全文获取类型
收费全文 | 901篇 |
免费 | 56篇 |
专业分类
化学 | 659篇 |
晶体学 | 7篇 |
力学 | 22篇 |
数学 | 30篇 |
物理学 | 239篇 |
出版年
2024年 | 3篇 |
2023年 | 22篇 |
2022年 | 13篇 |
2021年 | 25篇 |
2020年 | 40篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 28篇 |
2016年 | 48篇 |
2015年 | 23篇 |
2014年 | 37篇 |
2013年 | 62篇 |
2012年 | 70篇 |
2011年 | 92篇 |
2010年 | 47篇 |
2009年 | 33篇 |
2008年 | 57篇 |
2007年 | 44篇 |
2006年 | 46篇 |
2005年 | 31篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有957条查询结果,搜索用时 921 毫秒
41.
J. D. Sudha Subrata Pradhan Heera Viswanath Jisha Unnikrishnan Priyanka Brahmbhatt M. S. Manju 《Journal of Thermal Analysis and Calorimetry》2014,115(1):743-750
Thermosetting blend system of co-cured cyanate ester with epoxy resin is receiving importance for high technological applications because of its wide range of thermo-mechanical, rheological, and electrical properties. However, processing of these system warrant proper knowledge of the rheological behavior of the blend during the curing process. This article discusses the rheological behavior of the blend systems with respect to the pot life, gel time, gelation temperature and also evaluated fitting parameters for the prediction of gelation time and viscosity during the entire curing process from the isothermal rheological measurements. 相似文献
42.
Cover Picture: Double CaromH Activation Associated with Etheral Oxygen Insertion to Phenazine Architecture in Oxidisable Ruthenium(III) Complexes: A Mechanistic Insight (Chem. Eur. J. 10/2014) 下载免费PDF全文
43.
N‐Heterocyclic Carbene,High Oxidation State Molybdenum Alkylidene Complexes: Functional‐Group‐Tolerant Cationic Metathesis Catalysts 下载免费PDF全文
Prof. Michael R. Buchmeiser M. Sc. Suman Sen Dr. Jörg Unold Dr. Wolfgang Frey 《Angewandte Chemie (International ed. in English)》2014,53(35):9384-9388
We synthesized the first N‐heterocyclic carbene (NHC) complexes of Schrock’s molybdenum imido alkylidene bis(triflate) complexes. Unlike existing bis(triflate) complexes, the novel 16‐electron complexes represent metathesis active, functional‐group‐tolerant catalysts. Single‐crystal X‐ray structures of two representatives of this novel class of Schrock catalysts are presented and reactivity is discussed in view of their structural peculiarities. In the presence of monomer (substrate), these catalysts form cationic species and can be employed in ring‐closing metathesis (RCM), ring‐opening metathesis polymerization (ROMP), as well as in the cyclopolymerization of α,ω‐diynes. Monomers containing functional groups, which are not tolerated by the existing variations of Schrock’s catalyst, e.g., sec‐amine, hydroxy, and carboxylic acid moieties, can be used. These catalysts therefore hold great promise in both organic and polymer chemistry, where they allow for the use of protic monomers. 相似文献
44.
Abhijit Dutta Amit Kumar Pradhan Fei Qi Paritosh Mondal 《Monatshefte für Chemie / Chemical Monthly》2020,151(2):159-171
Quantum chemical study has been performed on finite-sized bi-metallic Rh3M alloys, M = Ag, Ir, Pd, Pt, Au, derived from magic cluster, Rh4. Bond length of C–O and N–O are noticed to be elongated in the presence of rhodium alloy clusters. CO2 and NO2 gases are found to be highly adsorbed on Rh3M clusters, which is confirmed by stretching frequency of C–O and N–O. DFT evaluated dipole moment and electronic charge redistribution suggests the sensing capability of CO2 and NO2 gases by Rh3M clusters which is further confirmed by the calculated HOMO–LUMO gap. Mixed rhodium alloy clusters supported on single-wall carbon nanotube (SWCNT) exhibits much higher ability to sense CO2 and NO2. On the other hand, SWCNT@Rh3M shows higher catalytic activity for the activation of CO2 and NO2 in comparison to bare Rh3M because of the higher electronic charge redistribution in the case of SWCNT@Rh3M. In case of SWCNT-supported gas adsorbed clusters, p electrons play a major role in bonding. 相似文献
45.
Sharma Deepika Radha Anu Kumar Pretam Kumar Sandeep Jassal Amanpreet K. Lata Suman Vikas Pandey Sushil K. 《Transition Metal Chemistry》2020,45(8):531-544
Transition Metal Chemistry - Nickel(II) complexes with octahedral coordination stabilized by N-donor ligands corresponds to [{(ArO)2PS2}2Ni·L2] [Ar = 4-(C2H5)C6H4 (3), and... 相似文献
46.
