全文获取类型
收费全文 | 1373607篇 |
免费 | 33585篇 |
国内免费 | 11593篇 |
专业分类
化学 | 689317篇 |
晶体学 | 14626篇 |
力学 | 76335篇 |
综合类 | 401篇 |
数学 | 245979篇 |
物理学 | 392127篇 |
出版年
2021年 | 13472篇 |
2020年 | 16764篇 |
2019年 | 17073篇 |
2018年 | 15048篇 |
2017年 | 13603篇 |
2016年 | 29735篇 |
2015年 | 22042篇 |
2014年 | 31938篇 |
2013年 | 76402篇 |
2012年 | 42398篇 |
2011年 | 41355篇 |
2010年 | 40283篇 |
2009年 | 42251篇 |
2008年 | 39196篇 |
2007年 | 35536篇 |
2006年 | 39703篇 |
2005年 | 32463篇 |
2004年 | 32878篇 |
2003年 | 29552篇 |
2002年 | 27140篇 |
2001年 | 29830篇 |
2000年 | 24473篇 |
1999年 | 21209篇 |
1998年 | 19334篇 |
1997年 | 19881篇 |
1996年 | 19543篇 |
1995年 | 18876篇 |
1994年 | 18416篇 |
1993年 | 17855篇 |
1992年 | 18230篇 |
1991年 | 18394篇 |
1990年 | 17657篇 |
1989年 | 17624篇 |
1988年 | 17218篇 |
1987年 | 17187篇 |
1986年 | 16121篇 |
1985年 | 22627篇 |
1984年 | 23721篇 |
1983年 | 19756篇 |
1982年 | 21380篇 |
1981年 | 20595篇 |
1980年 | 19911篇 |
1979年 | 20412篇 |
1978年 | 21567篇 |
1977年 | 21284篇 |
1976年 | 21052篇 |
1975年 | 19742篇 |
1974年 | 19415篇 |
1973年 | 19912篇 |
1972年 | 14365篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Kim D. G. Bakhteeva E. I. Sharutin V. V. 《Russian Journal of General Chemistry》2020,90(11):2064-2067
Russian Journal of General Chemistry - Cyclization of 4-propargylsulfanylquinazoline under the action of iodine gave 3-iodomethyl[1,3]thiazolo[3,2-c]-quinazolinium triiodide, which is reduced with... 相似文献
992.
Dolganov A. V. Balandina A. V. Chugunov D. B. Timonina A. S. Lyukshina Yu. I. Ahmatova A. A. Yudina A. D. Shindina V. V. Zhirnova V. O. Klimaeva L. A. Osipov A. K. 《Russian Journal of General Chemistry》2020,90(7):1229-1234
Russian Journal of General Chemistry - The possibility of 10-methyl-9-phenylacridine iodide usage as a photocatalyst in the process of molecular hydrogen evolution in various aprotic solvents has... 相似文献
993.
Russian Journal of Applied Chemistry - Extraction of rare earth elements with solutions of di(2-ethylhexyl) hydrogen phosphate or tributyl phosphate in heptane, toluene, or tetrachloromethane is... 相似文献
994.
Abou-Dina M. S. Helal M. A. Ghaleb Ahmed F. Kaoullas George Georgiou Georgios C. 《Meccanica》2020,55(7):1499-1507
Meccanica - The occurrence of slip complicates the estimation of the viscosity in rheometric flows. Thus, special analyses and experimental protocols are needed in order to obtain reliable... 相似文献
995.
Nonlinear Dynamics - This paper describes the chaos behavior of an in-plane tethered satellite system induced by atmospheric drag and the Earth’s oblateness. A commonly used model, the... 相似文献
996.
Eva Dehling Jennifer Rüschenbaum Julia Diecker Wolfgang Drner Henning D. Mootz 《Chemical science》2020,11(33):8945
Nonribosomal peptide synthetases (NRPSs) are large, multi-modular enzyme templates for the biosynthesis of important peptide natural products. Modules are composed of a set of semi-autonomous domains that facilitate the individual reaction steps. Only little is known about the existence and relevance of a higher-order architecture in these mega-enzymes, for which contacts between non-neighboring domains in three-dimensional space would be characteristic. Similarly poorly understood is the structure of communication-mediating (COM) domains that facilitate NRPS subunit docking at the boundaries between epimerization and condensation domains. We investigated a COM domain pair in a minimal two module NRPS using genetically encoded photo-crosslinking moieties in the N-terminal acceptor COM domain. Crosslinks into the C-terminal donor COM domain of the partner module resulted in protein products with the expected migration behavior on SDS-PAGE gels corresponding to the added molecular weight of the proteins. Additionally, an unexpected apparent high-molecular weight crosslink product was revealed by mass spectrometric analysis to represent a T-form isomer with branched connectivity of the two polypeptide chains. Synthesis of the linear L-form and branched T-form isomers by click chemistry confirmed this designation. Our data revealed a surprising spatial proximity between the acceptor COM domain and the functionally unrelated small subdomain of the preceding adenylation domain. These findings provide an insight into three-dimensional domain arrangements in NRPSs in solution and suggest the described photo-crosslinking approach as a promising tool for the systematic investigation of their higher-order architecture.Photo-crosslink analysis reveals unexpected insights into the higher-order architecture of NRPS and the nature of crosslink isomers. 相似文献
997.
