全文获取类型
收费全文 | 955篇 |
免费 | 55篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 218篇 |
金属工艺 | 7篇 |
机械仪表 | 15篇 |
建筑科学 | 34篇 |
矿业工程 | 9篇 |
能源动力 | 16篇 |
轻工业 | 110篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 55篇 |
一般工业技术 | 147篇 |
冶金工业 | 194篇 |
原子能技术 | 4篇 |
自动化技术 | 188篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 25篇 |
2021年 | 47篇 |
2020年 | 26篇 |
2019年 | 16篇 |
2018年 | 26篇 |
2017年 | 27篇 |
2016年 | 28篇 |
2015年 | 28篇 |
2014年 | 31篇 |
2013年 | 64篇 |
2012年 | 45篇 |
2011年 | 67篇 |
2010年 | 42篇 |
2009年 | 47篇 |
2008年 | 48篇 |
2007年 | 52篇 |
2006年 | 38篇 |
2005年 | 43篇 |
2004年 | 33篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1976年 | 4篇 |
1972年 | 4篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1012条查询结果,搜索用时 15 毫秒
151.
Dana E. Wong Stephanie M. Andler Christina Lincoln Julie M. Goddard Joey N. Talbert 《Journal of Coatings Technology and Research》2017,14(2):489-495
Trace oxygen in packaged foods, beverages, and pharmaceuticals can promote a range of oxidative degradation reactions and support microbial growth, ultimately impacting product quality and shelf-life. Oxygen scavenging active packaging systems have therefore been explored to control headspace oxygen content. Herein, we report on a hydrophobic ion pairing method to render glucose oxidase hydrophobic, and thus soluble in organic solvents. Hydrophobic modified glucose oxidase was blended with ethylene vinyl acetate and cast on the interior of glass vials to demonstrate potential as a commercially translatable coating method for enzyme immobilization. The resulting oxygen scavenging polymer coatings were topographically uniform and presented 0.553 μg/cm2 enzyme at the coating interface. The coatings effectively reduced headspace oxygen by 2% in a closed-vial system filled 50 vol% with citrate buffer, pH 3.5. Less than 25% protein migrated from the coating over an 8-week leaching study, with no detectable protein leached in the first 4 weeks. Hydrophobic ion pairing of glucose oxidase enabled a facile, high-throughput enzyme immobilization technique without use of complicated, time-consuming surface modification chemistries and reagents. Such oxygen scavenging polymer coatings can support controlling headspace oxygen in packaged goods, and thus retaining stability of oxygen-sensitive components such as colors, flavors, and nutrients. 相似文献
152.
Concepcion JJ Dattelbaum DM Meyer TJ Rocha RC 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2008,366(1862):163-175
Detailed understanding of the transition between localized and delocalized behaviour in mixed valence compounds has been elusive as evidenced by many interpretations of the Creutz-Taube ion, [(NH3)5Ru(pz)Ru(NH3)5]5+. In a review in 2001, experimental protocols and a systematic model to probe this region were proposed and applied to examples in the literature. The model included: (i) multiple orbital interactions in ligand-bridged transition metal complexes, (ii) inclusion of spin-orbit coupling which, for dpi5-dpi6 complexes, leads to five low-energy bands, two from interconfigurational (dpi-->dpi) transitions at the dpi5 site and three from intervalence transfer transitions, (iii) differences in time scale between coupled vibrations and solvent modes which can result in solvent averaging with continued electronic asymmetry defining 'class II-III', an addition to the Robin-Day classification scheme, and (iv) delineation of coupled vibrations into barrier vibrations and 'spectator' vibrations. The latter provide direct insight into localization or delocalization and time scales for electron transfer. In this paper, the earlier model is applied to a series of mixed-valence molecules. 相似文献
153.
Dana Brown John Ferrario Randy Wolf Jing Li Jayendra Bhagat Mustapha Slamani 《Journal of Electronic Testing》2007,23(1):85-94
In this paper, testing of radio frequency (RF) devices with mixed-signal testers is discussed. General purpose automatic test
equipment (ATE) will be used. In this paper, a more universal test structure utilizing RF building blocks is proposed. A global
positioning system (GPS) device is used as an example to illustrate how to develop the RF test plan with this usage. The test
plan developed includes fast, cost-effective and dedicated circuitry.
相似文献
Jing LiEmail: |
154.
Electrical impedance tomography (EIT) is a badly posed inverse problem, but can be stabilized if one assumes that the conductivity is piecewise constant, with a relatively small number of distinct regions, and that the region boundaries are known, for example from prior anatomical imaging. With this assumption, we introduce a three-dimensional (3-D) boundary element method (BEM) model for the forward EIT map from injected currents to measured voltages, and 3-D inverse solutions for both BEM and the finite element method (FEM) which explicitly take into account the parameterization implied by the known boundary locations. We develop expressions for the Jacobians for both methods, since they are nonlinear, to more rapidly solve the inverse problem. We show simulation results in a torso geometry with the heart and lungs as inhomogeneities. In a simulation study, we could reconstruct the conductive values of some internal organs of a human torso with more than 92% accuracy even with inaccurate internal boundary locations, a randomized rather than constant conductivity profile (with the standard deviation of the Gaussian-distributed conductivities set to 20% of their mean values), signal to measurement noise of 50 dB, and with different meshes used for the forward and inverse problems. BEM and FEM perform similarly, leading to the conclusion that the choice between them should be based on secondary considerations such as computational efficiency or the need to model conductivity anisotropies 相似文献
155.
