全文获取类型
收费全文 | 4034篇 |
免费 | 298篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 93篇 |
综合类 | 3篇 |
化学工业 | 1044篇 |
金属工艺 | 98篇 |
机械仪表 | 134篇 |
建筑科学 | 118篇 |
矿业工程 | 7篇 |
能源动力 | 165篇 |
轻工业 | 906篇 |
水利工程 | 24篇 |
石油天然气 | 30篇 |
无线电 | 174篇 |
一般工业技术 | 574篇 |
冶金工业 | 450篇 |
原子能技术 | 29篇 |
自动化技术 | 496篇 |
出版年
2024年 | 22篇 |
2023年 | 43篇 |
2022年 | 148篇 |
2021年 | 189篇 |
2020年 | 131篇 |
2019年 | 168篇 |
2018年 | 190篇 |
2017年 | 186篇 |
2016年 | 184篇 |
2015年 | 117篇 |
2014年 | 168篇 |
2013年 | 332篇 |
2012年 | 276篇 |
2011年 | 262篇 |
2010年 | 216篇 |
2009年 | 245篇 |
2008年 | 173篇 |
2007年 | 144篇 |
2006年 | 113篇 |
2005年 | 80篇 |
2004年 | 67篇 |
2003年 | 61篇 |
2002年 | 64篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 55篇 |
1998年 | 135篇 |
1997年 | 88篇 |
1996年 | 88篇 |
1995年 | 52篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 20篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 25篇 |
1975年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有4345条查询结果,搜索用时 0 毫秒
21.
JM de Oliveira 《Canadian Metallurgical Quarterly》1998,17(12):967-973
At present, the treatment for acute myocardial infarction is revascularization during the critical initial period of six hours after the beginning of coronary occlusion. Despite the fact that surgery performed within this time period presents a hospital of mortality around 2%, and with excellent results in the long term, it is seldom used due to logistic limitations and capabilities of hospital infrastructures, high costs and the possibility of the surgical team initiating surgery inside the useful time period. Surgery is thus limited to the patients with suitable anatomy, who are not candidates or had failure of thrombolytic/angioplasty therapy and are in the six-hour period after initiation of symptoms. Surgery performed at a later stage has good results if performed in a non emergency situation, specially after the first 72 hours. Surgery continues to be the only treatment for the mechanical complications of infarction, and good results have recently been shown in ventricular septal ruptures, with hospital mortality of 14%, due to the use of an endoventricular patch in patients operated early, before the consequences of low cardiac output develop at systemic level. In the surgical treatment of mitral regurgitation, the tendency has been to use repair techniques whenever possible, but still with hospital mortality up to 15%. The recent advances of the techniques and tactics of myocardial preservation during surgery have made a very significant contribution to the better results we see today. 相似文献
22.
D Ayres-de-Campos JL Silva-Carvalho C Oliveira I Martins-da-Silva J Silva-Carvalho L Pereira-Leite 《Canadian Metallurgical Quarterly》1995,10(8):2010-2016
In this study, we evaluated the reproducibility of analysis of basal body temperature graphs under optimized conditions for agreement. A total of 160 recordings were selected from spontaneous cycles of infertile women and analysed by three experienced clinicians using uniform criteria. Agreement at the various stages of analysis was assessed by the 'proportions of agreement' with 95% confidence intervals. Agreement in identification of the thermal nadir was clearly superior to that reported in previous publications. Reproducibility of 'ovulatory' graph features (i.e. biphasic graphs and adequate thermal shifts) was excellent. Agreement in classification of monophasic graphs and inadequate thermal shifts, although lower, was still good. Thus, with experienced observers and uniform criteria, a good agreement can be achieved in analysis of the most important parameters of the basal body temperature graph. We believe that an effort should be made to generalize the use of uniform analysis criteria, because only then can results from different institutions be compared and the remaining clinical evaluation of the method be performed. 相似文献
23.
J. De Caigny J. F. Camino R. C. L. F. Oliveira P. L. D. Peres J. Swevers 《国际强度与非线性控制杂志
》2012,22(5):535-558
》2012,22(5):535-558
This paper presents synthesis conditions for the design of gain‐scheduled dynamic output feedback controllers for discrete‐time linear parameter‐varying systems. The state‐space matrix representation of the plant and of the controller can have a homogeneous polynomial dependency of arbitrary degree on the scheduling parameter. As an immediate extension, conditions for the synthesis of a multiobjective ??∞ and ??2 gain‐scheduled dynamic feedback controller are also provided. The scheduling parameters vary inside a polytope and are assumed to be a priori unknown, but measured in real‐time. If bounds on the rate of parameter variation are known, they can be taken into account, providing less conservative results. The geometric properties of the uncertainty domain are exploited to derive finite sets of linear matrix inequalities based on the existence of a homogeneous polynomially parameter‐dependent Lyapunov function. An application of the control design to a realistic engineering problem illustrates the benefits of the proposed approach. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
24.
