全文获取类型
收费全文 | 191篇 |
免费 | 14篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 49篇 |
金属工艺 | 4篇 |
机械仪表 | 8篇 |
建筑科学 | 5篇 |
能源动力 | 2篇 |
轻工业 | 27篇 |
水利工程 | 1篇 |
无线电 | 18篇 |
一般工业技术 | 19篇 |
冶金工业 | 43篇 |
自动化技术 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 15 毫秒
61.
Elaine Aparecida Regiani de Campos Regina Negri Pagani Luis Mauricio Resende Joseane Pontes 《Scientometrics》2018,116(2):815-842
Methodi Ordinatio is a methodology used to accomplish systematic literature reviews, to build bibliographical portfolios, and to map the state of the art of a research theme. It is composed of nine phases. The 7th phase, named InOrdinatio, applies an equation that orders the papers according to its scientific relevance. The equation applies the alpha (α) element, which can vary from 0 to 10 depending on the research need of currentness and according to the researcher’s perception for its variation. Therefore, the aim of this paper is to test and analyse the variations of the alpha (α) values in the equation InOrdinatio and its influence in the qualification of the items that composes a portfolio. In order to reach this purpose, a practical application was performed and a bibliographic portfolio on the theme Horizontal Business Networks and Trust was built. Using the data from the bibliographic portfolio, the alpha values from 0 to 10 were applied and their influence on the final qualification of the articles was analysed. As a complementary objective, the areas where the methodology was successfully applied until now are also identified. The results show that the methodology is coherent, reproducible and useful to sort the most relevant articles in accordance with what is internationally recognized as valid scientific criteria: the impact factor, year of publication, and number of citations. 相似文献
62.
A Marcos Dolado J Sánchez Portocarrero R Jiménez Madridejo JC Pontes Navarro D García Urra 《Canadian Metallurgical Quarterly》1994,9(2):72-75
Boutonneuse fever (BF) is usually considered to be a benign rickettsiosis. However, severe presentations, resembling Rocky Mountain spotted fever, have been reported. There are few neurological complications, except in serious forms of the disease. We present a case of meningoencephalitis in a male adult suffering from BF, and we review the clinical, etiopathogenic and diagnostic aspects among the cases previously reported. We conclude that BF encephalitis would have the following characteristics: a) they mostly affect elderly males; b) they cause altered consciousness level, headaches and low rate of meningeal signs; c) absence of "tache noir"; d) cerebrospinal fluid with slight pleocytosis and/or increased level of proteins, and normal glucose values; e) computerized tomography without significative changes, and f) high rate of morbidity and mortality. We emphasize that we should consider BF in the differential diagnosis of our environmental encephalitis. 相似文献
63.
Ivaldo D. S. Pontes Fo. Lavinia A. Borges Nestor Zouain Francisco R. Lopes 《International journal for numerical methods in engineering》1997,40(21):4011-4032
The paper presents an algorithm for limit analysis with mixed approach by finite elements with application to geotechnical problems. The emphasis is on a special technique to deal with the singularity at the apex of a cone-shaped yield surface. The approach is based on the direct application of the sub-differential concept to the flow law and is essentially different from the Lagrange multipliers technique. The proposed algorithm does not require the regularization usually adopted for the singularities at the boundary of the plastic admissible stress region that occur in soil models. The case of a Drucker–Prager model is particularly considered, as well as the Mohr–Coulomb model in plane strain conditions. The algorithm is applied to a footing and a shallow tunnel. © 1997 John Wiley & Sons, Ltd. 相似文献
64.
