全文获取类型
收费全文 | 1270篇 |
免费 | 51篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 280篇 |
金属工艺 | 39篇 |
机械仪表 | 12篇 |
建筑科学 | 79篇 |
矿业工程 | 7篇 |
能源动力 | 8篇 |
轻工业 | 149篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 35篇 |
一般工业技术 | 172篇 |
冶金工业 | 389篇 |
原子能技术 | 1篇 |
自动化技术 | 126篇 |
出版年
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 39篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 30篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 68篇 |
2012年 | 45篇 |
2011年 | 78篇 |
2010年 | 52篇 |
2009年 | 54篇 |
2008年 | 48篇 |
2007年 | 64篇 |
2006年 | 50篇 |
2005年 | 49篇 |
2004年 | 28篇 |
2003年 | 25篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 23篇 |
1997年 | 25篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 17篇 |
1989年 | 22篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1981年 | 9篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1971年 | 6篇 |
排序方式: 共有1323条查询结果,搜索用时 671 毫秒
91.
Hepatitis C (HCV) is a serious infection caused by a blood-borne virus. It is a contagious disease spreading via a variety
of transmission mechanisms including contaminated tattoo equipment. Effectively regulating commercial tattoo parlours can
greatly reduce this risk. This paper models the cost-effectiveness and optimal timing of such interventions, and parameterises
the model with data for Vienna, Austria. This dynamic model of the contagious spread of HCV via tattooing and other mechanisms
accounts for secondary infections and shows that regulating tattoo parlours as done in Vienna, Austria in 2003, is a cost-saving
intervention. 相似文献
92.
41 women with bulimia nervosa completed a brief intervention that was designed to promote symptom management. Cutoff scores for the determination of reliable and clinically significant change were calculated for several psychometric instruments that are commonly used as outcome measures in the field of eating disorders. Using these statistical procedures to assess therapeutic change, this study documents the diversity of outcomes that individuals reported following their participation in the intervention. As expected, there was a differential reporting of clinically significant change in favor of specific eating psychopathology relative to personality features and associated psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
94.
The purpose of this paper is to present part of a computer aided design model which was developed for the analysis of millimeter wave rectangular waveguide circuits. This paper focuses on cap resonator circuits and pre-tuned modules for Gunn andimpatt oscillators in the W band. The theoretical results were verified through comparisons with experiments performed in the Ku band. The influence of the main cap circuit parameters are analyzed in order to provide a guidance for theptm design. 相似文献
95.
Xia YAN Marion CHARLIER Thomas GERNAY 《Frontiers of Structural and Civil Engineering》2022,16(9):1071
For open car park structures, adopting a performance-based structural fire design is often justified and allowed because the fire does not reach flashover. However, this design approach requires an accurate assessment of temperatures in structural members exposed to car fires. This paper describes a numerical study on the thermal exposure on steel framing members in open car park fires. Steel temperatures are computed by the coupling of computational fluid dynamics and finite element modeling, and by analytical models from the Eurocodes. In addition, the influence of galvanization on the steel temperature evolution is assessed. Results show that temperatures in unprotected beams and columns are influenced by the section geometry, car fire scenario, modeling approach, and use of galvanization. Galvanization slightly delays and reduces peak temperature. Regarding the different models, CFD-FEM (CFD: computational fluid dynamics, FEM: finite-element method) coupled models predict lower temperatures than the Hasemi model, because the latter conservatively assumes that the fire flame continuously touches the ceiling. Further, the Hasemi model cannot account for the effect of reduced emissivity from galvanization on the absorbed heat flux. Detailed temperature distributions obtained in the steel members can be used to complete efficient structural fire designs based on the member sections, structure layout, and use of galvanization. 相似文献
96.
