全文获取类型
收费全文 | 1133篇 |
免费 | 63篇 |
国内免费 | 50篇 |
专业分类
化学 | 1087篇 |
晶体学 | 12篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 1篇 |
物理学 | 137篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 15篇 |
2020年 | 33篇 |
2019年 | 34篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 41篇 |
2013年 | 133篇 |
2012年 | 54篇 |
2011年 | 53篇 |
2010年 | 39篇 |
2009年 | 45篇 |
2008年 | 51篇 |
2007年 | 60篇 |
2006年 | 48篇 |
2005年 | 64篇 |
2004年 | 80篇 |
2003年 | 60篇 |
2002年 | 30篇 |
2001年 | 24篇 |
2000年 | 24篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 19篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 20篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
51.
Chen Sun Ya‐Hui Guo Sha‐Sha Han Jing‐Zhao Li Kuan Jiang Lin‐Feng Dong Qi‐Long Liu Cheng‐Yang Yue Xiao‐Wu Lei 《Angewandte Chemie (International ed. in English)》2020,59(38):16465-16469
Considering the instability and low photoluminescence quantum yield (PLQY) of blue‐emitting perovskites, it is still challenging and attractive to construct single crystalline hybrid lead halides with highly stable and efficient blue light emission. Herein, by rationally introducing d10 transition metal into single lead halide as new structural building unit and optical emitting center, we prepared a bimetallic halide of [(NH4)2]CuPbBr5 with new type of three‐dimensional (3D) anionic framework. [(NH4)2]CuPbBr5 exhibits strong band‐edge blue emission (441 nm) with a high PLQY of 32 % upon excitation with UV light. Detailed photophysical studies indicate [(NH4)2]CuPbBr5 also displays broadband red light emissions derived from self‐trapped states. Furthermore, the 3D framework features high structural and optical stabilities at extreme environments during at least three years. To our best knowledge, this work represents the first 3D non‐perovskite bimetallic halide with highly efficient and stable blue light emission. 相似文献
52.
Addition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the corresponding vicinal dihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25-60 °C) with excellent to moderate yields. 相似文献
53.
甲壳素-壳聚糖对皂土悬浮液的絮凝 总被引:3,自引:0,他引:3
研究了三种摩尔质量大体相同而脱乙酰度分别为93%、78%和62%的甲壳素-壳聚糖在pH=3~6范围内对皂土悬浮液的絮凝性质, 并与非离子型絮凝剂聚丙烯酰胺作了比较, 证明含自由氨基的甲壳素-壳聚糖在酸性溶液中形成阳离子聚电解质后. 对带负电的皂土悬浮颗粒有很好的絮凝能力. 通过对上述三种聚合物的絮凝能力、在皂土颗粒表面的吸附量等测定, 认为絮凝中桥连机制起了主导作用, 但聚合物所带正电荷则有利于被皂土颗粒所吸附, 电中和还降低了颗粒间的静电排斥, 这都对桥连絮凝起了促进作用. 聚丙烯酰胺分子在水中不带电, 故当介质pH升高使皂土颗粒双电层变厚时, 絮凝能力迅速下降. 相似文献
54.
Several quaternary alkyl halides were synthesized from dimeric tropane alkaloids - and -scopodonnines, which were prepared by dimerization of hyoscine. Their pharmacologic activities were studied. 相似文献
55.
56.
F
A1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing
tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using
ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical
conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical
rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions,
and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be
dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO
and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect
free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate
interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the
K+ site of the KCl and KBr (100) surfaces and on KBr relative to KCl.
相似文献
57.
Nano‐silica supported ionic liquids composed of alkyl carbon chain and transition metal chlorides anions have been prepared and successfully applied as a heterogeneous catalyst in the direct aldehyde C‐H activation. Catalytic results indicated that nano‐SiO2 supported ionic liquid consisting C12 alkyl carbon chain and CoCl3 anion nano‐SiO2@CoCl3‐C12IL showed excellent catalytic properties with good to excellent yields towards the desired aryl ketones. The excellent recyclability of the supported catalyst, mild reaction conditions, low catalyst loading, and operational simplicity are the important features of this methodology. 相似文献
58.
Simon Graßl Clémence Hamze Thaddäus J. Koller Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3752-3755
(Hetero)aryl, benzylic, and alkyl zinc halides were thiolated with N-thiophthalimides at 25 °C within 1 h in the presence of 5–10 % Cu(OAc)2 ⋅ H2O to furnish the corresponding polyfunctionalized thioethers in good yields. This electrophilic thiolation was extended to the introduction of trifluoromethylthio (SCF3), thiocyanate (SCN), and selenophenyl (SePh) groups. The utility of this method was shown in a seven-step synthesis of a potent cathepsin D inhibitor in 34 % overall yield. 相似文献
59.
Dr. Jie Ke Hongling Wang Dr. Liejin Zhou Chengli Mou Jingjie Zhang Prof. Dr. Lutai Pan Prof. Dr. Yonggui Robin Chi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(28):6911-6914
A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu3N/Et3N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale. 相似文献