Ranjit Bag Sourav Kar Suvam Saha Suman Gomosta Beesam Raghavendra Thierry Roisnel Sundargopal Ghosh 《化学:亚洲杂志》2020,15(6):780-786
Triply‐bridging bis‐{hydrido(borylene)} and bis‐borylene species of groups 6, 8 and 9 transition metals are reported. Mild thermolysis of [Fe2(CO)9] with an in situ produced intermediate, generated from the low‐temperature reaction of [Cp*WCl4] (Cp*=η5‐C5Me5) and [LiBH4?THF] afforded triply‐bridging bis‐{hydrido(borylene)}, [(μ3‐BH)2H2{Cp*W(CO)2}2{Fe(CO)2}] ( 1 ) and bis‐borylene, [(μ3‐BH)2{Cp*W(CO)2}2{Fe(CO)3}] ( 2 ). The chemical bonding analyses of 1 show that the B?H interactions in bis‐{hydrido (borylene)} species is stronger as compared to the M?H ones. Frontier molecular orbital analysis shows a significantly larger energy gap between the HOMO‐LUMO for 2 as compared to 1 . In an attempt to synthesize the ruthenium analogue of 1 , a similar reaction has been performed with [Ru3(CO)12]. Although we failed to get the bis‐{hydrido(borylene)} species, the reaction afforded triply‐bridging bis‐borylene species [(μ3‐BH)2{WCp*(CO)2}2{Ru(CO)3}] ( 2′ ), an analogue of 2 . In search for the isolation of bridging bis‐borylene species of Rh, we have treated [Co2(CO)8] with nido‐[(RhCp*)2(B3H7)], which afforded triply‐bridging bis‐borylene species [(μ3‐BH)2(RhCp*)2Co2(CO)4(μ‐CO)] ( 3 ). All the compounds have been characterized by means of single‐crystal X‐ray diffraction study; 1H, 11B, 13C NMR spectroscopy; IR spectroscopy and mass spectrometry. 相似文献
47.
Soujan Ghosh Swati Chowdhury Subrata Kundu Sudipta Sasmal Dimitrios Z. Politis Stelios M. Potirakis Masashi Hayakawa Suman Chakraborty Sandip K. Chakrabarti 《Entropy (Basel, Switzerland)》2022,24(1)
We focus on the possible thermal channel of the well-known Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the variation of Surface Latent Heat Flux (SLHF) as resulting from satellite observables. We demonstrate a spatio-temporal variation in the SLHF before and after a set of strong seismic events occurred in Kathmandu, Nepal, and Kumamoto, Japan, having magnitudes of 7.8, 7.3, and 7.0, respectively. Before the studied earthquake cases, significant enhancements in the SLHF were identified near the epicenters. Additionally, in order to check whether critical dynamics, as the signature of a complex phenomenon such as earthquake preparation, are reflected in the SLHF data, we performed a criticality analysis using the natural time analysis method. The approach to criticality was detected within one week before each mainshock. 相似文献
48.
49.
Abstract An efficient, atom-economic, one-pot protocol has been developed for the synthesis of highly functionalized dihydropyridines via four-component reactions of aromatic aldehydes, arylamines, malononitrile, and dimethylacetylenedicarboxylate in the presence of sodium hydroxide in ethanol. This domino reaction proceeded smoothly in good to excellent yields and offered several advantages, including short reaction time, simple experimental procedure, and applicability to a broad range of substrates. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
50.
Francis R. Costa Sudip Pradhan Udo Wagenknecht Anil K. Bhowmick Gert Heinrich 《Journal of Polymer Science.Polymer Physics》2010,48(22):2302-2311
In elastomer/organo clay nanocomposites, the morphological characteristics, and hence the mechanical properties, of the vulcanizates are strongly influenced by the organic modifier and the vulcanization process. When the elastomer itself undergoes strain‐induced crystallization, both the organic modifier and the dispersed filler particles could significantly influence the crystallization process. These phenomena are very common in case of natural rubber‐based vulcanizates. In this study, the similar effects have been demonstrated with carboxylated nitrile rubber (XNBR) and organically modified layered double hydroxide (O‐LDH)‐based nanocomposites. The effect of size of the organic modifier was obviously visible on the interlayer distance of O‐LDH and also on the morphological reorganization of the dispersed O‐LDH particles during vulcanization process. The strain‐induced crystallization of the XNBR was found to be strongly dependent on the morphological change that occurs during vulcanization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献