全文获取类型
收费全文 | 667篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
化学 | 358篇 |
晶体学 | 9篇 |
力学 | 36篇 |
数学 | 115篇 |
物理学 | 173篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 20篇 |
2014年 | 12篇 |
2013年 | 41篇 |
2012年 | 39篇 |
2011年 | 47篇 |
2010年 | 36篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 4篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1922年 | 1篇 |
排序方式: 共有691条查询结果,搜索用时 15 毫秒
681.
Numerical aspects of two-scale modeling of epoxy/glass composites are presented. The homogenization process is carried out under consideration of periodic boundary constraints (PBC) of the representative volume element (RVE) due to the periodic structure of glassfiber reinforced epoxy systems. The introduction of artificial constraints for computing macro-stresses and macro-moduli is presented by giving the modified algorithmic treatment of a two-scale approach using PBC. The proposed algorithm is applied to an ISO 527 epoxy/glass test specimen. The results of computations considering or not considering interphases and interfaces within the composite are compared. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
682.
Several recent contributions formalize and analyze binary choices games with externalities as those described by Schelling. Nevertheless, in the real world choices are not always binary, and players have often to decide among more than two alternatives. These kinds of interactions are examined in game theory where, starting from the well known rock-paper-scissor game, several other kinds of strategic interactions involving more than two choices are examined. In this paper we investigate how the dynamics evolve introducing one more option in binary choice games with externalities. The dynamics we obtain are always in a stable regime, that is, the structurally stable dynamics are only attracting cycles, but of any possible positive integer as period. We show that, depending on the structure of the game, the dynamics can be quite different from those existing when considering binary choices. The bifurcation structure, due to border collisions, is explained, showing the existence of so-called big-bang bifurcation points. 相似文献
683.
684.
Lidiani Figueiredo Santana Bruna Larissa Spontoni do Espirito Santo Mariana Bento Tatara Fbio Juliano Negro Júlio Croda Flvio Macedo Alves Wander Fernando de Oliveira Filiú Leandro Fontoura Cavalheiro Carlos Eduardo Domingues Nazrio Marcel Arakaki Asato Bernardo Bacelar de Faria Valter Arago do Nascimento Rita de Cssia Avellaneda Guimares Karine de Cssia Freitas Priscila Aiko Hiane 《Molecules (Basel, Switzerland)》2022,27(19)
Background: Studies indicate that different parts of Carica papaya Linn have nutritional properties that mean it can be used as an adjuvant for the treatment of various pathologies. Methods: The fatty acid composition of the oil extracted from the seeds of Carica papaya Linn was evaluated by gas chromatography, and an acute toxicity test was performed. For the experiment, Swiss mice were fed a balanced or high-fat diet and supplemented with saline, soybean oil, olive oil, or papaya seed oil. Oral glucose tolerance and insulin sensitivity tests were performed. After euthanasia, adiposity, glycemia, total cholesterol and fractions, insulin, resistin, leptin, MCP-1, TNF-α, and IL-6 and the histology of the liver, pancreas, and adipose tissue were evaluated. Results: Papaya seed oil showed predominance of monounsaturated fatty acids in its composition. No changes were observed in the acute toxicity test. Had lower food intake in grams, and caloric intake and in the area of adipocytes without minimizing weight gain or adiposity and impacting the liver or pancreas. Reductions in total and non-HDL-c, LDL-c, and VLDL-c were also observed. The treatment had a hypoglycemic and protective effect on insulin resistance. Supplementation also resulted in higher leptin and lower insulin and cytokine resistance. Conclusions: Under these experimental conditions, papaya seed oil led to higher amounts of monounsaturated fatty acids and had hypocholesterolemic, hypotriglyceridemic, and hypoglycemic effects. 相似文献
685.
Lazare Saladin Victor Breton Ophélie Dal Pra Dr. Andrey S. Klymchenko Dr. Lydia Danglot Prof. Pascal Didier Dr. Mayeul Collot 《Angewandte Chemie (International ed. in English)》2023,62(4):e202215085
We herein present a new concept to produce dual-color photoconvertible probes based on a mechanism called Directed Photooxidation Induced Conversion (DPIC). As a support of this mechanism, styryl-coumarins ( SCs ) bearing Aromatic Singlet Oxygen Reactive Moieties (ASORMs) like furan and pyrrole have been synthesized. SCs are bright fluorophores, which undergo a hypsochromic conversion upon visible light irradiation due to directed photooxidation of the ASORM that leads to the disruption of conjugation. SC-P , a yellow emitting probe bearing a pyrrole moiety, converts to a stable blue emitting coumarin with a 68 nm shift allowing the photoconversion and tracking of lipid droplet in live cells. This new approach might pave the way to a new generation of photoconvertible dyes for advanced bioimaging applications. 相似文献
686.
