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   178篇
  免费   10篇
电工技术   2篇
化学工业   64篇
金属工艺   1篇
机械仪表   3篇
建筑科学   2篇
能源动力   1篇
轻工业   51篇
水利工程   1篇
无线电   9篇
一般工业技术   39篇
冶金工业   3篇
原子能技术   1篇
自动化技术   11篇
  2023年   1篇
  2022年   8篇
  2021年   6篇
  2020年   4篇
  2018年   2篇
  2017年   5篇
  2016年   2篇
  2015年   1篇
  2014年   5篇
  2013年   7篇
  2012年   20篇
  2011年   10篇
  2010年   9篇
  2009年   9篇
  2008年   14篇
  2007年   11篇
  2006年   12篇
  2005年   9篇
  2004年   6篇
  2003年   6篇
  2002年   5篇
  2001年   3篇
  2000年   5篇
  1998年   5篇
  1997年   1篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1988年   1篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1982年   1篇
  1980年   2篇
  1977年   2篇
  1972年   1篇
排序方式: 共有188条查询结果,搜索用时 15 毫秒
91.
Objectives: To examine racial/ethnic disparities in older women's health-related quality of life (QoL) and type of breast cancer treatment as mediated by physician-level and individual-level variables. Methods: A cross-sectional survey of a population-based, consecutive sample identified through the Los Angeles Cancer Surveillance Program of Latina (n = 99), African American (n = 66), and White (n = 92) women aged 55 years or older (N = 257) between 3 and 9 months after primary breast cancer diagnosis and at least 1 month posttreatment. An exploratory, empirically developed latent variable model tested the relationships among demographic and physician-related variables, patient attitudes, and health-related outcomes. Health-related outcomes included QoL measures and receipt of breast conserving surgery (BCS). Results: Latinas reported less BCS and poorer QoL compared with Whites. Physician communication that can empower patients, in terms of patient efficacy in patient?physician interactions and breast cancer knowledge, mitigated racial/ethnic disparities in receipt of BCS. Physician emotional support was not related to patient cognitive empowerment and treatment outcomes. Medical mistrust in minority women was related to less self-efficacy and less positive coping, as well as, both directly and indirectly, to reduced QoL. Latinas reported poorer QoL in the tested model. Conclusion: Physician communication style, specifically information giving and participatory decision making, may empower older women with breast cancer and help mitigate racial/ethnic disparities in surgical treatment received. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
92.
The charge carrier mobility in films of regioregular polythiophenes substituted by n-alkyl side-chains, of butyl, hexyl, octyl, decyl, and dodecyl, was investigated by flash-photolysis time-resolved microwave conductivity (FP-TRMC), and transient photoabsorption spectroscopy excited at 355 nm. The charge carrier concentration was estimated from inspecting radical anions of perylenecarboxydiimide (PDI), which also acts as an efficient electron acceptor to improve the yield of photocarrier generation. We discuss the dependence of side-chain length in terms of decay dynamics, quantum yield of charge carrier generation, and alternating current (ca. 9 GHz) mobility, which exceeded 0.12 cm2/(V s).  相似文献   
93.
The zero-field critical temperature and the coherence length in the layered superconductor 2H-NbSe2−x S x (x = 0–2.0) were investigated. The zero-field critical temperature decreases with increasing the residual resistivity. This result can be explained in terms of the three-dimensional Anderson localization with the mobility edge below the Fermi level. The coherence length as a function ofx can be explained by the theory of the anisotropic three-dimensional dirty superconductor. However it shows anomalous behavior whenx = 0.6. This may be relevant to the change of the crystal structure or the disappearance of the CDW. The effective mass ratio does not depend onx whenx ≤ 0.4.  相似文献   
94.
The specific heat of copper potassium tutton salt has been measured down to 1 mK in order to investigate the hyperfine interaction of this copper compound. The magnetic ordering of the electronic system occurs at 29.5 mK in zero field. Below the transition temperature the electronic heat capacity decreases and the copper nuclear heat capacity of hyperfine splitting becomes dominant in the heat capacity of the compound. The nuclear heat capacity has a broad peak around 3.5 mK. The entropy of copper nuclear spin, which was calculated from the specific heat data, remains at 40% of ln(2I+1) at 1 mK.  相似文献   
95.
In the surface analysis methods such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, or secondary-ion mass spectroscopy, sputtering processes are used for depth profiling. However, ion beam bombardment changes the surface composition and the surface structure, which deteriorates the accuracy of the surface analysis and the depth resolution. We studied the preferential sputtering in some materials consisting of two components with different mass ratio by using the dynamic Monte Carlo simulation. Dose dependence of the depth profile of composition is presented. By Ar sputtering, the surface compositions of Au0.25Cu0.75, Au0.67Al0.33, and Ni0.5Cu0.5 alloys changed to Au0.28Cu0.72, Au0.76Al0.24, and Ni0.67Cu0.33, respectively. These results agreed with the experimental data. In order to compare the effect of mass ratio on the preferential sputtering, B–C, Si–C, and W–C systems were investigated. In B–C system, preferential sputtering by 1 and 3 keV Ar ion was negligible. In W–C system, a significant preferential sputtering occurred. In Si–C system, carbon was enriched in the outermost surface layer at a fluence lower than 3×1016 ions/cm2. At higher fluence, the partiality in concentration recovers because of the balance between the enrichment and the preferential sputtering.  相似文献   
96.
