全文获取类型
收费全文 | 313篇 |
免费 | 4篇 |
国内免费 | 45篇 |
专业分类
化学 | 353篇 |
晶体学 | 1篇 |
力学 | 1篇 |
物理学 | 7篇 |
出版年
2023年 | 12篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 19篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 28篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 11篇 |
2007年 | 32篇 |
2006年 | 34篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有362条查询结果,搜索用时 93 毫秒
1.
甲烷热裂解制氢并生成高附加值的纳米碳材料,被认为是极具发展前景的氢气生产途径,但高性能催化剂的研发仍存在诸多挑战.我们选择多种载体(TS-1、 IM-5、 Y、介孔SiO2、 γ-Al2O3、 CNTs),采用浸渍法制备Ni-Cu负载催化剂,通过低温N2吸附-脱附、 XRD、 SEM和H2-TPR等系列表征方法对样品进行分析,考察不同载体对催化剂甲烷裂解制氢和纳米碳材料的影响.实验结果发现,分子筛载体独特的孔道结构有利于金属颗粒的分散,能有效避免反应中界面效应导致的催化剂失活,可提高催化剂反应活性并延长反应寿命,也显著提高了其碳产率.其中以IM-5分子筛为载体的催化剂表现最佳,在反应温度为700℃时, NiCu/IM-5催化剂甲烷转化率高达80%,氢气选择性达100%,反应400 min后活性未见明显降低. NiCu/IM-5催化剂碳产率高达1 446 gC/gcat,是NiCu/SiO2催化剂的5.7倍, NiCu/γ-Al 相似文献
2.
Catalytic Diastereo- and Enantioselective Cyclopropanation of gem-Dihaloalkanes and Terminal Olefins
Hou-Lu Liu Xinyu Wang Ke Gao Zhaobin Wang 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305987
Chiral cyclopropane derivatives are essential in synthetic chemistry and drug discovery. Their synthesis commonly relies on asymmetric cyclopropanation of diazo compounds, potentially explosive and needing stabilizing substituents. Thus, asymmetric catalytic transformations of non-stabilized carbenes or carbenoids remain a formidable challenge. Herein, we report the unprecedented chromium-catalyzed asymmetric cyclopropanation of readily available gem-dihaloalkanes and terminal olefins. Distinct from previous approaches, gem-dihaloalkanes serve as suitable precursors for non-stabilized carbenes or carbenoids, furnishing various functionalized chiral cyclopropanes. Mechanistic studies, including radical trapping, non-linear effect, and UV/Vis spectroscopy, provide insights into the catalytic process, featuring radical-polar crossover. 相似文献
3.
Mingming Peng Quanzheng Deng Yuhong Zhao Prof. Hao Xu Prof. Yejun Guan Dr. Jingang Jiang Prof. Lu Han Prof. Peng Wu 《Angewandte Chemie (International ed. in English)》2023,62(15):e202217004
A high-silica zeolite ECNU-13 (Si/Al=23) with a new three-dimensional (3D) pore system and a nanosized morphology has been developed, consisting of multitudes of 10-membered ring (10-R) medium pores and one set of 8-R small pores. A phase-discrimination strategy was proposed to synthesize ECNU-13 by regulating the gel compositions and nucleation processes that were used for preparing 12-R large-pore germanosilicate IM-20 with the known UWY topology. The crystallization was directed towards forming one set of single four-ring (s4r) composite building units together with one set of double four-ring (d4r) rather than two different types of d4r units in IM-20. The electron crystallographic investigations elucidated that the ECNU-13 structure was composed of two kinds of polymorphs as a result of distinct atomic positionings in s4r units. In catalytic cracking of 1-butene, ECNU-13 exhibited high propene selectivity (55.6 %) and propene to ethylene molar ratio (>4.7) superior to well-studied conventional ZSM-5 zeolite catalyst. 相似文献
4.
