全文获取类型
收费全文 | 786篇 |
免费 | 41篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 148篇 |
金属工艺 | 20篇 |
机械仪表 | 29篇 |
建筑科学 | 32篇 |
矿业工程 | 1篇 |
能源动力 | 110篇 |
轻工业 | 53篇 |
水利工程 | 1篇 |
石油天然气 | 5篇 |
无线电 | 60篇 |
一般工业技术 | 177篇 |
冶金工业 | 56篇 |
原子能技术 | 7篇 |
自动化技术 | 121篇 |
出版年
2024年 | 4篇 |
2023年 | 13篇 |
2022年 | 44篇 |
2021年 | 63篇 |
2020年 | 30篇 |
2019年 | 34篇 |
2018年 | 28篇 |
2017年 | 38篇 |
2016年 | 43篇 |
2015年 | 19篇 |
2014年 | 30篇 |
2013年 | 53篇 |
2012年 | 42篇 |
2011年 | 58篇 |
2010年 | 51篇 |
2009年 | 40篇 |
2008年 | 28篇 |
2007年 | 36篇 |
2006年 | 23篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 20篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有836条查询结果,搜索用时 31 毫秒
821.
The electricity tariffs in Oman are subsidized and are based on a cost accounting approach and do not reflect the true cost incurred in generating, transmitting and distributing a kilowatt-hour of electricity at the consumer end. This paper presents the electricity tariff based on the estimation of long-run marginal cost at generation, 33 kV, and 415 voltage level for Ministry of Housing, Electricity & Water (MHEW) interconnected power system of Oman. The result shows that at the generation level a marginal kW costs US$ 75 per year and a marginal kWh costs 2.07 ¢/kWh. These costs increase as we move downstream from generation to consumer end. The average cost of electricity at the consumer end connected at 415 V is 6.52 ¢/kWh or 25.17 Bz/kWh. 相似文献
822.
The present study deals with evaluating the utility sector in terms of energetic and exergetic aspects. In this regard, energy and exergy utilization efficiencies in the Turkish utility sector over a wide range of period from 1990 to 2004 are assessed in this study. Energy and exergy analyses are performed for eight power plant modes, while they are based on the actual data over the period studied. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for each power plants throughout the years, and overall energy and exergy efficiencies are compared for these power plants. The energy utilization efficiencies for the overall Turkish utility sector range from 32.64% to 45.69%, while the exergy utilization efficiencies vary from 32.20% to 46.81% in the analyzed years. Exergetic improvement potential for this sector are also determined to be 332 PJ in 2004. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral and subsectoral energy and exergy utilization to determine how efficient energy and exergy are used in the sector studied. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies. 相似文献
823.
This paper presents an optimal proportional bandwidth allocation and data droppage scheme to provide differentiated services (DiffServ) for downlink pre‐orchestrated multimedia data in a single‐hop wireless network. The proposed resource allocation scheme finds the optimal bandwidth allocation and data drop rates under minimum quality‐of‐service (QoS) constraints. It combines the desirable attributes of relative DiffServ and absolute DiffServ approaches. In contrast to relative DiffServ approach, the proposed scheme guarantees the minimum amount of bandwidth provided to each user without dropping any data at the base‐station, when the network has sufficient resources. If the network does not have sufficient resources to provide minimum bandwidth guarantees to all users without dropping data, the proportional data dropper finds the optimal data drop rates within acceptable levels of QoS and thus avoids the inflexibility of absolute DiffServ approach. The optimal bandwidth allocation and data droppage problems are formulated as constrained nonlinear optimization problems and solved using efficient techniques. Simulations are performed to show that the proposed scheme exhibits the desirable features of absolute and relative DiffServ. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
824.
Muhammad Asif Asghar Aftab Ahmed Muhammad Arif Asghar 《Food Additives and Contaminants: Part B: Surveillance Communications》2018,11(3):167-174
During 2016–2017, 156 samples of fresh milk samples were collected from local markets of Karachi, Pakistan and analysed for aflatoxin M1 (AFM1) contamination using ELISA technique. AFM1 was detected in 143 (91.7%) samples, ranged from 20 to 3090 ng L?1 with a mean level of 346.2 ng L?1. In 125 (80.1%) samples, the AFM1 contamination was greater than the maximum limit (ML = 50 ng L?1) set by EU. However, in 51 (32.7%) samples, the AFM1 level was higher than the ML of 500 ng L?1 as assigned by the USA. Statistical analysis showed that the AFM1 level in milk samples from summer was significantly (p < 0.05) higher than that obtained in winter. It was concluded that the AFM1 levels in the tested samples appear to be a serious public health problem. Therefore, immediate measures should be taken and re-evaluation done for the procedures for farming, transportation, refrigeration, and storage for the control of AFM1 level in milk samples. 相似文献
825.
