全文获取类型
收费全文 | 514篇 |
免费 | 30篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 106篇 |
金属工艺 | 17篇 |
机械仪表 | 25篇 |
建筑科学 | 17篇 |
能源动力 | 50篇 |
轻工业 | 65篇 |
水利工程 | 3篇 |
石油天然气 | 7篇 |
无线电 | 32篇 |
一般工业技术 | 94篇 |
冶金工业 | 36篇 |
自动化技术 | 92篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 28篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 39篇 |
2011年 | 48篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 32篇 |
2007年 | 18篇 |
2006年 | 17篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有550条查询结果,搜索用时 15 毫秒
91.
Kohoutek J Bonakdar A Gelfand R Dey D Nia IH Fathipour V Memis OG Mohseni H 《Nano letters》2012,12(5):2537-2541
We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction. 相似文献
92.
93.
94.
Bogaerts Katleen; Van Eylen Lien; Li Wan; Bresseleers Johan; Van Diest Ilse; De Peuter Steven; Stans Linda; Decramer Marc; Van den Bergh Omer 《Canadian Metallurgical Quarterly》2010,119(1):226
The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing). Breathing behavior was continuously monitored, and dyspnea was rated every 10 s. The within-subject correlations between dyspnea on the one hand and end-tidal CO2 and minute ventilation on the other were used to index the degree to which perceived dyspnea was related to specific relevant respiratory changes. The results showed that perceived symptoms were less strongly related to relevant physiological parameters in MUS patients than in healthy persons, specifically when afferent physiological input was relatively weak. This suggests a stronger role for top-down psychological processes in the symptom perception of patients with MUS. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
Omer Yehezkeli Ran Tel‐Vered Dorit Michaeli Rachel Nechushtai Itamar Willner 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(17):2970-2978
Layered assemblies of photosystem I, PSI, and/or photosystem II, PSII, on ITO electrodes are constructed using a layer‐by‐layer deposition process, where poly N,N′‐dibenzyl‐4,4′‐bipyridinium (poly‐benzyl viologen, PBV2+) is used as an inter‐protein “glue”. While the layered assembly of PSI generates an anodic photocurrent only in the presence of a sacrificial electron donor system, such as dichlorophenol indophenol (DCPIP)/ascorbate, the PSII‐modified electrode leads, upon irradiation, to the formation of an anodic photocurrent (while evolving oxygen), in the absence of any sacrificial component. The photocurrent is generated by transferring the electrons from the PSII units to the PBV2+ redox polymer. The charge‐separated species allow, then, the injection of the electrons to the electrode, with the concomitant evolution of O2. A layered assembly, consisting of a PSI layer attached to a layer of PSII by the redox polymer PBV2+, leads to an anodic photocurrent that is 2‐fold higher, as compared to the anodic photocurrent generated by a PSII‐modified electrode. This observation is attributed to an enhanced charge separation in the two‐photosystem assembly. By the further nano‐engineering of the two photosystems on the electrode using two different redox polymers, vectorial electron transfer to the electrode is demonstrated, resulting in a ca. 6‐fold enhancement in the photocurrent. The reversed bi‐layer assembly, consisting of a PSII layer linked to a layer of PSI by the PBV2+ redox polymer, yields, upon irradiation, an inefficient cathodic current. This observation is attributed to a mixture of photoinduced electron transfer reactions of opposing effects on the photocurrent directions in the two‐photosystem assembly. 相似文献
96.
An integrated platinum nanoparticles (NPs)/glucose oxidase (GOx) composite film associated with a Au electrode is used to follow the biocatalytic activities of the enzyme. The film is assembled on a Au electrode by the electropolymerization of thioaniline-functionalized Pt NPs and thioaniline-modified GOx. The resulting enzyme/Pt NPs-functionalized electrode stimulates the O 2 oxidation of glucose to gluconic acid and H 2O 2. The modified electrode is then implemented to follow the activity of the enzyme by the electrochemical monitoring of the generated H 2O 2. The effect of the composition of the Pt NPs/GOx cross-linked nanostructures and the optimal conditions for the preparation of the electrodes are discussed. 相似文献
97.
