全文获取类型
收费全文 | 23232篇 |
免费 | 3462篇 |
国内免费 | 2412篇 |
专业分类
化学 | 12586篇 |
晶体学 | 188篇 |
力学 | 1202篇 |
综合类 | 136篇 |
数学 | 2025篇 |
物理学 | 5954篇 |
无线电 | 7015篇 |
出版年
2024年 | 93篇 |
2023年 | 538篇 |
2022年 | 664篇 |
2021年 | 828篇 |
2020年 | 825篇 |
2019年 | 842篇 |
2018年 | 667篇 |
2017年 | 707篇 |
2016年 | 936篇 |
2015年 | 1000篇 |
2014年 | 1268篇 |
2013年 | 1507篇 |
2012年 | 1911篇 |
2011年 | 1872篇 |
2010年 | 1334篇 |
2009年 | 1314篇 |
2008年 | 1478篇 |
2007年 | 1325篇 |
2006年 | 1315篇 |
2005年 | 1094篇 |
2004年 | 818篇 |
2003年 | 742篇 |
2002年 | 755篇 |
2001年 | 642篇 |
2000年 | 520篇 |
1999年 | 520篇 |
1998年 | 419篇 |
1997年 | 407篇 |
1996年 | 406篇 |
1995年 | 324篇 |
1994年 | 262篇 |
1993年 | 206篇 |
1992年 | 226篇 |
1991年 | 205篇 |
1990年 | 153篇 |
1989年 | 141篇 |
1988年 | 99篇 |
1987年 | 78篇 |
1986年 | 98篇 |
1985年 | 74篇 |
1984年 | 63篇 |
1983年 | 48篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1978年 | 24篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1974年 | 25篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Chongyu Mei Junqiao Ding Bing Yao Yanxiang Cheng Zhiyuan Xie Yanhou Geng Lixiang Wang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1746-1757
Two orange phosphorescent iridium complex monomers, 9‐hexyl‐9‐(iridium (III)bis(2‐(4′‐fluorophenyl)‐4‐phenylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐PIr) and 9‐hexyl‐9‐(iridium(III)bis(2‐(4′‐fluorophenyl)‐4‐methylquinoline‐N,C2′)(tetradecanedionate‐11,13))‐2,7‐dibromofluorene (Br‐MIr), were successfully synthesized. The Suzuki polycondensation of 2,7‐bis(trimethylene boronate)‐9,9‐dioctylfluorene with 2,7‐dibromo‐9,9‐dioctylfluorene and Br‐PIr or Br‐MIr afforded two series of copolymers, PIrPFs and MIrPFs, in good yields, in which the concentrations of the phosphorescent moieties were kept small (0.5–3 mol % feed ratio) to realize incomplete energy transfer. The photoluminescence (PL) of the copolymers showed blue‐ and orange‐emission peaks. A white‐light‐emitting diode with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/PIr05PF (0.5 mol % feed ratio of Br‐PIr)/Ca/Al exhibited a luminous efficiency of 4.49 cd/A and a power efficiency of 2.35 lm/W at 6.0 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.46, 0.33). The CIE coordinates were improved to (0.34, 0.33) when copolymer MIr10PF (1.0 mol % feed ratio of Br‐MIr) was employed as the white‐emissive layer. The strong orange emission in the electroluminescence spectra in comparison with PL for these kinds of polymers was attributed to the additional contribution of charge trapping in the phosphorescent dopants. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 1746–1757, 2007 相似文献
63.
64.
A configurable nonlinear filter generator is proposed. The nonlinear function employed is key controllable. By changing the key, a different sequence will be obtained. Simulated results show that an optimal linear complexity profile of the sequence can be generated 相似文献
65.
An adaptive morphological filter for image processing 总被引:6,自引:0,他引:6
Novel types of opening operator (NOP) and closing operator (NCP) are proposed. An adaptive morphological filter is then constructed on the basis of the NOP and NCP. The filter can remove any details consisting of fewer pixels than a given number N, while preserving the other details. Efficient algorithms are also developed for the implementation of the NOP and NCP. 相似文献
66.
The general volume equivalence theorem for bianisotropic scatterers is presented, where the equivalent electric and magnetic currents are determined by a pair of coupled vector integral equations. Moreover, using the general volume equivalence theorem and conventional image principle, image theory is developed for a bianisotropic body over an infinite perfect electric or magnetic conducting ground plane. 相似文献
67.
本文描述了用膜吸收法测量激光等离子体辐射温度空间分布的原理和方法给出了柱形缝靶轴向辐射温度随空间位置变化的特征,对测量结果进行了分析讨论。 相似文献
68.
A triaxial omega medium, which can be artificially realised by embedding three types of omega-shaped particles in an isotropic host medium, is proposed. The Green dyadic and the electromagnetic field of a dipole radiator are presented, by introducing a set of auxiliary fields and coordinate transformation 相似文献
69.
Chung S.S. Shui-Ming Cheng Lee R.G.-H. Song-Nian Kuo Mong-Song Liang 《Electron Devices, IEEE Transactions on》1997,44(12):2220-2226
This paper reports a simple I-V method for the first time to determine the lateral lightly-doped source/drain (S/D) profiles (n- region) of LDD n-MOSFETs. One interesting result is the direct observation of the reverse-short-channel effect (RSCE). It is observed that S/D n- doping profile is channel length dependent if reverse short-channel effect exists as a result of the interstitial imperfections caused by Oxide Enhanced Diffusion (OED) or S/D implant. Not only the lateral profiles for long-channel devices but also for short-channel devices can be determined. One other practical application of the present method for device drain engineering has been demonstrated with a LATID MOS device drain engineering work. It is convincible that the proposed method is well suited for the characterization and optimization of submicron and deep-submicron MOSFETs in the current ULSI technology 相似文献
70.
The coordinate rotation digital computer (CORDIC) algorithm is used in numerous special purpose systems for real-time signal processing applications. It uses barrel shifters to complete shift operations. However, the barrel shifter occupies most of the area of the CORDIC chip. A new structure of multilevel barrel shifters is presented. With this structure the shifter size is reduced by 68%. The novel structure can also slightly reduce the latency time of shift operations 相似文献