全文获取类型
收费全文 | 486篇 |
免费 | 33篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 101篇 |
金属工艺 | 26篇 |
机械仪表 | 8篇 |
建筑科学 | 2篇 |
能源动力 | 18篇 |
轻工业 | 4篇 |
石油天然气 | 1篇 |
无线电 | 69篇 |
一般工业技术 | 206篇 |
冶金工业 | 15篇 |
原子能技术 | 4篇 |
自动化技术 | 63篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 16篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 31篇 |
2013年 | 41篇 |
2012年 | 36篇 |
2011年 | 56篇 |
2010年 | 40篇 |
2009年 | 41篇 |
2008年 | 41篇 |
2007年 | 24篇 |
2006年 | 23篇 |
2005年 | 24篇 |
2004年 | 17篇 |
2003年 | 5篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有522条查询结果,搜索用时 15 毫秒
81.
Romanov DA Healy DM Brady JJ Levis RJ 《Journal of the Optical Society of America. A, Optics, image science, and vision》2008,25(5):1039-1050
We propose a new approach to the classical detection problem of discrimination of a true signal of interest from an interferent signal, which may be applied to the area of chemical sensing. We show that the detection performance, as quantified by the receiver operating curve (ROC), can be substantially improved when the signal is represented by a multicomponent data set that is actively manipulated by means of a shaped laser probe pulse. In this case, the signal sought (agent) and the interfering signal (interferent) are visualized by vectors in a multidimensional detection space. Separation of these vectors can be achieved by adaptive modification of a probing laser pulse to actively manipulate the Hamiltonian of the agent and interferent. We demonstrate one implementation of the concept of adaptive rotation of signal vectors to chemical agent detection by means of strong-field time-of-flight mass spectrometry. 相似文献
82.
Bose R McMillan JF Gao J Rickey KM Chen CJ Talapin DV Murray CB Wong CW 《Nano letters》2008,8(7):2006-2011
We present the first time-resolved cryogenic observations of Forster energy transfer in large, monodisperse lead sulfide quantum dots with ground-state transitions near 1.5 microm (0.8 eV), in environments from 160 K to room temperature. The observed temperature-dependent dipole-dipole transfer rate occurs in the range of (30-50 ns) (-1), measured with our confocal single-photon counting setup at 1.5 microm wavelengths. By temperature-tuning the dots, 94% efficiency of resonant energy transfer can be achieved for donor dots. The resonant transfer rates match well with proposed theoretical models. 相似文献
83.
Selective adsorption of semiconductor nanocrystals onto an organic self-organized pattern shows a time-dependent behavior. By studying the wetting behavior of delivered solvent (1-phenyloctane) on a lipid self-organized pattern and determining the adhesion energy between semiconductor nanocrystals and substrate, we obtain a correlation between dynamics and selectivity in adsorption of semiconductor nanocrystals onto the pattern by constructing a potential energy landscape. Two consecutive steps for selective adsorption of nanocrystals onto the self-organized pattern have been established: the first one is the molecule exchange of 1-phenyloctane and lipid molecules to form the adsorption sites for nanocrystals, and the second one is the adsorption of nanocrystals onto the adsorption sites due to the strong interaction between nanocrystals and substrate. 相似文献
84.
85.
Anton Germashev Viktor Logominov Dmitri Anpilogov Yuri Vnukov Vladimir Khristal 《先进制造进展(英文版)》2018,6(3):280-290
This paper presents an approach for determining the optimal cutting condition for milling thin-walled elements with complex shapes. The approach is based on the interaction between the thin-walled detail and its periodic excitation by tooth passing, taking into account the high intermittency of such a process. The influence of the excitation frequency on the amplitude of the detail oscillation during milling was determined by simulation and experiments. It was found that the analytical results agreed with experimental data. The position of the detail when the tooth starts to cut was evaluated through experiments. The influence of this parameter on the processing state is presented herein. The processing stability is investigated and compared with the proposed approach. Thereafter, spectral analyses are conducted to determine the contribution of the vibrating frequencies to the detail behavior during processing.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-018-0224-y.pdf 相似文献
86.
