全文获取类型
收费全文 | 25249篇 |
免费 | 3981篇 |
国内免费 | 1389篇 |
专业分类
化学 | 3568篇 |
晶体学 | 94篇 |
力学 | 1128篇 |
综合类 | 273篇 |
数学 | 6794篇 |
物理学 | 6873篇 |
无线电 | 11889篇 |
出版年
2024年 | 40篇 |
2023年 | 239篇 |
2022年 | 397篇 |
2021年 | 562篇 |
2020年 | 672篇 |
2019年 | 640篇 |
2018年 | 622篇 |
2017年 | 854篇 |
2016年 | 975篇 |
2015年 | 992篇 |
2014年 | 1557篇 |
2013年 | 1907篇 |
2012年 | 1617篇 |
2011年 | 1728篇 |
2010年 | 1489篇 |
2009年 | 1559篇 |
2008年 | 1677篇 |
2007年 | 1653篇 |
2006年 | 1518篇 |
2005年 | 1304篇 |
2004年 | 1146篇 |
2003年 | 1152篇 |
2002年 | 973篇 |
2001年 | 786篇 |
2000年 | 741篇 |
1999年 | 611篇 |
1998年 | 544篇 |
1997年 | 486篇 |
1996年 | 368篇 |
1995年 | 347篇 |
1994年 | 238篇 |
1993年 | 196篇 |
1992年 | 161篇 |
1991年 | 128篇 |
1990年 | 95篇 |
1989年 | 100篇 |
1988年 | 66篇 |
1987年 | 51篇 |
1986年 | 47篇 |
1985年 | 82篇 |
1984年 | 60篇 |
1983年 | 30篇 |
1982年 | 38篇 |
1981年 | 38篇 |
1980年 | 20篇 |
1979年 | 27篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
11.
12.
This paper considers the state‐dependent interference relay channel (SIRC) in which one of the two users may operate as a secondary user and the relay has a noncausal access to the signals from both users. For discrete memoryless SIRC, we first establish the achievable rate region by carefully merging Han‐Kobayashi rate splitting encoding technique, superposition encoding, and Gelfand‐Pinsker encoding technique. Then, based on the achievable rate region that we derive, the capacity of the SIRC is established in many different scenarios including (a) the weak interference regime, (b) the strong interference regime, and (c) the very strong interference regime. This means that our capacity results contain all available known results in the literature. Next, the achievable rate region and the associated capacity results are also evaluated in the case of additive Gaussian noise. Additionally, many numerical examples are investigated to show the value of our theoretical derivations. 相似文献
13.
Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
14.
为了减小传统的最差情况设计方法引入的电压裕量,提出了一种变化可知的自适应电压缩减(AVS)技术,通过调整电源电压来降低电路功耗.自适应电压缩减技术基于检测关键路径的延时变化,基于此设计了一款预错误原位延时检测电路,可以检测关键路径延时并输出预错误信号,进而控制单元可根据反馈回的预错误信号的个数调整系统电压.本芯片采用SMIC180 nm工艺设计验证,仿真分析表明,采用自适应电压缩减技术后,4个目标验证电路分别节省功耗12.4%,11.3%,10.4%和11.6%. 相似文献
15.
We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors. 相似文献
16.
17.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
18.
《Comptes Rendus Mecanique》2019,347(4):318-331
In this essay we explore analogies between macroscopic patterns, which result from a sequence of phase transitions/instabilities starting from a homogeneous state, and similar phenomena in cosmology, where a sequence of phase transitions in the early universe is believed to have separated the fundamental forces from each other, and also shaped the structure and distribution of matter in the universe. We discuss three distinct aspects of this analogy: (i) Defects and topological charges in macroscopic patterns are analogous to spins and charges of quarks and leptons; (ii) Defects in generic 3+1 stripe patterns carry an energy density that accounts for phenomena that are currently attributed to dark matter; (iii) Space-time patterns of interacting nonlinear waves display behaviors reminiscent of quantum phenomena including inflation, entanglement and dark energy. 相似文献
19.
Azobenzene‐Functionalized Cage Silsesquioxanes as Inorganic–Organic Hybrid,Photoresponsive, Nanoscale,Building Blocks
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Hongzhi Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4731-4738
Mono‐ and octa‐azobenzene‐functionalized cage silsesquioxanes were easily synthesized by the reaction of 4‐bromoazobenzene with monovinyl‐substituted octasilsesquioxane and cubic octavinylsilsesquioxane through the Heck coupling reaction. Excited‐state energies obtained from time‐dependent density functional theory (TDDFT) and the CAM‐B3LYP functional correlate very well with experimental trans–cis photoisomerization results from UV/Vis spectroscopy. These azobenzene‐functionalized cages exhibit good thermal stability and are fluorescent with maximum emission at approximately 400 nm, making them potential materials for blue‐light emission. 相似文献
20.
激光脉冲编码是激光制导武器的抗干扰措施之一。角度欺骗式干扰和高重频干扰是目前半主动激光制导武器的主要有源干扰来源。为研究不同激光脉冲编码方式对激光半主动制导武器抗这两种干扰性能的影响,本文针对敌方激光告警机的识别算法与我方导引头的解码过程,提出自相关函数与归一化互相关函数评价方法,并对目前主要编码方式进行仿真,仿真结果表明:激光脉冲编码的抗角度欺骗式干扰能力受编码序列周期性与脉冲间隔随机性的影响;抗高重频激光干扰能力受编码序列脉冲间隔随机性的影响;LFSR状态码的抗角度欺骗式干扰与抗高重频干扰效果均优于其他编码方式。 相似文献