全文获取类型
收费全文 | 1594篇 |
免费 | 118篇 |
专业分类
电工技术 | 6篇 |
综合类 | 6篇 |
化学工业 | 510篇 |
金属工艺 | 16篇 |
机械仪表 | 15篇 |
建筑科学 | 122篇 |
矿业工程 | 1篇 |
能源动力 | 27篇 |
轻工业 | 303篇 |
水利工程 | 25篇 |
石油天然气 | 6篇 |
无线电 | 66篇 |
一般工业技术 | 256篇 |
冶金工业 | 193篇 |
原子能技术 | 3篇 |
自动化技术 | 157篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 66篇 |
2021年 | 86篇 |
2020年 | 43篇 |
2019年 | 57篇 |
2018年 | 57篇 |
2017年 | 49篇 |
2016年 | 55篇 |
2015年 | 52篇 |
2014年 | 79篇 |
2013年 | 119篇 |
2012年 | 102篇 |
2011年 | 138篇 |
2010年 | 109篇 |
2009年 | 80篇 |
2008年 | 78篇 |
2007年 | 77篇 |
2006年 | 56篇 |
2005年 | 53篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 32篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 3篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1964年 | 2篇 |
排序方式: 共有1712条查询结果,搜索用时 15 毫秒
51.
Tanja Stahl Caroline Rothe Manja U. B?hme Aloisa Kohl Nicolaus Kr?ger Boris Fehse 《International journal of molecular sciences》2016,17(9)
Accurate and sensitive determination of hematopoietic chimerism is a crucial diagnostic measure after allogeneic stem cell transplantation to monitor engraftment and potentially residual disease. Short tandem repeat (STR) amplification, the current “gold standard” for chimerism assessment facilitates reliable accuracy, but is hampered by its limited sensitivity (≥1%). Digital PCR (dPCR) has been shown to combine exact quantification and high reproducibility over a very wide measurement range with excellent sensitivity (routinely ≤0.1%) and thus represents a promising alternative to STR analysis. We here aimed at developing a whole panel of digital-PCR based assays for routine diagnostic. To this end, we tested suitability of 52 deletion/insertion polymorphisms (DIPs) for duplex analysis in combination with either a reference gene or a Y-chromosome specific PCR. Twenty-nine DIPs with high power of discrimination and good performance were identified, optimized and technically validated. We tested the newly established assays on retrospective patient samples that were in parallel also measured by STR amplification and found excellent correlation. Finally, a screening plate for initial genotyping with DIP-specific duplex dPCR assays was designed for convenient assay selection. In conclusion, we have established a comprehensive dPCR system for precise and high-sensitivity measurement of hematopoietic chimerism, which should be highly useful for clinical routine diagnostics. 相似文献
52.
Kernel density estimation based on Ripley’s correction 总被引:1,自引:0,他引:1
In this paper, we investigate a technique inspired by Ripley’s circumference method to correct bias of density estimation of edges (or frontiers) of regions. The idea of the method was theoretical and difficult to implement. We provide a simple technique – based of properties of Gaussian kernels – to efficiently compute weights to correct border bias on frontiers of the region of interest, with an automatic selection of an optimal radius for the method. We illustrate the use of that technique to visualize hot spots of car accidents and campsite locations, as well as location of bike thefts. 相似文献
53.
Caroline Gollub Stanislav Avdoshenko Rafael Gutierrez Yuri Berlin Gianaurelio Cuniberti 《Israel journal of chemistry》2012,52(5):452-460
Charge migration is a ubiquitous phenomenon with profound implications throughout many areas of chemistry, physics, biology, and materials science. The long-term vision of designing functional materials with tailored molecular-scale properties has triggered an increasing quest to identify prototypical systems where truly molecular conduction pathways play a fundamental role. Such pathways can be formed due to the molecular organization of various organic materials and are widely used to discuss electronic properties at the nanometer scale. Here, we present a computational methodology to study charge propagation in organic molecular stacks at nano and sub-nanoscales and exploit this methodology to demonstrate that moving charge carriers strongly affect the values of the physical quantities controlling their motion. The approach is also expected to find broad application in the field of charge migration in soft matter systems. 相似文献
54.
Marcio Schmiele Leandra Zafalon Jaekel Stella Maris Cardoso Patricio Caroline Joy Steel Yoon Kil Chang 《International Journal of Food Science & Technology》2012,47(10):2141-2150
The use of bran and whole grain flour changes dough rheology and causes difficulties in manufacturing bakery products. The aim of this study was to analyse the influence of substituting refined wheat flour (WF) by wheat bran (WB; 5%, 10%, 20%, 30% and 40%) or whole grain wheat flour (WGWF; 10%, 20%, 30%, 40% and 50%) on dough rheological properties and pan bread quality characteristics. The addition of WB and WGWF increased water absorption and resistance to extension and decreased stability, extensibility and peak viscosity. Effects with WB were more pronounced. The presence of WB or WGWF increased crumb moisture content, firmness and hardness and decreased specific volume of pan bread. It is important to set new farinographic and extensographic standards when using WB and WGWF, allowing for a correct correlation between rheology and quality characteristics of bakery products, as the same standards used for WF are not valid. 相似文献
55.