Field emitters in nanoscale are important in micro/nanoelectronic devices. Here, we report a large scale synthesis and effective field emission of field nanoemitters. The integrated nanostructures of ultrathin BN nanosheets aligned on Si3N4 nanowires are prepared through a two-stage process. Si3N4 nanowires were previously synthesized through heating Si powder at 1500 degrees C under a N2 atmosphere. Ultrathin BN nanosheets were then deposited on Si3N4 nanowires by heating a homemade B-N-O precursor under a N2/NH3 atmosphere. The as-prepared nanofilaments act as cold electron emitters displaying excellent field emission performance owing to the untrathin and sharp edges of the protruding BN nanosheets. 相似文献
87.
Biebersdorf A Dietmüller R Susha AS Rogach AL Poznyak SK Talapin DV Weller H Klar TA Feldmann J 《Nano letters》2006,6(7):1559-1563
Semiconductor nanocrystals (SCNCs) made of CdSe, CdTe, and InP are used to photosensitize needlelike C(60) crystals. The photocurrent is increased by up to 3 orders of magnitude as compared with C(60) crystals without SCNCs. The photocurrent spectrum can be tuned precisely by the SCNC size and material, rendering the SCNC-functionalized C(60) crystals an excellent material for spectrally tuneable photodetectors. We explain the increased photocurrent as a result of photoexcited electrons transferring from the SCNCs to the C(60) crystals and causing photoconductivity, while the complementary holes remain trapped in the SCNCs. 相似文献
88.
Mouradov D Craven A Forwood JK Flanagan JU García-Castellanos R Gomis-Rüth FX Hume DA Martin JL Kobe B Huber T 《Protein engineering, design & selection : PEDS》2006,19(1):9-16
We have determined the three-dimensional structure of the protein complex between latexin and carboxypeptidase A using a combination of chemical cross-linking, mass spectrometry and molecular docking. The locations of three intermolecular cross-links were identified using mass spectrometry and these constraints were used in combination with a speed-optimised docking algorithm allowing us to evaluate more than 3 x 10(11) possible conformations. While cross-links represent only limited structural constraints, the combination of only three experimental cross-links with very basic molecular docking was sufficient to determine the complex structure. The crystal structure of the complex between latexin and carboxypeptidase A4 determined recently allowed us to assess the success of this structure determination approach. Our structure was shown to be within 4 A r.m.s. deviation of Calpha atoms of the crystal structure. The study demonstrates that cross-linking in combination with mass spectrometry can lead to efficient and accurate structural modelling of protein complexes. 相似文献
89.
Assessment of cellular oxygen gradients with a panel of phosphorescent oxygen-sensitive probes 总被引:1,自引:0,他引:1
The supply of oxygen (O(2)) to respiring tissue, cells, and mitochondria regulates metabolism, gene expression, and cell fate. Depending on the cell type and mitochondrial function, O(2) gradients between extra- and intracellular compartments may vary and play important physiological roles such as the regulation of activity of prolyl hydroxylases and adaptive responses to hypoxia. Here we present a new methodology for the analysis of localized O(2) gradients in cultures of adherent cells, using three phosphorescent Pt-porphyrin based probes with different localization. One new O(2) probe targeted to the cell membrane was developed and used together with existing MitoXpress and Nano2 probes to monitor mean pericellular (PC), extracellular (EC), and intracellular (IC) O(2) concentrations, respectively. Mouse fibroblasts and neuronal PC12 cells cultured in standard microplates were stained with probes and measured on a commercial time-resolved fluorescence reader in phosphorescence lifetime mode. Respiring cells exposed to various levels of atmospheric O(2) showed differences in oxygenation of their IC, PC, and EC compartments. Experiments with different cell numbers and modulation of respiration activity demonstrated that these gradients are dynamic and regulated by the O(2) diffusion and consumption rate. The new method facilitates the assessment of such gradients. 相似文献
90.
In photonic force microscopes, the position detection with high temporal and spatial resolution is usually implemented by a quadrant position detector placed in the back focal plane of a condenser. An objective with high numerical aperture (NA) for the optical trap has also been used to focus a detection beam. In that case the displacement of the probe at a fixed position of the detector produces a unique and linear response only in a restricted region of the probe displacement, usually several hundred nanometers. There are specific experiments where the absolute position of the probe is a relevant measure together with the probe position relative the optical trap focus. In our scheme we introduce the detection beam into the condenser with low NA through a pinhole with tunable size. This combination permits us to create a wide detection spot and to achieve the linear range of several micrometers by the probe position detection without reducing the trapping force. 相似文献