全文获取类型
收费全文 | 709篇 |
免费 | 67篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 185篇 |
金属工艺 | 16篇 |
机械仪表 | 25篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 154篇 |
水利工程 | 12篇 |
石油天然气 | 9篇 |
无线电 | 20篇 |
一般工业技术 | 146篇 |
冶金工业 | 70篇 |
原子能技术 | 3篇 |
自动化技术 | 87篇 |
出版年
2024年 | 4篇 |
2023年 | 11篇 |
2022年 | 24篇 |
2021年 | 33篇 |
2020年 | 32篇 |
2019年 | 34篇 |
2018年 | 42篇 |
2017年 | 48篇 |
2016年 | 48篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 68篇 |
2012年 | 39篇 |
2011年 | 40篇 |
2010年 | 45篇 |
2009年 | 37篇 |
2008年 | 23篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 11篇 |
1995年 | 12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777条查询结果,搜索用时 15 毫秒
81.
J Ara E Mirapeix R Rodríguez J Pascual L Alvarez A Darnell 《Canadian Metallurgical Quarterly》1998,111(14):536-538
BACKGROUND: Analysis of usefulness of antineutrophil cytoplasmic antibodies (AN-CA) as a marker of clinical activity in small vessel vasculitis. PATIENTS AND METHODS: 33 patients, 10 patients with Wegener's granulomatosis (WG) and 23 with microscopic polyangiitis (MPA) and rapidly progressive glomerulonephritis type III (RPGN III). The clinic and serologic follow-up was accomplished every 3 months during an average of 19 (SD, 24) months (range 3-52 months. The serologic follow-up included the determination of ANCA by indirect immunofluorescence (IFI) and ELISA, as well as the serum level of C reactive protein (RCP). RESULTS: At the time of diagnosis all patients were ANCA positive by IFI and ELISA. The seroconversion of ANCA from positive to negative was produced in 30/33 patients (90%). Twenty-six out of these 30 patients (87%) achieved the seroconversion within the first 6 months. During the follow-up 4 patients had a major relapse, all with positive ANCA. In 2 patients, one of each group, seroconversion from negative to positive was not associated with clinical relapse of vasculitis. CONCLUSION: ANCA should be used in conjunction with other indices of disease activity in patients with small vessel vasculitis. 相似文献
82.
83.
G Caires A Drumond G Silva JJ Araújo A Cardoso A Teixeira JA Araújo I Mendon?a M Diniz 《Canadian Metallurgical Quarterly》1998,17(7-8):597-607
OBJECTIVE: The aim of this study was to analyse different ultrasound parameters for the assessment of isolated left ventricular diastolic dysfunction (LVDD) in patients with chronic renal failure (CRF) on periodic hemodialysis (HD), comparing pulsed wave Doppler with pulsed tissue Doppler. MATERIALS AND METHODS: Forty-seven patients with CRF on HD (61% were male; mean age was 51.0 +/- 16.5 years, mean HD time--3.7 +/- 3.8 years, 38% had hypertension, 17% had diabetes) were studied by echocardiography (bidimensional, M-Mode, flow pulsed Doppler and tissue Doppler imaging). All patients had symptoms of left heart failure-class II NYHA, were in sinus rhythm and had no symptoms of ischemic heart disease. The presence of abnormal LV regional contractility was the exclusion criteria. According to their mitral inflow profile Doppler characteristics, patients were included in two groups: Group A (E/A > 1; n = 21) and B (E/A < 1; n = 26). We compared: LV dimensions and function, left atrial (LA) dimension. Gaasch index, LV mass index. E and A wave velocities (in flow pulsatile Doppler and tissue Doppler). E/N ratio in tissue Doppler, isovolumetric relaxation time (IVRT) and deceleration time (DT). RESULTS: There were no significant differences in the prevalence of age > or = 65 years male sex, hypertension or diabetes between group A and B patients, and almost all patients were on hemodialytic treatment for more than one year (81% vs 85%: NS). LV hypertrophy was present in almost all group A and B patients (A--95% vs B--85.5%; NS). Group A, compared with group B, had a difference in the Gaasch index (2.45 +/- 0.3 vs 2.08 +/- 0.4; p < 0.05), E wave velocity in flow pulsatile Doppler and tissue Doppler (cm/sec) (110 +/- 27 vs 62 +/- 20; p < 0.001 and 41 +/- 15 vs 28.5 +/- 16; p < 0.05), E/A ratio in tissue Doppler (1.3 +/- 0.4 vs 0.8 +/- 0.3; p < 0.001). IVRT (msec) (80.7 +/- 15.2 vs 113.5 +/- 28.3; p < 0.001) and DT (msec) (189.7 +/- 24 vs 278.2 +/- 17.9; p < 0.001). According to the E'/A' ratio in tissue Doppler, group A patients were divided in another two groups: E'/A' > 1 (13/21--62%) and < 1 (8/21--38%) and a significantly longer IVRT (75.8 +/- 9.3 vs 100.9 +/- 3.2; p < 0.001) and DT (178 +/- 15 vs 240 +/- 20; p < 0.001) and a greater LA dimension (37.6 +/- 6.9 vs 44.6 +/- 6.9; p < 0.05) were found. CONCLUSIONS: Pulsed wave Doppler is the most useful non invasive method for assessment of global diastolic dysfunction. In our study, 17% of the patients had E/A < 1 only in the tissue Doppler study. These patients probably had a pseudonormal mitral pattern. 相似文献
84.
Vde P Teixeira MB Araújo MA dos Reis L dos Reis SA Silveira ML Rodrigues J Franquini Júnior 《Canadian Metallurgical Quarterly》1993,87(5):552-554
A non-parametric estimator of the AIDS survival time (after developing AIDS) is computed for the AIDS data set from the US Air Force (USAF). Survival times are unobservable. They are censored by the screening mechanism. The Armstrong Laboratory's Epidemiologic Research Division maintains data on over 954 active duty US Air Force (USAF) individuals who tested positive for human immunodeficiency virus (HIV) antibodies. Many have been clinically evaluated seven times since 1986. The HIV-positive individual is classified in seven stages of the disease complex as time progresses. Exact times of transition from one stage to the next are unknown. It is known that transition occurred between two consecutive evaluations. The aim of this study is to analyse distributions of the times that individuals spend in each stage of the HIV disease complex. We will discuss methods used to obtain non-parametric estimators of the distribution of times that individuals spend in stage 6. Finally, it is hoped to model the median time spent in each stage of the disease. This, along with incidence and separation data, will allow the prediction of the impact of HIV disease on USAF individuals and medical care systems. 相似文献
85.
We present two cases of community acquired pneumonia (extra-hospital) of severe onset, secondary to Chlamydia psittaci of avian origin. Each patient have bought a parakeet in the same pet-shop, and took care of them personally. Both developed a respiratory insufficiency, one of them needing mechanical ventilation. Out of nine relatives to whom serological determinations were performed, there was evidence of infection in two of them, but only one referred an auto-limited febrile syndrome during that period of time. Psittacosis incidence is discussed as origin of community acquired pneumonias, as well as its epidemiology, diagnosis and treatment. 相似文献
86.
E.?M.?Araú?JoEmail author E.?HageJr. A.?J.?F.?Carvalho 《Journal of Materials Science》2005,40(16):4239-4246
Nylon6 is an attractive polymer for engineering applications because it has reactive functionality through amine and carboxyl end groups that are capable of reacting. For this reason, it has been used a lot in polymeric blends. Blends of nylon6/ABS (acrylonitrile-butadiene-styrene) were produced using glycidyl methacrylate-methyl methacrylate (GMA-MMA) copolymers as compatibilizer. The binary blends were immiscible and exhibited poor mechanical properties that stemmed from the unfavorable interactions among their molecular segments. This produced an unstable coarse phase morphology and weak interfaces between the phases in the solid state. The presence of the copolymer in the blends clearly led to a more efficient dispersion of the ABS phase and consequently optimized Izod impact properties. However, the compatibilized blend showed poor toughness at room temperature and failed in a brittle manner at subambient temperatures. 相似文献
87.
