全文获取类型
收费全文 | 9475篇 |
免费 | 1229篇 |
国内免费 | 1805篇 |
专业分类
化学 | 7717篇 |
晶体学 | 53篇 |
力学 | 154篇 |
综合类 | 75篇 |
数学 | 442篇 |
物理学 | 1374篇 |
无线电 | 2694篇 |
出版年
2024年 | 24篇 |
2023年 | 136篇 |
2022年 | 188篇 |
2021年 | 296篇 |
2020年 | 290篇 |
2019年 | 319篇 |
2018年 | 209篇 |
2017年 | 347篇 |
2016年 | 364篇 |
2015年 | 407篇 |
2014年 | 486篇 |
2013年 | 524篇 |
2012年 | 944篇 |
2011年 | 628篇 |
2010年 | 512篇 |
2009年 | 614篇 |
2008年 | 692篇 |
2007年 | 718篇 |
2006年 | 657篇 |
2005年 | 587篇 |
2004年 | 563篇 |
2003年 | 464篇 |
2002年 | 347篇 |
2001年 | 295篇 |
2000年 | 256篇 |
1999年 | 224篇 |
1998年 | 203篇 |
1997年 | 193篇 |
1996年 | 130篇 |
1995年 | 138篇 |
1994年 | 139篇 |
1993年 | 129篇 |
1992年 | 114篇 |
1991年 | 102篇 |
1990年 | 95篇 |
1989年 | 56篇 |
1988年 | 35篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 491 毫秒
1.
We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope. 相似文献
2.
3.
《Comptes Rendus Chimie》2015,18(9):993-1000
The electrochemical oxidation of N-acetyl-p-aminophenol (PAR) was investigated at a Pt electrode with the application of cyclic (CV) and differential pulse (DPV) voltammetry methods. An effect of scan rate, substrate concentration and pH on electrode reactions was determined. The parameters of substrate electro-oxidation, i.e. heterogeneous rate constant, charge transfer coefficient, and diffusion coefficient, were calculated. Our investigation's results prove the exchange of two electrons and one proton in the first step, followed by a chemical reaction. PAR electro-oxidation occurs according to an EC mechanism. 相似文献
4.
James E. Tyrrell Martyn G. Boutelle Alasdair J. Campbell 《Advanced functional materials》2021,31(1):2007086
Biological environments use ions in charge transport for information transmission. The properties of mixed electronic and ionic conductivity in organic materials make them ideal candidates to transduce physiological information into electronically processable signals. A device proven to be highly successful in measuring such information is the organic electrochemical transistor (OECT). Previous electrophysiological measurements performed using OECTs show superior signal-to-noise ratios than electrodes at low frequencies. Subsequent development has significantly improved critical performance parameters such as transconductance and response time. Here, interdigitated-electrode OECTs are fabricated on flexible substrates, with one such state-of-the-art device achieving a peak transconductance of 139 mS with a 138 µs response time. The devices are implemented into an array with interconnects suitable for micro-electrocorticographic application and eight architecture variations are compared. The two best-performing arrays are subject to the full electrophysiological spectrum using prerecorded signals. With frequency filtering, kHz-scale frequencies with 10 µV-scale voltages are resolved. This is supported by a novel quantification of the noise, which compares the gate voltage input and drain current output. These results demonstrate that high-performance OECTs can resolve the full electrophysiological spectrum and suggest that superior signal-to-noise ratios could be achieved in high frequency measurements of multiunit activity. 相似文献
5.
《Discrete Mathematics》2019,342(3):623-627
Wang and Lih (2002) conjectured that every planar graph without adjacent triangles is 4-choosable. In this paper, we prove that every planar graph without any 4-cycle adjacent to two triangles is DP-4-colorable, which improves the results of Lam et al. (1999), Cheng et al. (2016) and Kim and Yu [ arXiv:1709.09809v1]. 相似文献
6.
7.
用周期波导的方法分析平面阵列波导光栅(AWG)的本征方程及波导模式参数,结果表明波导传播常数是带状分布的,与波导间隔有关。分析结果对器件的优化设计有一定的指导意义。 相似文献
8.
应用二维器件仿真程序 PISCES- ,对槽栅结构和平面结构器件的特性进行了模拟比较 ,讨论了槽栅结构 MOSFET的沟道电场特征及其对热载流子效应的影响。槽栅结构对抑制短沟道效应和抗热载流子效应是十分有利的 ,而此种结构对热载流子的敏感 ,使器件的亚阈值特性、输出特性变化较大 相似文献
9.
10.