全文获取类型
收费全文 | 4598篇 |
免费 | 130篇 |
国内免费 | 14篇 |
专业分类
化学 | 2391篇 |
晶体学 | 33篇 |
力学 | 551篇 |
数学 | 975篇 |
物理学 | 792篇 |
出版年
2022年 | 62篇 |
2021年 | 88篇 |
2020年 | 37篇 |
2019年 | 78篇 |
2018年 | 48篇 |
2017年 | 69篇 |
2016年 | 114篇 |
2015年 | 104篇 |
2014年 | 97篇 |
2013年 | 380篇 |
2012年 | 197篇 |
2011年 | 214篇 |
2010年 | 133篇 |
2009年 | 116篇 |
2008年 | 212篇 |
2007年 | 178篇 |
2006年 | 228篇 |
2005年 | 192篇 |
2004年 | 126篇 |
2003年 | 137篇 |
2002年 | 162篇 |
2001年 | 60篇 |
2000年 | 161篇 |
1999年 | 50篇 |
1998年 | 41篇 |
1997年 | 36篇 |
1996年 | 56篇 |
1995年 | 61篇 |
1994年 | 58篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 44篇 |
1990年 | 34篇 |
1989年 | 36篇 |
1987年 | 36篇 |
1985年 | 59篇 |
1984年 | 49篇 |
1983年 | 56篇 |
1982年 | 44篇 |
1981年 | 39篇 |
1980年 | 52篇 |
1979年 | 34篇 |
1977年 | 36篇 |
1975年 | 52篇 |
1974年 | 61篇 |
1973年 | 35篇 |
1971年 | 40篇 |
1970年 | 36篇 |
1969年 | 60篇 |
1968年 | 38篇 |
排序方式: 共有4742条查询结果,搜索用时 15 毫秒
191.
Rouven F. Pfleger Sören Schlittenhardt Dr. Marcel P. Merkel Prof. Dr. Mario Ruben Prof. Dr. Karin Fink Dr. Christopher E. Anson Prof. Jesper Bendix Prof. Dr. Annie K. Powell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15086-15095
We report three structurally related single ion Dy compounds using the pentadentate ligand 2,6-bis((E)-1-(2-(pyridin-2-yl)-hydrazineylidene)ethyl)pyridine (H2dapp) [Dy(H2dapp)(NO3)2]NO3 ( 1 ), [Dy(H2dapp)(OAc)2]Cl ( 2 ) and [Dy(H2dapp)(NO3)2]Cl0.92(NO3)0.08 ( 3 ). The (H2dapp) occupies a helical twisted pentagonal equatorial arrangement with two anionic ligands in the axial positions. Further influence on the electronic and magnetic structure is provided by a closely associated counterion interacting with the central N−H group of the (H2dapp). The slow relaxation of the magnetisation shows that the anionic acetates give the greatest slowing down of the magnetisation reversal. Further influence on the relaxation properties of compounds 1 and 2 is the presence of short nitrate-nitrate intermolecular ligand contact opening further lattice relaxation pathways. 相似文献
192.
Dr. Sankar Mohan Dr. Philip S. Kerry Nicole Bance Prof. Dr. Masahiro Niikura Prof. Dr. B. Mario Pinto 《Angewandte Chemie (International ed. in English)》2014,53(4):1076-1080
We have previously reported a potent neuraminidase inhibitor that comprises a carbocyclic analogue of zanamivir in which the hydrophilic glycerol side chain is replaced by the hydrophobic 3‐pentyloxy group of oseltamivir. This hybrid inhibitor showed excellent inhibitory properties in the neuraminidase inhibition assay (Ki=0.46 nM ; Ki (zanamivir)=0.16 nM ) and in the viral replication inhibition assay in cell culture at 10?8 M . As part of this lead optimization, we now report a novel spirolactam that shows comparable inhibitory activity in the cell culture assay to that of our lead compound at 10?7 M . The compound was discovered serendipitously during the attempted synthesis of the isothiourea derivative of the original candidate. The X‐ray crystal structure of the spirolactam in complex with the N8 subtype neuraminidase offers insight into the mode of inhibition. 相似文献
193.
Molecular Recognition of Nucleotides in Water by Scorpiand‐Type Receptors Based on Nucleobase Discrimination 下载免费PDF全文
Mario Inclán Dr. M. Teresa Albelda Dr. Esther Carbonell Dr. Salvador Blasco Antonio Bauzá Prof. Antonio Frontera Prof. Enrique García‐España 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3730-3741
The detection of nucleotides is of crucial importance because they are the basic building blocks of nucleic acids. Scorpiand‐based polyamine receptors functionalized with pyridine or anthracene units are able to form stable complexes with nucleotides in water, based on coulombic, π–π stacking, and hydrogen‐bonding interactions. This behavior has been rationalized by means of an exploration with NMR spectroscopy and DFT calculations. Binding constants were determined by potentiometry. Fluorescence spectroscopy studies have revealed the potential of these receptors as sensors to effectively and selectively distinguish guanosine‐5′‐triphosphate (GTP) from adenosine‐5′‐triphosphate (ATP). 相似文献
194.
