全文获取类型
收费全文 | 2003篇 |
免费 | 80篇 |
专业分类
电工技术 | 38篇 |
综合类 | 3篇 |
化学工业 | 383篇 |
金属工艺 | 22篇 |
机械仪表 | 34篇 |
建筑科学 | 76篇 |
矿业工程 | 4篇 |
能源动力 | 40篇 |
轻工业 | 150篇 |
水利工程 | 18篇 |
石油天然气 | 3篇 |
无线电 | 287篇 |
一般工业技术 | 319篇 |
冶金工业 | 234篇 |
原子能技术 | 18篇 |
自动化技术 | 454篇 |
出版年
2021年 | 32篇 |
2020年 | 17篇 |
2019年 | 27篇 |
2018年 | 33篇 |
2017年 | 45篇 |
2016年 | 43篇 |
2015年 | 44篇 |
2014年 | 66篇 |
2013年 | 109篇 |
2012年 | 98篇 |
2011年 | 111篇 |
2010年 | 91篇 |
2009年 | 100篇 |
2008年 | 113篇 |
2007年 | 83篇 |
2006年 | 95篇 |
2005年 | 83篇 |
2004年 | 78篇 |
2003年 | 77篇 |
2002年 | 54篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 41篇 |
1998年 | 53篇 |
1997年 | 33篇 |
1996年 | 41篇 |
1995年 | 24篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 22篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 20篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1973年 | 13篇 |
1972年 | 9篇 |
排序方式: 共有2083条查询结果,搜索用时 15 毫秒
981.
982.
PJ Moore MA Little PE McSharry JR Geddes GM Goodwin 《IEEE transactions on bio-medical engineering》2012,59(10):2801-2807
Bipolar disorder is characterized by recurrent episodes of mania and depression and affects about 1% of the adult population. The condition can have a major impact on an individual's ability to function and is associated with a long-term risk of suicide. In this paper, we report on the use of self-rated mood data to forecast the next week's depression ratings. The data used in the study have been collected using SMS text messaging and comprises one time series of approximately weekly mood ratings for each patient. We find a wide variation between series: some exhibit a large change in mean over the monitored period and there is a variation in correlation structure. Almost half of the time series are forecast better by unconditional mean than by persistence. Two methods are employed for forecasting: exponential smoothing and Gaussian process regression. Neither approach gives an improvement over a persistence baseline. We conclude that the depression time series from patients with bipolar disorder are very heterogeneous and that this constrains the accuracy of automated mood forecasting across the set of patients. However, the dataset is a valuable resource and work remains to be done that might result in clinically useful information and tools. 相似文献
983.
Khosravi S Hahn JO Dumont GA Ansermino JM 《IEEE transactions on bio-medical engineering》2012,59(3):736-743
This paper presents a new monitor-decoupled model of propofol pharmacodynamics (PD) using the state entropy (SE) as the clinical endpoint of interest. In our model, the dynamics of the entropy monitor are separated from the PD response of the patient by explicitly accounting for the model of the entropy monitor in the PD identification process. The monitor model was then excluded from the identified PD model for the patient. The PD model, thus, obtained is distinct from its traditional counterpart in that it reflects the PD response of a patient with the dynamic effects of the monitor included as a specific entity. System identification trials using SE data of 31 pediatric subjects show that the PD models derived from the proposed approach are an improvement on the traditional approach. For the Paedfusor pharmacokinetic (PK) model, population-averaged effect site equilibration rate constant k(e0) was 5.4 and 3.0 for the proposed and traditional PD models ( p < 0.001), respectively. For the Kataria PK model, population-averaged k(e0) was 2.3 and 1.4 (p < 0.01). This significant difference suggests that the effects of the monitor must be considered when searching for the intrinsic PD of a patient that is free from the bias induced by the monitor characteristics. 相似文献
984.
Michael R. Walsh Marianne E. Walsh Guy Ampleman Sonia Thiboutot Sylvie Brochu Thomas F. Jenkins 《Propellants, Explosives, Pyrotechnics》2012,37(4):393-406
Training with live munitions is an integral component of preparing the modern military for warfare. Energetic compounds, such as propellants and explosives, are consumed during the use of these munitions. These compounds are never fully consumed, however, and the deposition and accumulation of energetic residue on training ranges is the result. This paper summarizes 10 years of research into propellant deposition rates for common military munitions used in the USA and Canada. Research indicates that the firing of howitzers and tanks leave very little residue, the firing of mortars can result in moderate deposition of propellant residue, small‐arms firing positions have the potential for significant residue accumulation, and training with shoulder‐fired rockets and 40 mm machine guns can result in dangerous quantities of unburned propellants. Residue rates vary widely for the weapon systems tested, from 10−6 % for large rocket systems to over 70 % for shoulder‐fired rockets. 相似文献
985.
Cowie CT Rose N Gillett R Walter S Marks GB 《Environmental science & technology》2012,46(5):2918-2927
The aim of this study was to assess the effect of a new road tunnel on the concentration and distribution of traffic-related air pollution (TRAP), specifically nitrogen dioxide (NO(2)) and particulate matter (PM), and to determine its relationship to change in traffic flow. We used continuously recorded data from four monitoring stations at nonroadside locations within the study area and three regional monitors outside the area. The four monitors in the study area were in background locations where smaller pollutant changes were expected compared with changes near the bypassed main road. We also deployed passive samplers to assess finer spatial variability in NO(2) including application of a land use regression model (LUR). The study was conducted from 2006 to 2008. Analysis of the continuously recorded data showed that the tunnel intervention did not lead to consistent reductions in NO(2) or PM over the wider study area. However, there were significant decreases in NO(2), NO(x), and PM(10) in the eastern section of the study area. Analysis of passive sampler data indicated that the greatest reductions in NO(2) concentrations occurred within 100 m of the bypassed main road. The LUR model also demonstrated that changes in NO(2) were most marked adjacent to the bypassed main road. These findings support the use of methods that highlight fine spatial variability in TRAP and demonstrate the utility of traffic interventions in reducing air pollution exposures for populations living close to main roads. 相似文献
986.
