐Demand Compartmentalization,and Downstream Nucleic Acid Analysis 下载免费PDF全文
Yuling Qin Li Wu Thomas Schneider Gloria S. Yen Jiasi Wang Shihan Xu Min Li Amy L. Paguirigan Jordan L. Smith Jerald P. Radich Prof. Robbyn K. Anand Prof. Daniel T. Chiu 《Angewandte Chemie (International ed. in English)》2018,57(35):11378-11383
The design and fabrication of a self‐digitization dielectrophoretic (SD‐DEP) chip with simple components for single‐cell manipulation and downstream nucleic acid analysis is presented. The device employed the traditional DEP and insulator DEP to create the local electric field that is tailored to approximately the size of single cells, enabling highly efficient single‐cell capture. The multistep procedures of cell manipulation, compartmentalization, lysis, and analysis were performed in the integrated microdevice, consuming minimal reagents, minimizing contamination, decreasing lysate dilution, and increasing assay sensitivity. The platform developed here could be a promising and powerful tool in single‐cell research for precise medicine. 相似文献
36.
Highly Emissive Fused Heterocyclic Alkynylgold(III) Complexes for Multiple Color Emission Spanning from Green to Red for Solution‐Processable Organic Light‐Emitting Devices 下载免费PDF全文
Dr. Man‐Chung Tang Chin‐Ho Lee Dr. Maggie Ng Yi‐Chun Wong Dr. Mei‐Yee Chan Prof. Dr. Vivian Wing‐Wah Yam 《Angewandte Chemie (International ed. in English)》2018,57(19):5463-5466
A new class of fused heterocyclic tridentate ligand‐containing alkynylgold(III) complexes with tunable emission color has been successfully designed and synthesized. Structural modification of the σ‐donating fused heterocyclic alkynyl ligands, including substituted fluorene, carbazole, and triphenylamine, enables a large spectral shift of about 110 nm (ca. 3310 cm?1) that covers the green to red region to be realized with the same tridentate ligand‐containing alkynylgold(III) complexes in solid‐state thin films. Interestingly, the energy of the excimeric emission can be controlled by the rational design of the fused heterocyclic alkynyl ligands. Superior solution‐processable organic light‐emitting devices (OLEDs) with high external quantum efficiencies (EQEs) of 12.2, 13.5, 9.3, and 5.2 % were obtained with green, yellow, orange, and red emission. These high EQE values are comparable to those of the vacuum‐deposited OLEDs based on structurally related alkynylgold(III) complexes. 相似文献
37.
38.
Serge Beaupr Michel Belletête Gilles Durocher Mario Leclerc 《Macromolecular theory and simulations》2011,20(1):13-18
A reliable model that can be used to estimate the electronic properties (i.e., the HOMO, LUMO, and band gap energies) of conjugated polymers would be a great tool for applications in organic electronics such as light‐emitting diodes, field‐effect transistors, and photovoltaic cells. Recently, poly(2,7‐carbazole) derivatives have shown promising results when used as an active donor layer in bulk heterojunction photovoltaic cells with power conversion efficiency exceeding 7%. By using a simple correlation between density functional theory (DFT) theoretical calculations performed on six model compounds (using the repeating unit) and experimental data from the six corresponding polymers, an accurate estimation of the HOMO energy level, the LUMO energy levels, and the band gap of several poly(2,7‐carbazole) derivatives was obtained. According to the theoretical data obtained for more than one hundred repeating units, fourteen new copolymers that can be used as p‐type materials in bulk heterojunction solar cells were selected and synthesized. Experimental data obtained from these materials were then used to refine the correlation between DFT and experimental data of poly(2,7‐carbazole) derivatives.
39.
柔性电池作为新型柔性电子设备的关键部件,得到越来越多的关注.近年来,柔性锂离子电池取得了实质性的发展,并在卷曲式显示器、触摸屏、可穿戴动力传感器和可植入医疗装置等方面得到应用.本文主要介绍柔性锂离子电池的发展现状,分别从集流体、电极材料和电解质三部分进行阐述,特别介绍拉伸性能的实现途径,根据其不同的结构特点,可以分为波形结构、点阵互联结构、纺织结构、折纸结构和电缆式结构,并提出将柔性材料与新型结构相结合可以促进柔性电池发展.同时,也对其他柔性电池体系,如锂硫电池、燃料电池和太阳能电池等的最新发展进行简单概述.最后,对目前柔性电池的发展过程中存在的问题进行了总结,并对其未来的发展方向与面临的挑战进行展望. 相似文献
40.
Dr. Xueting Pan Dr. Weiwei Wang Dr. Zhijun Huang Shuang Liu Juan Guo Fengrong Zhang Hongjun Yuan Xin Li Prof. Fengyong Liu Prof. Huiyu Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13659-13663
The high reactive oxygen species (ROS) generation ability and simple construction of sonosensitizer systems remain challenging in sonodynamic therapy against the hypoxic tumor. In this work, we rationally prepared MOF-derived double-layer hollow manganese silicate nanoparticle (DHMS) with highly effective ROS yield under ultrasound irradiation for multimodal imaging-guided sonodynamic therapy (SDT). The presence of Mn in DHMS increased ROS generation efficiency because it could be oxidized by holes to improve the electron–hole separation. Moreover, DHMS could produce oxygen in the tumor microenvironment, which helps overcome the hypoxia of the solid tumor and thus enhance the treatment efficiency. In vivo experiments demonstrated efficient tumor inhibition in DHMS-mediated SDT guided by ultrasound and magnetic resonance imaging. This work presents a MOF-derived nanoparticle with sonosensitive and oxygen generating ability, which provides a promising strategy for tumor hypoxia in SDT. 相似文献