In this paper, we present a new robust and reversible watermarking approach for the protection of relational databases. Our approach is based on the idea of difference expansion and utilizes genetic algorithm (GA) to improve watermark capacity and reduce distortion. The proposed approach is reversible and therefore, distortion introduced after watermark insertion can be fully restored. Using GA, different attributes are explored to meet the optimal criteria rather than selecting less effective attributes for watermark insertion. Checking only the distortion tolerance of two attributes for a selected tuple may not be useful for watermark capacity and distortion therefore, distortion tolerance of different attributes are explored. Distortion caused by difference expansion can help an attacker to predict watermarked attribute. Thus, we have incorporated tuple and attribute-wise distortion in the fitness function of GA, making it tough for an attacker to predict watermarked attribute. From experimental analysis, it is concluded that the proposed technique provides improved capacity and reduced distortion compared to existing approaches. Problem of false positives and change in attribute order at detection side is also resolved. Additionally, the proposed technique is resilient against a wide range of attacks such as addition, deletion, sorting, bit flipping, tuple-wise-multifaceted, attribute-wise-multifaceted, and additive attacks. 相似文献
826.
Z. Qamar A. K. Sheikh A. F. M. Arif T. Pervez 《Materials and Manufacturing Processes》2007,22(7):804-810
Complexity of the profile being extruded plays a critical role in die design, die reliability, process aberrations, and product defects. Engineering common sense dictates that a more complex die should require a larger amount of extrusion force or pressure. This has been experimentally substantiated by the authors in a recent study. According to a basic definition, therefore, extrusion shape complexity is the ratio of the pressure required to extrude a complex profile to the pressure required for a solid circular profile of the same area. Most of the complexity definitions reported in published literature are based on this interrelationship between extrusion pressure and profile complexity. From a die reliability viewpoint, a complex profile is more difficult to extrude than a simple one, and it generates more stresses in the die. It should therefore lead to an earlier die failure. Another study by the authors confirms that the working life of hot extrusion dies is definitely affected by profile complexity. Reported complexity definitions provide some sort of index to measure extrudability, and can thus be used for pressure prediction to a certain degree. Unfortunately, none of these definitions addresses the very important issue of die reliability, and they generally yield a counterintuitive trend of increasing die life with increasing complexity. None of these definitions includes all the significant geometrical features of a die profile. This article reports the development of two new definitions of shape complexity (linear and power-law) incorporating all significant geometrical features of an extrusion die profile. Die failure data from a large commercial extrusion facility have been collected and analyzed. Regression-based models have been developed for prediction of die failure on the basis of complexity. 相似文献
827.
Tina Gulin-Sarfraz Georgios N. Kalantzopoulos John-Erik Haugen Lars Axelsson Hilde Raanaas Kolstad Jawad Sarfraz 《International journal of molecular sciences》2022,23(13)
Essential oils and their active components have been extensively reported in the literature for their efficient antimicrobial, antioxidant and antifungal properties. However, the sensitivity of these volatile compounds towards heat, oxygen and light limits their usage in real food packaging applications. The encapsulation of these compounds into inorganic nanocarriers, such as nanoclays, has been shown to prolong the release and protect the compounds from harsh processing conditions. Nevertheless, these systems have limited shelf stability, and the release is of limited control. Thus, this study presents a mesoporous silica nanocarrier with a high surface area and well-ordered protective pore structure for loading large amounts of natural active compounds (up to 500 mg/g). The presented loaded nanocarriers are shelf-stable with a very slow initial release which levels out at 50% retention of the encapsulated compounds after 2 months. By the addition of simulated drip-loss from chicken, the release of the compounds is activated and gives an antimicrobial effect, which is demonstrated on the foodborne spoilage bacteria Brochothrix thermosphacta and the potentially pathogenic bacteria Escherichia coli. When the release of the active compounds is activated, a ≥4-log reduction in the growth of B. thermosphacta and a 2-log reduction of E. coli is obtained, after only one hour of incubation. During the same one-hour incubation period the dry nanocarriers gave a negligible inhibitory effect. By using the proposed nanocarrier system, which is activated by the food product itself, increased availability of the natural antimicrobial compounds is expected, with a subsequent controlled antimicrobial effect. 相似文献
828.
