全文获取类型
收费全文 | 1989篇 |
免费 | 155篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 790篇 |
金属工艺 | 25篇 |
机械仪表 | 42篇 |
建筑科学 | 75篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 414篇 |
水利工程 | 17篇 |
石油天然气 | 7篇 |
无线电 | 100篇 |
一般工业技术 | 235篇 |
冶金工业 | 119篇 |
原子能技术 | 7篇 |
自动化技术 | 241篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 192篇 |
2021年 | 187篇 |
2020年 | 85篇 |
2019年 | 71篇 |
2018年 | 76篇 |
2017年 | 77篇 |
2016年 | 77篇 |
2015年 | 71篇 |
2014年 | 89篇 |
2013年 | 142篇 |
2012年 | 132篇 |
2011年 | 148篇 |
2010年 | 92篇 |
2009年 | 77篇 |
2008年 | 77篇 |
2007年 | 64篇 |
2006年 | 68篇 |
2005年 | 50篇 |
2004年 | 42篇 |
2003年 | 51篇 |
2002年 | 40篇 |
2001年 | 18篇 |
2000年 | 26篇 |
1999年 | 20篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有2146条查询结果,搜索用时 15 毫秒
141.
Wilson Keith G.; Chochinov Harvey Max; McPherson Christine J.; Skirko Merika Graham; Allard Pierre; Chary Srini; Gagnon Pierre R.; Macmillan Karen; De Luca Marina; O'Shea Fiona; Kuhl David; Fainsinger Robin L.; Karam Andrea M.; Clinch Jennifer J. 《Canadian Metallurgical Quarterly》2007,26(3):314
Objective: To investigate the attitudes of terminally ill individuals toward the legalization of euthanasia or physician-assisted suicide (PAS) and to identify those who would personally desire such a death. Design: In the Canadian National Palliative Care Survey, semistructured interviews were administered to 379 patients who were receiving palliative care for cancer. Patients who expressed a desire for physician-hastened death were followed prospectively. Main Outcome Measures: Attitudes toward the legalization of euthanasia or PAS were determined, as was the personal interest in receiving a hastened death. Demographic and clinical characteristics were also recorded, including a 22-item structured interview of symptoms and concerns. Results: There were 238 participants (62.8%) who believed that euthanasia and/or PAS should be legalized, and 151 (39.8%) who would consider making a future request for a physician-hastened death. However, only 22 (5.8%) reported that, if legally permissible, they would initiate such a request right away, in their current situations. This desire for hastened death was associated with lower religiosity (p = .010), reduced functional status (p = .024), a diagnosis of major depression (p 相似文献
142.
Eakin Elizabeth G.; Bull Sheana S.; Riley Kimberley M.; Reeves Marina M.; McLaughlin Patty; Gutierrez Silvia 《Canadian Metallurgical Quarterly》2007,26(4):392
Objective: The Resources for Health trial evaluates a social-ecologically based lifestyle (physical activity and diet) intervention targeting low-income, largely Spanish-speaking patients with multiple chronic conditions. Design: A randomized controlled trial was conducted with 200 patients recruited from an urban community health center and assigned to intervention and usual care conditions. Intervention involved 2 face-to-face, self-management support and community linkage sessions with a health educator, 3 follow-up phone calls, and 3 tailored newsletters. Main Outcome Measures: Primary outcomes measured at 6-months were changes in dietary behavior and physical activity. Changes in multilevel support for healthy living were evaluated as a secondary outcome. Results: After adjustment for age, sex, language, and number of chronic conditions, significant intervention effects were observed for dietary behavior and multilevel support for healthy lifestyles but not for physical activity. Conclusion: The Resources for Health intervention provides an effective and practical model for improving health behavior among low-income, Spanish-speaking patients with multiple chronic conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
143.
Silvia Angelone Marina Cauhapé Casaux Manuel Borghi Fernando O. Martinez 《Materials and Structures》2016,49(5):1655-1665
Nowadays, the disposal of plastic waste is an issue of major concern worldwide because of its considerable volume and growth. An option to tackle this problem is to recycle this waste. This alternative reduces the quantity of net discards, conserves both material and energy and provides a comparatively simple way to make a substantial reduction in the overall volume of solid waste. The purpose of this study is to investigate an environmentally friendly approach about the influence of recycling different percentages of urban and rural plastic waste by adding them in a dry process on an asphalt mixture, through a comparative laboratory study. The resulting mixtures are analyzed considering their volumetric parameters and the values from diverse laboratory mechanical tests. The performance tests include, Marshall stability, Marshall quotient, indirect tensile strength, fracture energy, resilient modulus, permanent deformation and creep compliance, which were carried out on unmodified and modified hot asphalt mixtures. The obtained results are presented and discussed in this paper showing that the reuse of recycled plastics in asphalt mixtures is a viable alternative that contributes to the reduction of plastic wastes as well as the protection of the environment. 相似文献
144.
In this work, we examine the classic problem of robot navigation via visual simultaneous localization and mapping (SLAM), but introducing the concept of dual optical and thermal (cross-spectral) sensing with the addition of sensor handover from one to the other. In our approach we use a novel combination of two primary sensors: co-registered optical and thermal cameras. Mobile robot navigation is driven by two simultaneous camera images from the environment over which feature points are extracted and matched between successive frames. A bearing-only visual SLAM approach is then implemented using successive feature point observations to identify and track environment landmarks using an extended Kalman filter (EKF). Six-degree-of-freedom mobile robot and environment landmark positions are managed by the EKF approach illustrated using optical, thermal and combined optical/thermal features in addition to handover from one sensor to another. Sensor handover is primarily targeted at a continuous SLAM operation during varying illumination conditions (e.g., changing from night to day). The final methodology is tested in outdoor environments with variation in the light conditions and robot trajectories producing results that illustrate that the additional use of a thermal sensor improves the accuracy of landmark detection and that the sensor handover is viable for solving the SLAM problem using this sensor combination. 相似文献
145.