Yunchuan Pu Mingang Zhao Xu Liang Shaoyu Wang Dr. Hongjian Wang Ziting Zhu Dr. Yanxiong Ren Zhiming Zhang Prof. Guangwei He Prof. Dan Zhao Prof. Zhongyi Jiang 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302355
We report a covalent organic framework (COF) induced seeding strategy to fabricate metal–organic framework (MOF) membranes. Contrary to graphene oxide nuclei-depositing substrate, COF substrate has uniform pore size, high microporosity and abundant functional groups. We designed a series of charged COF nanosheets to induce the formation of ZIF-8@COF nanosheet seeds with high aspect ratio over 150, which were readily processed into a compact and uniform seed layer. The resulting ZIF-8 membranes with thickness down to 100 nm exhibit an ultrahigh C3H6/C3H8 separation performance and superior long-term stability. Our strategy is also validated by fabricating ultrathin ZIF-67 and UiO-66 membranes. 相似文献
5.
Jennifer M. StorvickEvgenia Ankoudinova Brianne R. KingHeather Van Epps Gregory W. O’Neil 《Tetrahedron letters》2011,52(44):5858-5861
The total synthesis of haminol A has been completed featuring a masked-alkene metathesis reaction followed by bis-acyloxysulfone elimination to install the 1,3,8-triene subunit. During the course of our synthesis, the metathesis reactivity of 3-vinylpyridine was evaluated and our data suggest the rapid formation of a ruthenium pyridylalkylidene that no longer participates in productive metathesis. A chemotaxis assay using Caenorhabditis elegans demonstrated that haminol A produced an avoidance response from this organism. 相似文献
6.
Ching‐Yao Chang 《中国化学会会志》2011,58(3):286-289
The first total synthesis of the linear diarylheptanoid 1‐(4″‐methoxyphenyl)‐7‐(4′‐hydroxyphenyl)‐(E)‐hept‐2‐ene, which has a uniquely nonconjugated olefin, was achieved. The synthetic route employed an olefin cross‐metathesis as a key step. Beginning with commercially available 3‐(4‐hydroxyphenyl)propan‐1‐ol, the final product was made in three steps with a 52% yield. 相似文献
7.
Mudassar AbbasChristian Slugovc 《Tetrahedron letters》2011,52(20):2560-2562
A series of ruthenium catalysts for olefin metathesis have been screened in the cross metathesis of 1,9-decadiene with ethyl acrylate. Under optimized reaction conditions a catalyst loading of only 100 ppm in respect to double bonds was sufficient for complete conversion of the diene. 相似文献
8.
N-杂环卡宾配体的优异催化性能引起了人们的广泛关注, 已成功应用于多种烯烃聚合反应。本文结合N-杂环卡宾的相关研究报道,首先简要介绍N-杂环卡宾,随后重点介绍N-杂环卡宾在开环易位聚合、烯烃配位聚合和原子转移自由基聚合等聚合反应的应用。在此基础上,指出了今后N-杂环卡宾配体在聚合反应研究的发展方向。 相似文献
9.
D.Y. Mikhaylov T.V. Gryaznova I.A. Litvinov O.G. Sinyashin 《Journal of organometallic chemistry》2009,694(24):3840-172
An efficient nickel-catalyzed method devoted to the direct addition of perfluoroalkyl halides (I, Br) to α-methylstyrene is described. This procedure allows for synthesis of compounds resulting from addition-dimerization in good yields. 相似文献
10.
Synthesis of siloxy-modified second generation Hoveyda-Grubbs catalysts and their catalytic activity
Szymon Rogalski 《Journal of organometallic chemistry》2009,694(24):3918-5077
Efficient syntheses of the first ruthenium alkylidene complexes bearing siloxide ligands are described. Second generation Hoveyda-Grubbs catalyst is shown to undergo efficient functionalization with a number of potassium silanolates to give disiloxy derivatives. The complexes obtained are found catalytically active in selected metathesis transformations. 相似文献