Amélie Deglaire Caroline Méjean Katia Castetbon Emmanuelle Kesse-Guyot Christine Urbano Serge Hercberg Pascal Schlich 《Food quality and preference》2012,23(2):110-124
Liking for a sweet, salty or fatty diet may induce overconsumption of simple carbohydrates, sodium or lipids. Measuring overall liking of the corresponding sensory sensations contributes to understanding the determinants of dietary behaviours. However, no standardized validated questionnaire assaying these sensations is currently available. In the present study, we developed a web-based questionnaire, “PrefQuest”, which measures recalled liking for the following four sensations: salt, fat and salt, sweet, fat and sweet. PrefQuest included four types of items: (1) liking for sweet, fatty-sweet and fatty-salty foods, (2) preferences in the level of seasoning by adding salt, sweeteners, or fat, (3) preferences for types of dishes in a restaurant menu and (4) overall questions about sweet-, salt- and fat-related behaviours. A development study (n = 198) demonstrated that PrefQuest was feasible, well-perceived, only lasted about 20 min and that items were repeatable (overall mean intra-class correlation coefficient: 0.77, SD 0.08). Construct validity was then evaluated on a larger population sample (n = 47 803). The underlying structure within each of the four sensations was determined by exploratory factor analysis and then internally validated by confirmatory factor analysis. After a selection of the most relevant items, the salt, fat-and-salt, sweet, and fat-and-sweet scales exhibited a theoretically meaningful factor structure, unidimensional for the salt scale and with interrelated sub-dimensions for the sweet, fat-and-salt, and fat-and-sweet scales. Based on the fat-and-sweet and fat-and-salt scales, a fat model was also unveiled. For each factor, internal consistency as well as convergent and divergent validities were demonstrated. Overall, PrefQuest is an internally valid and original tool that can be used to assay recalled liking for sweet, salt, and fat considered altogether or separately as fat and salt or fat and sweet, and can be applied to large population surveys. 相似文献
56.
57.
58.
Determination of alcohols and volatile organic acids in anaerobic bioreactors for H2 production by near infrared spectroscopy 总被引:1,自引:0,他引:1
Maurílio Gustavo Nespeca Caroline Varella Rodrigues Kamili Oliveira Santana Sandra Imaculada Maintinguer José Eduardo de Oliveira 《International Journal of Hydrogen Energy》2017,42(32):20480-20493
In recent years, near infrared (NIR) spectroscopy has been investigated as a tool for monitoring anaerobic digesters, but several adversities in its application have been reported. This study proposes the application of NIR for the determination of alcohols and volatile organic acids from H2 production bioreactors and evaluates different approaches to optimize the prediction models. Partial least squad (PLS) models were developed using samples from anaerobic batch reactors fed with crude glycerol for wastewater treatment. The analytes predicted were: methanol, ethanol, 1-butanol, acetic, propanoic, butyric, isocaproic and total volatile organic acids (VFA). The optimization of the predictive capacity of the models was achieved through the orthogonal signal correction (OSC) preprocessing and the selection of variables performed by the genetic algorithm (GA). The application of the proposed models were based on the following figures of merit: accuracy, precision, linearity, limits of detection and quantitation, measurement interval, sensitivity, selectivity, signal-to-noise ratio and bias. Despite the low selectivity (maximum of 0.12%), the models presented high sensitivity [γ?1 = 0.19 (mg L?1)?1], low LOQ (1 mg L?1) and correlation between reference and predicted values (r) at least 0.93, except for propanoic acid (rpred = 0.85). The F-test revealed that the selection of variables by GA significantly improved the accuracy and linearity of the prediction models for methanol, acetic acid, isocaproic acid and VFA. NIR spectroscopy has proved to be a powerful tool for monitoring H2 production bioreactors since provides fast, low cost and multicomponent information. 相似文献
59.
Selma Ben Saad Caroline Gentric Jean-François Fourmigué Patrice Clément Jean-Pierre Leclerc 《Chemical Engineering Research and Design》2014
High performance of compact heat exchangers is conditioned by correct fluid distribution. This is especially true for gas–liquid heat exchangers where a uniform distribution is particularly delicate to obtain and where maldistribution entails significant performance deterioration. Several phenomena can lead to phase distribution problems: the fins may be subject to manufacturing defects or fouling, leading to shortcuts or dead zones. But the first source of maldistribution may be a poor distribution at the outlet of the entrance distributor. This distributor aims at mixing the phases and distributing them across the channels. 相似文献
60.
This study examined directly the impact of various factors associated with driving on ‘A-class’ roads in the United Kingdom (specifically length of platoon, proportion of heavy goods vehicles (HGVs), speed and opportunities for overtaking) on self-reported frustration and overtaking intentions. The impact of situational variables (being under time pressure, and time behind a slower moving platoon) were also examined, as was the association between frustration and self-reported overtaking intentions. 183 members of the public from the areas around Perth and Inverness, Scotland took part in the study. Participants viewed simulated ‘driver’s viewpoint’ clips representing all the combinations of the experimental variables (except time pressure, which was a between-groups variable, and time behind platoon, which was examined separately in four specific clips). After each clip, participants responded on a paper questionnaire as to the level of frustration they would feel for a given clip, and the likelihood that at some point during the clip they would have attempted an overtake manoeuvre. The findings show that the links between traffic variables such as speed and platoon length, and behaviourally-relevant variables such as frustration and overtaking intentions, are not simple. Although there are broad and predictable effects of speed and platoon length (lower speeds and longer platoons leading to greater frustration) these are mediated by other variables, and it is not always the case that more frustration leads to more intention to overtake. Analysis of driver attitudes identified three clusters (low, medium and high risk drivers) and suggests that higher risk drivers’ levels of frustration are more affected by situational changes than those of lower risk drivers. 相似文献