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   485篇
  免费   8篇
电工技术   5篇
化学工业   81篇
金属工艺   6篇
机械仪表   4篇
建筑科学   32篇
矿业工程   1篇
能源动力   11篇
轻工业   39篇
水利工程   17篇
石油天然气   19篇
无线电   24篇
一般工业技术   46篇
冶金工业   168篇
自动化技术   40篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   5篇
  2017年   3篇
  2016年   5篇
  2015年   2篇
  2014年   11篇
  2013年   31篇
  2012年   18篇
  2011年   14篇
  2010年   16篇
  2009年   9篇
  2008年   18篇
  2007年   13篇
  2006年   21篇
  2005年   7篇
  2004年   8篇
  2003年   8篇
  2002年   9篇
  2001年   6篇
  2000年   13篇
  1999年   12篇
  1998年   48篇
  1997年   33篇
  1996年   26篇
  1995年   14篇
  1994年   9篇
  1993年   10篇
  1992年   9篇
  1991年   7篇
  1990年   2篇
  1989年   2篇
  1988年   5篇
  1987年   13篇
  1986年   6篇
  1985年   11篇
  1984年   6篇
  1983年   4篇
  1982年   9篇
  1981年   12篇
  1980年   7篇
  1978年   3篇
  1977年   3篇
  1976年   7篇
  1975年   2篇
  1974年   2篇
  1972年   1篇
  1969年   1篇
排序方式: 共有493条查询结果,搜索用时 15 毫秒
11.
ABSTRACT

A chromatographic-infrared method has been used for the separation and characterization of acid compound types in shale oil high-boiling distillates. Acid compound concentrates are separated by high performance liquid chromatography (HPLC) on basic alumina, and the chromatographic subfractions are analyzed by quantitative infrared spectrometry. The analyses are reproducible, and generally 90 percent or more of the material is analyzed. Major acid compound types identified in shale oils are phenols, pyrrolic nitrogen compounds, and amides.  相似文献   
12.
ABSTRACT

The paper describes the effect of time and pressure on liquid product yields when Green River shale was exposed to supercritical methanol-water at 400°C and then extracted with benzene-methanol. Reaction times between 1 second and 34 minutes were studied as were pressures between 1800 and 5200 psi. Maximum yields of liquid product were obtained after a methanol-water treatment time of about 34 minutes. Presssure did not have a significant effect on product yields. Chemical characterization of Selected liquid products is reported and shows that the product composition varies with time. Exfoliation of shale also increases with treatment time. This phenomenon is discussed and illustrated.  相似文献   
13.
Sustainable development is the modern rhetoric to guide environmental or natural resources management. There are many ways to do this and one is the wider utilization of economic instruments, such as taxes and levies. Although such levies are becoming common in Australia and worldwide, the role of the taxes or levies is still limited. In many cases, these taxes/levies -although environmentally related- have a fiscal rather than a purely environmental motive, for example, the Natural Resources Management (NRM) Levy in South Australia. This study evaluates the NRM levy policy using one NRM region and focussing on the Adelaide urban community. Data was collected through a web-based survey with 770 respondents who answered 59 questions. The research found that community strongly prefers a levy calculated on the volume of water consumed. Respondents also indicated that they would use less water if the levy were calculated on the volume of water consumed. The clear implications of the results suggest that if a tax or levy aims to change water consumption behaviour then it should be based on the volume of water consumed not on property value.  相似文献   
14.
This study tested whether coordinated care management (CCM), a continuity of care intervention for substance use disorders (SUD), improved rates of abstinence when compared with usual welfare management for substance-using single adults and adults with dependent children applying for public assistance. The study was designed as a practical clinical trial and was implemented in partnership with a large city welfare agency. Participants were 421 welfare applicants identified via SUD screening and assigned via an unbiased computerized allocation program to a site that provided either CCM (n = 232) or usual care (UC; n = 189). Outcomes were assessed for 1 year postbaseline with self-reports and biological measures of substance use. As hypothesized, for participants not enrolled in methadone maintenance programs (n = 313), CCM clients received significantly more services than did UC clients. Nonmethadone CCM also showed significantly higher abstinence rates (odds ratio = 1.75; 95% confidence interval = 1.12, 2.76; d = 0.31) that emerged early in treatment and were sustained throughout follow-up. In contrast, no treatment services or outcome effects were found for methadone maintenance clients (n = 108). Findings suggest that CCM is promising as a wraparound to SUD treatment for welfare recipients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
15.
