全文获取类型
收费全文 | 648篇 |
免费 | 53篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 145篇 |
金属工艺 | 16篇 |
机械仪表 | 23篇 |
建筑科学 | 15篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 145篇 |
水利工程 | 10篇 |
石油天然气 | 9篇 |
无线电 | 16篇 |
一般工业技术 | 138篇 |
冶金工业 | 69篇 |
原子能技术 | 3篇 |
自动化技术 | 83篇 |
出版年
2024年 | 4篇 |
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 40篇 |
2017年 | 43篇 |
2016年 | 42篇 |
2015年 | 20篇 |
2014年 | 28篇 |
2013年 | 65篇 |
2012年 | 37篇 |
2011年 | 35篇 |
2010年 | 42篇 |
2009年 | 33篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 20篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有702条查询结果,搜索用时 18 毫秒
91.
Alisson Rodrigo Souza Reis Sineire Maria Silva Araújo Paulo Ricardo Rodrigues Piovesan 《Holz als Roh- und Werkstoff》2018,76(6):1761-1763
The objective of this study was to anatomically characterize the fibers of nine species of Fabaceae lianas, to determine their potential in papermaking and to define which biometric parameters can be used to distinguish and identify individuals. The species presented average values of 76.81, 57.45, 42.55, and 1.81 for the felting index, wall fraction, coefficient of flexibility, and Runkel index, respectively. It is concluded that only M. ferox and M. madeirense can be recommended for papermaking. 相似文献
92.
93.
In this paper, a hybrid intelligent morphological approach is presented for stock market forecasting. It consists of a hybrid
intelligent model composed of a Modular Morphological Neural Network (MMNN) and a Modified Genetic Algorithm (MGA), which
searches for the minimum number of time lags for a correct time series representation, as well as by the initial weights,
architecture and number of modules of the MMNN. Each element of the MGA population is trained via Back Propagation (BP) algorithm
to further improve the parameters supplied by the MGA. Initially, the proposed method chooses the most tuned prediction model
for time series representation, then it performs a behavioral statistical test in the attempt to adjust time phase distortions
that appear in financial time series. An experimental analysis is conducted with the proposed method using four real world
time series and five well-known performance measurements, demonstrating consistent better performance of this kind of morphological
system. 相似文献
94.
C. Fernández-Lorenzo D. Araújo J. Martín R. Alcántara J. Navas M.P. Villar M.P. Alegre P.N. Volpe F. Omnès E. Bustarret 《Diamond and Related Materials》2010,19(7-9):904-907
A homoepitaxial boron-doped diamond single layer is investigated by means of Fourier transformed infrared spectroscopy (FTIR) and cathodoluminescence (CL). Both techniques are shown to be complementary. µ-FTIR mapping allows to determine the location of active boron while CL allows discernability between passivation and compensation. Hydrogen incorporation during chemical vapour deposition (CVD) growth is revealed to passivate boron acceptors. The obtained results highlight that plasma etching can induce a dissociation of B–H centres. 相似文献
95.
Active application of primer acid on acid‐treated enamel: Influence on the bond effectiveness of self‐etch adhesives systems 下载免费PDF全文
Cíntia Tereza Pimenta Araújo Lúcia Trazzi Prieto Daiane Cristianismo Costa Mariana Avalone Bosso Erick Kamiya Coppini Carlos Tadeu Santos Dias Luis Alexandre Maffei Sartini Paulillo 《Microscopy research and technique》2017,80(8):943-949
Aim: Evaluate the composite‐to‐enamel bond after passive or active application of self‐etching primer systems on polished or pre‐etched enamel with phosphoric acid. Materials and Methods: Two self‐etch adhesives systems (SEAS) were used: Clearfil SE Bond and Easy Bond. Third human molars were divided into 8 groups (N = 10). The crown of each tooth was sectioned into halves and the mesial/distal surfaces were used. The adhesives were actively or passively applied on enamel with or without prior phosphoric‐acid etching. Resin composite cylinders were built after adhesive application. After stored in relative humidity for 24 hr/37°C the specimens were subjected to microshear test in universal testing a machine at a crosshead speed of 0.5 mm/minute. The results were analyzed with three‐way ANOVA and the Tukey test. The enamel‐etching pattern was evaluated under SEM. Results: The 2‐step SEAS system presented significantly higher adhesive bond strength means (47.37 MPa) than the 1‐step (36.87 MPa). A poor enamel‐ etching pattern was observed in active mode showing irregular and short resin tags, however there was not compromised the bond strength. Conclusion: Active or passive application produced similar values of bond strength to enamel regardless of enamel pretreatment and type of SEAS. 相似文献
96.
