全文获取类型
收费全文 | 1995篇 |
免费 | 143篇 |
国内免费 | 421篇 |
专业分类
化学 | 2286篇 |
晶体学 | 20篇 |
力学 | 11篇 |
综合类 | 20篇 |
数学 | 2篇 |
物理学 | 220篇 |
出版年
2023年 | 29篇 |
2022年 | 39篇 |
2021年 | 60篇 |
2020年 | 101篇 |
2019年 | 71篇 |
2018年 | 51篇 |
2017年 | 56篇 |
2016年 | 72篇 |
2015年 | 71篇 |
2014年 | 72篇 |
2013年 | 209篇 |
2012年 | 118篇 |
2011年 | 102篇 |
2010年 | 89篇 |
2009年 | 87篇 |
2008年 | 95篇 |
2007年 | 100篇 |
2006年 | 84篇 |
2005年 | 105篇 |
2004年 | 86篇 |
2003年 | 84篇 |
2002年 | 73篇 |
2001年 | 50篇 |
2000年 | 51篇 |
1999年 | 44篇 |
1998年 | 49篇 |
1997年 | 42篇 |
1996年 | 43篇 |
1995年 | 28篇 |
1994年 | 33篇 |
1993年 | 30篇 |
1992年 | 33篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 9篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1973年 | 8篇 |
1972年 | 7篇 |
排序方式: 共有2559条查询结果,搜索用时 15 毫秒
1.
Ajay Gupta Fillip Kumar Sarkar Rajib Sarkar Ramen Jamatia Chang Yeon Lee Gajendra Gupta Amarta Kumar Pal 《应用有机金属化学》2020,34(9):e5782
Magnetically retrieval CuFe2O4@MIL-101(Cr) metal–organic framework was successfully prepared from easily available starting materials and characterized using various spectroscopic and analytical techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, elemental mapping, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, vibrating sample magnetometer, and inductively coupled plasma optical emission spectroscopy. The catalyst was then used in the synthesis of benzodiazepines containing a triazole moiety in water. The advantages of this protocol include high yields, reusability of the catalyst, and gram-scale synthesis. 相似文献
2.
A variety of heterobiaryl compounds have been synthesized by the Suzuki‐Miyaura coupling reactions of heteroaryl halides with potassium aryltrifluoroborates. Pd (OAc)2 was found to be highly efficient for the Suzuki‐Miyaura coupling reactions of various heteroaryl halides with potassium aryltrifluoroborates in aqueous systems, delivering the corresponding heterobiaryl compounds in good to excellent yields. 相似文献
3.
Dr. Soichiro Ogi Natsumi Fukaya Dr. Arifin Bastian Bjerkem Skjelstad Dr. Yuh Hijikata Prof. Dr. Shigehiro Yamaguchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(30):7303-7307
The self-assembly of an amide-functionalized dithienyldiketopyrrolopyrrole (DPP) dye in aqueous media was achieved through seed-initiated supramolecular polymerization. Temperature- and time-dependent studies showed that the spontaneous polymerization of the DPP derivative was temporally delayed upon cooling the monomer solution in a methanol/water mixture. Theoretical calculations revealed that an amide-functionalized DPP derivative adopts an energetically favorable folded conformation in the presence of water molecules due to hydration. This conformational change is most likely responsible for the trapping of monomers in the initial stage of the cooperative supramolecular polymerization in aqueous media. However, the monomeric species can selectively interact with externally added fragmented aggregates as seeds through concerted π-stacking and hydrogen-bonding interactions. Consequently, the time course of the supramolecular polymerization and the morphology of the aggregated state can be controlled, and one-dimensional fibers that exhibit a J-aggregate-like bathochromically shifted absorption band can be obtained. 相似文献
4.
5.