Bagci U Yao J Wu A Caban J Palmore TN Suffredini AF Aras O Mollura DJ 《IEEE transactions on bio-medical engineering》2012,59(6):1620-1632
This study presents a novel computer-assisted detection (CAD) system for automatically detecting and precisely quantifying abnormal nodular branching opacities in chest computed tomography (CT), termed tree-in-bud (TIB) opacities by radiology literature. The developed CAD system in this study is based on 1) fast localization of candidate imaging patterns using local scale information of the images, and 2) M?bius invariant feature extraction method based on learned local shape and texture properties of TIB patterns. For fast localization of candidate imaging patterns, we use ball-scale filtering and, based on the observation of the pattern of interest, a suitable scale selection is used to retain only small size patterns. Once candidate abnormality patterns are identified, we extract proposed shape features from regions where at least one candidate pattern occupies. The comparative evaluation of the proposed method with commonly used CAD methods is presented with a dataset of 60 chest CTs (laboratory confirmed 39 viral bronchiolitis human parainfluenza CTs and 21 normal chest CTs). The quantitative results are presented as the area under the receiver operator characteristics curves and a computer score (volume affected by TIB) provided as an output of the CAD system. In addition, a visual grading scheme is applied to the patient data by three well-trained radiologists. Interobserver and observer-computer agreements are obtained by the relevant statistical methods over different lung zones. Experimental results demonstrate that the proposed CAD system can achieve high detection rates with an overall accuracy of 90.96%. Moreover, correlations of observer-observer (R(2)=0.8848, and observer-CAD agreements (R(2)=0.824, validate the feasibility of the use of the proposed CAD system in detecting and quantifying TIB patterns. 相似文献
98.
99.
Methylsulfonylmethane (or dimethyl sulfone), a naturally produced and vitally important organosulfur compound in living organisms, was irradiated with gamma rays, and the produced radicals were investigated using electron paramagnetic resonance spectroscopy at different temperatures. The structure and behavior of the radical changed when the temperatures varied. The hyperfine splitting of the CH(3) group was small, and the (33)S splitting was relatively high between 80 and -50 °C. When the temperature was between -50 and -160 °C, the (33)S splitting became small and the CH(3) splitting was higher. However, the group kept rotating; therefore, only the isotropic splitting values were measured, and the g-values were anisotropic. When the temperature decreased below -180 °C, the CH(3) group stopped rotating, and the hydrogen splitting values became nonequivalent due to an inhomogeneous electron distribution. The observed structures can be explained by referring to both the experimental and theoretically calculated values reported. 相似文献
100.
M. S. Mohy Eldin H. M. El‐Sherif E. A. Soliman A. A. Elzatahry A. M. Omer 《应用聚合物科学杂志》2011,122(1):469-479
A novel application, utilizing polyacrylamide‐g‐carboxymethyl cellulose (CMC‐g‐PAM) in concentrating dilute solutions of Bovine serum albumin (BSA), was investigated. The grafting reaction parameters were investigated and the hydrogel smartness was verified. FT‐IR proved that the grafting reaction occurred between the hydroxyl group located in anhydroglucose C2 position of CMC and the π‐bond of PAM and SEM confirmed a changed morphology to a fibrillar structure. The pH sensitivity was proved; as the grafted polymer attained its maximum swelling at pH 7.2 while the minimum swelling was observed under acidic conditions (pH 1‐3). The rate of water uptake in the grafted polymer hydrogel was higher than that of the homopolymer hydrogel and the swelling behaviors of both hydrogels obeyed second‐order kinetics. The tested hydrogel showed a high potency towards concentrating BSA solutions with a concentration factor of 1 to 4.5 times and recovery of 60–90%. The concentration factor increased linearly with increasing both the polymer concentration and the process time and decreased with the increase in the protein concentration. The grafted polymer had stable efficiency in the concentration process for 20 cycles. The obtained results have recommended the employment of the prepared CMC‐g‐PAM hydrogel in the down stream protein concentration process in the industrial scale. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. 相似文献