全文获取类型
收费全文 | 23212篇 |
免费 | 3829篇 |
国内免费 | 2589篇 |
专业分类
化学 | 16293篇 |
晶体学 | 264篇 |
力学 | 1404篇 |
综合类 | 240篇 |
数学 | 2634篇 |
物理学 | 8795篇 |
出版年
2024年 | 12篇 |
2023年 | 491篇 |
2022年 | 494篇 |
2021年 | 672篇 |
2020年 | 974篇 |
2019年 | 887篇 |
2018年 | 739篇 |
2017年 | 709篇 |
2016年 | 1074篇 |
2015年 | 989篇 |
2014年 | 1238篇 |
2013年 | 1621篇 |
2012年 | 2053篇 |
2011年 | 2076篇 |
2010年 | 1424篇 |
2009年 | 1366篇 |
2008年 | 1531篇 |
2007年 | 1403篇 |
2006年 | 1342篇 |
2005年 | 1086篇 |
2004年 | 870篇 |
2003年 | 709篇 |
2002年 | 587篇 |
2001年 | 501篇 |
2000年 | 481篇 |
1999年 | 556篇 |
1998年 | 471篇 |
1997年 | 407篇 |
1996年 | 411篇 |
1995年 | 383篇 |
1994年 | 355篇 |
1993年 | 321篇 |
1992年 | 266篇 |
1991年 | 229篇 |
1990年 | 232篇 |
1989年 | 158篇 |
1988年 | 119篇 |
1987年 | 82篇 |
1986年 | 96篇 |
1985年 | 65篇 |
1984年 | 37篇 |
1983年 | 39篇 |
1982年 | 37篇 |
1981年 | 20篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
A Cascade‐Reaction Nanoreactor Composed of a Bifunctional Molecularly Imprinted Polymer that Contains Pt Nanoparticles 下载免费PDF全文
Jiao Wang Dr. Maiyong Zhu Dr. Xiaojuan Shen Prof. Songjun Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7532-7539
This study was aimed at addressing the present challenge of cascade reactions, namely, how to furnish the catalysts with desired and hierarchical catalytic ability. This issue was addressed by constructing a cascade‐reaction nanoreactor made of a bifunctional molecularly imprinted polymer containing acidic catalytic sites and Pt nanoparticles. The acidic catalytic sites within the imprinted polymer allowed one specified reaction, whereas the encapsulated Pt nanoparticles were responsible for another coupled reaction. To that end, the unique imprinted polymer was fabricated by using two well‐coupled templates, that is, 4‐nitrophenyl acetate and 4‐nitrophenol. The catalytic hydrolysis of the former compound at the acidic catalytic sites led to the formation of the latter compound, which was further reduced by the encapsulated Pt nanoparticles to 4‐aminophenol. Therefore, this nanoreactor demonstrated a catalytic‐cascade ability. This protocol opens up the opportunity to develop functional catalysts for complicated chemical processes. 相似文献
65.
Application of ion mobility tandem mass spectrometry to compositional and structural analysis of glycopeptides extracted from the urine of a patient diagnosed with Schindler disease 下载免费PDF全文
66.
Yaping Chen Dr. Kun Rui Prof. Jixin Zhu Prof. Shi Xue Dou Dr. Wenping Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):703-713
Developing clean and sustainable energies as alternatives to fossil fuels is in strong demand within modern society. The oxygen evolution reaction (OER) is the efficiency-limiting process in plenty of key renewable energy systems, such as electrochemical water splitting and rechargeable metal–air batteries. In this regard, ongoing efforts have been devoted to seeking high-performance electrocatalysts for enhanced energy conversion efficiency. Apart from traditional precious-metal-based catalysts, nickel-based compounds are the most promising earth-abundant OER catalysts, attracting ever-increasing interest due to high activity and stability. In this review, the recent progress on nickel-based oxide and (oxy)hydroxide composites for water oxidation catalysis in terms of materials design/synthesis and electrochemical performance is summarized. Some underlying mechanisms to profoundly understand the catalytic active sites are also highlighted. In addition, the future research trends and perspectives on the development of Ni-based OER electrocatalysts are discussed. 相似文献
67.
Bingjie Chen Dr. Lianhai Zu Dr. Yao Liu Dr. Ruijing Meng Yutong Feng Prof. Chengxin Peng Feng Zhu Tianzi Hao Jiajia Ru Prof. Yonggang Wang Prof. Jinhu Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3161-3166
Incorporating nanoscale Si into a carbon matrix with high dispersity is desirable for the preparation of lithium-ion batteries (LIBs) but remains challenging. A space-confined catalytic strategy is proposed for direct superassembly of Si nanodots within a carbon (Si NDs⊂C) framework by copyrolysis of triphenyltin hydride (TPT) and diphenylsilane (DPS), where Sn atomic clusters created from TPT pyrolysis serve as the catalyst for DPS pyrolysis and Si catalytic growth. The use of Sn atomic cluster catalysts alters the reaction pathway to avoid SiC generation and enable formation of Si NDs with reduced dimensions. A typical Si NDs⊂C framework demonstrates a remarkable comprehensive performance comparable to other Si-based high-performance half LIBs, and higher energy densities compared to commercial full LIBs, as a consequence of the high dispersity of Si NDs with low lithiation stress. Supported by mechanic simulations, this study paves the way for construction of Si/C composites suitable for applications in future energy technologies. 相似文献
68.
等离子体破裂会对托卡马克装置的安全运行造成严重威胁.等离子体破裂期间电流猝灭速率与电磁负载的大小及逃逸电流平台的形成都密切相关.本文对HL-2A装置等离子体破裂进行了统计分析,统计选用等离子电流的两个衰减区间90%-10%和80%-20%.分析结果表明:HL-2A装置等离子体破裂有四种不同的电流猝灭波形,两个衰减区间最小电流猝灭时间的参数区分别为2.6 ms和2.2 ms,并且不同衰减区间下平均电流猝灭时间统计分布明显不同. 相似文献
69.
基于单相流体的概念,超临界流体的异常传热行为已经被研究很多年了,但是关于其流动传热机理仍没有统一的认识.本文通过理论分析和实验研究了超临界二氧化碳在竖直管内向上流动过程中,浮升力和流动加速效应对其流动结构和传热过程的影响.结果表明,没有确凿的实验证据表明超临界流体的异常传热行为是浮升力和流动加速直接导致的,存在的估计浮升力和流动加速效应准则均是在常物性流体的基础上,做了大量假设得出的,不同的研究者采用浮升力和流动加速准则分析超临界流体的传热恶化得出的结论不一致.最后,基于拟沸腾理论分析超临界流体的传热恶化过程,提出超临界沸腾数区分了超临界流体正常传热与恶化传热的转换边界,为超临界流体流动传热研究提供新思路,超临界沸腾数对建立用于不同技术的超临界流体动力循环的最佳运行条件具有重要意义. 相似文献
70.
Nonlinear Dynamics - Under investigation is a generalized (3 + 1)-dimensional variable- coefficient Kadomtsev– Petviashvili equation in fluid mechanics. Various exact analytical solutions are... 相似文献