全文获取类型
收费全文 | 298篇 |
免费 | 32篇 |
国内免费 | 50篇 |
专业分类
化学 | 329篇 |
晶体学 | 2篇 |
综合类 | 2篇 |
数学 | 1篇 |
物理学 | 46篇 |
出版年
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 16篇 |
2020年 | 21篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有380条查询结果,搜索用时 46 毫秒
81.
采用微波等离子体技术研究了一氧化碳氢化制乙炔反应的产物选择性。对影响乙炔选择性的几个因素,如微波输入功率、反应物的比例和体系压力进行了研究。乙炔的选择性随着微波输入功率的增加,反应物比例和体系压力的降低而增大。在最佳条件下,乙炔的选择性可达到95.87%,甲烷选择性的变化规律和乙炔相反,乙烯和乙烷的选择性很低。等离子体中的电子温度(或能量)和密度采用了静电悬浮双探针诊断,电子密度和能量受微波输入功率和体系压力的影响。在反应中,电子能量决定化学反应是否进行,电子密度决定产物的组成。根据自由基反应理论解释了乙炔选择性在H2+CO等离子体化学反应中随影响因素的变化规律。 相似文献
82.
Yibo WU Fuxiang LI Qingbin LI Songtian LI Ganqing ZHAO Xuerong SUN Peisong LIU Guoxv HE Yongjun HAN Liping CHENG Shiying LUO 《Turkish Journal of Chemistry》2021,45(5):1463
The catalysts comprising the main active compounds of Sn-Nx were synthesized using trichlorophenylstannane ((C6H5)Cl3Sn), nitrogen carbon-dots (NCDs), and activated carbon (AC) as starting materials, and the activity and stability of catalysts was evaluated in the acetylene hydrochlorination. According to the results on the physical and chemical properties of catalysts (TEM, XRD, BET, XPS and TG), it is concluded that NCDs@AC can increase (C6H5)Cl3Sn dispersity, retard the coke deposition of (C6H5)Cl3Sn/AC and lessen the loss of (C6H5)Cl3Sn, thereby further promoting the stability of (C6H5)Cl3Sn/AC. Based on the characterization results of C2H2-TPD and HCl adsorption experiments, we proposed that the existence of Sn-Nx can effectively strengthen the reactants adsorption of catalysts. By combing the FT-IR, C2H2-TPD and Rideal-Eley mechanism, the catalytic mechanism, in which C2H2 is firstly adsorbed on (C6H5)Cl3Sn to form (C6H5)Cl3Sn-C2H2 and then reacted with HCl to produce vinyl chloride, is proposed. 相似文献
83.
Polymerization of N-carbazolylacetylene by various transition metal catalysts and polymer properties
Tomoaki Sata Ryoji Nomura Tatsuo Wada Hiroyuki Sasabe Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》1998,36(14):2489-2492
N-Carbazolylacetylene (CzA) was polymerized in the presence of various transition metal catalysts including WCl6, MoCl5, [Rh(NBD)Cl]2, and Fe(acac)3 to give polymers in good yields. The polymers produced with W catalysts were dark purple solids and soluble in organic solvents such as toluene, chloroform, etc. The highest weight-average molecular weight of poly(CzA) reached about 4 × 104. In the UV–visible spectrum in CHCl3, poly(CzA) exhibited an absorption maximum around 550 nm (εmax = 4.0 × 103 M−1 cm−1) and the cutoff wavelength was 740 nm, showing a large red shift compared with that of poly(phenylacetylene) [poly(PA)]. Poly(CzA) began to lose weight in TGA under air at 310°C, being thermally more stable than poly(PA) and poly[3-(N-carbazolyl)-1-propyne]. Poly(CzA) showed a third-order susceptibility of 18 × 10−12 esu, which was 2 orders larger than that of poly(PA). © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2489–2492, 1998 相似文献
84.
Dr. Yueqiang Cao Hao Zhang Dr. Shufang Ji Prof. Zhijun Sui Prof. Zheng Jiang Prof. Dingsheng Wang Prof. Francisco Zaera Prof. Xinggui Zhou Prof. Xuezhi Duan Prof. Yadong Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11744-11749
Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory-guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi-hydrogenation processes. Such Ni sites show not only preferential acetylene π-adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, including aberration-corrected high-resolution scanning transmission electron microscopy and X-ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni5Ga3 intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi-atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation. 相似文献
85.
86.
87.
I. V. Magedov N. M. Przheval’skii D. S. Yufit V. N. Droza 《Russian Chemical Bulletin》1997,46(4):759-763
The reaction of thiocarbonyl ylides with activated acetylene derivatives gives (E,E)-divinyl sulfides in good yields. The reaction mechanism is discussed and evidence in favor of the formation of a thiirane
intermediate is presented.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 791–795, April, 1997. 相似文献
88.
Separation of Acetylene from Carbon Dioxide and Ethylene by a Water‐Stable Microporous Metal–Organic Framework with Aligned Imidazolium Groups inside the Channels 下载免费PDF全文
Jaechul Lee Chong Yang Chuah Prof. Jaheon Kim Youngsuk Kim Nakeun Ko Younggyu Seo Prof. Kimoon Kim Prof. Tae Hyun Bae Prof. Eunsung Lee 《Angewandte Chemie (International ed. in English)》2018,57(26):7869-7873
Separation of acetylene from carbon dioxide and ethylene is challenging in view of their similar sizes and physical properties. Metal–organic frameworks (MOFs) in general are strong candidates for these separations owing to the presence of functional pore surfaces that can selectively capture a specific target molecule. Here, we report a novel 3D microporous cationic framework named JCM‐1 . This structure possesses imidazolium functional groups on the pore surfaces and pyrazolate as a metal binding group, which is well known to form strong metal‐to‐ligand bonds. The selective sorption of acetylene over carbon dioxide and ethylene in JCM‐1 was successfully demonstrated by equilibrium gas adsorption analysis as well as dynamic breakthrough measurement. Furthermore, its excellent hydrolytic stability makes the separation processes highly recyclable without a substantial loss in acetylene uptake capacity. 相似文献
89.
Yun‐Lei Peng Dr. Tony Pham Pengfei Li Ting Wang Prof. Yao Chen Prof. Kai‐Jie Chen Dr. Katherine A. Forrest Prof. Brian Space Prof. Peng Cheng Dr. Michael J. Zaworotko Prof. Zhenjie Zhang 《Angewandte Chemie (International ed. in English)》2018,57(34):10971-10975
Highly selective separation and/or purification of acetylene from various gas mixtures is a relevant and difficult challenge that currently requires costly and energy‐intensive chemisorption processes. Two ultramicroporous metal–organic framework physisorbents, NKMOF‐1‐M (M=Cu or Ni), offer high hydrolytic stability and benchmark selectivity towards acetylene versus several gases at ambient temperature. The performance of NKMOF‐1‐M is attributed to their exceptional acetylene binding affinity as revealed by modelling and several experimental studies: in situ single‐crystal X‐ray diffraction, FTIR, and gas mixture breakthrough tests. NKMOF‐1‐M exhibit better low‐pressure uptake than existing physisorbents and possesses the highest selectivities yet reported for C2H2/CO2 and C2H2/CH4. The performance of NKMOF‐1‐M is not driven by the same mechanism as current benchmark physisorbents that rely on pore walls lined by inorganic anions. 相似文献
90.