全文获取类型
收费全文 | 294篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 61篇 |
金属工艺 | 4篇 |
机械仪表 | 10篇 |
建筑科学 | 8篇 |
能源动力 | 17篇 |
轻工业 | 47篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 20篇 |
一般工业技术 | 41篇 |
冶金工业 | 46篇 |
自动化技术 | 61篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 20篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 3篇 |
1999年 | 4篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有318条查询结果,搜索用时 15 毫秒
1.
I Contreras R San-Millán A Agustín-Barrasa J Pontón G Quindós 《Canadian Metallurgical Quarterly》1996,136(1):17-20
A clinical study was carried out in an attempt to assess the efficacy of a newly designed electric toothbrush compared to a conventional manual toothbrush using the American Dental Association's protocol for evaluating toothbrushes. An Oral-B 35 manual toothbrush, which served as the control, was compared to the Plaq & White125 electric toothbrush. Examinations were performed by two calibrated examiners at baseline, day 15 and day 30. Examinations included the gingival index, plaque index and bleeding index. Mean indices were calculated and compared between the two brushes using the repeated measures multiple analysis of variance. No statistically significant differences between the mean indices on the three examination days were observed following the use of the manual or the electric toothbrushes. The results of this study demonstrate that the electric toothbrush was numerically more effective than the manual toothbrush in reducing supragingival plaque levels, either before or after brushing, at each examination date compared to baseline plaque values. However, this difference was not statistically significant. This and other findings concluded that the Plaq & White toothbrush is comparable to the control ADA-accepted toothbrush. 相似文献
2.
Farmers lung disease is a common form of hypersensitivity pneumonitis (HP) and is characterized by inflammation and granuloma formation in the lung. Interferon-gamma is important for the expression of granulomatous diseases caused by infectious agents; however, the role this mediator in regulating expression of the granulomatous response to inhaled antigen is not known. To evaluate this, we compared the response to inhaled antigen of mice that do not express the gene coding for interferon-gamma (GKO) with that of their normal littermates (WT). GKO and WT mice on a BALB/c background were exposed to 150 microg of the thermophilic bacteria Saccharopolyspora rectivirgula or saline alone, for three consecutive days a week, for 3 wk. After exposure to antigen, WT mice developed a marked granulomatous inflammation associated with an increase in lung weight and numbers of cells in bronchoalveolar lavage fluid (BAL). Although GKO mice also exhibited an increase in lung weight and numbers of cells in BAL fluid, they developed minimal inflammation and no granulomas after a similar exposure to antigen. To further evaluate if the lack of a response to antigen in GKO mice was due to lack of IFN-gamma, we replaced this mediator via intraperitoneal injections. When given replacement IFN-gamma, the GKO mice developed granulomatous inflammation in the lung. These studies show that IFN-gamma is essential for the expression of hypersensitivity pneumonitis. 相似文献
3.
In this paper, a fuzzy logic controller (FLC) based variable structure control (VSC) is presented. The main objective is to obtain an improved performance of highly non‐linear unstable systems. New functions for chattering reduction and error convergence without sacrificing invariant properties are proposed. The main feature of the proposed method is that the switching function is added as an additional fuzzy variable and will be introduced in the premise part of the fuzzy rules; together with the state variables. In this work, a tuning of the well known weighting parameters approach is proposed to optimize local and global approximation and modelling capability of the Takagi‐Sugeno (T‐S) fuzzy model to improve the choice of the performance index and minimize it. The main problem encountered is that the T‐S identification method can not be applied when the membership functions are overlapped by pairs. This in turn restricts the application of the T‐S method because this type of membership function has been widely used in control applications. The approach developed here can be considered as a generalized version of the T‐S method. An inverted pendulum mounted on a cart is chosen to evaluate the robustness, effectiveness, accuracy and remarkable performance of the proposed estimation approach in comparison with the original T‐S model. Simulation results indicate the potential, simplicity and generality of the estimation method and the robustness of the chattering reduction algorithm. In this paper, we prove that the proposed estimation algorithm converge the very fast, thereby making it very practical to use. The application of the proposed FLC‐VSC shows that both alleviation of chattering and robust performance are achieved. 相似文献
4.
Basil Mohammed Al-Hadithi Antonio Javier Barragán José Manuel Andújar Agustín Jiménez 《Applied Soft Computing》2013,13(12):4802-4812
In this paper, a fuzzy based Variable Structure Control (VSC) with guaranteed stability is presented. The main objective is to obtain an improved performance of highly non-linear unstable systems. The main contribution of this work is that, firstly, new functions for chattering reduction and error convergence without sacrificing invariant properties are proposed, which is considered the main drawback of the VSC control. Secondly, the global stability of the controlled system is guaranteed.The well known weighting parameters approach, is used in this paper to optimize local and global approximation and modeling capability of T-S fuzzy model.A one link robot is chosen as a nonlinear unstable system to evaluate the robustness, effectiveness and remarkable performance of optimization approach and the high accuracy obtained in approximating nonlinear systems in comparison with the original T-S model. Simulation results indicate the potential and generality of the algorithm. The application of the proposed FLC-VSC shows that both alleviation of chattering and robust performance are achieved with the proposed FLC-VSC controller. The effectiveness of the proposed controller is proven infront of disturbances and noise effects. 相似文献
5.