Alexander Kromka Marina Davydova Bohuslav Rezek Milan Vanecek Martin Stuchlik Petr Exnar Martin Kalbac 《Diamond and Related Materials》2010,19(2-3):196-200
Toxic gas sensing device with metal electrodes built into nanocrystalline diamond (NCD) is investigated. The NCD morphology is controlled via seeding and/or deposition time. The surface properties and morphology of NCD are studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). AFM measurements reveal increase in NCD surface area by up to 13%. Gas sensing properties of H-terminated NCD device show high sensitivity towards oxidizing species where the surface conductivity is increased by an order of magnitude for humid air and by three orders of magnitude for COCl2. The surface conductivity exhibits a small decrease to reducing spices (CO2, NH3). 相似文献
146.
A culture-independent and two culture-dependent real time (rt-) PCR approaches were developed to quantitatively identify Listeria monocytogenes in raw milk and soft cheeses. The optimised rt-PCR revealed 100% inclusivity and exclusivity. DNA- and cell-based standard curves showed a good linearity of response (R2 ≥ 0.987 and R2 ≥ 0.998, respectively) for five orders of magnitude (39 × 105 – 3 × 100 genome equivalents and 106–101 CFU equivalents, respectively) with about 100% relative accuracy and inter-assay variability ≤0.90%. Up to 1 genome equivalent/and 10 CFU/reaction were quantified in the DNA and cell standard curves, respectively. The rt-PCR was then combined with a liquid- (MPN technique) or a solid- (ALOA and PALCAM) based enumeration. The diagnostic sensitivity of the different approaches was investigated in artificially contaminated raw milk and soft cheeses. The rt-PCR culture-independent approach performed well in raw milk and (with a lower sensitivity) in stracchino cheese-based standard curves. MPN/rt-PCR was the best approach to enumerate low levels of L. monocytogenes in raw milk and stracchino cheese, while the ALOA-based rt-PCR quantification was more effective than the PALCAM-based. These performances were confirmed when 23 real samples of raw milk and soft cheeses by both the rt-PCR approaches were assayed. 相似文献
147.
This paper presents a method for the diagnosis of active systems, these being a class of distributed asynchronous discrete-event systems, such as digital networks, communication networks, and power transmission protection systems. Formally, an active system is viewed as a network of communicating automata, where each automaton describes the behavior of a system component. The diagnostic method encompasses four steps, namely system modeling, reconstruction planning, behavior reconstruction, and diagnosis generation. System modeling formally defines the structure and behavior of system components, as well as the topology of the active system. Based on optimization criteria, reconstruction planning breaks down the problem of system behavior reconstruction into a hierarchical decomposition. Behavior reconstruction yields an intensional representation of all the dynamic behaviors that are consistent with the available system observation. Eventually, diagnosis generation extracts diagnostic information from the reconstructed behaviors. The diagnostic method is applied to a case study in the power transmission network domain. Unlike other proposals, our approach both deals with asynchronous events and does not require any global diagnoser to be built off-line. The method, which is substantiated by an ongoing implementation, is scalable, incremental, and amenable to parallelism, so that real size problems can be handled. 相似文献
148.
Michal Soreni‐Harari David Mocatta Marina Zimin Yair Gannot Uri Banin Nir Tessler 《Advanced functional materials》2010,20(6):1005-1010
InAs nanocrystals field‐effect transistors with an ON/OFF ratio of 105 are reported. By tailoring the interface regions in the active layer step‐by‐step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 105. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal–nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub‐gap states, and better electronic order (lower σ parameter). Films with enhanced charge transport qualities retain their quantum‐confined characteristics throughout the procedure, thus making them useful for optoelectronic applications. 相似文献
149.
Cheng-Yu HoJui-Jen Chang Jia-Jen LinTsu-Yuan Chin Gincy Marina MathewChieh-Chen Huang 《International Journal of Hydrogen Energy》2011,36(19):12168-12176
For simultaneous saccharification and fermentation of cellulosic bioresources to biofuels, a stable rumen-mimicking bacterial consortium was established and maintained by sub-culturing and is referred to here as the “Functional Rumen Bacterial Consortium” (FRBC). The microbial community was analyzed by denaturing gradient gel electrophoresis, which contained dominant species such as Clostridium xylanolyticum, Clostridium papyrosolvens, Clostridium beijerinckii, Clostridium puniceum, Clostridium putrifaciens, and Ruminococcus sp. These predominant Clostridial strains showed potential in converting lignocellulosic material into bio-hydrogen and bio-fuels. The Clostridial strains with 16S rRNA sequences identical to the DGGE profile were isolated from FRBC. The isolate C. puniceum strain Ru6 exhibited xylanase and pectinase activity and higher hydrogen productivity and was thus chosen as the partner strain for ethanol production with C. xylanolyticum Ru15, which showed additional endoglucanase activity. A co-culture approach was used to reconstruct the FRBC with Ru6 and Ru15, and the productivities of hydrogen and ethanol were comparable to that of the FRBC. These results demonstrate the potential of a biologically inspired rumen-mimic microbial community to produce cellulosic bio-fuels. 相似文献
150.