Traina C Traina AJ Araújo MR Bueno JM Chino FJ Razente H Azevedo-Marques PM 《Computer methods and programs in biomedicine》2005,80(Z1):S71-S83
This paper presents a new Picture Archiving and Communication System (PACS), called cbPACS, which has content-based image retrieval capabilities. The cbPACS answers range and k-nearest- neighbor similarity queries, employing a relational database manager extended to support images. The images are compared through their features, which are extracted by an image-processing module and stored in the extended relational database. The database extensions were developed aiming at efficiently answering similarity queries by taking advantage of specialized indexing methods. The main concept supporting the extensions is the definition, inside the relational manager, of distance functions based on features extracted from the images. An extension to the SQL language enables the construction of an interpreter that intercepts the extended commands and translates them to standard SQL, allowing any relational database server to be used. By now, the system implemented works on features based on color distribution of the images through normalized histograms as well as metric histograms. Metric histograms are invariant regarding scale, translation and rotation of images and also to brightness transformations. The cbPACS is prepared to integrate new image features, based on texture and shape of the main objects in the image. 相似文献
88.
89.
Camilloto GP Pires AC Soares Nde F Araújo EA Andrade NJ Ferreira SO 《Journal of food science》2010,75(8):E557-E564
ABSTRACT: Antimicrobial polyethylene and cellulose based films incorporated with triclosan were studied. The antimicrobial efficacy, the hydrophobicity, microscopic and the mechanical characteristics of the films, as well free energy of adhesion between bacteria and antimicrobial films were evaluated. It was observed that both polyethylene and cellulose based films incorporated with the antimicrobial were homogeneous. Furthermore, the addition of triclosan did not affect mechanical characteristics of the films (P > 0.05). However, triclosan incorporated into polyethylene films reduced its hydrophobicity while antimicrobial cellulose based films became more hydrophobic. The adhesion was thermodynamically favorable between tested bacteria and polyethylene films. On the other hand, the adhesion to triclosan cellulose based film was thermodynamically unfavorable to Staphylococcus aureus and Escherichia coli and favorable to Listeria innocua and Pseudomonas aeruginosa. Polyethylene and cellulose based films showed inhibitory effect against S. aureus and E. coli, being the inhibition halo higher for polyethylene films. This study improves the knowledge about antimicrobial films. 相似文献
90.
Arantxa Alonso Santiago García‐Martínez Laura Vázquez‐Araújo Juan J Ruiz Ángel A Carbonell‐Barrachina 《Journal of the science of food and agriculture》2010,90(6):1056-1062
BACKGROUND: Nowadays, organoleptic quality is the primary objective for almost all tomato breeding programmes. In this study, post‐harvest behaviour of a breeding line with genetic resistance to important viruses (tomato mosaic virus, tomato spotted wilt virus and tomato yellow leaf curl virus) has been compared with the original traditional landrace (Muchamiel). The breeding line has been obtained by backcrossing, introgressing three resistance genes but aiming to keep the quality characteristics of the traditional variety. Tomatoes were picked at random and stored at 10 °C for 13 days. Quality analyses were made in both tomato samples: weight loss, colour, respiration rate, ethylene production, maturity index, instrumental hardness and sensory evaluation with trained panel. RESULTS: Fruits of the breeding line were characterized by higher hardness even with a higher maturity index. Results of sensory tests were in agreement with instrumental measurements. Organoleptic quality of Muchamiel virus‐resistant tomatoes was at least as high as that of traditional tomatoes, reaching the best scores in odour and aroma at the 13th storage day. CONCLUSION: Although a long time has been required to develop the breeding line, results indicate that organoleptic fruit quality has been recovered through backcrossing, confirming the success of the breeding programme. Copyright © 2010 Society of Chemical Industry 相似文献