全文获取类型
收费全文 | 6462篇 |
免费 | 571篇 |
国内免费 | 464篇 |
专业分类
化学 | 3505篇 |
晶体学 | 53篇 |
力学 | 46篇 |
综合类 | 4篇 |
数学 | 13篇 |
物理学 | 1036篇 |
无线电 | 2840篇 |
出版年
2024年 | 25篇 |
2023年 | 493篇 |
2022年 | 126篇 |
2021年 | 308篇 |
2020年 | 261篇 |
2019年 | 244篇 |
2018年 | 165篇 |
2017年 | 334篇 |
2016年 | 436篇 |
2015年 | 373篇 |
2014年 | 589篇 |
2013年 | 466篇 |
2012年 | 439篇 |
2011年 | 366篇 |
2010年 | 306篇 |
2009年 | 363篇 |
2008年 | 291篇 |
2007年 | 309篇 |
2006年 | 264篇 |
2005年 | 193篇 |
2004年 | 205篇 |
2003年 | 124篇 |
2002年 | 107篇 |
2001年 | 108篇 |
2000年 | 62篇 |
1999年 | 73篇 |
1998年 | 57篇 |
1997年 | 69篇 |
1996年 | 42篇 |
1995年 | 38篇 |
1994年 | 38篇 |
1993年 | 34篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 31篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有7497条查询结果,搜索用时 367 毫秒
991.
Yeon Sik Choi Jahyun Koo Young Joong Lee Geumbee Lee Raudel Avila Hanze Ying Jonathan Reeder Leonhard Hambitzer Kyungtaek Im Jungwon Kim Kyung‐Mi Lee Jianjun Cheng Yonggang Huang Seung‐Kyun Kang John A. Rogers 《Advanced functional materials》2020,30(31)
Bioresorbable electronic systems represent an emerging class of technology of interest due to their ability to dissolve, chemically degrade, disintegrate, and/or otherwise physically disappear harmlessly in biological environments, as the basis for temporary implants that avoid the need for secondary surgical extraction procedures. Polyanhydride‐based polymers can serve as hydrophobic encapsulation layers for such systems, as a subset of the broader field of transient electronics, where biodegradation eventually occurs by chain scission. Systematic experimental studies that involve immersion in phosphate‐buffered saline solution at various pH values and/or temperatures demonstrate that dissolution occurs through a surface erosion mechanism, with little swelling. The mechanical properties of this polymer are well suited for use in soft, flexible devices, where integration can occur through a mold‐based photopolymerization technique. Studies of the dependence of the polymer properties on monomer compositions and the rates of permeation on coating thicknesses reveal some of the underlying effects. Simple demonstrations illustrate the ability to sustain operation of underlying biodegradable electronic systems for durations between a few hours to a week during complete immersion in aqueous solutions that approximate physiological conditions. Systematic chemical, physical, and in vivo biological studies in animal models reveal no signs of toxicity or other adverse biological responses. 相似文献
992.
Jiayi Yang David Tang Jinping Ao Tushar Ghosh Taylor V. Neumann Dongguang Zhang Egor Piskarev Tingting Yu Vi Khanh Truong Kai Xie Ying‐Chih Lai Yang Li Michael D. Dickey 《Advanced functional materials》2020,30(36)
Soft, capacitive tactile (pressure) sensors are important for applications including human–machine interfaces, soft robots, and electronic skins. Such capacitors consist of two electrodes separated by a soft dielectric. Pressing the capacitor brings the electrodes closer together and thereby increases capacitance. Thus, sensitivity to a given force is maximized by using dielectric materials that are soft and have a high dielectric constant, yet such properties are often in conflict with each other. Here, a liquid metal elastomer foam (LMEF) is introduced that is extremely soft (elastic modulus 7.8 kPa), highly compressible (70% strain), and has a high permittivity. Compressing the LMEF displaces the air in the foam structure, increasing the permittivity over a large range (5.6–11.7). This is called “positive piezopermittivity.” Interestingly, it is discovered that the permittivity of such materials decreases (“negative piezopermittivity”) when compressed to large strain due to the geometric deformation of the liquid metal droplets. This mechanism is theoretically confirmed via electromagnetic theory, and finite element simulation. Using these materials, a soft tactile sensor with high sensitivity, high initial capacitance, and large capacitance change is demonstrated. In addition, a tactile sensor powered wirelessly (from 3 m away) with high power conversion efficiency (84%) is demonstrated. 相似文献
993.