Material removal rate, shear force and variance of shear force during copper polishing are studied as a function of pad conditioning scheme: 0% in situ conditioning (i.e., basically the equivalent of ex situ conditioning) and fractional in situ conditioning variants (i.e., conditioning during the first 25, 50, 75 or 100% of the total polish time). Spectral analysis of raw shear force data is employed to help elucidate the fundamental physical phenomena during copper chemical mechanical planarization. Fast Fourier transform is performed to convert the shear force data from time domain into frequency domain. The energy distribution of copper polishing is quantified which sheds light on the effect of fractional in situ pad conditioning. Variance of shear force and spectral analysis indicate that pad micro-texture evolution ceases after 50% fractional conditioning, thereby indicating that in situ conditioning time can be reduced during a given polishing process thus extending pad life. This study shows that a combination of unique spectral fingerprinting and analysis of force variance can be used to monitor the effect of pad conditioning in real time. This work also underscores the importance of real-time detection and non-destructive method to extend pad life and consumable usage during CMP by optimizing the pad conditioning time. 相似文献
97.
Comparative B‐mode and Doppler renal ultrasonography with histopathological findings in dogs positive for canine visceral leishmaniasis 下载免费PDF全文
Pollyana Irene Baltazar Laecio Da Silva Moura Gerson Tavares Pessoa Renan Paraguassu De Sá Rodrigues Marina Pinto Sanches Anaemilia Das Neves Diniz Francisco Das Chagas Araújo Sousa Porfírio Candanedo Guerra Willams Costa Neves Robson Fortes Giglio Jacyara De Jesus Rosa Pereira Alves Francisco De Assis Leite Souza Juliana Fortes Vilarinho Braga Flávio Ribeiro Alves 《Microscopy research and technique》2016,79(7):637-645
Morphological parameters and renal flow were assessed and measured in six clinically healthy dogs with negative serological and parasitological examinations for canine visceral leishmaniasis (CVL) and six dogs with CVL‐positive serological and parasitological tests and asymptomatic condition of the disease. Kidney length and diameter were measured and compared with the aorta/kidney ratio. Alterations in flow were measured using the flow velocity (cm/s) and resistance index (RI). Renal function was assessed by serum biochemical examination (urea, creatine, total proteins, albumin, and globulin) and urinalysis. CVL‐positive animals presented heterogeneous kidney echotexture, reduced vascular flow, hypoperfusion, lesser visualization of the arcuate arteries, high RI values (1.06 ± 0.28 for the right kidney and 1.10 ± 0.30 for the left kidney), reduced diastolic flow, and high systolic peak. They also presented positive creatine/RI correlation and between the renal artery vascular flow and kidney diameter. Histopathological analysis of CVL‐positive animals was compatible and confirmed hemodynamic changes observed by Doppler ultrasound. The findings in the present study showed that Doppler ultrasonography is a valid method to assess and detect alterations in flow in renal pathological processes with kidney vascular damage, as in the case of leishmaniasis, and can help in the diagnosis of animals with this infection. Microsc. Res. Tech. 79:637–645, 2016. © 2016 Wiley Periodicals, Inc. 相似文献
98.
