全文获取类型
收费全文 | 475篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 286篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 61篇 |
物理学 | 144篇 |
出版年
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 32篇 |
2012年 | 26篇 |
2011年 | 30篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 20篇 |
2007年 | 34篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 25篇 |
2003年 | 14篇 |
2002年 | 19篇 |
2001年 | 8篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1934年 | 2篇 |
1933年 | 2篇 |
排序方式: 共有494条查询结果,搜索用时 281 毫秒
61.
We measure polarization-resolved instantaneous patterns in a large-aspect ratio quasi-isotropic Nd:YAG laser. High correlation between the instantaneous orthogonal polarization patterns recorded at the earlier stages of the laser pulse has been found due to the strong cross saturation between both polarization modes. 相似文献
62.
Michael DG Adamson P Alexopoulos T Allison WW Alner GJ Anderson K Andreopoulos C Andrews M Andrews R Arms KE Armstrong R Arroyo C Auty DJ Avvakumov S Ayres DS Baller B Barish B Barker MA Barnes PD Barr G Barrett WL Beall E Becker BR Belias A Bergfeld T Bernstein RH Bhattacharya D Bishai M Blake A Bocean V Bock B Bock GJ Boehm J Boehnlein DJ Bogert D Border PM Bower C Boyd S Buckley-Geer E Bungau C Byon-Wagner A Cabrera A Chapman JD Chase TR Cherdack D Chernichenko SK Childress S Choudhary BC 《Physical review letters》2006,97(19):191801
This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.). 相似文献
63.
Reina M González-Coloma A Domínguez-Díaz D Cabrera R Giménez Mariño C Rodríguez ML Villarroel L 《Natural product research》2006,20(1):13-19
A new bioactive eremophilanolide, 1alpha-tigloyloxy-8betaH,10betaH-eremophil-7(11)-en-8alpha,12-olide, was isolated from Senecio poepigii and its structure was elucidated by spectral analysis. 1alpha-Angeloyloxy-8beta-methoxy-10betaH-eremophil-7(11)-en-8alpha,12-olide was also isolated. Antifungal and insect antifeedant properties were evaluated. 相似文献
64.
Europium-doped aluminophosphate glasses prepared by the melt-quenching technique have been studied by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The effects of silver and tin doping, and of further thermal processing on Eu3+ ions luminescence have been assessed. For the glass system containing only europium, Eu3+ PL observed under UV excitation is suggested to occur through energy transfer from the excited glass host. After silver and tin doping, an enhanced UV excited Eu3+ PL has been indicated to occur essentially due to radiative energy transfer from isolated Ag+ ions and/or two fold-coordinated Sn centers. Since thermal processing of the material leads to a quenching effect on Eu3+ PL and Ag nanoparticles (NPs) formation due to reduction of silver ions by tin, XPS was employed in order to investigate the possibility for Eu3+→Eu2+ reduction during HT as a potential source of the PL decrease. The data points towards Ag NPs as main responsible for the observed weakening of Eu3+ PL. 相似文献
65.
J.?M.?SorianoEmail authorView authors OrcID profile M.?Ordo?ez?Cabrera 《Mediterranean Journal of Mathematics》2018,15(1):23
Let X be a real Hilbert space and \(X^{*}\) its dual space. Let A be a strongly positive operator from X to \(X^{*}\). Sufficient conditions are provided to assert that a compact perturbation of A reaches a fixed value at least once and at most finitely many times. When the compact perturbation is linear, the value is reached just once. The same conclusions are obtained when operators map the space X into itself. As an application of our results two examples are given related to some types of integral equations. The proof of results is constructive and is based upon a continuation method. 相似文献
66.
In this paper, we classify all the multiplicity-free permutation characters of sporadic simple groups and their automorphism groups. This project is an application of the group theory system GAP, its character table library, and its library of tables of marks. 相似文献
67.
Let A be an algebra whose multiplication algebra M(A) is semiprime. We prove that, except in an exceptional case, the proper closed prime ideals of A are the maximal closed ideals of A, for the closure operations π and ?. In fact, these sets agree for both closures. The same can be said in M(A) for the closure operations π and ?′. Moreover, we establish the relationships between the proper closed prime ideals of A and the ones of the algebras M(A),U and A/U, for a given ideal U of A. 相似文献
68.
69.
Jeon JY Kim YH Cabrera D Bassett J 《The Journal of the Acoustical Society of America》2008,123(6):4272-4282
Opera performance conveys both visual and auditory information to an audience, and so opera theaters should be evaluated in both domains. This study investigates the effect of static visual and auditory cues on seat preference in an opera theater. Acoustical parameters were measured and visibility was analyzed for nine seats. Subjective assessments for visual-only, auditory-only, and auditory-visual preferences for these seat positions were made through paired-comparison tests. In the cases of visual-only and auditory-only subjective evaluations, preference judgment tests on a rating scale were also employed. Visual stimuli were based on still photographs, and auditory stimuli were based on binaural impulse responses convolved with a solo tenor recording. For the visual-only experiment, preference is predicted well by measurements taken related to the angle of seats from the theater midline at the center of the stage, the size of the photographed stage view, the visual obstruction, and the distance from the stage. Sound pressure level was the dominant predictor of auditory preference in the auditory-only experiment. In the cross-modal experiments, both auditory and visual preferences were shown to contribute to overall impression, but auditory cues were more influential than the static visual cues. The results show that both a positive visual-only or a positive auditory-only evaluations positively contribute to the assessments of seat quality. 相似文献
70.
Rodríguez-Calvillo Pablo Ferrer Nuria Cabrera José-María 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1393-1403
Journal of Thermal Analysis and Calorimetry - The thermal behavior of two copper alloys, with 0.2 and 0.5 mass % of Mg, was analyzed after severe plastic deformation processing by Equal Channel... 相似文献