全文获取类型
收费全文 | 2562篇 |
免费 | 88篇 |
国内免费 | 7篇 |
专业分类
化学 | 1930篇 |
晶体学 | 7篇 |
力学 | 22篇 |
数学 | 305篇 |
物理学 | 290篇 |
无线电 | 103篇 |
出版年
2023年 | 16篇 |
2022年 | 15篇 |
2021年 | 32篇 |
2020年 | 63篇 |
2019年 | 39篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 79篇 |
2015年 | 70篇 |
2014年 | 82篇 |
2013年 | 127篇 |
2012年 | 165篇 |
2011年 | 167篇 |
2010年 | 93篇 |
2009年 | 82篇 |
2008年 | 146篇 |
2007年 | 122篇 |
2006年 | 124篇 |
2005年 | 126篇 |
2004年 | 134篇 |
2003年 | 93篇 |
2002年 | 105篇 |
2001年 | 49篇 |
2000年 | 46篇 |
1999年 | 38篇 |
1998年 | 31篇 |
1997年 | 38篇 |
1996年 | 38篇 |
1995年 | 39篇 |
1994年 | 47篇 |
1993年 | 41篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1990年 | 25篇 |
1989年 | 26篇 |
1988年 | 29篇 |
1987年 | 15篇 |
1985年 | 28篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 19篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1973年 | 9篇 |
1970年 | 10篇 |
排序方式: 共有2657条查询结果,搜索用时 10 毫秒
11.
Uwe Einmahl 《Probability Theory and Related Fields》1992,92(2):177-194
Summary In a previous paper we obtained upper and lower class type results refining the bounded LIL for sums of iid Hilbert space valued mean zero random variables, whose covariance operators satisfy certain regularity assumptions. We now establish precise convergence rates for the bounded LIL in the non-regular case. It turns out that the almost sure behavior in this case is entirely different from the behavior in the previous situation.Supported in part by NSF Grant DMS 90-05804 相似文献
12.
Physical Mechanisms behind the Field‐Cycling Behavior of HfO2‐Based Ferroelectric Capacitors 下载免费PDF全文
Milan Pešić Franz Paul Gustav Fengler Luca Larcher Andrea Padovani Tony Schenk Everett D. Grimley Xiahan Sang James M. LeBeau Stefan Slesazeck Uwe Schroeder Thomas Mikolajick 《Advanced functional materials》2016,26(25):4601-4612
Novel hafnium oxide (HfO2)‐based ferroelectrics reveal full scalability and complementary metal oxide semiconductor integratability compared to perovskite‐based ferroelectrics that are currently used in nonvolatile ferroelectric random access memories (FeRAMs). Within the lifetime of the device, two main regimes of wake‐up and fatigue can be identified. Up to now, the mechanisms behind these two device stages have not been revealed. Thus, the main scope of this study is an identification of the root cause for the increase of the remnant polarization during the wake‐up phase and subsequent polarization degradation with further cycling. Combining the comprehensive ferroelectric switching current experiments, Preisach density analysis, and transmission electron microscopy (TEM) study with compact and Technology Computer Aided Design (TCAD) modeling, it has been found out that during the wake‐up of the device no new defects are generated but the existing defects redistribute within the device. Furthermore, vacancy diffusion has been identified as the main cause for the phase transformation and consequent increase of the remnant polarization. Utilizing trap density spectroscopy for examining defect evolution with cycling of the device together with modeling of the degradation results in an understanding of the main mechanisms behind the evolution of the ferroelectric response. 相似文献
13.
Uwe Weigmann Knut Deimer Christian Leininger Ludwig Turba Steffen Jurran 《e & i Elektrotechnik und Informationstechnik》2002,119(11):a19-a19
Firmen&ProdukteDehn Austria
überspannungs-schutz in der Telekommunikation 相似文献14.
Christian Pacha Oliver Kessler Peter Glo¨seko¨tter Karl F. Goser Werner Prost Andreas Brennemann Uwe Auer Franz J. Tegude 《Analog Integrated Circuits and Signal Processing》2000,24(1):7-25
Quantum-effect devices utilizing resonant tunneling are promising candidates for future nano-scale integration. Originating from the technological progress of semiconductor technology, circuit architectures with reduced complexity are investigated by exploiting the negative-differential resistance of resonant tunneling devices. In this paper a resonant tunneling device threshold logic family based on the Monostable-Bistable Transition Logic Element (MOBILE) is proposed and applied to different parallel adder designs, such as ripple carry and binary carry lookahead adders. The basic device is a resonant tunneling transistor (RTT) composed of a resonant tunneling diode monolithically integrated on the drain contact layer of a heterostructure field effect transistor. On the circuit level the key components are a programmable NAND/NOR logic gate, threshold logic gates, and parallel counters. The special properties of MOBILE logic gates are considered by a bit-level pipelined circuit style. Experimental results are presented for the NAND/NOR logic gate. 相似文献
15.