Dai JD Winkel V Oliveira JB Jen CK 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1992,39(6):722-729
An approximate analysis of the weakly guiding cladded acoustic fiber consisting of a core and infinite thick cladding both with hexagonal crystal symmetry is presented. The crystalline Z axis is parallel to the fiber axis. Weak guidance conditions require that the stiffness constants of the core are slightly less than those of the cladding, and the density of the core and cladding are almost the same. Approximate dispersion and cutoff equations are derived for all pure guided modes. Dispersion curves of several lower-order guided torsional, radial-axial and flexural modes are evaluated using both exact and approximate formulas and they are in good agreement. A simple approximate dispersion equation for leaky (longitudinal-type) modes is also obtained. 相似文献
25.
M A Rossi S Zucoloto J E Dutra de Oliveira P F Becker J S Oliveira 《Archivos latinoamericanos de nutrición》1978,28(1):29-40
A study of the effect of long-term alcohol consumption on the liver of well-nourished rats is described. Rats fed for 16 weeks on a semipurified diet supplemented with high levels of vitamins and lipotropic factors and alcohol corresponding to 35% of the total caloric intake developed marked fatty changes of the liver. Mild fatty changes were observed in pair-fed controls receiving as isoenergetic equivalent of sucrose instead of alcohol. Intracellular hyaline bodies, corresponding ultrastructurally to giant mitochondria were abundantly found in the hepatocytes of alcoholic rats, while in the controls they were not seen. Te findings in this investigation are postulated to provide further evidence that the long-term intake of alcohol exerts a direct causative role in the pathogenesis of liver damage. 相似文献
26.
Evandro Eduardo Broday Antonio Augusto de Paula XavierReginaldo de Oliveira 《International Journal of Industrial Ergonomics》2014
The incorrect determination of metabolic rate can be linked to discrepancies between the model of the PMV (Predicted Mean Vote) and real thermal sensation collected in field studies. Aiming to improve the correlation of the PMV model and the real thermal sensation, this work established new values for the metabolic rate: one way being called “calculated” using Newton's Method and the other called "measured" using a metabolic analyzer. Welder's activities were evaluated, through the measurements of environmental and personal variables. New values of metabolic rate were determined for this activity. The values found for the calculated form and the measured one were, respectively, 178.63 and 145.46 W/m2, different from the range provided by the table of ISO 8996 (2004) for this activity (75–125 W/m2). In order to verify which of the values of the metabolic rate was closer to the real thermal sensation of PMV, a linear regression was made between the PMV and the real thermal sensation in three ways: S × PMVtabulated (R2 = 0.1749), S × PMVcalculated (R ² = 0.7481) and S × PMVmeasured (R2 = 0.7854). It was found that the values measured by the instrument gave a higher coefficient of determination which was chosen for the correction of the table. The correction of the table provides a value of Mpredicted, that is a value of metabolic rate that corrects the values provided by the tables of ISO 8996 (2004), by means of a correction coefficient. For the welder's activities in a metal-mechanics industry, tabulated values can be multiplied by the correction coefficient 1.4648 in order to minimize inaccuracies. The PMVpredicted, obtained through the Mpredicted, when related to the actual thermal sensation, provides a coefficient of determination of 0.7511, thereby improving the model of the PMV. 相似文献
27.
Clinical practice guidelines in paper format are still the preferred form of delivery of medical knowledge and recommendations to healthcare professionals. Their current support and development process have well identified limitations to which the healthcare community has been continuously searching solutions. Artificial intelligence may create the conditions and provide the tools to address many, if not all, of these limitations.. This paper presents a comprehensive and up to date review of computer-interpretable guideline approaches, namely Arden Syntax, GLIF, PROforma, Asbru, GLARE and SAGE. It also provides an assessment of how well these approaches respond to the challenges posed by paper-based guidelines and addresses topics of Artificial intelligence that could provide a solution to the shortcomings of clinical guidelines. Among the topics addressed by this paper are expert systems, case-based reasoning, medical ontologies and reasoning under uncertainty, with a special focus on methodologies for assessing quality of information when managing incomplete information. Finally, an analysis is made of the fundamental requirements of a guideline model and the importance that standard terminologies and models for clinical data have in the semantic and syntactic interoperability between a guideline execution engine and the software tools used in clinical settings. It is also proposed a line of research that includes the development of an ontology for clinical practice guidelines and a decision model for a guideline-based expert system that manages non-compliance with clinical guidelines and uncertainty. 相似文献
28.
Massa Lucas Barbosa Adriano Oliveira Krerley Vieira Thales 《Multimedia Tools and Applications》2021,80(4):5517-5537
Multimedia Tools and Applications - Measuring and analyzing the flow of customers in retail stores is essential for a retailer to better comprehend customers’ behavior and support... 相似文献
29.
Inspired by the relational algebra of data processing, this paper addresses the foundations of data analytical processing from a linear algebra perspective. The paper investigates, in particular, how aggregation operations such as cross tabulations and data cubes essential to quantitative analysis of data can be expressed solely in terms of matrix multiplication, transposition and the Khatri–Rao variant of the Kronecker product. The approach offers a basis for deriving an algebraic theory of data consolidation, handling the quantitative as well as qualitative sides of data science in a natural, elegant and typed way. It also shows potential for parallel analytical processing, as the parallelization theory of such matrix operations is well acknowledged. 相似文献
30.