全文获取类型
收费全文 | 984篇 |
免费 | 5篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 26篇 |
金属工艺 | 2篇 |
机械仪表 | 8篇 |
建筑科学 | 2篇 |
能源动力 | 3篇 |
轻工业 | 9篇 |
无线电 | 20篇 |
一般工业技术 | 25篇 |
冶金工业 | 859篇 |
原子能技术 | 10篇 |
自动化技术 | 22篇 |
出版年
2020年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 27篇 |
1998年 | 238篇 |
1997年 | 131篇 |
1996年 | 99篇 |
1995年 | 66篇 |
1994年 | 51篇 |
1993年 | 56篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 22篇 |
1976年 | 57篇 |
1975年 | 4篇 |
1964年 | 1篇 |
1961年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有989条查询结果,搜索用时 46 毫秒
981.
982.
983.
At VTT, development work has been in progress for 15 years to develop and validate testing and analysis methods applicable for fracture resistance determination from small material samples. The VTT approach is a holistic approach by which to determine static, dynamic and crack arrest fracture toughness properties either directly or by correlations from small material samples. The development work has evolved a testing standard for fracture toughness testing in the transition region. The standard, known as the Master Curve standard is in a way “first of a kind”, since it includes guidelines on how to properly treat the test data for use in structural integrity assessment. No standard, so far, has done this. The standard is based on the VTT approach, but presently, the VTT approach goes beyond the standard. Key components in the standard are statistical expressions for describing the data scatter, and for predicting a specimens size (crack front length) effect and an expression (Master Curve) for the fracture toughness temperature dependence. The standard and the approach, it is based upon, can be considered to represent the state of the art of small specimen fracture toughness characterization. Normally, the Master Curve parameters are determined using test specimens with “straight” crack fronts and comparatively uniform stress state along the crack front. This enables the use of a single KI value and single constraint value to describe the whole specimen. For a real crack in a structure, this is usually not the case. Normally, both KI and constraint vary along the crack front and in the case of a thermal shock, even the temperature will vary along the crack front. A proper means of applying the Master Curve methodology for such cases is presented here. 相似文献
984.
Kim R.W. Wallin 《Engineering Fracture Mechanics》2011,(9):2070-2081
The assessment of structural integrity data requires a statistical assessment. However, most statistical analysis methods make some assumption regarding the underlying distribution. Here, a new distribution-free statistical assessment method based on a combination of Rank and Bimodal probability estimates is presented and shown to result in consistent estimates of different probability quantiles. The method is applicable for any data set expressed as a function of two parameters. Data for more than two parameters can always be expressed as different subsets varying only two parameters. In principle, this makes the method applicable to the analysis of more complex data sets. The strength in the statistical analysis method presented lies in the objectiveness of the result. There is no need to make any subjective assumptions regarding the underlying distribution, or of the relationship between the parameters considered. 相似文献
985.
Stefan Wallin Viktor Leijon Johan Nordlander Nicklas Bystedt 《International Journal of Network Management》2012,22(3):181-198
The development and integration of an alarm interface between network elements and a network management system is a costly process, largely because of the informal way in which alarm interfaces are expressed and communicated. Low‐quality alarm documentation and confusion around fundamental concepts like alarm states and alarm types are typical consequences of current practices. If alarm interfaces were expressed in a more formal manner, costs could be reduced and more advanced analysis and automation would be enabled. We present a novel approach to alarm interfaces by providing a formal alarm model together with a domain‐specific language that allows us to specify both the alarm models and the constraints placed on the alarm models in a consistent manner. This means that we can verify the consistency of an alarm interface and automatically generate artifacts such as alarm correlation rules or alarm documentation based only on the model. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
986.
Cytochromes P-450 are a supergene family of enzymes involved in the metabolism of a wide range of endogenous and foreign compounds. The existing genetic variations of the distinct isozymes lead to interindividually different metabolic capacity. Since vitamin A, endogenous retinoids and their natural metabolites are morphogenic for the sebaceous gland, we investigated the polymorphisms of cytochrome P-450 1A1, as being one of the most active isozymes involved in their interconversion. From the known mutations, two were investigated; an additional cleavage site for MspI in the 3'-flanking region identified as a thymine-to-cytosine transition 1,194 bp downstream of exon 7 (m1) and an adenine-to-guanine transition at position 4889 in exon 7 (m2). We studied 96 acne patients for m1 and m2 mutations by restriction fragment length polymorphism and allele-specific polymerase chain reaction, respectively, and compared the results with 408 reference individuals. No statistically significant difference was found in the distribution of m2 alleles; the frequency was 3.13 and 3.06% of the alleles, respectively (odds ratio = 1.02, confidence limits 0.41-2.52, p = 0.96). In contrast, a trend to an overrepresentation of m1 alleles in acne patients was observed; allele frequency was 8.33 in the patients and 6.99% in the control subjects, respectively (odds ratio 1.21, 95% confidence limits 0.68-2.16, p = 0.52). As the m1 mutation might define a marker for alterations on regulatory sites, the biological efficacy of natural retinoids could be greatly impaired by their rapid metabolism to inactive compounds. The resulting deficit of active natural retinoids may lead to abnormal sebocyte differentiation and hyperkeratinization of the follicular canal implicating the development of acne in some patients. 相似文献
987.
RR Dickerson S Kondragunta G Stenchikov KL Civerolo BG Doddridge BN Holben 《Canadian Metallurgical Quarterly》1997,278(5339):827-830
Photochemical smog, or ground-level ozone, has been the most recalcitrant of air pollution problems, but reductions in emissions of sulfur and hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation back into space and can cool Earth's surface, they also change the actinic flux of ultraviolet (UV) radiation. Observations and numerical models show that UV-scattering particles in the boundary layer accelerate photochemical reactions and smog production, but UV-absorbing aerosols such as mineral dust and soot inhibit smog production. Results could have major implications for the control of air pollution. 相似文献
988.
Phenobarbital is known to reduce serum bilirubin concentration in the newborn infant, but optimal dosage is unknown. Ten pregnant women and their infants were given a standard regimen including prenatal maternal administration and postnatal administration to the infant during the first week of life. The plasma levels of phenobarbital in the infants were found to increase during the period of administration, and to remain high for many days beyond the period of hyperbilirubinemia. Optimal dose schedules for phenobarbital should be based both upon pharmacologic effects (including those other than bilirubin disposition) and upon the pharmacokinetic profile of the drug in the newborn infant. 相似文献
989.
Jeanette M. Wallin Stefan H. Jacobson Lena Axelsson Jenny Lindberg Carina I. Persson Jenny Stenberg Agneta Wennman-Larsen 《Hemodialysis international. International Symposium on Home Hemodialysis》2023,27(4):454-464