全文获取类型
收费全文 | 135674篇 |
免费 | 20315篇 |
国内免费 | 15344篇 |
专业分类
化学 | 72510篇 |
晶体学 | 1140篇 |
力学 | 5927篇 |
综合类 | 669篇 |
数学 | 12643篇 |
物理学 | 39610篇 |
无线电 | 38834篇 |
出版年
2024年 | 551篇 |
2023年 | 3152篇 |
2022年 | 4190篇 |
2021年 | 5159篇 |
2020年 | 5205篇 |
2019年 | 4703篇 |
2018年 | 4436篇 |
2017年 | 4161篇 |
2016年 | 5889篇 |
2015年 | 6253篇 |
2014年 | 7675篇 |
2013年 | 9761篇 |
2012年 | 11416篇 |
2011年 | 11607篇 |
2010年 | 8609篇 |
2009年 | 8521篇 |
2008年 | 8786篇 |
2007年 | 7967篇 |
2006年 | 7559篇 |
2005年 | 6626篇 |
2004年 | 4828篇 |
2003年 | 4034篇 |
2002年 | 3630篇 |
2001年 | 3101篇 |
2000年 | 2817篇 |
1999年 | 2940篇 |
1998年 | 2505篇 |
1997年 | 2172篇 |
1996年 | 2144篇 |
1995年 | 1901篇 |
1994年 | 1618篇 |
1993年 | 1348篇 |
1992年 | 1179篇 |
1991年 | 997篇 |
1990年 | 830篇 |
1989年 | 591篇 |
1988年 | 462篇 |
1987年 | 378篇 |
1986年 | 383篇 |
1985年 | 293篇 |
1984年 | 221篇 |
1983年 | 191篇 |
1982年 | 141篇 |
1981年 | 84篇 |
1980年 | 65篇 |
1979年 | 27篇 |
1978年 | 28篇 |
1976年 | 24篇 |
1975年 | 23篇 |
1957年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Wireless Personal Communications - In recent years, many wireless communication services have become indispensable for our daily life, such as voice telephoning and the internet surfing. However,... 相似文献
52.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
53.
Wireless Personal Communications - The traditional simultaneous wireless information and power transfer (SWIPT) system uses a part of signals to decode information, and the other part is used for... 相似文献
54.
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from... 相似文献
55.
56.
Unsymmetrical Pyrene‐Fused Phthalocyanine Derivatives: Synthesis,Structure, and Properties
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)
Houhe Pan Chao Chen Kang Wang Prof. Dr. Wenjun Li Prof. Dr. Jianzhuang Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3168-3173
Novel pyrene‐fused unsymmetrical phthalocyanine derivatives 2,3,9,10,16,17‐hexakis(2,6‐dimethylphenoxy)‐22,25‐diaza(2,7‐di‐tert‐butylpyrene)[4,5]phthalocyaninato zinc complex Zn[Pc(Pz‐pyrene)(OC8H9)6] ( 1 ) and 2,3,9,10‐tra(2,6‐dimethylphenoxy)‐15,18,22,25‐traza(2,7‐di‐tert‐butylpyrene)[4,5]phthalocyaninato zinc compound Zn[Pc(Pz‐pyrene)2(OC8H9)4] ( 2 ) were isolated for the first time. These unsymmetrical pyrene‐fused phthalocyanine derivatives have been characterized by a wide range of spectroscopic and electrochemical methods. In particular, the pyrene‐fused phthalocyanine structure was unambiguously revealed on the basis of single crystal X‐ray diffraction analysis of 1 , representing the first structurally characterized phthalocyanine derivative fused with an aromatic moiety larger than benzene. 相似文献
57.
58.
59.
60.