Bayesian model for flow-class dependent distributions of fecal-indicator bacterial concentration in surface waters 总被引:1,自引:0,他引:1
A Bayesian statistical water quality model is demonstrated to predict fecal-indicator bacterial concentrations for waterbodies without sufficient monitoring data for data-intensive modeling techniques. Using a truncated bivariate normal likelihood function and the readily available observations of flow and bacterial concentration, the Bayesian approach propagates the uncertainty in the model parameterization to the final predictions of in-stream bacterial concentration. The proposed model captures the variation in the magnitude of bacterial loading between dry and wet conditions by estimating separate sets of model parameters for different flow conditions, but also has the capability to pool the data among flow conditions. The model can be used in two ways: first, the model specifies the percent of time that the recreational season in-stream concentration is not in compliance with the relevant water quality standard, and second, the model estimates the necessary bacterial load reduction for multiple flow conditions to meet the relevant water quality standard. Using an eleven year monitoring record for a site sampled at a monthly frequency on the Youghiogheny River in southwestern Pennsylvania, USA, the model parameters are updated and posterior predictions are generated for each 2-year increment. After six years of sampling, the predicted percent of time that the recreational season in-stream bacterial concentration is not in compliance with the relevant water quality is 82% with 95% CI(80,85), and the bacterial load reductions required to meet the standard are 14.7 CI(14.6,14.8), 14.5 CI(14.3, 14.6), and 14.0 CI(13.9, 14.2) log10(cfu/day) for the high, normal, and dry flow conditions, respectively. The change in estimated load reduction and percent exceedance resulting from additional monitoring for this site becomes small after six years of sampling, indicating that a decision does not need to be postponed for additional monitoring. 相似文献
97.
Guoqing Guan Marion Teshima Chie Sato Sung Mo Son Muhammad Faisal Irfan Katsuki Kusakabe Norihiro Ikeda Tsao‐Jin Lin 《American Institute of Chemical Engineers》2010,56(5):1383-1390
Flow patterns in the course of transesterification of waste cooking oil (WCO), sunflower oil (SFO) with water and/or oleic acid as a model of WCO, and pure SFO in the presence of a KOH catalyst in microtubes were investigated. FAME yield for the transesterification of WCO reached more than 89% in the microtube reactors with a residence time of 252 s at 333 K. The flow patterns when using WCO were changed from a liquid–liquid slug flow at the inlet region to a parallel flow at the middle region, and then to a homogeneous liquid flow at the outlet region as the reaction proceeded at 333 K. Fine droplets containing glycerol and methanol generally formed in oil slugs when using pure SFO, but were almost unobservable when using WCO. The soap produced from free fatty acids was considered to be the main factor affecting the flow patterns of WCO and SFO. © 2009 American Institute of Chemical Engineers AIChE J, 2010 相似文献
98.
Chromatographic Methods for the Determination of Carbohydrates and Organic Acids in Foods of Animal Origin 下载免费PDF全文
Marion Pereira da Costa Carlos Adam Conte‐Junior 《Comprehensive Reviews in Food Science and Food Safety》2015,14(5):586-600
Carbohydrates are ubiquitous and range from simple monosaccharides to large complex polysaccharides. Organic acids are compounds with acidic properties. Both occur naturally in many foods and in fermented products. Organic acids are usually derived from the hydrolysis of carbohydrates by microorganisms such as lactic acid bacteria. These bacteria convert carbohydrates into energy required for growth, since they are not equipped with the enzymes necessary for respiration and are unable to perform oxidative phosphorylation. Determination of carbohydrates and organic acids in foods of animal origin is important, since they contribute to flavor and texture. Their presence and proportions can affect the chemical and sensory characteristics of a food matrix and they can provide information on nutritional properties of food and the means to optimize selected technological processes. Furthermore, the levels of carbohydrate and organic acid are important to monitor bacterial growth and activity. Actually, these compounds can be quantified by several methods including high‐performance liquid chromatography (HPLC) and gas chromatography (GC). High‐performance liquid chromatography has been widely used to analyze carbohydrates and nonvolatile organic acids, while gas chromatography has been used to determine the volatile organic acids in complex matrices. This contribution provides an overview of chromatographic methods (HPLC and GC) used to analyze carbohydrates and organic acids in foods of animal origin. 相似文献
99.
Marion Balz Erhard Schulte Hans -Peter Thier 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,202(1):80-81
The quality of an -tocopherol standard can be checked easily by measuring the UV absorbance at minimum (255 nm,A
min) and maximum (292 nm,A
max) wavelengths inn-hexane. If the quotientA
min/A
max exceeds 0.18, the standard contains less than 90% -tocopherol and the determination at 292 nm will yield inaccurate results. 相似文献
100.