Electrospun Nanofibers from a Tricyanofuran‐Based Molecular Switch for Colorimetric Recognition of Ammonia Gas 下载免费PDF全文
Dr. Tawfik A. Khattab Dr. Sherif Abdelmoez Prof. Dr. Thomas M. Klapötke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4157-4163
A chromophore based on tricyanofuran (TCF) with a hydrazone (H) recognition moiety was developed. Its molecular‐switching performance is reversible and has differential sensitivity towards aqueous ammonia at comparable concentrations. Nanofibers were fabricated from the TCF–H chromophore by electrospinning. The film fabricated from these nanofibers functions as a solid‐state optical chemosensor for probing ammonia vapor. Recognition of ammonia vapor occurs by proton transfer from the hydrazone fragment of the chromophore to the ammonia nitrogen atom and is facilitated by the strongly electron withdrawing TCF fragment. The TCF–H chromophore was added to a solution of poly(acrylic acid), which was electrospun to obtain a nanofibrous sensor device. The morphology of the nanofibrous sensor was determined by SEM, which showed that nanofibers with a diameter range of 200–450 nm formed a nonwoven mat. The resultant nanofibrous sensor showed very good sensitivity in ammonia‐vapor detection. Furthermore, very good reversibility and short response time were also observed. 相似文献
6.
A one‐pot, multistep synthesis of acridine‐1,8(2H,5H)‐diones ( 4a–m ) was achieved by three‐component reaction of dimedone ( 1 ) with an aromatic aldehyde ( 2a–m ) and an ammonium acetate ( 3 ) using water as a green solvent without any catalyst and a simple, easily handled, and ultrasonic technique as well as conventional method. 相似文献
7.
Dr. Jun Wang Jaeyoung Heo Dr. Changqiang Chen Dr. Andrew J. Wilson Prof. Prashant K. Jain 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18588-18592
We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon resonances. Under visible-light excitation, this catalyst exhibits enhanced electrochemical ammonia oxidation kinetics, outperforming previously reported electrochemical schemes. We trace the enhancement to a photochemical potential resulting from electron–hole carriers generated in the electrocatalyst by plasmonic excitation. The photopotential responsible for enhanced kinetics scales linearly with the light intensity—a general design principle for eliciting superlative photoelectrochemical performance from catalysts comprised of plasmonic metals or hybrids. We also determine a photochemical conversion coefficient. 相似文献
8.
Dr. Andrew Ballard Dr. Stefania Narduolo Dr. Hiwa O. Ahmed Nathaniel I. Keymer Dr. Nabil Asaad Dr. David A. Cosgrove Dr. Niklaas J. Buurma Dr. Andrew G. Leach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3661-3687
The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented. 相似文献
9.
Young Eun Jeun Joon Ho Park Joo Yeon Kim Prof. Hyun S. Ahn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(18):4039-4043
Mixed-metal oxyhydroxides—especially those of Ni and Fe—are one of the most active classes of materials known for catalyzing the oxygen evolution reaction (OER). Here, nanoparticulate mixed metal oxyhydroxides (of Ni, Fe, and Co) were prepared on an electrode surface by electrochemical reaction of a precursor solution encapsulated in aqueous nanodroplets (AnDs), with each of the droplets containing 10 s of attoliters of fluid. Electrode reactions and synthesis can be monitored in situ by electrochemistry as single AnD stochastically lands and interacts with the working electrode. Resultant metal oxyhydroxide nanoparticles can be size and composition controlled precisely by modulating the precursor solution stored in the AnD. Nanoparticulate metal oxyhydroxides were implemented as catalysts for the OER and exhibited superior catalysis compared to their thin-film counterparts, demonstrating a hundred-thousand-fold enhancement in atom efficiency at comparable turnover rates. 相似文献
10.
Yuwei Wang Jia-Jun Yan Shengnan Hu Prof. David James Young Prof. Hong-Xi Li Prof. Zhi-Gang Ren 《化学:亚洲杂志》2021,16(18):2681-2686
A photoluminescent bimetallic cluster [Ag10Cu6(bdppthi)2(C≡CPh)12(MeOH)2(H2O)](ClO4)4 ( 1 , bdppthi=N,N’-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH3 in air or water. The sensing of NH3 was rapid and recoverable, with detection limits of 53 ppm (v/v) in N2 and 21 μmol/L (0.36 ppm, w/w) for NH3 ⋅ H2O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water. 相似文献