全文获取类型
收费全文 | 517篇 |
免费 | 14篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 162篇 |
金属工艺 | 20篇 |
机械仪表 | 4篇 |
建筑科学 | 42篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 82篇 |
水利工程 | 1篇 |
石油天然气 | 11篇 |
无线电 | 12篇 |
一般工业技术 | 57篇 |
冶金工业 | 72篇 |
自动化技术 | 49篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 18篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 3篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 24篇 |
2012年 | 18篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 31篇 |
2008年 | 30篇 |
2007年 | 29篇 |
2006年 | 20篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1967年 | 2篇 |
1944年 | 2篇 |
1943年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有531条查询结果,搜索用时 31 毫秒
31.
Jana Velde Ursula Kowalsky Tim Zümendorf Dieter Dinkler 《Computational Materials Science》2009,46(2):352-357
In order to describe the time-dependent inelastic behavior of steel structures up to failure, a material model is developed within the framework of thermodynamics considering viscoplastic material behavior, isotropic hardening, softening, and isotropic ductile damage. Since softening and damage lead to localization of deformations, the model is extended by a non-local implicit gradient formulation. An additional gradient equation is formulated for the local damage variable in order to achieve results independent of the finite-element discretization. The approach is verified by 3D-structural analysis of CT-specimens. 相似文献
32.
Laughing at oneself is considered a core component of the sense of humor in the theories of several authors. In McGhee's (1996) eight-step-training program of the sense of humor, laughing at oneself constitutes one of the most difficult levels. However, until now, only little empirical evidence on laughing at oneself exists. Using a multimethod approach, in the current study, 70 psychology students and a total of 126 peers filled in the Sense of Humor Scale (SHS, McGhee, 1996), containing as a subscale “Laughing at oneself”. In addition, the participants answered the Trait and State forms of the State-Trait-Cheerfulness-Inventory (STCI, Ruch, K?hler, & van Thriel, 1996; Ruch, K?hler, & van Thriel, 1997). They then were confronted with six distorted images of themselves. Facial responses of the participants were videotaped and analyzed using the Facial Action Coding System (FACS, Ekman, Friesen, & Hager, 2002). Four indicators of exhilaration were examined: (a) experienced funniness, (b) AU12 smiles, (c) Duchenne displays, and (d) laughter. Furthermore, fake and masking smiles were studied. Results demonstrated that self- and peer reports of “laughing at oneself” converged moderately. All four indicators of exhilaration were shown, but funniness and laughter seemed to be the most strongly related indicators. Trait cheerfulness and (low) seriousness, and a cheerful mood state formed further characteristics of persons who laugh at themselves. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
33.
Taisa Venäläinen Ursula Schwab Jyrki Ågren Vanessa de Mello Virpi Lindi Aino-Maija Eloranta Sanna Kiiskinen David Laaksonen Timo A. Lakka 《Lipids》2014,49(5):467-479
Plasma fatty acid (FA) composition is known to be an indicator of dietary fat quality, but the associations of other dietary factors with plasma FA composition remain unknown in children. We investigated the cross-sectional associations of food consumption with the proportions of FA and estimated desaturase activities in plasma cholesteryl esters (CE) and phospholipids (PL) among children. The subjects were a population sample of 423 children aged 6–8 years examined at baseline of The Physical Activity and Nutrition in Children (PANIC) Study. We assessed food consumption by food records and plasma FA composition by gas chromatography. We used linear regression models adjusted for age, sex, physical activity and total energy intake to analyze the associations. A higher consumption of vegetable oil-based margarine (fat 60–80 %) was associated with a higher proportion of linoleic and α-linolenic acids in plasma CE and PL. A higher consumption of high-fiber grain products was related to a lower proportion of oleic acid in CE and PL. The consumption of candy was directly associated with the proportion of palmitoleic and oleic acid in plasma CE. The consumption of vegetable oil-based margarine was inversely associated with estimated stearoyl-CoA-desaturase activity in plasma CE and PL and the consumption of candy was directly related to it in plasma CE. The results of our study suggest that plasma FA composition is not only a biomarker for dietary fat quality but also reflects the consumption of high-fiber grain products and foods high in sugar among children. 相似文献
34.
The choice of statistical distributions characterising microbial counts is essential in risk assessment and risk management. While the lognormal distribution has been long used to directly model the microbial data obtained from food samples, it does not allow for complete absence of microorganisms in a sample. Within a heterogeneous Poisson theoretical interpretation, a gamma or a lognormal population distribution for the unknown microbial concentration and a Poisson measurement distribution produces a discrete Poisson-gamma (λ, 1/k) or a Poisson-lognormal (μ,σ) distribution of observed plate counts. The capability of both distributions to deal with clustering was compared using six data sets of variable proportion of zero counts: total viable counts, coliforms and Escherichia coli on pre-chill and post-chill beef carcasses. Whereas the Poisson-lognormal distribution fitted better to the high counts data sets, the Poisson-gamma distribution represented the low counts data sets (13–81% zero counts) by far better than the Poisson-lognormal – which invariably tended to have a longer tail, an overestimated mean log and a lower predicted probability of zero counts. The inverse close relationship between the observed proportion of zero counts in the data set and the fitted dispersion factor 1/k suggested the possibility of obtaining a first approximation of 1/k by this means. Finally, in absence of zero counts, it was demonstrated that fitting a Poisson-lognormal to the observed plate count data can be closely approximated by the common practice of fitting a simple normal distribution to the back-calculated ‘unobserved’ mean concentrations in log CFU/g. 相似文献
35.
