全文获取类型
收费全文 | 1960篇 |
免费 | 43篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 250篇 |
金属工艺 | 40篇 |
机械仪表 | 14篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 36篇 |
轻工业 | 91篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 145篇 |
一般工业技术 | 210篇 |
冶金工业 | 945篇 |
原子能技术 | 9篇 |
自动化技术 | 168篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 38篇 |
2020年 | 29篇 |
2019年 | 33篇 |
2018年 | 35篇 |
2017年 | 38篇 |
2016年 | 29篇 |
2015年 | 20篇 |
2014年 | 35篇 |
2013年 | 68篇 |
2012年 | 59篇 |
2011年 | 59篇 |
2010年 | 44篇 |
2009年 | 45篇 |
2008年 | 62篇 |
2007年 | 44篇 |
2006年 | 27篇 |
2005年 | 33篇 |
2004年 | 29篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 48篇 |
1998年 | 271篇 |
1997年 | 166篇 |
1996年 | 104篇 |
1995年 | 66篇 |
1994年 | 50篇 |
1993年 | 47篇 |
1992年 | 11篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1978年 | 16篇 |
1977年 | 30篇 |
1976年 | 59篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有2007条查询结果,搜索用时 15 毫秒
41.
Rami N. Khushaba Chelsea Wise Sarath Kodagoda Jordan Louviere Barbara E. Kahn Claudia Townsend 《Expert systems with applications》2013,40(9):3803-3812
Application of neuroscience methods to analyze and understand human behavior related to markets and marketing exchange has recently gained research attention. The basic aim is to guide design and presentation of products to optimize them to be as compatible as possible with consumer preferences. This paper investigates physiological decision processes while participants undertook a choice task designed to elicit preferences for a product. The task required participants to choose their preferred crackers described by shape (square, triangle, round), flavor (wheat, dark rye, plain) and topping (salt, poppy, no topping). The two main research objectives were (1) to observe and evaluate the cortical activity of the different brain regions and the interdependencies among the Electroencephalogram (EEG) signals from these regions; and (2) unlike most research in this area that has focused mainly on liking/disliking certain products, we provide a way to quantify the importance of different cracker features that contribute to the product design based on mutual information. We used the commercial Emotiv EPOC wireless EEG headset with 14 channels to collect EEG signals from participants. We also used a Tobii-Studio eye tracker system to relate the EEG data to the specific choice options (crackers). Subjects were shown 57 choice sets; each choice set described three choice options (crackers). The patterns of cortical activity were obtained in the five principal frequency bands, Delta (0–4 Hz), Theta (3–7 Hz), Alpha (8–12 Hz), Beta (13–30 Hz), and Gamma (30–40 Hz). There was a clear phase synchronization between the left and right frontal and occipital regions indicating interhemispheric communications during the chosen task for the 18 participants. Results also indicated that there was a clear and significant change (p < 0.01) in the EEG power spectral activities taking a place mainly in the frontal (delta, alpha and beta across F3, F4, FC5 and FC6), temporal (alpha, beta, gamma across T7), and occipital (theta, alpha, and beta across O1) regions when participants indicated their preferences for their preferred crackers. Additionally, our mutual information analysis indicated that the various cracker flavors and toppings of the crackers were more important factors affecting the buying decision than the shapes of the crackers. 相似文献
42.
43.
MgO-Y2O3 nanostructured composite powder (volume ratio of 50:50) was synthesized by a sol-gel combustion process which generated crystal sizes in the 10-20 nm range. The MgO-Y2O3 nanopowder was plasma sprayed using a conventional, DC arc plasma spray system. X-ray diffraction analysis shows that the as-sprayed MgO-Y2O3 coating is composed of cubic MgO and Y2O3 phases and has ~95% density. Microstructure characterization by SEM reveals that the as-sprayed coating has fine grain sizes of 100-300 nm as a result of rapid solidification. The hardness of the coating, 7.5 ± 0.6 GPa, is higher than that of coarse-grained, dense MgO, and Y2O3 ceramics. This approach demonstrates the potential of plasma spray processes for making thick, dense MgO-Y2O3 nanocomposite performs for applications as durable, infrared windows. 相似文献
44.
Jordan Schilbach 《国外电子测量技术》2014,(7)
正1引言移动数据流量的很大部分发生在室内。确保室内高密度用户的最佳网络质量显得特别重要。为了规划、实施和优化室内无线网络,首选必须对所有广泛使用的网络的无线信道质量进行可靠和全面评估。极其轻便和紧凑的路测扫描仪非常适合这一目标。甚至采用背包系统就能并行测量所有相关标准,因此极大缩短了测量时间。因为宽带市场上涌现出智能手机和平板电脑,移动宽带数据业务应用急速增加。仅2012年,全球移动数据 相似文献
45.
