全文获取类型
收费全文 | 5972篇 |
免费 | 130篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 52篇 |
综合类 | 59篇 |
化学工业 | 570篇 |
金属工艺 | 109篇 |
机械仪表 | 100篇 |
建筑科学 | 91篇 |
矿业工程 | 10篇 |
能源动力 | 146篇 |
轻工业 | 216篇 |
水利工程 | 15篇 |
石油天然气 | 17篇 |
武器工业 | 2篇 |
无线电 | 473篇 |
一般工业技术 | 717篇 |
冶金工业 | 3082篇 |
原子能技术 | 15篇 |
自动化技术 | 463篇 |
出版年
2023年 | 23篇 |
2022年 | 54篇 |
2021年 | 71篇 |
2020年 | 39篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 66篇 |
2015年 | 50篇 |
2014年 | 91篇 |
2013年 | 259篇 |
2012年 | 178篇 |
2011年 | 184篇 |
2010年 | 149篇 |
2009年 | 173篇 |
2008年 | 150篇 |
2007年 | 139篇 |
2006年 | 152篇 |
2005年 | 114篇 |
2004年 | 100篇 |
2003年 | 86篇 |
2002年 | 72篇 |
2001年 | 71篇 |
2000年 | 71篇 |
1999年 | 154篇 |
1998年 | 929篇 |
1997年 | 572篇 |
1996年 | 420篇 |
1995年 | 238篇 |
1994年 | 198篇 |
1993年 | 224篇 |
1992年 | 78篇 |
1991年 | 75篇 |
1990年 | 60篇 |
1989年 | 73篇 |
1988年 | 85篇 |
1987年 | 59篇 |
1986年 | 60篇 |
1985年 | 43篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 28篇 |
1981年 | 37篇 |
1980年 | 32篇 |
1979年 | 16篇 |
1978年 | 7篇 |
1977年 | 62篇 |
1976年 | 170篇 |
1975年 | 15篇 |
1972年 | 6篇 |
排序方式: 共有6137条查询结果,搜索用时 0 毫秒
81.
Lennart P.J. Teunissen Li-Chu Wang Shih-Nung Chou Chin-hsien Huang Gwo-Tsuen Jou Hein A.M. Daanen 《Applied ergonomics》2014
Firemen often suffer from heat strain. This study investigated two chest cooling systems for use under a firefighting suit. In nine male subjects, a vest with water soaked cooling pads and a vest with water perfused tubes were compared to a control condition. Subjects performed 30 min walking and 10 min recovery in hot conditions, while physiological and perceptual parameters were measured. No differences were observed in heart rate and rectal temperature, but scapular skin temperature and fluid loss were lower using the perfused vest. Thermal sensation was cooler for the perfused vest than for the other conditions, while the cool pad vest felt initially cooler than control. However, comfort and RPE scores were similar. We conclude that the cooling effect of both tested systems, mainly providing a (temporally) cooler thermal sensation, was limited and did not meet the expectations. 相似文献
82.
Thick films of superconducting oxides, YBa2Cu3O7-, were successfully made by conventional screen-printing technology on Al2O3, MgO, and ZrO2 substrates. Interdiffusion between the superconductive film and substrate was investigated using analytical electron microscopy. The results indicate that MgO and ZrO2 are superior to Al2O3 for substrate materials. 相似文献
83.
Kuo‐Chung Huang Yi‐Heng Chou Lang‐chin Lin Hoang Yan Lin Fu‐Hao Chen Ching‐Chiu Liao Yi‐Han Chen Kuen Lee Wan‐Hsuan Hsu 《Journal of the Society for Information Display》2013,21(6):263-270
The optimal viewing distance was proposed as a parameter for designing a parallax barrier 3D display. It can be designed based on simple geometric method and by considering the pitches of image display pixels and parallax barrier, or even including the aperture ratios of the image display pixels and parallax barrier. It can be analyzed by using ray tracing method. By considering the optical refraction index of the cover glass, the angular behavior of the system becomes more realistic; however, the geometric method is difficult to be used. We propose a revised method for estimating the view distance and angular behavior. In this paper, we have demonstrated a designated eye position (DEP) for each view and shown that multiple DEPs make a circular curve around the center of the display. We prove the new concept by comparing the optical ray tracing calculations and optical measurement. 相似文献
84.
85.
Yao-Jen Chang Li-Der Chou Frank Tsen-Yung Wang Shu-Fang Chen 《Personal and Ubiquitous Computing》2013,17(2):351-358
Difficulties in executing daily living tasks hamper the quality of life of many individuals with cognitive impairments who are otherwise physically mobile. With sufficient and appropriate support on the job, many people with developmental disabilities and cognitive impairments are capable of participating in the world of work to various levels. Kinect is used as assistive technology for individuals with cognitive impairments to achieve the goal of performing task steps independently. In a community-based rehabilitation program under the guidance of three job coaches, a task prompting system called Kinempt was designed to assist four participants involving pre-service food preparation training. The study assessed the effectiveness of Kinempt in terms of precision and recall. A follow-up comparative study then evaluated a baseline method and the system of least prompts against the Kinempt system. Results indicate that for participants with cognitive disabilities, acquisition of job skills may be facilitated by use of Kinempt in conjunction with operant conditioning strategies. Our findings suggest that the image recognition technology may be able to facilitate task prompts needed by people with cognitive impairments. Therefore, the system may be helpful for pre-service training while increasing independence in the process of community integration. 相似文献
86.
