全文获取类型
收费全文 | 900篇 |
免费 | 29篇 |
国内免费 | 4篇 |
专业分类
化学 | 538篇 |
晶体学 | 4篇 |
力学 | 10篇 |
数学 | 155篇 |
物理学 | 194篇 |
无线电 | 32篇 |
出版年
2023年 | 17篇 |
2022年 | 28篇 |
2021年 | 37篇 |
2020年 | 28篇 |
2019年 | 36篇 |
2018年 | 40篇 |
2017年 | 29篇 |
2016年 | 34篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 50篇 |
2012年 | 50篇 |
2011年 | 76篇 |
2010年 | 59篇 |
2009年 | 49篇 |
2008年 | 48篇 |
2007年 | 42篇 |
2006年 | 49篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 4篇 |
1965年 | 7篇 |
1962年 | 3篇 |
排序方式: 共有933条查询结果,搜索用时 15 毫秒
31.
32.
Svetlana F. Malysheva Natal’ya A. Belogorlova Nina K. Gusarova Alexander V. Artem’ev Alexander I. Albanov Boris A. Trofimov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1688-1693
Abstract Red phosphorus reacts with allylbenzene in the superbase system KOH-DMSO (130°C, 3 h, Ar) to give a mixture of bis(1-methyl-2-phenylethyl)phosphane (1), bis(1-methyl-2-phenylethyl)phosphane oxide (2), and 1-methyl-2-phenylethylphosphinic acid (3). Secondary phosphane oxide 2 and phosphinic acid 3 have been isolated from this mixture in 35% and 32% yield, respectively. Microwave activation of the reaction (200 W, 30 min) affords secondary phosphane 1 as the main product in 48% yield. GRAPHICAL ABSTRACT 相似文献
33.
34.
Artem V. Matyskin Danas Ridikas V. S. Skuridin Johannes Sterba Georg Steinhauser 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):413-418
The subject of this paper is to explore the possibility to obtain 99mTc from activation of 98Mo, using the TRIGA Mark II low flux research reactor (Vienna, Austria). Irradiation of both natural and enriched in 98Mo molybdenum oxides was compared. Aims of this work included the determination of neutron fluxes and 98Mo(n, γ)99Mo reaction effective cross section in the TRIGA Mark II reactor irradiation channels, calculation of 99Mo specific activities, determination of optimal irradiation conditions for the subsequent 99mTc separation from MoO3 targets using concentrating technologies. 相似文献
35.
Elena A. Shalamova Yeosan Lee Garam Chung Artem N. Semakin Jinho Oh Alexey Yu. Sukhorukov Dmitry E. Arkhipov Sema L. Ioffe Sergey E. Semenov 《Tetrahedron letters》2014
A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized. 相似文献
36.
A. A. Mishchenko N. P. Korotkova V. S. Lebedev Yu. T. Panov 《Polymer Science Series D》2014,7(4):271-274
This article describes synthesis of polyurethane (PU) elastomers based on DMC polyethers. The influence of the molecular weight of DMC polyethers on the strength characteristics and mechanical hysteresis of model PU composites based on them is studied. It is shown that, when the molecular weight of DMC polyethers changes in the range of 2000–4000, the strength of PU materials dramatically increases, while a considerable improvement of elastic properties is observed when using polyethers with MW = 8.000 or higher. 相似文献
37.
Cellulose - This study addresses the question of how the difference in mechanical properties of the individual layers in a multi-ply commercial paperboard affects the outcome of the tray-forming... 相似文献
38.
Svitlana O. Sotnik Artem M. Mishchenko Eduard B. Rusanov Andriy V. Kozytskiy Konstantin S. Gavrilenko Sergey V. Ryabukhin Dmitriy M. Volochnyuk Sergey V. Kolotilov 《Molecules (Basel, Switzerland)》2021,26(12)
The third generation Buchwald precatalysts Pd(ABP)(Phos)(OMs) (also known as Phos Pd G3)) with XPhos and RuPhos were prepared in multigram scale by a modified procedure (ABP = fragment of C-deprotonated 2-aminobiphenyl, XPhos = 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, RuPhos = 2-dicyclohexylphosphino-2′,6′-diisopropoxybiphenyl, OMs− = CH3SO3−). The 1H- and 31P-NMR spectra of the title complexes and some impurities, measured by various 1D and 2D techniques, were analyzed in detail. The solvent-dependent isomerization of Pd(ABP)(XPhos)(OMs) was studied by NMR, and the X-ray structures of two isomers were determined. The impurities in precatalysts, such as Pd(ABP)(HABP)(OMs) (HABP—neutral 2-aminobiphenyl coordinated to Pd2+ in N-monodentate mode) and PdCl2(XPhos)2, were identified and characterized by single crystal X-ray diffraction. A simple method for the quick quality control (QC) of the precatalysts, suitable for routine use, was proposed. The method was based on the assessment of the impurity content on the basis of the 1H-NMR spectra analysis. 相似文献
39.
Prof. Dr. Evgeny V. Tretyakov Dr. Svetlana I. Zhivetyeva Dr. Pavel V. Petunin Dmitry E. Gorbunov Prof. Dr. Nina P. Gritsan Prof. Dr. Irina Yu. Bagryanskaya Dr. Artem S. Bogomyakov Dr. Pavel S. Postnikov Dr. Maxim S. Kazantsev Prof. Dr. Marina E. Trusova Dr. Inna K. Shundrina Dr. Elena V. Zaytseva Dr. Dmitriy A. Parkhomenko Prof. Dr. Elena G. Bagryanskaya Prof. Dr. Victor I. Ovcharenko 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20885-20891
Thermally stable organic diradicals with a triplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications. A series of phenylene-bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium-catalyzed cross-coupling reaction of iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields. The diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. For the diradicals, both substantial AF (ΔEST≈−64 cm−1) and FM (ΔEST≥25 and 100 cm−1) intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para- or meta-phenylene) and by the type of oxoverdazyl block (C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique one-dimensional exchange-coupled chains with strong intra- and weak inter-diradical ferromagnetic coupling. 相似文献
40.
Dmitri O. Charkin Stanislav I. Bezzubov Oleg I. Siidra Artem S. Borisov Stepan N. Kalmykov 《无机化学与普通化学杂志》2020,646(11-12):540-543
Crystals of a new uranyl sulfate (C2N4H8S2)[UO2(SO4)2] · 0.3H2O ( 1 ) templated by a relatively rare bis-isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P212121, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO2(SO4)2] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C2N4H8S22+ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO22+ partially reduced to U4+. 相似文献