Keisuke Santo Kentaro Uchida Dr. Keisuke Fujimoto Dr. Toshiyasu Inuzuka Prof. Dr. Kazutaka Hirakawa Dr. Tetsuya Sengoku Prof. Dr. Masaki Takahashi 《European journal of organic chemistry》2023,26(9):e202201479
Newly designed fluorophore systems with feather-like structures were constructed by connecting bisanthracene building units via a concise reaction sequence of bromination, etherification, and desilylation. Spectroscopic characterizations revealed that all of the fluorophore systems achieved high light absorptivity and high emission efficiency by preventing closely spaced anthracene chromophores from mutual interactions to reduce concomitant energy loss by fluorescence quenching. The application of fluorophore systems for the preparation of light-harvesting dyad materials has successfully demonstrated their potential utility as versatile photofunctional tools. 相似文献
687.
Dr. Ana M. Ortuño Dr. Pablo Reiné Prof. Luis Álvarez de Cienfuegos Dr. Irene R. Márquez Dr. Wynand Dednam Prof. Enrico B. Lombardi Prof. Juan J. Palacios Dr. Edmund Leary Prof. Giovanna Longhi Prof. Vladimiro Mujica Dra. Alba Millán Dra. M. Teresa González Linda A. Zotti Dra. Delia Miguel Prof. Juan M. Cuerva 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218640
We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau-length distributions, attributed to different conformations of the helical structures. The large chiro-optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state-of-the-art Density Functional Theory (DFT) calculations, including a fully ab-initio estimation of the CISS-originating spin polarization which is done, for the first time, for a realistic molecular system. 相似文献
688.
Nives Hribernik Denisa Vargová Marlene C. S. Dal Colle Jia Hui Lim Giulio Fittolani Yang Yu Junki Fujihara Kai Ludwig Peter H. Seeberger Yu Ogawa Martina Delbianco 《Angewandte Chemie (International ed. in English)》2023,62(47):e202310357
Peptides and nucleic acids with programmable sequences are widely explored for the production of tunable, self-assembling functional materials. Herein we demonstrate that the primary sequence of oligosaccharides can be designed to access materials with tunable shapes and properties. Synthetic cellulose-based oligomers were assembled into 2D or 3D rod-like crystallites. Sequence modifications within the oligosaccharide core influenced the molecular packing and led to the formation of square-like assemblies based on the rare cellulose IVII allomorph. In contrast, modifications at the termini generated elongated aggregates with tunable surfaces, resulting in self-healing supramolecular hydrogels. 相似文献
689.
Larissa Bessler Lea-Marie Vogt Marc Lander Dr. Christina Dal Magro Dr. Patrick Keller Dr. Jonas Kühlborn Dr. Christopher J. Kampf Prof. Dr. Till Opatz Prof. Dr. Mark Helm 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217128
The fields of RNA modification and RNA damage both exhibit a plethora of non-canonical nucleoside structures. While RNA modifications have evolved to improve RNA function, the term RNA damage implies detrimental effects. Based on stable isotope labelling and mass spectrometry, we report the identification and characterisation of 2-methylthio-1,N6-ethenoadenosine (ms2ϵA), which is related to 1,N6-ethenoadenine, a lesion resulting from exposure of nucleic acids to alkylating chemicals in vivo. In contrast, a sophisticated isoprene labelling scheme revealed that ms2ϵA biogenesis involves cleavage of a prenyl moiety in the known transfer RNA (tRNA) modification 2-methylthio-N6-isopentenyladenosine (ms2i6A). The relative abundance of ms2ϵA in tRNAs from translating ribosomes suggests reduced function in comparison to its parent RNA modification, establishing the nature of the new structure in a newly perceived overlap of the two previously separate fields, namely an RNA modification damage. 相似文献
690.
Modeling of complex mechanisms leading to the functioning of the heart has been an active field of research since decades. Difficulties associated with in vivo experiments motivate the utilization of computational models in order to gain a better appreciation of heart electromechanics. Although rate dependent behaviour of the orthotropic passive heart tissue has been comprehensively studied in the literature [1], effects of this phenomenon on fully coupled cardiac electromechanics are unrevealed yet. Therefore, this contribution is concerned with the investigation of viscous effects on the electromechanical response of the myocardium. To this end, we adopt the fully implicit finite element framework which strongly couples the mechanical and electrophysiological problem of the myocardium in a mono- and bi-domain setting [2,3], respectively. Viscous effects, however, are consistently embedded into this framework by making use of the orthotropic viscoelastic material model for the passive myocardium, which considers different relaxation mechanisms for the different orientation directions [5]. The performance of the proposed model is assessed by comparing finite element simulations of spiral waves in heart tissue for elastic and viscoelastic formulations. We further investigate the influence of viscosity on the defibrillation phenomenon by means of the finite element formulation of bidomain electrophysiology. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献