全文获取类型
收费全文 | 125篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 62篇 |
力学 | 5篇 |
数学 | 47篇 |
物理学 | 18篇 |
出版年
2023年 | 1篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有132条查询结果,搜索用时 31 毫秒
51.
52.
Eleftherios Tachtsis 《Archive for Mathematical Logic》2018,57(5-6):665-686
In set theory without the axiom of choice, we investigate the deductive strength of the principle “every topological space with the minimal cover property is compact”, and its relationship with certain notions of finite as well as with properties of linearly ordered sets and partially ordered sets. 相似文献
53.
Nikolaos Politakos Eleftherios Ntoukas Apostolos Avgeropoulos Vahik Krikorian Brian D. Pate Edwin L. Thomas Randal M. Hill 《Journal of Polymer Science.Polymer Physics》2009,47(23):2419-2427
We report the observation of a cubic phase consistent with the double gyroid structure in strongly segregated diblock copolymers of PS‐b‐PDMS over a volume fraction (φPDMS) range of ~0.39 to 0.45. The samples have respective molecular weights of 127 kg/mol and 73 kg/mol and degree of segregation Nχ equal to 187 and 106, respectively, at annealing temperature of 130 °C. It is important to highlight that two out of the total four samples investigated, exhibited hexagonally close packed cylindrical domains of PDMS and alternating lamellae at φPDMS = 0.39 and 0.45, respectively, indicating the possible narrow range of the DG morphology for the specific diblock copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2419–2427, 2009 相似文献
54.
Siskos AP Baerga-Ortiz A Bali S Stein V Mamdani H Spiteller D Popovic B Spencer JB Staunton J Weissman KJ Leadlay PF 《Chemistry & biology》2005,12(10):1145-1153
A system is reported for the recombinant expression of individual ketoreductase (KR) domains from modular polyketide synthases (PKSs) and scrutiny of their intrinsic specificity and stereospecificity toward surrogate diketide substrates. The eryKR(1) and the tylKR(1) domains, derived from the first extension module of the erythromycin PKS and the tylosin PKS, respectively, both catalyzed reduction of (2R, S)-2-methyl-3-oxopentanoic acid N-acetylcysteamine thioester, with complete stereoselectivity and stereospecificity, even though the substrate is not tethered to an acyl carrier protein or an intact PKS multienzyme. In contrast, and to varying degrees, the isolated enzymes eryKR(2), eryKR(5), and eryKR(6) exercised poorer control over substrate selection and the stereochemical course of ketoreduction. These data, together with modeling of diketide binding to KR(1) and KR(2), demonstrate the fine energetic balance between alternative modes of presentation of ketoacylthioester substrates to KR active sites. 相似文献
55.
Marinos Xagoraris Alexandra Skouria Panagiota-Kyriaki Revelou Eleftherios Alissandrakis Petros A. Tarantilis Christos S. Pappas 《Molecules (Basel, Switzerland)》2021,26(12)
This study aimed at an experimental design of response surface methodology (RSM) in the optimization of the dominant volatile fraction of Greek thyme honey using solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). For this purpose, a multiple response optimization was employed using desirability functions, which demand a search for optimal conditions for a set of responses simultaneously. A test set of eighty thyme honey samples were analyzed under the optimum conditions for validation of the proposed model. The optimized combination of isolation conditions was the temperature (60 °C), equilibration time (15 min), extraction time (30 min), magnetic stirrer speed (700 rpm), sample volume (6 mL), water: honey ratio (1:3 v/w) with total desirability over 0.50. It was found that the magnetic stirrer speed, which has not been evaluated before, had a positive effect, especially in combination with other factors. The above-developed methodology proved to be effective in the optimization of isolation of specific volatile compounds from a difficult matrix, like honey. This study could be a good basis for the development of novel RSM for other monofloral honey samples. 相似文献
56.
Kyriakos Keremedis Eleftherios Tachtsis 《Proceedings of the American Mathematical Society》2007,135(4):1205-1211
We show that the existence of a countable, first countable, zero-dimensional, compact Hausdorff space which is not second countable, hence not metrizable, is consistent with ZF.
57.