Oxidative stress has been implicated as a primary or secondary player to numerous diseases. A potential approach to control oxidative stress induced diseases is to deliver small antioxidant compounds to compromised sites at equivalent rates of reactive oxygen species (ROS) generation. This becomes a complicated task as antioxidant molecules typically have poor bioavailability and stability. Antioxidants synthesized into poly(beta-amino ester) (PBAE) crosslinked polymers have shown improved delivery by enhancing stability while allowing controlled release through hydrolysis. The tunable crosslinked networks show significant response to specific oxidizing environments, where free radicals can be present. Curcumin conjugated PBAE bulk films have proportional rates of accelerated degradation, thus faster release of curcumin, in a range of low concentrations of hydrogen peroxide (H2O2), where 2′2-azobis(2-amidinopropane) dihydrochloride has no substantial impact. This effect suggests the possibility to create a system that releases its therapeutic agent in direct relationship to the need through ROS signaling. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48647. 相似文献
46.
Anderson Ryan Terrell Jordan Schneider Judy Thompson Sean Gradl Paul 《Metallurgical and Materials Transactions B》2019,50(4):1921-1930
Metallurgical and Materials Transactions B - Various additive manufacturing processes are being evaluated to reduce the time and cost for fabrication of low volume, complex, and multifunctional... 相似文献
47.
Sharon Hausman-Cohen William LaValley Heather Way Emily Gutierrez Jordan Reeder 《International journal of molecular sciences》2022,23(4)
Molecular biology combined with genomics can be a powerful tool for developing potential intervention strategies for improving outcomes in children with autism spectrum disorders (ASD). Monogenic etiologies rarely cause autism. Instead, ASD is more frequently due to many polygenic contributing factors interacting with each other, combined with the epigenetic effects of diet, lifestyle, and environment. One limitation of genomics has been identifying ways of responding to each identified gene variant to translate the information to something clinically useful. This paper will illustrate how understanding the function of a gene and the effects of a reported variant on a molecular level can be used to develop actionable and targeted potential interventions for a gene variant or combinations of variants. For illustrative purposes, this communication highlights a specific genomic variant, SHANK3. The steps involved in developing molecularly genomically targeted actionable interventions will be demonstrated. Cases will be shared to support the efficacy of this strategy and to show how clinicians utilized these targeted interventions to improve ASD-related symptoms significantly. The presented approach demonstrates the utility of genomics as a part of clinical decision-making. 相似文献
48.
J. Grune K. Sempert M. Kuznetsov T. Jordan 《International Journal of Hydrogen Energy》2021,46(23):12487-12496
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames. 相似文献
49.
Dominik Rätz Kelly A. Jordan Gregory Perret Rakesh Chawla 《Annals of Nuclear Energy》2011,38(11):2319-2332
Two different types of perturbations of an SCWR-like fuel lattice have been investigated experimentally in the central test zone of the PROTEUS zero-power research reactor at the Paul Scherrer Institute in Switzerland. In each case, a campaign of high-resolution gamma-ray spectroscopy measurements was carried out on 34 fuel pins of the test lattice. In the first case, the test lattice was perturbed by inserting aluminum rods into the four central moderator regions, while in the second case, the perturbation was affected using steel absorber rods (instead of aluminum). The derived reaction rates are the capture rate in 238U (C8) and the total fission rate (Ftot), as also the reaction rate ratio C8/Ftot. Each of these has been mapped on the lattice and compared to calculated results from whole-reactor Monte Carlo simulations with MCNPX. Excellent agreement has been obtained, for both perturbed lattices, between the calculated and experimental distributions of C8, Ftot and C8/Ftot. Considering that control rods in an SCWR assembly are foreseen to be inserted into the central moderator regions, these results may be considered as generic validation of Monte Carlo simulations for the two different types of lattice perturbations which inserted control rods imply, viz. moderator displacement and strong neutron absorption.In a second step, calculated C8, Ftot and C8/Ftot distributions for the two perturbed lattices (as well as for the unperturbed lattice) have been compared, at assembly level, between MCNPX and the deterministic LWR lattice code CASMO-4E. In the case of the unperturbed lattice, as well as for the lattice with steel rods, the agreement between the codes is found to be within ~1% for all pins and each reaction rate. However, for the lattice with aluminum rods, i.e. the case with mainly just moderator displacement involved, CASMO overestimates the reaction rates in the vicinity of the perturbations by up to 2–3%, when employing the standard input options. The reason for this discrepancy has been found to be the leakage treatment, which uses the fundamental-mode buckling applied in a homogenized sense across the lattice. In this way, global leakage gradients get averaged out over the entire assembly. The optional input card BZ2 for CASMO resolves this problem, and the codes then agree within 1% even for the aluminum case. 相似文献