全文获取类型
收费全文 | 42281篇 |
免费 | 6953篇 |
国内免费 | 4686篇 |
专业分类
化学 | 28936篇 |
晶体学 | 481篇 |
力学 | 2749篇 |
综合类 | 341篇 |
数学 | 4978篇 |
物理学 | 16435篇 |
出版年
2024年 | 164篇 |
2023年 | 876篇 |
2022年 | 1561篇 |
2021年 | 1624篇 |
2020年 | 1624篇 |
2019年 | 1624篇 |
2018年 | 1467篇 |
2017年 | 1393篇 |
2016年 | 2015篇 |
2015年 | 1971篇 |
2014年 | 2397篇 |
2013年 | 3208篇 |
2012年 | 3766篇 |
2011年 | 3910篇 |
2010年 | 2624篇 |
2009年 | 2545篇 |
2008年 | 2698篇 |
2007年 | 2443篇 |
2006年 | 2128篇 |
2005年 | 1814篇 |
2004年 | 1423篇 |
2003年 | 1108篇 |
2002年 | 1024篇 |
2001年 | 854篇 |
2000年 | 837篇 |
1999年 | 876篇 |
1998年 | 735篇 |
1997年 | 680篇 |
1996年 | 669篇 |
1995年 | 607篇 |
1994年 | 534篇 |
1993年 | 454篇 |
1992年 | 398篇 |
1991年 | 342篇 |
1990年 | 319篇 |
1989年 | 259篇 |
1988年 | 188篇 |
1987年 | 163篇 |
1986年 | 132篇 |
1985年 | 131篇 |
1984年 | 91篇 |
1983年 | 66篇 |
1982年 | 57篇 |
1981年 | 30篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1957年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Journal of Solid State Electrochemistry - Hydroxide precursor Ni0.5Co0.2Mn0.3(OH)2 was successfully prepared by co-precipitation using lactic acid as the environment-friendly chelating agent. And... 相似文献
952.
953.
A novel perylene tetracarboxylic acid bisimide(PTCBI) in-chain polyethylene(PE) was first prepared via acyclic diene metathesis(ADMET) polymerization of PTCBI-functionalized α,ω-diene monomer. The polymers could spontaneously self-assemble into hollow cylindrical structures in which the π-π interaction between adjacent PTCBI moieties was enhanced and the electron mobility was possibly promoted. The hydrogenation of as-obtained polymer was readily accomplished, affording the desired precision PTCBI in-chain PE with a saturated backbone, which showed high glass transition temperature(Tg = 63 °C), relatively wide range of light absorption(λ = 200-575 nm), and higher LUMO level(-3.62 e V). It can therefore serve as a superior model for facile construction of functional polyolefin and soluble PTCBI polymer with ordered architecture. 相似文献
954.
Bergman cyclization has shown great promise in constructing conjugated polymers.However,the application of this reaction in polymer science is still limited due to the harsh reaction condition and ill-defined structure of the achieved polymers.To this end,the cycloaromatization polymerization of enediynes catalyzed by a series of transition metal catalysts is investigated in this work,by taking advantage of the coordination chemistry of the enediyne with the transition metal complexes.According to the nuclear magnetic resonance (NMR),Fourier transform infrared (FTIR),ultraviolet-visble (UV-Vis) spectroscopies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis,the cycloaromatization polymerization of enediynes proceeds under milder conditions and in a more controlled manner in the presence of palladium(Ⅱ) complexes,giving structurally regulated conjugated polymers in high yields. 相似文献
955.
956.
957.
958.
Prof. Dr. Shaodong Zhou Dr. Xiaoyan Sun Dr. Lei Yue Dr. Maria Schlangen Prof. Dr. Helmut Schwarz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):2967-2971
The thermal gas-phase reactions of [Al2VO5]+ and [AlV2O6]+ with methane have been explored by using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry complemented by high-level quantum chemical calculations. Both cluster ions chemisorbed methane as the major reaction channels at room temperature. [Al2VO5]+ could break only one C−H bond to liberate CH3, whereas [AlV2O6]+ exhibited higher oxidizing ability such that it brings about the selective generation of formaldehyde. Mechanistic aspects are revealed and the crucial roles of the metal centers are discussed. 相似文献
959.
Dr. Carlos Sánchez-Sánchez Dr. Thomas Dienel Dr. Adrien Nicolaï Dr. Neerav Kharche Dr. Liangbo Liang Colin Daniels Prof. Vincent Meunier Dr. Junzhi Liu Prof. Xinliang Feng Prof. Klaus Müllen Dr. Juan Ramón Sánchez-Valencia Dr. Oliver Gröning Dr. Pascal Ruffieux Prof. Roman Fasel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12074-12082
A bottom up method for the synthesis of unique tetracene-based nanoribbons, which incorporate cyclobutadiene moieties as linkers between the acene segments, is reported. These structures were achieved through the formal [2+2] cycloaddition reaction of ortho-functionalized tetracene precursor monomers. The formation mechanism and the electronic and magnetic properties of these nanoribbons were comprehensively studied by means of a multitechnique approach. Ultra-high vacuum scanning tunneling microscopy showed the occurrence of metal-coordinated nanostructures at room temperature and their evolution into nanoribbons through formal [2+2] cycloaddition at 475 K. Frequency-shift non-contact atomic force microscopy images clearly proved the presence of bridging cyclobutadiene moieties upon covalent coupling of activated tetracene molecules. Insight into the electronic and vibrational properties of the so-formed ribbons was obtained by scanning tunneling microscopy, Raman spectroscopy, and theoretical calculations. Magnetic properties were addressed from a computational point of view, allowing us to propose promising candidates to magnetic acene-based ribbons incorporating four-membered rings. The reported findings will increase the understanding and availability of new graphene-based nanoribbons with high potential in future spintronics. 相似文献
960.
Liu Xiaoping Tan Xiaobin Zhou Yuemin Li Yiqun Zhang Zhubao 《Research on Chemical Intermediates》2019,45(6):3359-3378
Research on Chemical Intermediates - Copper nanoparticles assembled on carboxymethylcellulose (Cu0NPs@CMC) were successfully synthesized and well characterized by FT-IR, SEM, EDS, TEM, XPS, and... 相似文献