A detection method using the polymerase chain reaction (PCR) was developed to detect genetically modified (GM) potato (NewLeaf Y potato; NL-Y), of which the mandatory assessment has not yet been completed in Japan. The potato sucrose synthase gene was used as an internal control. We designed a primer pair to specifically detect NL-Y without false-positive results in processed potato foods infected with the potato virus Y (PVY). The DNA introduced into NL-Y using the primer pair could be detected from potato powder samples containing 0.05% NL-Y. In addition, we designed primer pairs for recognizing the CryIIIA gene to detect the NewLeaf potato (NL), NewLeaf Plus potato (NL-P) and NL-Y and for recognizing p-FMV in order to detect NL-P and NL-Y. The proposed method was applied to the detection of NL-Y in 26 processed potato foods and NL-Y was not detected in any samples.  相似文献   
97.
A carbon micro/nanostructured composite based on cup-stacked carbon nanotubes (CSCNTs) grown onto a carbon felt has been found to be an efficient matrix for enzyme immobilization and chemical signal transduction. The obtained CSCNT/felt was modified with a copper hexacyanoferrate/polypyrrole (CuHCNFe/Ppy) hybrid mediator, and the resulting composite electrode was applied to H2O2 detection, achieving a sensitivity of 194 ± 15 μA mmol−1 L. The results showed that the CSCNT/felt matrix significantly increased the sensitivity of CuHCNFe/Ppy-based sensors compared to those prepared on a felt unrecovered by CSCNTs. Our data revealed that the improved sensitivity of the as-prepared CuHCNFe/Ppy–CSCNT/felt composite electrode can be attributed to the electronic interactions taking place among the CuHCNFe nanocrystals, Ppy layer and CSCNTs. In addition, the presence of CSCNTs also seemed to favor the dispersion of CuHCNFe nanocrystals over the Ppy matrix, even though the CSCNTs were buried under the conducting polymer layer. The CSCNT/felt matrix also enabled the preparation of a glucose biosensor whose sensitivity could be tuned as a function of the number of glucose oxidase (GOx) layers deposited through a Layer-by-Layer technique with an sensitivity of 11 ± 2 μA mmol−1 L achieved at 15 poly(diallyldimethylammoniumchloride)/GOx bilayers.  相似文献   
98.
In this paper, we have studied the facet and ripple formation on a hemispherical diamond stylus by low energy (0.3-3.0 keV) oxygen ion beam bombardment at different ion incidence angle. The sputtered stylus was observed by SEM. From SEM image, we measured the ion incidence angle θmax where the etching rate is maximum and compared them with the theoretical values of θmax derived from Witcomb formula. From experimentally and theoretically obtained values of θmax, we measured the facet angles of the processed hemispherical diamond stylus. Our result shows increasing discrepancy between theoretical and experimental values of both θmax and facet angle towards lower ion energy (< 2 keV) due to dominance of chemical sputtering over physical sputtering. From our observation we found a diamond stylus can be sharpened at 3 keV ion energy if the original apex angle is > 70°. We also observed surface morphology of the processed hemispherical diamond stylus machined by 0.3-3 keV oxygen ion beam at different tilted conditions. Our observation confirms the formation of ripple on the processed diamond stylus at higher angles of ion incidence. The ripple orientation at ion incidence 40°-60° processed by 3 keV oxygen ion beam is in well agreement with the predictions of linear BH model. However, ripples were not observed at near normal incidence and grazing incidence in contrast to BH model. In order to avoid ripple formation, the diamond stylus needs to be processed within the region of low ion incidence angles. The smoothing region is broader in the low ion energy range but some etch pits are seen to form in this region due to chemical sputtering of the impurities present in the diamond stylus.  相似文献   
99.
We studied the formation dynamics of low-molecular-weight organic semiconducting molecules of N,N′-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N′-diphenylbenzidine (DNTPD) during solvent evaporation. We dropped the DNTPD–toluene solution on a glass substrate and performed in situ measurements of mass, temperature, scattered light intensity, and photoluminescence (PL). We found that both light scattering and PL measurements were able to detect the onset of solid film formation from dissolved organic semiconducting materials. When a solid thin film forms during drying, sudden changes in scattered light and PL are observed. Furthermore, we also found that a period of time after the onset was necessary for completion of thin solid film formation. Observations and in situ PL measurement during thin-film formation by spin coating revealed that this period of time affected the optical properties of the film. This result indicates that quantitative information on the film formation process is quite important to obtain thin films with desired properties by coating and drying. Our in situ measurements were simple and practical approaches to monitor the formation dynamics of organic thin films during drying.  相似文献   
100.
BACKGROUND: Members of the genus Fusarium are well known as one of the most important plant pathogens causing food spoilage and loss worldwide. Moreover, they are associated with human and animal diseases through contaminated foods because they produce mycotoxins. To control fungal hazards of plants, animals and humans, there is a need for a rapid, easy and accurate identification system of Fusarium isolates with molecular methods. RESULTS: To specify genes appropriate for identifying isolates of various Fusarium species, we sequenced the 18S rRNA gene (rDNA), internal transcribed spacer region 1, 5.8S rDNA, 28S rDNA, β‐tubulin gene (β‐tub), and aminoadipate reductase gene (lys2), and subsequently calculated the nucleotide sequence homology with pair‐wise comparison of all tested strains and inferred the ratio of the nucleotide substitution rates of each gene. Inter‐species nucleotide sequence homology of β‐tub and lys2 ranged from 83.5 to 99.4% and 56.5 to 99.0%, respectively. The result indicated that sequence homologies of these genes against reference sequences in a database have a high possibility of identifying unknown Fusarium isolates when it is more than 99.0%, because these genes had no inter‐species pair‐wise combinations that had 100% homologies. Other markers often showed 100% homology in inter‐species pair‐wise combinations. The nucleotide substitution rate of lys2 was the highest among the six genes. CONCLUSION: The lys2 is the most appropriate genetic marker with high resolution for identifying isolates of the genus Fusarium among the six genes we examined in this study. Copyright © 2011 Society of Chemical Industry  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