Dr. Hiroshi Inaba Minamo Sakaguchi Soei Watari Dr. Shigesaburo Ogawa Dr. Arif Md. Rashedul Kabir Prof. Dr. Akira Kakugo Prof. Dr. Kazuki Sada Prof. Dr. Kazunori Matsuura 《Chembiochem : a European journal of chemical biology》2023,24(8):e202200782
Spatiotemporal modulation of microtubules by light has become an important aspect of the biological and nanotechnological applications of microtubules. We previously developed a Tau-derived peptide as a binding unit to the inside of microtubules. Here, we conjugated the Tau-derived peptide to spiropyran, which is reversibly converted to merocyanine by light, as a reversible photocontrol system to stabilize microtubules. Among the synthesized peptides with spiropyran/merocyanine at different positions, several peptides were bound to the inside of microtubules and stabilized the structures of microtubules. The peptide with spiropyran at the N-terminus induced polymerization and stabilization of microtubules, whereas the same peptide with the merocyanine form did not exert these effects. Reversible formation of microtubules/tubulin aggregates was achieved using the peptide with spiropyran conjugated at the N-terminus and irradiation with UV and visible light. Spiropyran-conjugated Tau-derived peptides would be useful for spatiotemporal modulation of microtubule stability through reversible photocontrol of binding. 相似文献
829.
Eran Y. Bellin William T. Markis Alice M. Hellebrand Christine M. Busby Katy A. Wane Camille R. Jordan Jordan G. Ledvina Steven M. Kaplan Todd R. Metzroth Greg S. Williams Arif Nazir Nathan W. Levin Allen M. Kaufman 《Hemodialysis international. International Symposium on Home Hemodialysis》2023,27(4):465-474
Introduction
For end-stage renal disease (ESRD) patients residing in skilled nursing facilities (SNFs), the logistics and physical exhaustion of life-saving hemodialysis therapy often conflict with rehabilitation goals. Integration of dialysis care with rehabilitation programs in a scalable and cost-efficient manner has been a significant challenge. SNF-resident ESRD patients receiving onsite, more frequent hemodialysis (MFD) have reported rapid post-dialysis recovery. We examined whether such patients have improved Physical Therapy (PT) participation.Methods
We conducted a retrospective electronic medical records review of SNF-resident PT participation rates within a multistate provider of SNF rehabilitation care from January 1, 2022 to June 1, 2022. We compared three groups: ESRD patients receiving onsite MFD (Onsite-MFD), ESRD patients receiving offsite, conventional 3×/week dialysis (Offsite-Conventional-HD), and the general non-ESRD SNF rehabilitation population (Non-ESRD). We evaluated physical therapy participation rates based on a predefined metric of missed or shortened (<15 min) therapy days. Baseline demographics and functional status were assessed.Findings
Ninety-two Onsite-MFD had 2084 PT sessions scheduled, 12,916 Non-ESRD had 225,496 PT sessions scheduled, and 562 Offsite-Conventional-HD had 9082 PT sessions scheduled. In mixed model logistic regression, Onsite-MFD achieved higher PT participation rates than Offsite-Conventional-HD (odds ratio: 1.8, CI: 1.1–3.0; p < 0.03), and Onsite-MFD achieved equivalent PT participation rates to Non-ESRD (odds ratio: 1.2, CI: 0.3–1.9; p < 0.46). Baseline mean ± SD Charlson Comorbidity score was significantly higher in Onsite-MFD (4.9 ± 2.0) and Offsite-Conventional-HD (4.9 ± 1.8) versus Non-ESRD (2.6 ± 2.0; p < 0.001). Baseline mean self-care and mobility scores were significantly lower in Onsite-MFD versus Non-ESRD or Offsite-Conventional-HD.Discussion
SNF-resident ESRD patients receiving MFD colocated with rehabilitation had higher PT participation rates than those conventionally dialyzed offsite and equivalent PT participation rates to the non-ESRD SNF-rehabilitation general population, despite being sicker, less independent, and less mobile. We report a scalable program integrating dialysis and rehabilitation care as a potential solution for ESRD patients recovering from acute hospitalization. 相似文献830.
Jan Ahmad Pu Zhang Khan Kashif Ali Ahmad Izhar Shaukat Ahmed Jawad Hao Zhang Khan Irshad 《SILICON》2022,14(7):3147-3162
Silicon - Recently, geopolymer concrete (GPC) has gained substantial consideration and commercial interest in the construction industry owing to the superior mechanical and chemical properties in... 相似文献