An analytical solution for a two resistance mass transfer model explaining the adsorption of Astrazone Blue dye (Basic Blue 69) onto Sorbsil silica has been developed. The model includes a film mass transfer coefficient, kf1 = 80 × 10−6cm·s−1, and an internal effective diffusivity, Deff = 18×10−9cm2·s−1 which controls the internal mass transport processes based on a pore diffusion mechanism.  相似文献   
16.
Indirect cytotoxicity evaluation of pseudowollastonite   总被引:1,自引:0,他引:1  
This study aimed to evaluate the cytotoxicity of substances leached by pseudowollastonite (CaSiO3). It has been previously shown that calcium (Ca2+) and silicate (SiO3 ) ions are released from pseudowollastonite into biological solutions. Both of these ions are known to influence the biological metabolism of osteoblastic cells essential in the mineralization process and bone-bonding mechanism. The indirect toxicity evaluation was performed by extraction method, according to International Standard Organization (ISO). Pseudowollastonite pellets obtained by solid-state reaction were incubated, in culture medium, during 24, 48, 72 or 168 h at different concentrations (5, 10, 15, 50, 100, 200 mg/ml). The cytotoxicity of each extract in presence of human osteoblastic cell line (SaOS-2) was quantitatively assessed by measuring the viability (succinate dehydrogenase activity, MTT), the membrane integrity (the uptake of the neutral red by viable cells, NR) as well as the cell necrosis by measuring the lactate dehydrogenase (LDH) released in the culture medium. No significant alteration of membrane integrity or cell suffering was detectable. However, increased cell metabolism was observed for cells exposed to pseudowollastonite extract with longest extraction time (168 h). In conclusion, mineral elements leached by pseudowollastonite do not significantly affect the metabolism of osteoblastic cells.  相似文献   
17.
This review documents the uses of quantitative MS applied to colorectal cancer (CRC) proteomics for biomarker discovery and molecular pathway profiling. Investigators are adopting various labeling and label-free MS approaches to quantitate differential protein levels in cells, tumors, and plasma/serum. We comprehensively review recent uses of this technology to examine mouse models of CRC, CRC cell lines, their secretomes and subcellular fractions, CRC tumors, CRC patient plasma/serum, and stool samples. For biomarker discovery these approaches are uncovering proteins with potential diagnostic and prognostic utility, while in vitro cell culture experiments are characterizing proteomic and phosphoproteomic responses to disrupted signaling pathways due to mutations or to inhibition of drugable enzymes.  相似文献   
18.
Business publications and the popular press have stressed the importance of creating conditions for meaningful employee expression in work roles, also known as engagement. Few empirical studies, however, have examined how individual or situational factors relate to engagement. Consequently, this study examines the interplay between employee age, perceived coworker age composition, and satisfaction with older (older than 55) and younger (younger than 40) coworkers on engagement using a sample of 901 individuals employed in the United Kingdom. Results indicated that satisfaction with one's coworkers related significantly to engagement. Moreover, perceived age similarity was associated with higher levels of engagement among older workers when they were highly satisfied with their coworkers over 55 and lower levels of engagement when they were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
19.
A previous randomized trial with 224 alcohol and/or cocaine addicts who had completed an initial phase of treatment indicated that 12 weeks of telephone-based continuing care yielded higher abstinence rates over 24 months than did group counseling continuing care. The current study examined mediators of this treatment effect. Results suggested that self-help involvement during treatment and self-efficacy and commitment to abstinence 3 months after treatment mediated subsequent abstinence outcomes. These analyses controlled for substance use prior to the assessment of mediators. Conversely, there was no evidence that self-help beliefs or social support mediated the treatment effect. These results are consistent with a model in which treatment effects are first accounted for by changes in behavior, followed by changes in self-efficacy and in commitment to abstinence. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
20.
There is wide interpatient variability in toxicity to chemotherapeutic drugs and a lack of routine clinical tests for prospectively identifying patients at risk of developing toxicity from chemotherapy. An empirically driven MS strategy has been developed to monitor liver-derived plasma proteins as potential biomarkers of early toxicity. Multiple reaction monitoring (MRM) has been used to assess 46 candidate peptides from 18 liver-derived proteins. Following an iterative process of assay design, optimisation and assessment we selected 29 MRM assays (median CV 4.6%, range 1.2-11.6%) and monitored changes in levels of plasma proteins from a small number of colorectal cancer (CRC) patients undergoing chemotherapy. We demonstrated MRM assay robustness, and show that patients undergo minor elevation in plasma proteins when profiled on Day 3 of the chemotherapeutic regime. The MRM assays were in general agreement with 2-D DIGE-based quantitation from the same patient samples. The data supports the application of MRM-based methods as facile, highly reproducible, medium-throughput techniques that warrant expanded investigation for clinical utility in identifying patients at risk of developing chemotoxicity.  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