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   396篇
  免费   2篇
  国内免费   2篇
电工技术   3篇
化学工业   70篇
金属工艺   3篇
机械仪表   6篇
建筑科学   41篇
能源动力   4篇
轻工业   32篇
水利工程   4篇
石油天然气   1篇
无线电   37篇
一般工业技术   46篇
冶金工业   130篇
自动化技术   23篇
  2020年   4篇
  2018年   5篇
  2017年   6篇
  2016年   10篇
  2015年   4篇
  2014年   8篇
  2013年   31篇
  2012年   7篇
  2011年   9篇
  2010年   4篇
  2009年   5篇
  2008年   16篇
  2007年   17篇
  2006年   10篇
  2005年   11篇
  2004年   11篇
  2003年   6篇
  2002年   13篇
  2001年   9篇
  2000年   7篇
  1999年   8篇
  1998年   21篇
  1997年   20篇
  1996年   12篇
  1995年   13篇
  1994年   9篇
  1993年   14篇
  1992年   6篇
  1991年   7篇
  1990年   6篇
  1989年   9篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   6篇
  1984年   3篇
  1979年   2篇
  1978年   2篇
  1977年   8篇
  1976年   9篇
  1975年   2篇
  1973年   2篇
  1947年   3篇
  1946年   4篇
  1945年   4篇
  1944年   4篇
  1943年   2篇
  1942年   2篇
  1941年   2篇
  1940年   2篇
排序方式: 共有400条查询结果,搜索用时 15 毫秒
1.
Based on an idea introduced by Benjamin and Cornell (1970. Probability, statistics and decision for civil engineers. New York: McGaw Hill) and previous works by the authors it is demonstrated how condition indicators may be formulated for the general purpose of quality control and for assessment and inspection planning in particular. The formulation facilitates quality control based on sampling of indirect information about the condition of the considered components. This allows for a Bayesian formulation of the indicators whereby the experience and expertise of the inspection personnel may be fully utilized and consistently updated as frequentistic information is collected. The approach is illustrated on an example considering a concrete structure subject to corrosion. It is shown how half-cell potential measurements may be utilized to update the probability of excessive repair after 50 years. Furthermore in the same example it is shown how the concept of condition indicators might be applied to develop a cost optimal maintenance strategy composed of preventive and corrective repair measures.  相似文献   
2.
Few studies have prospectively examined the characteristics associated with worksite adoption of tobacco-control initiatives. Data were collected as part of the Community Intervention Trial (COMMIT) for Smoking Cessation, which conducted interventions in 11 communities. This smoking cessation intervention was based on community organization principles and delivered through multiple community channels, including worksites, health care providers, the media, and cessation resources. This article reports results from telephone interviews of intervention community worksites having 50 or more employees, conducted at baseline and the end of the intervention period. Among worksites that responded to both baseline and final surveys, 83% had not adopted a smoke-free policy at baseline, and 61% did not offer any cessation aid or quitting resources at baseline. By the final survey, 34% of those with no smoking ban at baseline had become smoke-free, and 36% of those offering no cessation assistance at baseline were offering cessation resources at the follow-up. The prevalence of policy adoption was higher among worksites employing more female employees and offering other health-promotion activities; manufacturing businesses were significantly less likely than businesses other than service and wholesale/retail businesses to adopt policies. Adoption of cessation programs was significantly more likely among worksites employing 100 to 249 workers, compared with those employing 50 to 99 workers; those predominantly employing men; those offering other types of health-promotion activities; and those with a higher rate of turnover. These results provide important information about the characteristics of worksites likely to engage in tobacco-control efforts. Health educators and others may choose to target those worksites most ready for adoption of tobacco control policies and programs, as indicated by these findings.  相似文献   
3.
Treatment of the addictions is changing. Psychosocial treatment programs and research projects have changed the way helping professionals view, treat, and prevent drug abuse. This article reviews the contributions included in this special series; they encompass several general issues facing psychologists who conduct treatment, research, and teaching in the field of addictive behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
5.
Drug users are particularly at risk for contracting the human immunodeficiency virus and serve as a major mechanism for spreading the virus to other sectors of the population. As a result drug abuse treatment and potential behavioral change strategies are primary public health issues. The purpose of this article is to review the contributions included in this special edition, which represent an effort to describe the most current thinking in the field with a blend of theoretical, review, and empirical articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
8.
Violet and purple bacterial pigmentations are uncommon when considering strict aerobes. Here we report discovery of two novel isolates, P102 and P117 from the freshwater Lake Winnipeg, each with violet to deep purple colony colouration. The relationship between pigment production and growth was investigated under different conditions, including a variety of carbon sources, pH, and temperatures. The violet compounds were purified using polar organic solvents, and then structurally characterized via mass spectrometry and nuclear magnetic resonance to be violacein and deoxyviolacein. Strain P117 produced higher concentrations of the darker pigment deoxyviolacein, which resulted in a deeper hue of violet than in cultures of P102. Strain P102, synthesized violacein maximally in liquid rich organic medium at pH 8 and 20 °C, and had 99.3% sequence similarity to the 16S rDNA from Janthinobacterium lividum. Strain P117, related to Massilia violaceinigra sharing 99.2% 16S rDNA sequence similarity, also produced violacein at similar optimal conditions, but developed higher concentrations of pigment at 15 °C. Culture-based methods found that violacein producers composed 0.001% or 0.023% CFU of environmental heterotrophic populations using BG-11 and potato-based media, respectively. Culture-independent high-throughput ribosomal 16S V4 sequencing of environmental DNA was used to detect Gram-negative species known for their production of violacein. Of all bacterial and archaeal sequences present during the fall in littoral waters and sediment of Lake Winnipeg, 5.5% and 6.3%, respectively, belonged to species that have similar pigment, demonstrating the scarcity of violacein producers in this aquatic freshwater system.  相似文献   
9.
10.
Shear viscosity measurements of a mixture of 3-methylpentane and nitroethane at the critical concentration are presented in the temperature range 0.005 KT–T c13.93 K, where T c is the consolute or critical temperature. The data agree with earlier measurements.  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