Stefan Kwiatkowski Ursula Thielen Phyllis Glenney Colm Moran 《Journal of the Institute of Brewing》2009,115(2):151-158
Much research has been carried out over the years examining cell wall glucans from Saccharomyces cerevisiae and this study further examines aspects of the binding of (1r?4)‐α‐D‐glucan in the yeast cell wall, using a number of isolation techniques as well as monoclonal antibodies able to recognize a mixed (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan. Extraction of purified glucan, from S. cerevisiae cell wall, with 0.1N HCl, at 80°C for 6 h, released into the solution (1r?4)‐α‐D‐glucan and (1r?6)‐β‐D‐glucan as the major polysaccharides, along with an insoluble pellet highly enriched in (1r?3)‐β‐D‐glucan. The released (1r?4)‐α‐D‐glucan was composed of a high molecular size >100 kDa fraction (7.2% w/w) and a medium 5–50 kDa polysaccharide (10.2% w/w), with the (1r?4)‐α‐D‐glucan covalently bound to the (1r?6)‐β‐D‐glucan. The average molar ratio of the α:β glucan was 47: 53 in this mixed polysaccharide. The structure of this polysaccharide was different from the structure of plant starch or animal glycogen as monoclonal antibodies specific to yeast (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan did not recognize the plant starch or animal glycogen standards. 相似文献
36.
Observed 72 infants aged 12, 18, and 24 mo in the presence of their mothers and 2 adult female strangers to assess their willingness to initiate proximal interaction (PI) with unfamiliar adults. Mothers and strangers were asked to be warmly responsive to infant overtures but not to invite interaction from the infant. A majority of the infants at the 3 ages initiated PI with one or both strangers, often repeatedly. For those who engaged in 2 or more PI bouts with the strangers, a significant upward trend in bout duration and intensity was noted. Older infants gave more toys to the strangers and initiated more mutual play. Stranger–mother distance affected amount of proximity, not PI. Mother–stranger conversation was associated with less PI with the conversing stranger. At all ages infants sought more PI with their mothers than with the strangers. Although infants initiated an appreciable amount of PI with the strangers during the 40-min observation, comparison with other studies indicates that a stranger who takes the initiative by inviting play can establish more rapport much sooner. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
Christofi N Aspichueta E Dalzell D De la Sota A Etxebarria J Fernandes T Gutierrez M Morton J Obst U Schmellenkamp P 《Water research》2003,37(1):177-187
A laboratory model nitrifying activated sludge plant treating OECD synthetic sewage was designed and constructed by each of three laboratories in Germany, Scotland and Spain in order to produce a sludge inoculum for 5 rapid toxicity bioassays. The plants were run for 3 years and produced sludge for the microbially based bioassays Vibrio fischeri bioluminescence, ATP luminescence and respiration, and, nitrification and enzyme inhibition. Although the initial sludge inoculum for the plants differed, as did some of the running conditions such as temperature regime, the sludge produced within the different countries had similar characteristics with respect to sludge age, total suspended solids and volatile suspended solids. Nitrification was generally maintained over the 3-year period although there were occasions when the process was inconsistent. Nitrification recovery was afforded by reseeding with a nitrifying sludge from a local wastewater treatment works (WWTW) or imposition of starvation conditions for a period of time. The sludge produced was used to carry out toxicity testing and results compared well with those using sludge from a WWTW. Overall, the use of sludge generated in the laboratory could be used for toxicity testing negating the need to resort to the use of natural WWTW sludge, which may contain a range of toxic substances due to uncontrolled industrial and domestic inputs and an unbalanced microbial consortium. 相似文献
38.
Anderson Ursula S.; Stoinski Tara S.; Bloomsmith Mollie A.; Maple Terry L. 《Canadian Metallurgical Quarterly》2007,121(1):1
The ability to select the larger of two quantities ranging from 1 to 5 (relative numerousness judgment [RNJ[) and the ability to select the larger of two pairs of quantities with each pair ranging from 1 to 8 (summation) were evaluated in young, middle-aged, and older adult orangutans (7 Pongo pygmaeus abelii and 2 Pongo pygmaeus pygmaeus). Summation accuracy and RNJ were similar to those of previous reports in apes; however, the pattern of age-related differences with regard to these tasks was different from that previously reported in gorillas. Older orangutans were less accurate than the young and middle-aged for RNJ, and summation accuracy was equivalent among age groups. Evidence was found to suggest that the young and middle-aged based their selection of the largest quantity pair on both quantities within each pair during the summation task. These results show a relationship between subject age and the quantitative abilities of adult orangutans. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Hanne Gottliebsen Ruth Hardy Olga Lightfoot Ursula Martin 《Formal Aspects of Computing》2013,25(6):993-1016
Real number theorem proving has many uses, particularly for verification of safety critical systems and systems for which design errors may be costly. We discuss a chain of developments building on real number theorem proving in PVS. This leads from the verification of aspects of an air traffic control system, through work on the integration of computer algebra and automated theorem proving to a new tool, NRV, first presented here that builds on the capabilities of Maple and PVS to provide a verified and automatic analysis of Nichols plots. This automates a standard technique used by control engineers and greatly improves assurance compared with the traditional method of visual inspection of the Nichols plots. 相似文献
40.