Cristian A. Silva Jian lv Lu Yin Itthipon Jeerapan Gabriel Innocenzi Fernando Soto Young‐Geun Ha Joseph Wang 《Advanced functional materials》2020,30(30)
The adoption of epidermal electronics into everyday life requires new design and fabrication paradigms, transitioning away from traditional rigid, bulky electronics towards soft devices that adapt with high intimacy to the human body. Here, a new strategy is reported for fabricating achieving highly stretchable “island‐bridge” (IB) electrochemical devices based on thick‐film printing process involving merging the deterministic IB architecture with stress‐enduring composite silver (Ag) inks based on eutectic gallium‐indium particles (EGaInPs) as dynamic electrical anchors within the inside the percolated network. The fabrication of free‐standing soft Ag‐EGaInPs‐based serpentine “bridges” enables the printed microstructures to maintain mechanical and electrical properties under an extreme (≈800%) strain. Coupling these highly stretchable “bridges” with rigid multifunctional “island” electrodes allows the realization of electrochemical devices that can sustain high mechanical deformation while displaying an extremely attractive and stable electrochemical performance. The advantages and practical utility of the new printed Ag‐liquid metal‐based island‐bridge designs are discussed and illustrated using a wearable biofuel cell. Such new scalable and tunable fabrication strategy will allow to incorporate a wide range of materials into a single device towards a wide range of applications in wearable electronics. 相似文献
994.
Katrin Ortstein Sebastian Hutsch Alexander Hinderhofer Jrn Vahland Martin Schwarze Sebastian Schellhammer Martin Hodas Thomas Geiger Hans Kleemann Holger F. Bettinger Frank Schreiber Frank Ortmann Karl Leo 《Advanced functional materials》2020,30(32)
In modern electronics, it is essential to adapt band structures by adjusting energy levels and band gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction in organic semiconductors allows for a continuous shift of the ionization energy (IE) over a wide range by mixing molecules with halogenated derivatives that exhibit different quadrupole moments. Here, this effect of energy level engineering on blends of pentacene and two fluorinated derivatives, in which the position but not the number of fluorine atoms differ, is studied. Structural investigations confirm that pentacene forms intermixed phases in blends with the fluorinated species. The investigation of electronic properties and simulations reveals a much larger shift of the ionization energy (1.5 eV) than in previous studies, allowing to test this model in a range not investigated so far, and emphasizing the role of the position of the halogen atoms. The tuning effect is preserved in electronic devices such as field‐effect transistors and significantly influences device characteristics. 相似文献
995.
Jinwoo Lee Heayoun Sul Yeongju Jung Hyeonseok Kim Seonggeun Han Joonhwa Choi Jaeho Shin Dongkwan Kim Jinwook Jung Sukjoon Hong Seung Hwan Ko 《Advanced functional materials》2020,30(36)
Cephalopods’ extraordinary ability to hide into any background has inspired researchers to reproduce the intriguing ability to readily camouflage in the infrared (IR) and visible spectrum but this still remains as a conundrum. In this study, a multispectral imperceptible skin that enables human skin to actively blend into the background both in the IR‐visible integrated spectrum only by simple temperature control with a flexible bi‐functional device (active cooling and heating) is developed. The thermochromic layer on the outer surface of the device, which produces various colors based on device surface temperature, expands the cloaking range to the visible spectrum (thus visible‐to‐IR) and ultimately completes day‐and‐night stealth platform simply by controlling device temperature. In addition, the scalable pixelization of the device allows localized control of each autonomous pixel, enabling the artificial skin surface to adapt to the background of the sophisticated pattern with higher resolution and eventually heightening the level of imperceptibility. As this proof‐of‐concept can be directly worn and conceals the human skin in multispectral ranges, the work is expected to contribute to the development of next‐generation soft covert military wearables and perhaps a multispectral cloak that belongs to cephalopods or futuristic camouflage gadgets in the movies. 相似文献
996.
