全文获取类型
收费全文 | 2011篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
化学 | 1341篇 |
晶体学 | 40篇 |
力学 | 22篇 |
数学 | 126篇 |
物理学 | 539篇 |
出版年
2023年 | 13篇 |
2022年 | 18篇 |
2021年 | 17篇 |
2020年 | 21篇 |
2019年 | 18篇 |
2016年 | 34篇 |
2015年 | 54篇 |
2014年 | 43篇 |
2013年 | 87篇 |
2012年 | 83篇 |
2011年 | 91篇 |
2010年 | 60篇 |
2009年 | 44篇 |
2008年 | 84篇 |
2007年 | 82篇 |
2006年 | 55篇 |
2005年 | 71篇 |
2004年 | 58篇 |
2003年 | 53篇 |
2002年 | 43篇 |
2001年 | 41篇 |
2000年 | 55篇 |
1999年 | 30篇 |
1998年 | 43篇 |
1997年 | 29篇 |
1996年 | 39篇 |
1995年 | 30篇 |
1994年 | 37篇 |
1993年 | 40篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 30篇 |
1984年 | 38篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 20篇 |
1980年 | 32篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 36篇 |
1976年 | 17篇 |
1975年 | 11篇 |
1974年 | 28篇 |
1973年 | 12篇 |
1968年 | 13篇 |
排序方式: 共有2068条查询结果,搜索用时 78 毫秒
111.
Magnetic Titanium Dioxide Nanocomposites for Surface‐Enhanced Resonance Raman Spectroscopic Determination and Degradation of Toxic Anilines and Phenols 下载免费PDF全文
Dr. Xiao Xia Han Dr. Lei Chen Dr. Uwe Kuhlmann Claudia Schulz Prof. Inez M. Weidinger Prof. Peter Hildebrandt 《Angewandte Chemie (International ed. in English)》2014,53(9):2481-2484
Mesoporous M‐TiO2 NCs, functionalized by PATP, can capture toxic anilines and phenols by azo coupling. Loading these nanodevices with Ag NPs offers the possibility for a sensitive quantitative determination of target compounds by SERRS spectroscopy, which allows multiplex detection because of the specific vibrational fingerprints. Sensitivity and selectivity can be further enhanced by concentrating the hybrid particles by an external magnet and compound‐specific binding (anilines versus phenols). The bound toxic compounds can be degraded by TiO2‐assisted photocatalysis after removal of the loaded hybrid particles from the sample solution with an external magnet. The degradation process can be enhanced in the presence of plasmonic Ag nanostructures. 相似文献
112.
Synthesis,Structure, and Reactivity of Diazene Adducts: Isolation of iso‐Diazene Stabilized as a Borane Adduct 下载免费PDF全文
Dipl.‐Chem. Fabian Reiß Prof. Dr. Axel Schulz Dr. Alexander Villinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11800-11811
This work describes the synthesis and full characterization of a series of GaCl3 and B(C6F5)3 adducts of diazenes R1?N?N?R2 (R1=R2=Me3Si, Ph; R1=Me3Si, R2=Ph). Trans‐Ph?N?N?Ph forms a stable adduct with GaCl3, whereas no adduct, but instead a frustrated Lewis acid–base pair is formed with B(C6F5)3. The cis‐Ph?N?N?Ph ? B(C6F5)3 adduct could only be isolated when UV light was used, which triggers the isomerization from trans‐ to cis‐Ph?N?N?Ph, which provides more space for the bulky borane. Treatment of trans‐Ph?N?N?SiMe3 with GaCl3 led to the expected trans‐Ph?N?N?SiMe3 ? GaCl3 adduct but the reaction with B(C6F5)3 triggered a 1,2‐Me3Si shift, which resulted in the formation of a highly labile iso‐diazene, Me3Si(Ph)N?N; stabilized as a B(C6F5)3 adduct. Trans‐Me3Si?N?N?SiMe3 forms a labile cis‐Me3Si?N?N?SiMe3 ? B(C6F5)3 adduct, which isomerizes to give the transient iso‐diazene species (Me3Si)2N?N ? B(C6F5)3 upon heating. Both iso‐diazene species insert easily into one B?C bond of B(C6F5)3 to afford hydrazinoboranes. All new compounds were fully characterized by means of X‐ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis. 相似文献
113.
A Volatile Lactone of Hymenoscyphus pseudoalbidus,Pathogen of European Ash Dieback,Inhibits Host Germination 下载免费PDF全文
Dr. Christian A. Citron Dr. Corina Junker Priv.‐Doz. Dr. Barbara Schulz Priv.‐Doz. Dr. Jeroen S. Dickschat 《Angewandte Chemie (International ed. in English)》2014,53(17):4346-4349
The largely unknown secondary metabolism of the plant pathogenic fungus Hymenoscyphus pseudoalbidus was investigated by use of the CLSA method. A set of volatile lactones was identified by GC/MS. The lactones were synthesized and used in bioassays in which one of the compounds was found to be a strong germination inhibitor for ash seeds, causing necroses in the plant tissue. 相似文献
114.
