全文获取类型
收费全文 | 2434篇 |
免费 | 48篇 |
国内免费 | 5篇 |
专业分类
化学 | 1577篇 |
晶体学 | 5篇 |
力学 | 27篇 |
数学 | 512篇 |
物理学 | 366篇 |
出版年
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 19篇 |
2016年 | 38篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 69篇 |
2012年 | 72篇 |
2011年 | 90篇 |
2010年 | 54篇 |
2009年 | 54篇 |
2008年 | 73篇 |
2007年 | 76篇 |
2006年 | 73篇 |
2005年 | 58篇 |
2004年 | 68篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1997年 | 31篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 31篇 |
1991年 | 23篇 |
1990年 | 36篇 |
1989年 | 27篇 |
1988年 | 28篇 |
1987年 | 33篇 |
1986年 | 20篇 |
1985年 | 54篇 |
1984年 | 45篇 |
1983年 | 44篇 |
1982年 | 22篇 |
1981年 | 45篇 |
1980年 | 43篇 |
1979年 | 28篇 |
1978年 | 41篇 |
1977年 | 37篇 |
1976年 | 26篇 |
1975年 | 36篇 |
1974年 | 32篇 |
1973年 | 23篇 |
1972年 | 17篇 |
1968年 | 14篇 |
1960年 | 19篇 |
1885年 | 15篇 |
排序方式: 共有2487条查询结果,搜索用时 46 毫秒
1.
2.
Dr. Shaima Hkiri Maxime Steinmetz Prof. Rachel Schurhammer Dr. David Sémeril 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202201887
The neutral complex dichloro-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)-(4-trifluoro-methylphenyl)methyl]phosphonate} (p-cymene)-ruthenium(II) was encapsulated inside a self-assembled hexameric host obtained upon reaction of 2,8,14,20-tetra-undecyl-resorcin[4]arene and water. The formation of an inclusion complex was inferred from a combination of spectral measurements (MS, UV/Vis spectroscopy, 1H and DOSY NMR). The 31P and 19F NMR spectra are consistent with motions of the ruthenium complex inside the self-assembled capsule. Molecular dynamics simulations carried out on the inclusion complex confirmed these intra-cavity movements and highlighted possible supramolecular interactions between the ruthenium first coordination sphere ligands and the inner part (aromatic rings) of the capsule. The embedded ruthenium complex was assessed in the catalytic oxidation (using NaIO4 as oxidant) of mixtures of three arylmethyl alcohols into the corresponding aldehydes. The reaction kinetics were shown to vary as a function of the substrates’ size, with the oxidation rate varying in the order benzylalcohol >4-phenyl-benzylalcohol >9-anthracenemethanol. Control experiments realized in the absence of hexameric capsule did not allow any discrimination between the substrates. 相似文献
3.
Mathematische Semesterberichte - 相似文献
4.
Clemens K. Blasius Niklas F. Heinrich Dr. Vladislav Vasilenko Prof. Lutz H. Gade 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16108-16111
A readily activated iron alkyl precatalyst effectively catalyzes the highly enantioselective hydroboration of N-alkyl imines. Employing a chiral bis(oxazolinylmethylidene)isoindoline pincer ligand, the asymmetric reduction of various acyclic N-alkyl imines provided the corresponding α-chiral amines in excellent yields and with up to >99 % ee. The applicability of this base metal catalytic system was further demonstrated with the synthesis of the pharmaceuticals Fendiline and Tecalcet. 相似文献
5.
Prof. Dr. Frank Heinrich Aria Salyapongse Akari Kumagai Dr. Fernando G. Dupuy Karpur Shukla Dr. Anja Penk Prof. Dr. Daniel Huster Prof. Dr. Robert K. Ernst Dr. Anna Pavlova Prof. Dr. James C. Gumbart Prof. Dr. Berthony Deslouches Prof. Dr. Y. Peter Di Prof. Dr. Stephanie Tristram-Nagle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6247-6256
In the quest for new antibiotics, two novel engineered cationic antimicrobial peptides (eCAPs) have been rationally designed. WLBU2 and D8 (all 8 valines are the d -enantiomer) efficiently kill both Gram-negative and -positive bacteria, but WLBU2 is toxic and D8 nontoxic to eukaryotic cells. We explore protein secondary structure, location of peptides in six lipid model membranes, changes in membrane structure and pore evidence. We suggest that protein secondary structure is not a critical determinant of bactericidal activity, but that membrane thinning and dual location of WLBU2 and D8 in the membrane headgroup and hydrocarbon region may be important. While neither peptide thins the Gram-negative lipopolysaccharide outer membrane model, both locate deep into its hydrocarbon region where they are primed for self-promoted uptake into the periplasm. The partially α-helical secondary structure of WLBU2 in a red blood cell (RBC) membrane model containing 50 % cholesterol, could play a role in destabilizing this RBC membrane model causing pore formation that is not observed with the D8 random coil, which correlates with RBC hemolysis caused by WLBU2 but not by D8. 相似文献
6.