Hu Z Muls B Gence L Serban DA Hofkens J Melinte S Nysten B Demoustier-Champagne S Jonas AM 《Nano letters》2007,7(12):3639-3644
We demonstrate that arrays of nanowires of conjugated polymers can be easily produced by a simple embossing protocol, compatible with very large scale integration technology. The embossing process is shown to have the supplementary virtue to increase the internal degree of order of the nanowires, significantly enhancing their performance. This is applied to the fabrication of nanowire-based devices consisting of a liquid crystalline light-emitting polymer, of a liquid crystalline semiconducting polymer, and of an amorphous conducting polymer, illustrating the versatility and wide applicability of the method. 相似文献
156.
This research examined the effect of alcohol on intentional behavior using a process dissociation procedure to separate the influences of conscious controlled processes from those of unconscious automatic processes. In 2 identical experiments, 24 male social drinkers studied a list of words before they received either 0.56 g/kg alcohol, an alcohol placebo, or soda. Participants then performed a word stem completion test that provided estimates of controlled influences and of automatic influences on their responses. The results of the 2 experiments were consistent. Comparisons among the treatments showed that alcohol reduced conscious controlled processes and left automatic processes unchanged. The findings contribute to understanding how the drug may reduce cognitive control of intentional behavior and raise important questions concerning personal and environmental factors that might mediate these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
157.
In many instances, the architect∕engineer is responsible for the drafting of construction contracts. The importance of the drafter's clearly defining direct and indirect costs for contract items receiving cost reimbursement is reinforced by this survey of contractors. The survey asks contractors to classify a list of 44 items as their company would, with respect to project and home-office overhead and direct and indirect costs. The results of the survey indicate a lack of standard usage of these terms by industry. The survey also is used to investigate the manner in which contractors allocate home-office overhead to contracts. 相似文献
158.
Martina Culenova Andreas Nicodemou Zuzana Varchulova Novakova Michaela Debreova Veronika Smolinsk Sona Bernatova Dana Ivanisova Olga Novotna Jaromir Vasicek Ivan Varga Stanislav Ziaran Lubos Danisovic 《International journal of molecular sciences》2021,22(22)
Mesenchymal stem cells (MSCs) represent an attractive source within the field of tissue engineering. However, their harvesting often requires invasive medical procedures. Urine-derived stem cells (UDSCs) display similar properties to MSCs, and their obtention and further processing is non-invasive for the donors as well as low cost. Here, we offer a comprehensive analysis of their biological properties. The goal of this study was to analyze their morphology, stemness, differentiation potential and cytokine profile. We have successfully isolated UDSCs from 25 urine samples. First colonies emerged up to 9 days after the initial seeding. Cell doubling time was 45 ± 0.24 SD, and when seeded at the density of 100 cells/cm2, they formed 42 ± 6.5 SD colonies within 10 days. Morphological analyzes revealed that two different types of the cell populations have been present. The first type had a rice-grain shape and the second one was characterized by a polyhedral shape. In several cell cultures, dome-shaped cells were observed as well. All examined UDSCs expressed typical MSC-like surface markers, CD73, CD90 and CD105. Moreover, conditioned media from UDSCs were harvested, and cytokine profile has been evaluated showing a significantly higher secretory rate of IL-8, IL-6 and chemokines MCP-1 and GM-CSF. We have also successfully induced human UDSCs into chondrogenic, osteogenic and myogenic cell lineages. Our findings indicate that UDSCs might have immense potential in the regeneration of the damaged tissues. 相似文献
159.
Photoconductive optically driven deformable membrane for spatial light modulator applications utilizing GaAs substrates 总被引:1,自引:0,他引:1
Haji-Saeed B Kolluru R Pyburn D Leon R Sengupta SK Testorf M Goodhue W Khoury J Drehman A Woods CL Kierstead J 《Applied optics》2006,45(12):2615-2622
The fabrication and characterization of an optically addressable deformable mirror for a spatial light modulator is described. Device operation utilizes an electrostatically driven pixellated aluminized polymeric membrane mirror supported above an optically controlled photoconductive GaAs substrate. A 5 microm thick grid of patterned photoresist supports the 2 microm thick aluminized Mylar membrane. A conductive ZnO layer is placed on the back side of the GaAs wafer. A standard Michelson interferometer is used to measure mirror deformation data as a function of illumination, applied voltage, and frequency. A simplified analysis of device operation is also presented. 相似文献
160.
Lazzè MC Pizzala R Perucca P Cazzalini O Savio M Forti L Vannini V Bianchi L 《Molecular nutrition & food research》2006,50(1):44-51
Epidemiological and intervention studies correlate anthocyanin-rich beverages and a low incidence of coronary heart diseases. Since endothelin-1 (ET-1) and nitric oxide (NO) produced by endothelial NO synthase (eNOS) are vascular tension regulators secreted by endothelial cells, we studied the influence of two anthocyanidins, namely cyanidin (CY) and delphinidin (DP), on the regulation of ET-1 and eNOS in cultured human umbilical vein endothelial cells (HUVECs). Aglycon anthocyanidin forms, such as CY and DP, may be present in vivo after the first deglycosylation step occurring in the jejunum and in the liver. DP showed a major action compared to CY inducing a significant dose-dependent inhibitory effect on both protein and mRNA levels of ET-1. CY and DP both increased the protein level of eNOS, but DP showed the major effect raising eNOS protein in a dose-dependent manner. To correlate the vasoprotective effect of CY and DP with their antioxidant activity, we analysed also the antioxidant effect of anthocyanidins both in vitro and in HUVECs. In particular, we examined the effect of anthocyanidins on endothelial heme oxygenase-1 (HO-1), an inducible stress protein. In all tests, DP showed a higher antioxidant activity than CY. Finally, the antiproliferative effect induced by DP was detected in HUVECs. DP and CY differ in the number and position of hydroxyl groups in their structure; therefore, the greater biological activity by DP, compared with CY, seems to be due to the presence of the three hydroxyl groups on the B ring in the molecular structure of DP. 相似文献