Effect of vitamin A supplementation on diarrhoea and acute lower-respiratory-tract infections in young children in Brazil 总被引:1,自引:0,他引:1
ML Barreto LM Santos AM Assis MP Araújo GG Farenzena PA Santos RL Fiaccone 《Canadian Metallurgical Quarterly》1994,344(8917):228-231
A beneficial effect of periodic vitamin A supplementation on childhood mortality has been demonstrated, but the effect on morbidity is less clear. We investigated the effect of vitamin A supplementation on diarrhoea and acute lower-respiratory-tract infections (ALRI) in children from northeastern Brazil in a randomised, double-blind, placebo-controlled community trial. 1240 children aged 6-48 months were assigned vitamin A or placebo every 4 months for 1 year. They were followed up at home three times a week, and data about the occurrence and severity of diarrhoea and ALRI were collected. Any child with cough and respiratory rate above 40 breaths per min was visited by a paediatrician. The overall incidence of diarrhoea episodes was significantly lower in the vitamin-A-supplemented group than in the placebo group (18.42 vs 19.58 x 10(-3) child-days; rate ratio 0.94 [95% Cl 0.90-0.98]). The benefit of supplementation was greater as regards severe episodes of diarrhoea; the incidence was 20% lower in the vitamin A group than in the placebo group (rate ratio 0.80 [0.65-0.98]). With the standard definition of diarrhoea (> or = 3 liquid or semi-liquid stools in 24 h) the effect of vitamin A on mean daily prevalence did not reach significance, but as the definition of diarrhoea was made more stringent (increasing number of stools per day), a significant benefit became apparent, reaching for diarrhoea with 6 or more liquid or semi-liquid stools in 24 h a 23% lower prevalence. We found no effect of vitamin A supplementation on the incidence of ALRI. The reduction in severity of diarrhoea may be the most important factor in the lowering of mortality by vitamin A supplementation. 相似文献
99.
MC Bueno Jayme Gallani RC Rodrigues Colombo E de Araújo Cintra S Brunelli Rigacci 《Canadian Metallurgical Quarterly》1996,4(2):179-199
The overall purpose of this study was to explore nurses' feelings about the applicability and adequacy of a pilot model of nursing assessment (PMNA) developed for coronary care units (CCU) in order to obtain data that could help in establishing a definitive model. The evaluation, performed by 11 CCU nurses, showed that they considered the development and implementation of PMNA as valuable, and that its design was adequate for interviewing cardiac patients. These results will be employed in the elaboration of a definitive model of nursing assessment. 相似文献
100.
Certain biological differences between men and women are relevant to the problem of AAA, and are widely accepted. Women unequivocally have smaller aortas. The size difference correlates with a variety of anthropomorphic measurements, but is most strongly associated with body surface area. In women the compliance of the aorta decreases in linear fashion with age, whereas in men the decrease in compliance is exponential with age. Women appear to be underrepresented in AAA surgical series (typically 18% to 20% of operative cases) compared with autopsy studies (29% to 32%), ultrasound screening studies (19% to 25%), and mortality studies (34% of the 14,982 deaths due to AAA in the US in 1988). Several lines of evidence suggest that women with AAA are less likely than men to be referred for surgery, and that, when referred, they have higher mortality rates. The reasons for these differences are unclear. The very factors that allow increased longevity in women may have an adverse effect on the ability to tolerate a major surgical stress. Wenger et al have suggested that psychosocial and economic factors may affect women's decisions to seek care, or their choice of therapeutic options. Lack of knowledge among practitioners of gender-related aortic size differences and overreliance on simplistic clinical paradigms that dictate operations for 5-cm diameter aneurysms and watchful waiting for 4- to 5-cm AAAs may result in unintended bias in patient selection. It may be that a 5-cm diameter AAA in a woman with a predicted normal aortic size of 1.4 cm represents a more advanced stage of disease than a 5-cm diameter AAA in a man with a normal aortic diameter of 2.5 cm. More precise and detailed algorithms are needed to permit clinicians to tailor decisions to patients' size, sex, and risk factors. Development of such algorithms requires expansion of clinical and epidemiological studies to include enough women to make precise risk estimates. 相似文献