Valeria Pettarin Gastón Viau Laura Fasce Julio C. Viana Antonio J. Pontes Patricia M. Frontini Antonio S. Pouzada 《Polymer Engineering and Science》2013,53(4):724-733
Polypopylene/nanoclay three‐dimensional parts were produced without intermediate steps by direct injection molding to explore the influence of flow features and nanoclay incorporation in their impact performance. The nanocomposite was obtained by direct compounding of commercial PP with nanoclay masterbatch. The as‐molded morphology was analyzed by X‐ray and TEM analyses in terms of skin‐core structure and nanoclay particle dispersion. The nanoclay particles induced the reduction of β‐form spherulites, a known toughener. The impact behavior was assessed in tensile and biaxial modes. The PP nanocomposite molding toughness was practically unaffected by the processing melt temperature and flow rate. Conversely the nanoclay presence is influent in the impact performance. Under biaxial stress impact, the regions close to weld lines are tougher than the bulk and the fracture develops with main crack paths along the flow direction and the weld line. Cracking along the weld line results from less macromolecular interpenetration and chain entanglement, and unfavorable nanoparticle orientation. It seems that a failure mechanism which involves nanoclay delamination and multiple matrix crazing explains the toughening of PP in the directions where the nanoparticle orientation with respect to loading is adequate. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers 相似文献
65.
Claudia A. Zacharias Gina B. Pontes Marcelo G. Lorenzo Gabriel Manrique 《Journal of chemical ecology》2010,36(4):449-451
Several triatomine bug species utilize chemical cues for sexual communication. We tested whether female or male Rhodnius prolixus, a vector of Chagas disease, produce volatile chemicals that elicit flight responses from conspecifics, and then isolated
the source of the chemical. Males confronted with an airstream containing female odors showed a significantly greater take-off
frequency compared to a blank airstream or an airstream with male odors. In contrast, females exhibited similar take-off frequencies
to male or female odor as to a clean airstream. Occlusion of female metasternal glands with paraffin wax resulted in a significant
decrease in male take-off frequency compared to that of intact females. Additionally, excised female metasternal glands elicited
a similar take-off frequency from males as did intact females, both significantly greater than the take-off frequency to clean
air. These results show that R. prolixus females release a pheromone from their metasternal glands that causes upwind flight in conspecific males. 相似文献
66.
José Pedro Pontes 《The Annals of Regional Science》2007,41(4):897-909
This paper models the decision of vertically linked firms to build either partitioned or connected networks of supply of an
intermediate good. In each case, there is a correlation between the locations of upstream and downstream firms. Input specificity
is related to both variable costs (transport costs of the input) and fixed costs (learning costs of the use of the input).
When both are low, a connected network emerges, whereas, in the opposite case, we find a partitioned pattern. In the boundary
region, there are multiple equilibria, either asymmetric (mixed network) or symmetric. 相似文献
67.
Davi S. Gaasterland D. Cummins C. III Liesegang G. 《Quantum Electronics, IEEE Journal of》1984,20(12):1458-1465
Energy and power density damage thresholds were determined in air, for plastic IOL's and membranes at the focal point of several solid-state laser systems: 1) 694 nm,Q -switched single pulse (30 ns), multimode, 2) 1064 nm,Q -switched single pulse (20 ns), TEM00 , 3) 1060 nm, mode-locked single pulse, 15 ps, TEM11 , 4) 530 nm, mode-locked single pulse, 15 ps, TEM11 , and 5) 1064 nm, mode-locked pulse train (9-11 pulses, 30 ps), TEM00 . Pulse energies bracketing damage thresholds as well as focal diameter and pulse duration for each system were determined. Energy density thresholds are lower, and power density thresholds higher, for shorter duration pulses-e.g., 23 J/cm2(1.15 GW/cm2) versus 6 J/cm2(400 GW/cm2) at the same wavelength as in systems 2) and 3) (p = 0.005). Damage thresholds for glass IOL's are 37 J/cm2(1.9 GW/cm2) and 37 J/cm2(1235 GW/cm2) as in systems 2) and 5). Damage threshold values for plastic membranes (Saran Wrap®) exposed to nanosecond and picosecond pulse trains of Nd:YAG at 1064 nm are about half that of plastic IOL's. When laser pulses with a cone angle of 14° from systems 2) and 5) are focused on plastic membrane next to the IOL, damage thresholds are 30 J/cm2(1.5 GW/cm2) for 20 nsQ -switched pulses and 20 J/cm2(670 GW/cm2) for trains of 30 ps mode-locked pulses. Damage thresholds of IOL's immersed in 0.9 percent saline are approximately the same as those obtained in air. 相似文献
68.
