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排序方式: 共有345条查询结果,搜索用时 16 毫秒
1.
Physics of Atomic Nuclei - In this paper, the analysis of the relation between the multiplication factor of neutrons of the multiplying system measured in critical experiments and the system... 相似文献
2.
Yushkov E. V. Lukin A. S. Sokoloff D. D. 《Journal of Experimental and Theoretical Physics》2020,130(6):935-944
Journal of Experimental and Theoretical Physics - We compare the classical mean-field dynamo model proposed by Steenbeck, Krause, and Rädler to describe the generation of large-scale magnetic... 相似文献
3.
Structural analysis using powder X-ray diffraction data has overcome many obstacles and nowadays is readily applicable for structural analysis of all types of compounds and materials. Being less straightforward than single crystal diffraction, it requires significant users’ input and consequently, implementation of standardized tools to assess the accuracy of crystal structures. This article discusses potential errors in crystal structure solution and refinement of small-molecule structures obtained from PXRD data. Moreover, it proposes how accuracy of these structures can be improved by using high-quality PXRD data, complementary external analytical techniques, knowledge stored in crystal structure databases, as well as an approach to search the parameter space to avoid local minima in testing different sets of geometry restraints. 相似文献
4.
N. F. Morozov D. A. Indeitsev A. V. Lukin I. A. Popov O. V. Privalova D. Yu. Skubov L. V. Shtukin 《Doklady Physics》2016,61(11):562-566
Branching of equilibria of a system of three parallel conducting nano/microlayers, which is used to detect changes in the external and internal mechanical and electric characteristics (for example, conductivity, tension force, and gap between layers), has been investigated. A change in the physical parameters may cause asymmetric bending of the outer layers and deformation of the formerly neutral middle layer. By changing the current in one of the outer layers slowly, their initial symmetry (neutrality of the inner layer) can be restored and the change that occurred in the parameters can be determined. 相似文献
5.
Highly Efficient One‐Pot Preparation of 1,2,4‐Oxadiazoles in the Presence of Diazabicycloundecene 下载免费PDF全文
New highly efficient method for the cyclization of acylamidoximes in the presence of diazabicycloundecene was developed and incorporated into a general and practical one‐pot synthesis of 1,2,4‐oxadiazoles (11 examples, 85–97% yields). 相似文献
6.
Artem Cherepakha Vladimir O. Kovtunenko Andrey Tolmachev Oleg Lukin 《Journal of heterocyclic chemistry》2013,50(5):1071-1077
A set of synthetic procedures was developed to yield functionalized pyrido‐, pyrimido‐, and thiazo‐annulated thiadiazine‐1,1‐dioxides on a preparative scale. In all cases the thiadiazine‐1,1‐dioxide ring closure was carried out through a reaction of hetaryl‐sulfonyl chlorides with amidines under mild noncatalytic conditions. In the case of 2‐chloropyridine‐3‐sulfonyl chloride derivatives and 2,4‐dichlorothiazole‐5‐sulfonyl chloride open‐chain sulfonylated amidine intermediates were isolated and then subjected to the cyclization step. The reaction with 2,4‐dichloropyrimidine‐5‐sulfonyl chloride gave rise to the corresponding thiadiazine‐1,1‐dioxides in one‐pot. Similarly, a reaction of 2‐chloropyridine‐3‐sulfonamide with lactime ethers proceeded in one‐pot readily giving the corresponding thiadiazine‐1,1‐dioxides. Remaining chlorine atoms on the prepared hetaryl‐annulated benzothiadiazine‐1,1‐dioxides readily undergo aromatic nucleophilic displacement reactions serving thus as additional variation points for the design of biologically potent compounds. 相似文献
7.
Alexey V. Laptev Dmitrii E. Pugachev Alexey Yu. Lukin Andrei V. Nechaev Nikolay E. Belikov Olga V. Demina Petr P. Levin Andrey A. Khodonov Andrey F. Mironov Sergei D. Varfolomeev Vitalii I. Shvets 《Mendeleev Communications》2013,23(4):199-201
A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn2+ and Cu2+ ions were prepared and characterized by physicochemical methods of analysis. 相似文献
8.
Karen J. Ardila‐Fierro Stipe Lukin Martin Etter Krunoslav Uarevi Ivan Halasz Carsten Bolm Jos G. Hernndez 《Angewandte Chemie (International ed. in English)》2020,59(32):13458-13462
Recent progress in the field of mechanochemistry has expanded the discovery of mechanically induced chemical transformations to several areas of science. However, a general fundamental understanding of how mechanochemical reactions by ball milling occur has remained unreached. For this, we have now implemented in situ monitoring of a mechanochemically induced molecular rearrangement by synchrotron X‐ray powder diffraction, Raman spectroscopy, and real‐time temperature sensing. The results of this study demonstrate that molecular rearrangements can be accomplished in the solid state by ball milling and how in situ monitoring techniques enable the visualization of changes occurring at the exact instant of a molecular migration. The mechanochemical benzil–benzilic acid rearrangement is the focal point of the study. 相似文献
9.
Giacomo Bergamini Dr. Paola Ceroni Prof. Vincenzo Balzani Prof. Ramchandra Kandre Dr. Oleg Lukin Dr. 《Chemphyschem》2009,10(1):265-269
Novel dendrimers G2PC and G4PC consisting of a p‐pentaphenylene core ( PC ) appended in the para position with two second‐generation ( G2 ) or two fourth‐generation ( G4 ) sulfonimide branches and two n‐octyl chains, as well as a model compound of the pentaphenylene core ( G0PC ), are prepared. The photophysical properties (absorption, emission, and excitation spectra; fluorescence decay lifetime; and fluorescence anisotropy spectra) of the three compounds are investigated under different experimental conditions (dichloromethane solution and solid state at 293 K, dichloromethane/methanol rigid matrix at 77 K). In the absorption spectra contributions from both the branches and the core can be clearly identified. The fluorescence spectra show only the characteristic fluorescence of the pentaphenylene unit with λmax around 410 nm in fluid solution and 420 nm in the solid state. In solution the fluorescence quantum yields are 0.78, 0.76, and 0.72 for G0PC , G2PC , and G4PC , respectively, and the fluorescence lifetime is about 0.7 ns in all cases. Energy transfer from the chromophoric groups of the dendrimer branches to the core does not occur. The three compounds show the same, high steady‐state anisotropy value (0.35) in dilute rigid‐matrix solution at 77 K. In dichloromethane at 293 K, the increasing anisotropy values along the series G0PC (0.17), G2PC (0.27), and G4PC (0.32), with increasing molecular volume of the three compounds, show that depolarization takes place by molecular rotation. In the solid state the anisotropy is very low (0.015, 0.017, and 0.035 for G0PC , G2PC , and G4PC , respectively), probably because of fast depolarization via energy migration. 相似文献
10.