全文获取类型
收费全文 | 25260篇 |
免费 | 1189篇 |
国内免费 | 1445篇 |
专业分类
化学 | 18732篇 |
晶体学 | 297篇 |
力学 | 492篇 |
综合类 | 10篇 |
数学 | 3727篇 |
物理学 | 4636篇 |
出版年
2023年 | 161篇 |
2022年 | 485篇 |
2021年 | 566篇 |
2020年 | 428篇 |
2019年 | 505篇 |
2018年 | 452篇 |
2017年 | 489篇 |
2016年 | 1017篇 |
2015年 | 811篇 |
2014年 | 942篇 |
2013年 | 1983篇 |
2012年 | 1827篇 |
2011年 | 1964篇 |
2010年 | 1182篇 |
2009年 | 1357篇 |
2008年 | 1519篇 |
2007年 | 1452篇 |
2006年 | 1226篇 |
2005年 | 1208篇 |
2004年 | 1442篇 |
2003年 | 1008篇 |
2002年 | 927篇 |
2001年 | 479篇 |
2000年 | 408篇 |
1999年 | 302篇 |
1998年 | 287篇 |
1997年 | 239篇 |
1996年 | 259篇 |
1995年 | 212篇 |
1994年 | 167篇 |
1993年 | 172篇 |
1992年 | 159篇 |
1991年 | 136篇 |
1990年 | 128篇 |
1989年 | 122篇 |
1988年 | 118篇 |
1987年 | 109篇 |
1986年 | 117篇 |
1985年 | 185篇 |
1984年 | 181篇 |
1983年 | 124篇 |
1982年 | 116篇 |
1981年 | 121篇 |
1980年 | 110篇 |
1979年 | 84篇 |
1978年 | 63篇 |
1977年 | 65篇 |
1976年 | 68篇 |
1975年 | 60篇 |
1974年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Reversible Activation of Water by an Air- and Moisture-Stable Frustrated Rhodium Nitrogen Lewis Pair
Dr. María Carmona Dr. Joaquina Ferrer Dr. Ricardo Rodríguez Dr. Vincenzo Passarelli Prof. Dr. Fernando J. Lahoz Dr. Pilar García-Orduña Dr. Laura Cañadillas-Delgado Prof. Dr. Daniel Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13665-13670
[Cp*Rh(κ3N,N′,P- L )][SbF6] (Cp*=C5Me5), bearing a guanidine-derived phosphano ligand L , behaves as a “dormant” frustrated Lewis pair and activates H2 and H2O in a reversible manner. When D2O is employed, a facile H/D exchange at the Cp* ring takes place through sequential C(sp3)−H bond activation. 相似文献
942.
943.
Anwar Jacintomoreno Dr. Hemant K. Sharma Dr. Alejandro Metta-Magaña Prof. Dr. Keith H. Pannell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(48):11302-11307
The reactions of the Mannich reagent Et3SiOCH2NMe2 ( 1 ) with a variety of anilines (mono-substituted RC6H4NH2, R=H, 4-CN, 4-NO2, 4-Ph, 4-Me, 4-MeO, 4-Me2N; di-substituted R2C6H3NH2, R2=3,5-(CH3)2, 3,5-(CF3)2; tri-substituted R3C6H2NH2, R3=3,5-Me2-4-Br and a “super bulky” aniline (Ar*NH2) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC6H4NH(CH2NMe2) [R=CN ( 2 a ), NO2 ( 2 b )] and R2C6H3NH(CH2NMe2) [R2=3,5-(CF3)2 ( 2 c) ] were formed. Further reaction of 2 a , b , c with 1 yielded the corresponding triamines RC6H4N(CH2NMe2)2 (R=CN ( 3 a ), NO2 ( 3 b ) and R2C6H3N(CH2NMe2)2, R2=3,5-(CF3)2 ( 3 c ). The new polyamines were characterized by NMR spectroscopy, and for 2 a , 2 c , and 3 c , by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe2, 4-Me, 3,5-Me2, 3,5-Me2-4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO ( 5 a ), 4-Me2N ( 5 b ), 4-Me ( 5 c ), 3,5-Me2 ( 5 d ), 3,5-Me2-4-Br ( 5 e ), 4-Ph ( 5 f ), 4-Cl ( 5 g ). The “super bulky” aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH2 ( 4 ) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of “Silick” chemistry. 相似文献
944.
Dr. Andy Hernández Montoto Dr. Antoni Llopis-Lorente Mónica Gorbe José M. Terrés Dr. Roberto Cao-Milán Dr. Borja Díaz de Greñu Dr. María Alfonso Dr. Javier Ibañez Prof. María D. Marcos Dr. Mar Orzáez Dr. Reynaldo Villalonga Prof. Ramón Martínez-Máñez Dr. Félix Sancenón 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8471-8478
Janus gold nanostar–mesoporous silica nanoparticle ( AuNSt–MSNP ) nanodevices able to release an entrapped payload upon irradiation with near infrared (NIR) light were prepared and characterized. The AuNSt surface was functionalized with a thiolated photolabile molecule ( 5 ), whereas the mesoporous silica face was loaded with a model drug (doxorubicin) and capped with proton-responsive benzimidazole-β-cyclodextrin supramolecular gatekeepers ( N 1 ). Upon irradiation with NIR-light, the photolabile compound 5 photodissociated, resulting in the formation of succinic acid, which induced the opening of the gatekeeper and cargo delivery. In the overall mechanism, the gold surface acts as a photochemical transducer capable of transforming the NIR-light input into a chemical messenger (succinic acid) that opens the supramolecular nanovalve. The prepared hybrid nanoparticles were non-cytotoxic to HeLa cells, until they were irradiated with a NIR laser, which led to intracellular doxorubicin release and hyperthermia. This induced a remarkable reduction in HeLa cells viability. 相似文献
945.
946.
947.
948.
Friis Helmer André Pedersen Janne Jettestuen Espen Helland Johan Olav Prodanović Maša 《Transport in Porous Media》2019,128(1):123-151
Transport in Porous Media - Multiphase flow simulations on imaged porous rock structures require numerical methods that are accurate and robust when applied on complex geometries. A key element in... 相似文献
949.
950.
The generation of nucleophiles from the combination of aryl boronic acids and catalytic amounts of copper salt allows a reactivity distinct from other organometallic species, such as organolithiums or Grignard reagents. Here we examine how the electronic and steric properties of the boronic acid affect the formation of active nucleophiles and their subsequent reactivity with iminium‐type compounds, showing that electron‐rich substrates display reduced reactivity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献