全文获取类型
收费全文 | 28007篇 |
免费 | 5232篇 |
国内免费 | 8741篇 |
专业分类
化学 | 21053篇 |
晶体学 | 1065篇 |
力学 | 2017篇 |
综合类 | 791篇 |
数学 | 3814篇 |
物理学 | 13240篇 |
出版年
2024年 | 35篇 |
2023年 | 352篇 |
2022年 | 893篇 |
2021年 | 908篇 |
2020年 | 1090篇 |
2019年 | 1046篇 |
2018年 | 927篇 |
2017年 | 1261篇 |
2016年 | 1230篇 |
2015年 | 1562篇 |
2014年 | 1843篇 |
2013年 | 2344篇 |
2012年 | 2337篇 |
2011年 | 2651篇 |
2010年 | 2425篇 |
2009年 | 2467篇 |
2008年 | 2659篇 |
2007年 | 2284篇 |
2006年 | 2302篇 |
2005年 | 2022篇 |
2004年 | 1492篇 |
2003年 | 1205篇 |
2002年 | 1137篇 |
2001年 | 1123篇 |
2000年 | 1046篇 |
1999年 | 621篇 |
1998年 | 349篇 |
1997年 | 279篇 |
1996年 | 281篇 |
1995年 | 231篇 |
1994年 | 239篇 |
1993年 | 212篇 |
1992年 | 225篇 |
1991年 | 108篇 |
1990年 | 133篇 |
1989年 | 106篇 |
1988年 | 104篇 |
1987年 | 85篇 |
1986年 | 81篇 |
1985年 | 52篇 |
1984年 | 44篇 |
1983年 | 51篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 34篇 |
1978年 | 6篇 |
1959年 | 9篇 |
1957年 | 7篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Li‐Na Wang Zhen‐Xun Zhou Dr. Xiao‐Na Li Dr. Tong‐Mei Ma Prof. Sheng‐Gui He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6957-6961
In addition to generation of a methyl radical, formation of a formaldehyde molecule was observed in the thermal reaction of methane with AuNbO3+ heteronuclear oxide cluster cations. The clusters were prepared by laser ablation and mass‐selected to react with CH4 in an ion‐trap reactor under thermal collision conditions. The reaction was studied by mass spectrometry and DFT calculations. The latter indicated that the gold atom promotes formaldehyde formation through transformation of an Au?O bond into an Au?Nb bond during the reaction. 相似文献
82.
基于熵理论,分析了森林生态系统类自然保护区区域系统的熵变机理,构建了该类保护区区域森林生态系统熵变状态转移模型,运用模型可以反映系统的发展状况并进一步确定影响其发展的关键协同因子.以云南省大围山国家级森林生态系统类自然保护区为例介绍了模型的具体运用,并证实了模型的合理性,从而为实现此类保护区的可持续发展提供新的战略思想. 相似文献
83.
84.
m‐Methoxy Substituents in a Tetraphenylethylene‐Based Hole‐Transport Material for Efficient Perovskite Solar Cells 下载免费PDF全文
Dr. Fei Wu Jianlin Liu Gang Wang Prof. Qunliang Song Dr. Linna Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16636-16641
Three tetrapheynlethylene derivatives (N,N‐di(4‐methoxyphenyl)aminophenyl‐substituted tetraphenylethylene; TPE‐4DPA) with different methoxy positions (pp‐, pm‐, and po‐) have been synthesized and characterized. The methoxy groups can control the oxidation potential of the materials, and the electronic properties of the derivatives were affected by the position of the methoxy substituents. These compounds were synthesized in a facile and cost‐effective way, and were applied as hole‐transport materials in perovskite solar cells. The corresponding cell performances were compared with respect to their structure modifications, and it was found that the derivative with m‐OMe substituents showed the highest power conversion efficiency (PCE) of 15.4 %, with a Jsc value of 20.04 mA cm?2, a Voc value of 1.07 V, and a fill factor (FF) value of 0.72, which is higher than the p‐OMe and o‐OMe substituents. Moreover, the PCE of pm‐TPE‐4DPA is comparable with that of the state‐of‐the‐art 2,2′,7,7′‐tetrakis(N,N′‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene under identical conditions. 相似文献
85.
86.
87.
88.
High‐Nuclear Organometallic Copper(I)–Alkynide Clusters: Thermochromic Near‐Infrared Luminescence and Solution Stability 下载免费PDF全文
Hong‐Yan Zhuo Dr. Hai‐Feng Su Zhao‐Zhen Cao Wei Liu Prof. Shu‐Ao Wang Lei Feng Dr. Gui‐Lin Zhuang Dr. Shui‐Chao Lin Prof. Mohamedally Kurmoo Prof. Chen‐Ho Tung Dr. Di Sun Prof. Lan‐Sun Zheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17619-17626
Cu(CF3COO)2 reacts with tert‐butylacetylene (tBuC≡CH) in methanol in the presence of metallic copper powder to give two air‐stable clusters, [CuI15(tBuC≡C)10(CF3COO)5]?tBuC≡CH ( 1 ) and [CuI16(tBuC≡C)12(CF3COO)4(CH3OH)2] ( 2 ). The assembly process involves in situ comproportionation reaction between Cu2+ and Cu0 and the formation of two different clusters is controlled by reactants concentration. The clusters consist of Cu15 and Cu16 cores co‐stabilized by strong by σ‐ and π‐bonded tert‐butylethynide and CF3COO? (together with methanol molecule in 2 ). Their stabilities in solution were confirmed using electrospray ionization mass spectrometry in which the cluster core remains intact for 1 in chloroform and acetone, and for 2 in acetonitrile. Strong thermochromic luminescence in the near infrared (NIR) region was observed in the solid‐state. Of particular interest, the emission maximum of 1 is red‐shifted from 710 nm at 298 K to 793 nm at 93 K, along with a 17‐fold fluorescence enhancement. In contrast, 2 exhibits red shift from 298 to 123 K followed by blue shift from 123 to 93 K. The emission wavelength was correlated with the structural parameters using variable‐temperature X‐ray single‐crystal analyses. The rich cuprophilic interaction plays a significant role in the formation of 3LMCT (tBuC≡C→Cux) excited state mixed with cluster‐centered (3CC) characters, which can be considerably influenced by temperature, leading to thermochromic luminescence. The present work provides 1) a new synthetic protocol for the high‐nuclear CuI–alkynyl clusters; 2) a comprehensive insight into the mechanism of thermochromic luminescence; 3) unusual emissive materials with the characters of NIR and thermochromic luminescence simultaneously. 相似文献
89.
90.