F Davi HJ Delecluse P Guiet J Gabarre A Fayon O Gentilhomme P Felman C Bayle F Berger J Audouin PA Bryon J Diebold M Rapha?l 《Canadian Metallurgical Quarterly》1998,16(12):3788-3795
PURPOSE: Burkitt-like lymphoma (BLL) is a tumor with morphologic features intermediate between Burkitt's lymphoma (BL) and large-cell lymphoma, but its relationship with these lymphomas is currently unclear. We have therefore analyzed its characteristics within a large series of human immunodeficiency virus (HIV)-associated lymphomas. MATERIALS AND METHODS: Clinical, histologic, immunophenotypic, and molecular analyses were performed on 103 patients with AIDS lymphomas. RESULTS: Nineteen cases (18.4%) were identified as BLL. They were monoclonal B-cell proliferations, as evaluated by immunoglobulin (Ig) gene rearrangement analyses, and had rearrangement of the c-myc oncogene in 68% of cases but not the bcl-2 gene, in contrast to a previous study on non-HIV-associated BLL. This molecular pattern was therefore identical to that of typical BL, suggesting that they represented tumors of similar origin. However, some features could clearly differentiate BLL from BL and were similar to those seen in the diffuse large-cell immunoblastic lymphomas (DLC-IBL) group. These included a greater frequency of Epstein-Barr Virus (EBV) infection (79% v 48%, P = .04), an upregulation of CD39 (50% v 0%, P = .0007) and CD70 (75% v 15%, P = .003) activation antigens and of the CD11a/LFA-1 adhesion molecule (83% v30%, P = .05), and, finally, a lower CD4 count (mean, 119/microL v 270/microL, P = .04). CONCLUSION: BLL is a frequent entity among AIDS lymphomas and should be considered as a morphologic variant of BL in the context of severe immunodepression that occurs in HIV-infected patients. 相似文献
69.
Marlene S. Pontes 《电信纪事》1977,32(11-12):372-376
This paper is concerned with depolarization caused by rain due to nonsphericity of drops and the distribution of their axes orientations. The drops are assumed to be oblate spheroids having canting angles distribution obtained by Saunders. Differential phase shift as well as differential attenuation is important in the calculation of depolarization and the values proposed by Oguchi and Hosoya are utilized. In the first part expression to calculate depolarization amount for a uniform precipitation rate are presented. But communication engineers are usually interested on statistical variations of depolarization amount, so the second part of this paper is concerned with statistical distribution of depolarization. The rain cell proposed by Misme and Fimbel is used to describe the rain model over a path. If the precipitation rate distribution is known in one point of the path, the depolarization distribution is obtained by assuming only one rain cell along the path where, for a long time observation, the precipitation rate distribution for all points is the same. 相似文献
70.
Microstructure and electrical properties of perovskite (Pb, La)TiO3 thin film deposited at low temperature by the polymeric precursor method 总被引:2,自引:0,他引:2
F. M. Pontes J. H. G. Rangel E. R. Leite E. Longo J. A. Varela E. B. Araújo J. A. Eiras 《Journal of Materials Science》2001,36(14):3565-3571
High-quality (Pb, La)TiO3 ferroelectric thin films were successfully prepared on a Pt(111)/Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. The X-ray diffraction patterns show that the films are polycrystalline in nature. This method allows for low temperature (500° C) synthesis, a high quality microstructure and superior dielectric properties. The effects on the microstructure and electrical properties were studied by changing the La content. The films annealed at 500°C have a single perovskite phase with only a tetragonal or pseudocubic structure. As the La content is increased, the dielectric constant of PLT thin films increases from 570 up to 1138 at room temperature. The C-V and P-E characteristics of perovskite thin films prepared at a low temperature show normal ferroelectric behavior, representing the ferroelectric switching property. The remanent polarization and coercive field of the films deposited decreased due to the transformation from the ferroelectric to the paraelectric phase with an increased La content. 相似文献