全文获取类型
收费全文 | 1854篇 |
免费 | 110篇 |
国内免费 | 10篇 |
专业分类
化学 | 1002篇 |
晶体学 | 5篇 |
力学 | 46篇 |
数学 | 403篇 |
物理学 | 328篇 |
无线电 | 190篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 37篇 |
2020年 | 50篇 |
2019年 | 50篇 |
2018年 | 35篇 |
2017年 | 27篇 |
2016年 | 86篇 |
2015年 | 77篇 |
2014年 | 79篇 |
2013年 | 127篇 |
2012年 | 128篇 |
2011年 | 164篇 |
2010年 | 99篇 |
2009年 | 61篇 |
2008年 | 107篇 |
2007年 | 101篇 |
2006年 | 97篇 |
2005年 | 85篇 |
2004年 | 76篇 |
2003年 | 66篇 |
2002年 | 57篇 |
2001年 | 26篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 14篇 |
1997年 | 14篇 |
1996年 | 23篇 |
1995年 | 27篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 18篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1966年 | 2篇 |
1965年 | 4篇 |
排序方式: 共有1974条查询结果,搜索用时 953 毫秒
61.
62.
63.
Chelsea Weir Michelle L. Pantoya Gautham Ramachandran Tim Dallas Daniel Prentice Michael Daniels 《Journal of Electrostatics》2013,71(1):77-83
Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum (Al) with copper oxide (CuO) was the only mixture to ignite by electrostatic discharge. Under the loose powder conditions of these experiments, the Al–CuO minimum ignition energy (MIE) is 25 mJ and exhibited an electrical conductivity two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source. 相似文献
64.
65.
Ming-Sin Cheung Mahon L. Maguire Tim J. Stevens R. William Broadhurst 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,202(2):223-233
This paper introduces DANGLE, a new algorithm that employs Bayesian inference to estimate the likelihood of all possible values of the backbone dihedral angles ? and ψ for each residue in a query protein, based on observed chemical shifts and the conformational preferences of each amino acid type. The method provides robust estimates of ? and ψ within realistic boundary ranges, an indication of the degeneracy in the relationship between shift measurements and conformation at each site, and faithful secondary structure state assignments. When a simple degeneracy-based filtering procedure is applied, DANGLE offers an ideal compromise between accuracy and coverage when compared with other shift-based dihedral angle prediction methods. In addition, per residue analysis of shift/structure degeneracy has potential to be a useful new approach for studying the properties of unfolded proteins, with sufficient sensitivity to identify regions of residual structure in the acid denatured state of apomyoglobin. 相似文献
66.
The aim of this paper is to analyze 2D fringe pattern denoising performed by two chosen methods based on quasi-1D two-arm
spin filter and 2D discrete wavelet transform (DWT) signal decomposition and thresholding. The ultimate aim of this comparison
is to estimate which algorithm is better suited for high-accuracy measurements by phase shifting interferometry (PSI) with
the phase step evaluation using the lattice site approach. The spin filtering method proposed by Yu et al. (1994) was designed
to minimize possible fringe blur and distortion. The 2D DWT also presents such features due to a lossless nature of the signal
wavelet decomposition. To compare both methods, a special 2D histogram introduced by Gutman and Weber (1998) is used to evaluate
intensity errors introduced by each of the presented algorithms. 相似文献
67.
68.
Molecular Heterojunctions of Oligo(phenylene ethynylene)s with Linear to Cruciform Framework
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhongming Wei Tim Hansen Marco Santella Xintai Wang Christian R. Parker Xingbin Jiang Tao Li Magni Glyvradal Karsten Jennum Emil Glibstrup Nicolas Bovet Xiaowei Wang Wenping Hu Gemma C. Solomon Mogens Brøndsted Nielsen Xiaohui Qiu Thomas Bjørnholm Kasper Nørgaard Bo W. Laursen 《Advanced functional materials》2015,25(11):1700-1708
Electrical transport properties of molecular junctions are fundamentally affected by the energy alignment between molecular frontier orbitals (highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO)) and Fermi level (or work function) of electrode metals. Dithiafulvene (DTF) is used as substituent group to the oligo(phenylene ethynylene) (OPE) molecular wires and different molecular structures based on OPE3 backbone (with linear to cruciform framework) are achieved, with viable molecular orbitals and HOMO–LUMO energy gaps. OPE3, OPE3–DTF, and OPE3–tetrathiafulvalene (TTF) can form good self‐assembled monolayers (SAMs) on Au substrates. Molecular heterojunctions based on these SAMs are investigated using conducting probe–atomic force microscopy with different tips (Ag, Au, and Pt) and Fermi levels. The calibrated conductance values follow the sequence OPE3–TTF > OPE3–DTF > OPE3 irrespective of the tip metal. Rectification properties (or diode behavior) are observed in case of the Ag tip for which the work function is furthest from the HOMO levels of the OPE3s. Quantum chemical calculations of the transmission qualitatively agree with the experimental data and reproduce the substituent effect of DTF. Zero‐bias conductance, and symmetric or asymmetric couplings to the electrodes are investigated. The results indicate that improved fidelity of molecular transport measurements may be achieved by systematic studies of homologues series of molecular wires applying several different metal electrodes. 相似文献
69.
Egbert Müller Judith Vajda Djuro Josic Tim Schröder Romain Dabre Tim Frey 《Journal of separation science》2013,36(8):1327-1334
An essential part of the modulation of protein‐binding capacity in hydrophobic interaction chromatography is the buffer‐salt system. Besides using “single” electrolytes, multicomponent electrolyte mixtures may be used as an additional tool. Both the protein solubility and the binding capacity depend on the position of a salt in the so‐called Hofmeister series. Specific interactions are observed for an individual protein‐salt combination. For salt mixtures, selectivity, recovery, and binding capacity do not behave like for the single salts that are positioned in between the two mixed components in the Hofmeister series, as the continuous correlation would suggest. Thus, finding strategies for mixed salts could potentially lead to improved capacities in hydrophobic interaction chromatography. Mixtures of ammonium sulfate, sodium citrate, sodium sulfate, sodium chloride, sodium acetate, and glycine were used to investigate the binding capacities for lysozyme and a monoclonal antibody on various hydrophobic resins. Resin capacity for two investigated proteins increases when mixtures consisting of a chaotropic and a kosmotropic salt are applied. It seems to be related to the rather basic isoelectric points of the proteins. 相似文献
70.
2,2-Dimethyl-4-methoxychromans (1–12) have been converted into 2,2-dimethyl-2H-chromenes (13–24) in acidic media. 相似文献