Experimental and Theoretical Studies on Arene‐Bridged Metal–Metal‐Bonded Dimolybdenum Complexes 下载免费PDF全文
Dr. Mario Carrasco Natalia Curado Dr. Eleuterio Álvarez Dr. Celia Maya Dr. Riccardo Peloso Prof. Dr. Manuel L. Poveda Dr. Amor Rodríguez Prof. Dr. Eliseo Ruiz Prof. Dr. Santiago Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6092-6102
The bis(hydride) dimolybdenum complex, [Mo2(H)2{HC(N‐2,6‐iPr2C6H3)2}2(thf)2], 2 , which possesses a quadruply bonded Mo2II core, undergoes light‐induced (365 nm) reductive elimination of H2 and arene coordination in benzene and toluene solutions, with formation of the MoI2 complexes [Mo2{HC(N‐2,6‐iPr2C6H3)2}2(arene)], 3?C6H6 and 3?C6H5Me , respectively. The analogous C6H5OMe, p‐C6H4Me2, C6H5F, and p‐C6H4F2 derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo2 complex precursors. X‐ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the MoI2 core, coordinating to each in an η2 fashion. In solution, the arene rotates fast on the NMR timescale around the Mo2‐arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron‐rich C?C bonds. 相似文献
195.
Air‐Stable Solid Aryl and Heteroaryl Organozinc Pivalates: Syntheses and Applications in Organic Synthesis 下载免费PDF全文
Sophia M. Manolikakes Mario Ellwart Dr. Christos I. Stathakis Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12289-12297
A wide range of air‐stable, solid, polyfunctional aryl and heteroarylzinc pivalates were efficiently prepared by either magnesium insertion or Hal/Mg exchange followed by transmetalation with Zn(OPiv)2 (OPiv=pivalate). By reducing the amount of LiCl the air stability could be significantly enhanced compared with previously prepared reagents. An alternative route is directed magnesiation using TMPMgCl ? LiCl (TMP=2,2,6,6‐tetramethylpiperidyl) followed by transmetalation with Zn(OPiv)2 or, for very sensitive substrates, direct zincation by using TMPZnOPiv. These zinc reagents not only show excellent stability towards air, but they also undergo a broad range of C?C bond‐formation reactions, such as allylation and carbocupration reactions, as well as addition to aldehydes and 1,4‐addition reactions. Acylation reactions can be performed by using an excess of TMSCl to overcome side reactions of the omnipresent pivalate anion. 相似文献
196.
Andrea Marchesi Dr. Fabio Parmeggiani João Louçano Ashley P. Mattey Dr. Kun Huang Tanistha Gupta Dr. Mario Salwiczek Prof. Sabine L. Flitsch 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22642-22645
Automated chemical oligosaccharide synthesis is an attractive concept that has been successfully applied to a large number of target structures, but requires excess quantities of suitably protected and activated building blocks. Herein we demonstrate the use of biocatalysis to supply such reagents for automated synthesis. By using the promiscuous NmLgtB-B β1-4 galactosyltransferase from Neisseria meningitidis we demonstrate fast and robust access to the LacNAc motif, common to many cell-surface glycans, starting from either lactose or sucrose as glycosyl donors. The enzymatic product was shown to be successfully incorporated as a complete unit into a tetrasaccharide target by automated assembly. 相似文献
197.
Marvin Fresia Dr. Mario Kock Prof. Dr. Thomas Lindel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(56):12733-12737
The enantioselective synthesis of (−)-dihydroraputindole D is reported. The key step is the desymmetrizing benzoylation of a prochiral 1,3-diol employing Trost′s ProPhenol catalyst system, which has been applied for the first time to a cyclic molecule carrying geminal hydroxymethyl groups. The cyclopenta[f]indoline system was assembled by Au(I)-catalyzed cyclization of an alkynylated indoline precursor. (−)-Dihydroraputindole D was obtained in 17 steps and 8% overall yield starting from dihydroxyacetone. In combination with quantum chemical calculations of the ECD spectra, our synthesis allowed us to determine the absolute configuration (5S,7R) of the natural product (+)-raputindole D from the Rutaceous plant Raputia simulans. 相似文献
198.
199.
Dr. Alessandro Presentato Dr. Antonino Scurria Dr. Lorenzo Albanese Dr. Claudia Lino Dr. Marzia Sciortino Dr. Mario Pagliaro Dr. Federica Zabini Dr. Francesco Meneguzzo Prof. Rosa Alduina Dr. Domenico Nuzzo Dr. Rosaria Ciriminna 《ChemistryOpen》2020,9(5):628-630
Pectin extracted via hydrodynamic cavitation in water only from waste lemon peel and further isolated via freeze drying displays significant antibacterial activity against Staphylococcus aureus, a Gram positive pathogen which easily contaminates food. The antibacterial effect of the new IntegroPectin is largely superior to that of commercial citrus pectin, opening the way to advanced applications of a new bioproduct now obtainable in large amounts and at low cost from citrus juice industry's waste. 相似文献
200.
Maurizi Enrici Tommaso Mertens Anne Sinnaeve Mario Tchuindjang Jérôme Tchoufang 《Journal of Thermal Analysis and Calorimetry》2020,141(3):1075-1089
Journal of Thermal Analysis and Calorimetry - In this work, a complex graphitic high-speed steel (Gr-HSS) obtained from a spin-casting process that allows high cooling rates during solidification... 相似文献