全文获取类型
收费全文 | 506篇 |
免费 | 40篇 |
国内免费 | 9篇 |
专业分类
化学 | 108篇 |
晶体学 | 1篇 |
力学 | 16篇 |
综合类 | 6篇 |
数学 | 140篇 |
物理学 | 284篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 27篇 |
2013年 | 44篇 |
2012年 | 23篇 |
2011年 | 27篇 |
2010年 | 33篇 |
2009年 | 31篇 |
2008年 | 26篇 |
2007年 | 30篇 |
2006年 | 31篇 |
2005年 | 30篇 |
2004年 | 23篇 |
2003年 | 31篇 |
2002年 | 14篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 4篇 |
排序方式: 共有555条查询结果,搜索用时 15 毫秒
81.
In this paper, we prove the existence and uniqueness of the local mild solution to the Cauchy problem of the n‐dimensional (n≥3) Wigner–Poisson–BGK equation in the space of some integrable functions whose inverse Fourier transform are integrable. The main difficulties in establishing mild solution are to derive the boundedness and locally Lipschitz properties of the appropriate nonlinear terms in the Wiener algebra. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
82.
T. Dube 《Acta Mathematica Hungarica》2007,116(3):223-237
By introducing a conservative notion of functional compactness to frames and using frame-theoretic techniques, we identify
two classes of topological spaces that can be densely embedded in functionally compact ones. Since θ-open elements of frames (corresponding in spaces to complements of Veličko’s [15] θ-closed subspaces) play an important role in functional compactness, we also study the concept of co-rigidity in frames and
show that it is enjoyed by all θ-open elements of functionally compact frames.
Dedicated to the memory of Sergio Salbany 相似文献
83.
Perttu Permi Ilkka Kilpelinen Arto Annila 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,146(2):255
Transverse relaxation-optimized NMR experiment (TROSY) for the measurement of three-bond scalar coupling constant between 1Hαi−1 and 15Ni defining the dihedral angle ψ is described. The triple-spin-state-selective experiment allows measurement of 3JHαN from 13Cα, 15N, and 1HN correlation spectra H2O with minimum resonance overlap. Transverse relaxation of 13Cα spin is minimized by using spin-state-selective filtering and by acquiring a signal longer in 15N-dimension in a manner of semi-constant-time TROSY evolution. The 3JHαN values obtained with the proposed α/β-HN(CO)CA-J TROSY scheme are in good agreement with the values measured earlier from ubiquitin in D2O using the HCACO[N] experiment. 相似文献
84.
85.
利用Nd∶YAG调Q单脉冲激光和自由脉冲激光对硬膜窄带干涉滤光片进行激光损伤阈值的测试,并且采用表面热透镜技术测量了滤光片的吸收率。实验发现:窄带干涉滤光片的吸收率和激光损伤阈值强烈依赖于辐照激光波长与窄带干涉滤光片通带的相对位置;在调Q单脉冲激光作用下,不同中心波长的滤光片损伤形貌存在明显的差别,而在自由脉冲激光作用下,各滤光片的损伤形貌则趋于相同,均表现为典型的热熔烧蚀破坏。根据实验结果,结合损伤形貌,通过驻波场理论对激光作用下滤光片内电场分布的分析与模拟,探讨了两种激光模式作用下滤光片的损伤特征和损伤机理的不同特点。 相似文献
86.
87.
正弦变化的振幅型光瞳滤波器 总被引:6,自引:0,他引:6
光瞳滤波器作为实现超分辨的基本元件之一,它的设计以及制作都非常重要。设计了一种正弦变化的振幅型光瞳滤波器,可以通过调节少量的参量实现各种不同的超分辨模式。选择正弦函数的周期以及光瞳中心点透过率变化两个参量来实现对最终超分辨效果的调节。数值计算结果表明:在整个人射光瞳上的透过率瞳函数分布具有0.5~2个正弦振幅周期时,较为合适。小于0.5个周期将不会有任何超分辨效果,大于2个周期超分辨效果反而变差。数值计算中还注意到,当周期数为整数时,斯特雷尔比将保持0.25不变。对正弦变化振幅型光瞳滤波器的计算结果,显示了其特殊的性质,对实际中制作正弦变化振幅型光瞳滤波器有一定的指导作用。 相似文献
88.
增量维纳滤波法在波前探测解卷积中的应用 总被引:6,自引:3,他引:3
一个常规的自适应光学系统通常包含三个重要环节:波前探测、波前校正和波前重构。因此对系统的技术要求非常高,造成系统复杂,成本昂贵。基于哈特曼-夏克波前探测的图像解卷积处理就是“事后”处理的一种,它省去了波前校正环节,使常规的自适应光学系统得到简化,降低了系统成本。其基本原理为对瞬时波面进行短时间曝光探测,同时记录相应的短时间曝光图像,来进行解卷积处理。将增量维纳滤波法应用于基于哈特曼-夏克波前探测的解卷积中,并对室内模拟点源情况下的三组畸变光斑图像数据进行了解卷积恢复处理。结果表明,将增量维纳滤波法应用于基于波前探测的解卷积是完全可行的,在室内模拟点源情况下,恢复的图像可以达到衍射极限分辨力。与维纳滤波相比,它扩展了噪声抑制因子的选取范围,在噪声抑制因子选取不正确的情况下,仍能得到比维纳滤波更好的结果。 相似文献
89.
A simple, inexpensive sample preparation procedure, based on the matrix solid-phase dispersion (MSPD) technique, for the determination of six UV filters: 2-ethylhexyl salicylate (EHS), 3,3,5-trimethylcyclohexyl salicylate (Homosalate, HMS), 3-(4-methylbenzylidene) camphor (4-MBC), isoamyl-p-methoxycinnamate (IAMC), 2-ethylhexyl-p-methoxycinnamate (EHMC) and octocrylene (OCR), in dust from indoor environments is presented and the influence of several operational parameters on the extraction performance discussed. Under the final working conditions, sieved samples (0.5 g) were mixed with the same amount of anhydrous sodium sulphate and dispersed with 2 g of octadecyl bonded silica (C18) in a mortar with a pestle. This blend was transferred to a polypropylene solid-phase extraction cartridge containing 2 g of activated silica, as the clean-up co-sorbent. The cartridge was first rinsed with 5 mL of n-hexane and the analytes were then recovered with 4 mL of acetonitrile. This extract was adjusted to 1 mL, filtered and the compounds were determined by gas chromatography combined with tandem mass spectrometry (GC–MS/MS). Recoveries for samples spiked at two different concentrations ranged between 77% and 99%, and the limits of quantification (LOQs) of the method between 10 and 40 ng g−1. Analysis of settled dust from different indoor areas, including private flats, public buildings and vehicle cabins, showed that EHMC and OCR were ubiquitous in this matrix, with maximum concentrations of 15 and 41 μg g−1, respectively. Both UV filters were also quantified in dust reference material SRM 2585 for first time. EHS, 4-MBC and IAMC were detected in some of the analyzed samples, although at lower concentrations than EHMC and OCR. 相似文献
90.
The method for the minimum-phase (MP) finite impulse response (FIR) filter design, based on Rouche’s theorem from complex analysis is presented here. The filter is designed directly from a given specification. The method uses the cosine filters and the sharpening technique resulting in a multiplierless filter. 相似文献