Bernhard Pemmer Jochen G. Hofstaetter Florian Meirer Stephan Smolek Peter Wobrauschek Rolf Simon Robyn K. Fuchs Matthew R. Allen Keith W. Condon Susan Reinwald Roger J. Phipps David B. Burr Eleftherios P. Paschalis Klaus Klaushofer Christina Streli Paul Roschger 《Journal of synchrotron radiation》2011,18(6):835-841
Based on clinical trials showing the efficacy to reduce vertebral and non‐vertebral fractures, strontium ranelate (SrR) has been approved in several countries for the treatment of postmenopausal osteoporosis. Hence, it is of special clinical interest to elucidate how the Sr uptake is influenced by dietary Ca deficiency as well as by the formula of Sr administration, SrR versus strontium chloride (SrCl2). Three‐month‐old ovariectomized rats were treated for 90 days with doses of 25 mg kg?1 d?1 and 150 mg kg?1 d?1 of SrR or SrCl2 at low (0.1% Ca) or normal (1.19% Ca) Ca diet. Vertebral bone tissue was analysed by confocal synchrotron‐radiation‐induced micro X‐ray fluorescence and by backscattered electron imaging. Principal component analysis and k‐means clustering of the acquired elemental maps of Ca and Sr revealed that the newly formed bone exhibited the highest Sr fractions and that low Ca diet increased the Sr uptake by a factor of three to four. Furthermore, Sr uptake in bone of the SrCl2‐treated animals was generally lower compared with SrR. The study clearly shows that inadequate nutritional calcium intake significantly increases uptake of Sr in serum as well as in trabecular bone matrix. This indicates that nutritional calcium intake as well as serum Ca levels are important regulators of any Sr treatment. 相似文献
58.
Spiros Kostopoulos Konstantinos Sidiropoulos Dimitris Glotsos Emmanouil Athanasiadis Konstantina Boutsikou Eleftherios Lavdas Georgia Oikonomou Ioannis V. Fezoulidis Marianna Vlychou Michael Hantes Dionisis Cavouras 《Magnetic resonance imaging》2013
The aim was to design a pattern-recognition (PR) system for discriminating between normal and pathological knee articular cartilage of the medial femoral (MFC) and tibial condyles (MTC). The data set comprised segmented regions of interest (ROIs) from coronal and sagittal 3-T magnetic resonance images of the MFC and MTC cartilage of young patients, 28 with abnormality-free knee and 16 with pathological findings. The PR system was designed employing the probabilistic neural network classifier, textural features from the segmented ROIs and the leave-one-out evaluation method, while the PR system's precision to “unseen” data was assessed by employing the external cross-validation method. Optimal system design was accomplished on a consumer graphics processing unit (GPU) using Compute Unified Device Architecture parallel programming. PR system design on the GPU required about 3.5 min against 15 h on a CPU-based system. Highest classification accuracies for the MFC and MTC cartilages were 93.2% and 95.5%, and accuracies to “unseen” data were 89% and 86%, respectively. The proposed PR system is housed in a PC, equipped with a consumer GPU, and it may be easily retrained when new verified data are incorporated in its repository and may be of value as a second-opinion tool in a clinical environment. 相似文献
59.
Eleftherios Lavdas Panayiotis Mavroidis Theofilos Topaltzikis Vasileios Slatinopoulos Violeta Roka Anna Vlachopoulou Nikos Papanikolaou Sotirios Stathakis Eftichia Kapsalaki Georgios Batsikas 《Magnetic resonance imaging》2013
The purpose of this study is to report the significant differences found in the identification of lesions in cervical spinal cord of two patients with multiple sclerosis when using the BLADE T2-TSE and BLADE T2-TIRM sequences as opposed to the conventional T2-TSE and T2-TIRM sequences for sagittal acquisition at 1.5 T. In both patients, one more lesion was identified with the BLADE sequences than with the conventional ones. Consequently, we suggest the use of BLADE T2-TSE and BLADE T2-TIRM sequences in place of conventional ones for sagittal examination of the cervical spinal cord of multiple sclerosis patients. The advantages of ΤΙRΜ to reveal the pathology of the cervical spinal cord and the advantage of BLADE sequences to improve image quality should be combined in a sequence that could be ideal for cervical spinal cord examinations. 相似文献
60.
Eleftherios Couzoudis Philipp Renner 《Mathematical Methods of Operations Research》2013,77(3):459-472
We present a new way to solve generalized Nash equilibrium problems. We assume the feasible set to be compact. Furthermore all functions are assumed to be polynomials. However we do not impose convexity on either the utility functions or the action sets. The key idea is to use Putinar’s Positivstellensatz, a representation result for positive polynomials, to replace each agent’s problem by a convex optimization problem. The Nash equilibria are then feasible solutions to a system of polynomial equations and inequalities. Our application is a model of the New Zealand electricity spot market with transmission losses based on a real dataset. 相似文献