Adeela Hanif Atanu Bag Arsalan Zabeeb Dong‐Bin Moon Surjeet Kumar Sajal Shrivastava Nae‐Eung Lee 《Advanced functional materials》2020,30(38)
Mimicking the skin's non‐linear self‐limiting mechanical characteristics is of great interest. Skin is soft at low strain but becomes stiff at high strain and thereby can protect human tissues and organs from high mechanical loads. Herein, the design of a skin‐inspired substrate is reported based on a spaghetti‐like multi‐nanofiber network (SMNN) of elastic polyurethane (PU) nanofibers (NFs) sandwiched between stiff poly(vinyldenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) NFs layers embedded in polydimethylsiloxane elastomer. The elastic moduli of the stretchable skin‐inspired substrate can be tuned in a range that matches well with the mechanical properties of skins by adjusting the loading ratios of the two NFs. Confocal imaging under stretching indicates that PU NFs help maintain the stretchability while adding stiff P(VDF‐TrFE) NFs to control the self‐limiting characteristics. Interestingly, the Au layer on the substrate indicates a negligible change in the resistance under cyclic (up to 7000 cycles at 35% strain) and dynamic stretching (up to 35% strain), which indicates the effective absorption of stress by the SMNN. A stretchable chemoresistive gas sensor on the skin‐inspired substrate also demonstrates a reasonable stability in NO2 sensing response under strain up to 30%. The skin‐inspired substrate with SMNN provides a step toward ultrathin stretchable electronics. 相似文献
997.
998.
Vladimir M. Mostepanenko Elena N. Velichko Maksim Aleksandrovich Baranov 《电子科技学刊:英文版》2020,18(1):52-58
Thin organic films find expanding applications in electronic and optoelectronic devices, biotechnology, food packing, and for many other purposes. Among other factors, the stability of films with a thickness below a micrometer is determined by the zero-point and thermal fluctuations of the electromagnetic field. These fluctuations result in the van der Waals and Casimir free energy and forces between a film and a substrate. The fluctuation-induced force may be both attractive and repulsive making the film either more or less stable, respectively. Here, we review recently obtained results for the Casimir free energy of both freestanding and deposited on the metallic and dielectric substrates peptide films. We also perform computations for the free energy of the peptide films deposited on a silica glass substrate in the region of parameters where this free energy vanishes. Possible applications of the obtained results are discussed. 相似文献
999.
Mini Sreejeth Madhusudan Singh Parmod Kumar 《International Journal of Electronics》2019,106(9):1281-1294
In this paper, efficiency enhancement algorithms are developed and implemented on an indirect vector-controlled three-phase induction motor (IM) drive, and its performance under different operating conditions is analysed. The controllable electrical losses in the IM are minimised through the optimal control of direct axis (d-axis) stator current, and improvement in motor efficiency is achieved by weakening the rotor flux. The optimal d-axis stator current is also estimated using particle swarm optimisation (PSO) to validate the results obtained through analytical control method. The developed algorithms are tested under various operating conditions and the dynamic performance of the IM drive is analysed. The effectiveness of analytical and PSO-based efficiency optimisation control over conventional constant flux control, especially during light load at rated speed operation, is summarised. The effectiveness of the developed algorithm is validated experimentally through development of laboratory prototype set-up. The effect of parametric variation on efficiency, stator current, torque and speed of IM drive is studied through sensitivity analysis. The effect of variation in stator and rotor resistance due to change in operating temperature of the IM is also analysed and the robustness of the developed algorithm against parametric variations is demonstrated through simulation and experimental studies. 相似文献
1000.