Antonio Dore Maria Giovanna Molinu Tullio Venditti Guy D’hallewin 《Food and Bioprocess Technology》2013,6(11):3029-3037
Imazalil (IMZ) plays a key role in the storage and marketing of Citrus fruits. It represents a very important tool in the fight against postharvest pathogens and is an efficient system for reducing economic losses due to the development of rots from Penicillium digitatum and Penicillium italicum. However, the current technologies employed to apply the fungicide by drenching, spraying, or dipping are ever much less suitable and progressive restrictions by law limit the residue level on the fruit and in the waste-water. A critical analysis of the factors affecting imazalil efficacy in postharvest preservation of Citrus fruit suggests that ultrasound could be useful to overcome these drawbacks. Data obtained confirmed a faster and deeper uptake of the fungicide in mandarins and lemons when the fruits were dipped in sonicated imazalil mixtures compared to the un-sonicated ones, allowing reduction of the dose of application and duration of the treatment. Indeed dipping for 1 min in 500 mg?L?1 IMZ sonicated mixture produced in mandarins the same residue level of dipping for 5 min in 1,000 mg?L?1 IMZ mixture without ultrasound. Moreover, imazalil concentration in fruit after sonication did not exceed the maximum residue limit allowed by the law. Sonication did not affect the chemical parameters, weight loss, and rind color of the fruit. No damage on the fruit surface was observed after scanning electron microscopy analyses of the rind of sonicated fruit. The data obtained open new interesting perspectives in the development of new postharvest treatment technologies for Citrus fruit. 相似文献
987.
Guy Hoover 《电源世界》2014,(1):39-41
本文为不同变化范围的差分、单端、单极性和双极性信号提供简便但高性能的模数转换器(ADC)输入驱动器解决方案,所有电路采用了LTC2383-16 ADC单独工作或与LT6350 ADC驱动器一起工作来实现92dB SNR。 相似文献
988.
Snacking is a ubiquitous practice that has increased in recent years. However, the impact of snacking on the diet is difficult to assess because a variety of approaches have been used to define snacking (and snack foods) in the literature. This lack of a universally accepted definition complicates interpretation of the literature and limits the development of science-based recommendations for consumers. The purpose of this review is to illustrate this problem by showing that the conclusions derived from the literature are heavily dependent on the definition used or implied by the authors. It is suggested that the a universally accepted definition for snacking be developed by a coalition of stakeholders to provide a template for future research, guidance for the food industry and to enable the development of well-substantiated dietary recommendations. 相似文献
989.
Khac‐Minh Thai Dr. Andreas Windisch Daniela Stork Dr. Anna Weinzinger Dr. Andrea Schiesaro Robert H. Guy Prof. Dr. Eugen N. Timin Prof. Dr. Steffen Hering Prof. Dr. Gerhard F. Ecker Prof. Dr. 《ChemMedChem》2010,5(3):436-442
The inner cavity of the hERG potassium ion channel can accommodate large, structurally diverse compounds that can be trapped in the channel by closure of the activation gate. A small set of propafenone derivatives was synthesized, and both use‐dependency and recovery from block were tested in order to gain insight into the behavior of these compounds with respect to trapping and non‐trapping. Ligand–protein docking into homology models of the closed and open state of the hERG channel provides the first evidence for the molecular basis of drug trapping. 相似文献
990.
Sylvie Rocheleau Mike Simini Ronald T. Checkai Guy Ampleman 《The Science of the total environment》2010,408(16):3193-3199
The presence of energetic materials (used as explosives and propellants) at contaminated sites is a growing international issue, particularly with respect to military base closures and demilitarization policies. Improved understanding of the ecotoxicological effects of these materials is needed in order to accurately assess the potential exposure risks and impacts on the environment and its ecosystems. We studied the toxicity of the nitroaromatic energetic material 2,4-dinitrotoluene (2,4-DNT) on alfalfa (Medicago sativa L.), barnyard grass (Echinochloa crusgalli L. Beauv.), and perennial ryegrass (Lolium perenne L.) using four natural soils varying in properties (organic matter, clay content, and pH) that were hypothesized to affect chemical bioavailability and toxicity. Amended soils were subjected to natural light conditions, and wetting and drying cycles in a greenhouse for 13 weeks prior to toxicity testing to approximate field exposure conditions in terms of bioavailability, transformation, and degradation of 2,4-DNT. Definitive toxicity tests were performed according to standard protocols. The median effective concentration (EC50) values for shoot dry mass ranged from 8 to 229 mg kg− 1, depending on the plant species and soil type. Data indicated that 2,4-DNT was most toxic in the Sassafras (SSL) and Teller (TSL) sandy loam soils, with EC50 values for shoot dry mass ranging between 8 to 44 mg kg− 1, and least toxic in the Webster clay loam soil, with EC50 values for shoot dry mass ranging between 40 to 229 mg kg− 1. The toxicity of 2,4-DNT for each of the plant species was significantly (p ≤ 0.05) and inversely correlated with the soil organic matter content. Toxicity benchmark values determined in the present studies for 2,4-DNT weathered-and-aged in SSL or TSL soils will contribute to development of an Ecological Soil Screening Level for terrestrial plants that can be used for ecological risk assessment at contaminated sites. 相似文献