Electrostatic probes or Langmuir probes are the most common diagnostic tools in plasma discharges. The second derivative of the Langmuir probe I-V characteristic is proportional to the electron energy distribution function. Determining the second derivative accurately requires some method of noise suppression. We compare the Savitzky-Golay filter, the Gaussian filter, and polynomial fitting to the Blackman filter for digitally smoothing simulated and measured I-V characteristics. We find that the Blackman filter achieves the most smoothing with minimal distortion for noisy data. 相似文献
6.
7.
Agustí Segarra-Blasco 《Industry and innovation》2016,23(8):713-733
This article evaluates the propensity of firms to apply for R&D public grants, their capacity for obtaining subsides and how these relate to the firm age. This analysis is particularly relevant in understanding why young firms may be more or less successful in their application for public subsidies. Using data from an extensive database of 19,236 firms in Catalonia, we estimate a maximum likelihood probit model with sample selection. Our results show that firm age does not exert a significant direct impact on the application propensity in R&D public call, but younger firms tend to show a larger propensity to receive an R&D subsidy. They also show that firm age exerts a moderating role through different internal resources. They highlight the need to design R&D public policies that explicitly favour applications by young firms to help overcome their obstacles to innovation. 相似文献
8.
There have been many studies on the spatial configuration of cities, but few attempts to quantify the difference in building patterns between the old and new parts of cities. This may be partly attributable to lack of suitable study methods. This paper presents a new application of statistical methods for quantifying the geometric difference between different parts of a city using, as a case study, the old (historical) and new parts of the city of Yazd in Iran. We measured 341 edge lengths of 4 bazaars, 302 edge lengths of 5 mosques and tombs, and 239 edge lengths of 3 schools. We also measured 6,804 edge lengths and the areas of 1,243 well-preserved courtyard houses in the old part and 4,948 edge lengths and the areas of 1,237 houses in the new part of the city. In the old part, all edge-length and house-area frequency distributions, to a first approximation, follow power laws, indicating that there are many small and very few large buildings. By contrast, in the new part the edge-length and house-area frequency distributions follow bimodal (two-peak) distributions. The calculated entropies (measures of dispersion) of the house edge lengths and areas in the old part are much higher than of those in the new part and provide a clear, quantitative measure of the geometric differences between the built-up structures of old and the new parts of the cities. The power-law distributions in the old part indicate a gradual and continuous variation in sizes of edge lengths and house areas, whereas the bimodal distributions in the new part indicate abrupt (discontinuous) changes in the edge lengths and house areas. The entropy results imply that the size distributions of houses in the old part are more dispersed than those in the new part, indicating more interconnected structures in the old part of the city. The results also demonstrate quantitatively that there is a lack of coherence between the structures of old and new parts of city. 相似文献
9.
J. L. Varela Caselis E. Reyes Cervantes G. Landeta Cortés R. Agustín Serrano E. Rubio Rosas 《Materials Science-Poland》2014,32(3):436-441
We have prepared carboxymethyl cellulose fibers (CMC) by chemically modifying cotton cellulose with monochloroacetic acid and calcium chloride solution. This modification favored the growth of hydroxyapatite (HAP) on the surface of the CMC fibers in contact with simulated body fluid solutions (SBF). After soaking in SBF for periods of 7, 14 and 21 days, formation of HAP was observed. Analysis by scanning electron microscopy and X-ray diffraction showed that crystallinity, crystallite size, and growth of HAP increased with the soaking time. The amount of HAP deposited on CMC fibers increased greatly after 21 days of immersion in the SBF, while the substrate surface was totally covered with hemispherical aggregates with the size of the order of 2 microns. Elemental analysis showed the presence of calcium and phosphate, with calcium/phosphate atomic ratio of 1.54. Fourier transform infrared spectroscopy bands confirmed the presence of HAP. The results suggest that cotton modified by calcium treatment has a nucleating ability and can accelerate the nucleation of HAP crystals. 相似文献
10.
Jorge A. Marquez-Escalante Agustín Rascón-Chu Alma Campa-Mada Karla G. Martínez-Robinson Elizabeth Carvajal-Millan 《应用聚合物科学杂志》2020,137(5):48325
Feruloylated arabinoxylans (FAX) are gelling polysaccharides presenting antioxidant activity (AC) and potential application as delivery systems. The influence of carboxymethylation on the gelling capacity, rheological properties, and AC of FAX from wheat flour (FAX1) and maize distillers grains (FAX2) was analyzed. The degree of substitution of carboxymethyl groups was 0.27 and 1.77 for carboxymethylated FAX1 (CFAX1) and FAX2 (CFAX2), which presented a change in M n from 446 to 362 kDa and from 120 to 180 kDa, and a loss in FA content from 1.05 to traces and from 10.13 to 0.12, respectively, after carboxymethylation. G′ value at the end of rheological tests for FAX1 (71 Pa) and FAX2 (726 Pa) was higher than the corresponding G″ value. In contrast, G″ value for CFAX1 (0.35 Pa) and CFAX2 (0.03 Pa) was higher than the respective G′ value, indicating that they do no form gels. The AC increased in CFAX1 in relation to FAX1 from 4.49 to 8.30 mmol Trolox equivalent antioxidant capacity (TEAC) kg−1, respectively, while it decreased in CFAX2 with regard to FAX2 from 11.31 to 9.43 mmol TEAC kg−1, respectively. Carboxymethylation could be a path to design FAX derivatives offering alternative potential applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48325. 相似文献