首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   130篇
  免费   4篇
电工技术   8篇
综合类   1篇
化学工业   24篇
金属工艺   3篇
机械仪表   2篇
建筑科学   15篇
能源动力   7篇
轻工业   17篇
水利工程   2篇
无线电   9篇
一般工业技术   23篇
冶金工业   15篇
原子能技术   5篇
自动化技术   3篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   1篇
  2019年   3篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   10篇
  2012年   7篇
  2011年   6篇
  2010年   6篇
  2009年   6篇
  2008年   4篇
  2007年   11篇
  2006年   5篇
  2005年   6篇
  2004年   3篇
  2003年   5篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   5篇
  1997年   8篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
  1988年   2篇
  1986年   1篇
  1985年   4篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1976年   2篇
排序方式: 共有134条查询结果,搜索用时 640 毫秒
21.
Type I diabetes susceptibility genes have been identified within the major histocompatibility complex (MHC) on chromosome 6p21.3 and near the VNTR/insulin region on chromosome 11p15.5. We have used polymorphic dinucleotide repeat markers to search the human genome for additional susceptibility genes in 162 type I diabetic families with an affected sibling pair. We report that an additional susceptibility gene is located on chromosome 2q31 near HOXD8 (P < 10(-5), maximum logarithm of odds score = 4.8) in an analysis of affected sibling pairs having specific human leukocyte antigen (HLA) and hypervariable nucleotide tandem repeat (VNTR)/insulin gene haplotypes (absence of high-risk HLA-DR3/4 haplotypes and presence of homozygous high-risk class I VNTR alleles). These results suggest the interaction of a minimum of three genes in the pathogenesis of type I diabetes in humans.  相似文献   
22.
A two-scale evaluation concept of remediation technologies for a contaminated site was expanded by introducing life cycle costing (LCC) and economic input-output life cycle assessment (EIO-LCA). The expanded evaluation index, the rescue number for soil (RNSOIL) with LCC and EIO-LCA, comprises two scales, such as risk-cost, risk-energy consumption or risk-CO2 emission of a remediation. The effectiveness of RNSOIL with LCC and EIO-LCA was examined in a typical contamination and remediation scenario in which dieldrin contaminated an agricultural field. Remediation was simulated using four technologies: disposal, high temperature thermal desorption, biopile and landfarming. Energy consumption and CO2 emission were determined from a life cycle inventory analysis using monetary-based intensity based on an input-output table. The values of RNSOIL based on risk-cost, risk-energy consumption and risk-CO2 emission were calculated, and then rankings of the candidates were compiled according to RNSOIL values. A comparison between three rankings showed the different ranking orders. The existence of differences in ranking order indicates that the scales would not have reciprocal compatibility for two-scale evaluation and that each scale should be used independently. The RNSOIL with LCA will be helpful in selecting a technology, provided an appropriate scale is determined.  相似文献   
23.
Effects of Bi doping in PbTe liquid-phase epitaxial layers grown by the temperature difference method under controlled vapor pressure (TDM-CVP) are investigated. For Bi concentrations in the solution, xBi, lower than 0.2 at.%, an excess deep-donor level (activation energy Ed≈0.03–0.04 eV) appears, and Hall mobility is low. In contrast, for xBi>0.2 at.%, Hall mobility becomes very high, while carrier concentration is in the range of 1017 cm−3. Inductive coupled plasma (ICP) emission analysis shows that, for xBi=1 at.%, Bi concentration in the epitaxial layer is as high as NBi=2.3–2.7 × 1019 cm−3. These results indicate that Bi behaves not only as a donor but also as an acceptor, and the nearest neighbor or very near donor-acceptor (D-A) pairs are formed, so that strong self-compensation of Bi takes place. Carrier concentration for highly Bi-doped layers shows a minimum at a Te vapor pressure of 2.2 × 10−5 torr for growth temperature 470°C, which is coincident with that of the undoped PbTe.  相似文献   
24.
OBJECTIVE: The ratios of immunoglobulin (Ig) G1 and IgG2 in patients with rheumatoid arthritis (RA) were examined by nuclear magnetic resonance (NMR) and the results were compared to data obtained by ELISA. METHODS: The IgG of 11 patients with RA were prepared with a DE-52 column and the specific signals for IgG1 and IgG2 were measured by NMR. The ratios of IgG1 and IgG2 were determined by the intensity of this signal. The samples were also measured by ELISA. RESULTS: The ratios of IgG2 in patients with RA measured by NMR were increased significantly compared to controls. However, there were no significant differences in the data determined by ELISA. Thus, a discrepancy exists in the analysis of IgG2 ratios between NMR and ELISA methods. CONCLUSION: There was a discrepancy in the IgG2 ratios of patients with RA between NMR and ELISA methods, and we attribute this to a conformational difference in IgG2 in patients with RA.  相似文献   
25.
Computerized automatic registration of MR-PET images of the brain is of significant interest for multimodality brain image analysis. Here, the authors discuss the principal axes transformation for registration of three-dimensional MR and PET images. A new brain phantom designed to test MR-PET registration accuracy determines that the principal axes registration (PAR) method is accurate to within an average of 1.37 mm with a standard deviation of 0.78 mm. Often the PET scans are not complete in the sense that the PET volume does not match the respective MR volume. The authors have developed an iterative PAR (IPAR) algorithm for such cases. Partial volumes of PET can be accurately registered to the complete MR volume using the new iterative algorithm. The quantitative and qualitative analyses of MR-PET image registration are presented and discussed. Results show that the new PAR algorithm is accurate and practical in MR-PET correlation studies  相似文献   
26.
Kikuchi  K. Okoshi  T. Arata  R. 《Electronics letters》1984,20(13):535-536
The linewidth of 1.52 ?m InGaAsP lasers was measured as a function of the output power. The result shows that the linewidth is about 15 MHz when the output power is 1 mW. The FM-noise spectrum was also measured in the frequency range from 10 Hz to 100 MHz. The measured spectrum consists of the 1/f-noise and white-noise components. The linewidth calculated from the FM-noise spectrum is in good agreement with the measured value.  相似文献   
27.
A ceramics acid, calcined at temperatures above 1000 °C, was obtained by impregnating aluminum hydroxide with aqueous ammonium metatungstate followed by calcining in air at 1000–1200 °C (1–5 wt% W); its acidity and catalytic activity for decompositions of toluene, ethylbenzene, and cumene are higher than those of silica-alumina.  相似文献   
28.
29.
30.
Conventional sintering techniques of yttria-tetragonal zirconia polycrystals (Y-TZP) ceramics have presented limitations regarding the sintering time and temperature, increasing the cost of the final dental and biomedical products. Herein, microwave sintering comes to be an interesting alternative by providing fast heating, high densification, and grain-size control. The aim of this study was to compare the effect of microwave sintering of Y-TZP dental ceramics prepared from a pre-sintered commercial block and produced from powders synthesized in a laboratorial scale by the precipitation route. The synthetized and commercial discs were submitted to microwave sintering at 1450°C and 1350°C for 15, 30, and 60 minutes. Densification, fracture toughness, grain size, and crystalline phase quantification of the sintered groups were evaluated. Both synthetized and commercial groups sintered at 1450°C for 15 and 30 minutes showed the higher densification results (98% TD). XRD quantitative phase analysis indicates that samples present 89% tetragonal and 11% cubic phases, except for the group prepared from coprecipitated powders sintered at 1450°C for 30 minutes, that presented 79% and 21% of tetragonal and cubic phases. The microwave sintering at 1450°C allows hardness and fracture toughness values comparable to conventional sintering.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号