全文获取类型
收费全文 | 132716篇 |
免费 | 2797篇 |
国内免费 | 1205篇 |
专业分类
化学 | 74043篇 |
晶体学 | 2156篇 |
力学 | 5426篇 |
综合类 | 77篇 |
数学 | 12878篇 |
物理学 | 42138篇 |
出版年
2020年 | 1022篇 |
2019年 | 957篇 |
2016年 | 1681篇 |
2015年 | 1380篇 |
2014年 | 1837篇 |
2013年 | 5371篇 |
2012年 | 4027篇 |
2011年 | 5060篇 |
2010年 | 3181篇 |
2009年 | 2871篇 |
2008年 | 4408篇 |
2007年 | 4387篇 |
2006年 | 4396篇 |
2005年 | 4271篇 |
2004年 | 3658篇 |
2003年 | 3359篇 |
2002年 | 3212篇 |
2001年 | 3687篇 |
2000年 | 2817篇 |
1999年 | 2339篇 |
1998年 | 2011篇 |
1997年 | 1994篇 |
1996年 | 1950篇 |
1995年 | 1878篇 |
1994年 | 1651篇 |
1993年 | 1621篇 |
1992年 | 1831篇 |
1991年 | 1813篇 |
1990年 | 1748篇 |
1989年 | 1730篇 |
1988年 | 1731篇 |
1987年 | 1710篇 |
1986年 | 1623篇 |
1985年 | 2161篇 |
1984年 | 2282篇 |
1983年 | 1902篇 |
1982年 | 2226篇 |
1981年 | 2042篇 |
1980年 | 2082篇 |
1979年 | 2064篇 |
1978年 | 2187篇 |
1977年 | 2092篇 |
1976年 | 2117篇 |
1975年 | 2058篇 |
1974年 | 1900篇 |
1973年 | 2102篇 |
1972年 | 1285篇 |
1971年 | 977篇 |
1968年 | 1052篇 |
1967年 | 1102篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Unsymmetrical Pyrene‐Fused Phthalocyanine Derivatives: Synthesis,Structure, and Properties 下载免费PDF全文
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
2.
Mechanistic Aspects of a Highly Active Dinuclear Zinc Catalyst for the Co‐polymerization of Epoxides and CO2 下载免费PDF全文
Stefan Kissling Peter T. Altenbuchner Dr. Maximilian W. Lehenmeier Dr. Eberhardt Herdtweck Dr. Peter Deglmann Dr. Uwe B. Seemann Prof. Dr. Bernhard Rieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8148-8157
The dinuclear zinc complex reported by us is to date the most active zinc catalyst for the co‐polymerization of cyclohexene oxide (CHO) and carbon dioxide. However, co‐polymerization experiments with propylene oxide (PO) and CO2 revealed surprisingly low conversions. Within this work, we focused on clarification of this behavior through experimental results and quantum chemical studies. The combination of both results indicated the formation of an energetically highly stable intermediate in the presence of propylene oxide and carbon dioxide. A similar species in the case of cyclohexene oxide/CO2 co‐polymerization was not stable enough to deactivate the catalyst due to steric repulsion. 相似文献
3.
4.
5.
6.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
7.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors 下载免费PDF全文
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
8.
9.
10.
Cover Picture: Coordination Chemistry of N‐Heterocyclic Nitrenium‐Based Ligands (Chem. Eur. J. 19/2015) 下载免费PDF全文