Yong-Jin Zhao Jian-Ping Ma Jianzhong Fan Yan Geng Yu-Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(6):605-615
The tridentate organic ligand 4,4′,4′′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6,10‐triyl)tribenzoic acid ( H3L ) has been synthesized (as the methanol 1.25‐solvate, C48H39NO6·1.25CH3OH). As a donor–acceptor motif molecule, H3L possess strong intramolecular charge transfer (ICT) fluorescence. Through hydrogen bonds, H3L molecules construct a two‐dimensional (2D) network, which pack together into three‐dimensional (3D) networks with an ABC stacking pattern in the crystalline state. Based on H3L and M(NO3)2 salts (M = Cd and Zn) under solvothermal conditions, two metal–organic frameworks (MOFs), namely, catena‐poly[[triaquacadmium(II)]‐μ‐10‐(4‐carboxyphenyl)‐4,4′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6‐diyl)dibenzoato], [Cd(C48H37NO6)(H2O)3]n, I , and poly[[μ3‐4,4′,4′′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6,10‐triyl)tribenzoato](μ3‐hydroxido)zinc(II)], [Zn2(C48H36NO6)(OH)]n, II , were synthesized. Single‐crystal analysis revealed that both MOFs adopt a 3D structure. In I , partly deprotonated HL 2? behaves as a bidentate ligand to link a CdII ion to form a one‐dimensional chain. In the solid state of I , the existence of weak interactions, such as O—H…O hydrogen bonds and π–π interactions, plays an essential role in aligning 2D nets and 3D networks with AB packing patterns for I . The deprotonated ligand L 3? in II is utilized as a tridentate building block to bind ZnII ions to construct 3D networks, where unusual Zn4O14 clusters act as connection nodes. As a donor–acceptor molecule, H3L exhibits fluorescence with a photoluminescence quantum yield (PLQY) of 70% in the solid state. In comparison, the PL of both MOFs is red‐shifted with even higher PLQYs of 79 and 85% for I and II , respectively. 相似文献
998.
Ein elektronenreiches cyclisches (Alkyl)(amino)carben auf Au(111)-, Ag(111)- und Cu(111)-Oberflächen
Anne Bakker Dr. Matthias Freitag Elena Kolodzeiski Peter Bellotti Dr. Alexander Timmer Dr. Jindong Ren Bertram Schulze Lammers Daniel Moock Prof. Dr. Herbert W. Roesky Dr. Harry Mönig Dr. Saeed Amirjalayer Prof. Dr. Harald Fuchs Prof. Dr. Frank Glorius 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13745-13749
999.
Dr. Peng Wang Dr. Chang-xin Huo Shuyao Lang Dr. Kyle Caution Dr. Setare Tahmasebi Nick Prof. Purnima Dubey Prof. Rajendar Deora Prof. Xuefei Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6513-6520
With the infection rate of Bordetella pertussis at a 60-year high, there is an urgent need for new anti-pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis-LPS-like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti-glycan IgG responses with IgG titers reaching several million enzyme-linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ-glycan as a new anti-pertussis vaccine. 相似文献
1000.
Hong Song Ya Li Qi-Jun Yao Liang Jin Lei Liu Yan-Hua Liu Prof. Dr. Bing-Feng Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6638-6642
The atroposelective synthesis of axially chiral styrenes remains a formidable challenge due to their relatively lower rotational barriers compared to the biaryl atropoisomers. Herein, we describe the construction of axially chiral styrenes through PdII-catalyzed atroposelective C−H olefination, using a bulky amino amide as a transient chiral auxiliary. Various axially chiral styrenes were produced with good yields and high enantioselectivity (up to 95 % yield and 99 % ee). Carboxylic acid derivatives of the resulting axially chiral styrenes showed superior enantiocontrol over the biaryl counterparts in CoIII-catalyzed enantioselective C(sp3)−H amidation of thioamide. Mechanistic studies suggest that C−H cleavage is the enantioselectivity-determining step. 相似文献