全文获取类型
收费全文 | 20098篇 |
免费 | 3304篇 |
国内免费 | 3907篇 |
专业分类
化学 | 15550篇 |
晶体学 | 519篇 |
力学 | 926篇 |
综合类 | 385篇 |
数学 | 2689篇 |
物理学 | 7240篇 |
出版年
2024年 | 45篇 |
2023年 | 259篇 |
2022年 | 588篇 |
2021年 | 643篇 |
2020年 | 755篇 |
2019年 | 776篇 |
2018年 | 624篇 |
2017年 | 762篇 |
2016年 | 872篇 |
2015年 | 984篇 |
2014年 | 1179篇 |
2013年 | 1533篇 |
2012年 | 1797篇 |
2011年 | 1849篇 |
2010年 | 1541篇 |
2009年 | 1510篇 |
2008年 | 1748篇 |
2007年 | 1497篇 |
2006年 | 1395篇 |
2005年 | 1139篇 |
2004年 | 860篇 |
2003年 | 716篇 |
2002年 | 864篇 |
2001年 | 679篇 |
2000年 | 510篇 |
1999年 | 382篇 |
1998年 | 254篇 |
1997年 | 175篇 |
1996年 | 197篇 |
1995年 | 151篇 |
1994年 | 145篇 |
1993年 | 138篇 |
1992年 | 115篇 |
1991年 | 115篇 |
1990年 | 91篇 |
1989年 | 75篇 |
1988年 | 52篇 |
1987年 | 46篇 |
1986年 | 39篇 |
1985年 | 45篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
701.
702.
Ke Xu Evan T. Vickers Longshi Rao Dr. Sarah A. Lindley A'Lester C. Allen Prof. Binbin Luo Prof. Xueming Li Prof. Jin Zhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):5014-5021
CH3NH3PbBr3 perovskite quantum dots (PQDs) are synthesized by using four different linear alkyl phosphonic acids (PAs) in conjunction with (3-aminopropyl)triethoxysilane (APTES) as capping ligands. The resultant PQDs are characterized by means of XRD, TEM, Raman spectroscopy, FTIR spectroscopy, UV/Vis, photoluminescence (PL), time-resolved PL, and X-ray photoelectron spectroscopy (XPS). PA chain length is shown to control the PQD size (ca. 2.9–4.2 nm) and excitonic absorption band positions (λ=488–525 nm), with shorter chain lengths corresponding to smaller sizes and bluer absorptions. All samples show a high PL quantum yield (ca. 46–83 %) and high PL stability; this is indicative of a low density of band gap trap states and effective surface passivation. Stability is higher for smaller PQDs; this is attributed to better passivation due to better solubility and less steric hindrance of the shorter PA ligands. Based on the FTIR, Raman, and XPS results, it is proposed that Pb2+ and CH3NH3+ surface defects are passivated by R−PO32− or R−PO2(OH)−, whereas Br− surface defects are passivated by R−NH3+ moieties. This study establishes the combination of PA and APTES ligands as a highly effective dual passivation system for the synergistic passivation of multiple surface defects of PQDs through primarily ionic bonding. 相似文献
703.
Dr. He Zhao Xiu Li Rongqing Guan Prof. Huanfeng Jiang Prof. Min Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15858-15862
The tandem dual C−H amination of tetrahydroquinoxalines with free amines under aerobic copper catalysis conditions has been demonstrated. The synthetic protocol proceeds with good substrate and functional group compatibility, mild reaction conditions, short reaction time, the use of the naturally abundant [Cu]/O2 catalyst system, excellent chemoselectivity and synthetic efficiency, and with no need for the pre-installation of specific aminating agents, which offers a practical platform for the rapid and diverse synthesis of diaminoquinoxalines. Moreover, this work has shown the potential of single-electron-oxidation-induced C−H functionalization of N-heterocycles, and its application in the development of optoelectronic materials. 相似文献
704.
Dr. Longyu Li Qianming Lin Miao Tang Dr. Andrew J. E. Duncan Prof. Dr. Chenfeng Ke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10768-10781
The rapid development of additive manufacturing techniques, also known as three-dimensional (3D) printing, is driving innovations in polymer chemistry, materials science, and engineering. Among current 3D printing techniques, direct ink writing (DIW) employs viscoelastic materials as inks, which are capable of constructing sophisticated 3D architectures at ambient conditions. In this perspective, polymer designs that meet the rheological requirements for direct ink writing are outlined and successful examples are summarized, which include the development of polymer micelles, co-assembled hydrogels, supramolecularly cross-linked systems, polymer liquids with microcrystalline domains, and hydrogels with dynamic covalent cross-links. Furthermore, advanced polymer designs that reinforce the mechanical properties of these 3D printing materials, as well as the integration of functional moieties to these materials are discussed to inspire new polymer designs for direct ink writing and broadly 3D printing. 相似文献
705.
Wang Fei Cressault Yann Teulet Philippe Li Huan Yang Ke 《Plasma Chemistry and Plasma Processing》2019,39(4):1049-1069
Plasma Chemistry and Plasma Processing - Gas tungsten arc welding (GTAW), a widely used industrial process, is one of the most intense artificial sources of optical radiation. This paper presents a... 相似文献
706.
Hui‐Min Lin Jian‐Rong Li Chao Mu Ao Li Xu‐Feng Liu Pei‐Hua Zhao Yu‐Long Li Zhong‐Qing Jiang Hong‐Ke Wu 《应用有机金属化学》2019,33(11)
Five monophosphine‐substituted diiron propane‐1,2‐dithiolate complexes as the active site models of [FeFe]‐hydrogenases have been synthesized and characterized. Reactions of complex [Fe2(CO)6{μ‐SCH2CH(CH3)S}] ( 1 ) with a monophosphine ligand tris(4‐methylphenyl)phosphine, diphenyl‐2‐pyridylphosphine, tris(4‐chlorophenyl)phosphine, triphenylphosphine, or tris(4‐fluorophenyl)phosphine in the presence of the oxidative agent Me3NO·2H2O gave the monophosphine‐substituted diiron complexes [Fe2(CO)5(L){μ‐SCH2CH(CH3)S}] [L = P(4‐C6H4CH3)3, 2 ; Ph2P(2‐C5H4N), 3 ; P(4‐C6H4Cl)3, 4 ; PPh3, 5 ; P(4‐C6H4F)3, 6 ] in 81%–94% yields. Complexes 2 – 6 have been characterized by elemental analysis, spectroscopy, and X‐ray crystallography. In addition, electrochemical studies revealed that these complexes can catalyze the reduction of protons to H2 in the presence of HOAc. 相似文献
707.
708.
709.
In this paper,we design a novel three-order autonomous system.Numerical simulations reveal the complex chaotic behaviors of the system.By applying the undetermined coefficient method,we find a heteroclinic orbit in the system.As a result,the Si’lnikov criterion along with some other given conditions guarantees that the system has both Smale horseshoes and chaos of horseshoe type. 相似文献
710.
The cheap and easily available sodium dithionite and thiourea dioxide have been used as the source of sulfonyl group in the synthesis of sulfones and sulfonamides recently.Compared with other methods for the sulfonylation reactions,the strategies using sodium dithionite or thiourea dioxide provide an alternative and complementary route to diverse sulfonyl compounds.During the reaction process,sulfur dioxide anion radical is the key intermediate,which is usually generated from a single electron transfer under suitable conditions.The advantages using sodium dithionite or thiourea dioxide in the sulfonylation reactions include mild conditions and broad substrate scope with excellent functional group compatibility.Further applications by using sodium dithionite and thiourea dioxide in organic transformations will be anticipated. 相似文献