87.
In this paper, we propose a scheme to integrate independent component analysis (ICA) and neural networks for electrocardiogram (ECG) beat classification. The ICA is used to decompose ECG signals into weighted sum of basic components that are statistically mutual independent. The projections on these components, together with the RR interval, then constitute a feature vector for the following classifier. Two neural networks, including a probabilistic neural network (PNN) and a back-propagation neural network (BPNN), are employed as classifiers. ECG samples attributing to eight different beat types were sampled from the MIT-BIH arrhythmia database for experiments. The results show high classification accuracy of over 98% with either of the two classifiers. Between them, the PNN shows a slightly better performance than BPNN in terms of accuracy and robustness to the number of ICA-bases. The impressive results prove that the integration of independent component analysis and neural networks, especially PNN, is a promising scheme for the computer-aided diagnosis of heart diseases based on ECG. 相似文献
88.
The structure of silica gels derived from tetraethoxysilane (TEOS) with molar compositions of TEOSH2OHNO3=1100.4 and then aged in various solvents, was studied. The effect of various solvents having different physical properties on the gel structure, as well as the relationship between the solvent properties and the dried gel structure, were investigated. The density, surface area and pore-size distribution were measured. The results of the pore structure and SEM showed the aged gels to have a slit-shaped micropore, narrow pore-size distribution, and homogeneous microstructure. The density, surface area, pore size and pore volume of dried gels changed as the gels were subjected to ageing in various solvents. The surface area could be related to the polarity parameter of the ageing solvent. 相似文献
89.
Process simulation and fabrication of advanced multi-step three-dimensional braided preforms 总被引:3,自引:0,他引:3
The fundamentals of multi-step braiding for the fabrication of three-dimensional fibre preforms for composites have been studied. To facilitate the understanding of the complex multi-step braiding processes, a computer simulation algorithm has been developed. The simulation acts as a tool to allow the identification of individual yarn paths, number and location of yarn groups, and braid geometry. It was found that individual control of the rows and columns of yarn carriers on a Cartesian braiding bed allows for the fabrication of advanced multi-step braids; the micro-structural possibilities of three-dimensional braids are thus greatly extended. Some basic relationships of the braiding parameters have been identified. It has been concluded that the traditional four-step and two-step braidings are special cases of multi-step braidings. To verify the feasibility of the structures, experimental investigations have also been carried out. Innovative braid architectures have been designed and fabricated using a prototype multi-step braiding machine. 相似文献
90.
CM Otto MC Mickel JW Kennedy EL Alderman TM Bashore PC Block JA Brinker D Diver J Ferguson DR Holmes 《Canadian Metallurgical Quarterly》1994,89(2):642-650
BACKGROUND: To identify predictors of long-term outcome after balloon aortic valvuloplasty, we analyzed data on 674 adults (mean age, 78 +/- 9 years; 56% were women) undergoing this procedure at 24 clinical centers who had a mean initial increase in aortic valve area of 0.3 cm2. METHODS AND RESULTS: Baseline data included clinical, echocardiographic, and catheterization variables. Follow-up data included mortality, cause of death, rehospitalization, 6-month echocardiography, and functional status. Kaplan-Meier curves and log-rank tests were used to evaluate survival in subgroups. Multivariate Cox regression models were used to identify independent predictors of survival. Overall survival was 55% at 1 year, 35% at 2 years, and 23% at 3 years, with the majority of deaths (70%) classified as cardiac by an independent review committee. Rehospitalization was common (64%), although 61% of survivors at 2 years reported improved symptoms. Echocardiography at 6 months (n = 115) showed restenosis from the postprocedural valve area of 0.78 +/- 0.31 cm2 to 0.65 +/- 0.25 cm2 (P < .0001). With stepwise multivariate analysis, sequentially adding clinical, echocardiographic, and catheterization variables, the overall model identified independent predictors of survival as baseline functional status, baseline cardiac output, renal function, cachexia, female gender, left ventricular systolic function, and mitral regurgitation. Baseline and postprocedural variables were examined to identify which subgroup of patients has the best outcome after aortic valvuloplasty. A "lower-risk" subgroup (28% of the study population), defined by normal left ventricular systolic function and mild clinical functional limitation, had a 3-year survival of 36% compared with 17% in the remainder of the study group. CONCLUSIONS: Long-term survival after balloon aortic valvuloplasty is poor with 1- and 3-year survival rates of 55% and 23%, respectively. Although survivors report fewer symptoms, early restenosis and recurrent hospitalization are common. 相似文献