全文获取类型
收费全文 | 3651篇 |
免费 | 73篇 |
国内免费 | 169篇 |
专业分类
化学 | 2163篇 |
晶体学 | 4篇 |
力学 | 18篇 |
综合类 | 1篇 |
数学 | 1010篇 |
物理学 | 697篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 49篇 |
2019年 | 63篇 |
2018年 | 5篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 27篇 |
2013年 | 324篇 |
2012年 | 328篇 |
2011年 | 446篇 |
2010年 | 400篇 |
2009年 | 500篇 |
2008年 | 405篇 |
2007年 | 310篇 |
2006年 | 251篇 |
2005年 | 141篇 |
2004年 | 114篇 |
2003年 | 102篇 |
2002年 | 42篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 26篇 |
1997年 | 42篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 27篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有3893条查询结果,搜索用时 0 毫秒
111.
Nickel‐Catalyzed C?H Alkylations: Direct Secondary Alkylations and Trifluoroethylations of Arenes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Weifeng Song Sebastian Lackner Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2014,53(9):2477-2480
A versatile nickel catalyst allowed for C H alkylations of unactivated arenes with challenging secondary alkyl bromides and chlorides. The high catalytic efficacy also set the stage for direct secondary alkylations of indoles as well as C H trifluoroethylations with ample substrate scope. 相似文献
112.
Joachim W. Heinicke Nidhi Gupta Peter Mayer Konstantin Karaghiosoff 《无机化学与普通化学杂志》2020,646(13):959-963
NH-Functional 1H-1,3-benzazaphospholes 1a–1c and o-chloranil (tetrachloro-o-benzoquinone - TCBQ) undergo rapid [1+4]-cycloaddition in a 1:2 molar ratio to give 2a – 2c as high-melting zwitterionic σ6λ5-phosphorus compounds. In the case of 2a the yield is high (rel. to TCBQ) even if the reactants were used in a 1:0.5 molar ratio. For the 2-tert-butyl-substituted compounds 2b and 2c the yields were significantly lower, in part by unidentified byproducts. Addition of excess TCBQ to crude 2c containing unconverted 1c did not increase but strongly decrease the amount of 2c . Crystallization and XRD analysis led to detection of a minor side or consecutive product 3c , formally corresponding to P=C bond cleavage and [1+4] cycloaddition of three equivalents TCBQ, two at the phosphinidene and one at the carbene end. NMR spectroscopic data of 2a – 2c including conclusive 13C data for 2a give evidence of the structures of the new compounds. 相似文献
113.
Bofeng Zhang Hong Zhang Jiahe Lin Xinlu Cheng 《International journal of quantum chemistry》2020,120(13):e26232
Recently, all-inorganic perovskite nanostructures have become a hot research topic due to their unique optical response and novel properties. Here, we theoretically study the optical response in Cs2PbX4 and CsPb2X5 (X = Cl, Br, and I) nanostructures. First, to study the ground state, we calculate the band structures of the periodic system using the HSE06 method, which shows that all those periodic perovskites possess the direct band gaps, with distribution from 2.225 to 3.536 eV. Their valence band maximum are mainly contributed from both halogen and lead atoms, while the conduction band minimum are mainly contributed from lead atoms. Then, we study the excited state using the time-dependent density functional theory method and find that, with the increase of halogen atom radius, the photogenerated carrier concentrations in perovskite nanostructures become larger, while the surface plasmon resonance becomes localized rather than long-range. Moreover, through the analysis of photocurrent and local field enhancement, Cs2PbX4 and CsPb2X5 nanostructures exhibit nearly 40 μA photocurrent along the direction of optical polarization. Besides, by regulating the different anions, we predict that field enhancement in Cs2PbI4 and CsPb2I5 share a much stronger distribution at both the center and border parts of Pb-I planes due to localized plasmon resonance, while other perovskites are distributed at the edge parts of Pb-I planes, caused by long-range plasmon resonance. Our research shows that all-inorganic perovskite nanostructures are great candidate materials for developing optoelectronic devices working in high-frequency and high-energy regions and improving their application in sensitive detection and sensors. 相似文献
114.
115.
116.
117.
Using Stuttgart/Dresden effective core potentials MWB28, MWB60, and GTO valence basis sets (8s7p6d)/[6s5p3d], (8s7p6d)/[6s5p3d]
for Zr and Hf atoms and 6-311++G(3df,3pd) basis set for C, H, O, and Ti atoms, tight convergence criteria geometry optimizations
and harmonic frequency calculations are performed at B3LYP and B3LYP/IEF-PCM levels of theory so as to model the gas phase
and argon matrix infrared spectra of the tetrahedral molecules R2MH2 (R = D(H), CH3, OH; M = Ti, Zr, Hf). Influence of the transition metal and/or substituent group on the symmetric and asymmetric stretching
frequencies of the MH2 fragment of the R2MH2 molecules is investigated at both the levels of theory. The modelling of the argon matrix effect improves the agreement between
the calculated frequencies and the experimental ones. The calculated argon matrix to gas phase frequency shifts is compared
reasonably to the experimental argon to neon matrix shifts. 相似文献
118.
MGa2O4(M=Zn,Ni) rods with similar crystallinity and BET surface area were prepared via a facile template-engaged reaction.The photocatalytic activities for water splitting of RuO2-loaded MGa2O4(M=Zn,Ni) were investigated under high-pressure Hg lamp.RuO2-loaded ZnGa2O4 catalyst exhibited much higher photocatalytic activity than RuO2-loaded NiGa2O4.Factors affecting the photocatalytic activities of RuO2-loaded MGa2O4(M=Zn,Ni) were discussed.It was suggested that the electronic structure of oxide semiconductor was a predominant factor of the photocatalytic behavior for RuO2-loaded MGa2O4(M=Zn,Ni). 相似文献
119.
120.