M. Sc. Christoph Helling Dr. George E. Cutsail III M. Sc. Hanns Weinert Dr. Christoph Wölper Prof. Dr. Stephan Schulz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(19):7631-7638
We report on the structures of three unprecedented heteroleptic Sb-centered radicals [L(Cl)Ga](R)Sb. ( 2-R , R=B[N(Dip)CH]2 2-B , 2,6-Mes2C6H3 2-C , N(SiMe3)Dip 2-N ) stabilized by one electropositive metal fragment [L(Cl)Ga] (L=HC[C(Me)N(Dip)]2, Dip=2,6-i-Pr2C6H3) and one bulky B- ( 2-B ), C- ( 2-C ), or N-based ( 2-N ) substituent. Compounds 2-R are predominantly metal-centered radicals. Their electronic properties are largely influenced by the electronic nature of the ligands R, and significant delocalization of unpaired-spin density onto the ligands was observed in 2-B and 2-N . Cyclic voltammetry (CV) studies showed that 2-B undergoes a quasi-reversible one-electron reduction, which was confirmed by the synthesis of [K([2.2.2]crypt)][L(Cl)GaSbB[N(Dip)CH]2] ([K([2.2.2]crypt)][ 2-B ]) containing the stibanyl anion [ 2-B ]−, which was shown to possess significant Sb−B multiple-bonding character. 相似文献
115.
Andrea Preuß Marcus Korb Tobias Rüffer Jörn Bankwitz Colin Georgi Alexander Jakob Stefan E. Schulz Heinrich Lang 《无机化学与普通化学杂志》2020,646(13):670-680
The template synthesis of ethylenediamine ( 1 ) with 2-acetylcyclopentanone ( 2 ) and [Cu(OAc)2 · H2O] ( 5 ) produced [Cu(1-(2-cC5H6(O))C(Me)NCH2)2)] ( 6 ) in 82 % yield. Reaction of 5 with bis(benzoylacetone)diethylenetriamine ( 7 , = L H)[1] gave [Cu(μ-OAc)( L )(H2O)]2 ( 8 ). The solid-state structures of 6 and 8 were determined confirming that 8 possesses intra- and intermolecular hydrogen bonds resulting in a dimer formation. The thermal behavior of 6 – 8 was studied by TG and TG-MS. Under oxygen CuO was formed, whereas under Ar Cu/Cu2O ( 6 ) or Cu ( 8 ) was obtained. Complex 6 was used as CVD precursor for Cu and Cu-oxide deposition (substrate temp., 400–500 °C, N2, 60 mL · min–1; O2, 60 mL · min–1; pressure, 0.87–1.5 mbar). The as-obtained deposits show separated particles of different appearance at the substrate surface as evidenced by SEM. Non-volatile 8 was applied as spin-coating precursor for Cu and CuO formation [conc. 0.25 mol · L–1; volume 0.2 mL; 3000 rpm; depos. time 2 min; heating rate 50 K · min–1; holding time 60 min (Ar), 120 min (air) at 800 °C]. The samples on silicon consist of granulated particles (Ar) or are non-dense with a grainy topography (air). EDX and XPS measurements confirmed the formation of Cu (Ar) or CuO (O2) with up to 13 mol-% C impurity. 相似文献
116.
A group additivity methodology for predicting the thermochemistry of oxygen-containing organosilanes
A combinatorial approach was applied to devise a set of reference Si–C–O–H species that is used to derive group-additivity values (GAVs) for this class of molecules. The reference species include 62 stable single-bonded, 19 cyclic, and nine double-bonded Si–C–O–H species. The thermochemistry of these reference species, that is, the standard enthalpy of formation, entropy, and heat capacities covering the temperature range from 298 to 2000 K was obtained from quantum chemical calculations using several composite methods, including G4, G4MP2, and CBSQB3, and the isodesmic reaction approach. To calculate the GAVs from the ab initio based thermochemistry of the compounds in the training set, a multivariable linear regression analysis is performed. The sensitivity of GAVs to the different composite methods is discussed, and thermodynamics properties calculated via group additivity are compared with available ab initio calculated values from the literature. 相似文献
117.
Teresa Ksel Gran Schulz Gerald Drger Andreas Kirschning 《Angewandte Chemie (International ed. in English)》2020,59(30):12376-12380
This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer‐bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2‐functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols. 相似文献
118.
119.
120.
It is shown that a Gaussian distribution of the distortion not enables in each case an exact evaluation of experimentally measured Debye-Scherrer lines. – After a discussion of simple possibilities for set up of simple and more common distortion distributions with more than one free parameter is given a procedure independent on the distortion distributions for the determination of roentgenographic particle sizes and distortions. 相似文献