16.
Weiyuan Duan Gilbert Mains Habtamu Tsegaye Gebrewold Karsten Bittkau Andreas Lambertz Binbin Xu Volker Lauterbach Alexander Eberst Nathan Nicholson Lars Korte Muhammad Ainul Yaqin Kai Zhang Qing Yang Uwe Rau Kaining Ding 《Advanced functional materials》2024,34(3):2310552
An intrinsic hydrogenated amorphous silicon (a-Si:H(i)) film and a doped silicon film are usually combined in the heterojunction contacts of silicon heterojunction (SHJ) solar cells. In this work, a post-doping process called catalytic doping (Cat-doping) on a-Si:H(i) is performed on the electron selective side of SHJ solar cells, which enables a device architecture that eliminates the additional deposition of the doped silicon layer. Thus, a single phosphorus Cat-doping layer combines the functions of two other layers by enabling excellent interface passivation and high carrier selectivity. The overall thinner layer on the window side results in higher spectral response at short wavelengths, leading to an improved short-circuit current density of 40.31 mA cm−2 and an efficiency of 23.65% (certified). The cell efficiency is currently limited by sputter damage from the subsequent transparent conductive oxide fabrication and low carrier activation in the a-Si:H(i) with Cat-doping. Numerical device simulations show that the a-Si:H(i) with Cat-doping can provide sufficient field effect passivation even at lower active carrier concentrations compared to the as-deposited doped layer, due to the lower defect density. 相似文献
17.
State‐of‐the‐Art Neutral Tint Multichromophoric Polymers for High‐Contrast See‐Through Electrochromic Devices 下载免费PDF全文
Mauro Sassi Matteo M. Salamone Riccardo Ruffo Giorgio E. Patriarca Claudio M. Mari Giorgio A. Pagani Uwe Posset Luca Beverina 《Advanced functional materials》2016,26(29):5240-5246
Two new multichromophoric electrochromic polymers featuring a conjugated EDOT/ProDOT copolymer backbone (PXDOT) and a reversible Weitz‐type redox active small molecule electrochrome (WTE) tethered to the conjugated chain are reported here. The careful design of the WTEs provides a highly reversible redox behavior with a colorless red switching that complements the colorless blue switching of the conjugated backbone. Subtractive color mixing successfully provides high performing solution processable polymeric layers with colorless neutral tint switchable limiting states for application in see‐through electrochromic devices. Design, synthesis, comprehensive chemical and spectroelectrochemical characterization as well as the preparation of a proof‐of‐concept device are discussed. 相似文献
18.
Raqibul Mostafa Ramesh C. Pallat Uwe Ringel Ashok A. Tikku Jeffrey H. Reed 《ETRI Journal》2012,34(3):319-329
Closed‐loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal‐to‐noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two‐element array. It is shown that for a two‐element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter‐element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors. 相似文献
19.
A novel sensor consisting of nitrogen-doped multi-walled carbon nanotubes was fabricated by means of chemical vapor deposition technique with decomposition of acetonitrile onto oxidized silicon wafer using ferrocene as catalyst. The electrochemical response of carbon nanotubes-based sensor towards oxidation of paracetamol to N-acetyl-p-quinone imine was investigated in phosphate buffer solution (pH 7.0) by means of standard electrochemical techniques. A quasi-reversible response for oxidation of paracetamol was identified on carbon nanotubes-based sensor with detection limit and sensitivity of 0.485 μM and 0.8406 A M?1 cm?2, respectively. It was found that the nitrogen doping in carbon nanotubes enhances the sensor's detection ability. Namely, electrochemical studies performed on film consisting of pristine carbon nanotubes reveal as well quasi-reversible response towards oxidation of paracetamol but nevertheless poorer detection ability and sensitivity (0.950 μM; 0.601 A M?1 cm?2). The findings strongly suggest the application of nitrogen-doped carbon nanotubes in biosensing. 相似文献
20.
We have detected a fundamental pulse-compression limit for high-nonlinear fibers in the normal dispersion regime near the zero-dispersion wavelength. The desired generation of a broadband continuum by self-phase modulation is limited by already small amounts of third-order dispersion (TOD), which results in pulse splitting above a critical pulse power. We investigate the critical fiber length in dependence on pulse- and fiber parameters. 相似文献