Highly Segregated Lamello‐Columnar Mesophase Organizations and Fast Charge Carrier Mobility in New Discotic Donor–Acceptor Triads 下载免费PDF全文
Prof. Dr. Ke‐Qing Zhao Ling‐Ling An Xiao‐Bo Zhang Wen‐Hao Yu Prof. Ping Hu Prof. Bi‐Qin Wang Jing Xu Dr. Qing‐Dao Zeng Dr. Hirosato Monobe Dr. Yo Shimizu Dr. Benoît Heinrich Dr. Bertrand Donnio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10379-10390
Four new donor–acceptor triads (D–A–D) based on discotic and arylene mesogens have been synthesized by using Sonogashira coupling and cyclization reactions. This family of triads consists of two side‐on pending triphenylene mesogens, acting as the electron‐donating groups (D), laterally connected through short lipophilic spacers to a central perylenediimide (PI), benzo[ghi]perylenediimide (BI), or coronenediimide (CI) molecular unit, respectively, playing the role of the electron acceptor (A). All D–A–D triads self‐organize to form a lamello‐columnar oblique mesophase, with a highly segregated donor–acceptor (D–A) heterojunction organization, consequent to efficient molecular self‐sorting. The structure consists in the regular alternation of two disrupted rows of triphenylene columns and a continuous row of diimine species. High‐resolution STM images demonstrate that PI‐TP2 forms stable 2D self‐assembly nanostructures with some various degrees of regularity, whereas the other triads do not self‐organize into ordered architectures. The electron‐transport mobility of CI‐TP2, measured by time‐of‐flight at 200 °C in the mesophase, is one order of magnitude higher than the hole mobility. By means of this specific molecular designing idea, we realized and demonstrated for the first time the so‐called p–n heterojunction at the molecular level in which the electron‐rich triphenylene columns act as the hole transient pathways, and the coronenediimide stacks form the electron‐transport channels. 相似文献
7.
Influence of P‐Bonded Bulky Substituents on Electronic Interactions in Ferrocenyl‐Substituted Phospholes 下载免费PDF全文
Dominique Miesel Dr. Alexander Hildebrandt Marcus Korb Prof. Dr. Heinrich Lang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11545-11559
2,5‐Diferrocenyl‐1‐Ar‐1H‐phospholes 3 a – e (Ar=phenyl ( a ), ferrocenyl ( b ), mesityl ( c ), 2,4,6‐triphenylphenyl ( d ), and 2,4,6‐tri‐tert‐butylphenyl ( e )) have been prepared by reactions of ArPH2 ( 1 a – e ) with 1,4‐diferrocenyl butadiyne. Compounds 3 b – e have been structurally characterized by single‐crystal XRD analysis. Application of the sterically demanding 2,4,6‐tri‐tert‐butylphenyl group led to an increased flattening of the pyramidal phosphorus environment. The ferrocenyl units could be oxidized separately, with redox separations of 265 ( 3 b ), 295 ( 3 c ), 340 ( 3 d ), and 315 mV ( 3 e ) in [NnBu4][B(C6F5)4]; these values indicate substantial thermodynamic stability of the mixed‐valence radical cations. Monocationic [ 3 b ]+–[ 3 e ]+ show intervalence charge‐transfer absorptions between 4650 and 5050 cm?1 of moderate intensity and half‐height bandwidth. Compounds 3 c – e with bulky, electron‐rich substituents reveal a significant increase in electronic interactions compared with less demanding groups in 3 a and 3 b . 相似文献
8.
Dipl.‐Chem. Jan Tillmann Dipl.‐Chem. Josef Heinrich Wender Dr. Ute Bahr Dr. Michael Bolte Dr. Hans‐Wolfram Lerner Prof. Dr. Max C. Holthausen Prof. Dr. Matthias Wagner 《Angewandte Chemie (International ed. in English)》2015,54(18):5429-5433
Silicon analogues of the most prominent carbon nanostructures, namely, hollow spheroidals such as C60 and the fullerene family, have been unknown to date. Herein we show that discrete Si20 dodecahedra, stabilized by an endohedral guest and valence saturation, are accessible in preparative yields through a chloride‐induced disproportionation reaction of hexachlorodisilane in the presence of tri(n‐butyl)amine. X‐ray crystallography revealed that each silicon dodecahedron contains an endohedral chloride ion that imparts a net negative charge. Eight chloro substituents and twelve trichlorosilyl groups are attached to the surface of each cluster in a strictly regioregular arrangement, a thermodynamically preferred substitution pattern according to quantum‐chemical assessment. Our results demonstrate that the wet‐chemical self‐assembly of a complex, monodisperse Si nanostructure is possible under mild conditions starting from simple Si2 building blocks. 相似文献
9.
Dr. Luke A. Clifton Dr. Stephen A. Holt Dr. Arwel V. Hughes Dr. Emma L. Daulton Dr. Wanatchaporn Arunmanee Dr. Frank Heinrich Dr. Syma Khalid Damien Jefferies Dr. Timothy R. Charlton Dr. John R. P. Webster Dr. Christian J. Kinane Prof. Jeremy H. Lakey 《Angewandte Chemie (International ed. in English)》2015,54(41):11952-11955
Gram‐negative bacteria are an increasingly serious source of antibiotic‐resistant infections, partly owing to their characteristic protective envelope. This complex, 20 nm thick barrier includes a highly impermeable, asymmetric bilayer outer membrane (OM), which plays a pivotal role in resisting antibacterial chemotherapy. Nevertheless, the OM molecular structure and its dynamics are poorly understood because the structure is difficult to recreate or study in vitro. The successful formation and characterization of a fully asymmetric model envelope using Langmuir–Blodgett and Langmuir–Schaefer methods is now reported. Neutron reflectivity and isotopic labeling confirmed the expected structure and asymmetry and showed that experiments with antibacterial proteins reproduced published in vivo behavior. By closely recreating natural OM behavior, this model provides a much needed robust system for antibiotic development. 相似文献